Exploration and development potential of the low-maturity continental shale gas in the Fuxin Basin

Abstract

In order to promote the exploration and development of continental shale gas reservoirs in China further, we systematically summarized the geological features of typical continental shale, such as the Ordos Basin. Then, the shale gas reservoir characteristics, geochemical characteristics and fracturing performance of the Lower Cretaceous Shahai Fm in the Fuxin Basin were analyzed by using the data of TOC contents, rock specific surface, pore size distribution and X-ray diffraction analysis of the whole rock. Based on this, it was compared with the marine/continental shale gas reservoirs from the aspect of geological feature. Finally, the shale gas reservoir and resource potential of the Shahai Fm were evaluated. And the following research results were obtained. First, the formation age of China's continental shale is later, its TOC contents vary in a large range, and its organic matters are mainly of a mixed-humic type. And it is characterized by low thermal evolution degree, low quartz content, high feldspar content, high carbonate content, and comparability of total brittle mineral content to marine shale. Second, shale in the Shahai Fm has shallow burial depth and its mineral composition is dominated by quartz, feldspar and carbonate minerals. Its pores are mainly mesopores with an average porosity of 3.47%. There are diverse reservoir spaces, which is favorable for the accumulation of shale gas. Third, the TOC content of the Shahai Fm shale is mainly above 2%, with a moderate thermal evolution degree of organic matter and high gas content. Fourth, the total brittle mineral content of Shahai Fm shale is up to 60%, indicating a good fracturing performance. Fifth, shale reservoirs in the Shahai Fm can be classified into three categories. Type I is target reservoirs of exploration and development, and Type II is favorable reservoirs. It is estimated that the amount of shale gas resources are in the range of 232.2–286.2 billion m3. It is concluded that the Shahai Fm shale in the Fuxin Basin has both resource potential in geology and fracturing performance in engineering, and its exploration and development prospect is broad. What's more, the potential of commercial shale gas development is great in the sweet-point areas.