Identifier

etd-11122007-025400

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

Previous studies of the areal variations in heat flow and spatial variations in formation water salinity and hydraulic head are consistent with the existence of a currently active, topographically-driven regional fluid flow regime in the National Petroleum Reserve Alaska (NPRA) portion of the western North Slope foreland basin. This conclusion is also supported by the results of numerical modeling of fluid flow and heat transport in the area. This work has now been extended to the east. The results of this study demonstrate that the Permian though Cenozoic age sediments of the central North Slope foreland basin have been significantly flushed by low salinity waters. Although isotopic analyses of these waters are not available, it is likely that they have a major meteoric component, as is the case in the NPRA immediately to the west. There may have been several periods of time in which meteoric waters were introduced into the section, including the Triassic, during the development of the Lower Cretaceous Unconformity (LCU), and following the uplift of the Brooks Range in the Upper Cretaceous. Diagenesis associated with fluid flow during the LCU may have provided pathways for later hydrocarbon migration. The introduction of meteoric water has the potential for lowering the API gravity of crude oil through water washing and/or biodegradation. However, there is no clear relation in the North Slope between salinity and API gravity. It is possible that the Prudhoe Bay oils, which are light, were emplaced following invasion of fresh waters and the overlying Kuparuk oils, which are heavier, have been significantly impacted by fresh waters following hydrocarbon migration and entrapment. By analogy in geologic setting to the NPRA, a topographically-driven fluid flow regime probably exists today in the central North Slope, but additional pressure, head, and temperature data are needed to further verify this hypothesis. There is no clear relation between depth to the base of permafrost in the study area and elevated temperatures at depths of 2-3 km which may reflect fluid upwelling.

Date

2007

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Jeffrey A. Nunn

DOI

10.31390/gradschool_theses.4108

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