イソブタンハイドレートコアを用いた注入実験システムの開発と地盤改良剤によるメタンハイドレート層の安定化における分解ガスの挙動の解明

抄録

Methane-Hydrate（MH）, has been considered as a new resource of natural gas in the future. However, in the past several field production tests, serious sand problems occurred during the depressurization, because the sand grains in shallow formations without intensive compaction lost their solidarity, separated from each other, fluidized and migrated into the production well. To solve this problem, we proposed a method to stabilize a MH reservoir by grout material, and have verified its potential through a series of experiments using TBAB hydrate under normal pressure in our past research. However, in the case of real MH reservoirs, MH dissociation would occur during the grout operation, generating methane gas in pore spaces, which may interfere with grout injection, or push the grout materials in the pores back to the wellbore. Since TBAB hydrate does not generate any gas during its decomposition, we tried to use iso-Butane and its hydrate（i-BH）as a new alternative hydrate, which can be generated at a much lower pressure condition than MH. In this research, we developed the experimental apparatus system that can generate i-BH cores with accurate saturations, inject inhibitor and/or grout materials and measure their physical properties. Then we conducted a series of experiments to investigate the behavior associated with gas generated during chemical injection, including the change in gas and liq- uid production rates. Finally, we measured the physical properties of the grouted i-BH cores after curing in the presence of generated gas, such as permeabilities and mechanical strengths. As the result, the generation of gas phase did inter- fere with chemical injections, push the grout materials out of the cores, and cause heterogeneities like wormholes, but the grouted i-BH cores still had sufficient permeabilities and approximately reached 2/3 strengths of non-gas generated cores at the same operation conditions.