For want of a nail the shoe was lost.
For want of a shoe the horse was lost.
For want of a horse the rider was lost.
For want of a rider the battle was lost.
For want of a battle the kingdom was lost.
And all for the want of a horseshoe nail.
                                               -- Unknown


There is practically no field of endeavor that illustrates the truth of this proverb more than the drilling industry. From the smallest house well jobs, to the most technically challenging deep water oil wells, attention to detail has made the difference between success and failure.

On the largest end of the scale, it seems that investigation will prove that BP was lacking several horseshoe nails – small things, such as a questionable cement job, insufficient waiting-on-cement time, no cement bond log, a non-API inflow test, gas monitors and alarms turned off so the company man could sleep – many things, but mostly small things. Thousands of wells have been successfully drilled and completed this way with no problems. But when Murphy’s Law reared its head – Murphy had to be a driller – and one thing led to another, disaster ensued.

Recently, I was involved with a job with a small driller who was going into an area that was known to be tricky geologically, and a little deeper than he normally worked. The rig was in poor condition, but had been successfully drilling shallower wells in easier formations with only slightly more than the usual amount of field repairs. They were things like a parted drill line due to lack of lubrication and attention, a rotary clutch that had failed last year but had been patched just “to get through this job,” bad transfer-case bearings – small things, easily fixed, but overlooked.

Because they were pretty well behind schedule, shortcuts were taken. When they finally moved onto the big job, they were so late that more shortcuts were taken just to keep on schedule – small things like running a wing bit instead of a decent rock bit because it would drill the clay sections faster. Never mind that there were many layers of vugged limestone and dolomite. It was deemed faster to get in the hole if they didn’t run any stabilizers or drill collars to cut handling time, so the bit was screwed onto the end of a string of junk pipe. The result was a twist-off at 410 feet, leaving the bit and 30 feet of pipe in the hole.

Questionable fishing tools were hastily made – there were none on the rig – and run in the hole. Because the hole was drilled with an unstablized wing bit, it was crooked as a dog’s hind leg, and the fishing assembly wouldn’t go to bottom. The driller then decided to ream the hole with a rock bit to the top of the fish. More time was wasted until, finally, the rotary clutch broke again – another lost day and field repairs.

The next day, it was decided to abandon the hole, move the rig a few feet and start again. Since the surface casing was improperly set, it also was lost, adding to the expense. By the time new surface casing was delivered and set, another day was lost to small things, like running the rig out of fuel and fixing a backhoe hose that had been leaking for months. By this time, horseshoe nails were ankle deep on the location. Drilling eventually resumed, only to find out they were within 36 hours of a contract deadline that stated that they would be off the location and the location restored.

The original procedure was to set casing and screens, gravel pack, and tremie a cement plug on top of the gravel pack. This obviously was not possible, and the customer was not about to give an inch on the time. It was decided to drill to just above the producing formation, set casing and cement. This would allow them to move the rig, and come back without losing another hole. They would drill out, and set a liner and screens into the producing formation.

As time wore on, the mud got out of control, so I suggested they pump off and dilute it. No place to pump off. OK, thin it. No thinner. I went to town and got the thinner that should have been on the rig to start with, dug up more landscape to make a reserve pit, and got things going again.

We were within 60 feet of our casing point when the pinion bearings in the rotary table started to fail because the rotary clutch was in such bad shape, because the transfer-case bearings were going out. More horseshoe nails.

It was decided that we could set and cement casing at that depth, because we were deep enough to isolate the producing formation from the salt water above it.

Normally, I would recommend a bit trip to clean the hole, but with time pressing and the rotary table headed south, out we came. The driller did not bother to mention that he observed some swabbing as he came out. We went into the hole with the casing. Due to the condition of the hole, the casing started dragging 200 feet off bottom, and finally refused to go any more about 120 above the original intended depth. It was plugged, so a bit trip was made to clean it out enough to cement. I recalculated the cement, and we pumped. Since we had to move the rig, and I couldn’t leave it on the well, I calculated a balanced plug. I know; this will leave a long shoe-track, but it couldn’t be helped. Cement was pumped, the plug balanced, and the rig moved off at about dark-thirty. By this time, horseshoe nails were knee deep.

When, and if, the customer lets them get back on location, they should be able to finish the job if they spend the intervening time working on the rig – not with duct tape, but with real parts.

The point: In every operation, there are shortcuts, as well as time-saving methods. Sometimes we get by with them, and sometimes we don’t. I’ve met many drillers at trade shows who brag that they can drill circles around us old-timers, but they don’t bother to mention how many times they had to go back and re-drill some record-setting well. I’d rather have a driller who drilled 100 wells with no go-backs, than a kid who set the world on fire and re-drilled three out of five of those record wells. And this applies to Podunk Drilling as well a BP. 
ND