DEPOSITIONAL CHARACTERISTICS OF PALEOZOIC KHUFF FORMATION IN THE PERSIAN GULF AND THEIR RELATION WITH HYDROCARBON ACCUMULATION

Enormous natural gas resources have been found in the Paleozoic in the Persian Gulf area. Based upon regional tectonics, we described, in this paper, the sedimentary characteristics of the Paleozoic Khuff Formation and a sedimentary model for "carbonate platform with large ramp" was established. In this region, oil and gas accumulations are jointly controlled by the combination of "source-facies-potential". The result also shows that platform facies zone and platform edge facies zone are well developed in the Khuff Formation. Evaporate, restricted platform, open platform, platform margin shoal and reef are developed in an order from northwest to southeast. Sedimentologically, the Khuff Formation is characterized by interbedded limestone and dolomite intercalating gypsum and salt layers. Open platform, platform margin shoal and reef are favorable facies belts for hydrocarbon accumulation. The size and distribution of Qusaiba hot shale, as the hydrocarbon source kitchen, control the oil and gas distribution and resources potentials in the region. The gypsum-salt layers in the Khuff Formation control the vertical and plane distribution of oil and gas. The enriched zone of oil and gas is obviously controlled by sedimentary facies distribution of the Khuff Formation. The low potential basement highs and the salt arches surrounding the hot shale hydrocarbon generation kitchen are the favorable oil and gas accumulation areas. In view of the above, the reservoir property, petroleum migration and preservation are the key to hydrocarbon accumulation in the region. By data analysis, a large number of salt arch-related anticlinal traps in Khuff Formation have been found well developed in the southern gulf salt basin. The combination of Silurian hydrocarbon source rocks and the excellent traps in Khuff Formation provided superior conditions for hydrocarbon accumulations. Huge amount of resources is expected from the salt arch structure belt, which is a favorable exploration target in the Paleozoic of the Persian Gulf.