Research on the Influence of Stress Field Variations on Reservoir Stimulation Under Complex Structural Conditions in the Yingxiongling Shale Oil Reservoir

Continental shale oil reservoirs in China hold significant development potential. However, the efficient development of shale oil is challenged by significant changes in the stress field due to complex geological structures, which in turn affect the strategies and effectiveness of hydraulic fracturing operations. This paper, based on the integrated concept of geological engineering, focuses on the Yingxiongling shale oil formation in the Qaidam Basin. Through analysis of well logging data and microseismic monitoring techniques, the complex geological structures in typical regions are described. The influence of complex geological structures such as faults and natural fractures on stress field changes is analyzed. Numerical simulation methods are employed to study the countermeasures of reservoir stimulation under complex geological conditions. The results indicate that the stress field of the reservoir is influenced by the coupling effects of faults, natural fractures, and artificial fractures. Faults can deflect the in-situ stress of nearby reservoirs, and the characteristics of the in-situ stress vary at different depths and in different regions. During the expansion of artificial fractures, natural fractures in the near-wellbore zone can communicate with artificial fractures, while natural fractures in the far-wellbore zone can be opened by stress conduction, thereby altering the stress field around natural fractures. The dynamic expansion of artificial fractures leads to inter-segment interference and inter-well interference, thus affecting the reservoir stress field. Measures such as avoiding intersections should be taken in areas with developed natural fractures near the wellbore to prevent communication between natural fractures and artificial fractures. In areas with developed natural fractures far from the wellbore, the pumping rate should be reduced to prevent the opening of natural fractures and changes in the reservoir stress field, thereby affecting the effectiveness of reservoir stimulation. The results of this paper can support the development of oil and gas in complex structural formations.