IMPACT CRATERS:IMPLICATIONS FOR BASEMENT HYDROCARBON PRODUCTION

The impact cratering process results in unique structures and extensive fracturing and brecciation of the target rock which can be conducive to hydrocarbon accumulations. Examination of Viewfield and Red Wing Creek oil pools in North America reveals that they may have been formed by meteoritic impact in Paleozoic sediments. Additional hydrocarbon traps have most likely been produced by impact but have not been recognized as such because geologists are generally not familiar with crater structures and shock‐metamorphic effects in rocks. It is proposed that petroliferous basement impact craters also exist and that despite arguments to the contrary, at least one may have already been found. Further discoveries are severely limited because of conservative exploration procedures, which characteristically avoid penetrating crystalline basement. Core analysis from several large impact sites developed in crystalline rocks reveals that while permeability factors are marginal, the reservoir potential of these craters exceeds those of many of the largest known hydrocarbon accumulations. Preservation age studies of craters in conjunction with size frequency distribution curves implies that many will have been buried before erosional eradication. As with normally‐fractured and brecciated basement areas, some will have accumulated hydrocarbons. In addition to classical source rocks flanking or overlying these potential reservoirs, recycled kerogen and the possibility of inorganic sources are also considered. A basement impact crater may afford a unique way of testing the inorganic hydrocarbon proposals.