Process and Mechanisms of Deep Fluid Effects on Hydrocarbon Generation and Pore Space in Shale: A Case Study from the Mesoproterozoic Xiamaling Formation in the Zhaojiashan Section

Heat carried by deep fluid might greatly affect hydrocarbon generation and pore space in shale. Dyke intrusion carrying high levels of heat may be a means by which to explore the influence of deep fluid on shale reservoirs. This study evaluates hydrocarbon generation and analyzed the evolution of shale storage space in the third member of the Xiamaling Formation in the Zhaojiashan section, Hebei Province, based on experimental data such as TOC, SEM, VRo, low-temperature N-2 adsorption and high-pressure mercury injection. The results show that the dyke intrusion reduced the shale TOC content drastically-by up to 77%-and also induced instantaneous hydrocarbon generation over a range about 1.4 times the thickness of the intrusion. Furthermore, the dyke intrusion might transform organic pores in surrounding shales into inorganic pores. There were two shale porosity peaks: one appeared when VRo = 2.0%, caused by the increase of organic pores as thermal maturity increased, the other occurred when the VRo value was between 3% and 4%, caused by the increase of inorganic mineral pores. It can be concluded that dyke intrusion can be an effective tool with which to study how deep fluid affects instantaneous hydrocarbon generation and pore space in shale.

Automated summary

This study evaluates hydrocarbon generation and analyzes the evolution of shale storage space in the third member of the Xiamaling Formation in Hebei Province. The results show that dyke intrusion significantly reduces the TOC content of shale and induces instantaneous hydrocarbon generation. The intrusion also transforms organic pores in shale into inorganic pores. Two porosity peaks were observed in shale, corresponding to the increase of organic and inorganic mineral pores, respectively.