Resource Evaluation Program
Geological and Geophysical Data Acquisition and Analysis
Geological Surveys
Geological surveying on the Outer Continental Shelf consists of bottom sampling, shallow coring, and deep stratigraphic tests. These data are useful in determining the general geology of an area and whether the right types of rocks exist for petroleum formation and accumulation.
Bottom samples are obtained by dropping a weighted tube to the ocean floor and recovering it with an attached wire line. Depending upon the nature of the ocean floor, penetration is normally limited to a few tens of feet. Bottom samples can also be obtained from dredging.
Shallow coring is performed by conventional rotary drilling equipment to obtain a near-surface sample of the rocks of the seabed. Choice of location is carefully controlled to avoid any shallow (geological and manmade) hazards, for example, faults or environmentally sensitive areas. Penetration is limited to 50 feet of consolidated rock.
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In any planning area, deep stratigraphic test wells, commonly known as Continental Offshore Stratigraphic Test (COST) wells, can be drilled to determine the geological character of rock strata. The location of such wells is carefully controlled under a permit issued by BOEM. COST wells, which may be more than 20,000 feet deep, provide information that can be used by the Government and industry to evaluate tracts to be offered in a lease sale. Typically a consortium of interested companies is created so that drilling costs can be shared. All COST wells are drilled in accordance with BOEM and BSEE regulations.
As per BOEM regulations, all COST wells must be completed within 60 days before the anticipated lease sale date and the information must be released to the public 10 years after completion of the well (or 60 calendar days after the issuance of the first oil and gas lease within 50 miles (80.6 km) of the well site). The last COST well was drilled in 1989 in the Central Gulf of Mexico.
Resources and Publications
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