Volume contents of gas hydrates generated in porespace may change properties of elastic wave propagation in rock.One can anticipate estimating the volume of the generated gashydrates, when elastic velocities in this rock are measured bymeans of either seismic data processing or well log.The wave propagation has historically been studied under thecondition of two phases, i.e., matrix and fluid in the pore of thematrix. Once the gas hydrate is generated in the pore space, anadditional solid property to the two-phase model shall be takeninto the accunt to study this wave propagation. New numericalmodel is introduced to examine the relationship between volumeof gas hydrate contents and velocity change of elastic wave. Themodel is namely the extended Biot theory dealt with the threephases; matrix, fluid and second matrix to explain the laboratoryvelocity measurements of three-phase condition.The laboratory specimens filled in an acrylic resin case equippedwith velocity sensors are composed of glass beads as the matrix,Kibushi clay as the second matrix, and air or water in the porespace. The 3 cm sensor depth beneath the specimen surface isconsidered to be simulated the measurement at a poor consolidated porous media.This paper shows the comparison of this three-phase numericalmodel with the elastic velocity measurements.
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