GEOLOGY OF THE PERMIAN SUPER-GIANT GAS-RESERVOIRS IN THE GREATER PERSIAN GULF AREA

The Permian Dalan and Khuff Formations contain extensive gas reservoirs in the Greater Persian Gulf area. The Permian transgressive sea covered a vast area in the Middle East, and deposited a fairly thick sequence of shallow, epicontinental carbonates. These carbonates were deposited unconformably on Lower Paleozoic rocks in western Iran and on the basement in Central Arabia. The term "Khuff Formation " has been widely used by oil companies in the region, but its equivalent, the Dalan Formation, is a new name currently being used in Iran. The Permian Basin was an elongate trough, trending NW-SE, parallel to the Cretaceous-Tertiary Zagros geosyncline. The deepest part of the Permian Basin was in the extreme SE portion of the trough, in the vicinity of the present Oman Mountains, in which nearly 6,000 ft (1,830 m) of Permian sediments were deposited. Porosity and permeability are generally low in these carbonates. However secondary fracture porosity and dolomitization are commonly developed throughout these rocks. Permian reservoirs are capped by impervious strata, and the gas seems to be sourced from within the Permian section.