Multiple porosity model of a heterogeneous layered gas hydrate deposit in Ulleung Basin, East Sea, Korea: A study on depressurization strategies, reservoir geomechanical response, and wellbore stability
Precise simulation of the geomechanical response is crucial for the gas hydrate production such as from the deposits in Ulleung Basin, East Sea, Korea, which exhibit severe vertical heterogeneity of the hydrate-bearing sand and mud layers. Physically, depressurization causing hydrate dissociation can induce critical subsidence. Meanwhile, it is numerically cumbersome to apply the fine-scale single porosity model to the heterogeneous layered system particularly for geomechanics. In this study, to investigate geomechanical responses of the intercalated layer system based on various depressurization scenarios, we employ a multiple porosity (MP) model with upscaled geomechanical properties while flow variables kept in the fine-scale. For the rigorous two-way coupling between the fluid flow and geomechanics, the fixed-stress sequential method is employed with two individual simulators, the TOUGH+HYDRATE for the flow and an in-house code (called the ROCMECH) for the geomechanics. Specifically for the ROCMECH, we applied axisymmetric geomechanics for more precise calculation of deformation near the wellbore. Numerical experiments of field-wide simulations are about two different comparison studies for depressurization: a constant bottom hole pressure (BHP) and several different BHPs cases. For a constant BHP case, gas production periods, i.e., 14- and 100-days productions representing short- and long-term, respectively, are compared, while several different BHPs case including continuous and periodic depressurizations is focused on the comparison of the productivity and geomechanical stability. From the case of constant BHP, we confirm significant vertical displacement due to the weaker stiffness of the formation after hydrate dissociation, which can aggravate as the production continues. Among the cases with varying BHP, the periodic depressurization scenario exhibits superiority with significantly small subsidence despite similar productivity. The MP model employed in this study can help devise depressurization strategies for gas hydrate reservoirs, especially for the precise and efficient calculation of the geomechanical responses of the intercalated layer system.
- Research Organization:
- Texas A & M Univ., College Station, TX (United States). Texas A & M Engineering Experiment Station
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE); Korea Institute of Geoscience and Mineral Resources (KIGAM)
- Grant/Contract Number:
- FE0028973; GP2021-010; GP2016-027
- OSTI ID:
- 1830273
- Alternate ID(s):
- OSTI ID: 1846002
- Report Number(s):
- DOE-TAMU-FE0028973-18; S1875510021005163; 104321; PII: S1875510021005163
- Journal Information:
- Journal of Natural Gas Science and Engineering, Journal Name: Journal of Natural Gas Science and Engineering Vol. 96 Journal Issue: C; ISSN 1875-5100
- Publisher:
- ElsevierCopyright Statement
- Country of Publication:
- Netherlands
- Language:
- English
Similar Records
System response to gas production from a heterogeneous hydrate accumulation at the UBGH2-6 site of the Ulleung basin in the Korean East Sea
Analysis of short‐ and long‐term system response during gas production from a gas hydrate deposit at the UBGH2‐6 site of the Ulleung Basin in the Korean East Sea