Gas Flow Tightly Coupled to Elastoplastic Geomechanics for Tight- and Shale-Gas Reservoirs: Material Failure and Enhanced Permeability
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
We investigate coupled flow and geomechanics in gas production from extremely low permeability reservoirs such as tight and shale gas reservoirs, using dynamic porosity and permeability during numerical simulation. In particular, we take the intrinsic permeability as a step function of the status of material failure, and the permeability is updated every time step. We consider gas reservoirs with the vertical and horizontal primary fractures, employing the single and dynamic double porosity (dual continuum) models. We modify the multiple porosity constitutive relations for modeling the double porous continua for flow and geomechanics. The numerical results indicate that production of gas causes redistribution of the effective stress fields, increasing the effective shear stress and resulting in plasticity. Shear failure occurs not only near the fracture tips but also away from the primary fractures, which indicates generation of secondary fractures. These secondary fractures increase the permeability significantly, and change the flow pattern, which in turn causes a change in distribution of geomechanical variables. From various numerical tests, we find that shear failure is enhanced by a large pressure drop at the production well, high Biot's coefficient, low frictional and dilation angles. Smaller spacing between the horizontal wells also contributes to faster secondary fracturing. When the dynamic double porosity model is used, we observe a faster evolution of the enhanced permeability areas than that obtained from the single porosity model, mainly due to a higher permeability of the fractures in the double porosity model. These complicated physics for stress sensitive reservoirs cannot properly be captured by the uncoupled or flow-only simulation, and thus tightly coupled flow and geomechanical models are highly recommended to accurately describe the reservoir behavior during gas production in tight and shale gas reservoirs and to smartly design production scenarios.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Sciences Division
- Sponsoring Organization:
- USDOE; USEPA
- Grant/Contract Number:
- AC02-05CH11231
- OSTI ID:
- 1182652
- Report Number(s):
- LBNL-6961E
- Journal Information:
- SPE Journal, Vol. 19, Issue 06; ISSN 1086-055X
- Publisher:
- Society of Petroleum Engineers (SPE)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Simulation of Gas Production from Multilayered Hydrate-Bearing Media with Fully Coupled Flow, Thermal, Chemical and Geomechanical Processes Using TOUGH+Millstone. Part 2: Geomechanical Formulation and Numerical Coupling
|
journal | February 2019 |
Some key technical issues in modelling of gas transport process in shales: a review
|
journal | July 2016 |
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