Review of flow rate estimates of the Deepwater Horizon oil spill

Abstract

The unprecedented nature of the Deepwater Horizon oil spill required the application of research methods to estimate the rate at which oil was escaping from the well in the deep sea, its disposition after it entered the ocean, and total reservoir depletion. Here, we review what advances were made in scientific understanding of quantification of flow rates during deep sea oil well blowouts. We assess the degree to which a consensus was reached on the flow rate of the well by comparing in situ observations of the leaking well with a time-dependent flow rate model derived from pressure readings taken after the Macondo well was shut in for the well integrity test. Model simulations also proved valuable for predicting the effect of partial deployment of the blowout preventer rams on flow rate. Taken together, the scientific analyses support flow rates in the range of ∼50,000-70,000 barrels/d, perhaps modestly decreasing over the duration of the oil spill, for a total release of ∼5.0 million barrels of oil, not accounting for BP's collection effort. By quantifying the amount of oil at different locations (wellhead, ocean surface, and atmosphere), we conclude that just over 2 million barrels of oil (after accounting for containment) and all of the released methane remained in the deep sea. By better understanding the fate of the hydrocarbons, the total discharge can be partitioned into separate components that pose threats to deep sea vs. coastal ecosystems, allowing responders in future events to scale their actions accordingly.oil budget | particle image velocimetry | manual feature tracking

Diverse, rare microbial taxa responded to the Deepwater Horizon deep-sea hydrocarbon plume

“…In striking contrast to the slow natural gas and oil inputs, the DWH oil discharge released 2.6-3.6 × 10 5 t gas and 5.9-8.4 × 10 5 t oil McNutt et al, 2012), exposing the Gulf's microbial populations to locally unprecedented hydrocarbon loads. The temporal impact of the deepwater plume on the native bacterial communities was surveyed between March 2010 and November 2012, in conditions hereafter termed 'pre-discharge' (PRE), 'discharge' (DUR) and 'postdischarge' (POST).…”

Hydrocarbon-degrading bacteria enriched by the Deepwater Horizon oil spill identified by cultivation and DNA-SIP

“…An estimated 4.1 million barrels of crude oil entered the Gulf of Mexico over a period of 84 days (20 April to 15 July 2010) (McNutt et al, 2011). One distinctive feature that set this spill apart from other historic oil spill incidents at sea was the duration of the leak and depth at which it occurred (1500 m below the sea surface).…”

Impact of Photooxidation and Biodegradation on the Fate of Oil Spilled During the Deepwater Horizon Incident: Advanced Stages of Weathering

“…It has been estimated that between 4.2 and 4.9 million barrels of oil were released making it the largest accidental oil spill in history. [1][2][3] Numerous studies have examined the fate and impact of released Macondo oil within the plume [4][5][6][7][8] , on the surface of the Gulf 5,9,10 , buried in ocean sediments (either directly or as marine snow) 6,10 , in marshes [11][12][13][14] , and on beaches. 10,12,14-19 Not surprisingly, the environmental fate of the oil was influenced by many well documented weathering processes.…”

“…[1][2][3] This crude oil was transformed by a number of weathering processes and eventually converted into sand patties that are largely composed of partially oxidized organic compounds termed 'oxyhydrocarbons'. 20,21,25,54 The weathered sand patties may remain on the seafloor or be transported to beaches where they can settle in the swash zone.…”