Assessment of unconvential (tight) gas resources in Upper Cook Inlet Basin, South-central Alaska

Data Series 69- AA
By: , and 
Compiled by: Christopher J. Schenk

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Abstract

A geologic model was developed for the assessment of potential Mesozoic tight-gas resources in the deep, central part of upper Cook Inlet Basin, south-central Alaska. The basic premise of the geologic model is that organic-bearing marine shales of the Middle Jurassic Tuxedni Group achieved adequate thermal maturity for oil and gas generation in the central part of the basin largely due to several kilometers of Paleogene and Neogene burial. In this model, hydrocarbons generated in Tuxedni source rocks resulted in overpressure, causing fracturing and local migration of oil and possibly gas into low-permeability sandstone and siltstone reservoirs in the Jurassic Tuxedni Group and Chinitna and Naknek Formations. Oil that was generated either remained in the source rock and subsequently was cracked to gas which then migrated into low-permeability reservoirs, or oil initially migrated into adjacent low-permeability reservoirs, where it subsequently cracked to gas as adequate thermal maturation was reached in the central part of the basin. Geologic uncertainty exists on the (1) presence of adequate marine source rocks, (2) degree and timing of thermal maturation, generation, and expulsion, (3) migration of hydrocarbons into low-permeability reservoirs, and (4) preservation of this petroleum system. Given these uncertainties and using known U.S. tight gas reservoirs as geologic and production analogs, a mean volume of 0.64 trillion cubic feet of gas was assessed in the basin-center tight-gas system that is postulated to exist in Mesozoic rocks of the upper Cook Inlet Basin. This assessment of Mesozoic basin-center tight gas does not include potential gas accumulations in Cenozoic low-permeability reservoirs.

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Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Assessment of unconvential (tight) gas resources in Upper Cook Inlet Basin, South-central Alaska
Series title Data Series
Series number 69
Chapter AA
DOI 10.3133/ds69AA
Year Published 2015
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Central Energy Resources Science Center
Description 3 Chapters: variously paged; Upper Cook Inlet Basin Database
Country United States
State Alaska
Other Geospatial Cook Inlet Basin
Online Only (Y/N) Y
Additional Online Files (Y/N) Y