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Herein the relationships between porosity (Ф) and permeability (K), reservoir quality index (RQI) and flow zone indicator (FZI) were further verified and used to evaluate the selected reservoirs. This work is aimed at presenting porosity dependent equations for formation evaluation, through; (a) modification of traditional equations and (b) generation of curves/models for the estimation of K, RQI and FZI based on three fundamental ideas to aid the evaluation of the reservoirs flow units. Two reservoirs (R-M and R-N) were correlated across three wells (R-Da, R-Db and R-Dc) in Ritchie’s Block, offshore Niger Delta. The equations (Tixier’s, Timur’s and Coates’) for K determination and the expressions for RQI and FZI were modified and used for the evaluation of hydrocarbon potential of the two reservoirs mapped across the selected wells. Three porosity dependent equations suggested for use in sandstone units were presented for each of K, RQI and FZI. These equations were used to evaluate and compare these parameters each in three different ways and suggest that the reservoirs have good flow units. The estimated average porosity of the two reservoirs is 0.24, consequently, the values of averaged K were estimated at 1721mD, 2343mD and 1969mD for Kmtx, Kmtm and Kmc respectively. Similarly, the corresponding values of RQI and FZI were estimated at 2.66μm, 3.10μm and 2.84μm (RQIaa, RQIab and RQIac) and 8.42μm 9.82μm and 9.01μm (FZIaa, FZIab and FZIac) respectively. Models in form of curves that show the relationships between the evaluated parameters and porosity were presented. In a way to combine the three expressions for each of the parameters, the average of the values for RQIaa, RQIab and RQIac and the average of the corresponding values for FZIaa, FZIab and FZIac were determined. Hence, RQIaverage and FZIaverage were plotted against porosity to help generate a combined quick-look model for RQI and FZI prediction. With this model, the porosity of 0.24 corresponds to RQI of 2.95μm and FZI of 9.00μm respectively. Overall, the evaluated reservoirs were confirmed to have hydrocarbon with very good values of K, RQI and FZI. Significant rates of hydraulic conductivity and hydrocarbon recoveries are anticipated within the reservoirs (R-M and R-N) across the three wells and as such, hydrocarbon volumetric estimation is encouraged. A sensitivity analysis was carried out and shows that the change in tortuosity factor does not seem to have a significant influence on the results. Therefore, an averaged tortuosity factor of 0.8 was used in the equations. The expressions were also tested and compared with the results computed using the traditional equations and similar values were obtained.

Maximising Porosity for Flow Units Evaluation in Sandstone Hydrocarbon Reservoirs (A Case Study of Ritchie’s Block, Offshore Niger Delta)