Abstract

Petrophysical evaluation of carbonate reservoir is always a challenging task. The degree of difficulty increases as the inherent heterogeneity increases in the reservoir pay due to its mineralogy and pore structure. This study investigates improvement of Electrofacies classification for carbonate reservoirs by proper modeling of permeability and free fluid volume (FFV). Due to the lack of core/lab data it is always a difficult task to calibrate the NMR permeability with the in-situ permeability, which plays an important role for the interpretation of flow ability of a pay zone. Porosity, FFV, Permeability and effective reservoir thickness (He) are related to the reservoir quality in terms of its flow potential. The overestimation or underestimation of permeability, FFV and effective reservoir thickness affect the prediction of reservoir quality. The Formation Tester pretest mobility data can be used for re-computation of FFV and calibration of Permeability with proper cut off value. During the study it is seen that the Transverse Relaxation Time (T2) cut off can vary not only for the formation but with the reservoir/pay zone. Within this investigation, the Electrofacies modeling is also done with the statistical variation of wire line logging data sets such as Gamma Ray, Density, Neutron, Computed secondary porosity fraction, Calibrated Permeability and FFV over set intervals. The modified Electrofacies classification also supports the flow ability (Productivity Index) of the pay zones of the study area.