Dolomite Microfacies and Diagenetic Controls over Porosity in Palaeozoic Kinta Limestone, Perak, Malaysia: Based on Petrographic Properties.

Carbonate reservoirs have become one of the key targets of hydrocarbon exploration. In fact, carbonate reservoirs contributed to 50% of oil production. The reservoir properties evaluation can be very complex to understand when it encounters with dolomitization. Most of the ancient dolomites have associated with changing of rock texture through diagenetic processes such as dissolution, recrystallization, precipitation, mineral stabilization and multiphases of fracturing. Thus, qualitative and quantitative data helps to improve the study of dolomite characterization. The aims of this paper is to identify the dolomite groups in Paleozoic Kinta Limestone and discuss on how diagenetic alterations influence porosity in dolomites microfacies. Kinta dolomite is identified as epigenetic dolostone and believed to form by the replacement along post-depositional lineaments of faults and fractures. The dolomite in Kinta Valley is classified as secondary dolomite. There are thirty (30) samples were collected from quarries in Kinta Valley to perform a petrographic analysis. The analysis is conducted by studying the photomicrograph taken from the optical and cathodoluminescence microscopes. Five (5) types of dolomite microfacies are recognized, which are Dolo-I (Microdolomite), Dolo-II (Sucrosic Dolomite), Dolo-III (Fabric Destructive Fine Crystalline Dolomite), Dolo-IV (Fabric Destructive Coarse Crystalline Dolomite) and Dolo-V (Saddle Dolomite). The dolomite facies are grouped into cement and replacive dolomites. The replacive dolomite is associated with lower porosity than cement dolomite. The variation of porosity values in different types of dolomite can be linked to different diagenetic processes. Our data affirm that diagenetic process of pre-dolomitization has destroyed porosity, while post-dolomitization has created porosity. [ABSTRACT FROM AUTHOR]