Development characteristics of shale fracture in Longmaxi Formation in southeasten Sichuan

Based on core data, a detailed identification was carried out on the shale fracture in Longmaxi Formation in southestern Sichuan. Statistics of core fracture basic parameters were done and the fracture density was calculated. A method was established which apply fracture characteristic parameters to determine the fracture development characteristics. Taking Yuye 1 well as an example, combined with the microscope observation of micro crack, macroscopic core crack, shale fracture and fracture density, a detailed description was carried out on the fracture development characteristics of the organic-enriched marine black shale in Longmaxi Formation. Also, the influencing factors of shale fracture development degree are studied, the relationship between shale fracture development characteristics and the rock brittleness mineral content was determined qualitatively or semi-quantitatively and the relationship between the fracture development degree of organic-enriched marine shale and the organic carbon content was analyzed. Results show that: (1) Shale with high content of quartz, feldspar, calcite, brittleness mineral and low content of clay is easy to produce fractures; (2) To some extent, the TOC has a positive correlation with the fracture development degree of organic-enriched marine shale. The higher the TOC, the larger the fracture density; (3) The fracture development degree can be divided into three categories according to the TOC: Poor, normal and good. ©, 2015, Science Press. All right reserved.