The Dominant Factors of Hydrocarbon Accumulation in Qigu Formation in Zhong32 Wellblock, Junggar Basin

Based on the characteristics of strata, tectonics, sedimentary reservoir and fluid characteristics, the dominant factors of the hydrocarbon accumulation in Qigu Formation in Zhong32 wellblock in Junggar Basin are analyzed from the aspects of unconformity and faulty. The results show that Qigu Formation reservoir belongs to the type that would exist in the semi-weathering rock of Cretaceous-Jurassic unconformity in a fault block background. The model of hydrocarbon pool-forming is a secondary reservoir controlled by unconformity-fault, out of the source rock province from the late Jurassic to the Cretaceous unconformity. The unconformity-fault system of migration and accumulation is the primary system in the hydrocarbon migration and accumulation. The long-term weathering and erosion makes the reservoir quality much better. Though the Weathered Clay of Cretaceous-Jurassic unconformity is widespread development in Zhong32 wellblock, its sealing ability is poor, resulting in the leakage of light weight fractions of hydrocarbon and the formation of heavy oil reservoirs. Multistage tectonization and unconformity-fault migration-accumulation system are the main controlling factors for super heavy oil reservoirs in Qigu Formation.