Spiral drill collar
In directional drilling, due to the large deviated well and the large contact area between the drill collar and the borehole wall, problems like sticking and jamming are more likely to happen. The spiral drill collar reduces the contact area between the drill collar and the borehole wall, so it is widely used. Spiral drill collars are not listed in intl standards, but due to its practical value, many manufacturers have produced them.
The function of the spiral drill collar is to reduce the occurrence of sticking and sticking. Three right-hand spiral grooves are machined on the outer cylinder of its circular drill collar. A 305-560mm section of the circular drill collar without grooves is reserved at the external thread joint and 475-610mm section of the internal thread end joint. Its weight is 4% less than that of the circular drill collar of the same size. Sanjack has rich experience in R & D, production and sales of spiral drill collars to all over the world for more than 20 years old.
Types and Structure
There are many kinds of spiral drill pipes manufactured by SanJack. Take the most commonly used BI and BII as examples.
BI type: This type of drill collar has three spiral grooves and is distributed in right-hand rotation. Outer diameter: 165.1mm ~ 177.8mm (6 1 / 2 ~ 7 inches); Cutting depth: 7.9 ± 1.59mm; Lead: 1168 ± 25.4 mm.
BII type: This type of drill collar has three spiral grooves, which are right-handed and evenly distributed. External contour curve equation:. Where: ρ— Pole diameter; θ— Polar angle; R – radius; E-coefficient. Outer diameter 171.5 mm (6 3 / 4 inch); The maximum cutting depth is 7.1mm; Lead 1000 ± 25.4 mm.
Country of Origin: China
Nominal OD: 4 3/4” (4.750”) to 9” 1/2” (8.500”)
Nominal ID: 2.250” to 3” (3.000”)
Material Grade: AISI 4145H Modified
Nominal Weight: 45.00# to 144#
Nominal Wall Thickness: 3.250”
Drift Size: 2.125” to 2.875”
Manufacturing Criteria: NS-1
Relevant tool joint Parameters
Connection: NC38, Regular, REG
Bend Stress Ratio: 1.920 to 3.061
OD: 4 3/4” (4.750”) to 9”1/2” (9.500”)
ID: 2.563” to 3” (3.000”)
1) Due to the structural features, spiral drill collars can provide weight for drilling purpose. Gravity works on a number of drill collars to offer enough downward force needed to break rocks with the drill bit.
2) Apart from providing weight on the bit (WOB), spiral drill collars also work as a shock absorber to dampen the vibration and shaking when drilling takes place. In this way, the drilling process can be carried out in a much steadier state.
3) The presence of the spiral drill collars allows the pipelines to stay in the tensile state, while guarantees the rigidity of the drill string under great compression. Thus, the drill efficiency and quality are greatly improved.
4) Spiral drill collars can help to control the direction of the bottom hole assembly, avoiding the problem of hole deviation and enhancing the performance of drilling.
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