Ground movements associated with gas hydrate production. Progress report, April 1, 1992--June 30, 1992

• Main Author: Siriwardane, H.J.
• Language: unknown
• Published: 2008
• Subjects: 03 NATURAL GAS; GROUND SUBSIDENCE; MATHEMATICAL MODELS; GAS HYDRATES; PRODUCTION; DISSOCIATION; PROGRESS REPORT; NATURAL GAS HYDRATE DEPOSITS; PERMAFROST; MATERIALS RECOVERY; ROCK MECHANICS; FORECASTING; PARAMETRIC ANALYSIS; FINITE ELEMENT METHOD; permafrost
• Online Access: http://www.osti.gov/servlets/purl/10142702; https://www.osti.gov/biblio/10142702; https://doi.org/10.2172/10142702

An obvious consequence of hydrate dissociation is the compression of reservoir matrix causing displacements in the surrounding area. The reservoir compression is a time-dependent process which depends on the production rate. The ground movements cause additional stresses in the overburden which may result in rock mass fracture and failure. Rock failure may cause rubble formation or bulking in the fracture zone. This in turn can cause an increase in permeability for gas flow which may offset the reduction in permeability caused by closure of existing fractures during reservoir compression. The mechanics of ground movements during hydrate production can be more closely simulated by considering similarities with ground movements associated with subsidence in permafrost regions. The purpose of this research work is to investigate the potential strata movements associated with hydrate production by considering similarities with ground movements in permafrost regions. The work primarily involves numerical modeling of subsidence caused by hydrate dissociation. The investigation is based on the theories of continuum mechanics, thermomechanical behavior of frozen geo-materials, principles of rock mechanics and geomechanics. It is expected that some phases of the investigation will involve the use of finite element method, which is a powerful computer-based method which has been widely used in many areas of science and engineering. Parametric studies will be performed to predict expected strata movements and surface subsidence for different reservoir conditions and properties of geological materials. The results from this investigation will be useful in predicting the magnitude of the subsidence problem associated with gas hydrate production. The analogy of subsidence in permafrost regions may provide lower bounds for subsidence expected in hydrate reservoirs. Furthermore, it is anticipated that the results will provide insight into planning of hydrate recovery operations.