Nanomaterial-Based Drilling Fluids for Exploitation of Unconventional Reservoirs: A Review

Elevated temperature and pressure performance of water based drilling mud with green synthesized zinc oxide nanoparticles and biodegradable polymer

Water-based mud (WBM) faces challenges in high-temperature, high-pressure (HTHP) conditions due to fluid loss and property degradation. Enhancing eco-friendly drilling fluids with optimal rheology is crucial for sustainable, cost-effective, and environmentally safe drilling operations. This study formulated a WBM using green-synthesized zinc oxide (ZnO) nanoparticles (NPs, ~ 45 nm) and tragacanth gum (TG), a biodegradable natural polymer. The synthesized ZnO NPs were comprehensively characterized using energy-dispersive X-ray spectroscopy (EDS), field-emission scanning electron microscopy (FE-SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA/DTG) to determine their structural, morphological, and chemical properties. Rheological properties, including flow behavior index (n), consistency index (K), plastic viscosity (PV), and yield point (YP), were analyzed at 25, 50, and 75 °C using the Bingham-plastic and Power-law models. The accuracy of the model was validated using Analysis of Variance (ANOVA), which assessed the significance of the results. Additionally, Design Expert software was utilized to optimize the concentrations of TG and ZnO for elevated temperature applications. Moreover, the response surface methodology (RSM) results were evaluated by reporting the R2 and accuracy metrics, confirming the strong correlation between predicted and actual values, which demonstrates the model's robustness. Three optimal samples underwent HTHP filtration tests at 120 °C and 500 psi. The ideal formulation of 750 ppm TG and 0.25 wt% ZnO NPs improved PV by 27.84%, YP by 43.16%, reduced fluid loss by 54.16%, and mud cake thickness by 25%. The optimized sample showed superior performance, with a 'K' of 56.12 cp and a 'n' of 0.2272, ensuring effectiveness under HTHP conditions. This sustainable formulation reduced environmental contamination risks and drilling fluid consumption while enhancing operational efficiency.

Evaluation of using micronized saudi calcite in ilmenite-weighted water-based drilling fluid

A high-density water-based drilling fluid (WBDF) is crucial for maintaining wellbore stability, controlling formation pressures, and optimizing drilling performance in challenging subsurface conditions. In the present research, the effect of micronized calcium carbonate (calcite), extracted from the Aruma formation outcrop, is evaluated as one of the additives that could be added to the ilmenite-weighted WBDF to enhance and optimize its properties. Various concentrations of Calcite microparticles were introduced into identical fluid formulations to assess their impact. The concentrations ranged from 0, 10, 20, to 30 lb/bbl, providing a comprehensive examination of the effects of calcite microparticles across a spectrum of concentrations within the fluid. The results highlighted that adding Barite microparticles to the WBDF revealed a notable enhancement in rheological properties. Specifically, the yield point demonstrated an increase of 37%, 37%, and 11% for concentrations of 10, 20, and 30 lb/bbl of calcite, respectively. Equally significant, high-pressure-high-temperature (HPHT) filtration analysis indicated a considerable enhancement for the fluids containing calcite microparticles. A reduction of 14.5%, 24.6%, and 13% were observed in HPHT filtrate for concentrations of 10 lb/bbl, 20 lb/bbl, and 30 lb/bbl respectively. Simultaneously, there is a reduction in filter cake thickness by 20%, 40%, and 20%, respectively. No ilmenite settling was observed in the sample containing 20 lb/bbl of calcite, unlike the other concentrations. These diverse results strongly suggest that the optimal concentration for calcite microparticles is 20 lb/bbl. The combined utilization of the optimal concentration of calcite microparticles alongside the established additives proves to be an effective strategy for optimizing the ilmenite-weighted WBDF performance in terms of both thermal stability and rheological behavior.

Evaluating the Effect of Claytone-EM on the Performance of Oil-Based Drilling Fluids

This study provides a detailed characterization and evaluation of Claytone-EM as a rheological additive to enhance the performance of oil-based drilling fluids (OBDFs) under high-pressure, high-temperature (HPHT) conditions. It also offers a comparative evaluation of the effectiveness of Claytone-EM with an existing organoclay, analyzing their mineral and chemical compositions, morphologies, and particle sizes. A series of experiments are performed to evaluate Claytone-EM's influence on crucial drilling mud properties, such as mud density, electrical stability, sagging tendency, rheology, viscoelastic properties, and filtration properties, to formulate a stable and high-performing OBDF. Results indicated that Claytone-EM had no significant impact on mud density but remarkably enhanced emulsion stability. Claytone-EM effectively mitigated sagging issues under both static and dynamic conditions, leading to improvements in the plastic viscosity (PV), yield point (YP), apparent viscosity (AV), and YP/PV ratio. The PV, YP, AV, and YP/PV ratios were improved by 11, 85, 28, and 66% increments, respectively, compared with those of the drilling fluid formulated with MC-TONE. The addition of Claytone-EM resulted in enhancing gel strength and improving the filtration properties of the drilling fluid. The filtration volume was reduced by 2% from 5.0 to 4.9 cm3, and the filter cake thickness had a 13% reduction from 2.60 to 2.26 mm. These findings highlight Claytone-EM as a valuable additive for enhancing OBDF performance, particularly under challenging HPHT conditions. Its ability to provide emulsion stability, reduce static and dynamic sag, and control filtration holds the potential to enhance drilling operations, minimize downtime, and bolster wellbore stability. This study acknowledges certain limitations, including its temperature range, which could benefit from exploration at extreme temperatures. Additionally, the absence of flow experiments limits a comprehensive understanding of sag effects, and further research and field-scale evaluations are recommended to validate and optimize the application of Claytone-EM in OBDFs.

Investigating the efficacy of novel organoclay as a rheological additive for enhancing the performance of oil-based drilling fluids

Oil-based drilling fluids (OBDFs) are extensively used in the drilling industry due to their superior performance in challenging drilling conditions. These fluids control wellbore stability, lubricate the drill bit, and transport drill cuttings to the surface. One important component of oil-based drilling fluids is the viscosifier, which provides rheological properties to enhance drilling operations. This study evaluates the effectiveness of Claytone-IMG 400, a novel rheological agent, in enhancing the performance of OBDFs under high-pressure and high-temperature (HPHT) conditions. A comparative analysis was conducted with a pre-existing organoclay (OC) to assess the improvements achieved by Claytone-IMG 400. The OCs were analyzed using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size distribution (PSD) to identify their mineral and chemical compositions, morphologies, and particle sizes. The drilling fluid density, electrical stability, sagging tendency, rheological properties, viscoelastic properties, and filtration properties were studied to formulate a stable and high-performance drilling fluid. The results confirmed that the novel OC does not affect the drilling fluid density but enhances the emulsion stability with a 9% increment compared with the drilling fluid formulated with MC-TONE. The sagging experiments showed that Claytone-IMG 400 prevented the sagging issues in both static and dynamic conditions. Also, Claytone-IMG 400 improved the plastic viscosity (PV), yield point (YP), and apparent viscosity (AV). The PV, YP, and AV were improved by 30%, 38%, and 33% increments respectively compared with the drilling fluid formulated with MC-TONE. The YP/PV ratio increased with a 6% increment from 1.12 to 1.19. Moreover, the gel strength (GS) was significantly increased, and the filtration properties were enhanced. The filtration volume was reduced by 10% from 5.0 to 4.5 cm3, and the filter cake thickness had a 37.5% reduction from 2.60 to 1.89 mm. The novelty of this study is highlighted by the introduction and evaluation of Claytone-IMG 400 as a new rheological additive for safe, efficient, and cost-effective drilling operations. The results indicate that Claytone-IMG 400 significantly improves the stability and performance of OBDFs, thereby reducing wellbore instability and drilling-related problems.

Case studies of radioactivity of drilling mud for in situ leaching uranium mining in China

The drilling mud from in situ leaching uranium mining is a type of low-radioactivity waste that contains natural nuclides and other harmful substances. In order to determine whether the drilling mud can meet the requirements of radioactive exemption management standards, field investigations and data simulations were conducted in this study. Two typical uranium mines were selected for onsite investigations. Drilling mud from different layers (i.e., the upper covering layer and ore-bearing layer) and from different stages (e.g., logging stage mud, drilling expansion stage mud, and mixed mud) was sampled. For each sample, the ²³⁸U and ²²⁶Ra concentrations of the solid components and the U and ²²⁶Ra concentrations of the supernatant were analyzed. The results revealed that the highest ²³⁸U and ²²⁶Ra concentrations of the solid components were 4122 Bq/kg and 4077 Bq/kg, while the ²³⁸U and ²²⁶Ra concentrations of the mixed drilling mud were all less than 300 Bq/kg. A radioactivity estimation model was established for scenario analysis. Exemption management screening lines of waste drilling mud, which can be used to classify and treat the drilling project according to the deposit's grade and conditions, were proposed for in situ leaching drilling projects.

Lubricity and Rheological Properties of Highly Dispersed Graphite in Clay-Water-Based Drilling Fluids

Improving the tribological characteristics of water-based drilling fluids by adding graphene-based lubricants has garnered attention because of the potential for a range of inorganic-material-based additives at high temperature. In this study, we constructed a green and simple adsorption approach to prepare highly dispersed graphite using a cationic surfactant for graphite modification. The findings demonstrated that the prepared graphite was highly dispersed in water and had a low sedimentation rate and small contact angle in distilled water. The concentration dosage of cetyltrimethylammonium chloride (CTAC) on graphite was 0.02 g/g. We evaluated the performance of the modified graphite as a lubricated additive in water-based drilling through a rheological study and viscosity coefficient measurement. The results showed that the viscosity coefficient of drilling fluid with 0.05% modified graphite was reduced by 67% at 180 °C. We proved that the modified graphite can significantly improve the lubrication performance of drilling fluid. Furthermore, we revealed the lubrication mechanism by analyzing the chemical structural and crystalline and morphological features of graphite through a particle size test, zeta potential test, Fourier transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRD), and scanning electron microscopy (SEM) measurements. The results indicated that the modification of graphite by CTAC only occurs through physical adsorption, without changing the crystal structure. These findings provide a reference for the development of high-performance water-based drilling fluids.

Thermal and Rheological Properties of Hydrophobic Nanosilica in Sunflower Oil Suspensions at High Pressures

Nowadays, the reduction of the environmental impact associated with the operation of the oil industry is a primary concern. A growing trend is to develop low-toxicity formulations based on biodegradable components. In this sense, vegetable oils structured with nanomaterials could be an alternative to mineral or synthetic oils for sustainable fluid formulations. Hydrophobic fumed silica nanoparticles have the capability to change the rheological behavior of oil in suspensions, providing a large variety of non-Newtonian behaviors over a wide range of temperatures, from shear-thinning to gel-like, depending on the concentration and the nanosilica’s hydrophobicity, that permits the design of fluids with selected characteristic and applications. This work explores the microstructure and the rheological behavior of hydrophobic fumed silica dispersed in a sunflower oil as a function of temperature and pressure. The results suggest that the suspensions of hydrophobic silica in sunflower oil reveals appropriate rheological and thermal properties over a wide range of temperatures and pressures to serve as components of sustainable drilling fluids.

The Influences of NP100 Surfactant and Pine-Oil Concentrations on Filtrate Volume and Filter-Cake Thickness of Microemulsion-Based Drilling Fluids (O/W)

In this work, nonionic surfactant NP100 and pine oil influences on the filtrate volume (FV) and the filter-cake thickness (thkns) of microemulsified drilling fluids were studied. A ternary phase diagram was obtained to define the microemulsion region, where a 2k factorial design was used with the addition of four center points and axial points. Twelve microemulsion points were defined and used later in the formulation of the investigated drilling fluids. The results showed that the increase in the surfactant and pine oil’s concentration increased FV and thkns, withthe oil phase being the most influential component in the filtrate volume and the surfactant being the most influential in the filter-cake thickness. Statistically significant models were obtained. The optimal concentrations were determined for the lowest FV and thkns; 45% of surfactant and 5% of pine oil for the filtrate volume (1.3 mL), and 45% of surfactant and 15% of pine oil for the filter-cake thickness (0.64 mm).

Synthesis, Characterization and Filtration Properties of Ecofriendly Fe3O4 Nanoparticles Derived from Olive Leaves Extract

Recently, value-added nanomaterials including nanoparticles or nanofluids have been significantly used in designing drilling fluids with tunable rheological properties to meet specific downhole and environmental requirements. In this work, we report novel water-based drilling fluids (WBDF) containing eco-friendly Fe₃O₄ nanoparticles (Fe₃O₄-NPs) prepared by using olive leaves extract (OLE) as a reducing and capping agent. A series of economical and excellent performance of WBDF was obtained by introducing low, medium, and high concentrations of Fe₃O₄-NPs into the conventional WBDF. The synthesis of Fe₃O₄-NPs was accomplished through the thermal decomposition of iron precursors in an organic medium. NPs were added to the based fluid at concentrations of 0.01, 0.1, and 0.5 wt%. Emission scanning microscopy (FESEM), field- and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Energy-dispersive X-ray analysis (EDX) were used for Fe₃O₄-NPs analysis. Compared to the conventional WBDF, the addition of Fe₃O₄-NPs as an additive in the based fluids has been investigated to help increasing viscosity and yield point, which is advantageous for hole cleaning, as well as decreasing fluid loss and mud cake thickness.

Utilization of Eco-Friendly Waste Generated Nanomaterials in Water-Based Drilling Fluids; State of the Art Review

An important aspect of hydrocarbon drilling is the usage of drilling fluids, which remove drill cuttings and stabilize the wellbore to provide better filtration. To stabilize these properties, several additives are used in drilling fluids that provide satisfactory rheological and filtration properties. However, commonly used additives are environmentally hazardous; when drilling fluids are disposed after drilling operations, they are discarded with the drill cuttings and additives into water sources and causes unwanted pollution. Therefore, these additives should be substituted with additives that are environmental friendly and provide superior performance. In this regard, biodegradable additives are required for future research. This review investigates the role of various bio-wastes as potential additives to be used in water-based drilling fluids. Furthermore, utilization of these waste-derived nanomaterials is summarized for rheology and lubricity tests. Finally, sufficient rheological and filtration examinations were carried out on water-based drilling fluids to evaluate the effect of wastes as additives on the performance of drilling fluids.

Study on the Impact Pressure of Swirling-Round Supercritical CO2 Jet Flow and Its Influencing Factors

Supercritical carbon dioxide (SC-CO2) jet is capable of decreasing the threshold pressure of rock breakage and mitigating formation damage, owing to its low viscosity, high diffusivity, and extremely-low surface tension. The swirling-round jet holds the advantages of both a swirling jet and a round jet. Therefore, the comprehensive technique, swirling-round SC-CO2 (SR-SC-CO2) jet, is expected to substantially enhance rock-breaking efficiency. However, theoretical analysis of the flow field characteristics of SR-SC-CO2 has not been reported yet. This work aims to lay a theoretical foundation for employing SR-SC-CO2 in drilling and fracturing. The flow field is simulated using Naiver-Stokes equations and the RNG k-ε turbulence model. Sensitivity analysis, regarding pressure drop of the nozzle, confining pressure, fluid temperature, jetting distance, the diameter of the nozzle’s central hole, and grooving area, are performed. We show that the combined swirling-round SC-CO2 jet flow could maintain a relatively larger axial as well as tangential velocity compared to a single approach of swirling jet or round jet, enabling one to acquire a deeper oillet and expand the perforation area effectively. The simulation results substantiate the enormous potential of SR-SC-CO2 in improving rock-breaking efficiency and clarify the influence of relevant parameters on the impact pressure of the jet flow.

H2S Scavenging Capacity and Rheological Properties of Water-Based Drilling Muds

Drilling hydrocarbon formations where hydrogen sulfide (H₂S) is present could lead to the carryover of H₂S with the drilling mud (i.e., drilling fluid) to the surface, exposing working personnel to this lethal gas. Additionally, H₂S is very corrosive, causing severe corrosion of metal parts of the drilling equipment, which in turn results in serious operational problems. The addition of an effective H₂S scavenger(s) in the drilling mud formulations will overcome these health, safety, and operational issues. In this work, zinc oxide (ZnO), which is a common H₂S scavenger, has been incorporated into water-based drilling mud. The H₂S scavenging performance of this ZnO-containing drilling mud has been assessed. Additionally, drilling mud formulations containing either copper nitrate (Cu(NO₃)₂·3H₂O) or potassium permanganate (KMnO₄) have been prepared, and their H₂S scavenging performances have been studied and compared to that of the ZnO-containing drilling mud. It has been observed that the scavenging performance (in terms of the H₂S amounts scavenged up to the breakthrough time and at the saturation condition) of the ZnO-containing drilling mud is very poor compared to those of the copper nitrate-containing and KMnO₄-containing drilling muds. For instance, the amounts of H₂S scavenged up to the breakthrough time by ZnO-containing, copper nitrate-containing, and KMnO₄-containing drilling muds were 5.5, 15.8, and 125.3 mg/g, respectively. Furthermore, the amounts of H₂S scavenged at the saturation condition by these drilling muds were, respectively, 35.1, 146.8, and 307.5 mg/g, demonstrating the superiority of the KMnO₄-containing drilling mud. Besides its attractive H₂S scavenging performance, the KMnO₄-containing drilling mud possessed more favorable rheological properties [i.e., plastic viscosity (PV), yield point (YP), carrying capacity of the drill cuttings, and gelling characteristics] relative to the base and the ZnO-containing and copper nitrate-containing drilling muds. The addition of KMnO₄ to the base drilling mud increased its apparent viscosity, PV, and YP by 20, 33, and 10%, respectively. Additionally, all tested drilling muds possessed acceptable fluid loss characteristics. To the best of our knowledge, there are so far no published studies concurrently tackling the H₂S scavenging (i.e., breakthrough time, breakthrough capacity, saturation time, saturation capacity, and scavenger utilization) and the rheological properties of water-based drilling muds, as demonstrated in the current study, highlighting the novelty of this work.

Experimental Research of Shale Pellet Swelling in Nano-Based Drilling Muds

The drilling of clay-rich formations, such as shale, is an extremely demanding technical and technological process. Shale consists of mixed clay minerals in different ratios and in contact with water from drilling mud. It tends to swell and cause different wellbore instability problems. Usually, the petroleum industry uses various types of salt and/or polymers as shale hydration inhibitors. The aim of this research was to determine whether nanoparticles can be used as shale swelling inhibitors because due to their small size they can enter the shale nanopores, plug them and stop further penetration of mud filtrate into the shale formation. Swelling of bentonite-calcium carbonate pellets after 2 and 24 h in water and drilling mud (water, bentonite, PAC and NaOH) without nanoparticles and with addition of TiO2 (0.5, 1 and 1.5 wt%) and SiO2 (0.5, 1 and 1.5 wt%) nanoparticles was measured using a linear swell meter. Additionally, granulometric analyses of bentonite as well as the zeta potential of tested muds containing nanoparticles were performed. Based on the laboratory research, it can generally be concluded that the addition of SiO2 and TiO2 nanoparticles in water and base drilling mud reduces the swelling of pellets up to 40.06%.

Effect of Environment-Friendly Non-Ionic Surfactant on Interfacial Tension Reduction and Wettability Alteration; Implications for Enhanced Oil Recovery

Production from mature oil reservoirs can be optimized by using the surfactant flooding technique. This can be achieved by reducing oil and water interfacial tension (IFT) and modifying wettability to hydrophilic conditions. In this study, a novel green non-ionic surfactant (dodecanoyl-glucosamine surfactant) was synthesized and used to modify the wettability of carbonate reservoirs to hydrophilic conditions as well as to decrease the IFT of hydrophobic oil–water systems. The synthesized non-ionic surfactant was characterized by Fourier transform infrared spectroscopy (FTIR) and chemical shift nuclear magnetic resonance (HNMR) analyses. Further pH, turbidity, density, and conductivity were investigated to measure the critical micelle concentration (CMC) of surfactant solutions. The result shows that this surfactant alters wettability from 148.93° to 65.54° and IFT from 30 to 14 dynes/cm. Core-flooding results have shown that oil recovery was increased from 40% (by water flooding) to 59% (by surfactant flooding). In addition, it is identified that this novel non-ionic surfactant can be used in CO2 storage applications due to its ability to alter the hydrophobicity into hydrophilicity of the reservoir rocks.