As oil continues to spill into the Gulf of Mexico from the MC252 “Maconda” well, fingers are starting to be pointed at the various companies involved in the disaster. Thus it is that Tim Probert, president, Global Business Lines and chief HSE officer for Halliburton, testified before the Senate’s Committee on Energy and Natural Resources May 11.
This is a significant development in the ongoing investigation because cement failure has been floated as a possible cause for the blowout. Halliburton had four workers on the rig at the time of the explosion, and all four made it safely home, so their recollections have helped the company piece together its potential culpability.
Below is an excerpt of Probert’s testimony. The full document and the diagram he refers to are available at http://www.halliburton.com/public/news/pubsdata/press_release/2010/ProbertTestimony.pdf.
I need to start this section with an important statement of disclosure. Halliburton, as a service provider to the well owner, is contractually bound to comply with the well owner’s instructions on all matters relating to the performance of all work‐related activities. It is also important to understand the roles and responsibilities of the various parties involved in the construction of a well. The construction of a deepwater well is a complex operation involving the performance of numerous tasks by multiple parties led by the well owner’s representative, who has the ultimate authority for decisions on how and when various activities are conducted.
Attached to this testimony is an illustration showing the approximate depths and positions of the casing and liner strings set in this well. In addition, the approximate position of the various cement placements is illustrated, which is consistent with the well design. It should be noted that cement is used at specific designated spots and is not designed to be a complete barrier through the entire wellbore.
Cement can be used to isolate formation fluids, to prevent movement of these fluids between formations, and to bond and support the casing. A mixture of cement, water, and chemicals is combined in a slurry that can be pumped into position around the outside of steel liners and casing.
There are many external factors that impact the design and execution of a cement job. These include the variability in the hole geometry, relative location of hydrocarbon zones, hydrocarbon content, and the prior condition of the wellbore and associated fluids as determined by the drilling fluid provider. Casing strings are typically run with devices to centralize the casing concentrically in the wellbore and prevent incomplete displacement of drilling fluid, or “channeling.”
While every effort is made to complete a cement job with the highest levels of mechanical and hydraulic integrity, the above-mentioned well conditions may prevent this. Confirming cement integrity after placement would require the well owner to direct the wireline provider to obtain cement evaluation logs. Based on the findings of these logs, the well owner can elect to perform remedial action by perforating the casing and “squeezing” cement into remaining voids to improve the integrity of the original cement.
The centralizer placement on the production casing, the drilling fluid conditioning program prior to cementing, and the cement slurry and placement design used for this well were implemented as directed by the well owner. However, as shown in the attached diagram, by design there is no continuous cement column throughout the entire wellbore.
Approximately 20 hours prior to the catastrophic loss of well control, Halliburton had completed the cementing of the ninth and final production casing string in accordance with the well program. Following the placement of 51 barrels of cement slurry, the casing seal assembly was set in the casing hanger. In accordance with accepted industry practice, as required by MMS (the US Minerals Management Service) and as directed by the well owner, a positive pressure test was then conducted to demonstrate the integrity of the production casing string. The results of the positive test were reviewed by the well owner, and the decision was made to proceed with the well program.
The next step included the performance of a “negative” pressure test, which tests the integrity of the casing seal assembly and is conducted by the drilling contractor at the direction of the well owner and in accordance with MMS requirements. We understand that Halliburton was instructed to record drill pipe pressure during this test until Halliburton’s cementing personnel were advised by the drilling contractor that the negative pressure test had been completed, and were placed on standby.
We understand that the drilling contractor then proceeded to displace the riser with seawater prior to the planned placement of the final cement plug, which would have been installed inside the production string and enabled the planned temporary abandonment of the well. Prior to the point in the well construction plan that the Halliburton personnel would have set the final cement plug, the catastrophic incident occurred. As a result, the final cement plug was never set.
Halliburton is confident that the cementing work on the Mississippi Canyon 252 well was completed in accordance with the requirements of the well owner’s well construction plan.
Bill Herbert of Simmons & Co., in his “Simmons Morning Energy Note,” takes BP to task for reassigning blame. “One bizarre and distasteful aspect of this tragedy has been BP’s continuous refrain since the blowout to lay a disproportionate share of the blame on [Transocean, Halliburton, and Cameron] by inferring that it only had an arm’s length engagement/involvement in this whole process, which is patently absurd,” he writes. “Sure, the service companies are implementing and even recommending solutions, but the operator (BP) has the final say with regard to well construction architecture and signs off on all of the service solutions provided.”
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