RESERVOIR CHARACTERIZATION USING SEISMIC AND WELL LOGS DATA

Abstract

This study represents the delineation of gas sand reservoirs using seismic data interpretation and well log evaluation in LILY Field (Pseudo Name), Western Offshore Basin, India. The integrated study has incorporated three phases. The first, Seismic data Interpretation, which includes mapping of discontinuities and horizon to produce sub-surface time and depth structure maps, different seismic attributes for prospect identification and Coloured Inversion technique for a better allocation of reservoirs. The second phase is well log interpretation which includes interpretation of well log signatures, generation of Cross-plots, Geo cross-plots and classification of Electrofacies in order to define reservoir zones with a higher accuracy. Finally, the estimation of formation properties i.e. Porosity, Water Saturation, Hydrocarbon Saturation and Net to gross for the target reservoir zones. The seismic section and structure map exposed four way dip closures in the field, which resemble to the crest of anticlines with a promising good hydrocarbon accumulation at a depth of 850m.The extensive discontinuities F1, F2 and F3 discontinuities, facilitate suspected hydrocarbon prospects. The discontinuities F2 and F3 were falling in our area of interest were considered for interpretation. Five horizons were mapped in this study among which the two horizons H2 and H4 were taken into account for further seismic interpretation. Six wells were evaluated and seven markers were outlined. The seismic and well log interpretation disclosed that the sand zones tangled directly with the bright spots (hydrocarbon indicator) on the seismic sections as well as on attribute maps. The formation parameters Porosity, Water saturation and Net to gross calculated were nearly equal for the LILY reservoir sands with average porosity values of 19-26%, water saturation of 38-50% and average Net to Gross of 49-53%.