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Interactions Between Early and Late Diagenesis in Reservoir Formation, Lisburne Previous HitFieldNext Hit, Prudhoe Bay, Alaska

Jeremy Jameson

The Lisburne Previous HitfieldNext Hit is an Previous HitexampleNext Hit of a giant carbonate oil Previous HitfieldNext Hit where reservoir porosity formed due to several distinct, diagenetic events. The later stages of diagenesis occurred during relatively deep burial and often exploited preexisting pathways. Although burial diagenesis is generally perceived as being destructive to porosity and permeability, the Lisburne Previous HitfieldNext Hit is an Previous HitexampleNext Hit where late processes combine to enhance reservoir properties.

The earliest porosity formed during the Pennsylvanian as shallow-marine carbonates of the Wahoo formation, which were subaerially exposed at the close of some depositional cycles. Early porosities are moldic and minor intercrystalline, occurring at shoal and near shoal facies. The second stage of porosity development is intercrystalline, associated with Permian-Triassic burial and ferroan dolomitization at depths of 1,000-2,000 ft (800-1,600 m). Trace element gradients and isotopic Previous HitdataNext Hit indicate the overlying Kavik shales were a source of fluids. In general, ferroan dolomites formed by overgrowth on early (?Pennsylvanian) dolomite.

The youngest porosity is moldic and Cretaceous/Tertiary age. Burial fabrics such as stylolites and sutured grain contacts are often probably associated with burial expulsion of fluids from Cretaceous shales on the eastern side of the Previous HitfieldNext Hit.

Although each stage of porosity is volumetrically significant, the reservoir quality of the Lisburne Previous HitfieldTop is best in areas affected by all three stages of diagenesis. The second and third stages of porosity development are particularly important to reservoir quality.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.