Drilling on the cheap

“..BP threw a lot of money away by trying to drill that well ‘on the cheap’. One now has to wonder how Shell plans to drill their wells in the Arctic given the very ‘cheap’ drilling rig they are using.”

COMMENT ON THE BP/TRAN OCEAN DISASTER BY A FORMER SHELL EMPLOYEE

I have worked in the oil industry for several decades and have worked on many dozens of exploration wells, domestic US and overseas. Shallow wells, deep wells, straight hole and deviated, normally pressured and geopressured. So, I have been there and done that.

I have noticed in many articles and commentaries that Halliburton has come in for some serious pummeling for the design of the cement job for that particular well. Questions have been raised about whether they used the appropriate type of cement, and whether the proper number of stabilizers were attached to the casing, etc. And then there has been mention of the fact that BP did not run a cement bond log afterwards to determine the quality of the cement job.

I have however, seen no mention what-so-ever of the condition of the uncased borehole prior to the running of the casing and the cementing of that casing. It may well have been that the condition of the borehole was so bad that it was not possible to get a reliable cement job on the casing.

By ‘bad borehole’ I mean that it was badly washed out. Instead of being a nice round hole in the ground it was a very ratty and ragged affair where the diameter of the borehole varied widely up and down the open hole section. A ragged, ratty, washed out borehole almost always precludes obtaining a good cement job.

What causes borehole washout problems? Some times they are related to the type of rock through which you are drilling, such as unconsolidated shales or salt. But most of the time they are related to the way the well was drilled. The longer a borehole is open the rattier it gets. A poor mud program, designed to cut drilling expenses, is often the culprit.

In most large oil companies engineering duties for exploration and production wells are split into various sub-specialties. There are drilling engineers who specialized in designing drilling programs for well, there are production or completion engineers who take over from the drilling engineers after a well has been cased and cemented. And there are evaluation engineers who specialized in evaluation the various rock formations that a well has penetrated to determine if hydrocarbons are present or not.

The objective of the drilling engineers and drilling operations folks are often very much at odds with what is needed and required by the evaluation and completion engineers. Drilling engineers want to punch a hole down to the objective as quickly and cheaply as possible. Evaluation and completion issues associated with poor borehole conditions are not their problems. Evaluation and completion engineers want a borehole that is in as good condition as possible, i.e., that is not washed out. These people are always at odds with each other over how a well is to be drilled, and the resulting drilling program is always a compromise.

If engineering management and leadership is good then the drilling program is designed to meet the needs of the evaluation and completion engineers for an exploration well. If it is not, and they are too focused on ‘saving money’, then the resulting well will often be in poor condition making evaluation difficult at best, and in some cases impossible. Completing a well with a bad borehole can be very challenging as well, particularly if there are multiple zones to test. If the well bore is in bad condition the cement job is usually ineffective and it is not possible to isolate productive zones because the hydrocarbons can flow between the casing and the borehole.

From what little I have read and heard about the BP incident it would appear that no matter what Halliburton may or may not have done, it may not have been possible to get a good cement job on that well. That would allow hydrocarbons to migrate upward between the casing and the well bore.

While Transocean was responsible for drilling the well and rig operations, BP was responsible for the design of the drilling, evaluation, and completion program, and the execution of those programs.

From what little information I have seen I suspect the real culprit behind the BP fiasco was poor well design, and a poorly designed drilling program designed to save as much money as possible. That coupled with all the other mistakes, then led to the disaster. At $500,000/day, or there abouts, that drilling rig was not cheap. But BP threw a lot of money away by trying to drill that well ‘on the cheap’.

One now has to wonder how Shell plans to drill their wells in the Arctic given the very ‘cheap’ drilling rig they are using.

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