Determination of Reservoir Flow Units from Core Data: A Case Study of the Lower Cretaceous Sandstone Reservoirs, Western Bredasdorp Basin Offshore in South Africa

The overarching aim of this study is to use core measurements of porosity and permeability in three wells (MO1, MO2, and MO3) to generate a scheme of sandstone reservoir zonation for identification of flow units in the E-M gas field of the Western Bredasdorp Basin Offshore in South Africa. The evaluation method began by establishing rock types within a geological framework that allowed the definition of five facies, grouped as facies A, B, C, D, and E. Facies A was recognized as the best petrophysical rock type. In contrast, facies E was recognized as impervious rock. The results of independent reservoir classification methods were integrated to identify flow zones that yielded positive results. The results ultimately culminated in a zonation scheme for the Basin. Twelve flow zones were identified and were broadly classified as high, moderate, low, very low, and tight zones. The high zone was characterized by pore throat radius of >= 10 mu m, flow zone index (FZI) of >= 5.0 mu m, and flow unit efficiency (FUE) of >= 0.8. In contrast, very low efficiency zones had pore throat radius and FZI of < 2 mu m, and FUE of <= 0.2. The high-efficiency zones were comparable to facies A and the tight zone to facies E. Facie C provided sand-sand contacts that allowed flow between the zones. One high, two moderate, four low, and five very low efficiency zones were identified. The plot of FUE can be compared directly with flowmeter logs. The results obtained from this study will serve as an input parameter for reservoir studies in the western Bredasdorp Basin.

Automated summary

The study aimed to generate a sandstone reservoir zonation using core measurements of porosity and permeability in three wells in the E-M gas field offshore South Africa. The evaluation identified five facies and integrated multiple reservoir classification methods to identify twelve flow zones, ranging from high to very low efficiency. The results will serve as input parameters for further reservoir studies in the Western Bredasdorp Basin.