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四川盆地下寒武统龙王庙组气藏是迄今我国发现的单体规模最大的特大型海相碳酸盐岩整装气藏。为剖析其沉积模式及储层成因,通过地质构造、沉积背景和沉积相综合研究与岩相古地理编图,发现自川西向渝东南地区,龙王庙组依次发育后缓坡混积潮坪、内/浅缓坡颗粒滩(上滩)—滩间海(洼地)、内缓坡台凹开阔较深水海湾→蒸发潟湖→蒸发潮坪、中缓坡风暴岩—障壁滩—丘滩(下滩)以及外缓坡—盆地相,并据此归纳总结出龙王庙组碳酸盐缓坡双颗粒滩沉积模式:1该模式以万州—宜宾台凹为轴,两侧古地貌高地水体浅、能量强而对称发育双颗粒滩,较之于经典模式,该模式新增了环绕古隆起发育的上滩,分布面积达8×10~4 km~2;2上滩沉积时所处古地貌位置最高、水体能量最强而滩体规模大,同生—准同生干热期、湿热期分别更易白云石化和遭受大气淡水溶蚀作用,尤其是得益于毗邻加里东—早海西期剥蚀尖灭线而更易遭受后表生期多期岩溶作用,因而规模优质储层更为发育;3多期大气淡水淋滤使得颗粒岩粒间孔和蠕形动物铸模孔溶蚀扩大,并叠加构造作用,从而形成颗粒滩相控、多旋回层状—准层状、裂缝—孔隙、蜂窝状孔洞型岩溶储层。
The Lower Cambrian Longwangmiao Gas Reservoirs in the Sichuan Basin is by far the largest single giant marine carbonate carbonate gas reservoir discovered in our country. In order to analyze the sedimentary model and the genesis of the reservoir, a comprehensive study of geologic structure, sedimentary background and sedimentary facies and lithofacies palaeogeography maps were conducted to find that the Longwangmiao Formation developed successively from the west to southeast of Sichuan Basin, / Shallow gentle slope granite beach (upper beach) - Tanhai Sea (depression), the inner gentle slope concave wide open deep water bay → evaporation lagoons → evaporation tidal flat, medium gentle slope storm rock - barrier beach - beach (lower beach) and the outer ramp - basin facies, and summarizes the depositional pattern of carbonate sandbodies in Longwangmiao Formation: (1) This model takes Wanzhou-Yibintao depression as an axis, shallow paleogeomorphic highlands on both sides and strong and symmetrical development of double particles Compared with the classical model, the model has newly developed upper beach with paleo-uplift and distribution area of 8 × 10 ~ 4 km ~ 2. On the upper beach, the paleogeomorphology is the highest and the water body is the strongest Large-scale, same-life of the beach body - quasi-symbiotic dry-heat and wet-heat phases are more susceptible to dolomitization and atmospheric freshwater erosion, respectively, and are particularly vulnerable to the back table due to the extinction pinches adjacent to the Caledonian-Early Hercynian Multi-stage karstification, and thus high-quality reservoir More developed. The leaching of atmospheric freshwater in three stages resulted in the dissolution and enlargement of the mold pores of intergranular pores and vermilion grains of granulite and superimposed the tectonic processes to form granulite facies, polycyclic layers, quasi-stratification, fractures and pores , Honeycomb-shaped hole karst reservoir.