Barremian-lower Aptian Qishn Formation, Haushi-Huqf area, Oman: a new outcrop analogue for the Kharaib/Shu'aiba reservoirs

摘要

Limestones of the middle Cretaceous Qishn Formation are exposed in the Haushi-Huqf area of Oman. These carbonates preserved reservoir properties due to shallow burial and an arid post-exhumation climate. This characteristic makes the Qishn Formation an excellent outcrop analogue for the Upper Kharaib and Lower Shu'aiba oil reservoirs in the Interior Oman basins. The aim of this paper is to provide a broad overview of results from an industry-oriented field study recently performed in the Qishn Formation outcrops belts. The comparison of these results with studies undertaken in the Northern Oman Mountains and the Oman Interior subsurface is the topic of ongoing research. The age of the Qishn Formation is middle Barremian to mid-early Aptian, the Hawar Member (equivalent) is earliest Aptian in age. The paleo-environments recorded range from the tidal mudflat to the argillaceous platform setting (outer ramp) below the storm wave base. In terms of sequence stratigraphy, four large-scale transgressive-regressive cycles of Cretaceous age (Jurf and Qishn formations) were distinguished. Sequence I, a dolomitized succession termed Jurf Formation, is the equivalent of the Lekhwair, the Lower Kharaib and possibly older Cretaceous units. Due to pervasive early dolomitization, the Jurf Formation is not further considered here. Sequence II, forming the base of the overlying Qishn Formation represents the equivalent of the Upper Kharaib, portions of Sequence III the Hawar Member, and Sequence IV is the equivalent of the Lower Shu'aiba. At least two lower orders of cycles are superimposed on these four sequences.