Online Journal for E&P Geoscientists

Wilks, Bill ^*1; Johnson, Tim ¹; Salmi, Wafa ³; Busaidi, Talal ²; Mcilroy, James ³
(1) Exploration, New Opportunities, Petroleum Development Oman, Muscat, Oman. (2) Exploration, Quantitative Interpretation, PDO, Muscat, Oman. (3) Exploration, Oil South, PDO, Muscat, Oman.

The Ara stringers of the South Oman Salt Basin (SOSB) have long been a key exploration target for Petroleum Development Oman (PDO). Within the main body of the salt basin external tectonic forces have exerted a relatively subtle influence on early basin development, such that deep-rooted high relief traps are rare. Towards the west, however, all things change. The SOSB is bounded by an enigmatic zone named the ‘Western Deformation Front’ (WDF), which has itself been interpreted to extend into north Oman. Historic drilling results show that the WDF constitutes an extensive high, where much of the stratigraphy of the SOSB is missing due to erosion or non-deposition. The interpretation of this zone has historically been difficult due to the limited quality of the legacy 2D seismic database, which is partly linked to it’s apparent structural complexity.

Various models have been proposed to explain the evolution of the WDF, and it’s link to the history of the SOSB. These have included extension, transpression and compression, and have embraced both thick and thin-skinned mechanisms.

Despite disappointing drilling results along this trend to date, PDO still identifies play potential, especially amongst fractured carbonate reservoirs. This presentation highlights the results of multi-disciplinary geophysical studies which have sought to provide additional clarity on the evolution of this complex margin. These include recent 3D seismic surveys (high fold WAZ and conventional), gravity, magnetics and even the use of land based Magneto-Telluric surveying. The techniques have been used to reveal some of the details of the complex transition between the WDF and the SOSB proper. These include the definition of possible large scale overthrusts, the deformation style of the ‘bulldozed’ salt basin, and the possible interaction between the advancing thrust sheet and the depositional environments in the salt basin. Improved clarity in these areas provides better definition of the key plays and prospects, and will hopefully lead to renewed exploration drilling in this segment of the basin.

An evolutionary model is presented which represents the next step in our understanding of the South Oman Salt Basin.