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Drill Collars
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We are ready to help! If you're interested in one of our tools, or if you have a job in mind that needs a custom tool solution, don't hesitate to reach out and we'll be ready to get you exactly what you need - faster than you can get it anywhere else!
Bull Dog’s Drill Collars are made from solid bars—not tubing—for greater strength and consistent weight application. These collars stabilize milling and fishing assemblies and are dressed with heavy wall thickness for added torque resistance.
Applications
Providing weight on bit (WOB) for efficient drilling by transferring the necessary force to the drill bit.
Stabilizing the drill string to reduce vibrations, whip, and deviation while drilling.
Assisting in directional control during drilling operations by maintaining proper tool alignment.
Increasing tension and compressive strength in the bottom hole assembly (BHA).
Reducing drill pipe wear by keeping the drill string in tension and minimizing buckling.
Serving as a transition component between heavy BHA tools and lighter drill pipes.
Used in both vertical and directional wells for enhanced control and drilling performance.
Features & Advantages
High-Strength Construction: Manufactured from premium, heat-treated alloy steel for durability under extreme loads.
Optimized Weight and Balance: Provides proper weight on bit for efficient penetration without damaging the drill bit.
Machined for Precision: Tight manufacturing tolerances ensure reliable performance and reduced risk of connection failure.
Wear-Resistant Design: Built to withstand high torsional loads, abrasive formations, and long drilling intervals.
Standard and Custom Sizes: Available in multiple O.D./I.D. configurations, with custom machining options for unique needs.
Enhanced BHA Stability: Reduces toolface fluctuations and maintains proper hole trajectory.
Corrosion and Fatigue Resistance: Engineered for extended service life in harsh drilling environments.
Versatile Integration: Compatible with a variety of BHA components, including stabilizers, mills, and downhole motors.
Specifications
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Bull Dog stocks new Drill Collar Tubing (not drilled bar) in all your cased hole size applications.
Sizes:
3-1/8" X 1"
3-1/8” X 1-1/8”
3-1/8" X 1-1/2"
3-1/2" X 1-1/2"
4-1/8” X 2”
4-3/4" X 2-1/4"
All tubes are 30' X 6" blanks so we can thread the connection you prefer.
Frequently Asked Questions (FAQs)
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What are Bull Dog® Drill Collars used for?
Drill Collars are heavy, thick-walled tubulars used to apply weight-on-bit, increase string stiffness, and reduce vibration and deviation during milling, drilling, and cleanout operations. They're typically run above mills, scrapers, or bailers to improve performance and downhole tool control.
What sizes and thread types are available?
Bull Dog offers Drill Collars in a wide range of sizes, including:
3-1/8" O.D. with 2-3/8" IF
3-3/4" O.D. with 2-7/8" EUE
4-5/8" O.D. with 2-7/8" EUECustom O.D./I.D., length, and connection configurations are available to match your tool string or workover program.
Are Bull Dog Drill Collars made in-house?
Yes — every Drill Collar is precision-machined at our Houston facility using high-strength, heat-treated steel. That means faster turnaround, tighter QC, and custom builds you can trust in the field.
When should I include Drill Collars in my tool string?
Use Drill Collars when:
You need to apply controlled weight on a mill, bailer, or scraper
You’re working in deviated or crooked holes
You want to reduce string flex or dampen shock
You need torsional stability in a downhole assembly
Can Drill Collars be customized for my job?
Absolutely. Bull Dog can customize length, diameter, bore size, hardbanding, and connection type to match your well specs, tool stack, or weight requirements.