The Endicott Oil Pool is defined as the accumulation of hydrocarbons common to and correlating with the interval between 11,496’ and 12,812’ measured depths in the Sag Delta No. 4 well.3
This accumulation occurs in Mississippian-aged, fluvial sediments assigned to the Kekiktuk Formation (Kekiktuk). The pool is trapped by a combination of structural and stratigraphic elements within a large, northwest- trending fault block that dips toward the northeast. Normal faults border the accumulation to the north and southwest. Structural dip limits the field to the southeast.4
Upper confinement for the accumulation is provided by the Kayak Shale-Itkilyariak Formation and, in the northeastern portion of the pool, by the Lower Cretaceous Unconformity.5
The pool is broken by several minor faults that are subparallel to the major bounding faults. One of these faults, termed the Mid-Field Fault, is sealing,6
and it divides the reservoir into two parts: a northern field area developed mainly from the Main Production Island (“MPI”), and a southern area, which is produced mostly from the Satellite Development Island (“SDI”).
Three lithostratigraphic units are defined within the Kekiktuk. They are, in ascending order, Zone 1, Zone 2 and Zone 3, and they have an aggregate thickness of up to 1,200’. Zone 1 consists mainly of the shale, coal and siltstone deposited in floodplain, swamp and lacustrine environments. Associated sand bodies have very limited continuity. Zone 2 contains very porous and permeable, laterally continuous, medium-grained reservoir sandstone primarily deposited in low-sinuosity, coalescing braided channels that extend across the entire reservoir. Associated, locally continuous shales within Zone 2 were deposited in lacustrine environments. Zone 3 consists of fine-to medium-grained sandstone occurring in stacked point-bar channels deposited in a high-sinuosity, fluvial environment. These stacked channel sands are lenticular, and are interspersed with equal amounts of shale, siltstone and coal, which accumulated in between the fluvial channels.7
A gas-oil contact occurs at about 9,855’ true vertical depth subsea (“TVDSS”), and an oil-water contact occurs at approximately 10,190’ TVDSS.8
The areal extent of the hydrocarbon accumulation is about 8,600 acres.9