Diagenetic History and Its Control on Reservoir Properties in a Heterogeneous Carbonate Field, Kangan/Dalan Formation, Iran
A section of 445 m through the middle-upper Khuff Formation from three wells was selected for the study. A detailed description of the depositional facies and depositional cyclicity was first performed. The diagenetic processes were described by investigating more than 800 thin sections. A paragenetic sequence was established and the most important diagenetic processes with respect to reservoir quality were identified. All thin sections were described and categorized according to diagenetic facies. Important factors in this type of classification are mineralogy, cement type, cement volume and poretypes. The distribution of diagenetic facies will typically not correspond to the lithofacies distribution, since similar lithofacies may be subjected to different diagenetic processes, even within short distances. However, a higher-order correlation between sedimentary units and diagenetic facies can be demonstrated. The study has shown that this reservoir has been subjected to heavy diagenesis and that these processes, to a large degree, have altered the primary properties of the sediments. A better correlation between reservoir quality and diagenetic facies, rather than to sedimentary facies, can be demonstrated. The diagenetic overprinting therefore has a major control on reservoir quality distribution in the section, which therefore has important implications for the fluid-flow properties of the reservoir. The diagenetic facies have been grouped into associations according to their reservoir properties. These groups were identified with a high level of confidence on wireline logs making it possible to predict diagenesis and reservoir type outside cored sections.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain