Melted Shallow Gas Hydrates Blowing Through Burst Disk Triggered Macondo

It now seems highly probable that the offshore oil and gas industry’s infamous and long feared Gulf of Mexico Gas Hydrates [GH] caused drilling blowout was ultimately the cause of the horrors which occurred at the Block MC252 Macondo well  in the GoM in April 2010. This potential trigger has been well documented in the technical literature for many years, although probably required the compounding sequence of drilling mistakes that happened as BP continually adjusted their threadbare well design “on the hoof”. The incompetence and arrogance of BP has become breathtaking in recent years and this hydrate melt blowout was a direct result of that. Wells have been drilled through frozen gas hydrate formations in the Gulf of Mexico before, and the potential hazards were understood. It would be very surprising if the 1st trial finding arrived at was not gross misconduct and wilful misconduct, but that remains to be seen. This is and will continue to be a highly politicised situation. The question that arises is: Should a technique of cementing together smaller and smaller steel pipes in much the same way as done a century ago on land continue to be used in drilling very deep wells in very deep water in such hazardous geological situations?

A number of individuals, including senior members of the Deepwater Horizon Study Group [DHSG] have believed for some time that there was some sort of “casing breach” higher up in the drillstring. If one reads the events surrounding the workings of the US federal Steven Chu led team when they were “embedded” in the BP Houston office prior to the attempted Top Kill, one can see that there was a strong suspicion/fear that a casing breach or fracture had occurred or that one of the three 16” casing “burst disks” had blown. There is a remarkable first hand witness account held by the DHSG written in the immediate aftermath. Reading that, it is obvious to anyone who has any understanding about what an expanding Gas Hydrate generated methane cloud would consist of and what it would look like spreading across and flooding a drilldeck that this was the trigger. The cold methane cloud was quickly followed by mud being siphoned up the inner drillstring followed by oil as the shoe track at the well bottom was blown to pieces under an immense suction force at reservoir level. The DHSG have produced work of great diligence and fair-mindedness, but for whatever political reasons, have stayed away from the potential hydrate/burst disk scenario, presumably since such a scenario is effectively “unprovable”.

A senior member of the DHSG e-mailed me on the 14th December 2012 in response to a broad outline of my views I supplied to him:

“Thank you for the updates.

I share your observations and conclusions.

The civil litigation trial (Phase 1 – developments to the blowout) is scheduled to resume February 25th. the Phase 2 (post blowout developments) trial is scheduled to start “late summer 2013). 

I do not think that much more of the developments, including the current surveys, will become public until the litigation processes force them to become public.

Thank you again for the insights and www links”

What is remarkable when one considers the geological context is that the words “Gas Hydrate”, “Methane Clathrate”, “Burst Disk” and “Shallow Water Flow” do not appear at all in any of the thousands of 1st trial transcript documents. When one considers where Macondo was drilled and its location in relation to the well known gas hydrate bearing zones in the Gulf of Mexico, this is odd to say the least, or perhaps not so odd.

BP could and should have used “Riserless Drilling” techniques which they helped to develop in the South Caspian sea, where they also had serious blowout problems..This would have allowed better control of the formation fracture pressures and was used by BP in similarly hazardous geological conditions at West Azeri and elsewhere in the South Caspian after an earlier blowout and other problems. This is detailed in a separate post.

The belief in some quarters is that the US Govt. will await judge Carl Barbier’s 1st decision on “Gross Incompetence and Wilful Negligence” after Part 1 and then Part 2 will be all about how much BP pay up, based upon best estimates of oil which flowed. The attempted COREXIT clean up was a disgrace which compounded the original incompetence and this dreadful attempt to “disappear” oil thus reducing future fines is well covered elsewhere.

The truth will out. It is far too important not to be. But we are all just tiny individuals struggling to make sense of a hugely complex event, which is why some parties hope that the complexity and obfuscation can continue.

There is a least now a vast amount of Public Domain information on the subject, and there are a handful of people around who have now figured out what went on. Mr. Dan Zimmerman is the person who first warned of what may happen offshore California, but his work was not listened to in 2009. However obtaining critical documents has been akin to getting blood from a stone. For example, the rather prescriptive Macondo “Shallow Hazards Assessment” report was only made available as a Court Exhibit in April 2013 [TREX-07502], see http://www.oilspilldocs.com/exhibits.cfm?start=301

Based upon information received and the opinions of a very few independent specialists it is now quite convincing that in addition to the seven major drilling and completions errors, the root geological “geohazard” cause of the blowout was drilling into uncontrolled Gas Hydrates on the shelf edge area. These are frozen gas beds in the seafloor 100’s of metres thick and expand considerably when warmed/melted, or cause pressure build-up if constrained. The situation was compounded by the presence of 6 distinct  Shallow Water Flow [SWF] sand units mapped at well known intervals, the somewhat unusual placing of burst disks in the 16″ casing and some shorter casing strings than planned leading to the GH stability zone and sub-zone being exposed directly to the 16″ uncemented casing. This all has shades of the MARS/URSA drilling problems some years ago (1998-1999), which Shell are of course well aware of. There will be people in a number of oil companies who are well aware of what happened there and there are a few publications on the casing crimping and buckling that led to abandonment.

The melted frozen gas hydrate most likely blew through the lowest Burst Disk (essentially a valve) which was unprotected/uncemented and open to the sand layer, due to the 16″ casing being stopped early about 950 feet shallower than planned. After the pressure reduction in the well caused by the final negative leak off test, he gas blew up through the so-called outer annulus direct to the drill deck. It is unlikely this gas did not come from reservoir level at 18,000 feet. That high velocity gas plume siphoned the oil up through the inner drillstring from depth later on ( a few minutes) and off went the flow for 87 days. The main evidence provided to explain why the blowout flowpath was internal and not via the annulus was the lack of hydrocarbons identified in the annular fluids. However only gas entered the annulus. The oil flowed through the drillstring as erosion inspections of the wellhead showed.

Having the lowest burst disk in the centre of a thick permeable sand layer, unprotected from the outer strata by casing or cement and in a highly likely hydrate depth zone was a huge error, probably not realised by anyone onboard at the time in all the horrible confusion.

Image

If this is the case, and I think the evidence is fairly conclusive, then not only could deep drilling be stopped in GoM beyond a certain water depth, but also in deepwater regions around the world offshore West Africa and elsewhere. This in combination with the almost certain ban on exploration drilling of any sort in environmentally sensitive areas such as Alaska, the Antarctic Basin and elsewhere, will likely lead to a rocketing oil price in the coming years. BP has not come clean and there is possibly a degree of covering up going on. This does a disservice to the rest of the GoM oil industry and that secrecy will lead to problems for the other players when the truth actually does come out.

Bhopal and Exxon Valdez took years to come out and the same may be true here.

Why does it matter that the gas came from much shallower gas hydrate [GH] layers and not reservoir depth? Well, Alaska, amongst others, is a big hydrate area, which has been looked at for GH exploitation as an energy source, as has the Gulf of Mexico and other parts of the world. You can perhaps guess what might be going on here.

The description given on Page 5 of Peter Folger’s US Congressional Research Service document is almost certainly what happened at MC 252:

http://www.fas.org/sgp/crs/misc/RS22990.pdf

Guardian

http://www.guardian.co.uk/environment/2010/may/20/deepwater-methane-hydrates-bp-gulf

http://www.guardian.co.uk/environment/2010/may/26/bp-top-kill-mud-gulf-of-mexico-deepwater-horizon

Solve Climate

http://solveclimate.com/blog/20100524/investigator-warned-mms-2009-about-deepwater-gas-blowouts-gulf-mexico

Boing Boing

http://www.boingboing.net/2010/05/26/did-methane-hydrates.html

In These Times

http://www.inthesetimes.com/article/6067/bp_bets_the_planetwe_lose/

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About thegallowglaich

Offshore Engineer and Researcher
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