Product Overview

DEENPU API 7-1 Non-Magnetic Drill Collar (NMDC) in P530 / P550 Non-Magnetic Alloy Steel

DEENPU Non-Magnetic Drill Collar (NMDC) is a specialized drill string component manufactured from premium non-magnetic stainless steel alloys including P530, P550, and AISI 4145HM. Unlike conventional drill collars made from high-strength magnetic alloy steel, NMDC is engineered with a unique material composition that minimizes magnetic interference, making it essential for directional drilling, horizontal drilling, and MWD (Measurement While Drilling) / LWD (Logging While Drilling) operations.

Manufactured in strict accordance with API Spec 7-1 standards, DEENPU NMDC is available in three structural types: Slick, Spiral, and Flex. Each collar is designed to serve dual functions: housing the sensitive MWD/LWD electronic measurement tools in the bottom hole assembly (BHA), while simultaneously providing the necessary weight on bit (WOB) for efficient drilling. The non-magnetic properties ensure that the sensitive magnetometers and sensors in the MWD tools are not affected by the magnetic field of the surrounding drill string, enabling accurate wellbore trajectory measurement and precise directional control.

Available in outer diameters from 3-1/8″ (79.4 mm) to 11″ (279.4 mm) with standard lengths of 9.14 m (30 ft) or 9.45 m (31 ft), DEENPU NMDC features API-standard threaded connections including NC, REG, FH, and IF series. All collars undergo full-length ultrasonic inspection, dimensional verification, and magnetic permeability testing, with complete inspection certificates provided with each unit.

NMDC Types & Configurations

DEENPU offers three specialized non-magnetic drill collar types, each engineered for specific drilling requirements:

How the Non-Magnetic Drill Collar Works

The non-magnetic drill collar performs three critical functions in the bottom hole assembly (BHA):

1. MWD/LWD Tool Housing — The NMDC is placed immediately above the MWD/LWD tool assembly in the BHA. Its non-magnetic alloy construction creates a magnetically neutral zone that isolates the sensitive magnetometers and directional sensors from the magnetic field of the conventional magnetic drill collars and drill pipe above. Without this isolation, the Earth’s magnetic field measurements would be distorted by the magnetic field of the steel drill string, rendering the directional survey data inaccurate. The NMDC typically spans 60-120 feet (2-4 stands) to provide sufficient magnetic isolation for the sensors.
2. Weight on Bit (WOB) Provider — Like conventional drill collars, the NMDC provides concentrated weight at the bottom of the drill string to apply the necessary force on the drill bit. Its thick wall and heavy construction deliver approximately 80-90% of the weight per foot of an equivalent magnetic drill collar. The weight is transmitted through the tool joint connections to the bit, enabling efficient rock penetration. In directional drilling, the NMDC weight is carefully calculated to provide sufficient WOB without exceeding the limits of the directional motor or rotary steerable system.
3. Bottom Hole Assembly Stabilization — The NMDC acts as a stabilizing element in the BHA, providing stiffness and pendulum effect to maintain wellbore trajectory. The collar’s mass and rigidity help resist lateral forces from the bit and formation, keeping the well path on the desired azimuth and inclination. In combination with stabilizers and reamers, the NMDC helps control the build rate and walk rate of the well, which is critical for hitting the target zone in directional and horizontal wells. The flex type NMDC provides additional steerability in tight-radius curves.

Key Features

Applications

• MWD (Measurement While Drilling) operations — Housing and protecting MWD sensors including magnetometers, accelerometers, and gamma ray detectors from magnetic interference
• LWD (Logging While Drilling) operations — Providing magnetically neutral environment for resistivity, density, neutron, and sonic logging tools
• Directional drilling — Essential component in the BHA for accurate wellbore trajectory measurement and directional control with steering tools
• Horizontal drilling — NMDC in the build section and lateral section to maintain magnetic isolation for the sensor package while providing weight on bit
• Extended reach drilling (ERD) — Long NMDC sections in high-angle wells to maintain directional accuracy over long laterals
• Geosteering operations — Precision well placement in thin reservoirs where accurate inclination and azimuth measurement is critical
• Sour gas drilling (H2S) — Corrosion-resistant non-magnetic alloy suitable for hydrogen sulfide bearing formations
• Offshore drilling — Marine-grade corrosion resistance for offshore platform and subsea drilling operations

Technical Specifications

Bending Strength Ratio (BSR) is the ratio of the bending strength of the box to the bending strength of the pin. API 7-1 recommends BSR between 2.25:1 and 3.20:1 for optimal fatigue performance. All dimensions per API 7-1 with +1.59 mm / -0 mm tolerance on OD. Standard length tolerance: +152.4 mm / -0 mm. Contact us for non-standard sizes, custom lengths, and premium thread connections.

When Ordering, Please Specify

1. NMDC TypeSlick, Spiral, or Flex type. Spiral type recommended for formations with high differential sticking risk. Flex type recommended for high build rate directional wells.
2. Outer DiameterStandard OD: 79.4 mm (3-1/8″) to 279.4 mm (11″). Specify based on hole size and BHA design requirements.
3. Inner DiameterStandard ID: 31.8 mm (1-1/4″) to 76.2 mm (3″). Specify ID for MWD tool passage and flow requirements.
4. Connection Type & SizeNC series (NC23 through NC70), REG series (6-5/8 REG, 7-5/8 REG, 8-5/8 REG), FH, or IF connections. Specify pin and box requirements.
5. Material GradeP530 (standard non-magnetic), P550 (higher strength non-magnetic), or AISI 4145HM (modified non-magnetic alloy). Specify based on strength and magnetic permeability requirements.
6. Magnetic Permeability RequirementMaximum relative permeability value required. Standard P530: <1.005. P550: <1.003. Specify if lower permeability is required.
7. LengthStandard: 9.14 m (30 ft) or 9.45 m (31 ft). Custom lengths available.
8. Coating / Surface TreatmentPhosphor bronze or copper-based anti-galling coating on threads. External coating or hardbanding options available.
9. Certification RequirementsAPI 7-1 certification, material test certificates (MTC), ultrasonic test certificates, magnetic permeability test reports, and third-party inspection (DNV, BV, SGS).
10. Quantity & DeliveryTotal quantity, delivery schedule, and shipping destination. Thread protectors and export packaging included as standard.

Custom Manufacturing & OEM Capability

• Custom OD and ID Sizes — Non-standard outer and inner diameters manufactured to customer specifications for specialized BHA designs.
• Premium Thread Connections — Double-shoulder connections, proprietary connections, and premium sealing threads for high-pressure applications.
• Spiral Groove Design — Custom spiral groove pitch, depth, and profile optimized for specific formation types and flow rates.
• Material Grade Selection — P530, P550, AISI 4145HM, or custom non-magnetic alloy grades with specified magnetic permeability and mechanical properties.
• Anti-Galling Coatings — Phosphor bronze, copper-nickel, or proprietary low-friction coatings on threads to prevent galling during make-up and break-out.
• Hardbanding — Arnco 100XT or 300XT hardbanding applied to tool joints for extended connection life in abrasive formations.
• Internal Coating — Corrosion-resistant internal coating for H2S and CO2 environments. Protects MWD tool housing bore from corrosion.
• Special Lengths & Configurations — Short collars, pup joints, and custom lengths for specific BHA spacing requirements.

Quality Control & Testing Standards

• Material chemical composition verified per batch. Chromium, nickel, manganese, and nitrogen content verified for non-magnetic properties.
• Material mechanical properties tested including tensile strength, yield strength, elongation, and impact toughness per ASTM A370.
• Magnetic permeability tested on each collar using a permeability meter. Relative permeability verified against specification (P530 <1.005, P550 <1.003).
• Tool joint threads inspected with API ring and plug gauges per API 7-1. Standoff, thread length, and pitch diameter verified.
• Full-length ultrasonic inspection (UT) over 100% of the bar length. Longitudinal and transverse defect detection per API 7-1.
• Dimensional inspection including OD, ID, straightness, length, and ovality per API 7-1 tolerances.
• Surface inspection for cracks, seams, and defects using magnetic particle inspection (MPI) on threads and critical areas.
• Drift test performed with API standard drift mandrel to verify minimum internal diameter throughout the collar length.
• Material test certificates (MTC) per EN 10204 3.1 provided for all collar and tool joint materials.
• Third-party inspection and certification by DNV, BV, SGS, or ABS available upon request.

Frequently Asked Questions