SEGJ Technical Conference

Application of seismic reflection survey to detect methane plumes in seawater

Abstract Methane plumes can be an effective indicator of the existence of methane hydrates and natural gas reservoirs. In this study, we tried to examine whether we can detect methane plumes from seafloor by a seismic reflection survey. First we conducted numerical simulations of P-wave propagation and found out that we can detect methane plumes under the frequencies used in a seismic reflection survey. Then we processed the 2-D seismic data acquired in Tokai-oki to Kumano-nada and found three strong reflection events at seafloor shaped like a column. Considering the surrounding seafloor topography and the existence of multiple reflection surfaces, we concluded that it is highly possible that the detected reflection events are methane plumes. Moreover, considering the strong CDP stacking effect in the data acquired by main streamer cables, we proved that using data from mini streamer cables or limiting the offset distances of main streamer data is appropriate for detecting methane bubbles.