NORTH SLOPE BASIN – WHAT CAN STATISTICS TELL US

The North Slope Basin spans the entire width of north Alaska, and covers an area of approximately 300,000 sq km. The basin's extreme environment and remoteness from the hydrocarbon markets combine to focus the oil industry's efforts on the search for giant oil and gas accumulations. Oil and gas exploration started in the beginning of the 20th century but the basin remains immature offshore and moderately mature onshore in terms of hydrocarbon exploration.

The North Slope Basin has proven extremely prospective for oil and gas. Despite the high costs associated with exploring in the Arctic, over 450 exploratory wells have been drilled to date. The recent discoveries, however, do not offset the oil production. Ultimate recoverable reserves are estimated at some 19,524 MMbl of liquids and over 38,616 Tcf of gas. Remaining recoverable reserves are estimated at 5,230 MMbl and 16,790 Bscfg.

The question is how much are there still to be discovered? One way of evaluating / calculating the remaining reserves is to use complex models including source rock richness and distribution, production index, reservoir distribution, etc.

The nature of the distribution of objects in nature has been investigated over many years, and both linear and curved plots have been proposed to describe the relationship between size and rank. With field size distribution and Yet-To-Find methods, using lognormal and parabolic distributions, we can attempt to provide an estimate and the distribution of remaining recoverable reserves for the North Slope Basin (excluding the Chukchi Sea area). In this study we considered a low and a high scenario, for both oil and gas. The high scenario assumes that another giant oil (respectively gas) field can be found.

The presented here Yet-to-Find analysis of the North Slope Basin indicates that several fields with reserves of 100 MMbo or more can still be discovered, with estimated total recoverable reserves of 2,600 to 7,500 MMbo. The gas analysis suggests that, taking in account only fields with reserves of 1.5 Tcfg or more, some 4,300 to 20,000 Bscfg can still be discovered.