陆相页岩气的泥页岩评价——以延长下寺湾区上三叠统延长组长7段为例

Source rock evaluation of continental shale gas: A case study of Chang 7 of Mesozoic Yanchang Formation in Xia Siwan area of Yanchang

以鄂尔多斯盆地的延长下寺湾区中生界延长组长7段陆相泥页岩为研究对象,在样品实验数据分析和单井岩心观察的基础上,根据泥页岩的发育与分布特点和有机地球化学特征对陆相页岩气的泥页岩进行评价.结果表明:延长下寺湾区延长组长7段泥页岩主要为浅湖—深湖相沉积,泥页岩累计厚度适宜,有机质类型以Ⅱ1为主,有机质丰度较高,具备页岩气生成的物质基础,有机质演化主要处于成熟阶段.分析美国海相产气页岩与中国陆相产气页岩的综合特征,长7段泥页岩脆性矿物质量分数大于25%,有利于储层的后期改造.相对美国储层物性较好的页岩,根据现场解析法测得的长7段泥页岩含气量较高(平均为4.5m3/t),埋深适中,分布稳定,具有勘探潜力和开发前景.

Based on a large number of samples experimental data analysis and core observation,the systemic evaluation of continental mudstone takes the Mesozoic continental mudstone of the Seven Member of Yanchang Formation in Xia Si-wan area of the Ordos Basin as the research object.And its research of development,distribution and organic geochemical characteristics are carried out.The mudstone of the Seven Member of Yanchang Formation organic material is mainly made up of shallow-deep lake sediments,its cumulative thickness of shale is suitable and organic matter is mainly type II 1.It possesses the material basis of shale gas generation,with higher organic matter abundance in addition to in the mature stage of organic matter evolution.According to the comprehensive correlation of characteristics between continental shale in China and marine shale in America,the mudstone of the Seven Member of Yanchang Formation is conducive to latter reconstruction of the reservoirs for the large quantities of brittle mineral content(more than 25%).Compared with the layers with impressive reservoir properties in America,the mudstone of the Seven Member of Yanchang Formation has higher gas content(average value is 4.5 m3/t).Moreover,appropriately buried depth and steady distribution contribute to exploration and development of shale gas.Consequently,the continental shale gas of the Seven Member of Yanchang Formation in Xia Si-wan area of the Ordos Basin possesses large exploration potential and broad prospects of development.