THE LATE PERMIAN CARBONATES (KHUFF FORMATION) IN THE WESTERN ARABIAN GULF - ITS HYDROCARBON PARAMETERS AND PALEOGEOGRAPHIC

The Khuff Formation in the Arabian Gulf region is predominantly a shallow marine carbonate succession of Late Permian age, formed during transgressive-regressive depositional cycles. It varies considerably in thickness (from 500 to 975 m) and in reservoir quality. The formation proved the presence of large volumes of gas in Saudi Arabia, Bahrain, Qatar, Iran and United Arab Emirates and minor oil in Saudi and Omani fields. Reservoir characteristics indicate that the principal hydrocarbon accumulations lie in the subtidal to intertidal reservoir lithologies. Primary porosity and permeability tend to be low, but may be enhanced by a system of open fractures, thus making the Khuff sequence a good to very good reservoir. The source of the gas is either from Silurian shales or is indigenous to the Khuff carbonate itself The anhydritic shale of the Lower Triassic Sudair Formation forms an excellent seal.