Depositional and Diagenetic Controls on Carbonate Reservoir Distribution - A Study in Minagish Formation, Burgan Field, Kuwait

The Lower Cretaceous Minagish Formation in the Greater Burgan Field of Kuwait was deposited in a carbonate ramp. The reservoir facies are dominated by a mixture of ooilitic and peloidal grainstone/packstone deposited in an ooid shoal complex. Diagenesis has generally reduced interparticle porosity and increased tortuosity, but it also has increased porosity at places. An integrated reservoir characterization was undertaken to understand the complexity in the distribution of reservoir facies. Depositional facies within the Middle Minagish were described from 1600 feet of conventional core. Three 3rd order hemicycles and other higher frequency cycles were interpreted from sequence stratigraphic analysis. The distribution of the facies in the cored intervals of these stratigraphic units helped determine the paleogeography. The diagenetic characteristics and paragenetic sequence were also interpreted. A comparison of the facies with rock types based on Flow Zone Indicator (FZI) highlights intervals where the depositional facies have undergone significant diagenetic changes. The areas where the original porosity was reduced because of cementation and compaction or were improved due to leaching of carbonate grains were mapped. Areas that escaped significant diagenetic effects were also identified. This integrated study was useful for understanding the Middle Minagish reservoir and will guide future infill drilling.