Estimation of Permeability of Carbonate Gas Reservoirs Using Nuclear Magnetic Resonance (NMR) Log and FZI-Stonley Method

Permeability is one of the most important reservoir parameters for reservoir expansion , indicating the ability of reservoir rock to convey fluid. Due to the heterogeneity of the reservoir, the permeability estimation is always calculated with a large error. To calculate permeability, this paper is divided into two general sections. In the first part, NMR relaxation groups(equivalent to hydraulic flow units or HFUs) were determined using nuclear magnetic resonance logs. The advantage of this method is to overcome the heterogeneous property of the reservoir. Relaxation groups were obtained using the FZI-Stonley method, in which petrophysical interpretation was first performed by petrophysical logs, and the rate of stoneley wave velocity in the rock matrix was determined using intersecting logs and mathematical relationships. The advantage of this method is to overcome the heterogeneous property of the reservoir. Then, permeability was obtained for each of the relaxation groups using FZI-Stoneley method. This is how petrophysical interpretations were first made by petrophysicals and the velocity of the Stonley wave in the rock matrix was determined using intersecting diagrams and mathematical relationships. Then, using core data and petrophysical evaluation outputs, the adaptation index factor for different minerals of each relaxation group was calculated and finally, using mathematical equations, the quantitative permeability was determined continuously for each of the hydraulic flow units concept. Relaxation groups were calculated. In this study, several IMFs were identified for each mineral, thus identifying facies (hydraulic flow units) and based on the hydraulic flow units for each mineral, different IMFs are obtained. The main advantage of the above method is that by recording the intrinsic property of the Stonley wave affected by the permeability, a continuous log of the permeability changes across the well can be obtained which also considers the heterogeneity of the reservoir.