Description
API Oilfield Drill Collars for Weight on Bit and BHA Stability
Shangshanpetro manufactures and supplies 4145H oilfield drill collars for bottom-hole assemblies where concentrated weight, stiffness and stable load transfer to the bit are required.
Each quotation is configured around outside diameter, bore, length, slick or spiral profile, connection, material documentation, inspection scope and drilling conditions.
Supply Overview
Quick answer: A drill collar is a heavy, thick-wall rotary drill-stem element installed in the lower BHA. It supplies weight on bit (WOB), adds stiffness near the bit and helps the assembly maintain a controlled drilling direction. OD, bore and length determine its weight; the exact configuration must therefore be confirmed before pricing or load calculations.
What Does a Drill Collar Do?
The drill collar section is selected as part of the complete BHA, not as an isolated heavy tube. Its dimensions and placement influence weight distribution, bending behavior, hydraulics, contact and directional response.
01
Provides Weight on Bit
High linear mass allows controlled compressive load to be transferred to the bit while the drill pipe above is managed under tension.
02
Adds BHA Stiffness
The thick-wall section resists bending more than standard drill pipe and supports the planned bottom-hole assembly behavior.
03
Stabilizes Drilling
When combined with stabilizers and other BHA tools, collars help manage bit loading and directional tendency.
04
Transmits Torque
Rotary-shouldered connections and the collar body carry torque and axial loads through the lower drill string.
05
Maintains Fluid Passage
The internal bore provides a drilling-fluid path; bore size must balance hydraulics with required section mass and strength.
06
Supports BHA Design
Collar OD, ID, length, profile and placement are coordinated with hole clearance, dogleg severity and load cases.
API Drill Collar Specifications
The values below reflect the currently published Shangshanpetro supply range. Final dimensions, tolerances, connection data, testing and marking must follow the approved data sheet and purchase specification.
| Specification item | Published / available scope | What the buyer should confirm |
|---|---|---|
| Standard basis | API Spec 7-1 as specified | Applicable edition, addenda, product requirements and document scope. |
| Material | 4145H modified alloy steel | Material specification, chemistry, heat treatment, mechanical testing and traceability. |
| Outside diameter | 3-1/8 in to 11 in; customizable within manufacturing scope | Exact OD, hole size, radial clearance and handling constraints. |
| Inside diameter / bore | Selected for required geometry and fluid passage | Exact bore, drift requirement, section area and hydraulic calculation. |
| Length | 30 ft or 31 ft; customizable by project | Overall length, tolerance, quantity and permitted length distribution. |
| Profile | Slick or spiral configuration, subject to quotation | Spiral geometry, remaining section, flow clearance and wear allowance. |
| Connections | API Reg, IF or FH in compatible configurations | Exact designation, pin/box orientation, bore, make-up torque and gauging basis. |
| Hardness | 285-341 HB on the existing product specification | Test method, sampling, acceptance range and report requirements. |
| Straightness | At or below 1/1000 on the existing product specification | Measurement method, datum, acceptance and reporting. |
| Surface protection | Phosphating and/or anti-corrosion protection | Thread treatment, body coating, storage period and shipping environment. |
| Inspection | Material, dimensional, thread and NDT scope as agreed | Procedures, acceptance criteria, witness points and third-party inspection. |
A nominal OD is not a complete drill collar specification. Weight and mechanical behavior also depend on bore, length, profile, connection details and material condition.
Slick, Spiral and Non-Magnetic Drill Collars
Slick Drill Collar
A smooth outside profile provides the full nominal section and conventional geometry. Check annular clearance, wall-contact risk and BHA placement for the planned hole.
Spiral Drill Collar
Spiral grooves reduce continuous wall-contact area and create flow paths around the body. Groove depth, pitch, remaining section and weight must be approved.
Non-Magnetic Collar
This is a separate material category used around magnetic survey instruments. Standard 4145H alloy steel is magnetic and must not be treated as a substitute.
Supply clarification: the published Shangshanpetro specification identifies 4145H modified alloy steel. If a non-magnetic drill collar is required, request it as a separate engineered product and confirm alloy, magnetic properties, mechanical requirements and inspection documents before order.
Drill collar dimensions and connections are confirmed on the approved product drawing.
Geometry Buyers Should Identify
The quotation drawing should define the complete load-carrying section and every interface. This is especially important when a buyer is comparing drill collar sizes or calculating collar weight.
Drill Collar Sizes and Weight
Drill collar weight is calculated from the net steel volume and material density, including the OD, bore, length, connection geometry and any spiral grooves or other machined features. Two collars with the same OD can therefore have different weights.
For a reliable weight figure: provide OD, bore, overall length, connection and slick or spiral profile. Shangshanpetro can return the unit weight and total shipment weight on the approved quotation data sheet. Do not use a generic web table as the final lifting, transport or BHA-design value.
| Input | Why it changes the result | Buyer action |
|---|---|---|
| Outside diameter | Larger OD increases section area, stiffness, unit mass and hole-clearance requirements. | Match OD to hole size and BHA model. |
| Bore / ID | A larger bore reduces steel area and weight while changing hydraulic passage and section properties. | Define bore and drift requirements. |
| Length | Unit weight scales with effective material length and affects total BHA weight. | State 30 ft, 31 ft or exact project length. |
| Slick or spiral | Spiral machining removes material and changes external contact and flow behavior. | Approve a dimensioned profile. |
| Connection geometry | Pin, box, bore and relief details alter end-section volume and stress distribution. | Confirm the exact connection designation and drawing. |
Connection Selection
API Reg, IF and FH are connection families, not interchangeable labels. Availability and compatibility depend on collar OD, bore, surrounding BHA components and the specified rotary-shouldered connection requirements.
A
Exact Designation
Specify the full connection name, pin and box arrangement and any reference drawing or customer standard.
B
Dimensional Compatibility
Review shoulder, bevel, connection bore, counterbore and surrounding tool dimensions.
C
Torque and Loads
Confirm make-up torque and anticipated tension, compression, torque and bending load cases.
D
Thread Inspection
Define gauges, surface treatment, acceptance criteria and documentation before manufacture.
E
Field Handling
Use clean threads, approved compound, correct handling tools and protected shoulders during transport.
F
Traceability
Keep connection inspection and product identification linked to the material heat and manufacturing records.
Drill Collar vs HWDP vs Drill Pipe
These products form a connected drill-string cluster, but each has a different stiffness, mass distribution and role. They should be selected together in the drill-string and BHA model.
| Component | Construction and behavior | Primary role | Main buying focus |
|---|---|---|---|
| Drill pipe | Relatively thin-wall pipe body with tool joints | Forms most of the string and transmits fluid, torque and axial loads. | Size, nominal weight, grade, upset, connection and inspection. |
| Heavy weight drill pipe | Thicker body with extended end sections and normally a center upset | Adds weight and creates a stiffness transition above the collar section. | Body geometry, integral/welded route, connection, wear and fatigue transition. |
| Drill collar | Very thick and stiff alloy-steel rotary drill-stem element | Provides WOB and stiffness close to the bit. | OD, bore, length, slick/spiral form, material, connection and BHA plan. |
How to Select a Drill Collar
Manufacturing and Quality Control
Agree the acceptance criteria and document package before production. The final scope may include customer or third-party witness points when stated in the inquiry.
A
Material Traceability
Heat identification and material documents are linked to the collar marking and manufacturing records.
B
Heat Treatment
Process controls and mechanical tests verify the agreed material and hardness requirements.
C
Dimensional Control
OD, bore, length, straightness, profile and end geometry are checked against the approved drawing.
D
Nondestructive Testing
Applicable examinations are performed to the specified procedure and agreed acceptance criteria.
E
Thread Inspection
Connection dimensions, gauges, shoulders and surface condition are inspected within the agreed scope.
F
Protection and Packing
Thread protectors, corrosion protection, bundling and shipping marks prepare collars for export transport.
Information Required for a Drill Collar Quotation
Send the following information to receive a usable technical and commercial quotation:
Related Drill-String Products and Guide
Drill Collar FAQs
What is a drill collar?
A drill collar is a heavy, thick-wall rotary drill-stem element used in the bottom-hole assembly. Its mass and stiffness help apply weight on bit and stabilize the lower assembly.
What is a drill collar used for?
It supplies controlled WOB, adds stiffness near the bit, transmits torque and axial loads and works with stabilizers and other BHA tools to manage drilling behavior.
What sizes of drill collars are available?
Shangshanpetro currently lists drill collar ODs from 3-1/8 to 11 inches, with 30 ft and 31 ft lengths plus project customization. Exact bore, profile, connection and tolerances are confirmed for the selected configuration.
What material is used for standard drill collars?
The published Shangshanpetro range identifies 4145H modified alloy steel. Material chemistry, heat treatment, mechanical properties, hardness and documentation should be stated in the purchase specification.
What is the difference between a slick and spiral drill collar?
A slick collar has a smooth outside profile. A spiral collar has machined helical grooves that reduce continuous wall-contact area and create external flow paths, while also removing some material and weight.
How is drill collar weight calculated?
Weight depends on net steel volume: OD, bore, length, connection geometry and any spiral grooves or other machined features. Request the unit weight from the approved configuration drawing.
What is the difference between HWDP and a drill collar?
A drill collar is generally heavier and much stiffer and is used close to the bit. HWDP provides a more gradual transition between the collars and standard drill pipe while also adding weight.
Which drill collar connections are available?
The current product page lists API Reg, IF and FH connection families. The exact compatible designation, pin/box arrangement, bore and make-up requirements must be confirmed for the collar size.
Is a 4145H drill collar non-magnetic?
No. Standard 4145H alloy steel is magnetic. A non-magnetic drill collar is a separate material and inspection category for use around magnetic survey instruments and must be specified separately.
What information is needed for drill collar pricing?
Provide OD, bore, length, slick or spiral profile, connection, material and hardness requirements, API basis, service conditions, inspection scope, quantity, destination and delivery schedule.
Request a Drill Collar Technical Quotation
Send your BHA requirement or approved drawing. Shangshanpetro will review the requested OD, bore, length, profile, connection, material and inspection package.
- OD, bore and overall length
- Slick or spiral configuration
- Connection and make-up requirements
- Service and inspection conditions
- Quantity, destination and schedule
