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Department of Geology, University of Kuwait

ABSTRACT

The Albian Mauddud Formation is an important calcarenitic carbonate reservoir rock in Kuwait and north Arabian Gulf. It is widely spread in the Middle East, where it can be traced from Rubel Khali in southern Saudi Arabia up to Iraq. In Kuwait, it ranges in thickness between a few metres and 98 m. Nine microfacies associations are recognised within the Mauddud Formation in Kuwait, namely: Orbitolina-Trocholina biomicrite, Orbitolina-Trocholina pelsparite, Ovalveolina-miliolid biomicrite, shelly biomicrite, argillaceous biomicrite, dolomitic biomicrite, dolomite, sandy dolomitic Orbifolina biomicrite and carbonaceous siltstone. The pronounced diagenetic alterations in the Mauddud Formation are mainly recrystallisation, rim cementation and dolomitisation. The porosity which could be identified is mainly leaching and intercrystalline whereas intergranular and intragranular porosities are of less magnitude. The sediments constituting the Mauddud Formation are considered to have been deposited in a shallow marine environment with scattered shell banks. They formed during a regressive depositional phase which encountered an influx of detrital material from a nearby land mass in its early stages. The pronounced thinning of the Mauddud Formation, as well as the smaller number of microfacies in southern Kuwait is either due to: (a) deposition over pre-existing structural highs or, (b) less subsidence during deposition in the south compared to more subsidence northward or, (c) erosion of the upper Mauddud in the south.