Experimental investigation of methane adsorption and desorption in water-bearing shale

Abstract

Methane adsorption and desorption in shale can significantly be affected by water due to the water-bearing depositional environment of shale and the application of hydraulic fracturing technology in shale gas production. The characteristics of shale gas adsorption and desorption are comprehensively affected by the temperature, pressure, and especially, the water content in the reservoir. To further explore the impact of water on shale gas adsorption and desorption, the adsorption-desorption experiments of methane in waterbearing shale at different temperatures and different pressures are performed. Afterward, the adsorption behavior and desorption hysteresis are characterized by employing the Langmuir model and Langmuir+λ model. Finally, the ways of the pressure, temperature, and water combinedly affect shale gas adsorption behavior and desorption hysteresis are analyzed. The results show that adsorption and desorption of methane in the water-bearing shale are irreversible, which are consistent with the Langmuir model and the Langmuir+λ model, respectively. An increase in temperature will reduce adsorption and promote desorption, as an increase in temperature essentially enhances the thermal movement of methane molecules. Water lowers the adsorption and desorption of methane in shale, as the water molecules occupy the adsorption sites in organic pores and clay mineral pores in different ways. However, the effect of temperature and water content on adsorption is closely related to the pressure. The lower the pressure, the more significant the effect of temperature and water content. The combined effect analysis demonstrates that the impact of water on methane adsorption in shale is much more significant than that of the temperature. Still, desorption is simultaneously affected by both temperature and water content. As the pressure decreases in the desorption process, the desorption rate is dominantly affected by water when the pressure is lower than 8 MPa, and the desorption rate is aggressively affected by temperature when the pressure is at above 8 MPa.

Clarifying the Effect of Clay Minerals on Methane Adsorption Capacity of Marine Shales in Sichuan Basin, China

“…The relationship between TOC values and V L is presented in Figure 7a, showing an evident positive correlation between the two key parameters, which is consistent with previous studies based on limited data [24,27,53]. The findings indicated that a positive correlation still exists, even when the data become larger.…”

“…The TOC is the most critical parameter for the shale gas reservoir evaluation. The abundance, type, and thermal maturity of OM are key factors affecting shale gas generation and enrichment [27]. The TOC not only affects the absorbed gas content of shales, but also affects the free gas content because a large number of pores are developed in OM in marine shales, which are well preserved during the process of gas generation, becoming the main storage space of shale gas [40].…”

“…In order to evaluate the gas bearing capacity of different types of shale reservoirs, many scholars have studied the adsorption capacity of shale and its controlling factors [22][23][24][25][26]. Recently, Zhang [27] studied the influence of the organic matter (OM) content and its maturity on the adsorption capacity of shale and found that OM is the main controlling factor on gas adsorption in shales, and OM maturity mainly affects the methane adsorption capacity of organic-rich shales at low pressure. Ross [28] pointed out that the shale adsorption capacity is linearly correlated with the TOC, and high vitrinite content accounts for a strong gas adsorption.…”

Molecular Simulation of Adsorption in Deep Marine Shale Gas Reservoirs

“…Shale gas is an important energy resource, and it is mainly stored with free gas and adsorbed gas in shale reservoirs, with adsorbed gas accounting for 20~85% [1,2]. The shale gas reservoir usually has low permeability and low porosity.…”

“…The shale gas reservoir usually has low permeability and low porosity. Generally, the shale matrix porosity is less than 10%, and its permeability is approximately 10 −5 mD [1]. Meanwhile, it has high organic matter content, rich nano-pores, and large specific surface area, which are favorable for methane adsorption, as the main component (more than 95%) of shale gas [3][4][5].…”