Guided facies modeling using 3d seismic and well data: Soft-conditioning to geomorphologic objects

Greater geologic realisim is obtained when simple interpreted trends from 3D seismic were used for litho-facies modeling. Images slices from 3D seismic attributes provided soft-guidance to lateral arrangement of depositional reservoir facies. These are calibrated to wells establishing a relationship from which litho-facies distribution is predicted between well and extrapolated away from wells. It was observed that although well data was faithfully honored, as were trends in the 3D seismic data, all the simulation outcomes generally lacked geological meaning & realism. We applied principles of seismic sedimentology of (Zeng & Henz, 2004) to interpret & map geomorphic & depositional features from 3D seismic data over Tobaz field. The geology of reservoirs comprises deposits of lower coastal plain, fluvial with minor marine influence of sub-tidal to inner shelf environment of Uppermiddle Miocene age. Correlation of reservoir sand packages between logs, core and seismic signatures was severely hampered by core limitation and coal masking of reservoir rocks on seismic. The litho-facies model of BB field is obtained using object modeling of deterministic geomorphologic expressions on seismic attribute images to guide facies trends. This approach is more geologically meaningful, and it shifts emphasis from the orthodox methods of analyzing vertical seismic sections & well logs to a more lateral area-wide synoptic characterization of geologic features controlling reservoir rocks. It leads to reduction of uncertainties associated with estimates of reservoir hydrocarbon in-place & production potential.