Development laws and controlling factors of natural fractures of Xujiahe Formation in Tongjiang area,northeastern Sichuan
The development laws of natural fractures in tight sandstone reservoirs have a significant impact on gas reservoir enrichment and single well productivity.Based on outcrops,cores,thin sections,geophysics and gas testing data,the laws and controlling factors of natural fractures in Xujiahe Formation of Upper Triassic in Tongjiang area were clarified,a geological model for fracture development was established,and the types and distribution range of sweet spots in gas reservoirs were proposed.The research shows that:(1)There are two types of natural fractures developed in the tight sandstone reservoir of Xujiahe Formation in Tongjiang area,namely tectonic fractures and non-tectonic fractures.(2)The optimal orientation of natural fractures is near south-north,and natural fractures are mainly middle-high angle fractures.(3)The degree of development of natural fractures is joint-controlled by factors such as lithology,rock mechanical layer thickness and tectonism.Siltstone is the dominant lithology for fracture development,and fault surfaces and fold cores are favorable parts for fracture development.(4)Combined with seismic prediction results,it is clarified that the fracture development belt less than 300 m away from the fault surface and less than 400 m away from the fold hinge surface is the fracture sweet spot area of the tight reservoir of Xujiahe Formation.The research result can provide a basis for reserve evaluation and well loction deployment in this area.
tight sandstonenatural fracturescontrolling factorsXujiahe FormationTongjiang area
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