High-tier electromagnetic wave resistivity logging demands flawless tool-body physics. Serving as the structural foundation for downhole propagation resistivity tools, our non-magnetic LWD resistivity subs provide complete electromagnetic transparency combined with maximum mechanical durability under extreme cyclic fatigue and torsional stresses.
1. Precision Machining for Complex Antenna Geometries
The primary challenge in manufacturing electromagnetic logging collars lies in executing complex external profiles without compromising tool-body strength. We machine custom transmitter and receiver antenna grooves directly into the outer diameter of solid austenitic forgings.
- Optimized Recesses: Recessed coil geometries are engineered with smooth transition radii to eliminate localized stress risers under continuous rotating bending loads.
- Protective Shield Integration: Depths and clearances are tightly controlled to allow flush mounting of non-metallic composite shields or rubber overmolding, protecting internal windings from borehole abrasion.
2. Deep Gun-Drilled Wireways & HPHT Integrity
Internal signal routing through thick-walled non-magnetic alloy collars requires advanced machining capabilities. Our facilities utilize specialized deep-hole gun-drilling to machine longitudinal conduits through the collar wall, safely shielding electronic harnesses from extreme hydrostatic fluid pressures.
Every pressure port, sensor pocket, and bulkhead feedthrough connector is manufactured under micron-level tolerances. Each finished collar undergoes hydro-testing and full non-destructive examination (NDE) to certify zero-leakage performance under downhole pressures exceeding 20,000 psi.
3. Collaborative OEM Engineering
Because phase-shift and attenuation resistivity tools rely on distinct coil spacings and antenna configurations, we manufacture every resistivity sub strictly to your proprietary engineering specifications:
- Material Certification: High-purity austenitic stainless steel with verified magnetic permeability( μr< 1.005).
- Full Connection Compliance: API Spec 7-1 rotary shouldered pin and box connections with cold-rolled thread roots.
- Optional Hardbanding: Strategically applied non-magnetic wear bands to extend tool life across abrasive formations without distorting resistivity sensor readings.
4. Technical Specification of Non-Magnetic LWD Resistivity Sub
| Nominal O.D. (in) | API Connection | Max. Blank Length (ft) | Antenna Grooves & Deep-Hole Wireways | Magnetic Permeability (μr) |
|---|---|---|---|---|
| 4 3/4" | NC38 (3 1/2" IF) | Custom (Up to 31 ft) | Machined to Client IP / Drawings | ≤ 1.005 |
| 6 1/2" | NC50 (4 1/2" IF) | Custom (Up to 31 ft) | Machined to Client IP / Drawings | ≤ 1.005 |
| 6 3/4" | NC50 (4 1/2" IF) | Custom (Up to 31 ft) | Machined to Client IP / Drawings | ≤ 1.005 |
| 8" | 6 5/8" REG | Custom (Up to 31 ft) | Machined to Client IP / Drawings | ≤ 1.005 |
| 9 1/2" | 7 5/8" REG | Custom (Up to 31 ft) | Machined to Client IP / Drawings | ≤ 1.005 |