Relationship between Creep Property and Loading-Rate Dependence of Strength of Artificial Methane-Hydrate-Bearing Toyoura Sand under Triaxial Compression

Methane hydrate is anticipated to be a promising energy resource. It is essential to consider the mechanical properties of a methane hydrate reservoir to ensure sustainable production, since its mechanical behavior may affect the integrity of the production well, the occurrence of geohazards, and gas productivity. In particular, the creep property of methane-hydrate-bearing sediment is thought to have great significance in the long-term prediction of the mechanical behaviors of a reservoir. In earlier studies, triaxial compression tests were conducted on artificial methane-hydrate-bearing Toyoura sand under three axial-loading conditions, i.e., constant-strain-rate test, constant-stress-rate test, and creep (constant-stress) test. In this paper, the time-dependent properties of the methane-hydrate-bearing Toyoura sand observed in these tests were quantitatively discussed and found to be almost in agreement. The creep life obtained from the creep tests had a reasonably strong correlation with the loading-rate dependencies of strength, obtained from the constant-strain-rate tests and constant-stress-rate tests based on a simple hypothesis. The findings are expected to be used to develop a constitutive model considering the time-dependent behaviors of hydrate-bearing soil in future studies, and to improve the reliability of long-term prediction of the geomechanical response to gas extraction from a reservoir

Effects of Methane Hydrate Saturation and Confining Pressure on Strain-Rate Dependence of Artificial Methane-Hydrate-Bearing Sediment in Triaxial Compression Test

In this study, drained triaxial compression tests were conducted on artificial methane-hydrate-bearing sediment samples under various conditions of methane hydrate saturation and confining pressure. During the axial loading in the tests, the strain rate was alternated between 2 predetermined rates that were recommended in an earlier work. On the basis of the results, we examined the effects of methane hydrate saturation and confining pressure on the strain-rate dependence of triaxial compressive strength

Effects of Methane Hydrate Saturation and Confining Pressure on Strain-Rate Dependence of Artificial Methane-Hydrate-Bearing Sediment in Triaxial Compression Test

In this study, drained triaxial compression tests were conducted on artificial methane-hydrate-bearing sediment samples under various conditions of methane hydrate saturation and confining pressure. During the axial loading in the tests, the strain rate was alternated between 2 predetermined rates that were recommended in an earlier work. On the basis of the results, we examined the effects of methane hydrate saturation and confining pressure on the strain-rate dependence of triaxial compressive strength

Interference of production between two wells during a one month circulation test at the Hijiori Hot Dry Rock test site

In 1995, a one-month circulation test (Exp.9501) was carried out with HDR-1 as an injection well and HDR-2 and HDR-3 as production wells at the Hijiori HDR site in Yamagata prefecture, Japan. There are two reservoirs in a high temperature granite at the site. Exp.9501 was the first circulation test to evaluate characteristics of the deeper reservoir at about 2200 m deep and was a preliminary test for the subsequent two-years circulation test. The interference between the two reservoirs was observed because of water level changes in production wells. This observation was simulated by using a wellbore heat transfer ( WBHT) code and concluded that this could occur when downhole pressure changed by heating up of the wellbore. Geochemistry of the produced fluid support this conclusion

Review of Fundamental Properties of Gas Hydrates: Breakout Sessions of the International Workshop on Methane Hydrate Research and Development

The International Workshop on Methane Hydrate (MH) Research and Development (the Fiery Ice Workshop) began in 2001 with the goal of promoting laboratory and field research collaborations and providing a forum to share new knowledge on MH pertaining to coastal stability, climate change, and energy. Ten workshops have been held over the past 15 years in different countries. Each workshop has included presentations on national programs and policy areas, and new research, along with breakout sessions that focused on current key topics. Two or three concurrent breakout sessions were conducted twice during each workshop. In this paper, we review the breakout sessions on hydrate fundamental properties with the goal of identifying the major accomplishments and changes in hydrate science and engineering related to determining fundamental MH properties over the past 15 years