What More Can Halliburton Tell Us About the Horizon Oil Blowout and Its Risks?
A publicly available Halliburton PowerPoint presentation from last November might tell us a lot about what could have caused the oil blowout, fire and massive oil gushing at the Horizon rig.
Suppose you’re that division of Halliburton that has the dangerous job of "cementing" the drilling hole and the gaps between the hole and pipe. You’ve done this lots of times in shallow water wells, but you’ve learned through previous experience in deep water there’s a particularly difficult problem having to do with the presence of gas that has seeped to the ocean floor and been captured in essentially "frozen" crystallized formations.
The problem is that when you drill into these formations, and then try to inject cement into the hole/gaps to prevent leakage, the curing process for that creates heat. That heat can, if not controlled, cause the gas to escape the frozen crystals. If a lot of gas is released all at once, as could happen during the cement/curing process, it can cause a blowout where the cementing is occurring, or force gas and/or oil up the pipeline to the drilling rig on the surface. And the heat created by the process may be just enough to ignite the gas [or more likely, a spark at the rig — see comments 81, 85], causing the explosion and fire.
Did this happen at the Horizon rig? And if Halliburton already knew about this problem months (years) ago, and knew the risks it might create, why are we just now learning about this?
From Halliburton’s presentation (large pdf), page 10, last November (my bold):
• Shallow water flow may occur during or after cement job
• Under water blow out has happened
• Gas flow may occur after a cement job in deepwater environments that contain major hydrate zones.
• Destabilization of hydrates after the cement job is confirmed by downhole cameras.
• The gas flow could slow down in hours to days if the de- stabilization is not severe.
• However, the consequences could be more severe in worse cases.
Page 13 lists the design objectives but then concedes they can’t all be met at once:
Deepwater Well Objectives
• Cement slurry should be placed in the entire annulus with no losses
• Temperature increase during slurry hydration should not destabilize hydrates
• There should be no influx of shallow water or gas into the annulus
• The cement slurry should develop strength in the shortest time after placement
Conditions in deepwater wells are not
conducive to achieving all of these
The presentation goes on to explain various options for dealing with the risks and assess the relative merits and costs. What’s interesting is that Halliburton appears to have been working at the edge of the technology and was not certain what would happen. Most experience was in shallower waters and no one was certain what would happen in deep waters. It conducted tests, but it’s not clear how complete or realistic those tests were or how costs factored into the choice of techniques. From page 23:
Destabilization of hydrates during cementing and production in deepwater environments is a challenge to the safety and economics
I think we’re about to learn a lot more about how cement cures and interacts with gas-locked crystaline formations in deep water drilling.
Update: See, alternative explanations at The Oil Drum, Tech Talk: Revisiting Oil Well Pressures and Blow Out Preventers . . .. Reacting to a discussion of the cementing issues in the [May 1] LA Times, the author says "it is hard to see from what is known, that this was a cause in this case," though not all commenters there seem convinced.
h/t to Cynthia Kouril who seems to know about how cement cures underwater — tunnels into New York — and found the presentation.
Halliburton presenation below: