四川盆地东部黄龙组古岩溶特征与储集层分布

Paleokarst and reservoirs of the Huanglong Formation in eastern Sichuan Basin

综合地表地质、钻井资料和碳、氧、锶同位素地球化学特征,详细描述古岩溶的鉴别标志,并进一步分析古岩溶作用垂向分带性和平面分区性以及岩溶强度与储集层发育的关系。研究表明,岩溶角砾岩是识别古岩溶作用最直接的标志;不同成因类型和溶蚀强度的岩溶岩与胶结物的稳定同位素地球化学特征各异,其形成和演化规律明显受流体来源、性质及同位素分馏效应影响;小型针孔型储集层测井曲线与大型洞缝型储集层具有明显区别。古岩溶储集层的发育与分布规律主要受构造、古气候、岩性和岩相等因素控制,最有利于储集层发育的岩性是黄龙组二段的白云岩,最有利于储集层发育的层位是黄龙组二段的上部溶蚀段和下部溶蚀段,最有利于储集层发育的位置是岩溶高地和岩溶斜坡中残丘及坡地等微地貌单元。

According to the combination of surficial geology,drilling data,and the isotope geochemical characteristics of carbon,oxygen and strontium,the identification markers of paleokarst were described in detail,and the relationships between the vertical zoning,plane distribution and karstification degree of paleokarst and the reservoir development were further analyzed.The study shows that karst breccias are the direct sign of paleokarst.Karst of different genetic types and dissolution intension and its cements have different stable isotope geochemical characteristics,and their formation and evolution are significantly influenced by fluid sources,fluid nature and isotope fractionation.The identification markers of small scale pinholes are quite different from those of large scale holes.The development and evolution of palaeokarst are mainly controlled by structure,palaeoclimate and lithology.The best lithology for the development of reservoir is dolomite in the C2hl2,the best zones for the development of reservoir are located in the upper and lower dissolution sections of C2hl2,and the best positions for the development of reservoir are located in the karst highland,remnant hills and sloping fields in the karst slope.