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Velocity sensitivity refers to the possibility and degree of reservoir permeability decline caused by the migration of various particles in the reservoir rock due to the increase in fluid flow velocity and the blockage of pore channels. To improve the development results of M reservoir in Karamay Oil field, two reservoir cores were selected to carry out velocity sensitivity experiments. The permeability of No. 1 core decreases obviously when the flow rate is greater than 0.04 mL/min. Therefore, it can be considered that the injection rate of velocity sensitivity is between 0.04 and 0.06 mL/min, and the displacement rate should be less than 0.04 mL/min in the core displacement experiment. When the flow rate is greater than 0.5 mL/min, the permeability of No. 2 core decreases significantly. This is mainly due to the high permeability and critical velocity of No. 2 core. The study can provide a basis for the selection of displacement velocity in core displacement experiments, and also provide a reference for the determination of reasonable injection-production velocity in actual production.

Cross-borehole electrical resistivity tomography (CHERT) technology has been implemented in field-scale CCS/CCUS (carbon capture and storage/carbon capture, utilization and storage) projects. It is highly desirable to investigate how to optimize the design of the ERT electrode arrays and corresponding working schemes for both laboratory experiments and field applications. A CHERT system was developed for laboratory experiments of CO2 geological storage applications. An optimization method was established for optimizing the structure of electrode arrays and corresponding working schemes. The developed CHERT system was calibrated systematically to determine the measurement range and accuracy of electrical impedance. Laboratory experiments were designed and implemented to validate the performance of the developed CHERT system. It has been illustrated that: (1) It is an essential step to optimize the structure of electrode arrays and corresponding working schemes of CHERT according to the real application background. The optimization method based on finite-element modelling provides an effective means for designing a field-scale CHERT system. (2) The quality of the images inverted from the CHERT data is highly dependent on the working schemes and specific modes, which is closely related to the size of the data sets used for the inversion. The AM-BN scheme is recommended due to the better uniformity of the resultant sensitivity field and application to larger borehole spacing. (3) Based on the calibration, the measurement range of the developed CHERT system can be determined as 100 Ω to 4.5 kΩ with an error limit of 1.5%. The maximum relative errors of the impedance magnitude and phase angle are 5.0% and 7.0%, respectively. Based on the test results the location of the CO2-bearing objects can be identified accurately. The shapes of the tested objects present distortion to some extent, but this can be alleviated by selecting working modes with a larger size of data set. [ABSTRACT FROM AUTHOR]

The goals of carbon neutrality and peak carbon have officially been proposed; consequently, carbon dioxide utilization and sequestration technology are now in the limelight. Injecting carbon dioxide into reservoirs and solidifying and sequestering it in the form of carbonates after a series of geochemical reactions not only reduces carbon emissions but also prevents carbon dioxide from leaking out of the formation. Carbon dioxide mineralization sequestration, which has good stability, has been considered the best choice for large-scale underground CO2 sequestration. To provide a comprehensive exploration of the research and prospective advancements in CO2 mineralization sequestration within Chinese oil and gas reservoirs, this paper undertakes a thorough review of the mechanisms involved in CO2 mineralization and sequestration. Special attention is given to the advancing front of carbon dioxide mineralization, which is driven by microbial metabolic activities and the presence of carbonic anhydrase within oil and gas reservoirs. The paper presents an in-depth analysis of the catalytic mechanisms, site locations, and structural attributes of carbonic anhydrase that are crucial to the mineralization processes of carbon dioxide. Particular emphasis is placed on delineating the pivotal role of this enzyme in the catalysis of carbon dioxide hydration and the promotion of carbonate mineralization and, ultimately, in the facilitation of efficient, stable sequestration. [ABSTRACT FROM AUTHOR]

CO2 sequestration in saline aquifers is one of the most potential sequestration modes, and saline aquifers are ideal sites for CO2 geological sequestration. After CO2 is injected into a saline aquifer, it will have a long-term complex geochemical reaction with the formation of minerals and water, and the minerals will undergo multiple reactions such as dissolution and reprecipitation. Therefore, an in-depth study of the geochemical reaction mechanisms between CO2 and formation minerals is of great significance to the accurate calculation and prediction of CO2 storage volume and the safety evaluation of long-term CO2 sequestration. In China, continental saline aquifers are widely distributed, whose mineral compositions and texture maturity are markedly different from those of the marine sedimentary basins in North America, and their stratigraphic environments are more complicated. The studies on the CO2–water–rock (mineral) still have many research gaps or insufficiencies, and there is no report on the dissolution mechanisms of individual minerals in the reaction. Taking one certain block of Daqing Oilfield, which is a typical continental deposit in China, as an example, we analyze the dissolution laws and four types of typical continental deposited minerals under the effect of CO2 and the change features of ionic compositions and pH of the formation water in the process of geochemical reaction. The research results indicate that CO2 has different dissolution degrees for the four types of minerals, among which, feldspar, as the main mineral in continental sedimentary formations, has the lowest dissolution rate. Furthermore, in terms of the water type (Na+-enriched NaHCO3) of the saline aquifer in the deep part of the continental deposit, feldspar can precipitate into the secondary minerals represented by dawsonite in the later stage, which can act as the potential minerals of carbon fixation to increase the CO2 mineralization storage volume in continental deposited saline aquifers. [ABSTRACT FROM AUTHOR]

Passive icephobic surfaces have been extensively studied by researchers due to their advantages of delaying icing time and reducing ice adhesion strength. However, icephobic materials with petroleum‐based resources and toxic fluorine‐containing chemicals, as one of the excellent icephobic materials, are very unfavorable for resource conservation and environmental protection. In this study, we report fluorine‐free, highly transparent, chemically durable and low ice adhesion icephobic coatings prepared by glycerol triglycidyl ether (GTE) derived from natural glycerin and bis(3‐aminopropyl) terminated polydimethylsiloxane (PDMS) via one‐pot method. On the one hand, PDMS with multiple methyl groups and two amine groups acts as a hydrophobic modifier to modulate the surface energy of the coatings, and also acts as a structure modifier to modulate the mechanical properties of the coatings, which allow us to design and synthesis the coating with excellent deicing performance (ice adhesion strength can reach about 16 kPa). On the other hand, GTE with multiple epoxy groups works as cross‐linker to endow the coatings with good cross‐linked networks, so that the coatings showed good durability after being subjected to different temperature treatment and different solution treatments. In additional, the transmittance of the coating is above 91.4%, which is expected to be applied to windows and sensors. [ABSTRACT FROM AUTHOR]

Flue gas flooding has been applied in many oilfields for its accessibility and low cost. However, the problem of gas channeling during flue gas flooding is significantly more serious due to reservoir heterogeneity and gravity override, and the traditional profile control agent is inapplicable because of flue gas acidity. In order to solve this challenge, a novel acidic nanoparticle was presented first; then, the profile control performance of both water slugs and this novel nanoparticle for flue gas flooding in heterogeneous reservoirs was studied using core samples with different rhythms. The results show that the stability of the acidic nanoparticles is good, and the viscosity of the nanoparticle solution increases as the pH decreases, which is suitable for acidic flue gas flooding. The oil recovery of flue gas flooding in a positive rhythm core is 5–10% greater than that in a reverse rhythm core. The water slug can improve oil recovery by 5% in the reverse rhythm core, and oil recovery was less than 2% in the positive rhythm core. The effect of a nanoparticle slug is much better than the water slug. It improved the oil recovery by 10% in the positive rhythm core by continuing flue gas flooding after nanoparticle slug treatment, which was more than the 20% in the reverse rhythm core. The ultimate oil recovery of both positive and reverse-rhythm cores by acidic nanoparticle slug treatment was around 50%, which was 10% greater than the water slug treatment. The conformance control using acidic nanoparticles is more suitable for reverse rhythm formation due to its plugging capacity, deformation characteristic, and viscosity increment in an acidic environment. This research demonstrated that these novel acidic nanoparticles could be effectively applied to conformance control during flue gas flooding in heterogeneous reservoirs. [ABSTRACT FROM AUTHOR]

Because of the growing demand for energy, oil extraction under complicated geological conditions is increasing. Herein, oil displacement by CO2 in wedge-shaped pores was investigated by molecular dynamics simulation. The results showed that, for both single and double wedge-shaped models, pore Ⅱ (pore size from 3 to 8 nm) exhibited a better CO2 flooding ability than pore Ⅰ (pore size from 8 to 3 nm). Compared with slit-shaped pores (3 and 8 nm), the overall oil displacement efficiency followed the sequence of 8 nm > double pore Ⅱ > single pore Ⅱ > 3 nm > double pore Ⅰ > single pore Ⅰ, which confirmed that the exits of the wedge-shaped pores had determinant effects on CO2 enhanced oil recovery over their entrances. "Oil/CO2 inter-pore migration" and "siphoning" phenomena occurred in wedge-shaped double pores by comparing the volumes of oil/CO2 and the center of mass. The results of the interaction and radial distribution function analyses indicate that the wide inlet and outlet had a larger CO2–oil contact surface, better phase miscibility, higher interaction, and faster displacement. These findings clarify the CO2 flooding mechanisms in wedge-shaped pores and provide a scientific basis for the practical applications of CO2 flooding. [ABSTRACT FROM AUTHOR]

In view of the problems of low matrix permeability and low oil recovery in shale reservoirs, CO2 huff and puff technology is considered as an effective method to develop shale oil reservoirs. However, the production behaviors of actual shale reservoirs cannot be reproduced and the EOR potentials cannot be evaluated directly by scaled models in the laboratory. Conventional CO2 huff and puff has problems such as early gas breakthrough and gas channeling leading to inefficient development. In this article, with the help of a three-dimensional experimental simulation apparatus, a new method of CO2 huff and puff with a horizontal well assisted by pumping production and water injection disturbance is developed. The dynamic characteristic, pressure field distribution of soaking and the enhanced oil recovery effect are comprehensively evaluated. The results show that the soaking stage of CO2 huff and puff can be divided into three stages: differential pressure driving, diffusion driving and dissolution driving. According to the pressure field distribution, after water injection disturbance, the fluctuation boundary and distribution of pressure becomes more stable and uniform and the sweep rate is greatly improved. Water injection disturbance realizes the combination of CO2 injection energy enhancement and water injection energy enhancement and the CO2 injection utilization rate is improved. It has the dual effect of stratum energy increase and economic benefit. The new huff and puff method can increase the oil recovery rate by 7.18% and increase the oil–gas replacement rate to 1.2728, which confirms the potential of horizontal well pumping production and water injection disturbance-assisted CO2 huff and puff technology to improve oil recovery. [ABSTRACT FROM AUTHOR]