Dolomitization and Reservoir Characterization of the Cretaceous Qamchuqa Group, Khabaz oil Field, Kirkuk Area, Northern Iraq

Basim A. J. Al-Qayim¹*, Fuad M. Qadir¹**, and Fawzi M. Al-Biaty^2
1University of Sulaimaniah, Iraq
²Kirkuk Technological College, Iraq
*[email protected]
**[email protected]

The Lower Cretaceous (Aptian-Albian) Qamchuqa Formation, in the Kirkuk area of northern Iraq, consists of thick shelf carbonates. It is here recommended that it be raised to a group status consisting of three formations; the upper and lower Qamchuqa formations that are separated by the Sarmord Formation. The upper and lower Qamchuqa formations were deposited as platform carbonates in a wide spectrum of shelf subenvironments, whereas the Sarmord Formation consists of basinal facies. Pervasive dolomitization affected the Qamchuqa formations and their reservoir properties. This study examined cuttings, cores, and different types of wireline logs, as well as production data from seven wells in the Khabaz oil field. The analysis revealed important links between sedimentary facies, dolomitization, eustatic fluctuation and the heterogeneity of reservoir rocks. A wide range of dolomite fabrics were identified including microcrystalline, planar-e, planar-s, planar-c, planar-p, as well as saddle and non-planar types. These imply successive phases of dolomitization, which profoundly influenced the enhancement of reservoir character. Inter-crystalline microvuggy, and micromouldic porosity are the most important products of this dolomitization. Fracturing and the retained primary sedimentary fabric of the undolomitized, or partly dolomitized, facies contributes to the collective porosity and permeability of the reservoir. Linking these modes of dolomitization to the eustatic cycles of the sequence shows that part of the intensively dolomitized sections are associated with highstand episodes.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain