Near Bit Drill Collar

There are three types of drill collars, ordinary drill collars, spiral drill collars, and non-magnetic drill collars.

Ordinary drill collars are generally made of 4145H steel. Non-magnetic drill collars are made of non-magnetic materials and made of stainless steel. Therefore, non-magnetic drill collars are generally not painted. Spiral drill collars have spiral grooves throughout the body, which is very different in appearance from ordinary drill collars.

The drill collar is one of the important components of the drill string. Its function is to provide the drill bit with a bit pressure and at the same time make the lower drill tool assembly have greater rigidity, so that the drill bit is stable and helps to overcome the well inclination problem.

Drill collar classification:

Cylindrical type: drill collar made of ordinary alloy steel, the cross-section of the tube body is round inside and outside.

Features

(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 .

2. Spiral type: drill collar made of ordinary alloy steel with spiral groove on the outer surface of the tube. Can effectively reduce the occurrence of sticking stuck.

The drill collar is connected with the drill pipe on the top and the drill bit on the bottom. Its main role is to use its own weight to provide the bit pressure, to break the rock, to achieve drilling. In addition, due to the stiffness of the drill collar itself, the stabilizer is used to form a rigid drill string, which can prevent the lower drill string from bending during drilling and avoid the well inclination. The drill collars have rough female buttons at both ends. Some of them are female buttons at one end and male buttons at the other end. In order to eliminate stress concentration and avoid drill collar fatigue damage, a stress relief groove was designed on both ends of the drill collar near the joint wire. The API drill collar has an outer diameter of 7.6 ~ 30.5cm(3 ~ 12in), and its joint types are mostly internal flat type and full hole type, except some are normal type.

Non-magnetic type: It is made of non-magnetic stainless steel with very low magnetic permeability, such as non-magnetic stainless steel P550. The cross section of the tube body is round drill collars both inside and outside.

Non-magnetic drill collars have unusual design requirements, and as a result pose unique problems of corrosion resistance. Drill collars are the bottom components in a drill string, where their weight generates the force on the drill bit allowing it to drill and their stiffness allows the force to be transmitted without buckling. Conventional drill collars are made of alloy steel, like the rest of the drill string, and their corrosion usually poses no problems except to their threaded connections. A typical drill collar is 30 feet long and 4 to 9 inches in diameter.

We can customize different types of drill collars according to customer needs. Everyone is welcome to consult.