Analysis on Collapse Pressure and Fracture Pressure of a Borehole in Natural Gas Hydrate Formation
- T. Tan (China University of Petroleum-Beijing) | H. Zhang (China University of Petroleum-Beijing) | J. Li (China University of Petroleum-Beijing) | H. Wang (China University of Petroleum-Beijing) | Z. Cai (China University of Petroleum-Beijing) | Q. Yu (China University of Petroleum-Beijing) | M. Yang (China University of Petroleum-Beijing) | Y. Chen (China University of Petroleum-Beijing) | K. Liu (China University of Petroleum-Beijing) | Q. Deng (China University of Petroleum-Beijing)
- Document ID
- American Rock Mechanics Association
- 53rd U.S. Rock Mechanics/Geomechanics Symposium, 23-26 June, New York City, New York
- Publication Date
- Document Type
- Conference Paper
- 2019. American Rock Mechanics Association
- 6 in the last 30 days
- 54 since 2007
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ABSTRACT: Special rock mechanical characteristics of natural gas hydrate (NGH) sediments lead to the inapplicability of traditional well stability models. In this paper, a new model to calculate the collapse pressure and fracture pressure of a borehole in NGH formation is studied based on the laboratory experiment results in published literature, mainly considering the effect of the saturation of NGH. Amended Mohr-Coulomb failure criterion is applied to calculate the collapse pressure while the fracture pressure is calculated combining Griffith criterion. Case study of this model is carried out and sensitivity analysis is performed to reveal the effects of original rock cohesion, Biot coefficient, frictional angle and pore pressure. The results show that the collapse pressure increases, while the fracture pressure decreases, with the decrease of NGH saturation. The collapse pressure decreases with the increase of the original rock cohesion and the decreases of Biot coefficient and pore pressure at any saturation. however, it decreases with the increase of the frictional angle in low saturation region while shows opposite trend in high saturation region. The fracture pressure increases with the increases of the frictional angle and the original rock cohesion and the decreases of Biot coefficient and pore pressure.
As the conventional reservoirs are being gradually depleted, natural gas stored under unconventional conditions is required to be discovered and recovered (Sloan 2003). Regarded as a new energy resource with the potential of providing human with a great amount of natural gas, NGHs are clathrates composed of methane gas under a low-temperature and high-pressure condition (Makogon et al., 2007; Makogon, 2010; Wang and Economides, 2011; Li et al., 2018).
A lot of research has been performed on NGHs. Attention was firstly drawn to this compound by the pipeline blockage problem resulted from the formation of gas hydrate during the transportation of natural gas through cold environment (Hammerschmidt, 1934). Later the natural gas resources were discovered and developing approaches were focused on. NGHs are mainly distributed in two regions: (1) land permafrost areas and (2) offshore areas at outer continental margins (Collet 1990).
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