Abstract: New Discoveries and Hydrocarbon Potential of the Northwestern Region and the Red Sea Coastal Plains, Kingdom of Saudi Arabia

Sami M. Aoudeh

The recent discoveries of Paleozoic high-gravity hydrocarbons in the Central Province of Saudi Arabia inaugurated the launch of effective and successful exploratory programs in the frontier Northwestern Region and the coastal plains of the Red Sea.

In the Northwestern Region, all Paleozoic reservoirs are clastic. Their age varies from Devonian to Pre-Cambrian. The regional source rock, consisting of a thick sequence of dark colored shales is the Silurian Qusaiba Member of the Qalibah Formation. A basal highly organic-rich black "Hot Shale" unit is the prolific source correlated to all Paleozoic hydrocarbons discovered in Arabia. Devonian, Silurian, Ordovician, and Pre-Cambrian shales provide adequate seals.

Unlike the Northwestern Region, exploration efforts along the coastal plains of the Red Sea are concentrated within the Tertiary Miocene. Productive middle and lower Miocene reservoirs are both carbonates and clastics, with the middle and upper Miocene evaporites providing the regional seals. Both middle and lower Miocene marine shales are believed capable of generating both gas and oil in the deeper offshore basins. However, the best near-shore source identified to date comprises shallower inter-evaporitic shales with excellent generating capacity.

Structural traps in both areas are characteristically highly complex. In the Northwestern region the structures are mostly broad, large and fault-related. Growth of these structures occurred in many pulses ranging from the Late Paleozoic Hercynian to the Triassic and Cretaceous. In the Red Sea coastal plains the traps are much smaller rift-type tilted fault blocks.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994