Content Menu
● Applications of Coiled Tubing
● The Manufacturing Process of Coiled Tubing
>> 2. Slitting the Steel Sheets
>> 5. Sizing and Heat Treatment
>> 7. Spooling and Final Inspection
● Recent Advancements in Coiled Tubing Technology
>> 2. Enhanced Manufacturing Processes
>> 3. Integrated Downhole Tools
● Coiled Tubing Drilling (CTD)
● Challenges in Coiled Tubing Operations
● FAQ
>> 1. What materials are used in making coiled tubing?
>> 2. How long can coiled tubing be?
>> 3. What are common applications for coiled tubing?
>> 4. How does coiled tubing differ from traditional drilling methods?
>> 5. What testing does coiled tubing undergo before use?
Coiled tubing (CT) is a continuous length of small-diameter steel pipe that is widely used in the oil and gas industry for various applications, including drilling, workover, and intervention operations. The manufacturing process of coiled tubing is intricate and involves several key steps to ensure the final product meets the required specifications for strength, flexibility, and durability. This article will delve into the detailed process of how coiled tubing is made, supported by images and videos to enhance understanding.
Coiled tubing refers to a long metal pipe, typically ranging from 1 to 3.25 inches in diameter, which is supplied spooled on a large reel. The unique feature of coiled tubing is its ability to be continuously fed into the wellbore without the need for joints, which enhances its efficiency in various operations.
Coiled tubing is utilized for multiple purposes in the oil and gas sector, including:
- Well Cleanouts: Removing debris or blockages from wellbore.
- Acid Stimulation: Injecting acid to enhance production by dissolving limestone or other formations.
- Fracturing: Creating fractures in rock formations to improve oil and gas flow.
- Cementing: Placing cement in the wellbore to secure casing.
- Logging: Gathering data about the geological formations encountered.
- Plug Setting or Retrieval: Installing or removing plugs used to isolate sections of the well.
The manufacturing of coiled tubing involves several steps that transform raw materials into the final product. Below are the detailed stages involved in this process:
The first step in manufacturing coiled tubing is acquiring steel stock, typically supplied in 40- to 48-inch wide sheets. These sheets are wrapped into a "master coil" that can weigh approximately 40,000 pounds.
Once the steel sheets are acquired, they are slit into continuous strips of specific widths. This width determines the circumference of the final coiled tubing.
The next step involves welding these strips together to form a continuous length of steel. This is done using high-frequency induction welding (HFI), where electric current generates heat at the edges of the strips, allowing them to fuse together without additional filler material.
After welding, the flat steel strips are run through a series of roller dies that shape them into a tube. The edges of the tube walls are brought close together before being welded.
The newly formed tube then goes through a sizing mill that adjusts its diameter and ensures it meets specific tolerances. Following this, full-body heat treatment is performed using induction coils to relieve stress and enhance ductility.
To ensure quality and safety, each spool of coiled tubing undergoes hydrostatic testing using water treated with corrosion inhibitors. This test checks for leaks and verifies that the tubing can withstand high pressures.
Finally, once testing is complete, the coiled tubing is spooled onto either a wooden or steel take-up reel for transportation. Each spool is assigned a unique identification number along with documentation detailing its specifications and test results.
Coiled tubing offers several advantages over traditional methods:
- Continuous Length: Reduces connection points which minimizes potential failure sites.
- Flexibility: Can be easily maneuvered in various wellbore conditions.
- Efficiency: Allows for rapid deployment and retrieval during operations.
The coiled tubing industry has seen significant advancements over recent years that have enhanced its applications and efficiency:
The development of high-strength metals and composite materials has enabled the production of coiled tubing strings with higher tensile and burst strengths. Advanced materials allow for thinner tubing walls while maintaining structural integrity, resulting in lighter, more flexible coiled tubing that can endure higher pressure and temperature situations.
Innovations such as laser welding, precision machining, and non-destructive testing have increased the quality and reliability of coiled tubing. These advancements ensure consistent dimensional accuracy, surface finish, and mechanical properties, reducing the risk of defects and failures during operation.
Modern coiled tubing units (CTUs) are often equipped with integrated downhole tools that allow operators to perform multiple tasks without needing to remove the CT string from the wellbore. This integration enhances operational efficiency by reducing time spent on rigging up or down between different operations.
Coiled tubing can also be employed for drilling operations known as Coiled Tubing Drilling (CTD). In CTD operations:
- The coiled tubing string acts as a drill pipe carrying a bottom hole assembly equipped with a drill bit.
- The CT string is rotated while being pushed into rock formations, allowing for efficient drilling without traditional rig setups.
CTD has proven particularly effective in horizontal drilling applications where traditional methods might struggle due to space constraints or wellbore conditions.
While coiled tubing presents many advantages, there are challenges associated with its use:
- Depth Limitations: As operators venture into deeper subsea oilfields, limitations become apparent due to fatigue life diminishing with increasing strength requirements at greater depths.
- Erosion Risks: Abrasive fluids pumped through coiled tubing can preferentially erode inner surfaces due to centrifugal forces acting on slurries within the pipe.
To mitigate these challenges, ongoing research focuses on developing stronger materials and innovative monitoring technologies that provide real-time data on wall thickness during operations.
The manufacturing process of coiled tubing is complex yet crucial for ensuring that it meets industry standards for performance under high-pressure conditions. From material acquisition to final inspection, each step plays an integral role in producing high-quality coiled tubing suitable for various applications in oil and gas exploration and production. Furthermore, advancements in technology continue to drive improvements in both manufacturing processes and operational efficiencies within this sector.
Coiled tubing is primarily made from high-strength low-alloy steels that meet specific yield strength requirements as outlined by industry standards.
A single spool of coiled tubing can exceed lengths of 25,000 feet depending on its diameter.
Common applications include well cleanouts, acid stimulation, fracturing, cementing, logging, and plug setting or retrieval.
Unlike traditional drilling methods that use jointed pipes requiring multiple connections, coiled tubing provides a continuous length that enhances efficiency and reduces failure points.
Coiled tubing undergoes hydrostatic testing to check for leaks and ensure it can withstand high pressures before being spooled for transportation.
[1] https://petrowiki.spe.org/Coiled_tubing
[2] https://www.drillingmanual.com/coiled-tubing-complete-guide/
[3] https://drillingcontractor.org/coiled-tubing-pushing-its-limits-by-going-bigger-expanding-niche-applications-thinking-riserless-4655
[4] https://www.petrosync.com/blog/what-is-coiled-tubing/
[5] https://en.wikipedia.org/wiki/Coiled_tubing
[6] https://www.esimtech.com/how-advancements-in-coiled-tubing-technology-are-revolutionizing-the-oil-and-gas-industry.html
[7] https://www.slb.com/resource-library/oilfield-review/defining-series/defining-coiled-tubing
[8] https://www.tenaris.com/media/kvzju2ht/coiled-tubing-downhole-applications.pdf
[9] https://www.youtube.com/watch?v=TlBawIjj3mM
[10] https://www.oilproduction.net/files/coiled_tubing_handbook.pdf
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