--> Abstract: Interplay of Tectonics, Depositional Facies and Fracture Network Development in Sudair Formation, Kuwait: Implications for Hydrocarbon Prospectivity, by Ahmad Al-Eidan, Riyasat Husain, Terry O'Hearn, S. K. Bhattacharya, Abdul Aziz Sajer, and King Hoi Lau; #90039 (2005)

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Interplay of Tectonics, Depositional Facies and Fracture Network Development in Sudair Formation, Kuwait: Implications for Hydrocarbon Prospectivity

Ahmad Al-Eidan, Riyasat Husain, Terry O'Hearn, S. K. Bhattacharya, Abdul Aziz Sajer, and King Hoi Lau
Kuwait Oil Company, Ahmadi, Kuwait

Regionally, the Sudair Formation of Early Triassic age is regarded as the top seal for underlying Khuff reservoirs. In Kuwait, recent high-temperature high-pressure exploration wells have established measured flow of hydrocarbons to surface from the Sudair.

Thickness variations, lithofacies parameters and reservoir properties in Sudair Formation follow a predictable trend. In eastern Kuwait across the crest of the Burgan Arch and its northern extension, the Sudair is thin and characterized by a high percentage of anhydrites, poor reservoir facies and low gas readings on mud logs. The Sudair was deposited under very shallow subtidal to supratidal conditions over the high as indicated by dolomitized algal laminites with displacive anhydrite and by rare interbedded dolomitized ooid grainstones.

In western Kuwait in an inner ramp lagoonal setting, it is characterized by greater thickness, a lower percentage of anhydrites, improved reservoir characteristics and higher gas readings. To the west of the arch, a restricted embayment developed resulting in the deposition of interbedded carbonates and subtidal evaporites under restricted inner ramp conditions. Reservoir quality within the dolomudstones is poor due to pore-filling anhydrite. Intercrystalline porosity ranges up to 5.4%. Matrix permeability is very poor, but fracture-related permeability within the dolostones ranges up to 3.3 mD.

Syn-depositional tectonics controlled depositional environment and lithofacies distribution. Regional stress regimes and subsequent tectonics controlled the fracture network which developed within the brittle dolostones. Linkage of tectonics, depositional facies and fracture development can be utilized in a predictive manner for assessing reservoir quality and hydrocarbon potential within the Sudair.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005