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

• Main Author: Sarkar, Sudipta
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: Hydrocarbons; Petroleum; Prudhoe Bay; Fairbanks; Alaska North Slope; Ice; north slope; permafrost; Alaska
• Online Access: http://hdl.handle.net/11122/12841

Thesis (M.S.) University of Alaska Fairbanks, 2008 "Hydrocarbons leak from petroleum reservoirs to the surface. In continuous permafrost regions like 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 (1500 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 2675 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"--Leaf iii Bureau of Land Management 1. Introduction -- 1.1. Problem definition -- 1.2. Hypothesis -- 1.3. Objectives -- 2. Background -- 2.1. Geological background -- 2.1.1. Stratigraphy -- 2.2. Petroleum reservoirs -- 2.2.1. Kuparuk petroleum reservoir -- 2.2.2. Prudhoe Bay reservoir --2.2.3. West Sak reservoir -- 2.2.4. Petroleum filling history and hydrocarbon migration -- 2.3. Permafrost geology -- 2.4. Gas hydrates -- 2.5. Concept of hydrocarbon generation and migration -- 2.6. Helium in soil gas -- 2.7. Soil interference -- 3. Data -- 3.1. Soil hydrocarbon gas data -- 3.1.1. Sampling -- 3.1.2. Sample analysis -- 3.2. Lake gas data -- 3.2.1. Sampling -- 3.2.2. Sample analysis -- 3.3. Geochemical data from ...