Royale’s Abdel-Rahman sees different path

In the course of interviews with Royale Energy officials, Mohamed Abdel-Rahman, Royale’s vice president for exploration and production, provided Petroleum News with a description of how oil is generated in source rock, as well as more information about his unconventional view on the charging of the big North Slope reservoirs. Following are direct quotes from him:

“Oil is generated by kerogen, a mixture of organic chemical compounds that make up a portion of the organic matter in sedimentary rock. When subjected to heat by burial — the deeper rock is buried the hotter it is — that’s the oven, or the kitchen. As it cooks kerogen is changed into oil. As more oil is generated, the volume increases, so it builds up pressure and tries to escape the source rock.

“The oil trying to escape needs something called a ‘carrier bed’ to get out of the rock, to migrate into a trap. A carrier bed is a porous and permeable rock near the source rock through which petroleum flows from source to the trap, or reservoir, where it will reside until it is discovered.

“The physical characteristics of carrier-bed rocks are the same as reservoir rocks, that is, sandstones, limestones, or fractured rocks of all types.

“If there is no carrier bed adjacent to the source rock oil will stay where it was generated until it is exploited, using horizontal wells and hydraulic fracturing.

“The kitchen is down-dip and oil migrates out of the kitchen up-dip. All the fields along the Barrow Arch are up-dip; to the south you have the kitchen, which is deeper than the arch. Typically geologists talk about oil finding its way from source rock to go up-dip. What we differ on is where that carrier bed is; sometimes it is the down-dip equivalent of the reservoir. In the North Slope, the reservoir quality of the Ivishak, the main reservoir of the Prudhoe Bay field, deteriorates very rapidly as you go towards the kitchen. Therefore, it does not qualify as a carrier bed in my view since it lacks sufficient permeability.

“Another complicating factor to a simple charge story is the fact that the Shublik is younger than the Ivishak and its down-dip equivalent strata (i.e., it sits above it stratigraphically). This would mean that Shublik-generated oil will have to migrate downwards (typically oil migrates upwards because of its buoyancy) into strata that are not good carrier beds.”

So how did oil make it from the source rock to the Ivishak? It had to find a different route, Abdel- Rahman said.

At the State of Alaska’s Dec. 7 North Slope lease sale, Royale used Abdel-Rahman’s model to select acreage along the heart of the oil window, choosing leases for their thermal maturity for oil.

—Kay Cashman