Permafrost is typical temperature-sensitive sediment, and geo-mechanical issues such as wellbore collapse and sand production are prone to occur during the oil and gas development. Therefore, it is crucial to elucidate the patterns and mechanisms of wellbore instability throughout the drilling process and to develop/propose effective control strategies. In this study, based on sensitivity analysis of wellbore stability, a method for determining the safe windows of drilling fluid temperature, density, and salinity was proposed, along with corresponding measures for preventing wellbore collapse. The investigation results indicate that the collapse of sediments around the wellbore was primarily... More >

Hydrocarbon prospectivity in fold-and-thrust belts remains inherently uncertain due to the combined effects of structural complexity and heterogeneous reservoir properties. The Eastern Potwar region of Pakistan, characterized by imbricate thrust systems, anticlines, and synclines, represents a typical example where conventional approaches often fail to adequately constrain reservoir quality. This study integrates seismic interpretation with rock physics modeling to evaluate the hydrocarbon potential of the Missakeswal area. Seismic analysis delineates the structural framework controlling trap development, while rock physics modeling of well log data provides quantitative constraints on litho... More >

This study addresses fracturing performance evaluation during shale oil well flowback by developing a seepage flowback mathematical model and a water-phase evaluation framework. A method calculating effective fracture pore volume via flowback water production data is proposed. Using Well H flowback records, variable-production log-log well test plots and RNP-tm diagnostic charts were constructed for time-dependent fracturing effectiveness quantification. Key findings include: (1) Initial maximum cumulative water production derived from Arps harmonic decline model shows a semilogarithmic relationship between daily/cumulative water output; (2) Unit slope in fracturing fluid flowback indicates... More >

Extended-reach horizontal wells in continental shale formations of the Fuxing Block, southeastern Sichuan Basin, face prominent challenges, including drag and torque exceeding 50 metric tons and difficulties in weight-on-bit (WOB) transfer. Continental shale is characterized by high porosity, high permeability, distinct amphiphilic properties, and rapid performance degradation of oil-based drilling fluids (OBDF). These features lead to the formation of thick filter cakes and compacted cuttings beds, which further exacerbate abnormal drag. Existing research often focuses on single technical aspects, lacking integrated, full-cycle multi-factor coupling analysis. Based on field data from 14 dri... More >

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 >