Non-Magnetic Drill Collars for MWD/LWD in Directional Drilling
Non-magnetic drill collars are essential components in oil and gas directional and horizontal drilling assemblies, positioned directly above the MWD/LWD tool to provide a magnetically neutral zone for accurate geomagnetic measurements. Unlike standard steel collars, these collars are engineered from high-purity austenitic alloys with relative permeability μr ≤ 1.005, ensuring minimal distortion of the earth’s magnetic field around sensitive downhole sensors.
In addition to enabling precise azimuth determination, they deliver the necessary weight-on-bit (WOB) and maintain bottom-hole assembly (BHA) stability under high-torque, high-pressure conditions typical in deepwater or extended-reach wells.
Key Technical Properties
l Relative permeability (μr): ≤ 1.005 — verified per ASTM A342/A753
l High strength-to-density ratio: Optimized for BHA performance without compromising signal integrity
l Excellent fatigue resistance: Suitable for long-duration rotary and RSS operations
l Corrosion resistant: Performs reliably in seawater, H₂S, and CO₂ environments
Manufacturing Process & Material Integrity
l Forged from vacuum-induction melted (VIM) P650-grade non-magnetic steel
l Precision radial forging on 1800-ton press ensures uniform grain flow and eliminates internal voids
l Full solution annealing and stress-relief heat treatment achieve ASTM grain size 6–8
l Hardness variation across cross-section: ≤55 HBW — critical for thread reliability
Material Options:
Standard: P650-grade — tensile strength ≥1165 MPa, ideal for demanding offshore and deepwater applications
Economy Option: P550-grade — tensile strength ≥1035 MPa, suitable for onshore directional wells with moderate loads
Technical Specifications
|
Specification |
Value |
|
Material |
Austenitic non-magnetic steel (P650 or P550 grade) |
|
Relative Permeability (μr) |
≤ 1.005 |
|
Tensile Strength |
P650: ≥1165 MPa / P550: ≥1035 MPa |
|
Yield Strength |
P650: ≥1046 MPa / P550: ≥965 MPa |
|
Elongation |
≥36% |
|
Impact Toughness (KV₂ @ -20°C) |
Avg. ≥140 J |
|
Hardness |
38–39 HRC (P650) |
|
Thread Types |
API NC, FH, or custom premium connections |
|
Certification |
API 7-1 Monogram Licensed (with full traceability) |
Quality Assurance & Compliance
l Every collar undergoes 100% magnetic permeability testing using fluxgate magnetometers
l Hydrostatic pressure tested to 1.5× working pressure
l Supplied with mill test reports (MTRs), heat treatment certificates, and API 7-1 compliance documentation
l Optional third-party verification by Bureau Veritas or SGS available upon request
As an API 7-1 licensed manufacturer, we produce non-magnetic drill collars to meet stringent requirements for material purity, dimensional accuracy, and magnetic neutrality—ensuring reliable integration with modern MWD/LWD systems in demanding directional drilling environments.