C A N A D A Alaska Point Barrow Barrow Arch Prudhoe Bay
National Petroleum Reserve of Alaska
110 Ma Point Barrow 97 Ma
Brooks Range Foothills
Coastline
0 0
km mi Study area 100 100
96.01 Ma (impact) Avak structure Vapor Liquid
> Including impact in petroleum system modeling. Simulation of hydrocarbon maturation, migration and accumulation through time in the Barrow Peninsula shows a large accumulation at 97 Ma. At about 96 Ma, the Avak meteorite impact occurred, producing a circular, crater-like damage area (gray), effectively increasing the permeability and temperature. After the impact, the large oil accumulation disappeared. At present day, petroleum system modeling shows several gas accumulations near the impact structure. Modeled hydrocarbon phases are shown in green for liquid and red for vapor. Black dots indicate wells, and red arrows indicate the direction of plunge of the Barrow Arch.
Compared with the nonimpact model, the
postimpact petroleum system model gave a vastly different outcome. The sudden change in rock properties resulted in the release of trapped hydrocarbons. In addition, the drop in overpres- sure caused by excavation and postimpact uplift triggered a hydrocarbon phase transition from liquid to vapor. After impact, newly generated liquid hydrocarbons migrated into traps in the outer ring of the impact structure. With Tertiary uplift and erosion, these accumulations were transformed into vapor phases. The simulated present-day accumulations on the west, south and east sides of the Avak structure match the known gas accumulations in the area.
Embracing Impact Asteroid impact causes significant changes in surface morphology and subsurface rock proper- ties that should be considered when exploring for and producing hydrocarbons. These changes may be highly localized or regionally extensive; they may contribute to the formation of reservoirs or destroy them. Advances in remote sensing are making it
easier to find craters on the Earth’s surface that may be hidden by vegetation or other obstacles. For example, images from satellites can help identify impact-related features that are not rec- ognizable from the surface. Airborne light detec- tion and ranging (LiDAR) has been successful in locating an impact crater that was undetectable using visible imagery.48
Oilfield Review Autumn 09 Impact Fig. 20
ORAUT09-Impact Fig. 20 Winter 2009/2010 Though some craters are visible on the
surface, many are obscured by sediments. Traditional methods for detecting buried impact structures rely on surface geophysics—gravity, seismic and electromagnetic surveys.49
The strat-
egy is to identify anomalies consistent with an impact origin and then confirm them—or not—by examination of the rocks for traces of shock metamorphism. Until now, this has been the realm of plane- tary-science experts. In the future, as exploration teams learn to recognize impact structures, they will be able to model and exploit the effects of asteroid impact.
—LS
Present day
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