| Popis: |
Development of complex carbonate reservoirs requires a thorough evaluation of rock properties, especially when the reservoir has been highly influenced by diagenetic processes. Understanding the distribution of reservoir quality is a prerequisite to successful prediction of reservoir performance. This study focuses on the integration of diagenetic studies with reservoir rock-log typing. The objective was to understand the present day pore space system by evaluating the diagenetic overprint and its control on the studied reservoirs porosity, permeability and capillarity. In the cored intervals of the studied reservoirs the lithofacies indicate a high energy shallow, water platform environment prevailing during Early Cretaceous time. Both reservoir thicknesses vary between 20 and 30 feet in thickness. Average porosity and permeability are less than 20% and 20 mD, respectively. Detailed petrographic evaluation, stable isotope analysis, cathodoluminescence and fluid inclusion analysis were employed to develop the diagenetic model. The major controls on reservoir quality and diagenetic feature distribution were integrated and mapped within the sequence stratigraphic framework. Furthermore, a diagenetic facies scheme was established incorporating core description, petrography, RCA and MICP. The diagenesis evaluation was followed by a reservoir rock typing study to demonstrate the relationship between the identified diagenetic facies and established reservoir rock types using RCA, MICP and log data. Reservoir rock types were distinguished by their distinct storage and flow capacity characteristics from MICP and RCA. Multivariate statistical techniques were used to classify reservoir intervals into their reservoir rock types from the log data. Correspondence analysis was performed to corroborate relationships between the diagenetic facies and reservoir rock types. This was validated using saturation height functions within/between rock types. The results of this study will have lasting value to the asset. The geological and reservoir models being developed reveal controls and distribution of reservoir quality and can be updated and optimized with future planned data acquisition. |
