Abstract
A study has been performed to delineate the spatial distribution of the reservoirs and to infer reservoir rock properties in the Amarume oil field. Reservoir rocks consist of lenticular sandstones which are considered to be sediment gravity flow deposits of Neogene. Productive sandstone reservoirs lie approximately 900m below the surface and vary from 5m to 20m in thickness. 3-D seismic data was processed carefully and the filter operator which matches the seismic data to VSP data was applied to time migrated 3-D data volume to compensate for the phase shift. The reliable information of acoustic impedance was extracted from 3-D seismic data by lithologic inversion. It provided us the spatial distribution of thin sandstone reservoirs. The lateral variation of acoustic impedance observed in each sand reservoir suggests that the reservoir rock properties such as porosity change laterally. P-wave and S-wave velocity tomograms between two wells were derived from cross-well seismic data by traveltime inversion and Vp/Vs ratio profile was estimated. The resultant P-wave velocity tomogram was generally consistent with the well log data. Its resolution was less than that of the velocity profile derived from 3-D seismic data. However, cross-well seismic data provided both P-wave and S-wave velocity information which can be powerful tools to infer the reservoir rock properties.
