Characteristics of shale gas in Middle Permian Tongziyan Formation in Fujian Province

The work of geology survey and carbon isotopic composition on shale gas has been done to reasonably evaluate the gas resource potential of Middle Permian Tongziyan Formation. The results indicate that Ⅲ-type kerogen in the shale predominate and the content of organic carbon in the shale is usually under 2%, with the R_ran between 2.52% and 5.80% generally and the organic is in a mature stage of evolution. Shale reservoirs have high content of clay minerals and low content of brittle mineral, which is unfavorable to the fracturing treatment. The shale has low porosity and extremely low permeability, and meso-pores constitute the major space for gas adsorption. Tongziyan Formation gas content is generally low, mainly due to post-tectonic movement and magmatic activity. The analysis showed that the Tongziyan Formation at the bottom of the syncline has reservoir-forming conditions in the relatively less affected local block segment, the Jiafu syncline and the Fushi syncline.