A Basin Modeling Research On Zhangjiatan Shale Gas Content In Ordos Basin

Currently shale gas exploration and development at home and abroad has been developing rapidly. The gas content of shale plays a very important role in shale gas favorite zone optimization and resources assessment. Mesozoic lacustrine shale gas in Ordos Basin is one of the most important shale gas plays in China. This paper made a research of the gas content in Zhangjiatan shale in basin modeling ways.Based on the geological materials and documents, the strata, geologic evolution, sedimentology evolution and oil systems of Ordos Basin were concluded in the paper. The clastic formations have experienced Yinzhi, Yan Mountain and Himalaya Mountain movements. Geologic characteristics of Zhangjiatan shale which includes the distribution, sedimentary facies, geochemistry, reservoir characteristics and gas content were concluded based on experiments and logging data. The kerogen types of Zhangjiatan shale are mainly type ? and type ?1 with a TOC range of 1%-12%, and Ro ranges from 0.5% to 1.3%. The gas content tests showed that there is a great potential of shale gas in Zhangjiatan shale. Taking into account of the characteristic of shale gas and the principle of conventional oil and gas basin modeling, the principle and procedure of shale gas basin modeling were concluded. Based on the material of layer thickness, erosion and paleowater depth, the geologic history of the basin was simulated. The maturation history of the shale was also simulated and calibrated based on the materials of geologic history, heat flow, gradient and measured vitrinite reflectance. The transmission ration of kerogen and original TOC was calculated and thermo compression simulation experiments was done on low maturity Zhangjiatan shale, thus, the gas generation history was simulated. Darcy flow was applied in the modeling and the gas content in the shale gas was simulated too. It was estimated that the shale gas resource in Zhangjiatan shale is about 0.5×1012 m3,which includes 0.35 ×1012m3 absorbed gas and 0.15 ×1012m3 free gas. The recoverable reserve was estimated as 0.15 X 1012m3.Compared with the conventional shale gas resource evaluation methodologies, shale gas basin modeling not only takes into account of the heterogeneity of gas content of the shale, but also makes a simulation of the course of the formation of shale gas accumulation. The simulated porosity, maturity and gas content matches with the measured data very well which suggested that the shale gas basin modeling is applicable in Ordos Basin Zhangjiatan shale gas content research. It was concluded that the shale gas basin modeling can also be applied to similar shale gas bearing basins.