四川盆地安岳大气田震旦系—寒武系储层的发育机制

勘探揭示,四川盆地安岳大气田的3套工业气层分别发育在下寒武统龙王庙组、震旦系灯影组四段和二段,为了给该区的持续勘探发现提供储层研究支撑,分析了储层的主要特征及其发育机制,取得以下3项成果认识:①依据沉积微相、岩性和孔隙三要素将上述储层分为龙王庙组颗粒滩白云岩裂缝—孔洞型储层、灯四段蓝细菌丘滩白云岩缝洞—洞穴型储层和灯二段蓝细菌丘滩白云岩裂缝—孔洞型储层。②龙王庙组储层的主要岩性是颗粒白云岩,储集空间为溶孔溶洞,平均孔隙度为4.24%,平均厚度为36m;灯四段储层的主要岩性是蓝细菌白云岩,溶孔溶洞和洞穴是其主要储集空间,平均孔隙度为3.22%,平均厚度为70 m;而灯二段储层的岩性为蓝细菌白云岩,主要储集空间为溶缝溶洞,平均孔隙度为3.34%,平均厚度为80 m。③储层的发育经历了孔隙形成、热液矿物充填、沥青充填等主要演化阶段,准同生溶蚀作用和表生岩溶作用是储集空间形成的关键,并建立了储层的演化模式。

Genesis mechanism of the Sinian-Cambrian Reservoirs in the Anyue Gas Field,Sichuan Basin

The Lower Cambrian Longwangmiao Fm, the 4^th and 2^nd members of the Sinian Dengying Fm are the three major gas layers in the Anyue Gas Field of the Sichuan Basin. Their main characteristics and genesis mechanism were discussed with the following findings achieved. First, according to sedimentary microfacies, lithology and porosity, the Longwangmiao Fm was described as fractured-vuggy dolomite reservoirs of grain shoal facies, the 4^th member of the Dengying Fm as fractured - vuggy (cavernous) dolomite reservoirs of Cyanobacteria mound beach facies, and the 2^nd member of the Dengying Fm as fractured - vuggy dolomite reservoirs of Cyanobacteria mound beach facies. Second, the major lithology of the Longwangmiao Fm is dominated by grain dolomites and its reservoirs space is dominated by dissolution pores and vugs with an average porosity of 4.24% and an average thickness of 36 m. The 4^th member of the Dengying Fm has cyanobacteria dolomites as its dominant lithology, and dissolution pores, vugs and caverns as its major reservoir space with an average porosity of 3.22% and an average thickness of 70 m. The 2^nd member of the Dengying Fm takes cyanobacteria dolomites as its dominant lithology and fractures and vugs as its major reservoir space with an average porosity of 3.34% and an average thickness of 80 m. Third, those reservoirs experienced multiple evolutionary stages including porosity development, hydrothermal mineral filling, asphalt filling. Penecontemporaneous dissolution and supergene karstification are the key factors controlling the formation of the reservoir space and the evolution models of reservoirs were thus constructed.