Molecular Simulation Helps Determine Key Shale-Gas Parameters
- Adam Wilson (JPT Special Publications Editor)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- July 2014
- Document Type
- Journal Paper
- 94 - 97
- 2014. Society of Petroleum Engineers
- 1 in the last 30 days
- 243 since 2007
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This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 164790, "Molecular Simulation To Determine Key Shale-Gas Parameters and Their Use in a Commercial Simulator for Production Forecasting," by F. Gouth, Total; J. Collell and G. Galliero, Universite de Pau and Pays de l'Adour; and J. Wang, ecole Centrale de Pekin, prepared for the 2013 SPE Europec/EAGE Annual Conference and Exhibition, London, 10-13 June. The paper has not been peer reviewed.
Shale gas is fast becoming a source of energy of paramount significance for the coming years. Although commercial production has been achieved in numerous plays throughout the world, the actual physics involved is poorly understood. Molecular simulation is an emerging technique that can be put to use for shale gas. It offers insights into nanoscale properties such as sorption or transport coefficients. The technique is based on numerical simulations at the molecular scale for a given set of pressure and temperature conditions.
Comprehensive organic-shale rock characterization performed in recent years has emphasized the dual nature of the porous system, which is split between organic and inorganic pores, each system having its own scales and associated physical properties. At least two clearly identified mechanisms are likely to cause composition changes over time: In tiny pores, where specific surfaces are huge with respect to volumes, gas exists in both free and condensed (adsorbed) states and in different compositions. Because free and adsorbed gas will not be produced at the same time in a well’s life because the process is pressure dependent, a change in the produced-gas-composition stream is likely. In addition, flow through the nanometer-scale pore system exhibits not a Darcy pattern but a diffusion type of flow (transitional or free molecular flow) where transport coefficients depend on the molecule size. This mechanism is well-known in gas chromatography as molecular sieving and also will result in composition changes.
This paper seeks to offer a comprehensive screening of the current means available for representing such effects and to examine their consequence on long-term production with an appropriate model.
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