--> ABSTRACT: Unique Horizontal-Well Designs Boost Primary and EOR Production, Prudhoe Bay Field, Alaska, by Robert S. Tye, Becky A. Watson, Patrick L. McGuire, and Mathew M. Maguire; #90906(2001)

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Robert S. Tye1, Becky A. Watson2, Patrick L. McGuire3, Mathew M. Maguire4

(1) Phillips Petroleum Co, Bartlesville, OK
(2) Petrotechnical Resources of Alaska, Anchorage
(3) bp Exploration Alaska, Anchorage
(4) Phillips Alaska, Inc, Anchorage

ABSTRACT: Unique Horizontal-Well Designs Boost Primary and EOR Production, Prudhoe Bay Field, Alaska

Using horizontal-wells, and an unprecedented enhanced-oil recovery (EOR) process, Phillips Alaska, Inc. is capitalizing on geologic and fluid-distribution complexities in the Triassic Ivishak Sandstone to recover untapped or bypassed reserves. Millions of barrels of reserves reside in a basal, 37-m thick succession of en echelon, offlapping deltaic wedges. Distributary-mouth bar and distributary-channel sandstones are targeted. Onlapping, retrogradational mudstones form laterally extensive flow barriers, impeding the gravity-drainage process.

Reservoirs are structurally isolated in fault blocks covering 100 acres or less. Reserves are sacrificed with conventional wells, due to small drainage areas. However, a horizontal well with a 90° bend, or fishhook shape, maximizes exposure to productive sandstones. First stable production was 3750 BOPD and 2600 GOR. Production was 11.2 MMBbls as of 4/97.

Horizontal wells in a Miscible Injectant Stimulation Treatment (MIST) program recover millions of barrels of EOR oil. In a lateral MIST project, a horizontal well is drilled from an existing well in a watered-out pattern. Maximum-sweep efficiency is achieved keeping the wellbore near the reservoir base as it arcs between an injector and outlying producers. Miscible injectant is introduced at the well tip, forming a gas bulb pushing oil to the producers. After adequate injection, the perforations are squeezed and the well is re-perforated nearer its heel. By sequentially injecting gas, squeezing perforations, and re-perforating in a more proximal position, post-waterflood oil is stripped from the reservoir. Incremental EOR from three horizontal wells exceeds 1.3 MMSTB. Simulations predict incremental EOR of greater than a million barrels per horizontal well.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado