There are different kinds of drill collars,including round drill collar,spiral drill collar,non-magnetic drill collar,square drill collar and so on.Ordinary drill collar is the circular cross section, the center has a water hole,the wall thickness is larger,the nozzle is smaller, the weight of per unit length is greater than the size of drill pipe almost 4- 5 times .The majority of drill collar is thread processing directly on the pipe body , but some of them also use the replaced joint.
(1)Eccentric-weight drill collar is an effective anti-deviation drilling tool,with high drill pressure used in oblique areas,rectifying oblique as well.
(2)When drilling directional wells eccentric-weight drill collar is an effective tool to reduce oblique or straighten the well hole using high drilling pressure.
(3)Eccentric-weight drill collar has the advantages of simple structure,convenient use,connected directly to common drill collar without centralizers,greatly convenient for sinking in,fishing and milling operations.
(4)Eccentric-weight drill collar runs downhole safely,danger of leakage or bit freezing hard to appear.
(5)Pay much attention to avoid mud balling and prevent effect of anti-deviation .
CHEMICAL COMPOSITION
Drill Collar Specification | ||||||||
Thread Type | O.D. | I.D. | Length | Diameter of shoulder guide Angle | Reference bending strength ratio | |||
mm | inch | mm | inch | mm | inch | |||
NC23-31 | 79.4 | 31/8 | 31.8 | 11/4 | 9150 | 30ft | 76.2 | 2.57:1 |
NC26-35(23/8IF) | 88.9 | 31/2 | 38.1 | 11/2 | 82.9 | 2.42:1 | ||
NC31-41(27/8IF) | 104.8 | 41/8 | 50.8 | 2 | 100.4 | 2.43:1 | ||
NC35-47 | 120.7 | 43/4 | 50.8 | 2 | 114.7 | 2.58:1 | ||
NC38-50(31/2IF) | 127 | 5 | 57.2 | 21/4 | 121 | 2.38:1 | ||
NC44-60 | ||||||||
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