Recognition And Study Of Structural Fractures In Shale Reservoirs

With the increasing demand for energy,more and more attention has been paid to the exploration and development of shale gas.Compared with conventional oil and gas reservoirs,shale gas reservoirs have different storage spaces and seepage characteristics,fractures in the mud shale develop differently from one to the other,and the filling materials in the fractures are different.These differences make it more difficult to identify and predict fractures.At the same time,it is impossible to fully identify fractures by a single research method.It is necessary to combine multiple methods for comparative research,to take advantage of various methods,and finally obtain more accurate results through comprehensive prediction research.This study relies on the "Research on Shale Structual Fractures in Jiaoshiba Block" project,based on a full understanding of the geological background of the study area,to observe fractures in the core of the Upper Ordovician Wufeng Formation and Lower Silurian Longmaxi Formation(the target interval of the study area),and then study the distribution of shale fractures from the logging and seismic aspects.In terms of logging fracture response,the conventional logging curve and FMI imaging logging technology are introduced.Through the actual logging curve and imaging logging to verify the reliability of the methods,the logging response of the fracture development section in the study area is determined through statistical analysis.Recognize that the target interval is dominated by low-angle cracks and few high-angle cracks.In terms of seismic detection of cracks,seismic attribute analysis techniques and seismic attributes sensitive to cracks are introduced,technical C3 coherence algorithm and ant tracking technology are introduced in detail.Methods of detecting cracks in the actual post-stack seismic data are applied,and then explore the extraction technique which is suitable for the sensitive attributes unique to the study area.The comparison test found that the ant tracking technology works best,especially the development of the cracks in the main body of the anticline of Jiaoshiba is portrayed clear.Combined with previous studies and analysis,it is recognized that the research area experienced multiple stages of tectonic movements like Indosinian,Yanshan and Himalayan Movement to form today's complex fault system,and also realized that the strength of tectonic deformation is one of the essential factors that cause fracture development.Combined with comprehensive analysis of seismic,logging,drilling and core data,it is concluded that the maximum principal stress direction of the tectonic stress field in the study area is near east-west direction;the fractures in the study area are mainly north-east direction,and north-west direction is supplementary;In the eastwest and north-south fracture zones of the study area,the productivity of a single well is low.According to the analysis of tectonic evolution,the northeast fractures are classified as the Late Yanshan period,and the northwest fractures are classified as the Himalayan period.At the same time,with the stress field of the sinistral rotation and compressive shearing,the east-west and south-north directions are classified as the late Yanshan-Early Himalayan period.And finally the main body of the anticline of Shijiaba was divided according to the fracture density and strike.