#TITLE_ALTERNATIVE#

• Main Author: BAHAR (NIM 32302003), ALFIAN
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/25336
• Institution: Institut Teknologi Bandung

An indication of gas hydrate in sub marine sediment in Sunda forearc basin was reported by researchers from BGR (Federal Institute for Geosciences and Natural Resources), Hannover, Germany in 2001. Gas hydrate was detected from the appearance of BSR (Bottom Simulating Reflector) on Ginco seismic section survey (Geoscientific investigations on the active convergence zone between the east Eurasian and Indo-Australian Plates along Indonesia), during the Sonne SO137 cruise (1999).<p> <br /> An integrated analysis of seismic data has been carried out in this research in order to characterize gas hydrate bearing sediment in the Sunda forearc basin area. Seismic re-processing, AVO analysis and seismic attenuation analysis have been conducted to study seismic characteristics of gas hydrate bearing sediment and to estimate the initial volume of in situ gas hydrate in this area.<p> <br /> The interpretation of BSR and seismic interval velocity profile shown that BSR is characterized by a strong negative reflection and a decrease in velocity from the sediment above BSR to the sediment below. The interval velocity section also shows a high velocity anomaly above BSR. The thickness of the high velocity anomaly is approximately 200 m. The zone of high velocity anomaly is interpreted as hydrate bearing sediment. BSR is the base of this layer. This layer is also characterized by high seismic attenuation.<p> <br /> The map of the lateral BSR distribution shown that gas hydrates are mainly detected in the center of Sunda forearc basin along the Mentawai fault zone. Based on the AVO analysis of BSR reflection, I conclude that there is only little possibility to find free gas in the sediment below BSR.<p> <br /> Based on the interpretation of gas hydrate indication (BSR) on seismic sections, a model gas hydrate accumulation has been made. This model is not significantly different from the classic oil and gas trap model. The gas formed within the source rock at a certain depth is envisaged to migrate upward through a dipping layers that is permeable or through a fault / fracture to the sediment layer in hydrate stability zone. The interaction between gas and water in the rock pore space that exists within a hydrate stability zone will form gas hydrate crystal structure. If the gas hydrate concentration is significantly high and fills out the rock pore space, the sediment rock will become impermeable and resist further gas migration. This condition will cause the accumulation of free gas below the gas hydrate stable zone. Here, the fault zone, dipping layer and anticline structure are concluded to become the key factor for the existence of gas hydrate in the forearc Sunda basin area.