Abstract

Exploration activity to date on the U.S. Atlantic Continental Shelf includes 3 oil and gas lease sales and the drilling of 5 deep stratigraphic test wells and 26 wildcat wells. Wildcat drilling in the Baltimore Canyon trough has been concentrated in the vicinity of the Great Stone dome and along the shelf edge. The Great Stone dome, a large domal structure inferred to be associated with an Early Cretaceous mafic intrusion, appeared to be one of the largest and most promising single structures on the shelf on the basis of the interpretation of seismic data. Six wells have been drilled on the structure, but no shows of oil or gas have been reported.

Results of wildcat drilling along the outer edge of the Continental Shelf have been more encouraging. Significant shows of natural gas have been reported from 3 out of 14 completed wildcat wells. The combined initial flow rates were about 2 million m3 per day (68.5 million ft3 per day) from Upper Jurassic sandstone beds at per day) from Upper Jurassic sandstone beds at depths of about 4,000 m. An additional test, at one of these wells, flowed 48.4 deg. gravity oil at the rate of 100 m3 per day (630 barrels per day) from a thin bed of Lower Cretaceous sandstone. A commercial size field, however, has not been established.

In the Baltimore Canyon trough, analysis indicates that shelf sediments have a relatively low potential for the generation of liquid hydrocarbons, but indications are favorable that natural gas could have been generated below a depth of 3,000 m. However, sandstone porosities deteriorate below 3,000 m, and at these depths, the Jurassic sandstone beds may lack lateral continuity.

Tracts to be leased in upcoming sales will extend out to water depths of 2,500 m. In the deep-water area beneath the Continental Slope, the interpretation of seismic data suggests that the shelf prograded seaward during Jurassic time. Consequently, Jurassic shelf facies containing potential reservoir rock may interfinger with potential reservoir rock may interfinger with slope facies that could contain source rock capable of having generated liquid petroleum. In spite of the huge investments of money that will be required for deep-water exploration, the possible presence, under the slope, of complex extensional-fault presence, under the slope, of complex extensional-fault patterns, reef complexes, and salt diapirs will probably patterns, reef complexes, and salt diapirs will probably encourage interest in upcoming sales.

Introduction

The northern U.S. Atlantic Continental Shelf contains two sedimentary basins: the Georges Bank Basin off New England and the Baltimore Canyon trough off of the Middle Atlantic States (Fig. 1). The purpose of this paper is to discuss the stratigraphy, basin configuration, and petroleum geology of the Baltimore Canyon trough.

Much of the geologic information and many of the inferences contained in this report have been derived from multichannel common depth point (CDP) seismic reflection data. Cross-shelf profiles spaced 40 km apart (Fig. 1), were recorded and processed mainly by industry under contract to the processed mainly by industry under contract to the U.S. Geological Survey (USGS); several lines were processed by USGS personnel on the Phoenix I system processed by USGS personnel on the Phoenix I system in Denver. A 185,000 km aeromagnetic survey (Klitgord and Behrendt 1979) which had a flight-line spacing of 3–5 km on the Shelf and Slope was flown by LKB Resources under contract with the USGS. In addition, the USGS and the Woods Hole Oceanographic Institution cooperatively measured the gravity field on a 10 mgal contour interval using a grid spacing of 20 km (Grow et al., 1979). Geological information has been derived from the COST No. B-2 well (Scholle 1977) and the COST No. B-3 well (Amato and Simonis 1979). These wells (Fig. 1) provide the only publicly available data on provide the only publicly available data on stratigraphy, lithology, and reservoir-source rock characteristics for rocks deeper than 300 m. Two other COST wells, G-1 and G-2, have been drilled in the Georges Bank Basin.

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