Wider Application of Elemental Chemostratigraphy in Carbonates: A Case Study from the Lower Cretaceous Minagish Formation, Kuwait

Florian A. Conradi¹, Taher El-Gezeeri², Kenneth Wells³, Timothy J. Pearce¹, and Michael C. Dix^4
1Chemostrat Ltd, Llanfyllin, Powys, United Kingdom
²Kuwait Oil Company, Ahmadi, Kuwait
³British Petroleum, Ahmadi, Kuwait
⁴Halliburton - Sperry Drilling Services, Houston, TX

Whole-rock elemental chemostratigraphy has been used to establish a robust, high-resolution correlation in the Lower Cretaceous Minagish Formation of west Kuwait. Four cored wells along a four-kilometer line of section were analyzed for this study. The zonation comprises two major geochemical packages, which can be subdivided further into nine geochemical units. The upper package contains minor amounts of siliciclastic material, allowing small variations in elements such as SiO₂, Al₂O₃, and Fe₂O₃ to be useful for geochemical subdivision. The lower package contains little terrigeneous detritus, and the zonation is based mainly on carbonate- and phosphate-affinity elements such as MgO, MnO, Sr, P₂O₅, and Y.
The zonation incorporates the recognition of key stratal surfaces, supported by the integration of petrographic and sedimentological data. Additionally, subtle geochemical variations have been tied to the proportions and types of allochems, matrix, and cements. This method highlights the potential of modelling depositional facies using elemental chemostratigraphic data. Furthermore, geochemical data have been used to model the distribution of tar mats, based on the occurrence of high S, Ni and V levels. The tar mats appear to occur preferentially in facies characterized by high initial porosity.
The results of this study have shown the value of chemostratigraphic data beyond its more conventional use as a correlation tool. Chemostratigraphic data, calibrated with petrographic and sedimentological data, can provide an independent means to extract information on facies from cuttings samples during development drilling.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece