期刊
MICROPOROUS AND MESOPOROUS MATERIALS
卷 249, 期 -, 页码 88-96出版社
ELSEVIER
DOI: 10.1016/j.micromeso.2017.04.044
关键词
Non-equilibrium molecular dynamics; Transport diffusivity; Temperature control; Knudsen diffusion
类别
资金
- US National Science Foundation [DMS-1209124]
- Society of Petroleum Engineers-Gulf Coast Section through Distinguished Professorship endowment
- Institute of Petroleum Exploration & Development-Langfang Branch
- PetroChina Company Limited
- CNPC Chuan Drilling Engineering Company Limited
- Welch Foundation [E-1882]
- National Science Foundation [CBET-1629398]
- Div Of Chem, Bioeng, Env, & Transp Sys
- Directorate For Engineering [1629398] Funding Source: National Science Foundation
Accurate characterization of shale reservoir properties is vitally important for reliable gas production forecasting and reserve estimation. In this work, we use boundary-driven non-equilibrium molecular dynamics (BD-NEMD) to investigate methane transport in porous clays, which are one of the major mineral components of shale. One of the critical issues in BD-NEMD simulations is robust temperature control schemes to maintain isothermal conditions when the external force is applied to drive fluid flow. To this end, we scrutinize the performance of six temperature control schemes for BD-NEMD. We identify a number of effective temperature control schemes, and we show that careful algorithm selection can considerably reduce the number of simulations required to estimate transport diffusion coefficients. Using a robust temperature control scheme identified in our study, we examine the validity of the Knudsen model for predicting methane diffusivities in clay nano-pores. Although the Knudsen model is one of the most widely used theoretical approaches for predicting reservoir properties, we find that it fails to accurately predict methane transport diffusivities in small clay nano-pores. Our findings therefore suggest that reservoir models based on Knudsen theory may result in significant over- or under-prediction of gas production, depending on reservoir conditions. These findings are consistent with other studies, which posit that the Knudsen diffusion model breaks down in nano-confined systems because it neglects to account for the effects of adsorption on gas transport. (C) 2017 Elsevier Inc. All rights reserved.
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