Techniques for Exploring Remote Alaska Basins for Oil and Gas
Oil production in Alaska began along the southern margin with discovery in 1957 of the 500 MMBO Swanson River field in Cook Inlet. This discovery and the financial promise it held allowed Alaska to apply and receive statehood in 1959. Discoveries on the North Slope of Alaska, beginning in 1969 with the giant Prudhoe Bay field, filled the TransAlaska Pipeline with decades of subsequent oil production. Multi-billion barrel fields are still being discovered on the North Slope, although the pipeline is currently at about 25% capacity (500,000 B/D).
Alaska has several sedimentary basins in the remote Interior of the State which have potential to produce oil and gas for local use and possibly export. Nenana basin near Fairbanks is an instructive example of data and methods that serve to evaluate and explore the potential of an unknown basin. These often begin with geologic field work and regional potential field surveys (gravity, magnetics) and culminate with seismic and drilling, if warranted. New basin exploration is a risky and expensive business and managing risk is an important part of the work. Any creative and innovative approach that increases geologic understanding and lowers risk is welcome.
Nenana basin contains Tertiary fluvial, sedimentary rocks preserved over metamorphic basement. The basin is deep (>20,000’), warm (2.2°F/100’ gradient), and contains unusual hydrogen-rich coals which expel liquid oil when heated. Quartz-rich sands with good porosity occur in the deeper section. Surface lakebed sediments contain trace amounts of long chained hydrocarbons (microseeps). A late Miocene structural transition from an extensional half-graben geometry to a transpressional pull-apart basin created mid-basin uplifts and fault traps. 2D and 3D seismic returns good images which appeared to contain Direct Hydrocarbon Indicators (DHI’s). Nevertheless, four deep wells were unsuccessful in finding oil or gas despite abundant oil and gas shows.