Mesozoic Rift Basins of the U.S. Central Atlantic Offshore: Comparisons with Onshore Basins, Analysis, and Potential Petroleum Prospectivity

摘要

Limited exploratory drilling based on relatively sparse seismic data has occurred since at least 1890 in onshore Late Triassic-Early Jurassic rift basins of the eastern United States (U.S.). Although rich source rocks and thermally generated hydrocarbons have been documented, commercial petroleum accumulations have not been found. Consequently, in 2012 the U.S. Geological Survey (USGS) assessed these basins as having potentially modest volumes of primarily continuous (unconventional) resources. Using these findings and interpretations, what then is the prospectivity of similar age undrilled rift basins in the offshore of the U.S. Central Atlantic? Are there any indications of differences between the offshore and onshore basins in the apparent mode of formation, structural style, amount of inversion, etc., documented, or suggested by seismic data in these undrilled offshore basins? What do we know, and what can we speculate regarding petroleum system elements and processes in these unexplored basins? Seismic data interpretation suggests most offshore rift basins are generally similar to the Late Triassic-Early Jurassic rift basins onshore. The amount of eroded synrift strata predicted by geohistory modeling in the seismically defined Norfolk basin, offshore Virginia, is similar to that of onshore basins. However, seismic data interpretation also shows differences among some of the offshore basins; e.g., a rift system northwest of the Yarmouth arch in the northern Georges Bank basin, offshore New England, appears to have less synrift section eroded than most basins in the U.S. Central Atlantic and contains inversion features that appear seismically similar to productive structures found offshore Indonesia.