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.