Study Of Fault System’s Characteristics And Its Reservoir-Controlling Function In The Western Margin Of Junggar Basin

There is great potential for oil and gas resources in Western Margin of Junggar Basin.In order to confirm the relationship between faults and hydrocarbon accumulation, the control roles of faults on hydrocarbon accumulation were systematically studied in this work, applying the theories and methods of petroleum geology, structural geology, geochemistry, basin analysis and statistics synthetically.From 2D and 3D seismic data, fault patterns and their formation mechanism were summarized, and fault activity was evaluated. The results show that the two phases of faults’ evolution are compression deformation from Carboniferous to Jurassic period and compressive-sheering inversion deformation from N1 t to Quaternary Period.Comprehensive utilization of drilling,logging, geochemistry, analysis, source rock and fluid inclusions data, the hydrocarbon generation period and hydrocarbon reservoir forming stages of Western Margin of Junggar Basin was confirmed by the technology of basin modeling, and the time effectiveness between hydrocarbon accumulation and fault activity was evaluated. The source rock’s generation and expulsion period of heavy crude is T2 to J2.The source rock’s generation and expulsion period of light oil is E to Q. The time effectiveness between hydrocarbon accumulation and fault activity was good: the hydrocarbon reservoir forming stages are T2 to J, E3 and N to Q. Oil-source correlation and reservoir forming period were controlled by the matched space-time effectiveness between two periods of fault activity and two periods of hydrocarbon generation evolutions.Combining the spatial distribution characteristics of fault, sand body and unconformity and evaluation of fault sealing, the matching relation in space of fault, sand body and unconformity was evaluated and the role of fault in oil and gas accumulation was confirmed: Hongche fault,Aika fault, the shallow faults and the blanket sand in N1s1 compose the Meshwork-carpet passage system which is good for oil gathering in N1 s, Hongche fault and Aika fault are oil-source faults, the shallow faults are adjusting faults;the deep faults match with relation unconformity and J sand body in space is good, the deep fault are sealing faults.According to comprehensive analysis, three styles of hydrocarbon accumulation model were established. One is “the Permian hydrocarbon source rocks + Hongche Fault+ the Unconformity between K and C, the the Unconformity between J and C,the sandbody in J + deep faults” early reservoir-controlling model,one is “the Permian hydrocarbon source rocks(+ Unconformity between K and C+ shallow faults)+ Hongche Fault+the blanket sand in N1s1, the Unconformity under N1 s base+ the thinning out zone of sand body in N1s1” late reservoir-controlling model, and another “the Jurassic hydrocarbon source rocks + Hongche Fault/Aika Fault + shallow faults + Lithologic trap in N1s” late reservoir-controlling model.