四川盆地东缘龙王庙组碳酸盐岩储层特征及主控因素

随着安岳气田龙王庙组气藏的发现，四川盆地下寒武统龙王庙组已成为油气勘探的重点层位。基于四川盆地东缘龙王庙组野外露头和岩心观察，通过岩石普通薄片、铸体薄片、X射线衍射、白云石有序度、碳氧稳定同位素和物性测试等，对四川盆地东缘龙王庙组碳酸盐岩储层特征、成岩作用等进行了研究。结果表明，四川盆地东缘龙王庙组沉积期以局限台地和开阔台地沉积为主，主要发育有云坪、颗粒滩、灰坪等，垂向上发育多个滩坪组合序列。储层岩性主要为颗粒白云岩、晶粒白云岩，其次为发生部分白云石化作用的颗粒灰岩，其中颗粒白云岩物性最好，粉晶和细晶白云岩次之，颗粒灰岩发生白云石化部分具有一定的储集性能，未发生白云石化部分通常较致密。储集空间类型为粒间溶孔、晶间溶孔及微裂缝等。储层主要分布在白云石化程度较高的颗粒滩相，颗粒滩是储层形成的物质基础；同生期及早期成岩阶段的白云石化作用和准同生期溶蚀作用是储层发育的2种主要建设性成岩作用，是控制储层发育的关键因素。

Characteristics and main controlling factors of carbonate reservoirs of Longwangmiao Formation in eastern Sichuan Basin

It is the Lower Cambrian Longwangmiao Formation in Sichuan Basin that has become an important reservoir rocks for oil and gas exploration with the discovery of Anyue gas field. Based on the investigation of the outcrops and the boreholes,the characteristics and major controlling factors of the Longwangmiao carbonate reservoirs in the eastern Sichuan Basin were studied by using optical,casting thin sections,X-ray diffraction,order degree of dolomite,carbon,oxygen isotopes analyses,as well as physical property analyses. The following conclusions can be drawn. The main sedimentary facies of Longwangmiao carbonates mainly include the restricted platform and open platform,followed by the tidal flat,grain bank,limestone flat microfacies,etc. Especially, there are many grain shoal and tidal flat groups or rhythms in a single sequence system tract. The lithology of reservoir rocks mainly consists of granular dolomite and the crystalline dolomite,followed by granular limestone with partly dolomitized. The reservoir physical property of granular dolomite is superior to powder and fine crystalline dolostones,the granular limestone with partly dolomitized has limited reservoir properties and the nondolomitization part has little reservoir space. The reservoir spaces are dominated by intergranular denudation pore,intercrystalline denudation pore and micro-fissure. It is revealed that the grain shoal microfacies with high degree of dolomitization is a prerequisite to reservoir rocks,the grain shoal microfacies is the material bases of developing the Longwangmiao formation reservoirs,penecontemporaneous and early stage of diagenesis dolomitization and penecontemporaneous dissolution are the key factors to form the reservoir.