ABSTRACT

The Baltimore Canyon Trough is part of the offshore Atlantic Coast Continental Shelf and is filled with clastic sediments (sand-shales) ranging from Jurassic to Pleistocene in age. This constitutes an environment very propitious to the existence of stratigraphic or sedimentation traps formed by deformation, differential compaction, and igneous intrusions, including possible faulting and reefing. For the purpose of this evaluation, a knowledge of the nature of the entrapment geometry or mechanism is not needed because the interpretation procedure used is based on reliable and existing magnetic maps of the total earth magnetic field as it responds quantitatively to the hydrocarbons in place. The technique for this evaluation is based on magnetoelectric interpretation, i.e., on the evaluation of the vertical flux density of electrotelluric currents generated by the oil and gas in place by virtue of their electrochemical reactions with the catalytic clayey particles of the reservoir and country rocks.

There are a number of magnetoelectric interpretation methods ranging from the rapid visual .scanning procedure, through the spot-check circle integration, the polygon integration, and the computerized grid integration with downward projection to any desired depth and volumetric evaluation of the hydrocarbons in place. In this study, only the visual scanning and the spot-check circle integration methods were used.

Altogether, 55 promising areas were outlined and their approximate locations are shown with respect to the East Coast. Their combined discoverable hydrocarbon reserves are 117.1 Tcf of natural gas and 13.9 billion bbl of oil in place (1 Tcf of gas is equivalent to the thermal energy required to raise to boiling point the water from Lake Erie). One hundred seventeen Tcf of gas is almost 50 percent of the known gas reserves of the USA. Of the 13.9 billion bbl of oil, not all of it is recoverable, perhaps 25 percent, or 3.5 billion bbl of crude oil.

GEOLOGIC SETTING

On the basis of a reinterpretation of seismic velocity, gravity, and magnetic data from the Atlantic Outer Continental Shelf (AOCS) off the northeastern United States, geologists of the U. S. Geological Survey (1) have concluded that "the thickness of sedimentary deposits in the Baltimore Canyon Trough is as much as 36,000 ft (12 km) of post-Triassic sediments. Beneath these deposits, the basin may contain additional Triassic and pre-Triassic sedimentary rocks of undetermined thickness."

Structural and stratigraphic environments favorable for petroleum generation and accumulation exist within the Baltimore Canyon sediments. Well data from nearby onshore wells indicate that there are Cretaceous and Jurassic sedimentary wedge-outs in the updip direction along the coastal plains that could form stratigraphic traps. Deep-seated igneous intrustions exist in the trough that could have caused structural highs in the overlying sediments. A deep-seated basement ridge along the outer edge of the basin also could have resulted in the formation of structural highs in the overlying sedimentary section because of differential compaction and continued movement of the basement rocks.

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