中二叠统栖霞—茅口组碳酸盐岩是四川盆地天然气勘探开发重点层系之一。南川地区位于四川盆地东南缘,前期勘探表明南川地区栖霞—茅口组具有较大天然气开发潜力。为明确南川地区中二叠统栖霞—茅口组碳酸盐岩储集空间特征,基于JY205-2井岩心样品,采用薄片鉴定、扫描电镜实验、X射线衍射分析等测试手段,对储集空间进行分类研究。将储集空间分为孔隙和裂缝2大类,其中孔隙包括无机孔和有机孔;裂缝包括应力缝、粒缘缝、收缩缝。储集空间类型受岩性控制明显,栖霞—茅口组碳酸盐岩储层占主导地位的储集空间类型为粒内溶蚀孔和粒缘溶蚀缝,粒缘溶蚀缝具有较好的孔缝连通作用,有利于改善储层渗透率,其中泥质含量较高层段可见较丰富的黏土矿物晶间孔。茅一段①小层粒内溶蚀孔和黏土矿物晶间孔面孔率数值最高,与该段较高的孔隙度、渗透率数值吻合较好,认为茅一段①小层是该区天然气勘探有利层位。

Middle Permian Qixia-Maokou Formation is one of the most important series of strata to explore and develop natural gas in Sichuan Basin. Nanchuan area is located in the southeast of Sichuan Basin. The pilot exploration indicates that there is a great development potential for natural gas in Qixia-Maokou Formation. In order to know its reservoir spaces of carbonate rocks, the test methods, such as thin section identification, SEM and phase analysis of X-ray diffraction, have been taken based on the samples of Well-JY205-2. The reservoir spaces are classified into two categories: pores and fractures. Pores include organic pores and inorganic pores, while fractures include stress fractures, grain edge fractures and shrinkage cracks. The types of reservoir spaces are obviously controlled by lithology. In Qixia-Maokou Formation, the dominant reservoir space types of carbonate reservoirs are the intragranular dissolution pores and the dissolution fractures distributed along the particle edge. These dissolution fractures can connect the pores with the fractures better, and are beneficial to improve the permeability of the reservoir. There are abundant intercrystalline pores of clay minerals in the layers with higher argillaceous content. The surface porosity of intragranular dissolution pores and intercrystalline pores of clay minerals in the layer-① of Mao-1 Member are the highest and in good agreement with the higher porosity and permeability in this layer, which indicates that the layer-① of Mao-1 Member is favorable to natural gas exploration.