Fluid flow, gas accumulations, and gas hydrate formation in Kumano forearc basin determined by seismic reflection interpretation and well data correlation

A marine three dimensional (3-D) seismic reflection data set reveals a gas hydrate related bottom simulating reflector (BSR) within Kumano forearc basin, offshore Japan. Well data collected from Site C0002 within the surveyed area provides information on the physical and chemical properties of basin sediments and allows for correlation with the dipping sedimentary layers imaged in the dataset. Calculation of gas saturations in these horizons based on Archie’s Law shows preferential concentrations within sandier horizons. Structural controls such as faults and channels affect the gas distribution and illuminate migration pathways for gas to the BSR. Correlation of the strength of the BSR amplitude with the physical and chemical properties of the dipping stratigraphic horizons that are intersected by the BSR, determined by well log and core data, reveals the applicability of BSR amplitude maps in determining locations of elevated gas hydrate and free gas concentrations away from the wellbore.