Investigation of the Impact of Diagenesis on Reservoir Quality in Carbonate Reservoir: A Case Study

Abstract

Abstract Diagenesis can enhance, preserve or degrade the reservoir quality by changing its fabric partially or completely as it will affect directly the porosity and permeability. It is anticipated that by understanding the impact of diagenesis and integrating it with the depositional settings and sequence stratigraphy will represent a powerful tool for predicting a spatial distribution of reservoir quality in carbonate reservoir located offshore Abu Dhabi, United Arab Emirates. The study is based on sedimentological core descriptions and petrographical analysis of thin-sections for selected cored wells at field-scale. It will enable a semi- deterministic approach for the prediction of the key facies across the field. It will then be integrated with the different diagenetic processes that have been defined with respect to different relative time events. A diagenetic sequence made of 14 different processes, which are either enhancing or degrading reservoir quality, has been defined. In parallel, 3rd and 4th order sequence stratigraphy are defined using lithofacies association and allow determining a depositional framework at field scale. Combining depositional settings with diagenetic evolution enables to define how the rock properties evolved and where are located the better quality rock in the reservoir. The reservoir quality is controlled by the depositional environment, which controls the subsequent diagenetic processes. Hence, it is important to understand the lateral and vertical facies distribution as well as the different type of diagenetic alterations in order to have a clearer image of the spatial variation of the reservoir quality. With the help of this acquired knowledge the geologist will be aware of the reservoir limitations and could predict its behavior with time.