This report was prepared to provide a concise description of offshore operations related to exploration for petroleum (oil and natural gas} from the initial geologic and geophysical investigations to production. Petroleum deposits differ in their physical and chemical properties and are associated in the rocks with saline water. The origin of petroleum and its migration through rocks are not well understood. Commercial accumulations are found in certain suitable rocks or geologic structures - stratigraphic and structural traps, respectively.
The Delaware Geological Survey's Outer Continental Shelf (OCS) Core and Sample Repository is a large collection of cores and samples from oil and gas wells drilled offshore the Atlantic Coast of the U.S. during the 1970s and 1980s. This collection was assembled from the contributions of federal agencies, other state agencies, and private institutions that have recognized the value of having a centralized repository for this material.
A series of elongate rift basins of early Mesozoic age is exposed in eastern North America in a belt extending from Nova Scotia to South Carolina. The Upper Triassic-Lower Jurassic synrift rocks that fill the basins are called the Newark Supergroup comprising continental (fluvial and lacustrine) clastic sedimentary rocks (predominantly colored red) interbedded with basaltic volcanic rocks (Froelich and Olsen, 1985). Similar basins are buried beneath the sediments of the Atlantic Coastal Plain and continental shelf.
Three multichannel, common-depth-point (CDP), seismic reflection profiles were run off Delaware's coast for the Delaware Geological Survey. Their purposes were (1) to determine the depth to the unconformity (post-rift unconformity) at the base of the nearshore submerged Coastal Plain sedimentary rocks and (2) to relate onshore with offshore
The structure contour map of pre-Mesozoic basement
indicates the structural complexity of the landward margin of
the Baltimore Canyon trough, especially that shown by the
buried rift basins of probable early Mesozoic age. Information
on depth to basement is important in determining the economic
limit of drilling through overlying rocks in the search for oil
Lithologic logs from 268 vibracores taken from the Delaware Atlantic offshore were evaluated for sediment type and compatibility with historical beach sediment textures. A model of sand resource evaluation, known as "stack-unit mapping" (Kempton, 1981) was applied to all of the cores, and each core was labeled by its lithology in vertical sequence. The results are shown in detailed maps of the beach-quality sand resources offshore in state and federal waters.
The Delaware Academy of Science has been instrumental in informing Delaware citizens about science and utilization of local resources. Since 1970 the annual meeting of the Delaware Academy of Science has been used as a time for presentation of ongoing research in various areas of science in the Delaware region. The proceedings of these meetings have resulted in publication of transactions of the Delaware Academy of Science. The 1976 annual meeting focused on aspects of the geology of Delaware.
The Generalized Geologic Map of Delaware is a brief summary for general use indicating the major types and locations of rocks present throughout the State, and their interrelationships. The map is preliminary as it is a first step in a continuing program of detailed geologic mapping. It is based upon many existing sources of data; additional detail may be found in the references listed.
The nature and occurrence of subsurface resources, whether ground water, minerals, or petroleum, are controlled by the geologic history and framework of any particular area. Several years ago the staff of the Delaware Geological Survey began an informal assessment of the potential resources of southern Delaware and demonstrated the lack of basic data on the deep subsurface in this area. This assessment was later summarized by Benson (1976) with particular emphasis on the possibilities for petroleum occurrence.