Comprehensive Review about Methane Adsorption in Shale Nanoporous Media

Abstract

Shale/tight gas plays an increasingly important role to meet the growing global energy demand and reduce carbon emissions. Unlike conventional reservoirs, shale formations are subject to rock heterogeneity and have pore size distributions ranging from sub-1 nm to a few micrometers. Thanks to the large number of nanosized pores, adsorbed methane capacity plays a dominant role in total shale gas-in-place. Methane adsorption behaviors can vary drastically in micropores and mesopores, and rock surface type may also greatly affect its adsorption. In this review, we provide a systematic discussion on measurements of shale rock properties including rock compositions and pore structures such as specific surface area (SSA) and pore size distribution (PSD), which are important parameters for methane adsorption in shale nanoporous media. We also provide in-depth discussions on experimental measurements on methane (excess) adsorption in shale nanoporous media, methane adsorption behavior characterization based on molecular simulations, and various excess-adsorption-to-absolute-adsorption conversion methods. We pay particular attention to the assumptions and working mechanisms proposed in various interpretation methods which are embedded in pore structures (SSA and PSD) and absolute adsorption characterizations. In the end, we summarize the key challenges in the methane adsorption characterization in shale media.

Gas Adsorption Capacity of Type-II Kerogen at a Varying Burial Depth

“…Grand canonical Monte Carlo (GCMC) simulations have been proven an effective approach for the prediction of gas adsorption on various inorganic or organic substrates. , In previous studies, , we have used the GCMC method to simulate the adsorption of methane in silica nanopores and montmorillonite nanoslits. In this work, we extend our study to the adsorption of methane in kerogen and take the burial depth into account.…”

“…Kerogen pores are the main locations of adsorbed gas and free gas. The pore structures have been the focus in many studies. − Nitrogen adsorption, , mercury intrusion porosimetry, , and helium ion microscopy have been used to characterize the pore structure and connectivity of kerogen, revealing that kerogen is abundant of micro- (<2 nm), meso- (2–50 nm), and macro-pores (>50 nm). − Bazilevskaya et al found that over 50% pores in shale are smaller than 20 nm in size. Chiang et al revealed that kerogen with higher maturity has a larger pore volume and a larger contactable specific surface area.…”

Highly Stable Doped Barium Niobate Based Electrocatalysts for Effective Electrochemical Coupling of Methane to Ethylene

“…Efficient on-site conversion of methane to value-added chemicals such as ethylene and higher hydrocarbons is an active area of research as many recent discoveries of natural gas reserves made methane a cheap source of energy with an estimated reserve volume of 215 trillion cubic meters worldwide. [1][2][3] Due to these new discoveries, methane prices have dropped from $7-9 USD per million BTU in 2008 to roughly $2 USD per million BTU in 2020. Readily available amounts of natural gas have risen over 30% in the past 20 years, although transporting it to retail locations remains challenging.…”

Adsorption behavior and mechanism of CO2in the Longmaxi shale gas reservoir

“…The experimental results are the excess adsorption amounts, in which the inuence of adsorption phase density is ignored, resulting in lower values than the actual adsorption amount. 24,25 The absolute adsorption amount corrected from the excess adsorption amount is used to characterize the real gas adsorption capacity of shale gas reservoirs (Fig. 2, 3, 4 and 5).…”