Rock Physics Modeling of Sub-Seismic Reservoirs in Complex Depositional Systems: Case Study of SAND_K2, ‘KUTI’ Field, Deepwater Niger Delta, Nigeria

Abstract

Rock physics transformation of petrophysical properties into petro-elastic parameters, which allows sub-seismic reservoirs to be imaged from seismic data, has been carried out. The reservoirs’ lithofacies and properties were determined using available Well information. Rock physics analysis was implemented to model the seismic response of the reservoirs. This was achieved through multivariate cross-plot of petro-elastic parameters of the reservoirs. The methodology was implemented on a targeted sub-seismic reservoir SAND_K2, KUTI Field in Deepwater Niger Delta. SAND_K2 has a thickness of 32.8m, shale volume of 12%, average porosity of 33% and acoustic impedance of 4200 to 5000 (m/s)(g/cc). Presence of shale and clay minerals increases the acoustic impedance and P-wave velocity of the reservoir above 4800 (m/s)(g/cc) and 2500 m/s respectively; while decreasing its porosity and rigidity (Mu-Rho) below 36% and 6.0 (Gpa*g/cc) respectively. Effect of hydrocarbon reduces acoustic impedance below 4775 (m/s)(g/cc). Similarly, hydrocarbon effect reduces the reservoir’s incompressibility (Lambda-Rho) below 25 (Gpa*g/cc), with gas having the most effect. Rock physics modeling provided calibration data from which cut-off values of amplitude were determined for improved identification, discrimination and prediction of the lateral distribution of reservoirs away from wellbore using seismic data, thus reducing exploration risk.