Gas Hydrate Seismic Identification and Characterizations in X Basin, West Sulawesi

Abstract

Gas hydrate is solid solution which is formed when gas molecules were trapped in crystal lattices that is formed by water molecules at low temperature and high pressure. So that gas hydrate commonly found in permafrost and deep water ocean along continental margin. In Indonesia, gas hydrate can be found in deep ocean along subduction zone, such as Sunda Arc Basin and X Basin. X Basin is located at western Sulawesi. The presence of gas hydrate in nature can be represented by Bottom Simulating Reflector (BSR) on seismic section. BSR occur if gas hydrate bearing sediment and gas/water bearing sediment below has a negative contrast acoustic impedance. Those negative value is caused by the increasing of P- and S-wave velocity and density in gas hydrate bearing sediment. 3D seismic acquisition has been conducted in X Basin. The data was processed so gas hydrate in this basin can be identified and characterized. Firstly, the preliminary seismic data processing was conducted to produce a good quality seismic section/gathers. Secondly, this seismic section/gathers are developed by using advance seismic processing, such as seismic attributes, and AVO methods. Unfortunately, there is no well log data for this study, so the identification and characterization has been done as an estimation without an accurate validation. Seismic section/gathers in this study give information about the presence of gas hydrate. BSRs can be seen clearly almost in every along the crossline direction and they can be used as preliminary identification. Furthermore, RMS amplitude slice section and apparent polarity resulted in the same way. Through the seismic attribute method, gas hydrate bearing sediment velocity can be estimated around 2000 m/s with 100 m of thickness.