鄂西地区震旦系陡山沱组二段页岩气储层测井评价初探

鄂西地区震旦系陡山沱组是中国页岩气勘查的新层系,其页岩储层矿物成分以白云石为主,测井响应特征与奥陶系五峰组—志留系龙马溪组、寒武系牛蹄塘组硅质页岩明显不同,原有储层"七性"关系测井评价对于陡山沱组页岩储层精细刻画和压裂施工解释评价存在一定的不适用性。本文以鄂阳页1井为例,综合利用常规测井、特殊测井和样品测试分析资料,研究发现不同于五峰组—龙马溪组和牛蹄塘组硅质页岩"四高四低"测井响应特征,陡山沱组二段云质页岩具有低伽马、低铀、低声波时差、低中子,高电阻率、高密度"四低两高"测井响应特征,认为元素测井是评价陡山沱组二段页岩地层总有机碳含量最直接和有效的方法,MRIL-P型核磁测井适用于该地层孔隙度参数评价。通过拟合计算完善了适用于该地层的含气量估算方法,获取了有利页岩储层评价参数,研究成果将为同类型页岩储层测井评价提供参考依据。

Discussion on petrophysical evaluation of shale gas reservoir in the second Member of Sinian Doushantuo Formation in Western Hubei Province, South China

Being a new layer of shale gas exploration in China, the Sinian Doushantuo Formation located in western Hubei Province, which shale reservoir mineral composition is dominated by dolomite and therefore its log response characteristics is obviously different with the siliceous shale of Ordovician Wufeng Formation, Silurian Longmaxi Formation and the Cambrian Niutitang Formation. The previous "seven parameter relationship" study on Longmaxi and Niutitang Formation is not support effectively for the fine characterization and fracturing construction of the Doushantuo Formation shale reservoir. In this paper, after analyzed the conventional logging, special logging and sample data of Eyangye 1 well, we suggested that the logging response characteristics of second member of Sinian Doushantuo Formation with low gamma, low uranium, low acoustic time difference, low neutron, high resistivity, and high density on the conventional logging curve. Furthermore, we proposed that the elemental logging is the most direct and effective logging method for evaluating the TOC of the second member of Doushantuo Formation shale, and analyzed that MRIL-P type nuclear magnetic survey is suitable for the evaluation of porosity parameters. At last, we evaluated the shale gas content via the new fitting method, and obtained favorable evaluation parameters of shale reservoirs. The research results above mentioned will provide parameter basis for the logging evaluation of the same type shale reservoir.