Coiled Tubing

Coiled tubing is a long, flexible steel pipe wound onto a spool, designed for repeated deployment in oil and gas wells. Unlike conventional jointed casing, it eliminates the need for thread connections, enabling continuous circulation during well interventions—an essential feature for maintaining wellbore pressure and avoiding formation damage.

Key Characteristics

Dimensions: Diameters range from 0.75 to 4.5 inches (19–114 mm), with 2-inch being the most common size. Single spools can hold over 40,000 ft (12,000 m) of tubing.

Material Grades: Yield strengths span 55,000–120,000 psi (e.g., CT70, CT80, CT100, CT110 per API SPEC 5ST), balancing strength and fatigue resistance for deep or high-angle wells.

Applications

Continuous tubing supports a wide range of oilfield operations:

Well Servicing: Cleaning wells, removing sand bridges, and repairing downhole equipment without killing the well.

Stimulation & Fracturing: Delivering fluids for hydraulic fracturing in shale gas wells, where its flexibility allows access to horizontal sections.

Drilling & Completion: Drilling small-diameter wells or aiding in completion tasks like screen installation.

Logging & Intervention: Deploying tools for real-time downhole data collection (e.g., pressure, temperature) or repairing damaged casings.

Industry Standard: API SPEC 5ST

The American Petroleum Institute's API SPEC 5ST is the global benchmark for continuous tubing manufacturing. It specifies:

Material Requirements: Chemical composition (e.g., carbon, manganese limits) and mechanical properties (tensile strength, flattening performance).

Testing Protocols: Hydrostatic pressure tests (minimum 1.6× yield strength for 15 minutes), ultrasonic flaw detection, and dimensional inspections.

Marking & Protection: Permanent labels on spools indicating grade, size, and manufacturer, plus corrosion-resistant coatings for storage.

Advantages Over Conventional Methods

Cost Efficiency: Faster rig-up and pipe handling reduce operational time by 30–50% compared to jointed tubing.

Safety & Environment: Smaller rig footprint and fewer personnel lower HSE risks. Continuous circulation minimizes well control issues.

Versatility: Suits deep wells (≥5,000 m), high-temperature (≤150 °C), and high-pressure (≤150 MPa) environments, as seen in projects like China's Shale Gas fields.

About Manufacturer: China OAK Oilfield Pipe Manufacturing Co., Ltd

Products feature:

High-Toughness Alloys: Engineered for ultra-deep wells (e.g., ≥5,000 m depth) and corrosive environments (e.g., sour gas wells).

Custom Solutions: Tailored diameters (19–114 mm) and wall thicknesses (1.9–7.6 mm) for specific client needs, including subsea applications.

Continuous tubing's adaptability and compliance with API SPEC 5ST make it a cornerstone of modern oil and gas operations, enabling efficient, safe, and cost-effective well management worldwide.