Abstract

Petrophysical properties play a key role in calibrating 3D seismic attributes. This has been displayed in Carbonate reservoir in Indian Western Offshore. ELAN processing was first carried out in wells covering the entire boundary of reservoir. Mudstone, Packstone / Wackestone and Montmorillonite (main clay) have been used as matrix components in processing. Support from core data was taken in establishing the parameters for realistic results. Property maps were then generated to visualize the variations in space. The properties were superimposed over seismic structure and attribute maps for correlation. The relevant log properties (porosity, clay volume, oil saturation, net pay thickness, Net/Gross ratio and IHM) and seismic attributes were compared to establish correlation between them over gross thickness of reservoir. A gross correlation of IHM with Cosine of phase attribute was found relevant in defining the reservoir boundary. Likewise, IHM values are found corroborating with Seismic amplitude, and three types of reservoir facies (good, moderate and poor) have been identified fully satisfying geological concepts. The study shows the good quality reservoir extent suitable for drilling. FMI image has been helpful in identifying thin intervening shale layers within the reservoir, indicating fluctuation of sea levels during deposition. The image also depicts effect of diagenesis (presence of vugs, cemented vugs and few cemented vertical / sub vertical fractures). A New porosity-permeability relationship has been developed. The estimated permeability matches with the core derived permeability and also matches reasonably well with well test permeability except in regions indicating fractures. High permeability streaks within layers have also been mapped, which have caused injection water break through. Spatial variations of the permeability in the field helped in tracking direction of water movement in dynamic studies. There is a good semblance between petrophysical properties and productivity. Better reservoir facies developed in up-dip part have contributed the most. The paper signifies the contribution of petrophysics to characterize the reservoir in conjunction with seismic, geological and dynamic studies.