GEOCHEMICAL ANALYSIS OF CRUDE OILS IN COOK INLET BASIN, ALASKA

Oil samples from 11 wells were taken from the G-Oil and Hemlock oil sands in the McArthur River Field in SW Alaska. Samples were also taken from 2 producing wells at the West McArthur River Field, and from the 2 producing wells at the Redoubt Field. These oil samples were analyzed and compared to one another and to published geochemical analyses already done on McArthur River Field and on other oil fields in Cook Inlet. The goals of this research are to determine the depositional environment of the source rock, correlation of the oil to the source rock, thermal maturity of the oil, and the reservoir continuity/compartmentalization of the oils. The oils were analyzed by Chromatography/Mass Spectroscopy and Gas-Chromatography, and various calculations were performed on the histograms obtained. The calculated vitrinite reflectance for the 15 oil sample shows a decreasing thermal maturity trend from a mature source rock in the northeast to a less mature source rock in the southwest. Reservoir continuity and compartmentalization of the oils are quite complicated. All of the oils show very similar chemical compositions. One of two scenarios could exist. The first scenario is that all of the oils are in connection with each other, which is highly improbable because of the long distances between the oil wells. The other scenario is that none of the oils are in communication and they are just from the same source rock. There could be some combination of the two scenarios.