塔里木盆地富满断控破碎体油藏储集类型特征与注水替油效果

Storage space types and water-flooding efficiency for fault-controlled fractured oil reservoirs in Fuman oilfield,Tarim Basin

塔里木盆地走滑断裂控制的超深油气藏是近年来中国油气勘探开发最重要领域之一,但目前该类型油藏的储集空间类型并不清楚,不同储集空间类型与注水效果关系不明确,严重制约了富满油田的高效开发。在充分分析野外露头、岩心、成像测井以及动态监测资料的基础上,系统剖析了断控破碎体的3种主要储集空间类型及其与注水效果的关系。提出了断控破碎体的概念,指出富满油田主要为断控破碎体油藏,研究结果表明:①断裂空腔型储集体主要分布在断裂带的核部,由断层滑动面产状变化引发内部体积调整形成了“空腔”型洞穴。埋藏条件下的储集空间相对较为封闭,内部孔隙空间较大,注水后原油置换率较高,部分油井动用储量的注水采收率可高达93%。②角砾间孔隙型储集体主要分布在断裂带的核部,由相邻的角砾相互支撑而形成角砾间不规则储集空间类型。该类储集体分布较为均匀,孔隙度中等,单位压降下的产液量较高,但是由于储集空间内部连接并不通畅,注水后置换率较低,需要研究探索构建立体结构井网来提高开发效果。③构造裂缝型储集体主要分布在断裂带的损伤带和过程带,在断层带的两侧和端部发育形成一定宽度的裂缝带。裂缝带周边也会发育少量孔隙,部分区域会形成一定的渗流优势通道,因此注入水的流失量较大,注水效果相对于断裂空腔型储集体较差。研究成果支撑了富满油田上产原油350×10^(4) t,可助推注水开发方案和提高采收率方案的优化,对同类型油藏高效开发具有重要的借鉴意义。

Ultra-deep hydrocarbon reservoirs in the Tarim Basin,governed by strike-slip faults,have become a pivotal target in China’s hydrocarbon exploration and exploitation efforts in recent years.However,the storage space types of these reservoirs,as well as their relationships with water-flooding efficiency,are yet to be clarified,presenting a significant challenge to the efficient development of the Fuman oilfield.Based on thorough analyses of outcrops,core samples,formation micro-imaging(FMI)logs,and dynamic monitoring data,we introduce the concept of fault-controlled fractured reservoir to refer to the those in the Fuman oilfield,and systematically explore the three major storage space types and their relationships with the water-flooding efficiency.Key findings are as follows:(1)Fault cavity-type reservoirs,predominantly found in the core of the fault zones,feature hollow cavities created by adjustments of internal special volume after multi-stage structural activities on the faults’sliding surfaces.The storage spaces of these reservoirs,relatively enclosed under burial conditions,are characterized by large pore volumes.This structural configuration enhances oil-water displacement efficiency,with some oil wells yielding a waterflooding recovery factor up to 93%of the petroleum reserves in development;(2)Inter-breccia pore-type reservoirs,also primarily distributed in the fault zones’core,feature inter-breccia irregular storage spaces formed by the mutual support of adjacent breccias.These reservoirs exhibit a relatively uniform distribution,moderate porosity,and high liquid yield per unit pressure drop.However,the poor internal connectivity for the storage spaces leads to a low oil replacement rate by water injection.Therefore,it is necessary to explore the construction of a three-dimensional well pattern to improve development efficiency.(3)Structural fracture-type reservoirs are primarily distributed in the damage and process zones of the fault zones,with fracture zones with certain widths developing along the fault zones’both sides and ends.In addition,a small number of pores are present around these fracture zones,with dominant seepage channels formed locally.This leads to a significant loss of injected water and,accordingly,lower oil displacement efficiency compared to the fault cavity-type.The study results can serve to support the production of 350×10^(4) tonnes in the Fuman oilfield.Furthermore,they prompt the optimization of schemes for waterflooding and enhanced oil recovery(EOR),having a significant referential value for the efficient exploitation of similar oil reservoirs.