Drill collar function is for heavy drill sting to give more weight on bit, But some reason we have to chose other type of drill colar. In this article we will sahare about special type of drill collar
There Are 3 Special Type of Dill Collar
- Anti-Wall Stick Drill Collar : When drilling through certain formations the large diameter drillcollars can become stuck against the borehole (differential sticking). This is likely to happen when the formation is highly porous, a large overbalance of mud pressure is being used and the well is highly deviated. One method of preventing this problem is to reduce the contact area of the collar against the wellbore. Spiral grooves can be cut into the surface of the collar to reduce its surface area see picture below sample of spiral drill collar.
- Square Drill Collar : These collars are usually 1/16” less than bit size, and are run to provide maximumstabilisation of the bottom hole assembly.
- Monel Drill collar : These collars are made of a special non-magnetic steel alloy. Their purpose is to isolate directional survey instruments from magnetic distortion due to the steel drillstring.
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