Worst Case Discharge (WCD) is a calculation used by the

Bureau of Ocean Energy Management, Regulation and Enforcement The Minerals Management Service (MMS) was an agency of the United States Department of the Interior that managed the nation's natural gas, oil and other mineral resources on the outer continental shelf (OCS). Due to perceived conflict of intere ...

to determine the maximum flow rate for an offshore oil well in the event of an oil spill. WCD first came to prominence in the aftermath of the

Deepwater Horizon Oil Spill The ''Deepwater Horizon'' oil spill (also referred to as the "BP oil spill") was an industrial disaster that began on 20 April 2010 off of the coast of the United States in the Gulf of Mexico on the BP-operated Macondo Prospect, considere ...

to determine potential liability if another oil spill were to occur.

History

The now defunct

Minerals Management Service The Minerals Management Service (MMS) was an agency of the United States Department of the Interior that managed the nation's natural gas, oil and other mineral resources on the outer continental shelf (OCS). Due to perceived conflict of inter ...

planned to implement Worst Case Discharge studies before the

though the first actual was performed in August 2010 to model the Deepwater Horizon spill. In January 2011, several major oil and gas companies were allowed to resume deepwater drilling while Worst Case Discharge studies were being completed. In March 2011, the Worst Case Discharge study on the Deepwater Horizon Oil Spill was released to the public in the

Flow Rate Technical Group The Flow Rate Technical Group is a group of scientists and engineers from the United States federal government, universities, and research institutions created May 19, 2010, for an official scientific-based estimate of the flow of oil in the Deepw ...

final report.

Calculation methods

Analytical equations

Analytical equations are the simplest method for calculating WCD. However analytical equations cannot account for the rapid change in pressure and saturation near the well bore and have been replaced by simulation modeling.

Reservoir simulation

Reservoir simulation is the method used by the BOEMRE to calculate WCD as simulation can accurately model the rapid changes near well bore that occur in an uncontrolled blow out event. The BOEMRE currently uses the Merlin

finite difference A finite difference is a mathematical expression of the form . If a finite difference is divided by , one gets a difference quotient. The approximation of derivatives by finite differences plays a central role in finite difference methods for t ...

simulator and

nodal analysis In electric circuits analysis, nodal analysis, node-voltage analysis, or the branch current method is a method of determining the voltage (potential difference) between " nodes" (points where elements or branches connect) in an electrical circuit ...

package to perform all WCD studies since using the software to determine the official flow rate for the

. Engineers typically use radial modeling to calculate WCD as a radial model can employ sufficiently small grid cell sizes around the well bore that increase in volume as cells extend into the

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials ( gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characteris ...

. Full field modeling is generally only needed if a geologic barrier like a fault or pinch out is close enough to the well being studied there is pressure interference. Engineers also need to calculate the highest rate in each combination of geologic layers as the well is drilled. The WCD rate can be higher in certain cases if specific layers blowout rather than the entire reservoir as different combinations of aquifers, gas layers, and oil layers can limit or enhance flow.

References

External links

BOEMRE Worst Case Discharge
{{DEFAULTSORT:Deepwater Horizon Oil Spill Deepwater Horizon oil spill