RESERVOIR CHARACTERIZATION USING 3D SEISMIC MODELING, WELL LOG PARAMETERS AND ROCK PHYSICS OVER “TOBOL FIELD”, NIGER DELTA.

Abstract

The need to improve the physical understanding of seismic information through rock physics which provides a way of relating elastic properties such as the Primary Velocity (Vp), Secondary Velocity (Vs), Acoustic Impedance (AI), LambdaRho (λρ), MuRho (μρ), and Bulk Modulus (K) to measured physical properties within reservoirs is a core focus for higher exploration success rates and improved oil recovery. The data-base for this study consists of 3-D seismic data, checkshot data, suite of wire-line logs comprising; gamma ray logs, resistivity logs, and sonic logs. Well correlation across five (5) wells was carried out to show the continuity of a reservoir. Petrophysical analysis was done to generate parameters such as; Total Porosity, Effective Porosity, Permeability, Volume of shale, Formation factor, Hydrocarbon saturation and Water saturation for two (2) reservoirs. The reservoir is fault assisted with 46 faults and two (2) horizons mapped across the seismic sections, also structural maps (Time and Depth maps) and property models were generated. Rock physics analysis was carried out to correlate the result of petrophysical analysis and seismic interpretation and modeling. The Rock physics analysis includes Rock physics crossplot of elastic parameters against calculated reservoir parameter (e.g. Vp against Porosity to test for the degree of cementation of the formation, Vp against Vs to delineate lithology, LambdaRho against MuRho for identification of fluid content) and Gassmann fluid substitution for Porosity prediction. The result shows Porosity ranging from 26.7 % to 33.6 % for Petrophysical analysis, 27.4 % to 30.2 % for Gassmann Fluid Substitution and 15% to 40% for the modeled Porosity. This indicates a good to very good porosity rating for the reservoirs. Therefore, the Gassmann Fluid Substitution porosity result has been able to validate the results of the petrophysical parameters and that of the models.