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GEOREF RECORD

Evaluation of hydrocarbon broaching after subsurface containment failure, Gulf of Mexico

Thomas W. Bjerstedt, William W. Shedd, Michael G. Natter, Pierre B. Abadie, George J. Moridis and Matthew T. Reagan
Evaluation of hydrocarbon broaching after subsurface containment failure, Gulf of Mexico
AAPG Bulletin (April 2020) 104 (4): 845-862

Abstract

Broaching refers to the release of hydrocarbons at the seafloor after a loss of subsurface well containment. An underground blowout may allow migration of fluids upward through adjacent formations or the annulus to the seafloor. After the BP 001 Macondo well was capped, an oil slick was observed near the well. Available data were interpreted to determine if the slick was reservoir fluid broaching the seafloor or if it was a natural seep in the Gulf of Mexico. The experience revealed that no basis existed for estimating subsurface broach rates or how a potential to broach should be considered during well permitting decisions. Lawrence Berkeley National Laboratory (LBNL) modeled two broaching failure scenarios selected by the Bureau of Ocean Energy Management (BOEM) and representative of Gulf geosystems. Geoscientists from BOEM provided reservoir parameters and interpreted geologic surfaces from depth-migrated three-dimensional seismic volumes. The LBNL adapted existing supercomputing capabilities to model the traveltime for formation fluids to reach the seafloor after subsurface containment failure. The most sensitive parameters affecting traveltime are the mixture of formation fluids and the permeability of the geologic media through which it passes. Assuming nondepletion of reservoir pressure, gas-prone multiphase fluids may broach within a matter of decades. Wet oil and oil-prone multiphase fluids are slower by one to three orders of magnitude. The likelihood for the modeled systems to broach was mainly dependent on casing failure depth. The BOEM concluded that casing failures greater than 7500 ft (>2280 m) below mudline (seafloor) will not broach within a 6-month time frame of regulatory concern.


ISSN: 0149-1423
EISSN: 1558-9153
Coden: AABUD2
Serial Title: AAPG Bulletin
Serial Volume: 104
Serial Issue: 4
Title: Evaluation of hydrocarbon broaching after subsurface containment failure, Gulf of Mexico
Affiliation: U. S. Department of the Interior, U. S. Bureau of Ocean Energy Management, New Orleans, LA, United States
Pages: 845-862
Published: 20200415
Text Language: English
Publisher: American Association of Petroleum Geologists, Tulsa, OK, United States
References: 29
Accession Number: 2020-039431
Categories: Economic geology, geology of energy sourcesEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 4 tables, sketch maps
N28°37'60" - N28°46'60", W88°23'30" - W88°22'00"
Secondary Affiliation: Lawrence Berkeley National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by American Association of Petroleum Geologists, Tulsa, OK, United States
Update Code: 2020
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