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Collaborating Authors
Results
Forecast of Gas Production From Coal Seams: The Impact of Effective Permeability
Chen, Dong (School of Mechanical and Chemical Engineering, The University of Western Australia) | Liu, Jishan (School of Mechanical and Chemical Engineering, The University of Western Australia) | Pan, Zhejun (CSIRO Earth Science and Resource Engineering) | Connell, Luke D. (CSIRO Earth Science and Resource Engineering)
ABSTRACT: The coalbed methane (CBM) extraction usually begins with dewatering the coal seams to reduce the reservoir pressure. Then the gas desorbs from coal matrix into coal cleats and flows towards production wells. The CBM extraction requires a thorough understanding of the interactions among gas desorption, transport, capillary pressure and coal deformation. Although this issue has been investigated comprehensively in recent years, their combined impact is still poorly understood. There are two reasons for this: one is a lack of effective permeability models that take the effective stress changes into consideration, and the other is the mechanical influences are not rigorously coupled with the gas transport and water flow system. In this work, such permeability models are developed and implemented into a fully coupled finite element (FE) model of coal deformation, water flow and gas transport. The FE model represents important non-linear responses due to the effective stress effects that cannot be recovered where mechanical influences are not rigorously coupled with the water flow and gas transport system. The FE model is verified through the history matching of the gas and water production profiles in the Powder River Basin, and applied to forecast the gas production for a series of hypothetical production scenarios. 1. INTRODUCTION Coalbed methane (CBM) has become an important source of unconventional energy around the world. Forecast of gas production from coal seams relies on the understanding of the multiple physical and chemical interactions in the water-gas-coal system. The effective permeability is one of the most important parameters which determine the gas production. Coal seams are uniformly fractured media which are composed of the matrix and the cleat networks. The coal matrix is the main storage site for coalbed methane which is tightly adsorbed on the coal surface.
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- North America > United States > Wyoming > Powder River Basin (0.99)
- North America > United States > New Mexico > San Juan Basin (0.99)
- North America > United States > Montana > Powder River Basin (0.99)
- (2 more...)
Permeability Evolution In Dual Permeability Dual Stiffness Sorbing Media
Wang, Shugang (Department of Energy and Mineral Engineering and G3 Center, Pennsylvania State University) | Elsworth, Derek (Department of Energy and Mineral Engineering and G3 Center, Pennsylvania State University) | Liu, Jishan (School of Mechanical Engineering, The University of Western Australia)
ABSTRACT: We develop a mechanistic model to represent the evolution of permeability in dual permeability dual stiffness sorbing media such as coal beds and shales. This model accommodates key competing processes of poromechanical dilation and sorption-induced swelling. Permeability evolution is cast in terms of series and parallel models with the series model better replicating observational data. The model may be cast in terms of nondimensional parameters representing sorptive and poromechanical effects and modulated by the sensitivity of the fracture network to dilation or compaction of the fractures. This latter parameter encapsulates the effects of fracture spacing and initial permeability and scales changes in permeability driven by either sorption or poromechanical effects. For a system following a Langmuir type sorption isotherm and where both poromechanical and swelling effects are individually large, a turnaround in net permeability from decreasing at low (sorbing) gas pressures to increasing at large gas pressures is expected. This new mechanistic model is capable of representing key aspects of these changes in the transport parameters of fractured sorbing media to changes in stress and pore pressure. This model is applied to well-controlled observational data for different ranks of coals, and different types of gases, and satisfactory agreement is obtained. 1. INTRODUCTION Gas flow and transport in fractured sorbing media (coals and shales) is relevant to a broad variety of scientific and industrial problems and processes (e.g. geological carbon sequestration, coalbed methane and shale gas production, stability of coal seams and shale caprocks). As a result of processes related to deformation, sorption/desorption, and swelling and shrinking, permeability is a time-dependent property. These effects are especially important in fractured coals and shales, where both permeability and stiffness are intrinsically controlled by the most hydraulically conductive, and most mechanically soft, elements, through the fractures.
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.68)