A Self-Healing Gel with an Organic-Inorganic Network Structure for Mitigating Circulation Loss.

Lost circulation control remains a challenge in drilling operations. Self-healing gels, capable of self-healing in fractures and forming entire gel block, exhibit excellent resilience and erosion resistance, thus finding extensive studies in lost circulation control. In this study, layered double hydroxide, Acrylic acid, 2-Acrylamido-2-methylpropane sulfonic acid, and CaCl2 were employed to synthesize organic-inorganic nanocomposite gel with self-healing properties. The chemical properties of nanocomposite gels were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, X-ray photoelectron spectroscopy and thermogravimetric analysis. layered double hydroxide could be dispersed and exfoliated in the mixed solution of Acrylic acid and 2-Acrylamido-2-methylpropane sulfonic acid, and the swelling behavior, self-healing time, rheological properties, and mechanical performance of the nanocomposite gels were influenced by the addition of layered double hydroxide and Ca2+. Optimized nanocomposite gel AC6L3, at 90 °C, exhibits only a self-healing time of 3.5 h in bentonite mud, with a storage modulus of 4176 Pa, tensile strength of 6.02 kPa, and adhesive strength of 1.94 kPa. In comparison to conventional gel, the nanocomposite gel with self-healing capabilities demonstrated superior pressure-bearing capacity. Based on these characteristics, the nanocomposite gel proposed in this work hold promise as a candidate lost circulation material.

Hydrogenation of CO2 to Light Olefins over ZnZrOx /SSZ-13.

Converting CO2 to olefins is an ideal route to achieve carbon neutrality. However, selective hydrogenation to light olefins, especially single-component olefin, while reducing CH4 formation remains a great challenge. Herein, we developed ZnZrOx /SSZ-13 tandem catalyst for the highly selective hydrogenation of CO2 to light olefins. This catalyst shows C2 = -C4 = and propylene selectivity up to 89.4 % and 52 %, respectively, while CH4 is suppressed down to 2 %, and there is no obvious deactivation. It is demonstrated that the isolated moderate Brønsted acid sites (BAS) of SSZ-13 promotes the rapid conversion of intermediate species derived from ZnZrOx , thereby enhancing the kinetic coupling of the reactions and inhibit the formation of alkanes and improve the light olefins selectivity. Besides, the weaker BAS of SSZ-13 promote the conversion of intermediates into aromatics with 4-6 methyl groups, which is conducive to the aromatics cycle. Accordingly, more propene can be obtained by elevating the Si/Al ratio of SSZ-13. This provides an efficient strategy for CO2 hydrogenation to light olefins with high selectivity.

Highly selective conversion of CO2 to para-xylene over tandem catalysts.

ZnZrO/Mg-Si-ZSM-5 tandem catalysts enable CO2 hydrogenation to para-xylene (PX) with PX selectivity up to 28% and a proportion of PX in xylene up to 84%. SiO2 and MgO modification increases the PX selectivity by reducing the Brønsted acid sites and reducing the pore size of the zeolite.

A molecular dynamics study on adsorption mechanisms of polar, cationic, and anionic polymers on montmorillonite.

Adsorption of polymers on clay in aqueous solutions has wide applications in environmental, medical, and energy-related areas, but the interactions between polymers and clay under varied conditions are still not fully understood. In this study, we investigated the adsorption mechanisms of four polymers belonging to different categories, namely anionic poly(acrylic acid) (poly-AA), cationic poly(diallyldimethylammonium chloride) (poly-DADMAC), nonionic polyacrylamide (poly-AM), and the copolymer of AA and DADMAC (poly-AADADMAC). By using molecular dynamics simulations, we compared the desorption kinetics of these polymers at different temperatures and found that poly-AA and poly-AM have the weakest and strongest adsorption abilities, respectively. Polymer adsorptions are slightly more stable at higher pressures, and high salinity favors the adsorption of charged polymers. Further analysis suggests that the adsorption of anionic poly-AA is less stable than that of cationic poly-DADMAC because the latter is attracted to the negatively charged surface by direct coulombic forces, and poly-AM is stabilized by van der Waals forces and hydrogen bonds. This study provides insights on how to enhance the adsorption affinity of polymers on a clay surface and may help the design or improvement of polymer/clay nanocomposite materials.

Treatment of drilling fluid waste during oil and gas drilling: a review.

Oil and gas exploration and development provide important energy sources for the world, and drilling fluid is an essential engineering material for oil and gas exploration and development. During the drilling of oil wells, drilling fluids are eventually discarded as waste products after many cycles. Abandoned drilling fluid constitutes one of the largest wastes generated during oil and gas exploration and development. Drilling fluid contains many chemicals, which turn into pollutants during use. Furthermore, when drilling is carried out to reach reservoir, the drilling fluid becomes contaminated with crude oil. It may also mix with groundwater containing salts and heavy metals. The resulting pollutants and harmful substances threaten the environment, humans, animals, and plants. The variety and complexity of drilling fluid waste have increased in recent years. Various countries and regions are paying more attention to the ecological environment, and effective methods are urgently needed to solve problems associated with of environmental pollution caused by drilling fluid wastes. At present, various physical, chemical, and biological methods have been proposed for the treatment of drilling fluid wastes: safe landfilling, stabilization/solidification treatment, physicochemical treatment, thermal treatment, supercritical fluid treatment, bioremediation, etc. All of these methods show promising characteristics, and they each have advantages and limitations; thus, treatment methods need to be selected according to the actual application scenarios. This critical overview is based on an extensive literature review, and it summarizes and expounds on the current drilling fluid waste treatment technologies and proposes views future potential and outlook.

New Zwitterionic Polymer as a Highly Effective Salt- and Calcium-Resistant Fluid Loss Reducer in Water-Based Drilling Fluids.

To control the filtration loss of drilling fluids in salt-gypsum formations, a novel type of zwitterionic polymer gel (DNDAP) was synthesized by free radical polymerization, which was used as a salt- and calcium-resistant fluid loss reducer for water-based drilling fluids (WBDF). DNDAP was prepared with N, N-dimethylacrylamide (DMAA), N-vinylpyrrolidone (NVP), Diallyl dimethyl ammonium chloride (DMDAAC), 2-acrylamide-2-methylpropaneonic acid (AMPS), and isopentenol polyether (TPEG) as raw materials. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H-NMR) were used to characterize the composition and structure of the DNDAP copolymer. The thermal stability of DNDAP was evaluated by the use of thermogravimetric analysis (TGA). WBDF with DNDAP was analyzed for zeta potential and particle size and the corresponding filter cake underwent energy dispersive spectrum (EDS) analysis and scanning electron microscope (SEM) analysis. The results showed that the thermal decomposition of DNDAP mainly occurred above 303 °C. DNDAP exhibits excellent rheological and filtration properties in water-based drilling fluids, even under high-temperature aging (up to 200 °C) and high salinity (20 wt% NaCl or 5 wt% CaCl2) environments. The strong adsorption effect of DNDAP makes the particle size of bentonite reasonably distributed to form a dense mud cake that reduces filtration losses.

Application of PAC and flocculants for improving settling of solid particles in oilfield wastewater with high salinity and Ca2.

The suspended solids in wastewater from Rekabak oilfield, Kazakhstan, were characterized and treated with flocculants to enhance settling. The wastewater contained a high concentration of total dissolved solids and calcium ion. Scanning electron microscopy and energy dispersive X-ray analyses showed that suspended solids were mainly composed of corrosion products (iron oxides) and silicon dioxide particles. Also, much salt deposition from wastewater caused a large increase in the suspended solids value. The settling of solid particles in wastewater was investigated by turbidity decrease within 60 min. The particle settling was enhanced by adding polyaluminum chloride (PAC) as coagulant and hydrolyzed polyacryamide (HPAM) or cationic polyacrylamide (CPAM) as flocculant. At optimal dose, the particle settling ability with PAC and CPAM was better than that with PAC and HPAM. Particle size analysis showed that HPAM or CPAM with high molecular weight played an important role for enlarging the particle size. The experiments with simulated wastewater showed that particle settling by using HPAM deteriorated significantly compared to that by CPAM at high calcium ion. This study provides further understanding about the effect of high salinity and Ca2+ on solids formation, flocculant performance and particle settling. Meanwhile, the results are also helpful to develop novel flocculants used for high salinity wastewater.