流花11-1油田礁灰岩油藏沉积-成岩演化模式

南海流花11-1油田发育生物礁、生物滩两种沉积相类型,并可细分为珊瑚藻礁、珊瑚礁、珊瑚藻-珊瑚礁、有孔虫滩、生物碎屑滩及珊瑚藻屑-有孔虫滩6种沉积微相。岩心观察及薄片鉴定结果表明,生物礁体在海底成岩环境、大气淡水成岩环境及区域地下水-埋藏成岩环境中发生的成岩作用包括粘结、溶解、胶结、压实-压溶、重结晶、白云化及“白垩化”作用等。结合沉积相分析结果及成岩作用各个阶段对储集性能的影响,将礁灰岩油藏沉积-成岩演化过程划分为8个时期:iv期成礁、早期暴露-溶蚀、 期成礁、中期暴露-溶蚀、早期成藏、晚期溶蚀、晚期成藏及区域地下水溶蚀。这种特有的演化模式形成了垂向上的8层储层结构,即4个高孔渗段和4个中-低孔渗段间互沉积,4个中-低孔渗段A,B2,C及E段以胶结作用为主,岩性相对致密,隔夹层广泛发育;生物礁体暴露过程中,处于渗流环境的B₁,B₃及D段由于溶蚀作用形成高孔渗段,区域地下水进一步溶蚀和“漂洗”形成的高孔渗段F段为水层。

Sedimentary and diagenetic evolution pattern of reef limestone reservoirs in Liuhua 11 - 1 oilfield

Two types of sedimentary facies(bioherm and organic bank) are developed in Liuhua 11-1 oilfield.They can be subdivided into 6 microfacies,including coralgal reef,coral reef,coralgal-coral reef,foraminiferal bank,bioclastic bank and coralgal debris-foraminiferal bank.Core observation and thin section analysis indicate that the diagenesis of reef complex in sea floor diagenetic environment,fresh water diagenetic environment and regional underground water-buried diagenetic environment include cohesion,dissolution,cementation,compaction-pressure solution,recrystallization,dolomitization and "chalkification",etc.Based on the results of sedimentary facies analysis and the effects of various stages of diagenesis on poroperm characteristics of reservoirs,the sedimentary-diagenetic evolution of reef limestone reservoirs are divided into 8 periods,i.e.the early reef formation,early exposure-dissolution,late reef formation,middle exposure-dissolution,early reservoiring,late dissolution,late reservoiring and regional groundwater dissolution periods.This unique evolution pattern constitutes vertically 8-layer reservoir architecture,including the alternating of 4 high porous and permeable layers and 4 medium-low porous and permeable layers.Cementation is considered a major diagenetic factor in the 4 medium-low porous and permeable layers,namely layers A,B_2,C and E,which are relatively tight and have widely developed intercalations.The layers B_1,B_3 and D,being in percolation environment,have been turned into high porous and permeable layers through dissolution,while the high porous and permeable layer F formed by further dissolution of regional groundwater is an aquifer.