Khuff formation Permian-Triassic carbonate in the Qatar-South Fars arch hydrocarbon province of the Persian Gulf

Since the 1948 discovery of prolific gas reservoirs in Bahrain, Middle East explorationists have been interested in the Khuff Formation (Permian-Triassic carbonate). Several supergiant gas fields (reserves above 10 tcf) have been found in the region. North of the Persian Gulf very large gas fields have been discovered in Permian strata of south Iran, especially in coastal Fars, such as Kangan, Dalan, Nar, Aghar, Bandubast, Mand, Varavi, Asaluyeh, as well as in the Persian Gulf. Qatar-South Fars province contains light and heavy crude oil ( Bashari, 1988), in addition to being one of the most important gas provinces in the world. Qatar’s North field is the largest of all the giant Khuff gas reservoirs, with total reserves of 436 tscf and field life of around 200 years at planned production rates. It covers an area of 6000 km2. The gas reservoirs are found at shallow depth in the Khuff, usually between 2470 and 2830 m below sea level (Al-Marri and Al-Bader, 1989). In fact the field is even bigger than indicated because its reservoir extends across the political boundary in the Persian Gulf under Iranian waters (South Pars Field). There are efforts to evaluate extensions of the field in Qatar waters, especially to the east and southeast of production areas. There is a strong probability that current reserves in the North field will increase as a result of such work (Al-Attayah, 1998). In 1992, Iran discovered the supergiant South Pars field, in the Persian Gulf, close to Qatar’s North field, (Fig.1). South Pars has reserves estimated at 436 tscf. (Petropars, 2005). The South Pars field is formed by an extremely large open periclinal structure. North field and South Pars fields overlie the broad Qatar arch, which subdivides the Khuff depositional basin, into two basins located north west and south east of the arch. This paper describes the Khuff carbonates distributions in terms of Lithostratigraphy- Biostratigraphy, (diachroneity) of this formation and also reservoir development of Khuff formation.