天然气勘探与开发2025，Vol.48Issue(3)：14-26,13.DOI:10.12055/gaskk.issn.1673-3177.2025.03.002
川中龙女寺地区二叠系中统茅口组储层特征及成因机制
Reservoir characteristics and forming mechanisms in the Middle Permian Maokou Formation,Longnvsi area,central Sichuan Basin
摘要
Abstract
The Middle Permian Maokou Formation has recently emerged as one of vital reservoirs for natural-gas exploitation in Longnvsi area.However,Maokou reservoirs are characterized by strong heterogeneity resulting in uncertain forming mechanisms,which may retard their efficient exploration and development.Thus,the depositional and petrological characteristics,and reservoir space and types were analyzed for this formation after core observation,thin-section identification,and logging-data analysis.Moreover,reservoir-forming mechanisms and the main geological process controlling reservoir evolution were discussed to create an evolution model.Results show that(i)Maokou reservoirs in the study area are dominantly developed with fine-to medium-crystalline dolomite in the lower part of the second member of Maokou Formation(Maokou 2 Member).Generally,unreal images of residual grain are visible in the dolomite.And such reservoirs belong to low porosity and ultra-low permeability ones;(ii)their space consists of intercrystalline pores,intercrystalline dissolution pores,needle-like pores,contiguous fractures and vugs,and fractures.And they can be classified into three types,such as fractured-vuggy,vuggy,and porous reservoirs,with the first two as the predominant;(iii)dolomite reservoirs are mostly extended into grain-beach bodies.And not only fragmental shoal but bioclastic beach facies belts exhibit remarkably higher porosity than that in inter-beach sea and platform-flat facies belts;and(iv)initial pores are stemmed from meteoric freshwater of penecontemporaneous dissolution.Dolomitization preserves reservoir space.Early hydrothermal fluid invasion along faults induces hydraulic fractures to generate saddle-shaped dolomite filling.Accordingly,the created model is in line with the fragmental shoal as the basis,the penecontemporaneous dissolution for forming reservoirs,the dolomitization for reservoir preservation,and the hydrothermal alteration for making reservoirs better.In conclusion,strong heterogeneity in these Maokou reservoirs is jointly conditioned by sedimentary facies belts and multiepisodic diagenesis,with the dissolution attributing to reservoir basis,the expanded space due to the alteration,and beach bodies'structure and fault system as the major controls on the development of quality reservoirs.关键词
四川盆地中部/龙女寺地区/二叠系中统茅口组/白云岩/储层成因/储层演化模式/非均质性Key words
Central Sichuan Basin/Longnvsi area/Middle Permian Maokou Formation/Dolomite/Reservoir-forming origin/Reservoir-evolution model/Heterogeneity引用本文复制引用
罗文军,叶宁,兰雪梅,张云峰,闫梦楠,徐伟,付蕾..川中龙女寺地区二叠系中统茅口组储层特征及成因机制[J].天然气勘探与开发,2025,48(3):14-26,13.基金项目
中国石油天然气股份有限公司重大科技专项(编号:2023ZZ16-03). （编号:2023ZZ16-03）
