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

North Reggane gas project development drilling starts in Algeria


The North Reggane consortium has started development drilling at its gas project in the Algerian Sahara.

Inpex starts development drilling at Ichthys field


Inpex Corp. has started development drilling in Ichthys gas-condensate field in the Browse basin, about 200 km offshore Western Australia.

Anadarko reports 2014 loss, remains upbeat about Wattenberg

02/03/2015 Anadarko Petroleum Corp. announced a 2014 net loss of $1.75 billion, or $3.47/share diluted, including a net loss of $4.05 billion associated with ...

CNOOC cuts capital budget, starts production from Jinzhou 9-3

02/03/2015 CNOOC Ltd. is slashing its capital budget for 2015 by 26-35% to $11.25-12.86 billion compared with last year’s budget. Capital expenditures for exp...

Obama’s proposed fiscal 2016 budget recycles oil tax increases

02/02/2015 US President Barack Obama has proposed his federal budget for fiscal 2016 that he said was designed to help a beleaguered middle class take advanta...

Mud volcanoes show gas hydrates potential in India's Andaman Islands

02/02/2015 Minutes after the M9.0 Sumatra-Andaman earthquake in 2004, mud volcanoes erupted on Diglipur Island in North Andaman. The eruptions resulted in an ...

BHI: Texas anchors 90-unit plunge in US rig count

01/30/2015 The US drilling rig count plunged 90 units—a majority of which were in Texas—to settle at 1,543 rigs working during the week ended Jan. 30, Baker H...

Chevron, BP, ConocoPhillips join to explore, appraise Gulf of Mexico leases

01/28/2015 Chevron Corp. subsidiary Chevron USA Inc., BP PLC unit BP Exploration & Production Inc., and ConocoPhillips Co. have pledged to work together t...

Carrizo cuts drilling, completion spending by 35%

01/27/2015 Carrizo Oil & Gas Inc., Houston, is cutting its drilling and completion capital expenditure plan for the year by 35% to $450-470 million, but e...
White Papers

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

Squeezing the Green: How to Cut Petroleum Downstream Costs and Optimize Processing Efficiencies with Enterprise Project Portfolio Management Solutions

As the downstream petroleum industry grapples with change in every sector and at every level, includin...
Sponsored by

7 Steps to Improve Oil & Gas Asset Decommissioning

Global competition and volatile markets are creating a challenging business climate for project based ...
Sponsored by

The impact of aging infrastructure in process manufacturing industries

Process manufacturing companies in the oil and gas, utilities, chemicals and natural resource industri...
Sponsored by

What is System Level Thermo-Fluid Analysis?

This paper will explain some of the fundamentals of System Level Thermo-Fluid Analysis and demonstrate...
Available Webcasts

The Alternative Fuel Movement: Four Need-to-Know Excise Tax Complexities

When Thu, Jun 4, 2015

Discussion on how to approach, and ultimately embrace, the alternative fuel market by pulling back the veil on excise tax complexities. Taxes may be an aggravating part of daily operations, but their accuracy is crucial in your path towards business success.


On Demand

Prevention, Detection and Mitigation of pipeline leaks in the modern world

Thu, Apr 30, 2015

Preventing, detecting and mitigating leaks or commodity releases from pipelines are a top priority for all pipeline companies. This presentation will look at various aspects related to preventing, detecting and mitigating pipeline commodity releases from a generic and conceptual point of view, while at the same time look at the variety of offerings available from Schneider Electric to meet some of the requirements associated with pipeline integrity management. 


Global LNG: Adjusting to New Realities

Fri, Mar 20, 2015

Oil & Gas Journal’s March 20, 2015, webcast will look at how global LNG trade will be affected over the next 12-24 months by falling crude oil prices and changing patterns and pressures of demand. Will US LNG production play a role in balancing markets? Or will it add to a growing global oversupply of LNG for markets remote from easier natural gas supply? Will new buyers with marginal credit, smaller requirements, or great need for flexibility begin to look attractive to suppliers? How will high-cost, mega-projects in Australia respond to new construction cost trends?


US Midstream at a Crossroads

Fri, Mar 6, 2015

Oil & Gas Journal’s Mar. 6, 2015, webcast will focus on US midstream companies at an inflection point in their development in response to more than 6 years shale oil and gas production growth. Major infrastructure—gas plants, gathering systems, and takeaway pipelines—have been built. Major fractionation hubs have expanded. Given the radically changed pricing environment since mid-2014, where do processors go from here? What is the fate of large projects caught in mid-development? How to producers and processors cooperate to ensure a sustainable and profitable future? This event will serve to set the discussion table for the annual GPA Convention in San Antonio, Apr. 13-16, 2015.

This event is sponsored by Leidos Engineering.


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