Fracture characteristics and gas-bearing effects in Dalong Formation in complex tectonic zones:A case study of Hefeng area in western Hubei
The exploration potential of shale gas in the Permian Dalong Formation in the western Hubei is great,while the characteristics of fractures under the complex structural background have an important impact on the enrichment and preservation of shale gas.Utilizing both of core data and logging data from existed wells in the Hefeng area of western Hu-bei,the differences in fracture types and characteristic parameters of Permian Dalong Formation shale were compared sys-tematically,as well as the development characteristics,main controlling factors,and their impact on gas content of Dalong Formation shale fractures.The results show that the study area has a rich variety of fracture types,including shear frac-tures,tensile fractures,tension shear composite fractures,and network fractures,and the types of single well fractures at different structural locations vary greatly.The controlling factors for fracture development are structure and lithology.When the structure is relatively stable,the content of brittle minerals is high,and fractures are more developed.However,when faults develop,the degree of fracture development is inversely proportional to the distance from the structure.Frac-tures have a dual impact on the preservation of shale gas in the Dalong Formation.Fracture in structurally unstable areas have a destructive effect on shale gas preservation,while in structurally relatively stable areas,fracture have a certain a-bility to expand storage space when the material foundation is poor,and directly become escape channels when the materi-al foundation is good.
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