Several immediate causes contributed to Macondo blowout

Guntis Moritis
OGJ Production Editor

HOUSTON, Jan. 12 -- The National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling found several immediate causes contributed to the Macondo well blowout on Apr. 20, 2010, although its Jan. 11 report concluded that the root cause was a failure of management by the three main companies involved in drilling the well: BP PLC, the well’s operator; Halliburton Co., which provided cementing services; and Transocean Ltd., the rig's owner and operator.

The immediate causes listed in the report include the cementing, pressure testing, temporary abandonment, kick detection, fluid diversion, and blowout preventer activation procedures.

Because of the ongoing investigation by a government-sponsored forensic analysis team, the commission did not speculate in the report on why the blowout preventers failed to operate as designed.

Factors that may have led to a poor cement job of the production casing string included:

• Running a long-casing string instead of setting a liner. The report said it was unclear whether this directly contributed to the blowout, but running a long string did make it more difficult to obtain a good primary cement job.

• Inadequate number of casing centralizers. Again the report noted that it was unclear whether this was a direct cause but it did find fault with BP's management and centralizer design procedures, as well as poor communication between BP and Halliburton on the centralizer design.

• Float collar conversion. The report said it may never be established with certainty that the float collar valves closed, but it did fault BP personnel for not considering how anomalous pressure readings might increase the cement job's risks. The report noted that because of equivalent circulating density concerns, BP engineers used a very low circulating pump rate, lower than the flow rate needed for closing the float collar valves.

• Not running cement evaluation logs. The report said BP personnel erred by focusing on full returns as the sole criterion for deciding on whether to run a cement evaluation log. It said receiving full returns indicated that cement or other fluids had not been lost to a weak formation but full returns provided limited or no information on where the cement went, channeling, contamination, or stability of the foam cement. Cement evaluation logs although of limited use in a well such as Macondo should have been run, the report said.

• Foam cement instability. The report noted that Halliburton may have pumped foam cement into the well that available tests indicated would be unstable.

Other factors that the report said BP did not adequately consider in assessing the cement job risks included serious lost returns in the cementing zone, no bottoms up circulation, and low cement volume.

Negative-pressure test
The report said the failure to properly conduct and interpret the negative-pressure test was a major contributing factor to the blowout. The report noted that the cement spacer may have clogged the kill line and that pressure data showed that formation fluids were flowing into the well. The commission identified several factors that may have led to an incorrect test interpretation, such as:

• The Mineral Management Service and the industry having no standard procedures for running or interpreting the test and lack of any requirement to run the test.

• BP and Transocean having no internal procedures for running or interpreting negative-pressure tests and not formally training their personnel in how to run them.

• BP Macondo personnel not providing the wellsite leaders or rig crew with specific procedures for performing the negative-pressure test.

• BP not having in place (or not enforcing) any policy that would require personnel to contact the shore office for a second opinion about confusing data.

• Due to poor communication, the personnel performing and interpreting the test may not have had a full appreciation of the context in which they were performing it.

Temporary abandonment procedures
BP’s temporary abandonment procedure also may have contributed to the blowout, the report said. It noted the following problems in the procedures:

• Replacing 3,300-ft of mud below the mudline with seawater because of BP's preference for setting cement plugs in seawater instead of in mud to avoid mud contamination.

• Not setting one or more noncement bridge plugs.

• No evidence that BP evaluated the risks for removing 3,300 ft of mud from the well.

• Setting the planned cement plug as deep as 3,300 ft. The report noted that BP Macondo personnel planned that in order to set the casing lockdown sleeve last in the temporary abandonment sequence to minimize the chances of damage to the sleeve and to generate the 100,000 lb force for setting the sleeve by hanging 3,000 ft of drill pipe below the sleeve.

• Displacing mud from the riser before setting the cement plug was the most troubling aspect of the procedure, the report said. This left only the cement at the bottom of the well as the only barrier to fluid influx.

Kick detection
The report said the drilling crew and other individuals on the rig missed signs that a kick was occurring but it is unclear on why they missed these signals, such as the Sperry Sun mudlogger data between 8:00 p.m. and 9:49 p.m.

These signals included increasing drill pipe pressure after the pumps were shut down for the sheen test at 9:08 pm and the anomalous difference between the drill pipe and kill line pressures recognized by the driller and toolpusher at 9:30 pm.

The report noted the crew may have missed these signals because after 9:08 p.m., they began sending well fluid returns overboard, bypassing the active pit system and the flow-out meter (at least the Sperry Sun flow-out meter). The mudlogger then only performed a visual flow check.

The report recommended that in the future, the rig instrumentation and displays should be improved by installing more sophisticated, automated alarms, and algorithms to alert the driller and mudlogger of anomalies.

The report faulted the current rig operations in which individuals sit for 12 hr at a time in front of displays with the operations requiring the right person to look at the right data at the right time, and then to understand its significance in spite of simultaneous activities and other monitoring responsibilities.

Diversion, BOP activation
The report said the crew should have diverted the flow overboard when mud started spewing from the rig floor to reduce the risk of gas igniting.

It said the crew possible did not do that because of:

• Not recognizing the severity of the situation, although this is unlikely because of the amount of mud spewing from the well.

• Not having much time to act. The explosion occurred about 6-8 min after mud first emerged on the rig floor.

• Most significantly, not having been trained adequately how to respond to such an emergency.

The report recommends that in the future, well-control training should include simulations and drills for such emergencies, including engaging the blind shear rams and triggering the emergency disconnect.

Contact Guntis Moritis at

Related Articles

BHI: US oil rig count rises for first time in 30 weeks

07/02/2015 A sudden 12-unit jump in oil-directed rigs during the abbreviated week ended July 2 represented their first rise since Dec. 5, 2014, and helped lif...

BP to settle federal, state Deepwater Horizon claims for $18.7 billion

07/02/2015 BP Exploration & Production Inc. has agreed in principle to settle all federal and state claims arising from the 2010 Deepwater Horizon inciden...

Shell makes FID on Appomattox deepwater development in Gulf of Mexico

07/01/2015 Royal Dutch Shell PLC has taken a final investment decision (FID) on the Appomattox deepwater development, authorizing construction and installatio...

BHP, Woodside move to decommission Stybarrow field

07/01/2015 BHP Billiton Ltd. and Woodside Petroleum Ltd. have started preparations for decommissioning of the Stybarrow group of oil fields in production lice...

Tullow Oil provides production update on Jubilee, other fields

07/01/2015 Tullow Oil PLC reported that gross production for the Jubilee field offshore Ghana averaged 105,000 b/d in this year’s first half, up from 102,000 ...

Statoil to suspend Scarabeo 5 drilling rig

07/01/2015 Due to overcapacity in its rig portfolio, Statoil ASA said it has decided to suspend Saipem’s Scarabeo 5 dynamically position drilling rig after it...

FWS issues Shell letter of authorization on Chukchi Sea lease

07/01/2015 The US Fish & Wildlife Service issued Shell Gulf of Mexico Inc. a letter of authorization (LOA) related to the potential disturbance of polar b...

USGS: Water usage for fracturing varies widely across shale plays

07/01/2015 The volume of water required to hydraulically fracture wells varies widely across the country, according to the first national analysis and map of ...

Forum extends study of subsea integrity


Work by an industry forum called SURF IM Network, which studies oil and gas subsea integrity management, has been extended by 3 years.

White Papers

UAS Integration for Infrastructure: More than Just Flying

Oil and gas companies recognize the benefits that the use of drones or unmanned aerial systems (UAS) c...

Solutions to Financial Distress Resulting from a Weak Oil and Gas Price Environment

The oil and gas industry is in the midst of a prolonged worldwide downturn in commodity prices. While ...
Sponsored by

2015 Global Engineering Information Management Solutions Competitive Strategy Innovation and Leadership Award

The Frost & Sullivan Best Practices Awards recognise companies in a variety of regional and global...
Sponsored by

Three Tips to Improve Safety in the Oil Field

Working oil fields will always be tough work with inherent risks. There’s no getting around that. Ther...
Sponsored by

Pipeline Integrity: Best Practices to Prevent, Detect, and Mitigate Commodity Releases

Commodity releases can have catastrophic consequences, so ensuring pipeline integrity is crucial for p...
Sponsored by

AVEVA’s Digital Asset Approach - Defining a new era of collaboration in capital projects and asset operations

There is constant, intensive change in the capital projects and asset life cycle management. New chall...
Sponsored by

Transforming the Oil and Gas Industry with EPPM

With budgets in the billions, timelines spanning years, and life cycles extending over decades, oil an...
Sponsored by

Asset Decommissioning in Oil & Gas: Transforming Business

Asset intensive organizations like Oil and Gas have their own industry specific challenges when it com...
Sponsored by
Available Webcasts

Operating a Sustainable Oil & Gas Supply Chain in North America

When Tue, Oct 20, 2015

Short lead times and unpredictable conditions in the Oil & Gas industry can create costly challenges in supply chains. By implementing a LEAN culture of continuous improvement you can eliminate waste, increase productivity and gain end-to-end visibility leading to a sustainable and well-oiled supply chain.

Please join us for this webcast sponsored by Ryder System, Inc.


On Demand

Leveraging technology to improve safety & reliability

Tue, Sep 22, 2015

Attend this informative webinar to learn more about how to leverage technology to meet the new OSHA standards and protect your employees from the hazards of arc flash explosions.


The Resilient Oilfield in the Internet of Things World

Tue, Sep 22, 2015

As we hear about the hype surrounding the Internet of Things, the oil and gas industry is questioning what is different than what is already being done. What is new?  Using sensors and connecting devices is nothing new to our mode of business and in many ways the industry exemplifies many principles of an industrial internet of things. How does the Internet of Things impact the oil and gas industry?

Prolific instrumentation and automation digitized the industry and has changed the approach to business models calling for a systems led approach.  Resilient Systems have the ability to adapt to changing circumstances while maintaining their central purpose.  A resilient system, such as Maximo, allows an asset intensive organization to leverage connected devices by merging real-time asset information with other critical asset information and using that information to create a more agile organization.  

Join this webcast, sponsored by IBM, to learn how about Internet of Things capabilities and resilient systems are impacting the landscape of the oil and gas industry.


Taking the Headache out of Fuel License and Exemption Certificates: How to Ensure Compliance

Tue, Aug 25, 2015

This webinar, brought to you by Avalara, will detail the challenges of tax document management, as well as recommend solutions for fuel suppliers. You will learn:

-    Why it’s critical to track business partner licenses and exemption documents
-    The four key business challenges of ensuring tax compliance through document management
-    Best practice business processes to minimize exposure to tax errors


Emerson Micro Motion Videos

Careers at TOTAL

Careers at TOTAL - Videos

More than 600 job openings are now online, watch videos and learn more!


Click Here to Watch

Other Oil & Gas Industry Jobs

Search More Job Listings >>
Stay Connected