湖北当阳复向斜北部页岩气地质评价与有利区优选

以露头、钻井、地震等资料为基础,对湖北当阳复向斜北部上奥陶统五峰组—下志留统龙马溪组页岩气成藏条件和勘探潜力展开评价。研究表明,当阳复向斜五峰组—龙马溪组具备良好的页岩气成藏地质条件:五峰组—龙马溪组沉积期以深水陆棚沉积环境为主,页岩广泛发育,优质页岩层厚度约50 m;有机质类型为Ⅱ_2型,有机碳含量一般大于2%,有机质成熟度R_o在3.0%左右,已进入过成熟阶段;页岩中的矿物以石英和黏土为主,有利于后期压裂改造和吸附气的大量富集;储层具有低孔特低渗特征;当阳复向斜构造简单,区域上盖层连续分布,保存条件较好。通过地质评价和资源量计算,当阳复向斜页岩气资源量较为丰富,优选巡检—溪前向斜带和龙坪—肖堰—栗溪背斜带为页岩气勘探有利区。

Geological Evaluation of Upper Ordovician-Lower Silurian Gas-bearing Shales and Optional Potential Areas in the North of Dangyang Synclinorium,Hubei

Based on observation and analysis of samples from outcrops, drilled wells, and seismic data interpretation, it is indicated that controlled by sedimentary environment in deep shelf, the Upper Ordovicain Wufeng-Lower Silurian Longmaxi shales are widely developed and distributed in the north of Dangyang Synclinorium, Hubei province. The organic-rich black shale is about 50m thick. The kerogen type isⅡ2 .The content of organic carbon is generally more than 2%. The Ro is about 3%, which means the shale is in overmature stage.Shale is mainly composed of quartz and clay, which is useful for pressure-fracturing of shale reservoirs and gas enrichment. The shale reservoirs are characterized by low porosity and extra-low permeability. The simple synclinorium structures and the regional overlying cap provide the good preservation condition for shale gas. The resources calculation has indicated good resources potential in this area. Through the overall geological evaluation, it is suggested that the Xunjian-Xiqian synclinal zone and the Longping-Xiaoyan-Lixi anticlinal zone are the favorable potential areas of prospecting shale gas.