Drill Collars

The drill collars are made from modified AISI 4145H chromium molybdenum alloy steel. These drill collars are heat treated over its full length and further water quenched to obtain the mechanical properties in accordance with ASTM A-370. Mechanical and chemical properties of the steel are recorded in the relevant Mill Test Certificates and these are supplied with all drill collars. The Mill Test Certificates guarantee a hardness value in the range of 285 to 341 BHN and an IZOD impact value of 40 ft-lbs. at room temperature at one inch below the surface.
Drill Collars Oil Tools

STANDARD FEATURES:

Surface Finish:
The surface finish can be either “as rolled”, mill finish, peeled, or as per machined finish. The straightness, roundness and OD tolerances conform to API specifications.

Bores:
All drill collars are trepanned or deep precision bored along the bar length to tight tolerances that eliminate wall thickness variation. All trepanned drill collar bars are drifted to API specifications.

Lengths:
Most commonly API Range 2 drill collars are manufactured at OTI. However, we have the capability to manufacture API Range 3 drill collars as well both with the standard features listed here and the special features mentioned below.

Threaded Connections:
All threaded connections are precision machined to API specifications. Further all threaded connections are applied with phosphate surface coating to minimize galling during makeup and stored after the application of thread compound that conforms to the requirements of API RP 7A1.

Thread Protectors:
Cast or Pressed Steel Thread Protectors are installed on all drill collars that OTI manufactures. This is to provide maximum protection to threaded connections from damages during handling & storage and also give complete protection from corrosion.

Quality Assurance and Quality Control:
An extensive quality assurance program is employed at OTI that establishes various control points to ensure quality assurance and quality control ideologies are achieved right from purchase of the raw material to every relevant manufacturing step. OTI’s inspection team is equipped with state of the art monitoring and measurement tools that ensure that the highest level of inspection is achieved during all stages of production. OTI’s qualified inspectors can conduct various validated NDE methods that includes MPI, UT and PT inspection techniques.

Identification / Markings:
OTI is licensed by API and can apply the API monogram on all drill collars that meet with API’s Monogramming requirements. OTI can also machine identification slots as per the requirements of customers.

ORDERING INSTRUCTIONS:

When ordering or requesting quotations for drill collars, please specify the following :

  1. Collar Outside Diameter (OD).
  2. Drill Collar Bore (ID)
  3. Length of Drill Collar
  4. Size, type and location of connections,Eg: NC 50 BOX Up x NC 50 PIN Down
  5. Slick or Spiral
  6. Cast or Pressed Steel Thread Protectors
  7. Special Optional Features as desired – slip and / elevator recesses and / hardband type.
STANDARD SIZES, BORES AND CONNECTIONS FOR DRILL COLLARS

STANDARD SIZES, BORES AND CONNECTIONS FOR DRILL COLLARS

Size OD

Bore

Connection Style and Size

Approx. Weight,
31 ft.

Standard

Optional

For Standard Bore

For Optional Bore

(In.)

(In.)

(In.)

NC

API

NC

API

(Lbs.)

3-1/8

1-1/4

1

NC 23

 

 

2-3/8 REG

660

3-1/2

1-1/2

1-1/4

NC 26

2-3/8 IF

NC 26

2-3/8 IF

801

4-1/8

2

1-3/4

NC 31

2-7/8 IF

NC 31

2-7/8 IF

1043

4-3/4

2-1/4

2

NC 38

3-1/2 IF

NC 38

3-1/2 IF

1451

5

2-1/4

2

NC 38

3-1/2 IF

NC 38

3-1/2 IF

1652

6

2-1/4

2-13/16

NC 44

 

NC 40

4 FH

2561

6-1/4

2-1/4

2-13/16

NC 46

4 IF

NC 46

4 IF

2806

6-1/2

2-1/4

2-13/16

NC 46

4 IF

NC 50

4-1/2 IF

3085

6-3/4

2-1/4

2-13/16

NC 46

4 IF

NC 50

4-1/2 IF

3364

7

2-13/16

2-1/4

NC 50

4-1/2 IF

NC 50

4-1/2 IF

3643

7-1/4

2-13/16

3

NC 50

4-1/2 REG

 

5-1/2 FH

3714

7-3/4

2-13/16

3

NC 56

6-5/8 REG

NC 56

6-5/8 REG

4337

8

2-13/16

3

NC 56

6-5/8 REG

NC 56

6-5/8 REG

4675

8-1/4

2-13/16

3

 

6-5/8 REG

 

6-5/8 REG

5016

8-1/2

2-13/16

3

 

6-5/8 REG

 

6-5/8 REG

5337

9

3

2-13/16

NC 61

6-5/8 REG

NC 61

7-5/8 REG

6070

9-1/2

3

2-13/16

 

7-5/8 REG

 

7-5/8 REG

6727

10

3

2-13/16

NC 70

8-5/8 REG

NC 70

8-5/8 REG

7532

11

3

2-13/16

NC 77

8-5/8 REG

NC 77

8-5/8 REG

9269

Note: All dimensions are in inches unless stated otherwise

SPIRAL DRILL COLLARS: Spiral Drill Collars are manufactured by milling spiral grooves on the bar to prevent the likelihood of differential wall-sticking by reducing the wall contact between the drill collar and the wall of the hole. Shown below is the illustration of the drill collar cross-section highlighting the reduced contacted area as a result of spiral groove milling


SPIRAL GROOVED DRILL COLLAR SPECIFICATION

OD Size

No: of Spirals

No: of Cuts in Spiral

Direction of Spiral

Spiral Pitch

Depth of Cut

A

B

THRU 3-7/8

3

3

Right Hand

36 ± 1

5/32 ± 1/32

 

4 – 4-3/8

3

3

Right Hand

36 ± 1

3/16 ± 1/32

 

4-1/2 – 5-1/8

3

3

Right Hand

38 ± 1

7/32 ± 1/32

 

5-1/4 – 5-3/4

3

3

Right Hand

42 ± 1

1/4 ± 1/32

 

5-7/8 – 6-3/8

3

3

Right Hand

42 ± 1

9/32 ± 1/16

 

6-1/2 – 6-7/8

3

3

Right Hand

46 ± 1

5/16 ± 1/16

 

7

3

3

Right Hand

64 ± 1

5/16 ± 1/16

 

7-1/8 – 7-1/4

3

9

Right Hand

64 ± 1

7/32 ± 1/16

1/4 ± 1/16

7-3/8 – 7-5/8

3

9

Right Hand

64 ± 1

15/64 ± 1/16

1/4 ± 1/16

7-3/4 – 7-7/8

3

9

Right Hand

64 ± 1

1/4 ± 1/16

1/4 ± 1/16

8 – 8-5/8

3

9

Right Hand

68 ± 1

1/4 ± 1/16

1/4 ± 1/16

8-3/4 – 8-7/8

3

9

Right Hand

68 ± 1

9/32 ± 1/16

1/4 ± 1/16

9 – 9-1/4

3

9

Right Hand

72 ± 1

9/32 ± 3/32

17/64 ± 3/32

9-3/8 – 9-5/8

3

9

Right Hand

72 ± 1

19/64 ± 3/32

17/64 ± 3/32

9-3/4 – 9-7/8

3

9

Right Hand

72 ± 1

5/16 ± 3/32

1/4 ± 3/32

10 – 10-1/4

3

9

Right Hand

76 ± 1

5/16 ± 3/32

9/32 ± 3/32

10-3/8 – 10-1/2

3

9

Right Hand

76 ± 1

21/64 ± 3/32

9/32 ± 3/32

10-5/8

3

9

Right Hand

76 ± 1

21/64 ± 3/32

1/4 ± 3/32

10-3/4 – 10-7/8

3

9

Right Hand

76 ± 1

11/32 ± 3/32

1/4 ± 3/32

11 – 12

3

9

Right Hand

80 ± 1

21/64 ± 3/32

21/64 ± 3/32

Note: All dimensions are in inches unless stated otherwise

Please note that the weight of a Spiral Drill Collar is approximately 4% less than that of a Slick Drill Collar of the same size

SPECIAL OPTIONAL FEATURES

Slip and Elevator Recesses: Slip and Elevator Recesses are machined to eliminate the usage of lift subs and safety clamps, thus reducing the drill collar handling time. Customers can choose if they need the Slip and Elevator recesses together or separately. When machining slip and or elevator recesses, extreme care is taken that smooth radii are obtained and that there is no presence of tool marks on the surface. Customers have the option to increase fatigue life by opting to have the radii at the upper shoulders cold rolled. Further information on Slip and Elevator recesses can be provided upon request.


Stress Relief Features: API Stress Relief Features like Relief Groove on Pin Connections and Bore Back on Box Connections are recommended for drill collars and all downhole drilling tools where cyclic fatigue may occur from bending. The application of Stress Relief Features provides a more flexible connection that is less likely to crack due to fatigue as bending occurs in areas of smooth surfaces that are free of stress concentrations. The API Pin Relief Groove and Box Bore Back remove unengaged threads in highly stressed areas of the drill collar connection.


Cold Rolled Thread Roots: Cold Rolling of Thread Roots is the method of pre-stressing the thread roots of drill collar connections by cold working. All cold rolled thread roots have greater resistance to fatigue failure, as after cold rolling, the thread roots remain in compression. By employing cold rolling of thread roots, a drill collar’s connection life can be improved as cold rolled thread roots can withstand bending stresses longer without cracking in fatigue.


Hardbanding: : An automatic, metal-arc, inert gas shielded, consumable electrode process is used with closely controlled preheat and postheat. Hardbanding material consists of granular tungsten carbide that is fed automatically into the molten weld puddle to obtain uniform distribution of the tungsten carbide particles. The resulting deposit of hardbanding is flush to 1/32” above the OD of the collar.

Please note that the smallest diameter that can be hardbanded is 4-3/4” OD. This is because any drill collar that is lower than 4-3/4” OD would have smaller wall thickness. Information on OTI’s Hardbanding material can be found on the appropriate data sheet