Case Study of Petrophysical Evaluation Utilizing Well Logs Data with Optimization of Reservoir Cut-off Parameters

Petrophysical evaluation of well log data is essential for the exploration and evaluation of hydrocarbon-bearing formations. Moreover, there are no standard criteria to implement cut-offs on petrophysical properties as a direction for economic decisions. In the present work, a petrophysical evaluation of well logging data from four wells in a mature oil field is performed to identify formation quality as a potential for hosting mature hydrocarbons reservoirs. Full consideration of cut-off values was taken into account. The cut-offs were estimated from well-recognized petrophysical relationships for permeability as a function of porosity, water saturation, and shale content. Results verification and calibration were also made based on laboratory measurements of petrophysical properties obtained from available core plugs in order to minimize uncertainty. Lithology analysis and characteristics revealed that the target formation is mainly sand and shale sequences. Results from well logs were in agreement with results obtained from core data. Formation effective porosity varies from 16 to 26% in all wells. A wide range of variations is observed in water saturation ranging from 28 to 57% and permeability ranging from 20 to 3300 mD. This is in good agreement with other measurements and well log analysis that show the mature formation remains to be a good hydrocarbon reservoir with significant potential.