微生物碳酸盐岩储层特征与主控因素——以塔里木盆地西北缘上震旦统-下寒武统为例

通过对比分析塔里木盆地西北缘上震旦统-下寒武统微生物碳酸盐岩储层特征,认为随着时代的变迁,不同地层因微生物岩类型的差别而具有不同的微生物岩储层特征。上震旦统以发育泡沫绵层白云岩、非叠层石球粒白云岩和层状叠层石白云岩为主要储集岩石类型,并发育于上震旦统奇格布拉克组的中上部,以微生物层产出;而下寒武统则以凝块石白云岩、泡沫绵层白云岩和叠层石白云岩为主要储集岩石类型,并以礁体或微生物层产出。总体上,微生物碳酸盐岩储层储集空间类型多样,以窗格孔、球粒相关溶蚀孔、泡沫绵层腔溶蚀孔、泡沫绵层腔铸模孔、泡沫绵层腔超大溶孔、凝块间溶孔、晶间孔与晶间溶孔为特征。与其他类型碳酸盐岩储层类似,微生物碳酸盐岩储层的形成是沉积、成岩、构造作用等多种因素共同作用的结果,不同之处在于在某种程度上微生物结构对该类储层的储集空间类型及其结构具有一定的决定性作用。其中,沉积微相和微生物结构总体上控制着微生物岩储层类型及其展布特征,是微生物碳酸盐岩储层形成的基础,而白云石化、埋藏溶蚀作用和构造运作用是微生物岩储层有效孔隙形成的主要影响因素。该项研究成果将为塔里木盆地深层油气勘探提供重要依据。

Characteristics and main controlling factors of microbial carbonate reservoirs:a case study of Upper Sinian-Lower Cambrian in the northwestern margin of Tarim Basin

Through comparative analysis of the characteristics of Upper Sinian-Lower Cambrian microbial carbonate reservoirs in the northwestern margin of Tarim Basin, it is considered that as changing over time, various strata have diversified microbialite reservoir characteristics due to different microbialite types. The Upper Sinian reservoir rocks mainly consist of spongiostromata-type dolomite, non-stromatolitic pellet dolomite and stromatolitic dolomite, which are mainly developed in the middle-upper part of Upper Sinian Qigebulak Formation and outcropped as microbial layers. However, the Lower Cambrian reservoir rocks are mainly composed of clotted dolomite, spongiostromata-type dolomite and stromatolitic dolomite, outcropped as reef or microbial layers. In general, microbial carbonate reservoirs have diversified reservoir space types, characterized by fenestrule, pellet-associated dissolution pore, interclotted dissolution pore, intercrystalline dissolution pore, as well as dissolution pore, mould pore and oversized dissolution pore in spongiostromata-type cavities. Microbial carbonate reservoirs are formed due to the combined effects of multiple factors such as sedimentation, diagenesis and tectonism, etc., which is similar to other carbonate reservoirs. However, the difference lies in that microbial structure plays a certain decisive role in reservoir space types and structures of these reservoirs. Among them, sedimentary microfaces and microbial structure generally control the types and distribution characteristics of microbial carbonate reservoirs, providing a basis for the formation of microbial carbonate reservoirs, while dolomitization, burial dissolution and tectonism are major influence factors for the formation of effective pores in microbial carbonate reservoirs. This research result will provide an important basis for deep hydrocarbon exploration in Tarim Basin.