Seismic Identification and Characterization of Gas Hydrates in Central Sunda Margin - Indonesia

Abstract

A significant hydrate accumulation is interpreted to be present in the central Sunda margin area from seismic data acquired during the cruise of RV Sonne in 1998 conducted by BGR, Hannover, Germany. The hydrate deposits in this area are identified with the presence of a peculiar seismic signature of gas hydrate i.e. the Bottom Simulating Reflector (BSR). These seismic signatures, which are associated with the base of Gas Hydrate Stability Zone (GHSZ), are found at 450-950 milliseconds of depth below the sea floor. The BSRs are mostly distributed in the middle of fore-arc basin of the central Sunda margin, which is parallel with the Mentawai fault zone. In this paper, we present the seismic characterization of BSR interrelated with the delineation of gas hydrates distribution and estimation of gas hydrates reserve. The lateral and vertical distributions of gas hydrates are delineated using BSRs identification and interval velocity analyses above BSRs in detail. Based on the AVO (Amplitude Versus Offset) analyses of BSRs; we found the possibility of free gas trapped underneath the gas hydrate stability zone. To quantify the amount of gas hydrate, we calculate the volumetric of hydrate-bearing sediment using seismic surface interpretation and detailed velocity analysis. The volumetric of hydrate-bearing zone in this area is approximately 3,408 km. By assuming the concentration of gas hydrates in sediments is 2 % of the unconsolidated sediment volume, the estimate amount of gas hydrates is 68 km.