Hydrocarbon Accumulation Characteristics And Distribution Patterns In Deep And Shallow Basin In Kuqa Depression,Tarim Basin

A lot of hydrocarbon reservoirs have been detected in the deep tight reservoirs in Kuqa depression,however,the hydrocarbon accumulation conditions and characteristics in the deep basin are very different from those in shallow areas.Thus,the hydrocarbon exploration in the deep tight reservoirs has been delayed.This paper revealed the formation mechanism of hydrocarbon reservoirs in the deep and shallow basin based on the dissection of reservoir geological characteristics and accumulation dynamic process.Three types of reservoir and their discriminant criteria were established.On this basis,three hydrocarbon accumulation modes were established and hydrocarbon distribution pattern in two main exploration target strata of the Kuqa depression,the Cretaceous Bashijiqike Formation and Jurassic YangXia Formation,were clarified.The results showed that conventional reservoir was developed in shallow basin,whereas conventional tight reservoir and deep basin tight reservoir were developed in deep basin.Conventional reservoir has the geological characteristics of high point convergence,high point sealing,high porous concentration,and high pressure accumulation,and accumulation characteristics of source-resevoir separation,hydrocarbon driven by buoyancy in un-tight reservoir.Conventional tight reservoir has the geological characteristics of high point convergence,high point sealing,low porous concentration,and high pressure accumulation,and accumulation characteristics of source-resevoir separation,hydrocarbon injected before reservoir become tight,hydrocarbon driven by buoyancy during injection.Deep basin tight reservoir has the geological characteristics of low point convergence,low point sealing,low porous concentration,and low pressure accumulation,and accumulation characteristics of source-resevoir contiguous,hydrocarbon injected after reservoir become tight,buoyancy was limited during injection.Hydrocarbon accumulation process in the basin was controlled by the evolution process of fluid dynamic field.Freedom,limited,and constraint fluid dynamic field were developed in Kuqa depression.Affected by the complex evolutionary process of fluid dynamic field,conventional resources,conventional tight resources,and deep basin tight resources were developed in Cretaceous Bashijiqike Formation;conventional resources and deep basin tight resources were developed in Jurassic Yangxia Formation,which showed favorable exploration prospect.