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3-1/2 API Standard Tubing is a mainstream standardized tubing for medium and deep oil and gas wells. Adopting seamless steel forming and unified API calibration on size and thread, it boasts high interchangeability and compatibility. It effectively solves rigidity and pressure resistance defects of non-standard and small-diameter tubing, serving as a core supporting pipe for deep oilfield development.
Compared with smaller tubing sizes such as 2 7/8", it provides higher flow capacity and improved mechanical strength, making it suitable for wells requiring higher production rates and pressure resistance.
Manufactured from API-compliant seamless steel pipe, the tubing is available in J55, N80 and P110 grades according to well depth and pressure requirements.
Production process includes:
Steel billet inspection → Hot rolling → Heat treatment → Straightening → Ultrasonic flaw detection → CNC threading → Hydrostatic
testing
This process ensures consistent mechanical properties and connection reliability during long-term downhole operation.
This 3-1/2 API Standard Tubing delivers excellent tensile, collapse and internal pressure resistance. Optimized API thread structure prevents leakage and pipe string disconnection.
It resists erosion from crude oil, natural gas and formation water, adapting to high-pressure, alternating-load deep well working conditions with low failure rate.
| Item | Specification |
| Standard | API Spec 5CT |
| Size | 3 1/2 inch |
| OD | 88.9 mm |
| Steel Grade | J55 / N80 / P110 |
| Manufacturing Type | Seamless |
| Connection | API BTC / EUE |
| Length Range | R1 / R2 / R3 |
| Application | Oil production, water injection |
| Inspection | Hydrostatic test, NDT, dimensional inspection |
The table below lists core parameters of 2 7/8", 3 1/2 and 4 1/2" API standard tubing, covering mainstream oilfield specifications for intuitive working condition matching and project selection.
| Parameter Item | 2 7/8 API Standard Tubing | 3-1/2 API Standard Tubing | 4 1/2 API Standard Tubing |
| Applicable Well Depth | Shallow & medium wells (≤2500m) | Medium & deep wells (2500m–4000m) | Deep & ultra-deep wells (>4000m) |
| Outer Diameter | 2.875 inch (73.02mm) | 3.5 inch (88.9mm) | 4.5 inch (114.3mm) |
| Main Wall Thickness | 5.51mm / 7.01mm | 6.45mm / 7.82mm | 7.37mm / 8.56mm |
| Grade | J55 / N80 / P110 | J55 / N80 / P110 | N80 / P110 (high strength) |
| Working Pressure | Medium-low pressure (≤35MPa) | Medium-high pressure (35–55MPa) | High pressure (≥55MPa) |
| Collapse Resistance | General | Excellent | Superior |
| Core Application | Shallow well production, conventional water injection | Deep well exploitation, high-pressure water injection, well reconstruction | Ultra-deep well, heavy oil and high-load oilfield projects |
| Comprehensive Cost | Low (cost-effective for shallow wells) | Medium (balanced performance & cost) | High (high-strength heavy-duty specification) |
3-1/2 API Standard Tubing provides a balanced solution between production capacity and mechanical strength for medium and deep oil wells. Compared with smaller diameter tubing, it offers larger flow capacity and improved pressure resistance, helping operators meet higher production requirements while maintaining reliable downhole performance.
Its standardized API dimensions simplify inventory management, equipment replacement and field maintenance. By reducing tubing failure risks and workover frequency, it helps improve well operating continuity and reduce long-term production costs.
3-1/2 API Standard Tubing is widely used in medium and deep oil and gas wells where higher flow capacity and structural strength are required.
Typical applications include:
• Oil and gas production wells – providing reliable fluid transmission from reservoir to surface facilities.
• High-pressure water injection wells – withstanding continuous pressure cycles during enhanced oil recovery operations.
• Well completion and workover projects – compatible with common completion tools for new wells and well rehabilitation.
• Tight oil and gas development – suitable for wells requiring stable tubing performance under complex downhole conditions.
• Underground gas storage wells – supporting repeated injection and withdrawal cycles.
Designed according to API 5CT dimensional requirements, 3 1/2 tubing is compatible with standard tubing couplings, completion equipment and common downhole tools.
The standardized outer diameter, wall thickness and connection specifications allow convenient integration with existing well designs, reducing installation complexity and replacement difficulties. It can be used for both new well completion and existing well maintenance projects where API-compliant tubing systems are required.
A1: It is mainly used for medium and deep oil/gas well exploitation, oilfield high-pressure water injection, wellbore renovation and unconventional energy development.
A2: It follows unified API 5CT standards with accurate dimensions and stable performance, featuring strong compatibility, low failure rate and convenient maintenance, avoiding assembly mismatch risks.
A3: Yes. High-strength steel and optimized heat treatment endow it with high pressure resistance and corrosion resistance, suitable for long-term deep well cyclic operation.
A4: Custom length cutting, thread reinforcement and anti-corrosion treatment are available on the premise of complying with API standards.
Choosing the right tubing supplier is crucial for mitigating downhole operational risks.
AOTE Pump offers:
API-compliant manufacturing controls
Stable steel grade consistency
Complete inspection documentation
Flexible batch supply capabilities
Tubing selection technical support
We are not only committed to supplying tubing, but also to helping customers select the appropriate tubing specifications based on well depth, pressure conditions, and production needs.
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No. 2 Xinwang Road, Shuangqiaohe Industrial Park, Jinnan District, Tianjin, China.
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