Hydrocarbon Potential of the Baltimore Canyon Trough
ADINOLFI, FRED, Minerals Management Service, Herndon, VA
The Baltimore Canyon Trough, which is in the Mid-Atlantic Outer Continental Shelf (OCS) planning area, has a thick sediment accumulation and a large number of structural and stratigraphic traps. It is underlain by a seaward-thickening wedge of postrift sediments separated by an unconformity from older, more areally restricted rift sediments of Triassic and Early Jurassic age. Uplift and erosion landward of a hinge zone and regional subsidence seaward resulted in formation of the Baltimore Canyon Trough, an elongated northeast-trending depression filled with over 15,000 m of sediments.
Rift sediments are believed to consist of shallow-water carbonates, evaporites, arkosic red beds, and lacustrine shales, all of which are locally intruded by volcanic dikes and sills. These sediments occupy half-grabens landward and seaward of the hinge zone. Seaward, they also form basinward-dipping, wedgelike sequences. Postrift sediments have been penetrated by 32 wildcats and two deep stratigraphic tests drilled between 1978 and 1984. The sediments are shale, siltstone, sandstone, and carbonates. The carbonates predominate deep in the basin (lower Middle Jurassic) and in the seaward part of the shelf as shallow-water platform limestones. Along the seaward edge of the trough, the thick platforms are rimmed by a shelf-edge reef complex which developed until Berriasian (earliest Cret ceous) time, after which it was buried by a prograding clastic wedge which spilled onto the continental slope and rise in the form of turbidites, contourites, and hemipelagic drapes.
The top of the hydrocarbon evolution window is generally within the lower Cretaceous at a depth of about 3000 to 4000 m below sea level. Humic-prone (type III kerogens) Upper Jurassic strata are thermally mature for gas generation. Five wildcats drilled on one prospect tested gas from Jurassic reservoirs. One well also tested oil from an Albian sandstone at a depth of 2500 m below sea level.
Approximately 500 million bbl of oil and 20 tcf of gas (conditional mean undiscovered conventionally recoverable resources) were estimated to be present in the Mid-Atlantic OCS, according to a 1987 Minerals Management Service study. The Mid-Atlantic Baltimore Canyon Trough is a frontier exploration area with many prospects remaining to be drilled.
AAPG Search and Discovery Article #91006 © 1991 GCAGS and GC-SEPM Meeting, Houston, Texas, October 16-18, 1991 (2009)