Saturday, March 30, 2013

Major Failure: A Graphic Example of the Risks of Modern Well Completion

by Bob Cavnar, this small planet, March 27, 2013

Last week, on March 18th, 2013, LeNorman Operating, based in Oklahoma City, was engaging in multiple well operations on their lease in Hemphill County, Texas.  Halliburton was on location, fracking their Ruth 87-2H well, a Granite Wash completion; simultaneously, Cased Hole Solutions, as reported by witnesses, was perforating another well with wireline nearby on the same drilling pad.  A note here:  One of the advances in drilling and completion technologies brought to land from offshore operations is the ability to directionally drill multiple wells from one location or “pad.”  The advantage is efficiency and smaller geographic footprint.  The disadvantage, among others, is the danger of multiple operations on a single location (i.e., see Deepwater Horizon blowout causes).

As reported by industry website, Drilling Ahead, Halliburton was pumping the frac job at a reported 8,500 p.s.i. (pounds per square inch) when the 7″ production casing parted about 100′ below ground level.  This sudden upward force also parted the surface pipe just below the casinghead, and the entire assembly, including the frack stack and the attached frac iron, became a giant bottle rocket, landing on the wireline truck.  Miraculously, no one was killed, and the only injury was the operator in the wireline truck, sustaining a concussion.  I was able to confirm the incident through the Texas Railroad Commission Blowouts and Well Control page.  Before I talk about the causes of an accident like this, I’ll note that since January 1, 2011, in Texas alone, there have been 67 reported blowouts and well control problems; remarkably, reported injuries in these incidents were only 4; there was one fatality.  Of these 67 incidents, 5 were related to casing failures during frack jobs.

The post accident photos published by Drilling Ahead and floating around the industry are impressive and can give the reader a sense of the extreme forces that oilfield tubulars and equipment sustain during drilling, completion, and production operations.  Here are a few of the pics:

IMG 1075 Major Failure: A Graphic Example of the Risks of Modern Well Completion Technologies
Side view of the frack stack lying on top of the destroyed wireline truck.

IMG 1117 Major Failure: A Graphic Example of the Risks of Modern Well Completion Technologies
This hole is where the wellhead was. They were extremely fortunate the well didn’t blow out.

IMG 1133 Major Failure: A Graphic Example of the Risks of Modern Well Completion Technologies
Clear view of the bottom of the casinghead, surface pipe and production pipe.

Catastrophic casing failures, while relatively rare, can have profound consequences.  You’ll recall that potential casing failure and loss of well integrity was one of the principal concerns during the blowout of the Macondo well in the Deepwater Gulf of Mexico in 2010.  If you lose integrity, you lose control, and the well is open to the world.  Luckily here, this well stayed dead after the frackstack blew off.  In many cases, that doesn’t happen and the well blows out with nothing on top to work with to regain control.

Casing failure has a several causes; manufacturing flaws, damage while handling, or improper setting are most common.  Most frack jobs are pumped directly down the casing, rather than using a small diameter tubing run inside.  Operators do this to get a higher pump rate, and/or lower injection pressures, allowing for larger frack jobs.  In order to do a casing frack, however, the casing has to be set or “hung off” in the casinghead by “stacking” weight below the slips.  Stacking weight below the slips essentially puts “slack” in the casing allowing for thermal contraction that occurs when you pump cold frack fluids into a warm well.  As steel contracts, tremendous forces are exerted on the pipe itself, as well as the pipe threads and couplings.  If enough slack is not put in the pipe, its rated tensile strength can be exceeded during thermal contraction, and it will part, as we saw in this case.  Worse yet, the upward force can also be exceeded on the protection casing around it, in this case, the surface pipe, and it can also fail.  When that happens you have a gigantic bottle rocket.

The concerns over hydraulic fracturing mostly focus on its effects on ground water.  Much of that concern comes from worries that frack fluids will reach ground water sands that have been penetrated by oil and gas wells, concerns which are dismissed by the industry who claims that surface casing and cement protects those sands.  I believe surface pipe and cement does protect ground water much of the time, but the procedure is not failsafe and the industry claim is certainly not true 100% of the time.  There are strict rules in most states, including Texas, that specify surface pipe depths, strength, cement quality and cement volume.  However, just like we saw after the Deepwater Horizon incident, those rules only work if they are followed and enforced.  What we are seeing in Texas, as well as other shale boom areas, is lots of activity on many locations, not enough inspectors, and many workers who may not be trained as well as they should.  Going fast with lots of operations and light oversight can result in catastrophic failures.  Here was one.

Hopefully we learn from it.

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