四川盆地龙潭组沉积微相及页岩储层发育特征

Sedimentary Microfacies and Shale Reservoir Development Characteristics of Longtan Formation, Sichuan Basin

四川盆地上二叠统发育海陆过渡相沉积体系,其中的龙潭组是页岩气的有利勘探开发层位。本文以露头剖面、钻井取样资料为主要研究对象,利用常规和扫描电子显微镜、氩离子抛光、X-衍射、压汞等分析手段,开展四川盆地海陆过渡相龙潭组沉积微相特征研究和储层发育特征研究。研究结果表明:(1) 川中–川南地区龙潭组在早期形成的峨眉山玄武岩的基础上,由西南向东北依次发育河泛平原(冲积平原)——潮坪–浅水陆棚沉积体系,其中,泥页岩主要发育在河漫滩、河漫湖泊、泥坪、泥炭坪中;(2) 脆性矿物含量分布受沉积相带影响,表现为川南地区粘土矿物多、脆性颗粒较少,北部地区反之;(3) 龙潭组内泥页岩及砂岩主要发育粒(缘)间孔隙、晶间孔与微裂缝,局部发育粒内孔隙与溶蚀孔隙,少见有机质孔隙;(4) 川南地区为海陆过渡环境沉积产物,粉砂质、炭质含量较高,孔隙度介于1.51%~12.53%,平均5.84%;川东北地区为陆棚环境,为一套海相沉积物,储集岩孔隙度介于0.57%~7.69%之间,平均孔隙度为2.79%。

The sea-land transitional facies sedimentary system was developed in the Upper Permian of Sichuan Basin, and the Longtan Formation is a favorable reservoir for shale gas exploration and development. Based on outcrop profile and well sampling data, this paper uses conventional and scanning electron microscopy, argon ion polishing, X-ray diffraction, mercury injection and other analytical methods to study the depositional microfacies and reservoir development characteristics of Longtan Formation in Sichuan Basin. The results show that: (1) Sichuan Basin is developed River panplain (alluvial plain)—tidal flat-hallow water shelf sedimentary system and Mud shale is mainly developed in four sedimentary microphases: flood plain, river lake, mudflat and peat flat. (2) The distribution of brittle minerals is affected by sedimentary facies belts, which shows that there are more clay minerals and less brittle quartz particles in southern Sichuan, and the accumulation of carbonate minerals and quartz particles in northern Sichuan is conducive to the high content of brittle minerals;(3) In the Longtan Formation of Sichuan Basin, the shale and sandstone mainly develop intergranular pores, intergranular pores and micro-fractures, and locally develop intra-granular pores and solution pores, rarely organic pores;(4) The silty, carbonaceous content is higher in southern Sichuan, and the porosity ranges from 1.51%-12.53%, with an average of 5.84%;The northeast Sichuan area is a set of Marine sediments with reservoir rock porosity ranging from 0.57% to 7.69% with an average porosity of 2.79%.