On April 20, 2010, Deepwater Horizon suffered a blowout while drilling in the Macondo Prospect, 40 miles
off coast in the Gulf of Mexico. The platform caught fire; two days later, it sank.
Numerous attempts were made to seal the
well, but oil continued to spew into the
Gulf until July 15, when a temporary cap
was put in place. Relief wells then pumped
concrete into the area underneath the wellhead, and the well was deemed permanently sealed in mid-September.
Deepwater Horizon was a semi-sub-mersible, dynamically positioned drilling
platform, or mobile offshore drilling unit
(MODU). In layman’s terms, it was a huge
floating oil rig, capable of adjusting position under its own power, and designed to
drill wells nearly six miles deep.
Blowouts occur when pressurized oil and
gas flow uncontrolled up the drill pipe or
riser to the rig. To prevent this situation,
modern rigs are equipped with blowout
preventers, or BOP stacks, huge structures
that sit on the sea floor directly over the
wellhead. The drill pipe passes through
the BOP stack, which contains a number
of mechanisms—shear rams, bore rams,
annular preventers, and a host of electronic and hydraulic assemblies—that are supposed to shut the well down in the event
of a blowout.
During the initial event and in the weeks
after, numerous attempts were made to
activate the BOP stack—initiation of the
emergency disconnect sequence from the
failing rig, automated dead-man circuitry
on the BOP stack, even remotely operated
vehicles working directly on the stack’s
“autoshear” function. Nothing stopped the
flow of oil.
While the oil industry was working to
shut down the well, the Departments of
Interior and Homeland Security signed
an order to begin an investigation. They
released a competitive Request for
Proposal (RFP) for an analysis of the BOP
operation and failure to seal the well. DET
NORSKE VERITAS (DNV) was awarded a
contract to determine the performance
and possible failure modes of the BOP
stack. DNV pulled together an expert team
of 40 individuals in forensic investigation,
materials specialists, BOP operation, sys-
tems controls, and computer modeling to
address the issues.
Their contract charged them with “
determining the performance of the BOP system
during the well control event, any failures
that may have occurred, and the sequence
of events leading to failure(s) of the BOP.”
To meet this challenge, the DNV team
assembled operations at NASA’s Michoud
facility in New Orleans.
Shane Finneran, project engineer
and team lead in the Computer Aided
Engineering (CAE) Group at DNV’s Materials
and Corrosion Technology Center, was a key
player in the investigation. His team was
involved throughout the Deepwater Horizon
Blowout Preventer Forensic Examination,
leading the 3D laser scanning and computer
DNV faced the problem of quickly constructing and testing numerous computer
models of the stack’s mechanical components. They turned to Abaqus FEA software
from SIMULIA, an application from Dassault
Systèmes’ 3DEXPERIENCE technology.
FEA provided DNV with a rapid, accurate
methodology to simulate and evaluate the
likelihood of different scenarios.
“It would be extremely difficult and gen-
erally cost prohibitive to run physical tests
under the same conditions that exist two
miles under the ocean, re-enacting a blow-
out scenario,” says Finneran. "FEA can pro-
vide the means to perform extensive simu-
lations of many types of damage—ranging
from simplified deformation and buckling
to post-buckling deformation and shear-
ing—with realistic pressure and force mea-
surements built into those simulations.”
The BOP stack, together with several piec-
es of drill pipe, was raised from the well
site and transferred to a holding facility at
The team cleaned, photographed, and
cataloged the stack, disassembling where
necessary to get at its inner workings.
Hydraulic fluids and metal samples were
taken for analysis, the stack’s control mechanisms and their batteries, actuators, and
solenoids were tested, and the casing and
blind shear rams, variable bore rams, and
upper and lower annular preventers were
all visually inspected and 3D laser scanned.
DNV then used the laser scans to construct as-is 3D CAD models of the damaged equipment, especially in the area of
the BSR (blind shear ram) which was the
only ram on the BOP designed to cut the
drill pipe and seal the well bore.
Solid Works software, also from Dassault
Systèmes, was used to convert the original
CAD files into simplified surfaces for use
with Abaqus FEA.
What went wrong
Simply put, a drill pipe is a tube within a
tube. The outer tube is the bore of the well,
and the inner tube the drill pipe, which
contains the drill head. As the drill head
rotates and moves down within the well
bore, pumps aboard the drill platform force
a viscous fluid called "mud" down with it.
The mud lubricates and cools the drill head
while simultaneously flushing out dirt and
cut bits of rock.
FEA Aids Deepwater
Horizon Failure Forensics
By Kip Hanson, Contributor