Shangshanpetro Technical Data Hub · Drill String
We manufacture drill collars across a published 3-1/8 in to 11 in OD range. Use this page to compare common dimensions, theoretical plain-body weight and connection references, then send the complete BHA requirement for drawing review and quotation.
Quick Answer
What is a complete drill collar size?
A drill collar size is not OD alone. A usable specification includes outside diameter, bore/ID, length, body profile, connection designation and pin/box orientation. Linear weight depends mainly on OD and ID, but finished weight also changes with spiral grooves, recesses, end geometry and machining. Final dimensions and connections must be confirmed against the BHA and approved drawing.
Core Reference Table
Drill Collar Size and Weight Chart
The chart covers common reference configurations within our published manufacturing range. Values in the weight columns are calculated for a plain 4145H steel cylinder before connection, recess or spiral-profile corrections.
| OD | OD mm | Bore / ID | ID mm | Theoretical lb/ft | Theoretical kg/m | Typical Length | Connection Reference |
|---|---|---|---|---|---|---|---|
| 3-1/8 in | 79.4 | 1-1/4 in | 31.8 | 21.9 | 32.6 | 30 / 31 ft | NC23 / compatible connection |
| 3-1/2 in | 88.9 | 1-1/2 in | 38.1 | 26.7 | 39.8 | 30 / 31 ft | NC26 / 2-3/8 IF reference |
| 4-1/8 in | 104.8 | 2 in | 50.8 | 34.8 | 51.8 | 30 / 31 ft | NC31 / compatible IF |
| 4-3/4 in | 120.7 | 2-1/4 in | 57.2 | 46.8 | 69.6 | 30 / 31 ft | NC38 / 3-1/2 IF reference |
| 5 in | 127.0 | 2-1/4 in | 57.2 | 53.3 | 79.3 | 30 / 31 ft | NC38 / project connection |
| 6 in | 152.4 | 2-1/4 in | 57.2 | 82.7 | 123.0 | 30 / 31 ft | NC44 / NC46 reference |
| 6-1/4 in | 158.8 | 2-1/4 in | 57.2 | 90.8 | 135.1 | 30 / 31 ft | Match to BHA requirement |
| 6-1/2 in | 165.1 | 2-13/16 in | 71.4 | 91.8 | 136.5 | 30 / 31 ft | NC46 / 4 IF / 4-1/2 REG reference |
| 7 in | 177.8 | 2-13/16 in | 71.4 | 109.8 | 163.4 | 30 / 31 ft | NC50 / 4-1/2 IF reference |
| 8 in | 203.2 | 2-13/16 in | 71.4 | 149.9 | 223.0 | 30 / 31 ft | 6-5/8 REG reference |
| 9 in | 228.6 | 3 in | 76.2 | 192.4 | 286.3 | 30 / 31 ft | 7-5/8 REG reference |
| 9-1/2 in | 241.3 | 3 in | 76.2 | 217.1 | 323.1 | 30 / 31 ft | 7-5/8 REG reference |
| 11 in | 279.4 | 3 in | 76.2 | 299.3 | 445.4 | 30 / 31 ft | Project / compatible API connection |
Shangshanpetro Drill Collar Manufacturing Capability
| Specification | Published / Available Scope | What We Confirm Before Production |
|---|---|---|
| Outside diameter | 3-1/8 in to 11 in | Exact OD, tolerance, hole clearance and handling envelope |
| Bore / ID | Standard or customized | Bore, drift, hydraulics and remaining section |
| Length | 30 ft / 31 ft reference; project options | Overall length, tolerance and quantity distribution |
| Material | 4145H modified alloy steel | Chemistry, heat treatment, hardness and documentation |
| Body profile | Slick or spiral | Groove geometry, remaining section, recesses and weight |
| Connection | API REG, IF or FH in compatible configurations | Exact designation, pin/box, bore, shoulder and gauging basis |
| Custom drawing | Supported, subject to engineering review | Manufacturability, inspection scope and acceptance criteria |
| Quality documentation | Material, dimensional, thread and agreed NDT records | PO requirements, witness points and third-party inspection |
How Much Does a Drill Collar Weigh?
For a plain steel body, approximate linear weight can be estimated from cross-sectional steel area:
Weight (lb/ft) ≈ 2.672 × [OD² − ID²]
Use OD and ID in inches. Convert lb/ft to kg/m by multiplying by approximately 1.488. This calculation does not include material removed or added by connections, spiral grooves, stress-relief features, slip/elevator recesses or other profile machining.
6-1/2 in OD: how bore changes theoretical weight
| OD | Bore / ID | Theoretical lb/ft | Theoretical kg/m | Effect |
|---|---|---|---|---|
| 6-1/2 in | 2-1/4 in | 99.4 | 147.9 | More steel area; smaller flow passage |
| 6-1/2 in | 2-13/16 in | 91.8 | 136.5 | Common reference configuration |
| 6-1/2 in | 3-1/4 in | 84.7 | 126.0 | Less steel area; larger flow passage |
What Dimensions Define a Drill Collar?
Outside Diameter
Controls envelope, stiffness, annular clearance and wall-contact area.
Bore / ID
Changes steel area, linear weight, flow passage and pressure loss.
Length
Affects joint weight, total collar-section length, handling and BHA layout.
Connection
Defines the rotary shoulder interface and must match adjacent tools.
Body Profile
Slick, spiral, recesses and special machining change contact and mass.
End Details
Pin/box orientation, bevel, shoulder, bore and relief geometry complete the drawing.
Drill Collar Connection Reference
NC, REG, IF and FH are connection families, not interchangeable shortcuts. We confirm the exact connection after reviewing the collar section and mating BHA components.
Full connection name and governing drawing or specification.
Pin/box arrangement and crossover requirements.
Shoulder, bevel, bore, counterbore and remaining section.
Make-up requirements, combined loads and inspection criteria.
How to Select Drill Collar Size
Define required WOB, stiffness, directional response, stabilization and neutral-point strategy.
Check hole size, restrictions, inclination, dogleg severity, formation and fluid system.
Evaluate stiffness, clearance, fishing, unit mass, hydraulics and pressure loss together.
Compare slick and spiral geometry for contact, flow paths, remaining section and weight.
Verify designation, orientation, mating tools, bore and make-up requirements.
Freeze material, dimensions, tolerances, inspection, marking and document scope before production.
Air Weight vs Effective Weight on Bit
The chart reports theoretical linear weight in air. A submerged collar experiences buoyancy, and not all available submerged weight becomes effective WOB. Inclination, friction, stabilizer contact, bending, buckling, vibration and operating practice affect load transfer.
Preliminary relationship: buoyed collar weight ≈ air weight × buoyancy factor. The mud-density-based buoyancy factor and effective WOB must be established in the drilling and BHA model. Do not select the number of collars by air weight alone.
Slick vs Spiral vs Non-Magnetic Drill Collars
| Type | Key Characteristic | Selection Focus |
|---|---|---|
| Slick | Smooth external body and full nominal plain section | Clearance, contact, stiffness and required linear weight |
| Spiral | Helical grooves reduce continuous wall-contact area and remove material | Groove geometry, flow paths, remaining section and corrected weight |
| Non-Magnetic | Separate low-magnetic-permeability material category for survey environments | Alloy, magnetic properties, mechanical requirements and inspection |
Standard 4145H modified alloy steel is magnetic and is not a substitute for a non-magnetic collar. For profile selection, read Spiral Drill Collar vs Slick Drill Collar.
Need a Size or Connection Not Listed?
Send OD, bore, length, profile, connection, pin/box orientation, quantity and service conditions. We will review the configuration against manufacturing scope and prepare a quotation around the approved requirement.
Factory RFQ Example
Incomplete
“Please quote 6-1/2 in drill collars.”
Quotation-ready
6-1/2 in OD × 2-13/16 in bore × 31 ft, slick 4145H modified drill collar, specified connection and pin/box arrangement, quantity 20, inspection/document requirements, destination and required delivery date. Approved BHA drawing attached.
Also state applicable specification edition, material/hardness requirements, sour or special service, tolerances, NDT, third-party witness points, marking, packing and Incoterm where required.
Drill Collar Size & Weight FAQs
What are common drill collar sizes?
Shangshanpetro’s published OD range is 3-1/8 in to 11 in. A complete size must also state bore, length, profile and connection; OD alone is not an ordering specification.
How much does a drill collar weigh per foot?
For a plain steel body, approximate lb/ft is 2.672 × (OD² − ID²), with diameters in inches. Finished unit weight must be calculated from the approved geometry.
Why can two collars with the same OD have different weights?
Their bores, lengths, spiral grooves, recesses, connections, tolerances or materials may differ. A larger bore or deeper groove removes steel and reduces weight.
Is the connection fixed by drill collar OD?
No. OD narrows the feasible range, but bore, section strength, mating BHA components, pin/box arrangement, torque requirements and approved geometry determine the final connection.
What lengths are commonly supplied?
Our published reference lengths are 30 ft and 31 ft, with project options subject to drawing and manufacturing review.
Does a heavier collar always provide better drilling performance?
No. WOB transfer also depends on buoyancy, inclination, friction, buckling, vibration, stabilizer placement, hydraulics and operating limits. The complete BHA must be modeled.
When is a non-magnetic drill collar required?
It is specified where magnetic survey, MWD or LWD tools require a controlled magnetic environment. It is a separate material and inspection category, not standard 4145H.
What information is needed for a drill collar quote?
Provide OD, bore, length, body profile, exact connection and orientation, material and service conditions, inspection scope, quantity, destination and delivery target. Include the approved BHA or component drawing when available.
Related Resources
Published supply scope, manufacturing and quality information.
Spiral vs Slick Drill Collars
Profile differences, application factors and RFQ details.
Drill Pipe vs HWDP vs Drill Collar
Compare roles, construction, stiffness and buying data.
Heavy Weight Drill Pipe
Review the transition component used above the collar section.
Request a Drill Collar Technical Quotation
Send the required OD, bore, length, profile, connection, quantity, service conditions and inspection scope. We will review the configuration and quote against the agreed drawing and purchase requirements.
