准噶尔盆地西北缘克-百地区侏罗系成岩作用及其对储层质量的影响

准噶尔盆地西北缘克拉玛依—百口泉地区侏罗系砂岩、砂砾岩储层经历了压实、胶结、溶蚀等多种成岩作用,其中压实和溶蚀作用是控制储层物性的主要成岩作用,其次为胶结作用。压实作用以机械压实为主,是孔隙减少的主要原因。胶结作用主要为碳酸盐胶结,少量黄铁矿胶结,偶见方沸石胶结和硅质胶结。溶蚀作用导致碳酸盐胶结物、长石颗粒和少量岩屑溶解流失。储层孔隙经历了由原生到次生的演化过程。在成岩演化过程中,长石的溶蚀作用、碳酸盐矿物的沉淀与溶解作用是影响储层孔隙发育的关键因素,早期方解石的胶结有利于后期次生孔隙的形成。在克-乌断裂带上、下盘地层中,断裂带上盘埋深浅,一般小于1200m,原生孔隙非常发育;断裂带下盘埋深较深,压实作用强,原生孔隙所占比例明显减少,次生溶蚀孔隙相对发育。次生孔隙的形成受流体及断裂控制。

Jurassic Diagenesis and Its Control on Reservoir Quality in Ke-Bai Area, Northwestern Margin of Junggar Basin

Analysis of laboratory data indicates that the Jurassic reservoir of Ke-Bai area in northwestern margin of Junggar basin experienced compaction,cementation,dissolution and other diagenetic processes.Compaction and dissolution are main diagenetic processes that control the reservoir quality.The compaction is the major reason for reducing storage space.It is here dominated by the mechanical compaction with little significance of compaction-dissolution.The cementation is mainly of carbonate character, with little pyrite-cementation and less analcidite-and kiesel-cementation.The dissolution comprises cabonate cement dissolution, lithic grains dissolution and detrital feldspar dissolution.The reservoir pores evolved from primary to secondary pores.The pore space was affected by the dissolution of calcite and feldspar,as well as the precipitation and cementation of carbonates.The cementation by early calcite is favorable for the development of secondary pores in the later stage.The difference between the reservoir characteristics for different walls of the fault belt is obvious.On the hanging wall of the fault belt,the burial depth of strata is shallower,less than 1800 m,and the storage space is characterized by primary pores;However,on the foot wall of the fault belt,the burial depth of strata is deeper.Because of strong compaction,the proportion of the primary pores become obviously less,and the secondary pores are the major storage space.The characteristics of the secondary pore distribution are controlled by the distribution of acid fluid and fault.