New unconventional play concepts in the Middle East – The Silurian Qusaiba Member

Sometimes the best quality conventional source rock is not the most prospective unconventional resource. By understanding how hydrocarbons are expelled from organic-rich intervals, it is apparent that poorer quality source horizons are more likely to retain hydrocarbons in place. Rather than better quality source rocks which expel a large quantity of hydrocarbons, which then migrate to conventional traps. Therefore, by identifying stratigraphic horizons of varying source quality in the Silurian of the Middle East prospective horizons which have retained some charge can be identified. By understanding the plate scale structural architecture, areas where these source rocks subcrop low-angle unconformities covered by sealing facies can highlighted. The potential for sealing facies to occur above the unconformity, limits the expulsion and migration of hydrocarbons from the source rocks. This may be further enhanced by the inability of poorer quality source rocks to expel hydrocarbons. This shows that a number of Montney-esque play types within the Silurian of the Middle East may exist. Most notably where the Silurian Qusaiba Member subcrops the Unazyah Formation and where particular parts of the Silurian are in unconformable contact with sealing facies of the Unazyah.