中国陆相致密油形成条件、富集规律与资源潜力

Forming conditions,enrichment regularities and resource potentials of continental tight oil in China

基于对中国陆上不同类型典型致密油田进行解剖,通过分析烃源岩、储层和原油样品,运用二维充注物理模拟、三维格子玻尔兹曼数值模拟等技术方法,系统研究和揭示了中国陆相湖盆致密油的形成条件、富集因素与资源潜力。①致密油的形成受控于盆地/坳(凹)陷中心及近邻斜坡环境、规模优质成熟生油岩、(近)湖盆中心区域大范围分布的有利储集体及以微米—纳米级孔喉为主的各类致密储层、"源-储"最佳空间配置、适宜的"温度—压力—流体"场5个地质条件,其中,"源、储、配"是致密油形成的3个关键条件。②陆相湖盆致密油富集主要受"烃源品质—断裂体系—储聚体系"3大系统要素控制,其中,中—高生、排烃量和较高热演化程度的优质源岩是致密油富集高产的先决要素,断裂和裂缝显著改善致密油输导效率、储集空间和聚集规模,储集层的孔喉大小及其连通性和组构非均质性显著影响致密油的分异和局部富集。③根据资源丰度开展分级评价,划分出三级资源区;采用小面元容积法计算致密油地质资源量,采用最终可采资源量(EUR)类比法求取相似刻度区的可采系数,进而与地质资源量相乘得出可采资源量。研究成果可为致密油富集区及"甜点"评价优选提供理论技术支撑。

Based on analyzing different types of typical continental tight oil fields in China,as well as source rock,reservoir,and crude oil samples,and using the techniques such as 2D charging physical modeling experiment and 3D lattice Boltzmann numerical simulation,this paper systematically studies and reveals the forming conditions,main enrichment controlling factors,and resource potentials of tight oil in the continental lacustrine basin of China as below.(1)The formation of tight oil is controlled by the geological conditions of the center of basin/depression and its adjacent slope environment,high-quality mature source rocks,favorable reservoir bodies and various types of tight reservoirs dominated by micro-and nano-scale pore throats distributed over a large area in or near the central area of the lacustrine basin,the best spatial collocation of source and reservoir,and the suitable temperature-pressure-fluid field.Among them,source,reservoir,and collocation are key conditions for the formation of tight oil.(2)The tight oil enrichment in the continental lacustrine basin are mainly controlled by hydrocarbon source quality,fracture system,hydrocarbon storage and accumulation system,among which high-quality source rocks with medium to high intensity hydrocarbon generation and expulsion as well as high thermal evolution are the prerequisites for the enrichment and high yield of tight oil.Faults and fractures can significantly improve the transport efficiency,reservoir space and accumulation scale of tight oil.The size and connectivity of the reservoir pore throat and reservoir composition heterogeneity have significant effects on the differentiation and local enrichment of tight oil.(3)Based on a grading evaluation according to resource abundance,the study area is divided into three levels of resource zones;the small-bin volumetric method is used to calculate the amount of tight oil geological resources,and the estimated ultimate recovery(EUR)analogy method is applied to obtain the recoverable coefficients of similar scale areas,which further multiplies with the amounts of geological resources to get the potential recoverable resources.The research results provide theoretical and technical support for the evaluation and optimization of tight oil enrichment areas and sweet spots.