Oil well cement possible rig blow-out cause

Oil well cement possible rig blow-out cause
Published: 05 May 2010

The recently exploded US Gulf rig, Deepwater Horizon,  may have been the result of faulty well cementing procedures. To prevent oil and natural leakage, rig workers pump cement down wells after they’ve finished drilling. This process requires a very particular type of cement and if it is flawed, it can crack or fail to set properly, allowing oil and gas to leak through. If gas escaped through the Gulf rig’s cement, it could have shot back up the well –what is known as a "blowout" – and ignited the fatal blast. In the case of the Deepwater Horizon, workers had reportedly finished pumping cement to fill the space between the pipe and the sides of the hole and had begun temporarily plugging the well with cement. It isn’t known whether they had completed the plugging process before the blast.

Industry specialist Halliburton was said to be in charge of the operation – as it was for cementing a well off the coast of Timor/Australia that blew last August, leaking oil for 10 weeks before it was plugged. Though the investigation continues, an official from the US Minerals Management Service testified that a poor cement job probably caused the explosion. 

Regardless of blame, the process is a risky endeavor, in fact a 2007 study by three US Minerals Management Service officials found that cementing was a factor in 18 of 39 well blowouts in the Gulf of Mexico over a 14-year period. That was the single largest factor, ahead of equipment failure and pipe failure.

The BP oil spill may spur regulators to reevaluate the basic safety of offshore drilling. President Obama has already made clear his intention to suspend expansion of offshore drilling until the Gulf spill has been investigated. If cementing is found to have caused the explosion, then new regulations  that demand safer cementing practices will be in force before sanctioning new drilling off domestic coasts.

Houston-based Halliburton is the largest company in the global cementing business, which accounted for US$1.7bn, or about 11%, of the company’s revenue in 2009, according to analysts. For a six page report on all the technicalities of oilwell cement, log in to CemNet.com and download a detailed six-page report dated January 2006.