RESEARCH ARTICLE


A Crossplot for Mud Logging Interpretation of Unconventional Gas Shale Reservoirs and its Application



Wen-rui Shi1, Chong Zhang1, 2, *, Shao-yang Yuan1, Yu-long Chen1, Lin-qi Zhu1
1 Geophysics and Oil Resource Institute of Yangtze University, Wuhan, Hubei, 430100, China;
2 Oil and Gas Resources and Exploration Technology Laboratory of the Ministry of Education, Yangtze University, Wuhan, Hubei, 430100, China


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© 2015 Zhang et al.;

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Correspondence: * *Address correspondence to this author at the No.111 University Road, Caidian District, Wuhan, China, Post Code: 430100; Tel: 15090830973; E-mail: zhangc012@yangtzeu.edu.cn


Abstract

The drilling time data of gas logging are used to calculate drilling time ratio of the reservoir, and the total hydrocarbon data are used to calculate hydrocarbon contrast coefficient and to establish the drilling time ratio--hydrocarbon contrast coefficient crossplot. The standards of distinguishing the boundaries of hydrocarbon zones, hydrocarbonaceous water layers and dry layers are determined according to the statistics of regional oil testing data. Based on the standards, the crossplot is divided into three areas: hydrocarbon zone, hydrocarbonaceous water layer and dry layer, which are used in mud logging interpretation of abnormal shows in oil and gas layers. This method is widely used for low-resistivity reservoirs, fracture reservoirs, shale gas layers, and especially in the oil and gas zone with weak show and a single component. It is more applicable and accurate than some conventional interpretation methods such as the triangle plot, PIXLER plot, dual light hydrocarbon alkyl ratio and hydrocarbons ratio (3H).

Keywords: Crossplot, drilling time ratio, gas logging, hydrocarbon contrast coefficient, interpretation, unconventional oil and gas.