Selecting the most suitable enhanced oil recovery (EOR) technique remains challenging due to severe class imbalance in historical datasets and the limitations of traditional screening criteria. To address data imbalance while preserving domain knowledge, this study proposes a novel machine learning framework that incorporates domain-informed synthetic data generation strictly constrained by established EOR screening criteria. An initial dataset of 583 documented EOR projects was compiled from field reports and public databases. After rigorous cleaning, 575 valid samples were retained and subsequently augmented to 760 balanced instances (class sizes ranging from 60–110 samples per class). T... More >

Deep geothermal resources are environmentally friendly and represent a highly competitive form of clean energy. However, low rock-breaking energy combined with high rock strength results in a low rate of penetration (ROP), which significantly restricts the efficient utilization of geothermal resources. Previous studies have shown that rock failure is primarily caused by shear stress. Therefore, this paper aims to enhance the shear stress level by increasing the impact load and releasing the confining pressure, thereby improving the ROP. Specifically, the rock-breaking efficiency under the coupling of impact load and confining pressure releasing is analyzed to reveal the influence of confinin... More >

The low concentration and poor reservoir properties of natural hydrogen suggest that reservoir stimulation measures such as fracturing is required for its efficient development. Nevertheless, the presence of reservoir imperfections, including hard and soft cores, can significantly affect fracture behavior during the fracturing operations. Moreover, there is currently a lack of relevant simulation and experimental studies addressing these effects. In the present work, the effects and mechanisms of hard cores on fracture propagation in natural hydrogen reservoirs in the Songliao basin were numerically simulated. In addition, various factors affecting propagation behavior of fracture were also... More >

The flow resistance of displacement fluids within reservoir fractures directly influences oil recovery efficiency and sweep efficiency, thereby exerting a substantial impact on reservoir recovery and overall oilfield production. To address the significant flow resistance of contemporary displacement fluids, this study developed a multi-performance evaluation apparatus capable of simultaneously measuring fluid viscosity, flow resistance, and displacement efficiency. The effects of various reservoir parameters and fluid compositions on flow resistance and sweep area were systematically analyzed. Elevated reservoir temperatures clearly reduce fluid flow resistance within fractures, allowing dis... More >

Heavy oil reservoirs have become an important potential for alleviating energy shortages and supporting economic development. This investigation aims to explore the influence of a nano heavy oil viscosity reducer and reservoir characteristics on crude oil viscosity and flow rate during the underground extraction process, and to reveal the viscosity reduction mechanism of reservoir crude oil. The results indicate that the prepared nano viscosity reducer can significantly weaken oil viscosity compared with the commercial viscosity reducer. Moreover, the nano viscosity reducer NVR (acting as a catalyst) achieves a much higher viscosity reduction performance than the commercial viscosity reducer... More >

The low temperatures in the deepwater area are associated with a high risk of hydrate formation and flowline blockages in the wellbore and pipelines during the long-term development of gas reservoirs. The occurrence of this risk is required to be prevented and controlled to facilitate the safe and efficient development of offshore gas reservoirs. In this study, a numerical model was developed and solved to calculate the temperature and pressure distributions within wellbore and gathering system, and its applicability was evaluated. The comparison with experimental results verifies that the model is appropriate for predicting temperature and pressure distributions in the wellbore and gatherin... More >

Low fracturing efficiency and high permeability filtration present substantial challenges during the fracturing development of coalbed methane (CBM), significantly hindering its efficient exploitation. In this study, a cross-linker featuring specific polar functional groups on its side chains was synthesized, and a multi-functional coupling evaluation apparatus was developed to systematically investigate the performance characteristics of water-based fracturing fluids. Furthermore, molecular dynamics simulations were employed to elucidate the microscopic mechanisms by which the modified cross-linkers and various external factors influence CBM extraction efficiency. The results indicated that... More >

The depleted gas reservoirs can serve not only as sites for CO$_2$ sequestration but also as potential spaces for hydrogen storage. However, this process remains insufficiently investigated and thus cannot offer reliable technical support for the injection operations. In this study, a mathematical model for simulating hydrogen storage in depleted gas reservoirs was developed and numerically solved. Meanwhile, the applicability was then verified through comparison with results from previous studies. Based on this model, a detailed analysis was performed to investigate the evolution of key parameters under specific injection conditions. Finally, the effects of various factors on parameters suc... More >