眼球状石灰岩长久以来通常被看作一类非油气储集岩类,而且其成因一直颇有争议.通过对11条野外剖面的观测以及室内薄片鉴定和物性分析,对川东地区茅口组眼球状石灰岩的岩石学特征和储集性能进行研究,并初步探讨了储层的成因机制.研究发现,眼球状石灰岩"眼球"与"眼皮"宏观、微观特征具有较大差异:"眼皮"部分储渗性能相对较好,储集空间主要为各类次生溶蚀孔隙,孔渗相关性好,为低孔-低渗的孔隙型储层.研究结果表明:在盆地内广泛分布的眼球状石灰岩,可作为油气勘探中的致密灰岩储集体.基于眼球状石灰岩宏观、微观特征,结合前人研究成果,初步认为眼球状石灰岩储层的形成与该类岩石的成岩过程密切相关,早期海水埋藏成岩作用阶段形成的层状组构差异,为后期的暴露岩溶作用奠定了物质基础,沉积后的岩溶作用是储层形成的关键.

The diagenesis of the eyeball-shaped limestone traditionally interpreted as source rock has been discussed controversially. Based on field outcrops observation, thin sections identification and physical property analysis, the petrology and reservoir property of the eyeball-shaped limestone of the Middle Permian Maokou Formation are studied in East Sichuan Basin, South China, and the formation mechanism is also discussed. The macro-and micro-scopic characteristics of "eyeball" and "eyelid" are quite different. The porosity and permeability of "eyelid" are relatively good. The reservoir space of "eyelid" is mainly composed of various secondary dissolution pores. In particular, positive correlation between porosity and permeability is found within the "eyelid", as such, this type of composition may incorporate into a conventional porous reservoir with low-porosity and low-permeability. In general, this eyeball-shaped limestone, extensively found in the whole Sichuan Basin, can be served as a relatively tight limestone reservoir for future hydrocarbon exploration. Combined the macro- and micro-features of eyeball-shaped limestone with previous research results, this study suggests that the formation of eyeball-shaped limestone reservoir is closely related to its diagenetic process. The stratified fabric differences formed in the early diagenesis stage lay a material foundation for the later exposed karstification. Moreover, the karstification after deposition is the key to the formation of reservoir.