Research On Hydrocarbon Accumulation Of Different Structural Belt The Pre-jurassic Strata In The Tainan Depression, Tuha Basin

Bassed on 3D seismic data of Tainan sag, field geological features analysis and physical simulation experiment, this paper established triple complex tectonic style of nappe footwall tectonic geological model of the Flaming Mountains fault wih the application of the theory of fault related folds and well-log and seismic data. Meanwhile, the basic structural pattern, the types and distribution of structural styles are determined according to the development characteristics. As a result, this paper studied period and evolution of structural activity and fault system.There are five kinds of structural zone(fault-nose structural zone at footwall of antithetic fault, Back thrusting anticline structural zone, fault-anticline structural zone at the single thrust fault, composite structural zone between back thrust anticline and unconformity and fault-anticline structural zone for stratigraphic inversion) controlling the distribution of oil and gas in Tainan depression according to the match between trap in the reservoir period and transporting system, associated with reservoir research and accumulation factor. Four of above controlled the distribution of original hydrocarbon reservoir and oil and gas enrichment zone of formation reverse adjustment controlled secondary hydrocarbon reservoir. The main controlling factors of hydrocarbon accumulation are determined:(1) the effective match between trap and transporting system controlled the distribution of hydrocarbon enrichment zone;(2) the effective match between cap rock and fault controlled the layer of hydrocarbon accumulation. Controlled by Lubei fault, part of hydrocarbon in Permian System was carried vertically to Triassic System;(3) the effective match between fault-unconformity-fan controlled the hydrocarbon accumulation area. There are mainly traps of fault nose, faulted anticline, anticline-unconformity and lithologic updip pinchout which sealed by regional cap rock of Wutonggou Formatin vertically. Juxtaposition is in the lateral of traps related faults and unconformity weathered clay layer has sealing ability. There are mainly faulted anticline traps sealed by cap rock of Kelamayi Formation and juxtaposition in lateral;(4) Fault lateral sealing ability controlled the difference of oil and water distribution. The reservoir is full of cataclastic deformation zone which has sealing ability.According to the theory of fault controlling accumulation, there are 5 kinds of reservoir modes with the analysis of the hydrocarbon accumulation study and the factors of controlling oil accumulation:(1) The reservoir mode of antithetic fault sealing at the limb of anticline, which is represented by the Flaming Mountains fault-step zone(Yingyeer Area) and the slope zone of the north of Flaming Mountains;(2) The reservoir mode of fault-unconformity sealing in the updip direction of anticline which is represented by Flaming Mountains fault-horst zone;(3) The reservoir mode of lithologic updip pinchout at the limb of anticline,which is represented by Lukeqin fault-horst zone;(4) The reservoir mode of anticline controlled by fault which is represented by Permian oil reservoir of Flaming Mountains fault-step zone(Yubei Area);(5) The secondary reservoir mode of formation reverse adjustment- fault sealing which is represented by Triassic oil reservoir of Flaming Mountains fault-step zone(Yubei Area).