Study on non-plane propagation characteristics of fracturing fractures in tight sandstone of Qiulin block under high geo-stress

Abstract

In order to study the propagation characteristics of hydraulic fracturing fractures in tight sandstone reservoirs in Qiulin block, Sichuan Basin, hydraulic fracturing of tight sandstone under high triaxial in-situ stress were carried out by using a large true triaxial fracturing physical experimental system. The fracture morphology and pump pressure curves under different in-situ stress, fracturing fluid types and displacement were obtained. The experimental results show that: (1) under high geo-stress conditions, the fracture morphology of tight sandstone after hydraulic fracturing is relatively simple, and complex fracture characteristics are less formed. The sedimentary characteristics and the development of internal natural fractures are the main control factors affecting the initiation and propagation of hydraulic fracturing fractures. (2) The characteristics of in-situ stress affect the fracture initiation and propagation direction. When the vertical in-situ stress is equal to the horizontal minimum principal stress, the horizontal fracturing fractures perpendicular to the vertical in-situ stress direction can be formed, and most of the fracturing fractures are non-plane propagation fractures. (3) When the low displacement slick water is used for fracturing, the fracturing fluid is easy to enter into the micro fractures inside the tight sandstone, which is helpful to open the original micro fractures, and the fracture morphology after fracturing is relatively complex; when the high displacement slick water or high viscosity linear gel is used for fracturing, the fractures with non-planar expansion are formed after fracturing. The research results can provide some technical support for the reservoir reconstruction of the second member of ES_2 formation in Qiulin block, Sichuan.