ABSTRACT
This paper discusses the characteristics of gas-water distribution during different thermal evolution processes of shale reservoirs. Shale is originally deposited in water-saturated environment. And the movable water in the pores cannot be completely discharged even after the deposition and compaction process. Only when kerogen begins to generate hydrocarbon and produces enough pressure, a large amount of water would be discharged. Kerogen can generate hydrocarbons in two ways: depolymerization type and parallel defunctionalization type. The organic pores and hydrocarbon gases are generated during the evolution of hydrocarbon in shale reservoirs. The results reveal the micro-characteristics of gas-water distribution in both organic and inorganic pores. During the evolution process, formation of water is gradually displaced through generated gas phase. At the late stage of evolution, organic pores are dominated by single-phase gas. Few amounts of water molecules are adsorbed near the functional group. In inorganic pores, the gas-water distribution is evolved from water-saturated to water-film during the evolution process. Liquid water only exists in some micro-pores. This study can provide a theoretical basis for accurately predicting the gas content of shale reservoirs.
