Influence of Present-Day In Situ Stress on Deep and Ultradeep Carbonate Reservoir Distribution: A Case Study from the Upper Member of the Yingshan Formation in the S Area of the Tahe Oilfield, Tarim Basin, Northwestern China.

Recently, in addition to petrophysical properties, the present-day in situ stress (PDIS) is also considered as one of the controlling factors for the highly heterogeneous deep and ultradeep carbonate reservoirs. However, the specific relationship between PDIS and the distribution of carbonate reservoirs remains unclear. This situation restricts our understanding of the distribution law of deep carbonate reservoirs and the accurate prediction of favorable distribution areas. This paper focuses on unraveling the orientation, magnitude, and distribution law of PDIS and its influence on the distribution of deep carbonate reservoirs in the Upper Member of the Yingshan Formation within the S region of the Tahe Oilfield. By leveraging image logging, conventional logging, the combined spring model, and data dissection from a variety of geological experiments, drilling operations, and reservoir engineering undertakings, it is endeavored to shed light on these aspects. The results demonstrate that the maximum horizontal primary stress (Sh max), minimum horizontal primary stress (Sh min), and stress difference (D s) are the key factors controlling the distribution of deep carbonate reservoirs in the Upper Member of the Yingshan Formation in the study area. Specifically, the reservoir thickness, showing a negative correlation with Sh max and D s, is generally high with a value more than 14 m in the areas where Sh max and D s are less than 157 and 61 MPa, respectively. Reservoir porosity displays a positive correlation with Sh min but a negative correlation with Sh max and D s. It is commonly high with a value more than 5% in the areas where Sh min is larger than 96 MPa and Sh max and D s are less than 157 and 61 MPa, respectively. The thickness of strata with fracture development exhibits a positive correlation with Sh max and D s and a relatively strong negative correlation with Sh min. It is commonly high with a value more than 5 m in the areas where Sh max and D s are greater than 157 and 62 MPa, respectively, and Sh min is less than 95 MPa. Regions where Sh max is less than 157 MPa, D s is less than 61 MPa, and Sh min is greater than 96 MPa should be the primary choices for selecting favorable areas of deep carbonate reservoir distribution in the study area. The research results can not only benefit the exploration for the distribution law of deep and ultradeep marine carbonate reservoirs but also provide technical support for the prediction and optimization of favorable areas for deep oil and gas exploration.