Review of flow rate estimates of the <i>Deepwater Horizon</i> oil spill

TLDR

This review examines advances in estimating flow rates during the Deepwater Horizon deep‑sea oil spill. The authors compare in‑situ observations with a pressure‑derived, time‑dependent flow‑rate model and use simulations to assess the impact of partial blowout‑preventer deployment. The analyses indicate a flow rate of 50,000–70,000 barrels per day, totaling about 5 million barrels released, with roughly 2 million barrels remaining in the deep sea and all methane retained there, enabling threat‑specific response planning.

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.