孔洞型碳酸盐岩储层压裂裂缝转向扩展特征研究

Study on Propagation and Diversion Characteristics of Hydraulic Fractures in Vuggy Carbonate Reservoirs

吴峙颖 胡亚斐 蒋廷学 张保平 姚奕明 董宁

WU Zhiying HU Yafei JIANG Tingxue ZHANG Baoping YAO Yiming DONG Ning

页岩油气富集机理与有效开发国家重点实验室, 北京 102206 中石化石油工程技术研究院有限公司, 北京 102206 中国石油勘探开发研究院, 北京 100083 天津昆仑燃气有限公司, 天津 300353

State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing, 102206, China Sinopec Research Institute of Petroleum Engineering Co., Ltd., Beijing, 102206, China Research Institute of Petroleum Exploration & Development, Beijing, 100083, China Tianjin Kunlun Gas Co., Ltd., Tianjin, 300353, China

针对孔洞型碳酸盐岩储层改造产生的水力裂缝扩展规律复杂、不一定沿预设路径扩展的问题，基于碳酸盐岩储层孔洞体特征，制备了含孔洞体的碳酸盐岩试样；利用真三轴水力压裂试验结果，分析了不同水平主应力差异下孔洞体对水力裂缝扩展的干扰作用；并利用扩展有限元数值方法，分析了影响孔洞型碳酸盐岩储层水力裂缝扩展及扩展路径的因素。研究结果表明，水平主应力差异系数不大于0.15时，水力裂缝遇到孔洞体后产生非平面扩展，且水平主应力差越小，转向扩展距离越大，裂缝形态越复杂；水平主应力差异系数大于0.15、小于0.36时，水力裂缝会克服孔洞体的应力集中进行平面扩展，但遇到孔洞体后会被孔洞体捕捉，无法穿过孔洞体继续扩展；水平主应力差异系数不小于0.36时，水力裂缝会克服孔洞体的应力集中进行平面扩展，且遇到孔洞体后会直接穿过孔洞体继续扩展；随着水平主应力差增大，破裂压力逐渐降低。研究结果可为孔洞型碳酸盐岩储层压裂设计提供指导。

Hydraulic fractures generated in the stimulation of vuggy carbonate reservoirs feature complex propagation as they do not necessarily propagate along the prospected path. In view of this, vuggy carbonate rock samples were prepared based on the analysis of the vuggy characteristics of carbonate reservoirs. With test results of true triaxial hydraulic fracturing, the interference of cavities in the propagation of hydraulic fractures under different horizontal principal stress differences was investigated. Moreover, the extended numerical finite element method was used to analyze the factors affecting the propagation of hydraulic fractures in vuggy carbonate reservoirs and their propagation paths. The results revealed that non-planar propagation would occur when hydraulic fractures encountered cavities when the difference coefficient of the horizontal principal stress was below 0.15, and smaller horizontal principal stress was accompanied by a larger diversion propagation distance and more complex fracture pattern. When the coefficient was between 0.15 and 0.36, hydraulic fractures would overcome the stress concentration of cavities for planar propagation, but they would be captured by cavities encountered along the propagation path. When the coefficient was no less than 0.36, hydraulic fractures would overcome the stress concentration of cavities and penetrate cavities for planar propagation. In addition, the fracturing pressure would decrease as the stress difference increased. The research results can provide a reference for hydraulic fracturing design for vuggy carbonate reservoirs.

国家重点研发计划子课题“中东部深层高温地热系统分析与热储改造方法”（编号：2021YFA0716004）资助

https://doi.org/10.11911/syztjs.2022084