大北地区巴什基奇克组致密砂岩气储层定量评价

摘要

充分利用岩心、薄片和钻测井等资料，对大北地区巴什基奇克组致密砂岩气储层的沉积相、成岩相和裂缝相特征进行研究。通过沉积微相、成岩相、裂缝相与物性分析或产能的标定与拟合从而分别形成各相的定量表征参数，再通过加权平均的方法建立岩石物理相的定量划分标准。最后对大北202等井储层岩石物理相进行定量划分。研究结果表明：巴什基奇克组储层沉积微相主要有扇三角洲前缘水下分流河道、河口坝和分流间湾以及辫状河三角洲前缘水下分流河道、河口坝和分流间湾6种；根据成岩作用类型和强度并结合成岩综合系数的计算可将储层划分为中等压实中等胶结、中等压实弱胶结、微裂缝和中等压实溶解共4种不同成岩相；裂缝相则以高角度斜交缝和网状缝相为主。在此基础上通过三者的叠加与复合对储层岩石物理相进行分类命名，划分出辫状河三角洲河口坝—中等压实溶解—网状缝相等多种不同的岩石物理相；气层均对应于有利的岩石物理相带，岩石物理相指数大于4的层段即可解释为该致密砂岩储层中的甜点发育带。基于岩石物理相划分是开展此类致密砂岩气藏储层成因机理分析乃至定量评价的有效途径。%The sedimentary micro-facies, diagenetic facies and fracture facies of tight gas sandstone reservoirs of Lower Cretaceous Bashijiqike Formation in Dabei area were studied by making full use of core observation, thin sections, logging and drilling data. By analysis of the sedimentary micro-facies, diagenetic facies and fracture facies, actual property analysis results and gas testing results, the quantitative characterization method of each facies was formed by the method of weighting average in this way, and the weighted value for sedimentary micro-facies, diagenetic facies and fracture facies was given considering the three facies’ properties and gas productivity of Bashijiqike formation tight gas sandstone reservoirs,so the quantitative division and characterization standard of reservoir petrophysical facies could be built up in this way. The Well Dabei 202 was chosen to verify the effectiveness of the method. Firstly, the sedimentary micro-facies, diagenetic facies and fracture facies of Bashijiqike Formation in this well were divided respectively, and then the petrophysical facies were divided and the quantitative characterization parameter were calculated. The results show that the Bashijiqike formation occurred in the sedimentary facies zone of fan delta to braided delta front subfacies, of which the sedimentary micro-facies can be divided into underwater distributary channel,mouth bar and underwater distributary bay. The diagenetic facies of Bashijiqike formation can be divided into 4 types, i.e. middle compaction middle cementation, middle compaction weak cementation, middle compaction corrosion and micro-fracture diagenetic facies.While the fracture facies of Bashijiqike formation are mainly composed of network fracture, high-angle fracture and low angle fracture together with horizontal fracture appeared in local layers. Then the petrophysical facies can be divided through the superimpositions and coupling of the sedimentary micro-facies, diagenetic facies and tectonic facies, and many types of petrophysical facies of Bashijiqike formation such as braided delta front mouth bar-middle compaction corrosion-network fracture are divided in this way. The gas reservoirs with high productivity are mainly corresponded to the favorable petrophysical facies. The layer with petrophysical facies parameter higher than 4 can be interpreted as the development zones of sweet spots. Petrophysical facies control the heterogeneity and oil-gas-bearing possibility of tight gas sandstone reservoirs on the microscopic scales, and the method to classify reservoir based on the division of petrophysical facies is an efficient way to revelation of reservoir genesis mechanism and quantitative evaluation of tight gas sandstone reservoirs.