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Sarkar, Sudipta, 2008

Shallow surface thermogenic hydrocarbon migration over western Prudhoe Bay Region, Alaska

Bibliographic Reference

Sarkar, Sudipta, 2008, Shallow surface thermogenic hydrocarbon migration over western Prudhoe Bay Region, Alaska: University of Alaska Fairbanks, M.S. thesis, xii, 157 p., illust., maps.

Abstract

Hydrocarbons leak from petroleum reservoirs to the surface. In continuous permafrost regions such as the Alaska North Slope, surface migration of thermogenic hydrocarbons may be hindered by the presence of ground ice. However, suitable permeable migration pathways in the permafrost can exist. Unfrozen sediments at the bottom of the lakes, or open faults can facilitate thermogenic hydrocarbon migration. I studied the nature and distribution of gaseous alkanes (C1 to C6) and helium in the shallow permafrost cores (2 m depth); depth profiles of alkanes (C1 to C7) in the two wells (1,500 m deep); and stable isotopes of CH4 trapped in lake gas bubbles, to trace the presence of thermogenic hydrocarbons and their migration pathways. Geostatistical analysis of the alkane and helium distributions shows that most anomalies occur along northwest - southeast-oriented lineaments, roughly corresponding to the trend of the Eileen fault mapped at 2,675 m depth, high fault density zones of the Kuparuk Formation, and northwest - southeast-trending Sagavanirktok faults mapped at 457 m depth. The anomalies above the Eileen fault can be explained by a fluid-flow model in a dilational jog along a wrench fault. This model agrees with the movements along the Eileen fault...

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