Can we beneficially reuse produced water from oil and gas extraction in the U.S.?

Oil and gas produced water for cattle, crops, and surface water discharge: Evaluation of chemistry, toxicity and economics

Oil and gas produced water (PW), may help alleviate regional water scarcity affecting agriculture, but is often rich in salts and organic compounds that constrain agricultural applications. The specific objective is to assess the reuse potential of conventional PW through a comprehensive assessment of chemistry, toxicity, and economics by investigating PW from 18 conventionally drilled wells from sandstone formations in the Colorado Denver-Julesburg Basin. Ammonium, total dissolved solids, boron, sodium, and chloride were all close to recommended guidelines for livestock and crop irrigation and surface water discharge. Diesel and gasoline range organics and polycyclic aromatic hydrocarbons were detected in low concentrations in evaporation ponds compared to oil water separators, suggesting volatilization or degradation of organic compounds. Radium levels were generally low, but select samples exceeded the regulatory 5 pCi/g threshold, categorizing them as Non-Exempt TENORM (Technologically Enhanced Naturally Occurring Radioactive Material) waste. EC50 with Daphnia magna (D. magna) showed little to no toxicity for PW sampled in evaporation ponds in contrast to EC50 values of 12 % at the oil water separator, indicating that volatile organics controlled toxicity. However, the Aryl Hydrocarbon Receptor (AhR) bioassay illustrated toxicity not captured by the EC50 test. After chemical and toxicological analyses, it is clear that treatment is required, which informed our techno-economic assessment (TEA). Current PW volumes result in a treatment cost of $5.38/m3 ($1.42/barrel) by nanofiltration, but a scenario with increased volumes will result in a lower cost of $3.83/m³ ($0.60/barrel). Our chemical, toxicological, and economic assessment indicates that the PW in this study has potential to be discharged to surface water or reused for cattle and crop irrigation.

Current status, potential assessment, and future directions of biological treatments of unconventional oil and gas wastewater

Unconventional oil and gas (UOG) extraction techniques typically involve the production of large volumes of so-called flowback and produced water (FPW), a site-specific wastewater stream characterized by complex organic and inorganic composition. Sustainable and cost-effective management of FPW, as well as mitigation of its environmental risks and impacts, represents substantial challenges for governments, industries, and societies worldwide. Among various treatment technologies, biological processes have gained interest due to their low installation and operational costs. However, the interaction of FPW's complex composition with microorganisms poses challenging scientific and engineering questions. This review examines the water quality characteristics and sources of FPW from twelve UOG extraction sites in China and North America, revealing strong spatio-temporal heterogeneity of organic, inorganic, and microbial components across different reservoirs. The complex and variable water quality, large wastewater volumes, and high treatment demands have driven the exploration of biological treatments for FPW. This work systematically reviews and analyzes the operating conditions, treatment efficiency, and technical applicability of suspended sludge reactors, attached sludge reactors, mixed systems, and resource/energy recovery systems. Developing skid-mounted equipment based on suspended sludge reactors to handle variations in wastewater quantity and innovating the form of attached sludge reactors, especially in enriching salt-tolerant microbes for in-situ FPW treatment, are deemed essential. The dominant microorganisms playing a key role in the biological treatment are also discussed, with focus on two different inoculation sources (activated sludge and FPW). Roseovarius from FPW and Pseudomonas from activated sludge have strong adaptability to different reactors. The review further underscores the need to integrate biological treatments with complementary technologies. Finally, it advocates for the establishment of robust and scalable biological treatments through research in three main directions: (i) exploring microbial resources in original FPW; (ii) using omics technologies to elucidate microbial function and species interaction; (iii) pre-designing environmental and operational conditions to optimize treatment efficiency.

Pathways for Potential Exposure to Onshore Oil and Gas Wastewater: What We Need to Know to Protect Human Health

Produced water is a chemically complex waste stream generated during oil and gas development. Roughly four trillion liters were generated onshore in the United States in 2021 (ALL Consulting, 2022, https://www.gwpc.org/wp-content/uploads/2021/09/2021_Produced_Water_Volumes.pdf). Efforts are underway to expand historic uses of produced water to offset freshwater needs in water-stressed regions, avoid induced seismic activity associated with its disposal, and extract commodities. Understanding the potential exposures from current and proposed produced water uses and management practices can help to inform health-protective practices. This review summarizes what is known about potential human exposure to produced water from onshore oil and gas development in the United States. We synthesize 236 publications to create a conceptual model of potential human exposure that illustrates the current state of scientific inquiry and knowledge. Exposure to produced water can occur following its release to the environment through spills or leaks during its handling and management. Exposure can also arise from authorized releases, including permitted discharges to surface water, crop irrigation, and road treatment. Knowledge gaps include understanding the variable composition and toxicity of produced water released to the environment, the performance of treatment methods, migration pathways through the environment that can result in human exposure, and the significance of the exposures for human and ecosystem health. Reducing these uncertainties may help in realizing the benefits of produced water use while simultaneously protecting human health.

Geochemical fingerprinting and statistical variation of 35 elements in produced water and rock material from offshore chalk reservoirs

Trace metals and metalloids occur in small quantities in the subsurface water generated from oil wells, called produced water (PW). While these substances are present in low concentrations, PW volumes are sufficiently large that they are still a potential environmental concern. This study has focused on quantifying 71 trace metals and metalloids present in PW from Danish offshore oil production sites. These metals are often a challenge to measure and are globally underreported. By employing optimized sample treatment combined with ICP-OES and ICP-SFMS methods, the full elemental screening of PW samples collected from various offshore platforms has been carried out with high accuracy. Distinct geochemical signatures involving 35 elements have been discovered and they are associated with significant site-specific variations in the concentrations of key trace metals, including W, Ba, Mo, Cu, and Tl. Utilizing Principal Component Analysis (PCA), the study has effectively distinguished between PW samples from different fields, highlighting the relevance of certain trace metals and elemental ratios as potential geochemical markers. Geochemical analysis of the chalk rock material from the same production wells as the fluid samples has shown a correlation of key elements Tl, W, Cu, Mo, Ba, and As in the chalk with the produced water, potentially indicating the origin of the metals. The study has revealed a high compositional variability of PW and found that elements including Zn, Co, Hg, and Cs occur in concentrations of magnitude higher than previous estimates from reports. In addition, there is high variability in concentrations at different sampling times, underlining the need for environmental monitoring and developing more informed management strategies for the main offshore PW stream. The variability in concentrations in space and time leads to large uncertainties in environmental reporting based on a few samples. The detailed sampling campaign reported here for the first time highlights the need for much more frequent sampling, ideally continuous monitoring. The safety of produced water discharge to sea can be significantly underestimated by limited sampling. This paper provides the first field-specific and time varied screening of heavy metals in real produced water and shows the discrepancy in our understanding of the environmental impact of PW.

Produced water geochemistry from hydraulically stimulated Niobrara Formation petroleum wells: Origin of salinity and temporal perspectives on treatment and reuse

Produced water (i.e., a mixture of returned injection fluids and geologic formation brines) represents the largest volumetric waste stream associated with petroleum production in the United States. As such, produced water has been the focus of intense study with emphasis on understanding the geologic origin of the fluids, environmental impacts of unintended or intentional release, disposal concerns, and their commodity (e.g., lithium) potential. However, produced water geochemistry from many active petroleum plays remain poorly understood leading to knowledge gaps associated with the origin of brine salinity and parameters (e.g., radium levels) that can impact treatment, disposal, and possible reuse. Here we evaluate the major ion geochemistry, radium concentrations, and stable water isotope composition of ~120 produced water samples collected from 17 producing unconventional petroleum wells in Weld County, Colorado from the Late Cretaceous Niobrara Formation. This sample set encompasses eight produced water time series from four new wells across production days 0 to ~365 and from four established wells across production days ~1000 to ~1700. Additionally, produced water from nine other established Niobrara Formation wells were sampled at discrete time points ranging from day 458 to day 2256, as well as hydraulic fracturing input fluids. These results expand the available Niobrara Formation produced water geochemical data, previously limited to a few wells sampled within the first year of production, allowing for the heterogeneity of major ions and radium to be evaluated. Specific highlights include: (i) observations that boron and bromide concentrations are higher in produced waters from new wells compared to older, established wells, suggesting the role of input fluids contributing to fluid geochemistry; and (ii) barium and radium concentrations vary between the producing benches of the Niobrara Formation with implications for treating radiological hazards in produced waters from this formation. Furthermore, we explore the geochemical relationships between major ion ratios and stable water isotope composition to understand the origin of salinity in Niobrara Formation brines from the Denver-Julesburg Basin. These findings are discussed with perspective toward potential treatment and reuse of Niobrara produced water prior to disposal.

Wastewaters Coproduced with Shale Gas Drive Slight Regional Salinization of Groundwater

While unconventional oil and gas (UOG) development is changing the world economy, processes that are used during UOG development such as high-volume hydraulic fracturing ("fracking") have been linked with water contamination. Water quality risks include leaks of gas and salty fluids (brines) that are coproduced at wellpads. Identifying the cause of contamination is difficult, however, because UOG wells are often colocated with other contaminant sources. We investigated the world's largest shale gas play with publicly accessible groundwater data (Marcellus Shale in Pennsylvania, U.S.A. with ∼29,000 analyses) and discovered that concentrations of brine-associated barium ([Ba]) and strontium ([Sr]) show small regional increases within 1 km of UOG development. Higher concentrations in groundwaters are associated with greater proximity to and density of UOG wells. Concentration increases are even larger when considering associations with the locations of (i) spill-related violations and (ii) some wastewater impoundments. These statistically significant relationships persist even after correcting for other natural and anthropogenic sources of salts. The most likely explanation is that UOG development slightly increases salt concentrations in regional groundwaters not because of fracking but because of the ubiquity of wastewater management issues. These results emphasize the need for stringent wastewater management practices across oil and gas operations.

Benchmarking produced water treatment strategies for non-toxic effluents: Integrating thermal distillation with granular activated carbon and zeolite post-treatment

The management of produced water (PW) generated during oil and gas operations requires effective treatment and comprehensive chemical and toxicological assessment to reduce the environmental risks associated with reuse or discharge. This study evaluated a treatment train that included a low-temperature thermal distillation pilot system followed by granular activated carbon (GAC) and zeolite post-treatment for processing hypersaline Permian Basin PW. Our study provides a unique and comprehensive assessment of the treatment efficiency considering a targeted chemical scheme together with whole effluent toxicity (WET) tests across four trophic levels regarding aquatic critical receptors of concern (ROC): Raphidocelis subcapitata, Vibrio fischeri, Ceriodaphnia dubia, and Danio rerio. The distillate from the thermal distillation process met various numeric discharge standards for salinity and major ions. However, it did not meet toxicity requirements established by the United States National Pollutant Discharge Elimination System program. Subsequent post-treatment using GAC and zeolite reduced the concentration of potential stressors, including volatile organics, NH3, Cd, Cr, Zn, and Mn in the final effluent to below detection limits. This resulted in a consistent toxicity reduction across all WET tests, with no observable adverse effects for R. subcapitata, C. dubia, and D. rerio (no observed effect concentration >100%), and V. fischeri effects reduced to 19%. This study realizes the feasibility of treating PW to non-toxic levels and meeting reuse and discharge requirements. It underscores the importance of implementing integrated treatment trains to remove the contaminants of concern and provides a systematic decision framework to predict and monitor environmental risks associated with PW reuse.

Utica/Point Pleasant brine isotopic compositions (δ7Li, δ11B, δ138Ba) elucidate mechanisms of lithium enrichment in the Appalachian Basin

Global Li production will require a ∼500 % increase to meet 2050 projected energy storage demands. One potential source is oil and gas wastewater (i.e., produced water or brine), which naturally has high total dissolved solids (TDS) concentrations, that can also be enriched in Li (>100 mg/L). Understanding the sources and mechanisms responsible for high naturally-occurring Li concentrations can aid in efficient targeting of these brines. The isotopic composition (δ7Li, δ11B, δ138Ba) of produced water and core samples from the Utica Shale and Point Pleasant Formation (UPP) in the Appalachian Basin, USA indicates that depth-dependent thermal maturity and water-rock interaction, including diagenetic clay mineral transformations, likely control Li concentrations. A survey of Li content in produced waters throughout the USA indicates that Appalachian Basin brines from the Marcellus Shale to the UPP have the potential for economic resource recovery.

Critical mineral source potential from oil & gas produced waters in the United States

The volume of produced water, a by-product of oil & gas operations and other energy processes, has been growing across the United States (U.S.) along with the need to manage or recycle this wastewater. Produced water contains many naturally occurring elements of varying concentrations, including critical minerals which are essential to the clean energy transition. However, the current understanding of critical mineral concentrations in produced water and the associated volumes across the U.S. is limited. This study has assessed available databases and literature to gain insight into the presence and concentration of five high priority critical minerals, namely cobalt, lithium, magnesium, manganese, and nickel. The U.S. Geological Survey's National Produced Waters Geochemical Database was the main data source used for determining average critical mineral concentrations in produced water from the major oil and gas reservoirs in the U.S. The volumes of produced water for these major reservoirs were coupled with these concentrations to provide insights into where critical minerals are likely to have high abundance and therefore more recovery options. The analysis indicated the highest recovery potential for lithium and magnesium from produced water in the Permian basin and the Marcellus shale region. However, these assessments should be considered conservative due to the limited availability of reliable concentration data. It is expected more critical mineral recovery options could emerge with comprehensive characterization data from more recent and representative sources of produced water.

Non-targeted analysis and toxicity prediction for evaluation of photocatalytic membrane distillation removing organic contaminants from hypersaline oil and gas field-produced water

Membrane distillation (MD) has received ample recognition for treating complex wastewater, including hypersaline oil and gas (O&G) produced water (PW). Rigorous water quality assessment is critical in evaluating PW treatment because PW consists of numerous contaminants beyond the targets listed in general discharge and reuse standards. This study evaluated a novel photocatalytic membrane distillation (PMD) process, with and without a UV light source, against a standard vacuum membrane distillation (VMD) process for treating PW, utilizing targeted analyses and a non-targeted chemical identification workflow coupled with toxicity predictions. PMD with UV light resulted in better removals of dissolved organic carbon, ammoniacal nitrogen, and conductivity. Targeted organic analyses identified only trace amounts of acetone and 2-butanone in distillates. According to non-targeted analysis, the number of suspects reduced from 65 in feed to 25-30 across all distillate samples. Certain physicochemical properties of compounds influenced contaminant rejection in different MD configurations. According to preliminary toxicity predictions, VMD, PMD with and without UV distillate samples, respectively contained 21, 22, and 23 suspects associated with critical toxicity concerns. Overall, non-targeted analysis together with toxicity prediction provides a competent supportive tool to assess treatment efficiency and potential impacts on public health and the environment during PW reuse.

Estimates of lithium mass yields from produced water sourced from the Devonian-aged Marcellus Shale

Decarbonatization initiatives have rapidly increased the demand for lithium. This study uses public waste compliance reports and Monte Carlo approaches to estimate total lithium mass yields from produced water (PW) sourced from the Marcellus Shale in Pennsylvania (PA). Statewide, Marcellus Shale PW has substantial extractable lithium, however, concentrations, production volumes and extraction efficiencies vary between the northeast and southwest operating zones. Annual estimates suggest statewide lithium mass yields of approximately 1160 (95% CI 1140-1180) metric tons (mt) per year. Production decline curve analysis on PW volumes reveal cumulative volumetric disparities between the northeast (median = 2.89 X 107 L/10-year) and southwest (median = 5.56 × 107 L/10-year) regions of the state, influencing lithium yield estimates of individual wells in southwest [2.90 (95% CI 2.80-2.99) mt/10-year] and northeast [1.96 (CI 1.86-2.07) mt/10-year] PA. Moreover, Mg/Li mass ratios vary regionally, where NE PA are low Mg/Li fluids, having a median Mg/Li mass ratio of 5.39 (IQR, 2.66-7.26) and SW PA PW is higher with a median Mg/Li mass ratio of 17.8 (IQR, 14.3-20.7). These estimates indicate substantial lithium yields from Marcellus PW, though regional variability in chemistry and production may impact recovery efficiencies.

Integrative analysis of the transcriptome and metabolome reveals Bacillus atrophaeus WZYH01-mediated salt stress mechanism in maize (Zea mays L.)

Maize is an important food crop that is affected by salt stress during growth, which can hinder plant growth and result in a significant decrease in yield. The application of plant growth-promoting rhizobacteria can improve this situation to a certain extent. However, the gene network of rhizosphere-promoting bacteria regulating the response of maize to salt stress remains elusive. Here, we used metabolomics and transcriptomics techniques to elucidate potential gene networks and salt-response pathways in maize. Phenotypic analysis showed that the Bacillus atrophaeus treatment improved the plant height, leaf area, biomass, ion, nutrient and stomatal indicators of maize. Metabolomic analysis identified that differentially expressed metabolites (DEMs) were primarily concentrated in the arginine, proline and phytohormone signaling metabolic pathways. 4-Hydroxyphenylacetylglutamic acid, L-histidinol, oxoglutaric acid, L-glutamic acid, L-arginine, and L-tyrosine were significantly increased in the Bacillus atrophaeus treatment. Weighted gene coexpression network analysis (WGCNA) identified several hub genes associated with salt response: Zm00001eb155540 and Zm00001eb088790 (ABC transporter family), Zm00001eb419060 (extra-large GTP-binding protein family), Zm00001eb317200 (calcium-transporting ATPase), Zm00001eb384800 (aquaporin NIP1-4) and Zm00001eb339170 (cytochrome P450). Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that genes related to plant hormone signal transduction and the MAPK signaling pathway were involved in the response to the effect of Bacillus atrophaeus under salt stress. In the plant hormone signal transduction pathway, 3 differentially expressed genes (DEGs) encoding EIN3/EILs protein, 3 DEGs encoding GH3, 1 DEG encoding PYR/PYL and 6 DEGs encoding PP2C were all upregulated in Bacillus atrophaeus treatment. In the MAPK signaling pathway, 2 DEGs encoding CAT1 and 2 DEGs encoding WRKY22/WRKY29 were significantly upregulated, and the expression of DEGs encoding RbohD was downregulated by the application of Bacillus atrophaeus. In conclusion, the application of Bacillus atrophaeus under salt stress regulated key physiological and molecular processes in plants, which could stimulate the expression of genes related to ion transport and nutrients in maize, alleviate salt stress and promote maize growth to some extent, deepening our understanding of the application of Bacillus atrophaeus under salt stress to improve the salt-response gene network of maize growth.

Illegal dumping of oil and gas wastewater alters arid soil microbial communities

The Permian Basin, underlying southeast New Mexico and west Texas, is one of the most productive oil and gas (OG) provinces in the United States. Oil and gas production yields large volumes of wastewater with complex chemistries, and the environmental health risks posed by these OG wastewaters on sensitive desert ecosystems are poorly understood. Starting in November 2017, 39 illegal dumps, as defined by federal and state regulations, of OG wastewater were identified in southeastern New Mexico, releasing ~600,000 L of fluid onto dryland soils. To evaluate the impacts of these releases, we analyzed changes in soil geochemistry and microbial community composition by comparing soils from within OG wastewater dump-affected samples to unaffected zones. We observed significant changes in soil geochemistry for all dump-affected compared with control samples, reflecting the residual salts and hydrocarbons from the OG-wastewater release (e.g., enriched in sodium, chloride, and bromide). Microbial community structure significantly (P < 0.01) differed between dump and control zones, with soils from dump areas having significantly (P < 0.01) lower alpha diversity and differences in phylogenetic composition. Dump-affected soil samples showed an increase in halophilic and halotolerant taxa, including members of the Marinobacteraceae, Halomonadaceae, and Halobacteroidaceae, suggesting that the high salinity of the dumped OG wastewater was exerting a strong selective pressure on microbial community structure. Taxa with high similarity to known hydrocarbon-degrading organisms were also detected in the dump-affected soil samples. Overall, this study demonstrates the potential for OG wastewater exposure to change the geochemistry and microbial community dynamics of arid soils.IMPORTANCEThe long-term environmental health impacts resulting from releases of oil and gas (OG) wastewater, typically brines with varying compositions of ions, hydrocarbons, and other constituents, are understudied. This is especially true for sensitive desert ecosystems, where soil microbes are key primary producers and drivers of nutrient cycling. We found that releases of OG wastewater can lead to shifts in microbial community composition and function toward salt- and hydrocarbon-tolerant taxa that are not typically found in desert soils, thus altering the impacted dryland soil ecosystem. Loss of key microbial taxa, such as those that catalyze organic carbon cycling, increase arid soil fertility, promote plant health, and affect soil moisture retention, could result in cascading effects across the sensitive desert ecosystem. By characterizing environmental changes due to releases of OG wastewater to soils overlying the Permian Basin, we gain further insights into how OG wastewater may alter dryland soil microbial functions and ecosystems.

Treated water from oil and gas extraction as an unconventional water resource for agriculture in the Anadarko Basin

The energy industry generates large volumes of produced water (PW) as a byproduct of oil and gas extraction. In the central United States, PW disposal occurs through deep well injection, which can increase seismic activity. The treatment of PW for use in agriculture is an alternative to current disposal practices that can also provide supplemental water in regions where limited freshwater sources can affect agricultural production. This paper assesses the potential for developing PW as a water source for agriculture in the Anadarko basin, a major oil and gas field spanning parts of Kansas, Oklahoma, Colorado, and Texas. From 2011 to 2019, assessment of state oil and gas databases indicated that PW generation in the Anadarko Basin averaged 428 million m3/yr. A techno-economic analysis of PW treatment was combined with geographical information on PW availability and composition to assess the costs and energy requirements to recover this PW as a non-conventional water resource for agriculture. The volume of freshwater economically extractable from PW was estimated to be between 58 million m3 per year using reverse osmosis (RO) treatment only and 82 million m3 per year using a combination of RO and mechanical vapor compression to treat higher salinity waters. These volumes could meet 1-2 % and 49-70 % of the irrigation and livestock water demands in the basin, respectively. PW recovery could also modestly contribute to mitigating the decline of the Ogallala aquifer by ~2 %. RO treatment costs and energy requirements, 0.3-1.5 $/m3 and 1.01-2.65 kWh/m3, respectively, are similar to those for deep well injection. Treatment of higher salinity waters increases costs and energy requirements substantially and is likely not economically feasible in most cases. The approach presented here provides a valuable framework for assessing PW as a supplemental water source in regions facing similar challenges.

Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Quantitative approaches for including equity in risk and resilience infrastructure planning analyses

Risk and resilience assessments for critical infrastructure focus on myriad objectives, from natural hazard evaluations to optimizing investments. Although research has started to characterize externalities associated with current or possible future states, incorporation of equity priorities at project inception is increasingly being recognized as critical for planning related activities. However, there is no standard methodology that guides development of equity-informed quantitative approaches for infrastructure planning activities. To address this gap, we introduce a logic model that can be tailored to capture nuances about specific geographies and community priorities, effectively incorporating them into different mathematical approaches for quantitative risk assessments. Specifically, the logic model uses a graded, iterative approach to clarify specific equity objectives as well as inform the development of equations being used to support analysis. We demonstrate the utility of this framework using case studies spanning aviation fuel, produced water, and microgrid electricity infrastructures. For each case study, the use of the logic model helps clarify the ways that local priorities and infrastructure needs are used to drive the types of data and quantitative methodologies used in the respective analyses. The explicit consideration of methodological limitations (e.g., data mismatches) and stakeholder engagements serves to increase the transparency of the associated findings as well as effectively integrate community nuances (e.g., ownership of assets) into infrastructure assessments. Such integration will become increasingly important to ensure that planning activities (which occur throughout the lifecycle of the infrastructure projects) lead to long-lasting solutions to meet both energy and sustainable development goals for communities.

A review of the development in shale oil and gas wastewater desalination

The development of the shale oil and gas extraction industry has heightened concerns about shale oil and gas wastewater (SOGW). This review comprehensively summarizes, analyzes, and evaluates multiple issues in SOGW desalination. The detailed analysis of SOGW water quality and various disposal strategies with different water quality standards reveals the water quality characteristics and disposal status of SOGW, clarifying the necessity of desalination for the rational management of SOGW. Subsequently, potential and implemented technologies for SOGW desalination are reviewed, mainly including membrane-based, thermal-based, and adsorption-based desalination technologies, as well as bioelectrochemical desalination systems, and the research progress of these technologies in desalinating SOGW are highlighted. In addition, various pretreatment methods for SOGW desalination are comprehensively reviewed, and the synergistic effects on SOGW desalination that can be achieved by combining different desalination technologies are summarized. Renewable energy sources and waste heat are also discussed, which can be used to replace traditional fossil energy to drive SOGW desalination and reduce the negative impact of shale oil and gas exploitation on the environment. Moreover, real project cases for SOGW desalination are presented, and the full-scale or pilot-scale on-site treatment devices for SOGW desalination are summarized. In order to compare different desalination processes clearly, operational parameters and performance data of varying desalination processes, including feed salinity, water flux, salt removal rate, water recovery, energy consumption, and cost, are collected and analyzed, and the applicability of different desalination technologies in desalinating SOGW is qualitatively evaluated. Finally, the recovery of valuable inorganic resources in SOGW is discussed, which is a meaningful research direction for SOGW desalination. At present, the development of SOGW desalination has not reached a satisfactory level, and investing enough energy in SOGW desalination in the future is still necessary to achieve the optimal management of SOGW.

Hydrochemistry, Sources and Management of Fracturing Flowback Fluid in Tight Sandstone Gasfield in Sulige Gasfield (China)

Hydraulic fracturing technologies have been frequently utilized in the oil and gas industry as exploration and development efforts have progressed, resulting in a significant increase in the extraction of natural gas and petroleum from low-permeability reservoirs. However, hydraulic fracturing requires a large amount of freshwater, and the process results in the production of large volumes of flowback water along with natural gas. In this study, three tight sandstone gas wells were fractured in the Sulige gasfield (China), and a total of 103 flowback fluid samples were collected. The hydrochemical characteristics, water quality and sources of hydrochemical components in the flowback fluid were discussed. The results show that the flowback fluid is characterized by high salinity (Total dissolved solids (TDS) up to 38,268 mg/L, Cl^- up to 24,000 mg/L), high concentrations of metal ions (e.g., Fe, Sr²⁺, Ba²⁺) and high chemical oxygen demand (COD). The flowback fluid is a complex mixture of fracturing fluid and formation water, and its composition is impacted by water-rock interactions that occur during hydraulic fracturing. The major contaminants include COD, Fe, Ba²⁺, Cl^-, Mn and pH, which constitute a high risk of environmental pollution. Meanwhile, chemical elements such as K, Ba and Sr are unusually enriched in the flowback fluid, which has an excellent potential for recycle of chemical elements. The Sulige gasfield's flowback fluid recovery methods and treatment scenarios were discussed, taking into consideration the pollution and resource characteristics of the flowback fluid. Options for dealing with the flowback fluid include deep well reinjection, reuse for making up fracturing fluid, recycling of chemical elements and diverse reuse of flowback water. This research offers guidance for managing the fracturing flowback fluid in unconventional oil and gas fields.

Design Strategies for Forward Osmosis Membrane Substrates with Low Structural Parameters-A Review

This article reviews the many innovative strategies that have been developed to specifically design the support layers of forward osmosis (FO) membranes. Forward osmosis (FO) is one of the most viable separation technologies to treat hypersaline wastewater, but its successful deployment requires the development of new membrane materials beyond existing desalination membranes. Specifically, designing the FO membrane support layers requires new engineering techniques to minimize the internal concentration polarization (ICP) effects encountered in cases of FO. In this paper, we have reviewed several such techniques developed by different research groups and summarized the membrane transport properties corresponding to each approach. An important transport parameter that helps to compare the various approaches is the so-called structural parameter (S-value); a low S-value typically corresponds to low ICP. Strategies such as electrospinning, solvent casting, and hollow fiber spinning, have been developed by prior researchers-all of them aimed at lowering this S-value. We also reviewed the quantitative methods described in the literature, to evaluate the separation properties of FO membranes. Lastly, we have highlighted some key research gaps, and provided suggestions for potential strategies that researchers could adopt to enable easy comparison of FO membranes.

Geochemistry and Multiomics Data Differentiate Streams in Pennsylvania Based on Unconventional Oil and Gas Activity

Unconventional oil and gas (UOG) extraction is increasing exponentially around the world, as new technological advances have provided cost-effective methods to extract hard-to-reach hydrocarbons. While UOG has increased the energy output of some countries, past research indicates potential impacts in nearby stream ecosystems as measured by geochemical and microbial markers. Here, we utilized a robust data set that combines 16S rRNA gene amplicon sequencing (DNA), metatranscriptomics (RNA), geochemistry, and trace element analyses to establish the impact of UOG activity in 21 sites in northern Pennsylvania. These data were also used to design predictive machine learning models to determine the UOG impact on streams. We identified multiple biomarkers of UOG activity and contributors of antimicrobial resistance within the order Burkholderiales. Furthermore, we identified expressed antimicrobial resistance genes, land coverage, geochemistry, and specific microbes as strong predictors of UOG status. Of the predictive models constructed (n = 30), 15 had accuracies higher than expected by chance and area under the curve values above 0.70. The supervised random forest models with the highest accuracy were constructed with 16S rRNA gene profiles, metatranscriptomics active microbial composition, metatranscriptomics active antimicrobial resistance genes, land coverage, and geochemistry (n = 23). The models identified the most important features within those data sets for classifying UOG status. These findings identified specific shifts in gene presence and expression, as well as geochemical measures, that can be used to build robust models to identify impacts of UOG development. IMPORTANCE The environmental implications of unconventional oil and gas extraction are only recently starting to be systematically recorded. Our research shows the utility of microbial communities paired with geochemical markers to build strong predictive random forest models of unconventional oil and gas activity and the identification of key biomarkers. Microbial communities, their transcribed genes, and key biomarkers can be used as sentinels of environmental changes. Slight changes in microbial function and composition can be detected before chemical markers of contamination. Potential contamination, specifically from biocides, is especially concerning due to its potential to promote antibiotic resistance in the environment. Additionally, as microbial communities facilitate the bulk of nutrient cycling in the environment, small changes may have long-term repercussions. Supervised random forest models can be used to identify changes in those communities, greatly enhance our understanding of what such impacts entail, and inform environmental management decisions.

Textured ceramic membranes for desilting and deoiling of produced water in the Permian Basin

Oil production in the Permian Basin gives rise to large volumes of produced water contaminated by silt, emulsified oil, and additives used for enhanced oil recovery. There is intense interest in the design of membrane modules as sustainable alternatives for produced water treatment to enable the reuse of produced water for agricultural applications, injection into aquifers, and redeployment in oil recovery. Here, we report a hierarchically textured cement-based membrane exhibiting orthogonal wettability, specifically, superhydrophilic and underwater superoleophobic characteristics. The in situ formation of ettringite needles accompanied by embedding of glass spheres imbues multiscale texturation to stainless-steel mesh membranes, enabling the separation of silt and oil from produced water at high flux rates (1600 L h⁻¹۰m⁻², at ca. 2.7 bar). Oil concentration is reduced as low as 1 ppb with an overall separation efficiency of 99.7% in single-pass filtration. The membranes show outstanding mechanical resilience and retention of performance across multiple cycles.

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Multiscale 3D texturation of a metal mesh membrane engenders orthogonal wettability

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High separation efficiency of ca. 99% was achieved for produced water

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Oil concentration reduced to ≤1 ppb in a single pass at a high flux rate

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Desiliting and deoiling demonstrated for real produced water streams

The water footprint of hydraulic fracturing under different hydroclimate conditions in the Central and Western United States

The oil and gas (O&G) exploitation via hydraulic fracturing (HF) has augmented both energy production and water demand in the United States. Despite the geographical coincidence of U.S. shale plays with water-scarce areas, the water footprint of HF under drought conditions, as well as its impacts on local water allocation, have not been well understood. In this study, we investigated the water consumption by HF activities under different hydroclimate conditions in eleven O&G-producing states in the central and western U.S. from 2011 to 2020. Our results show that the water consumption under abnormally dry or drought climates accounted for 49.7 % (475.3 billion gallons or 1.8 billion m³) of total water usage of HF, with 9 % (86.1 billion gallons or 325.9 million m³) of water usage occurring under extreme or exceptional drought conditions. The water usage of HF under arid conditions can translate to high densities of water footprint at the local scale, equivalent to >10 % and 50 % of the annual water usage by the irrigation and domestic sectors in 6-29 irrigation-active counties and 11-51 counties (depending on the specific year), respectively. Such water stress imposed by O&G production, however, can be effectively mitigated by the reuse of flowback and produced water. Our findings, for the first time, quantify the water footprint of HF as a function of hydroclimate condition, providing evidence that the water consumption by HF intensifies local water competition and alters water supply threatened by climate variability. This renders wastewater reuse necessary to maintain water sustainability of O&G-producing regions in the context of both a rising O&G industry and a changing climate.

Dissolved organic matter within oil and gas associated wastewaters from U.S. unconventional petroleum plays: Comparisons and consequences for disposal and reuse

Wastewater generated during petroleum extraction (produced water) may contain high concentrations of dissolved organics due to their intimate association with organic-rich source rocks, expelled petroleum, and organic additives to fluids used for hydraulic fracturing of unconventional (e.g., shale) reservoirs. Dissolved organic matter (DOM) within produced water represents a challenge for treatment prior to beneficial reuse. High salinities characteristic of produced water, often 10× greater than seawater, coupled to the complex DOM ensemble create analytical obstacles with typical methods. Excitation-emission matrix spectroscopy (EEMS) can rapidly characterize the fluorescent component of DOM with little impact from matrix effects. We applied EEMS to evaluate DOM composition in 18 produced water samples from six North American unconventional petroleum plays. Represented reservoirs include the Eagle Ford Shale (Gulf Coast Basin), Wolfcamp/Cline Shales (Permian Basin), Marcellus Shale and Utica/Point Pleasant (Appalachian Basin), Niobrara Chalk (Denver-Julesburg Basin), and the Bakken Formation (Williston Basin). Results indicate that the relative chromophoric DOM composition in unconventional produced water may distinguish different lithologies, thermal maturity of resource types (e.g., heavy oil vs. dry gas), and fracturing fluid compositions, but is generally insensitive to salinity and DOM concentration. These results are discussed with perspective toward DOM influence on geochemical processes and the potential for targeted organic compound treatment for the reuse of produced water.

Analysis of Regulatory Framework for Produced Water Management and Reuse in Major Oil- and Gas-Producing Regions in the United States

The rapid development of unconventional oil and gas (O&G) extraction around the world produces a significant amount of wastewater that requires appropriate management and disposal. Produced water (PW) is primarily disposed of through saltwater disposal wells, and other reuse/disposal methods include using PW for hydraulic fracturing, enhanced oil recovery, well drilling, evaporation ponds or seepage pits within the O&G field, and transferring PW offsite for management or reuse. Currently, 1–2% of PW in the U.S. is used outside the O&G field after treatment. With the considerable interest in PW reuse to reduce environmental implications and alleviate regional water scarcity, it is imperative to analyze the current regulatory framework for PW management and reuse. In the U.S., PW is subject to a complex set of federal, state, and sometimes local regulations to address the wide range of PW management, construction, and operation practices. Under the supervision of the U.S. Environment Protection Agency (U.S. EPA), different states have their own regulatory agencies and requirements based on state-specific practices and laws. This study analyzed the regulatory framework in major O&G-producing regions surrounding the management of PW, including relevant laws and jurisdictional illustrations of water rules and responsibilities, water quality standards, and PW disposal and current/potential beneficial reuse up to early 2022. The selected eastern states (based on the 98th meridian designated by the U.S. EPA as a tool to separate discharge permitting) include the Appalachian Basin (Marcellus and Utica shale areas of Pennsylvania, Ohio, and West Virginia), Oklahoma, and Texas; and the western states include California, Colorado, New Mexico, and Wyoming. These regions represent different regulations; climates; water quantities; quality diversities; and geologic, geographic, and hydrologic conditions. This review is particularly focused on the water quality standards, reuse practices and scenarios, risks assessment, knowledge gaps, and research needs for the potential reuse of treated PW outside of O&G fields. Given the complexity surrounding PW regulations and rules, this study is intended as preliminary guidance for PW management, and for identifying the knowledge gaps and research needs to reduce the potential impacts of treated PW reuse on the environment and public health. The regulations and experiences learned from these case studies would significantly benefit other states and countries with O&G sources for the protection of their environment and public health.

Produced Water Treatment and Valorization: A Techno-Economical Review

In recent years, environmental concerns have urged companies in the energy sector to modify their industrial activities to facilitate greater environmental stewardship. For example, the practice of unconventional oil and gas extraction has drawn the ire of regulators and various environmental groups due to its reliance on millions of barrels of fresh water—which is generally drawn from natural sources and public water supplies—for hydraulic fracturing well stimulation. Additionally, this process generates two substantial waste streams, which are collectively characterized as flowback and produced water. Whereas flowback water is comprised of various chemical additives that are used during hydraulic fracturing; produced water is a complex mixture of microbiota, inorganic and organic constituents derived from the petroliferous strata. This review will discuss the obstacles of managing and treating flowback and produced waters, concentrating on the hardest constituents to remove by current technologies and their effect on the environment if left untreated. Additionally, this work will address the opportunities associated with repurposing produced water for various applications as an alternative to subsurface injection, which has a number of environmental concerns. This review also uses lithium to evaluate the feasibility of extracting valuable metals from produced water using commercially available technologies.

Characterizing Various Produced Waters from Shale Energy Extraction within the Context of Reuse

Environmental concerns with unconventional oil and gas development are frequently centered on elevated water usage and the induction of seismic events during waste disposal. Reuse of produced water for subsequent production well stimulation can effectively address these concerns, but the variability among such samples must be well understood. Twenty-four samples of wastewater from unconventional oil and gas development were collected from south and west Texas to assess their variability and feasibility for direct reuse. Bulk metrics were collected, including total organic carbon, total nitrogen, as well as total dissolved and suspended solids. The profiles of pertinent inorganic constituents were also evaluated. Variations were not only seen between regions but also among samples collected from the same region. For example, the average total organic carbon for Eagle Ford samples collected was 700 ± 500 mg/L, while samples collected from the Permian Basin featured an average total organic carbon concentration of 600 ± 900 mg/L. The Permian Basin total organic carbon ranged from 38 to 2600 mg/L. The total dissolved solids levels had the same variability between regions, with an average value for Eagle Ford of 20,000 ± 10,000 mg/L and a Permian Basin value of 150,000 ± 40,000 mg/L. However, samples were more reproducible within a given region. Collectively, the data indicate that the direct reuse of raw produced water for subsequent production well development without treatment is not feasible based on the reported reuse thresholds. Unconventional development wastewater samples from the Permian Basin were also compared to produced water values from conventional oil and gas wells in the same region, as reported by the United States Geological Survey. Samples collected in the Permian Basin consistently demonstrated lower ionic strength compared to conventional produced water data.

Spatiotemporal Analysis of Produced Water Demand for Fit-For-Purpose Reuse—A Permian Basin, New Mexico Case Study

This study created a framework for assessing the spatial and temporal distribution of the supply and demand of four potential produced water (PW) reuse options: agriculture, dust suppression, power generation, and river flow augmentation using Eddy and Lea counties in the southeastern New Mexico Permian Basin as a case study. Improving the PW management in the oil and gas industry is important in areas with limited water resources and increasing restrictions on PW disposal. One option in the PW management portfolio is fit-for-purpose reuse, but a lack of adequate information on PW quality, volumes, and the spatiotemporal distribution of PW supply and demand precludes its reuse. Using the framework, we determined that a 1.1-mile grid cell for data aggregation is a sufficient spatial scale for capturing the granular data needed for PW management decisions. The annual available PW supply for the two counties was estimated to be 45,460,875 m3 (36,870 acre-feet). The annual cumulative estimated demand was 647,656,261 m3 (525,064 acre-feet) for the four potential use cases—far exceeding PW supply. The maps generated using the framework illustrated that much of the supply and demand are spatially dispersed. The spatiotemporal analysis framework provides a generic methodology that can be used for PW management in other basins or for assessing alternative waters at the local and regional scales where management occurs.

Characterization of produced water and surrounding surface water in the Permian Basin, the United States

A thorough understanding of produced water (PW) quality is critical to advance the knowledge and tools for effective PW management, treatment, risk assessment, and feasibility for beneficial reuse outside the oil and gas industry. This study provides the first step to better understand PW quality to develop beneficial reuse programs that are protective of human health and the environment. In total, 46 PW samples from unconventional operations in the Permian Basin and ten surface water samples from the Pecos River in New Mexico were collected for quantitative target analyses of more than 300 constituents. Water quality analyses of Pecos River samples could provide context and baseline information for the potential discharge and reuse of treated PW in this area. Temporal PW and river water quality changes were monitored for eight months in 2020. PW samples had total dissolved solids (TDS) concentrations ranging from 100,800-201,500 mg/L. Various mineral salts, metals, oil and grease, volatile and semi-volatile organic compounds, radionuclides, ammonia, hydraulic fracturing additives, and per- and polyfluoroalkyl substances were detected at different concentrations. Chemical characterization of organic compounds found in Pecos River water showed no evidence of PW origin. Isometric log-ratio Na-Cl-Br analysis showed the salinity in the Pecos River samples appeared to be linked to an increase in natural shallow brine inputs. This study outlines baseline analytical information to advance PW research by describing PW and surrounding surface water quality in the Permian Basin that will assist in determining management strategies, treatment methods, potential beneficial reuse applications, and potential environmental impacts specific to intended beneficial use of treated PW.

Application of a Deep Learning Network for Joint Prediction of Associated Fluid Production in Unconventional Hydrocarbon Development

Machine learning (ML) approaches have risen in popularity for use in many oil and gas (O&G) applications. Time series-based predictive forecasting of hydrocarbon production using deep learning ML strategies that can generalize temporal or sequence-based information within data is fast gaining traction. The recent emphasis on hydrocarbon production provides opportunities to explore the use of deep learning ML to other facets of O&G development where dynamic, temporal dependencies exist and that also hold implications to production forecasting. This study proposes a combination of supervised and unsupervised ML approaches as part of a framework for the joint prediction of produced water and natural gas volumes associated with oil production from unconventional reservoirs in a time series fashion. The study focuses on the pay zones within the Spraberry and Wolfcamp Formations of the Midland Basin in the U.S. The joint prediction model is based on a deep neural network architecture leveraging long short-term memory (LSTM) layers. Our model has the capability to both reproduce and forecast produced water and natural gas volumes for wells at monthly resolution and has demonstrated 91 percent joint prediction accuracy to held out testing data with little disparity noted in prediction performance between the training and test datasets. Additionally, model predictions replicate water and gas production profiles to wells in the test dataset, even for circumstances that include irregularities in production trends. We apply the model in tandem with an Arps decline model to generate cumulative first and five-year estimates for oil, gas, and water production outlooks at the well and basin-levels. Production outlook totals are influenced by well completion, decline curve, and spatial and reservoir attributes. These types of model-derived outlooks can aid operators in formulating management or remedial solutions for the volumes of fluids expected from unconventional O&G development.

Assessing cumulative water impacts from shale oil and gas production: Permian Basin case study

Quantifying impacts of unconventional oil and gas production on water resources and aquatic habitats is critical for developing management approaches for mitigation. The study objective was to evaluate impacts of oil and gas production on groundwater and surface water and assess approaches to reduce these impacts using the Permian Basin as a case study. Water demand for hydraulic fracturing (HF) was compared to water supplies. We also examined contamination from surface spills. Results show that water demand for HF peaked in 2019, representing ~35% of water use in non-mining sectors. Most HF water was sourced from aquifers with ~1,100 wells drilled in the Ogallala aquifer in 2019. The State monitoring network did not show regional groundwater depletion but was not sufficiently dense to address local impacts. Groundwater depletion is more critical in the western Delaware Basin within the Permian Basin because groundwater is connected to large flowing springs (e.g. San Solomon Springs) and to the Pecos River which has total dissolved solids ranging from ~3000 to 14,000 mg/L. Most produced water (70-80%) is disposed in shallow geologic units that could result in overpressuring and potential groundwater contamination from leakage through ~70,000 abandoned oil wells, including orphaned wells. While there is little evidence of leakage from abandoned wells, the state monitoring system was not designed to assess leakage from these wells. Oil spill counts totaled ~11,000 in the Permian (2009-2018). Approaches to mitigating adverse impacts on water management include reuse of PW for HF; however, there is an excess of PW in the Delaware Basin. Treatment and reuse in other sectors outside of oil and gas are also possibilities. Data gaps include reporting of water sources for HF, PW quality data required for assessing treatment and reuse, subsurface disposal capacity for accommodating PW, and spills from PW in Texas.

Unraveling the Complex Composition of Produced Water by Specialized Extraction Methodologies

Produced water (PW), a waste byproduct of oil and gas extraction, is a complex mixture containing numerous organic solubles and elemental species; these constituents range from polycyclic aromatic hydrocarbons to naturally occurring radioactive materials. Identification of these compounds is critical in developing reuse and disposal protocols to minimize environmental contamination and health risks. In this study, versatile extraction methodologies were investigated for the untargeted analysis of PW. Thin-film solid-phase microextraction with hydrophilic-lipophilic balance particles was utilized for the extraction of organic solubles from eight PW samples from the Permian Basin and Eagle Ford formation in Texas. Gas chromatography-mass spectrometry analysis found a total of 266 different organic constituents including 1,4-dioxane, atrazine, pyridine, and PAHs. The elemental composition of PW was evaluated using dispersive solid-phase extraction followed by inductively coupled plasma-mass spectrometry, utilizing a new coordinating sorbent, poly(pyrrole-1-carboxylic acid). This confirmed the presence of 29 elements including rare earth elements, as well as hazardous metals such as Cr, Cd, Pb, and U. Utilizing chemometric analysis, both approaches facilitated the discrimination of each PW sample based on their geochemical origin with a prediction accuracy above 90% using partial least-squares-discriminant analysis, paving the way for PW origin tracing in the environment.

Photocatalytic membrane reactors for produced water treatment and reuse: Fundamentals, affecting factors, rational design, and evaluation metrics

Treatment and reuse of produced water (PW), the largest wastewater stream generated during oil and gas production, provides a promising option to address the increasing clean water demands. High-performance treatment technologies are needed to efficiently remove the organic and inorganic contaminants in PW for fit-for-purpose applications. Photocatalytic membrane reactor (PMR) is an emerging green technology for removal of organic pollutants, photoreduction of heavy metals, photo-inactivation of bacteria, and resource recovery. This study critically reviewed the mechanisms of photocatalysis and membrane processes in PMR, factors affecting PMR performance, rational design, and evaluation metrics for PW treatment. Specifically, PW characteristics, photocatalysts properties, membranes applied, and operating conditions are of utmost importance for rational design and reliable operation of PMR. PW pretreatment to remove oil and grease, colloidal and suspended solids is necessary to reduce membrane fouling and ensure optimal PMR performance. The metrics to evaluate PMR performance were developed including light utilization, exergetic efficiency, water recovery, product water improvement, lifetime of the photocatalyst, and costs. This review also presented the research gaps and outlook for future research.

Analysis and prediction of produced water quantity and quality in the Permian Basin using machine learning techniques

Appropriate produced water (PW) management is critical for oil and gas industry. Understanding PW quantity and quality trends for one well or all similar wells in one region would significantly assist operators, regulators, and water treatment/disposal companies in optimizing PW management. In this research, historical PW quantity and quality data in the New Mexico portion (NM) of the Permian Basin from 1995 to 2019 was collected, pre-processed, and analyzed to understand the distribution, trend and characteristics of PW production for potential beneficial use. Various machine learning algorithms were applied to predict PW quantity for different types of oil and gas wells. Both linear and non-linear regression approaches were used to conduct the analysis. The prediction results from five-fold cross-validation showed that the Random Forest Regression model reported high prediction accuracy. The AutoRegressive Integrated Moving Average model showed good results for predicting PW volume in time series. The water quality analysis results showed that the PW samples from the Delaware and Artesia Formations (mostly from conventional wells) had the highest and the lowest average total dissolved solids concentrations of 194,535 mg/L and 100,036 mg/L, respectively. This study is the first research that comprehensively analyzed and predicted PW quantity and quality in the NM-Permian Basin. The results can be used to develop a geospatial metrics analysis or facilitate system modeling to identify the potential opportunities and challenges of PW management alternatives within and outside oil and gas industry. The machine learning techniques developed in this study are generic and can be applied to other basins to predict PW quantity and quality.

Characterization and Treatment Technologies Applied for Produced Water in Qatar

Qatar is one of the major natural gas (NG) producing countries, which has the world’s third-largest NG reserves besides the largest supplier of liquefied natural gas (LNG). Since the produced water (PW) generated in the oil and gas industry is considered as the largest waste stream, cost-effective PW management becomes fundamentally essential. The oil/gas industries in Qatar produce large amounts of PW daily, hence the key challenges facing these industries reducing the volume of PW injected in disposal wells by a level of 50% for ensuring the long-term sustainability of the reservoir. Moreover, it is important to study the characteristics of PW to determine the appropriate method to treat it and then use it for various applications such as irrigation, or dispose of it without harming the environment. This review paper targets to highlight the generation of PW in Qatar, as well as discuss the characteristics of chemical, physical, and biological treatment techniques in detail. These processes and methods discussed are not only applied by Qatari companies, but also by other companies associated or in collaboration with those in Qatar. Finally, case studies from different companies in Qatar and the challenges of treating the PW are discussed. From the different studies analyzed, various techniques as well as sequencing of different techniques were noted to be employed for the effective treatment of PW.

Efficacy of oil and gas produced water as a dust suppressant

The effectiveness of oil and gas produced water (OGPW) applied to unpaved roads to reduce particulate matter (PM₁₀) generation has not been well-characterized. Here we quantify the efficacy of OGPW compared to commercial and alternative byproducts as dust suppressants applied to unpaved roads and estimate efficacy of a dust suppressant extrapolated from both lab experiments and published data for OGPW across U.S. states. Both treated and untreated OGPW, simulated brines, and commercial dust suppressants were characterized by major and trace element composition and then applied to road aggregate in the laboratory. PM₁₀ generation after treatment was quantified, both before and after simulated rain events to assess the need for multiple applications. We found the dust suppression efficacy of all OGPW to be less than commercial products and alternative byproducts such as waste soybean oil. In addition, OGPW lost efficacy following simulated rain events, which would require repeated applications of OGPW to maintain dust suppression. The dust suppression efficacy of OGPW can be estimated based on two chemical measurements, the sodium absorption ratio (SAR) and the total dissolved solids (TDS). OGPW with the lowest SAR and highest TDS performed best as dust suppressants while high SAR and lower TDS led to greater dust generation.

Bioelectrochemical system as an innovative technology for treatment of produced water from oil and gas industry: A review

Disposal of the high volume of produced water (PW) is a big challenge to the oil and gas industry. High cost of conventional treatment facilities, increasing energy prices and environmental concern had focused governments and the industry itself on more efficient treatment methods. Bioelectrochemical system (BES) has attracted the attention of researchers because it represents a sustainable way to treat wastewater. This is the first review that summarizes the progress done in PW-fed BESs with a critical analysis of the parameters that influence their performances. Inoculum, temperature, hydraulic retention time, external resistance, and the use of real or synthetic produced water were found to be deeply related to the performance of BES. Microbial fuel cells are the most analyzed BES in this field followed by different types of microbial desalination cells. High concentration of sulfates in PW suggests that most of hydrocarbons are removed mainly by using sulfates as terminal electron acceptor (TEA), but other TEAs such as nitrate or metals can also be employed. The use of real PW as feed in experiments is highly recommended because biofilms when using synthetic PW are not the same. This review is believed to be helpful in guiding the research directions on the use of BES for PW treatment, and to speed up the practical application of BES technology in oil and gas industry.

Potential for Biomass Production and Remediation by Cultivation of the Marine Model Diatom Phaeodactylum tricornutum in Oil Field Produced Wastewater Media

While oilfield produced water (PW) is one of the largest, unclaimed wastewater streams of the oil industry, it could potentially be used as a cultivation medium for microalgae. Microalgae could help with the remediation of this water while also delivering biomass that can be transformed into valuable byproducts such as biofuels. The coupling of these two purposes is expected to cut production costs of biofuels while aiding environmental protection. In this study, we compared the cultivation capacity of the marine model diatom Phaeodactylum tricornutum in media at varying salinities and in media composed of PW from two oilfields in the Central Valley of California that differed drastically in the concentration of inorganic and organic constituents. Specifically, we measured the carrying capacity of these media, the maximum growth rates of P. tricornutum, its cellular lipid accumulation capacity, and its capacity to remediate the most polluted PW source. Our study shows that P. tricornutum can successfully adjust to the tested cultivation media through processes of short-term acclimation and long-term adaptation. Furthermore, the cultivation of P. tricornutum in the most heavily polluted PW source led to significant increases in cell yield and improved photosynthetic capacity during the stationary phase, which could be attributed chiefly to the higher levels of nitrate present in this PW source. Chemical water analyses also demonstrated the capability of P. tricornutum to remediate major nutrient content and potentially harmful elements like fluorine and copper. Because P. tricornutum is amenable to advanced genetic engineering, which could be taken advantage of to improve its cultivation resilience and productivity in an economic setting, we propose this study as a step towards essential follow-up studies that will identify the genetic regulation behind its growth in oilfield PW media and its remediation of the PW constituents.

Water-rock interaction and the concentrations of major, trace, and rare earth elements in hydrocarbon-associated produced waters of the United States

Studies of co-produced waters from hydrocarbon extraction across multiple energy-producing basins have generally focused on major ions or a few select tracers, and studies that examine trace elements and involve laboratory experiments have generally been basin specific. Here, new perspective is sought through a broad analysis of concentration data for 26 elements from three hydrocarbon well types using the U.S. Geological Survey National Produced Waters Geochemical Database (v2.3). Those data are compared to leachates (water, hydrochloric acid, and artificial brine) from 12 energy-resource related shales from across the United States. Both lower pH and higher ionic strength were associated with greater concentrations of many trace elements in produced waters. However, individual effects were difficult to distinguish because higher ionic strengths drive decreases in pH. Water-rock interactions in the leaching experiments generally replicated produced water concentrations for trace elements including Al, As, Cd, Co, Cu, Mo, Ni, Pb, Sb, Si, and Zn. Enhanced middle rare earth element (REE) mobilization relative to shale REE content occurred with low pH leachates. Produced water concentrations of Li, Sr, and Ba were not replicated by the leaching experiments. Patterns of high Li, Sr, and Ba concentrations and ratios relative to other elements across produced waters types indicate controls on these elements in many settings related to pore space pools of salts, brines, and ion-exchange sites affected by diagenetic processes. The size of those pools is diluted and masked by other water-rock interaction processes at the water-rock ratios necessitated by laboratory experiments. The results broadly link water-rock interaction processes and environmental patterns across a wide variety of produced waters and host formations and thus provide context for trace element data from other environmental and laboratory studies of such waters.

A review of treatment technologies for produced water in offshore oil and gas fields

Offshore oil and gas production is increasingly growing popular globally. Produced water (PW), which is the largest byproduct of oil and gas production, is a complex mixture of dissolved and undissolved organic and inorganic substances. PW contributes considerably to oil pollution in the offshore petroleum and gas industry owing to the organic substances, which mainly include hydrocarbons; this is a major concern to researchers because of the long-term adverse effects on the ecosystem. Since the development of offshore petroleum and gas industry, the PW treatment process has been classified into pretreatment, standard-reaching treatment, and advanced purification treatment based on the characteristics of PW and has been coupled with the environmental, economic, and regulatory considerations. The mechanism, design principle, application, and development of conventional technologies for PW treatment, such as gravity and enhanced gravity sedimentation, hydrocyclone, gas flotation, and medium filtration, are summarized in this study. Novel methods for further application, such as tubular separation, combined fibers coalescence, and membrane separation, are also discussed. Enhancement of treatment with multiple physical fields and environmentally friendly chemical agents, coupled with information control technology, would be the preferred PW treatment approach in the future. Moreover, the PW treatment system should be green, efficient, secure, and intelligent to satisfy the large-scale, unmanned, and abyssal exploration of offshore oil and gas production in the future.

Thermal Desalination of Produced Water—An Analysis of the Partitioning of Constituents into Product Streams and Its Implications for Beneficial Use Outside the O&G Industry

To understand partitioning of produced water (PW) constituents using thermal desalination, PW from the Delaware Basin was desalinated using a crystallization process and modeled using OLI Systems, Inc. (OLI, Parsippany, NJ, USA) chemistry software. The incorporation of a pretreatment step, steam stripping, prior to desalination was predicted to be effective at removing hydrocarbons (across a range of volatilities). As expected, inorganics were almost completely retained in the residual brine which was confirmed by OLI. As evaporation progressed, sparingly soluble compounds such as gypsum and celestite precipitated first and overall solids production at this stage was low (<1% of total solids). Further evaporation resulted in saturation of the residual brine with respect to NaCl, which started to precipitate in bulk up to a practical desalination limit of approximately 68% by mass (approximately 80% by volume). Beyond this point, the residual brine and solids mixture became too viscous to be pumped. Gravimetrically determined total dissolved solids (TDS) for PW, distillate and residual brine was found to be much higher than prediction, potentially due to the presence of neutral species, unstripped gases and organic (likely hydrophilic) constituents. Although the distillate had low TDS, the presence of unknown constituents including organic compounds in the distillate will likely require polishing treatment to mitigate potential toxicity associated with such compounds or transformation products post-release if discharged to the environment. OLI predicted near-complete retention of acetate in the residual brine. In contrast, laboratory tests showed nearly 50% partitioning of acetate into the distillate. Although not modeled, propionate partitioning was even higher at 94%. The inclusion of ammonia as an input species in OLI greatly improved the match between test data and model prediction. Additionally, it was hypothesized that acetic acid/acetate could have formed a volatile adduct with ammonia that increased its volatility and partitioning into the distillate. The findings of this study inform beneficial use by describing the chemical composition of desalination-derived distillate, brine and salt products. This study also identified alternative approaches, both treatment and non-treatment, for managing PW from unconventional operations.

Solar distillation of highly saline produced water using low-cost and high-performance carbon black and airlaid paper-based evaporator (CAPER)

The current technologies to treat hypersaline produced water (PW), such as thermal evaporation, are usually energy-intensive and cost-prohibitive. This study developed a low-cost, robust, solar-driven carbon black and airlaid paper-based evaporator (CAPER) for desalination of PW in the Permian Basin, United States. The study aims to better understand the removal of aromatic organic compounds and heavy metals during solar distillation, water output, and heat transfer. Outdoor experiments using CAPER assisted with polystyrene foam in a single slope, single basin solar still achieved an enhanced average evaporation rate of 2.23 L per m² per day, 165% higher than that of a conventional solar still. Analysis of heat transfer models demonstrated that CAPER solar evaporation achieved an evaporative heat transfer coefficient of ∼28.9 W m^-2·K^-1, 27.9% higher than without CAPER. The maximum fractional energy of evaporation and convection heat transfer inside the solar still with and without CAPER was ∼81.4% and ∼78.2%, respectively. For the PW with a total dissolved solids concentration of 134 g L^-1, solar distillation removed 99.97% salts and over 98% heavy metals. The high removal efficiency of 99.99% was achieved for Ca, Na, Mg, Mn, Ni, Se, Sr, and V. Organic characterization revealed that solar distillation removed over 83% aromatic compounds. Solar desalination using CAPER provides a low-cost and high-performance process to treat PW with high salinity and complex water chemistry for potential fit-for-purpose beneficial uses.

Isolation and characterization of a halophilic Modicisalibacter sp. strain Wilcox from produced water

We report the isolation a halophilic bacterium that degrades both aromatic and aliphatic hydrocarbons as the sole sources of carbon at high salinity from produced water. Phylogenetic analysis of 16S rRNA-gene sequences shows the isolate is a close relative of Modicisalibacter tunisiensis isolated from an oil-field water in Tunisia. We designate our isolate as Modicisalibacter sp. strain Wilcox. Genome analysis of strain Wilcox revealed the presence of a repertoire of genes involved in the metabolism of aliphatic and aromatic hydrocarbons. Laboratory culture studies corroborated the predicted hydrocarbon degradation potential. The strain degraded benzene, toluene, ethylbenzene, and xylenes at salinities ranging from 0.016 to 4.0 M NaCl, with optimal degradation at 1 M NaCl. Also, the strain degraded phenol, benzoate, biphenyl and phenylacetate as the sole sources of carbon at 2.5 M NaCl. Among aliphatic compounds, the strain degraded n-decane and n-hexadecane as the sole sources of carbon at 2.5 M NaCl. Genome analysis also predicted the presence of many heavy metal resistance genes including genes for metal efflux pumps, transport proteins, and enzymatic detoxification. Overall, due to its ability to degrade many hydrocarbons and withstand high salt and heavy metals, strain Wilcox may prove useful for remediation of produced waters.

Mobilization of Arsenic and Other Naturally Occurring Contaminants during Managed Aquifer Recharge: A Critical Review

Population growth and climate variability highlight the need to enhance freshwater security and diversify water supplies. Subsurface storage of water in depleted aquifers is increasingly used globally to alleviate disparities in water supply and demand often caused by climate extremes including floods and droughts. Managed aquifer recharge (MAR) stores excess water supplies during wet periods via infiltration into shallow underlying aquifers or direct injection into deep aquifers for recovery during dry seasons. Additionally, MAR can be designed to improve recharge water quality, particularly in the case of soil aquifer treatment and riverbank filtration. While there are many potential benefits to MAR, introduction of recharge water can alter the native geochemical and hydrological conditions in the receiving aquifer, potentially mobilizing toxic, naturally occurring (geogenic) contaminants from sediments into groundwater where they pose a much larger threat to human and ecosystem health. On the basis of the present literature, arsenic poses the most widespread challenge at MAR sites due to its ubiquity in subsurface sediments and toxicity at trace concentrations. Other geogenic contaminants of concern include fluoride, molybdenum, manganese, and iron. Water quality degradation threatens the viability of some MAR projects with several sites abandoning operations due to arsenic or other contaminant mobilization. Here, we provide a critical review of studies that have uncovered the geochemical and hydrological mechanisms controlling mobilization of arsenic and other geogenic contaminants at MAR sites worldwide, including both infiltration and injection sites. These mechanisms were evaluated based on site-specific characteristics, including hydrological setting, native aquifer geochemistry, and operational site parameters (e.g., source of recharge water and recharge/recovery cycling). Observed mechanisms of geogenic contaminant mobilization during MAR via injection include shifting redox conditions and, to a lesser extent, pH-promoted desorption, mineral solubility, and competitive ligand exchange. The relative importance of these mechanisms depends on various site-specific, operational parameters, including pretreatment of injection water and duration of injection, storage, and recovery phases. This critical review synthesizes findings across case studies in various geochemical, hydrological, and operational settings to better understand controls on arsenic and other geogenic contaminant mobilization and inform the planning and design of future MAR projects to protect groundwater quality. This critical review concludes with an evaluation of proposed management strategies for geogenic contaminants and identification of knowledge gaps regarding fate and transport of geogenic contaminants during MAR.

Biomineralization of hypersaline produced water using microbially induced calcite precipitation

Reusing produced water (PW) as the subsequent hydraulic fracturing fluid is currently the most economical and dominant practice in the shale oil and gas industry. However, high Ca²⁺ present in PW needs to be removed prior to reuse to minimize the potential for well clogging and formation damage. In this study, the microbially induced calcite precipitation (MICP), as an emerging biomineralization technique mediated by ureolytic bacteria, was employed to remove Ca²⁺ and toxic contaminants from hypersaline PW for the first time. Batch and continuous studies demonstrated the feasibility of MICP for Ca²⁺ removal from hypersaline PW under low urea and nutrient conditions. Throughout the continuous biofiltration operation with biochar as the media, high removal efficiencies of Ca²⁺ (~96%), organic contaminants (~100%), and heavy metals (~100% for As, Cd, Mn and Ni, 92.2% for Ba, 94.2% for Sr) were achieved when PW co-treated with synthetic domestic wastewater (SDW) under the condition of PW:SDW = 1:1 & urea 4 g/L. Metagenomic sequencing analysis showed that a stable ureolytic bacterial consortium (containing Sporosarcina and Arthrobacter at the genus level) was constructed in the continuous biofiltration system under hypersaline conditions, which may play a crucial role during the biomineralization process. Moreover, the combination of the MICP and ammonium recovery could significantly reduce the acute toxicity of PW towards Vibrio fischeri by 72%. This research provides a novel insight into the biomineralization of Ca²⁺ and heavy metals from hypersaline PW through the MICP technique. Considering the low cost and excellent treatment performance, the proposed process has the potential to be used for both hydraulic fracturing reuse and desalination pretreatment on a large scale.

Geochemical and geophysical indicators of oil and gas wastewater can trace potential exposure pathways following releases to surface waters

Releases of oil and gas (OG) wastewaters can have complex effects on stream-water quality and downstream organisms, due to sediment-water interactions and groundwater/surface water exchange. Previously, elevated concentrations of sodium (Na), chloride (Cl), barium (Ba), strontium (Sr), and lithium (Li), and trace hydrocarbons were determined to be key markers of OG wastewater releases when combined with Sr and radium (Ra) isotopic compositions. Here, we assessed the persistence of an OG wastewater spill in a creek in North Dakota using a combination of geochemical measurements and modeling, hydrologic analysis, and geophysical investigations. OG wastewater comprised 0.1 to 0.3% of the stream-water compositions at downstream sites in February and June 2015 but could not be quantified in 2016 and 2017. However, OG-wastewater markers persisted in sediments and pore water for 2.5 years after the spill and up to 7.2-km downstream from the spill site. Concentrations of OG wastewater constituents were highly variable depending on the hydrologic conditions. Electromagnetic measurements indicated substantially higher electrical conductivity under the bank adjacent to a seep 7.2 km downstream from the spill site. Geomorphic investigations revealed mobilization of sediment is an important contaminant transport process. Labile Ba, Ra, Sr, and ammonium (NH₄) concentrations extracted from sediments indicated sediments are a long-term reservoir of these constituents, both in the creek and on the floodplain. Using the drivers of ecological effects identified at this intensively studied site we identified 41 watersheds across the North Dakota landscape that may be subject to similar episodic inputs from OG wastewater spills. Effects of contaminants released to the environment during OG waste management activities remain poorly understood; however, analyses of Ra and Sr isotopic compositions, as well as trace inorganic and organic compound concentrations at these sites in pore-water provide insights into potentials for animal and human exposures well outside source-remediation zones.

Immobilization of Rhodococcus qingshengii strain FF on the surface of polyethylene and its adsorption and biodegradation of mimic produced water

Low pH and high salinity characteristic of produced water (PW) posed a big challenge for the direct biological treatment. The immobilization of R. qingshengii strain FF, which degraded petroleum effectively under low pH, and application of immobilized R. qingshengii strain FF in treating mimic PW was studied in this work. The immobilization of R. qingshengii strain FF on the surface of polyethylene foam (PEF), one type of waste packaging materials, was optimized using the response surface methodology. Under optimum conditions, cell density of R. qingshengii strain FF immobilized on the surface of PEF reached 388 mg (cells)/g(PEF). In addition, a few factors, including hydraulic retention time (HRT), pH and salinity, were studied for treating mimic PW using immobilized R. qingshengii strain FF. The result of this study demonstrated that TPH degradation efficiency of PW by immobilized R. qingshengii strain FF reached above 90% when HRT was longer than 8 h. Weak acid and high salinity conditions only moderately decreased TPH. Asphalt, alkanes and aromatic hydrocarbon contained in petroleum can be degraded to some extent. These results indicated that immobilized R. qingshengii strain FF can be used as a highly efficient strain which could be used in biological treatment of real PW.

Understanding controls on the geochemistry of hydrocarbon produced waters from different basins across the US

The most massive waste stream generated by conventional and unconventional hydrocarbon exploration is the produced water (PW). The costs and environmental issues associated with the management and disposal of PW, which contains high concentrations of inorganic and organic pollutants, is one of the most challenging problems faced by the oil and gas industry. Many of the current strategies for the reuse and recycling of PW are inefficient because of varying water demand and the spatial and temporal variations in the chemical composition of PW. The chemical composition of PW is controlled by a multitude of factors and can vary significantly over time. This study aims to understand different parameters and processes that control the quality of PW generated from hydrocarbon-bearing formations by analyzing relationships between their major ion concentrations, O, H, and Sr isotopic composition. We selected PW data sets from three conventional (Trenton, Edwards, and Wilcox Formations) and four unconventional (Lance, Marcellus, Bakken, and Mesaverde Formations) oil and gas formations with varying lithology and depositional environment. Using comparative geochemical data analysis, we determined that the geochemical signature of PW is controlled by a complex interplay of several factors, including the original source of water (connate marine vs. non-marine), migration of the basinal fluids, the nature and degree of water-mineral-hydrocarbon interactions, water recharge, processes such as evaporation and ultrafiltration, and production techniques (conventional vs. unconventional). The development of efficient PW recycle and reuse strategies requires a holistic understanding of the geological and hydrological history of each formation to account for the temporal and spatial heterogeneities.

A Critical Review of Analytical Methods for Comprehensive Characterization of Produced Water

Produced water is the largest waste stream associated with oil and gas production. It has a complex matrix composed of native constituents from geologic formation, chemical additives from fracturing fluids, and ubiquitous bacteria. Characterization of produced water is critical to monitor field operation, control processes, evaluate appropriate management practices and treatment effectiveness, and assess potential risks to public health and environment during the use of treated water. There is a limited understanding of produced water composition due to the inherent complexity and lack of reliable and standardized analytical methods. A comprehensive description of current analytical techniques for produced water characterization, including both standard and research methods, is discussed in this review. Multi-tiered analytical procedures are proposed, including field sampling; sample preservation; pretreatment techniques; basic water quality measurements; organic, inorganic, and radioactive materials analysis; and biological characterization. The challenges, knowledge gaps, and research needs for developing advanced analytical methods for produced water characterization, including target and nontarget analyses of unknown chemicals, are discussed.