Evaluation of Lower Cambrian Shale in Northern Guizhou Province, South China: Implications for Shale Gas Potential

The Lower Cambrian shale is an important source rock for conventional oil and gas in northern Guizhou province (NGP), south China, but has recently been considered as a potential shale gas reservoir. In this study, characterization of this target shale was determined through a systematic series of measurements on core samples. According to total organic carbon (TOC) and Rock-Eval data, the Lower Cambrian shale is overmature but still contains high amounts of organic matter, which is composed mainly of alginite. The TOC content is enriched up to 10.4% at the base of the shale. There are two different correlation patterns between trace elements and TOC in the Lower Cambrian shale. A good correlation present in the upper part indicates a non-sulfidic anoxic sedimentary environment. However, higher enrichments of U, V, and Mo in the basal part exhibit sulfidic euxinic conditions. Brittle minerals are quite abundant and have a critical effect on artificial fracture. Gas sorption volume increases with an increasing TOC, pore volume, and surface area, indicating that pores at the microscale associated with the organic matter fraction are an important control on storage capacity. The contribution of clay minerals to the sorbed gas may be irrelevant because of the presence of moisture. Analysis of data indicates that the basal part of the Lower Cambrian shale demonstrates the greatest potential for gas content and can be explored for production.