COLLAR AND
ENVIRONMENTAL CORRECTIONS
Even a perfectly calibrated probe will not give the right formation API values when run downhole. A good calibration is an important part of the puzzle, but cannot guarantee a good log by itself. One has to take into account the very complex environment in which the tool is run.
A number of different factors affect the tool response. One of the biggest and most obvious is the effect of the drill collar. Even half an inch of steel will absorb a significant fraction of the gamma rays. For this reason, drill collar correction curves are developed to correct for the effect of drill collars.
Several companies have developed these corrections, and they provide corrections that are in the ball park for a nominal collar. Minette Consulting’s corrections are unique in that they allow the customer to correct for non-standard drill collar weights.
But, the drill collar is only one of many factors affecting the response. In addition to the drill collar, there is the borehole environment. This includes
1) Mud Type and Weight
2) Borehole Size
3) Centering/Eccentering
4) Presence of Radioactive Potassium in the Mud.
5) Effect of Collar OD and ID on the mud response
After extensive efforts, Minette Consulting is now able to provide the most complete corrections in the industry, in accord with the most stringent specifications. As you can see, the range of borehole sizes mud densities, and types of muds meets or exceeds any correction algorithm that is provided by any service company.
Examples of the mud weight correction and mud radioactivity corrections give a picture of how the correction works.
These corrections are available through the Benchtree receiver software.