Geologic characteristics in the vicinity of the Deepwater Horizon oil spill

Abstract

On April 20, 2010, the Deepwater Horizon offshore drilling rig experienced a catastrophic explosion and fire. At the time, it was drilling about 70km southeast of the mouth of the Mississippi River. A couple of days later it lay on the sea floor in more than 1500m of water. The drilling riser that extended from the sea floor to the water surface was destroyed and the blow-out preventer malfunctioned, causing a massive leak of crude oil and natural gas. Early attempts by British Petroleum (BP) and its drilling sub-contractors failed to cap the well. It continued to flow, at times intermittently, for more than 100 days. In total, it is estimated that at least five million barrels of oil were released into the Gulf of Mexico, undoubtedly the largest oil spill in U.S. history. Due to the proprietary nature of petroleum exploration and production, few details have been made public concerning the well from which the Deepwater Horizon spill originated. There is information about the geologic characteristics in the general vicinity of that well site, however. One source of information is the Gulf of Mexico Hydrate Research Consortium (GoMHRC) which has studied a hydrate/carbonate mound in Mississippi Canyon Block 118 (MC118) about 23 kilometers northwest of the spill site in preparation for installing a sea-floor observatory. It is managed by the University of Mississippi. Another source is a remarkable earthquake that occurred about 18 kilometers northeast of the spill site. Fig.1 shows the location of the spill site relative to that of the sea-floor observatory and the earthquake epicenter. Presented below is a discussion of what can be learned from these two sources.