Abstract

The Khuff Formation can be described as a second-order transgressive-regressive sequence. The transgressive sequence set comprises Khuff third-order composite sequences KS7 through KS5 and the third-order lowstand/transgressive systems tract of KS4. The regressive (highstand) sequence set comprises the highstand systems tract of KS4 as well as Khuff third-order composite sequences KS3 through KS1. Major Khuff gas reservoirs are associated with the second-order highstand sequence set.

Khuff analogues have been studied in the Musandam Peninsula at Wadi Bih and Wadi Hagil (Ras Al-Khaimah, U.A.E.) and are compared to well data from Abu Dhabi (U.A.E.). The outcropping carbonates of the Permian Bih and overlying Hagil formations as well as the lower part of the Triassic Ghail Formation are interpreted to be time equivalent to hydrocarbon bearing carbonates and siliciclastics of the subsurface Khuff of the Arabian Platform.

Khuff Sequence KS1 corresponds to the lower part of the Ghail Formation. The Hagil Formation comprises Khuff sequences KS2 and KS3. Khuff sequences KS4 through KS7 are interpreted to correspond to the Bih Formation. At Wadi Bih the Permian-Triassic Khuff sequence boundary SB1 at the base of the uppermost Khuff Sequence KS1 is well exposed. It is marked by a karst breccia overlain by oncoid packstones of the Ghail Formation. In Wadi Bih as well as in Wadi Hagil, Khuff sequence boundary SB3 is interpreted to correspond to an exposure surface showing mud-cracks and possible raindrop imprints. This sequence boundary also marks the boundary between the underlying Bih and the overlying Hagil Formation.

Introduction

Important commercial hydrocarbon accumulations are reported from the Permian Khuff (carbonates) and Unayzah (sandstones) Formations1,2,3. The so-called Hercynian Event, or Hercynian Unconformity separates the Lower Carboniferous ("Berwath Formation" or "Pre-Unayzah Clastics")4 and older sediments from the overlying Permian/Middle Carboniferous Khuff and Unayzah deposits. Paleozoic deposits older than Unayzah may have been partly to completely eroded on top of old basement highs like the Ghawar Arch and Summan Platform of Saudi Arabia and the Burgan Arch in Kuwait. Khuff or Unayzah sediments may unconformably overlie Devonian (Jubah or Jauf), Silurian (Qalibah: Sharawra or Qusaiba), Ordovician (Qasim: Quwarah), Cambrian, undifferentiated Cambro-Ordovician (Saq Formation), or Precambrian (Basement) sediments and metasediments3.

This content is only available via PDF.
You can access this article if you purchase or spend a download.