四川盆地寒武系洗象池组储层特征及天然气勘探潜力

Reservoir characteristic and gas exploration potential in Cambrian Xixiangchi Formation of Sichuan Basin

统计四川盆地寒武系钻井中膏盐岩含量,结合测井和地震资料刻画了全盆地膏盐岩分布。为此,将四川盆地寒武系分成以乐山-龙女寺古隆起及斜坡区为主的膏盐岩不发育区和以川东-蜀南地区为主的膏盐岩发育区。在此基础上,通过岩心和薄片观察描述揭示洗象池组储层岩石类型以颗粒白云岩和晶粒白云岩为主。储集空间包括孔隙型、溶洞型和裂缝型3大类9小类,且溶洞型是主体。物性测试结果显示膏盐岩不发育区岩心孔隙度多数在2%以下,储层段在3%以上;膏盐岩发育区岩心孔隙度平均为3.5%,最高可达5%。沉积微相是洗象池组储层发育基础,颗粒滩是主要微相类型。大气淡水岩溶作用的叠加改造是膏盐岩不发育区规模优质储层形成的主控因素。构造活动相对强烈的膏盐岩发育区,埋藏溶蚀作用的叠加改造是优质储层形成的关键。展望了洗象池组油气勘探潜力,寒武系膏盐岩不发育的古隆起及斜坡区应以寻找叠加了大气淡水岩溶作用为主的优质滩相储层,优选老井试油,勘探突破值得期待;寒武系膏盐岩发育的川东-蜀南地区以寻找叠加了埋藏溶蚀作用的改造型储层为主,优选成藏条件好的目标进行钻探,是未来勘探突破的重要领域。

The content of gypsum salt rock in Cambrian drilling in Sichuan Basin is counted.The distribution of gypsum salt rock is characterized by combining logging and seismic data.The Cambrian developed area of Sichuan Basin is divided into the undeveloped area of gypsum salt rock mainly in the ancient uplift and slope area of Leshan-Longnusi and the developing area of gypsum salt rock mainly in the area of Chuandong-Shunan.The observation and description of core and thin-section reveal that the main types of reservoir rocks are dolograinstone and dolopackstone.The reservoir space includes three categories and nine subcategories:pore type,cave type and fracture type,and the cavern type is the main type.Physical properties test show that the porosity of core is below 2%and the reservoir is above 3%in non-gypsum developed area.The core porosity is 3.5%on average and up to 5%in the development area of gypsum salt rock.Microfacies are the basis of reservoir development in the Xixiangchi Formation,and grainstone beach is the main microfacies type.The atmospheric fresh water karst is the main controlling factor for the formation of high quality reservoir in undeveloped area of gypsum salt rock.The superimposition of burial dissolution is the key to the formation of high quality reservoir in developed area of gypsum salt rock.The potential of oil and gas exploration in Xixiangchi Formation is prospected.The paleo uplift and slope area of undeveloped gypsum salt rock should be based on searching for high-quality beach reservoir influenced by the karst of atmospheric fresh water.It is an important field of exploration breakthrough to find buried dissolved and superimposed reservoir in the east-shunan area of Cambrian gypsum salt rock.