By Seth Richardson
The media has been generally remiss in describing to us how the disaster in the Gulf of Mexico happened, and everybody’s too busy pointing fingers and talking about the impending damage from the oil to take the time to do so, so I’m going to have to give it a shot myself.
After consulting with some experts, here’s a layman’s explanation of how deep-sea oil drilling works and what likely happened beneath the Deepwater Horizon.
First, some basics on oil drilling. Take a soda straw and and the ink reservoir and tip from a Bic ballpoint pen. Now insert the ink pen into the soda straw. Now jam the whole thing into the dirt, and twist and push the ballpoint parts downward. That’s pretty much how an oil drilling rig works. The ink reservoir tube is the “drill stem,” the ballpoint tip is the “tool” or “drill bit,” and the soda straw is the “casing.”
As the well is drilled, drilling mud, a chemical concoction used to lubricate the drill bit and carry the rock chips the bit creates, is pumped down through the center of the drill stem, and it flows back up out of the hole along the outside of the drill stem. As the hole gets deeper, the casing is slipped down into the hole with the drill bit and drill stem inside the casing. Sections of casing are added to this stack as the hole is drilled.
At the top of the stack of casing, which does not extend to the bottom of the hole where the oil is, is a “blowout preventer,” or BOP. This is a complex device that has at least four different ways of sealing the well casing and preventing oil from flowing up the casing uncontrolled. It has a hydraulic ram that can crush both the casing and the drill stem shut, another hydraulic ram with a shear plug that can punch a hole through both the casing and the stem, creating a horizontal plug in the well, an “annular plug” which can seal the casing but not the drill stem, and a pair of fittings at the very bottom of the BOP called the “kill” and “choke” ports, through which high pressure fluid can be pumped to create pressure in the casing to keep oil from flowing up the pipe.
Typical BOP used on land
As the well is drilled, and the casing is rammed into the hole, there is space between the rock wall of the hole the tool is boring and the 1/2 inch thick wall of the casing pipe. This is the space that is cemented in order to seal the space around the casing and the borehole. This must be done to prevent the high-pressure oil from flowing up the outside of the casing, where it cannot be controlled or captured.
Once the casing is cemented properly, there is a strong seal around the casing that will withstand the upwards pressure of the oil.
During drilling, the upwards pressure of the oil is balanced by the weight and pressure of the drilling mud being pumped down the drill stem, so the oil cannot flow upwards. This pressure is kept on until the well is cemented and the cement has hardened. Then the pressure can be let off, and the valves on the BOP closed to cap the well, and the whole system is sufficient to withstand the pressure of the oil.
What seems to have happened here is a failure in the cementing process, likely caused by the nature of deep-water drilling. At the depths involved, methane gas is a frozen liquid, not a gas. The pressure turns it into a liquid, and the temperature turns it into an icy slush or solid.
As the well is drilled, it may pass through layers of frozen liquid, which so long as it stays frozen, is not a problem. But the cementing process generates heat. Cement, as it hardens, chemically changes into concrete, and in the process, it heats up.
To cement the well, the cement is pumped down the drill stem, from which the tool has been removed. The cement flows out the end of the drill stem and is forced under pressure back upwards towards the surface along the outside of the casing pipe. Normally, a calculated amount of cement is injected into the well as engineers observe the pressure, and when completed, the cement has formed a strong seal around the casing pipe for hundreds or thousands of feet upwards from the bottom of the casing, sealing the bore hole and setting the casing in place.
In this case, however, it appears that there were fissures in the rock strata filled with methane ice, and when the cement hit a fissure or pocket, the heat of the cement curing melted the methane ice. When melted, the ice becomes gas, and the pressure rises dramatically, which can, if the pressure outside the casing and inside the casing are not carefully kept in balance, rupture the casing somewhere above the bottom of the casing, driving methane gas into the casing on the outside of the drill stem. This gas begins to flow upwards and at the same time, the cement, which is supposed to flow up the outside of the casing and fill the space between the casing and the bore hole, can flow into the fissure that contained the methane ice, which means that the desired seal around the outside of the casing cannot be guaranteed.
The methane gas flowed up the casing to the drill rig, a mile above, expanding all the way as the pressure dropped, and exploded. The rig sank, and the riser pipe, which is similar to the casing but is attached to the top of the BOP, fell to the side, kinking and cracking.
Three of the four safety systems in the BOP, the shear ram, the blind ram and the annular valve all failed or worked only partially for some unknown reason, so the flow of oil was not cut off at the BOP as intended, and is now flowing through the casing, drill stem and riser. The drill stem has been capped where it protrudes from the riser pipe, but the broken riser pipe end, with the drill stem inside it, is leaking, as is a crack near the BOP where the riser and drill stem folded over as it sank to the bottom.
The problem BP engineers are facing now is that they are not certain of the strength of the cementing, and if they plug the well, they don’t know if the pressure from the oil will cause the cement to fail and allow the oil to flow up the outside of the casing rather than the inside, which would make the leak completely uncontrollable.
At the moment, the oil is coming up the casing into the riser, where hopefully it can be captured and pumped to the surface, which is preferable to blowing out the cement and ending up with a massive, uncontrolled release of oil.
So, BP is reluctant to try to plug the well, lest the cement fail, and, according to my sources, are pinning their hopes on the lateral well they are drilling in hopes of intercepting the well bore so they can pump the whole well bore full of cement to plug it. The problem is that it’s going to take a long time to drill the intercept well, and in the past, such attempts have rarely hit the 12 inch wide borehole from four miles away on the first try. The last time this was attempted, in Ixtoc, Mexico, it took six attempts to hit the bore. If it takes two months per attempt, it could be a year before they manage to shut the well down that way.
But, BP may be preparing to try a “junk shot,” which is injecting bits of rubber and other debris through the kill and choke lines to clog up the annular valve at the top of the BOP and stop the flow of oil that way, even though they risk blowing out the cement, which could lead to an even greater and faster release of oil that would be completely uncontrollable, and likely cannot be contained and pumped away by dropping a structure over the BOP.
Why it happened will take months to determine, but I hope I’ve given you a better idea of how it happened, and what the risks are.
Hi Seth – please can you send me a hi-res version of your ‘Figure 1′ from this article as I’d like to use in a report if possible? Thanks
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Guys and Gals… a couple of more things . The EDS did not activate ( Emergency Disconnect System ) which disconects the BOP from the Marine Riser and thus the path of Methane Gas to the Rig. And ….at least …. if this device had worked We would still have the leak but the Rig would not have blown up and (11) fine Human Beings would not have perished . The idea has been suggested that a drill string coupling was what one of the “shear” BOP ‘s contacted when trying to close and it is My understanding that a shear BOP cannot shear a drill string coupling ( and why they have -two- “shear” Bop’s in line ( so that one of them WILL NOT contact a coupling at any location on the drill string)) It is also My understanding that BOP’s are to be redesigned as a result of this and other blowouts … this “blowout ” thang is nuttin’ new … peace B…..
Thanks for the compliment, Barry. I have also heard rumors that the number of centering devices used to keep the casing in the center of the bore-hole was reduced. The complete failure of all of the BOP systems is the core of this debacle. While there may have been several shortcuts in both drilling and cementing, as you suggest, all of those modes of failure were accounted for by the existing safety procedures in the form of the BOP, and it’s multiple failures are the main concern.
Given the multiply-redundant safety cut-off systems in the BOP, I’m not entirely certain that it is fair to excoriate BP and the drillers as much as has been done. No shortcut is acceptable, but poor cementing and casing ruptures are known risks of oil well drilling that the BOP is supposed to cover. I will be very interested to see what they find inside the BOP when they finally plug the well and bring the BOP up for inspection.
In the end, oil drilling is a risky business, but deep-water drilling actually has a very good record, particularly in the Gulf. There are thousands upon thousands of wells out there, and this is the first such multiple failure.
The problem we face now is that this is being used as a political wedge for Obama to shut down drilling, further compromise our economy and energy independence, ram cap-and-trade through and otherwise force his green agenda on us, from which his good friend George Soros will benefit financially.
Very nice and complete explanation Mr. Richardson… It’s the best no B.S explanation I have heard yet !!!! I have spent the last 3-4 weeks intensely studying all aspects of this and other drilling operations /industry/Companies…. via Schlumbergers, Wikipedia, U tube animations ( very helpfull) indutry Manufactuers and “Drilling Ahead” a Drilling Profession Social Networking site ( VERY helpfull) . A few additions to Your assesment … The reason for the migrating Methane gas into the bore could be the result of too fast ROP ( rate of progression ) in the later stages of drilling.. and the Strata was “fractured” mechanically , usually when Drillers want the oil to flow they chemically “fracture” the strata , but only after the well is in control. As the completion of this well was over budget ( $500,000/day ) and over time, the incentive to “drill for ‘kicks” ” was very high. Haliburton was reported to have complained that thay were being pressured to speed up the curing times (normally 12-24 hours)on the final casing cement job and thus would explain (1) the excessive heat generated by having to add more catalyst the cement. (2) the incomplete curing job on the final casing string . It was also reported that Haliburton had complained about the casing NOT being centered in the bore hole , which creates thin and thick layers of concrete on either side of the casing and between the bore hole and when pressure tested will fracture the thin side of the cement job, And which reportedly (on U tube animation vids ) is the reason the ‘shear” BOP did not completely shear the drill string ( like an old pair of worn out scissors !!!) The drilling mud was removed from the annulus and replaced with seawater ( drilling mud is —10% the budget on a drill job) to be used somewher else ( BAD choice) with out this fatal mistake this disaster probably would not have happened ) So… Thank You Mr. Richardson for shedding a much needed practical light on this very complicated and technical story . Most news oranizations did not have a clue as to what they were talking about … nice job.. Regards, Barry Pultz
What happened? How about BP surrender the Black Box…. (VDR) Voyage Data Recorder???
Nothing new the Very same thing happened in Nov 2009- Jan 2010 Atlas Platform Blowout Montara. 5 months to stop the Blow out………..
http://www.flickr.com/photos/skytruth/sets/72157622226354812/detail/
Thanks HugoV for the Post. …..A Business decision, Management, Like the 3 Little Pigs Memo from BP regarding the Living Quarters for the Pigs(Employees) on site Texas City Refinery. 15 dead 175 injured. A Dead pig only costs BP $10 million. Cheaper than Blast proof Dorms….
http://www.thedailybeast.com/blogs-and-stories/2010-05-25/shocking-bp-memo-and-the-oil-spill-in-the-gulf/
The 3 Pigs costing oversight might have been building too safe a dorms… too many little pigs not killed in blast. Should have gone with straw A better Business choice. But I am not a Harvard MBA or even a CPA…..
Bob0,
The quality of a cement job is not the same as lives.
I feel you’re mixing everything in the same basket. I wish we can make a constructive discussion.
Agree with you on the value of life, they should never be part of a business decision.
But lives are also considered (as a cold number in $) in business and moral decisions (vaccines, roads, oil wells, etc).
I insist, the main issue (for now) is the power of LOBBY.
Big companies (not only energy) are factually changing legislation.
The process of controlling their actions (and the way they evaluate risk) must be subject to a different type of control.
Nothing new or too difficult. IE see what controls and institutions regulate and control Oil Co’s in the North Sea.
And I agree with you, nothing new. The same mistakes, the same vices and the same moral wrongdoing,
Oil and Gas companies are moving offshore because there is better chances of profit there. The easy oil is fading away in land or shallow waters, there is a clear trend (somewhat changing on mature fields, yet not easy).
Wouldn’t the risk of oil well-related disasters diminish if the government allowed more onshore drilling and shallow-water offshore drilling? Isn’t the BP spill an unintended consequence of a myopic environmental policy that forces exploration at risky depths?
I’m for drilling anywhere there’s oil, but I doubt that if oil companies had a choice they’d build platforms 48 miles from shore, where their technical difficulties increase exponentially.
Suddenly we all became experts and critics of companies, government, regulators and whoever does or act in this disaster.
I’m a 34 years international oil experience veteran. I never worked in the oil field in the USA. I have no affiliation whatsoever to the involved companies (I work as an instructor).
I worked for several Oil and Service Co. at field, within technology groups and supervision.
More than 20% of ALL the Liner cementing jobs (worlwide) end up with a lack of isolation and severe problems that defeats the purpose of almost any well.
This is not new, every Company will try to fix the problem (Most of the time is done right the first time). But yes, some of them just neglect the problem. This is not unlawful or even a bad practice, it is a business decision.
Everything above the liner is designed to keep the well safe and controlled, even with a bad cementing job. Lack of common sense (managerial) and horrendous lack of regulations caused all the barriers to fail.
There is no doubt in my mind that the major problem is far from our (technical) discussions.
The same level of freedom (may be excessive?) is extended to food, drugs, alcohol, tobacco, firearms, finances, investments firms, insurance, etc. etc.
Whenever a group or individual wants government involvement, more regulation and more control we heard the irrational claims (leftist, liberals, immoral, big brother myths, anti American, etc).
Reality will keep hitting very hard on us. Until we realize that we MUST take a look on how they control Health Insurance (look everywhere and we’ll find better and worse ways. But we MUST look). The same apply to oil exploration, production and refining. Look at regulations on Norway, Brazil and the UK. All of them have achieved acceptable levels of risk (which will never be eliminated).
The main issue here is LOBBYING and how we, as a powerful nation, tolerate, admit and vote for people that receives MONEY from them.
Nothing good have come from our legislative in the last 20-30 years.
We are wasting our time in technical discussions, fingerpointing, etc.
Our mission is to keep profit driven companies from factually making or grossly changing legislation.
Or we can wait, see and suffer the next crisis with diseases, food, finances, energy, etc.
If profit is the driver, then there is no hope.
Money is inversely proportional to the need. The more you have the more you want (and the less you need).
Call me socialist, may be I’m enjoying the freedom to be one.
Some logical, humble reasoning is desperately needed ….
CSaction wrote: “With the neocon stooges Gale Norton and Julie MacDonald in charge for the last 8 years, they could do anything they wanted to do and this is the result of DEregulation.”
Yeah, it makes a lot of sense that BP was just aching to blow out a well and sink a multi-billion dollar drilling platform and make themselves liable for more billions in cleanup and damages just so they could thumb their noses at federal regulations.
Not….
“What seems to have happened here is a failure in the cementing process, likely caused by the nature of deep-water drilling.”
No.
“A 2007 MMS study found that cementing problems were associated with 18 of 39 blowouts between 1992 and 2006, and 18 of 70 from 1971 to 1991. There were 17 blowouts in the earlier period where contributing factors”
Halliburton did a variety of services on the rig, including cementing and had completed the cementing of the final production casing string approximately 20 hours prior to the explosion.
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 a spark at the rig can, causing the explosion and fire.
From Halliburton’s own regs:
• 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 objectives simultaneously-
That’s the key and they admit it in their own docs.
With the neocon stooges Gale Norton and Julie MacDonald in charge for the last 8 years, they could do anything they wanted to do and this is the result of DEregulation.
Only the top cabinet of the MMS and Interior has changed and the neocons are still in most positions there and still doing the bidding of Big Oil to rape us all.