地盤改良剤によるメタンハイドレート層の安定化の研究

抄録

Methane-hydrate （MH）, has been considered as a new resource of natural gas in the future. However, in the past several ?led production tests, serious sand problems occurred during the depressurization, because of the unconsolidated sand characteristic of MH reservoirs. Unlike conventional oil and gas reservoirs, MH reservoirs locate in very shallow formations without intensive compaction; MH existing in the pore space also play a role of cementing sand grains. Therefore, sand grains would lose their solidarity during the depressurization for MH dissociation, separate from each other, fluidize and migrate into a production well. To solve this problem, we have proposed a new method, which stabilizes a MH reservoir by grout material. To verify its effectiveness, we conducted a series of experiments using quartz sands, cement-grout and TBAB hydrate under normal pressure. First, we con?rmed that the grout material could prevent a sand problem from a synthesized formation without hydrate. Then, we verified that permeability and uniaxial compressive strength （UCS） could be sustained in the grouted hydrated cores. In addition, we examined the factors affecting the physical properties of grouted cores, such as grain size, hydrate saturation, salinity of formation water, temperature, concentration of grout material and additives, and curing time. Finally, in accordance with the insights obtained above, we tried to optimize the strategy to prevent the sand problem using the grout material in hydrate reservoirs, from the viewpoints of maintaining their permeability and strength （UCS）.