Petroleum Geology of Kodiak Shelf, Alaska

Organic geochemical data show that Cenozoic rocks on Kodiak Island, in Albatross basin, and under the continental slope generally contain less than 0.5 wt. % organic carbon. Moreover, kerogen from all rocks analyzed is predominantly (60 to 100%) herbaceous; woody and coaly kerogens are present in secondary (20 to 40%) amounts. Most strata in shelf basins are thermally immature; however, Eocene and Oligocene strata, which probably floor the shelf basins, are mature on the basis of comparison with coeval strata onshore. Eocene and Oligocene rocks have poor reservoir properties; the best reservoirs are probably in upper Miocene or Pliocene and younger rocks. Potential traps for hydrocarbons include Tugidak uplift, parts of Albatross Bank, structures in the central-shelf uplift, and Portlock anticline. Overall, unless hydrocarbon source rock properties improve offshore, gas and gas condensate are the most likely hydrocarbons to have been generated.