Investigators delving into the causes of the massive gulf oil spill are examining the role of Houston-based Halliburton Co., the giant energy services company that was responsible for cementing the deepwater drill hole, as well as the possible failure of equipment leased to British Petroleum.
Two members of Congress, Reps. Henry A. Waxman (D-Beverly Hills) and Bart Stupak (D-Mich.), called on Halliburton on Friday to provide all documents relating to "the possibility or risk of an explosion or blowout at the Deepwater Horizon rig and the status, adequacy, quality, monitoring, and inspection of the cementing work" by May 7.
Halliburton Chief Executive David Lesar is scheduled to testify before Waxman's energy and commerce committee on May 12, along with top executives Lamar McKay of BP America Inc. and Steve Newman of Transocean Ltd., which leased the drilling rig to BP.
In a statement Friday, Halliburton said: "It is premature and irresponsible to speculate on any specific causal issues.… The cement slurry design was consistent with that utilized in other similar applications… [and] tests demonstrating the integrity of the production casing string were completed."
After an exploration well is drilled, cement slurry is pumped through a steel pipe or casing and out through a check valve at the bottom of the casing. It then travels up the outside of the pipe, sheathing the part of the pipe surrounded by the oil and gas zone. When the cement hardens, it is supposed to prevent oil or gas from leaking into adjacent zones along the pipe.
As the cement sets, the check valve at the end of the casing prevents any material from flowing back up the pipe. The zone is thus isolated until the company is ready to start production.
The process is tricky. A 2007 study by the U.S. Minerals Management Service found that cementing was the single most-important factor in 18 of 39 well blowouts in the Gulf of Mexico over a 14-year period.
Halliburton has been accused of performing a poor cement job in the case of a major blowout in the Timor Sea off Australia last August. An investigation is underway.
In its statement, the company said: "Halliburton originated oilfield cementing and leads the world in effective, efficient delivery of zonal isolation and engineering for the life of the well, conducting thousands of successful well-cementing jobs each year."
The company had four employees stationed on the rig at the time of the gulf accident, all of whom were rescued by the Coast Guard. It had completed the final cementing of the well and pipe 20 hours before the blowout April 20.
But at the time of the accident, "well operations had not yet reached the point requiring the placement of the final cement plug, which would enable the planned temporary abandonment of the well," the Halliburton statement said.
Experts were cautious about attributing blame, pending what are expected to be lengthy investigations by Congress and the Department of Homeland Security, which oversees the Coast Guard.
"What we do know is that highly pressurized oil is coming out of the wellhead with no control possible at this time," said Richard Charter, a drilling expert with the Defenders of Wildlife. "For that to happen, at least three redundant fail-safe mechanisms on and below the rig had to either fail to operate or not have been properly installed."
Charter said a piece of equipment known as the blowout preventer is required to shut automatically, according to regulations by the Minerals Management Service. "And it obviously did not," he said.
Moreover, he added, a manual acoustic shutoff switch could have stanched the flow but may not have been available.
Joe Leimkuhler, past president of the American Assn. of Drilling Engineers, said it was difficult to speculate about the role of cementing in the accident. "The process to place the cement in the well is very similar from job to job, but the details that make up the risk and challenges are specific to each well. You really need the details of the well design and the formation characteristics." He added that only the companies involved have that information.
Some speculation has centered on methane pockets frozen into crystallized formations beneath the seabed that could be warmed by the cementing process and become unstable. A 2009 Halliburton presentation to the drilling engineers association described the challenges of methane hydrates, asking: "When do hydrates become unstable?" and "Will cement hydration cause this outcome?" The presentation noted that "gas release is a challenge for safety and economics."
A company spokesman declined to comment on whether methane hydrates, warmed by cement curing, may have been a factor in the gulf explosion.
More than two dozen class-action lawsuits have been filed against BP, Transocean and Halliburton. BP spokeswoman Sheila Williams said the company was "taking full responsibility" for the spill and would pay for legitimate claims by affected parties.