Sep 14 2011

Crack Cement 1

Does Cement Crack? – Part 1

New Public Focus on Role of Cement

& Whether ‘Proper Cementing’ Can Prevent Gas Migration,

Contamination of Water Wells & Acquifers


Schlumberger, a world leader in the oil and gas industry, literally wrote the book on "Well Cementing."


“Cementing an oil well is an inherently uncertain process.”
  • National Commission Final Report on Deepwater Horizon disaster
“Even a flawless primary cement job can be damaged by rig operations or well activities occurring after the cement has set.”
  • Schlumberger article in Oilfield Review, Autumn 2003
Cement is coming in for increased scrutiny since last year’s catastrophe in the Gulf of Mexico. The offshore drilling rig Deepwater Horizon sank after an explosion and fire that killed 11 workers and injured 16 others. The resulting oil spill is now considered the second largest environmental disaster in U.S. history.1
The rig was owned and operated by Transocean and leased by BP. Litigation is being discussed in terms of 20-year timelines. The cement seal and blowout preventer are said to have played key roles in the cause of the disaster.2

A National Commission appointed by President Barack Obama in May of last year issued a final report of nearly 400 pages. Among other issues, it discusses “The Inherently Uncertain Cementing Process.”

Until Deepwater Horizon, one would not expect the subject of cement to hold public interest; but the Commission’s analysis unfolds like a scientific detective story. For example, this excerpt and warning about cement (emphasis added):

“The Inherently Uncertain Cementing Process3

Cementing an oil well is an inherently uncertain process. … If done properly, the slug of cement will create a long and continuous seal around the production casing, and will fill the shoe track in the bottom of the final casing string. But things can go wrong even under optimal conditions. … Given the variety of things that can go wrong with a cement job, it is hardly surprising that a 2007 MMS study [Minerals Management Service, a federal regulatory agency] identified cementing problems as one of the ‘most significant factors’ leading to blowouts between 1992 and 2006.”

  • National Commission Final Report, Chapter 4, p. 99

New York State Department of Environmental Conservation (DEC) Commissioner Joe Martens put cement front and center when he made the following declaration and promise at his July 1 press conference:4

“Gas migration is the problem. … Poor cementing jobs were implicated in a lot of those cases [in Pennsylvania] where people ended up with gas in their [water] wells. We think that with proper cementing and this additional layer of casing, that problem will be essentially solved.”

Regulatory promises aside, what is the track record on cement?

By the way, those who interpret any question or challenge to energy industry practice as anti-drilling should read industry statements on the subject of cement.

In fact, Schlumberger, a world leader in the oil and gas industry, literally wrote the book on this subject – titled, Well Cementing (Second Edition, 2006) by Eric B. Nelson (and others). The introduction states (emphasis added):

“Despite recent advances in the cementing of oil and gas wells, many of today’s wells are at risk. … The environmental impact of contaminating a single fresh water aquifer is extremely serious. Therefore, the initial and long-term quality of the cement sheath and bond should be of prime importance to the operator, because it is essential for the safe and successful production of a well.”

This industry leader documents the critical role played by cement – and how easily it can fail and contaminate water aquifers. When you read this book and similar industry papers on the subject, you immerse yourself in serious discussions about the significance of annular gas flow and sustained casing pressure (SCP).

Jerry Lobdill is a retired physicist and chemical engineer in Fort Worth, TX, who has studied the technology of horizontal gas drilling and reviewed the Schlumberger text book. His 6-page paper on the subject is available on the internet.5

As he notes: “The cement job must fully surround the casing, with the casing approximately centered in the [well] bore. There must be no drilling mud or gas channels in the cement or around its interfaces with the [well] bore and the casing. The cement must form a bond with the rock formation and with the casing. If these conditions are not met then gas can migrate from the pay zone up the well bore as far as the surface.”

The Schlumberger book shows U.S. Minerals Management Service data from 22,000 underwater wells in the Gulf of Mexico that indicates cement failures rise with the age of the well.

According to Lobdill’s review of the data: “After 10 years about 40 percent of wells have cement failure. After 30 years, about 60 percent of wells have cement failure; and the failures have nothing to do with the fact that these are underwater wells.”

The Schlumberger Well Cementing book is available on Amazon – generally for $295 and up. For those who value an industry education on cement at a lower cost, there is a 15-page Schlumberger article available on the internet titled, From Mud to Cement – Building Gas Wells. It was published in Oilfield Review, Autumn 2003. See Links and Resources below for a copy.6

Uncontrolled gas migration that can contaminate surface and ground water is a well-known problem in the industry. As the article notes (p. 63):

“Since the earliest gas wells, uncontrolled migration of hydrocarbons to the surface has challenged the oil and gas industry. Gas migration, also called annular flow, can lead to sustained casing pressure (SCP), sometimes called sustained annular pressure (SAP). … Annular flow and SCP are significant problems affecting wells in many hydrocarbon-producing regions of the world.”

Schlumberger lists four categories of likely causes of uncontrolled gas migration in a well (p. 64):

  • Tubing and casing leaks
  • Poor mud displacement
  • Improper cement-slurry design
  • Damage to primary cement after setting

What is about to unfold in New York as the state government appears ready to open the door to shale gas extraction will tell the world whether citizens can believe government promises.

Leaders in the industry such as Schlumberger admit that “many of today’s [gas and oil] wells are at risk” due to ongoing problems in the cement process. Despite that admission, DEC Commissioner Joe Martens promises (emphasis added), “We think that with proper cementing and this additional layer of casing, that problem will be essentially solved.”

And from the same press conference (emphasis added):

“High volume drilling will be permitted on private lands but only under new rigorous and effective measures that mitigate the environmental impacts. We are going to do this safely.”

One notices a pattern when reading industry or government texts. For example, the problem isn’t solved. We think it will be essentially solved.

The Schlumberger article has similar language:

  • “… steps can be taken to mitigate the process.”
  • “… key to minimizing the migration ….”
  • “… the vulnerability of the cement to invasion by gas is reduced ….”

Is it unfair to expect operational excellence in such a complex industrial activity? New York State government is making a big bet that shale gas extraction can be done safely. Yet government lacks confidence in its own bet – that “We are going to do this safely.”

Why else does it exclude the watersheds of New York City and Syracuse and all government land? We’re told those two watersheds are “special,” but if government believes, “We are going to do this safely,” then government land (i.e., taxpayer land) and those special watersheds will be safe, right? Or weren’t we listening carefully?

In part two we’ll take a closer look at New York’s position on shale gas extraction and its reliance on “proper cementing” and a third well casing.

Meanwhile, the draft Supplemental Generic Environmental Impact Statement (dSGEIS) is now accepting public comments for only 90 days. Following are good sources for information.

New York State Department of Environmental Conservation: Revised Draft SGEIS (September 2011)

In addition, check out this helpful guide in the form of a volunteer Wiki website, hosted by the Center for Media and Democracy. It offers a detailed but user friendly guide for the lay person to understand, analyze and respond to the SGEIS document. You’ll find analyses by many knowledgeable folks including Chip Northrup, energy industry investor, and Lou Allstadt, former Executive VP of Mobil Oil Corporation:

Among other issues, the website offers comments on “mitigation” measures including the use of a new third cement casing:

Links & Resources

1, 2 Deepwater Horizon references in Wikipedia

About the drilling rig:

About the explosion:

About the National Commission:

3 National Commission on BP Deepwater Horizon Oil Spill And Offshore Drilling – official website where you can download the final report and other documents:

The Inherently Uncertain Cementing Process – Chapter Four, p. 99. See also pp. 99-103 which goes into detail about “The Cementing Design: Critical Decision For A Fragile Formation” and much more.

4 Webcast of DEC Commissioner Joe Martens press conference, July 1, 2011

5 “Why Gas Well Drilling is Environmentally Risky,” by Jerry Lobdill, April 2, 2011 – the paper is available at this Mendeley link:

6 From Mud to Cement – Building Gas Wells, Schlumberger, by Claudio Brufatto and others, Oilfield Review, Autumn 2003, pp. 62-76 – Pdf file:  ‘From Mud to Cement’ article

NOTE: This article is cross-posted on the Accountability Central website at this link:  Accountability Central is part of the Governance & Accountability Institute, Inc.



2 Responses

  1. Anonymous Says:

    “Proper Cementing” does not mean perfect cement. BTW, there is nothing such as perfect cement in O&G wells. Even if there was PERFECT cement, initially, many things can and will happen over the life of the well such as corrosion, casing collapse, etc, etc, etc. that will allow migration of fluids along the casing strings.
    In the old days of the zero pressure oil wells, with West Texas Pumpers at the surface, poor or deteriotating cement/casing/couplings were not as important as is the case with today’s high pressure shale gas wells. This added pressure is a serious factor when cement is poor or deteriorates over time, fracking occurs, so as to cause water aquifer contamination. There are many, many aspect to this issue. Don’t get me started.

  2. laurie Says:

    Regarding aging to failure of cement in wellbores – please see both posts:

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