川东地区黄龙组碳酸盐岩储层测井响应特征及储层发育主控因素

四川盆地东部(川东)地区上石炭统黄龙组为该区天然气藏主力产层,以岩心观察、铸体薄片鉴定、扫描电镜和岩心物性、孔隙结构等资料分析为基础,结合近期新资料和新认识,对该区黄龙组储层特征进行更为深入的研究。进一步确定黄龙组储层岩性主要为颗粒和晶粒白云岩及白云质岩溶角砾岩;储集空间以晶间孔和晶间溶孔最为发育,次为粒间溶孔、粒内溶孔、铸模孔、超大溶孔,以及未充填的裂溶缝。依据储层的电性差异,深入探讨了不同孔隙类型组合的储层特征,划分出孔洞缝型、孔隙型和裂缝性3类储集类型,建立了相应的测井响应模型。结论认为,黄龙组储层发育的规律是:①粒屑滩相带控制了储层分布范围和规模;②成岩期热液埋藏白云岩化作用是储层形成的基础;③岩溶作用扩大了储层发育范围,也是提高储层质量的关键。

Characteristics of log responses and major control factors of the development of carbonate reservoirs in the Huanglong Formation, eastern Sichuan Basin

The Upper Carboniferous Huanglong Formation is the major gas pay zone in the eastern Sichuan Basin. Based on core observation, cast thin section analysis, SEM, core physical properties, and pore structure, we perform an in depth study of the reservoir characteristics of the Huanglong Formation. The lithologies of the Huanglong Formation reservoirs are dominated by granular dolomite and crystalline dolomite as well as dolomitic karst breccia. The reservoir spaces are dominated by intercrystalline pores and intercrystalline dissolution pores, followed by inter granular dissolution pores, intra granular dissolution pores, moldic pores, super large dissolution pores as well as dissolved fractures without cements. According to the electrical property contrast of reservoirs, we recognize 3 reservoir types including pore cavern fracture type, pore type, and fracture type and build corresponding log response models. The following conclusions are obtained. ①Detrital bank facies belt controls the distribution and scale of reservoirs. ②Thermal and burial dolomitization is the major mechanism of reservoir formation. ③Karstification not only enlarges the scale of reservoirs but improves their quality.