CRAIG, JAMES D., KIRK W. SHERWOOD, and SARAH B. HURLBERT, Minerals Management Service, Anchorage, AK

ABSTRACT: Log Evaluation of a Hydrocarbon Reservoir in the Burger Well, Chukchi Sea

Recently released data from the SWEPI OCS-Y-1413 #1 well offshore northwestern Alaska includes information on gas and high-gravity oil shows in a sandstone/shale sequence equivalent to the Kuparuk Formation of the North Slope. A prospective reservoir was encountered between 5560-5665 ft (log depth) composed of medium-to very fine-grained, well-sorted, quartz sandstone. Porosities of 27-29.5% and permeabilities of 222-447 md are reported for the upper part of the sandstone, with porosities of 22-26% and permeabilities of 11-139 md in its lower part.

A neutron-density log crossover at 5620 ft indicates that the upper 60 ft of this reservoir contains nonassociated gas at the well location. In this upper, high permeability interval calculated hydrocarbon saturation averages 80% with moveable hydrocarbon saturations over 60%. In the underlying low permeability interval, moveable hydrocarbon saturations decrease downhole from a maximum of 60% to zero at the base of the sandstone.

Below the gas cap, a gradual decrease in deep resistivity indicates progressively increasing water saturation. However, a coincident decrease in permeability and increasing shale volume suggest that these effects could be related to lithology and may not represent an oil-water transition zone. Shaly sand evaluation models, sidewall core data, and pressure profiling provide evidence that the hydrostatic oil-water interface probably lies deeper than the base of this reservoir.

A deeper hydrostatic oil-water interface provides the potential for a significant liquid hydrocarbon accumulation in the immense Burger structure if similar productive reservoirs are present.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.