Hydrocarbon Systems, Basin Analyses, and 2006 Field and Subsurface Data: Bristol Bay, Alaska Peninsula, Frontier Basin

Reifenstuhl, Rocky Robert¹, Paul L. Decker², Robert J. Gillis¹, Kenneth P. Helmold², Andrea Strauch¹ (1) Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK (2) Alaska Division of Oil & Gas, Anchorage, AK

Eight of 10 wells in the 2007 Alaska Peninsula Area Wide Lease Sale (3,500,000 acres onshore; 1,500,000 acres offshore) have oil or gas shows. Hydrocarbon-focused fieldwork in 2006 by the Alaska Divisions of Geological & Geophysical Surveys and Oil & Gas provides hydrocarbon system data and basin analyses. These include: organic geochemistry, hydrocarbon typing, total organic carbon, vitrinite reflectance, reservoir quality, sandstone petrography, mercury injection capillary pressure (MICP), rockeval, microfossils, coalbed gas adsorption, geologic mapping, and subsurface correlations. Carbon and deuterium isotopes from a dry, natural-gas seep in the Port Moller–Herendeen Bay area indicate a deep, thermally mature Mesozoic source. Hydrocarbon system plays include: Mesozoic (Middle Jurassic Kialagvik and Triassic Kamishak formations–thermogenic) and Tertiary (Cretaceous Chignik and Miocene Bear Lake formations–biogenic) sources. Miocene strata, an important reservoir-play model, are 3,700 feet thick and contain thin coal. Porosity and permeability ranges from 1 to 35% and 0.001 to 1,000 md. Thin coals occur in the underlying Cretaceous Chignik Formation, creating biogenic methane possibilities. Oligocene through Paleocene age organic-rich marine strata yield TOC to 8.9%, and 253 HI and 8 OI. The Kamishak Formation, a shallow-water limestone in Puale Bay, yields TOC to 2.4%, 598 HI, and 22 OI. Kialagvik Formation siliciclastic marine rocks yield up to 3.5% TOC, 680 HI, and 22 OI. These rocks are interpreted to underlie the northwestern part of Herendeen Bay and northwestward offshore. MICP analyses of five Early Cretaceous Staniukovich Formation outcrop siltstones yields seal capacity parameters: capillary pressure 1,266 PSI, gas height at 7.5% saturation = 1,266 feet, and oil height at 7.5% saturation = 732 feet. Publicly available seismic and field data suggest the presence of structural traps and regional unconformities that may act as traps or seals.