Integration of geological and petrophysical studies for the evaluation of reservoir heterogeneities in carbonate sequences: case study from Permian–Triassic reservoirs in the Persian Gulf

This study integrates the results of petrographic studies of core samples and thin sections with petrophysical data for the evaluation of heterogeneities in the distribution of reservoir properties in the Upper Dalan and Kangan formations. Reservoir rock types, hydraulic flow units, and reservoir zonation of these formations are determined in a sequence stratigraphic framework. Accordingly, 7 rock types and 8 hydraulic flow units are defined using the petrographic evidence and flow zone indicator values, respectively. Based on the Lorenz approach, 15 reservoir, barrier, and baffle zones have been differentiated. Among the defined rock types, PRT1 (compacted anhydrite) has lowest reservoir quality, and PRT7 (dolomitized packstone and grainstone) has highest reservoir quality. A combination of depositional facies characteristics and diagenetic alterations controlled the reservoir properties in these formations. There are one reservoir and one baffle zone in K1 unit, two reservoir zones and one speed zone in K2, one reservoir, baffle, barrier, and speed zone in K3, and three reservoirs, two baffle, and one barrier zone in K4 unit. All macroscopic and microscopic heterogeneities are determined in sequence stratigraphic framework. Results showed that non-reservoir units of Permian–Triassic formations are concentrated within the RSTs (regressive systems tracts) of UDS3 and KS1 sequences. On the other hand, reservoir zones correspond to KS2 and UDS4 sequences.