塔里木盆地东部寒武系白云岩储层及相控特征

Characteristics of the Cambrian Dolomite Reservoirs and Their Facies-Controlling in Eastern Tarim Basin

根据钻井岩心、薄片、物性等数据资料,对塔里木盆地东部寒武系白云岩储层特征进行分析,并探讨沉积相对储层形成的控制作用。塔东地区寒武系白云岩可分为交代白云岩及缝洞充填型白云岩两大类型,交代白云岩又可分为泥粉晶白云岩、细—中晶白云岩、粗晶白云岩以及角砾状白云岩等次级类型。白云岩的储集空间主要以晶间孔隙、溶蚀孔隙、缝合线孔隙和裂缝为主,裂缝起到了连通孔隙的作用,储集空间组合类型以裂缝—孔洞型为主。研究表明:交代白云岩具有明显的相控特点,东侧的英东—罗西一带的交代白云岩主要发育在内缓坡背景的台地边缘浅滩、开阔台地及潮坪相带,而在西侧的古城4井一带的交代白云岩以角砾状白云岩为主,发育于环边陆棚的礁前斜坡带。白云岩储层发育除受后期成岩作用(白云化作用、胶结作用、溶蚀作用)和断裂等因素影响外,主要受早期沉积相带的控制,内缓坡是储层发育的有利部位。

Based on data from core samples,thin section,and physical property,we have investigated petrological characteristics and reservoir properties of dolomite reserviors in the Cambrian of the eastern Tarim Basin.The dolomites in eastern Tarim basin can be subdivided into two categories,replacement dolomite and crack-cavity-filled dolomite.The replacement dolomite can be further subdivided into mud-silt-sized dolomite,fine and midium crystal dolomite,coarse crystal dolomite,and breccia dolomite.The reservoir space in dolomites is predominated by inter-crystal pore,dissolved pore,stylolite pore and cracks and fractures.Cracks and fractures mainly play the role of connecting the pores.The most common reservoir space is mainly the overlapped complex of cracks and cavities.The replacement dolomites show an obvious facies-controlled feature,with the dolomite of the Yingdong-Luoxi region being developed in the marginal shoal,and tidal flat facies belts of the inner ramp setting,and the dolomite in the vicinity of Well Gucheng 4 being developed in the fore-reef slope facies belt of the rimmed shelf setting.Thin section identification and geochemical analysis indicate that the genesis of dolomite in the study area includes the seepage-reflux,burial,and hydrothermal dolomitization.The distribution of the dolomite reservoirs were controlled by the sedimentary facies,diagenesis（dolomitization,cementation,disolution）,and fractures.Higher quality reservoirs are those shaol-facies dolomite overprinted with interaction of seepage-reflux dolomitization,burial dolomitization and/or hydrothermal dolomitization.