Biomimetic functional hydrogel particles with enhanced adhesion characteristics for applications in fracture conformance control

Development and Application of High-Internal-Phase Water-in-Oil Emulsions Using Amphiphilic Nanoparticle-Based Emulsifiers

High-internal-phase water-in-oil (W/O) emulsions generated in situ have garnered considerable attention as novel profile control systems. However, conventional emulsifiers are unreactive and poorly dispersed in water, necessitating large dosages and resulting in poor injectivity. In this study, we synthesized amphiphilic nanoparticles (SiO2-NH2-DAC NPs) containing amine and long-chain alkyl groups using a one-pot method and investigated the stabilized emulsion properties. Our results indicated that W/O emulsions with a water-to-oil ratio (WOR) of 7:3 to 8:2 could be prepared with just 0.1 wt% of SiO2-NH2-DAC NPs under neutral and basic conditions, with demulsification occurring under acidic conditions (pH = 2.1), demonstrating the pH-responsiveness of the W/O emulsions. The emulsion viscosity increased from 150 to 2555 mPa·s at different WORs. An additional 18.7% oil recovery was achieved using SiO2-NH2-DAC NPs in a heterogeneous core, highlighting their potential as a promising profile control candidate.

Preparation and Evaluation of Physical and Chemical Properties of Resin Plugging System Suitable for Formation Plugging of Malignant Lost Circulation

Lost circulation is one of the important problems that restricts the speed and efficiency of oil and gas drilling and production. In this study, a resin plugging system was successfully developed for lost circulation formation. The resin plugging system showed excellent performance under high temperature and pressure conditions. The experimental results showed that the compressive strength of the resin plugging material can reach 9.23 MPa after curing, which is significantly higher than that of the traditional polymer gel material. The resin material can achieve effective curing in the temperature range of 60 °C to 100 °C, and the curing time decreases with the increase of temperature and only needs 3.46 h at 140 °C. The microstructure results showed that the resin material can form a chain or three-dimensional network structure after curing, which can effectively increase the toughness and strength of the cured plugging layer. Infrared and thermogravimetric analysis further confirmed the thermal stability of the chemical bonds in the material, and the initial decomposition temperature was about 241 °C, indicating that it had good thermal stability at about 300 °C. In addition, the effects of curing temperature, salinity, and drilling fluid pollution on the properties of the resin plugging agent were also investigated. The results showed that curing agent dosage and curing temperature are the key factors affecting curing time, while salinity and drilling fluid pollution affect the curing strength and overall properties of the materials. After adding 20% KCl polysulfonate drilling fluid, the compressive strength of the consolidated body decreased to 4.55 MPa. This study can provide an efficient and reliable plugging solution for malignant loss formation.

A comprehensive review on the behavior and evolution of oil droplets during oil/water separation by membranes

Membrane separation technology has significant advantages for treating oil-in-water emulsions. Understanding the evolution of oil droplets could reveal the interfacial and colloidal interactions, facilitate the design of advanced membranes, and improve the separation performances. This review on the characteristic behavior and evolution of oil droplets focuses on the advanced analytical techniques, and the subsequent fouling as well as demulsification effects during membrane separation. A detailed introduction is provided on microscopic observations and numerical simulations of the dynamic evolution of oil droplets, featuring real-time in-situ visualization and accurate reconstruction, respectively. Characteristic behaviors of these oil droplets include attachment, pinning, wetting, spreading, blockage, intrusion, coalescence, and detachment, which have been quantified by specific proposed parameters and criteria. The fouling process can be evaluated using Hermia and resistance models. The related adhesion force and intrusion pressure as well as droplet-droplet/membrane interfacial interactions can be accurately quantified using various force analysis methods and advanced force measurement techniques. It is encouraging to note that oil coalescence has been achieved through various effects such as electrostatic interactions, mechanical actions, Laplace pressure/surface free energy gradients, and synergistic effects on functional membranes. When oil droplets become destabilized and coalesce into larger ones, the functional membranes can overcome the limitations of size-sieving effect to attain higher separation efficiency. This not only bypasses the trade-off between permeability and rejection, but also significantly reduces membrane fouling. Finally, the challenges and potential research directions in membrane separation are proposed. We hope this review will support the engineering of advanced materials for oil/water separation and research on interface science in general.

Soft Movable Polymer Gel for Controlling Water Coning of Horizontal Well in Offshore Heavy Oil Cold Production

Horizontal well water coning in offshore fields is one of the most common causes of rapid declines in crude oil production and, even more critical, can lead to oil well shut down. The offshore Y oil field with a water cut of 94.7% urgently needs horizontal well water control. However, it is a challenge for polymer gels to meet the requirements of low-temperature (55 °C) gelation and mobility to control water in a wider range. This paper introduced a novel polymer gel cross-linked by hydrolyzed polyacrylamide and chromium acetate and phenolic resin for water coning control of a horizontal well. The detailed gelant formula and treatment method of water coning control for a horizontal well in an offshore field was established. The optimized gelant formula was 0.30~0.45% HPAM + 0.30~0.5% phenolic resin + 0.10~0.15% chromium acetate, with corresponding gelation time of 26~34 h at 55 °C. The results showed that this gel has a compact network structure and excellent creep property, and it can play an efficient water control role in the microscopic model. The thus-optimized gelants were successively injected with injection volumes of 500.0 m³. The displacement fluid was used to displace gelants into the lost zone away from the oil zone. Then, the formed gel can be worked as the chemical packer in the oil–water interface to control water coning after shutting in for 4 days of gelation. The oil-field monitoring data indicated that the oil rate increased from 9.2 m³/d to 20.0 m³/d, the average water cut decreased to 60~70% after treatment, and the cumulative oil production could obtain 1.035 × 10⁴ t instead of 3.9 × 10³ t.

Experimental Study on Physicochemical Properties of a Shear Thixotropic Polymer Gel for Lost Circulation Control

Polymer gel lost circulation control technology is a common and effective technique to control fractured lost circulation. The performance of a lost circulation control agent is the key to the success of lost circulation control techniques. In this study, rheological tests were used to study the physical and chemical properties of a shear thixotropic polymer gel system, such as anti-dilution, high temperature resistance and high salt resistance. The results showed that the shear thixotropic polymer gel system had the ability of anti-dilution, and the gel could be formed under a mixture of 3 times volume of heavy salt water and 3/7 volume white oil, and could keep the structure and morphology stable. Secondly, the gel formation time of shear thixotropic polymer gel system could be controlled and had good injection performance under the condition of 140 °C and different initiator concentrations. Meanwhile, the shear thixotropic polymer gel system had the ability of high temperature and high salt resistance, and the gel formation effect was good in salt water. When the scanning frequency was 4 Hz and the temperature was 140 °C, the storage modulus (G′) of the gel was 4700 Pa. The gel was dominated by elasticity and had excellent mechanical properties. By scanning electron microscope observation, it was found that the shear thixotropic polymer gel system had a stable three-dimensional reticular space skeleton under the condition of high salt, indicating that it had excellent ability to tolerate high salt. Therefore, the shear thixotropic polymer gel had high temperature and high salt resistance, dilution resistance and good shear responsiveness. It is believed that the results presented in this work are of importance for extending real-life applications of shear thixotropic polymer gel systems.

Atomic Force Microscopy (AFM) on Biopolymers and Hydrogels for Biotechnological Applications-Possibilities and Limits

Atomic force microscopy (AFM) is one of the microscopic techniques with the highest lateral resolution. It can usually be applied in air or even in liquids, enabling the investigation of a broader range of samples than scanning electron microscopy (SEM), which is mostly performed in vacuum. Since it works by following the sample surface based on the force between the scanning tip and the sample, interactions have to be taken into account, making the AFM of irregular samples complicated, but on the other hand it allows measurements of more physical parameters than pure topography. This is especially important for biopolymers and hydrogels used in tissue engineering and other biotechnological applications, where elastic properties, surface charges and other parameters influence mammalian cell adhesion and growth as well as many other effects. This review gives an overview of AFM modes relevant for the investigations of biopolymers and hydrogels and shows several examples of recent applications, focusing on the polysaccharides chitosan, alginate, carrageenan and different hydrogels, but depicting also a broader spectrum of materials on which different AFM measurements are reported in the literature.