The Amin sandstone is a primary reservoir target of the Haima Supergroup (Vendian -Cambrian) for a Tight Gas Play for the Non-Associated Gas exploration in the Fahud Salt Basin, onshore Oman. Recent development in Tight Gas exploration in Oman have focused on possible fractured reservoirs of the Haima Supergroup. However, uncertainty remains in mapping and modeling of deformation styles of the various Haima lithologies, under the influence of regional and localised tectonic evolution. Quantification of the late structural evolution of the Oman Mountain orogeny in the Late Cretaceous were taken into consideration, which may introduce fracturing or possibly reactivates earlier structures of these Vedinian-Cambrian rocks.
Multi-disciplinary fieldwork was carried out, with the following overall aims: (1) to understand the effect of mechanical rock properties on deformation styles of the Amin Fm. (Haima Supergroup) and the Buah Fm. (Huqf Supergroup) and (2) to develop understanding of potential fractured plays in the Fahud Salt Basin area. Due to limitation of number of available days for fieldwork, surface LIDAR acquisition was utilised to expedite fracture measurements on selected outcrops. We focused upon the Haushi-Huqf Uplift 300km south of Muscat due to presence of good quality outcrops of Amin and Buah formations. LIDAR acquisition was carried out over three major localities: a) Locality 1: Wadi Sumayinah, b) Locality 2: 5km SE of Wadi Sumaynah and c) Locality 3: the Buah Anticline.
In parallel to surface geology studies, a much wider regional geophysical interpretation was carried out to investigate possible correlation of structural styles seen at the outcrops to our area of interest which lies approximately 200km northwest of the Huashi-Huqf Uplift. For this regional evaluation we have utilised gravity data and satellite imagery, proprietary regional 2D seismic and 3D seismic to improve our interpretation of major structural lineaments in the subsurface and possible correlation to measured surface geology.
Several relevant, nearby published discoveries were used as analogues of fractured reservoirs in the subsurface as calibration of our observations and interpretations.
We observed over a wide area of ~ 200-300km radius, that the main structural orientations seen in outcrop can be correlated to the area of exploration interests. Similar fracture orientations can be observed and compared to the analogue discoveries of the fractured Aptian limestone; these observations further support the likelihood of reactivation of older reservoir structions in response to later tectonic events.
From this exercise we found many possibilities to improve surface geological data in supporting subsurface E&P activities. Although we acknowledge that issues of scale still remain, the effort to find better methods to integrate and exploit the value of surface geological analogues as an effective hydrocarbon prospecting tool should be fully harnessed.