Publish Time: 2025-05-15 Origin: Site
In the ever-evolving oil and gas industry, efficiency, durability, and cost-effectiveness are essential. One technology that has significantly improved operations in the field is welded coiled tubing. This continuous length of pipe, created through welding processes, is used for a variety of downhole operations, from well intervention to drilling and production support.
Though seamless coiled tubing has historically been the standard, advancements in materials and welding techniques have made welded coiled tubing a reliable and cost-effective alternative. In this article, we’ll explain what welded coiled tubing is, explore its major applications in the oilfield, and detail the many benefits it offers.
Welded coiled tubing is a long, flexible metal pipe produced by welding strips of steel or alloy into a continuous tube. Unlike seamless coiled tubing, which is extruded from a single piece of metal, welded tubing is formed by shaping and welding together the edges of flat strips, then drawing them into their final dimensions.
Thanks to advancements in longitudinal welding techniques—particularly high-frequency electric resistance welding (ERW)—welded coiled tubing now provides exceptional strength and integrity, often matching or exceeding the performance of seamless tubing for many oilfield uses.
The production of welded coiled tubing involves several carefully controlled steps:
Raw Material Preparation: High-grade steel or alloy strip is selected and prepared for forming.
Forming: The strip is gradually formed into a round tube shape using precision rollers.
Welding: The edges are joined using ERW, which produces a strong, uniform weld without adding filler material.
Heat Treatment: Post-weld heat treatment may be applied to normalize the weld zone and restore mechanical properties.
Cold Drawing: The welded tube is drawn to its final diameter and wall thickness, improving surface finish and strength.
Non-Destructive Testing: The entire length of tubing is inspected using techniques like ultrasonic or eddy current testing to ensure quality.
Coiling: The tubing is wound onto reels for transportation and deployment in the field.
Welded coiled tubing is widely used across multiple phases of oilfield operations, both onshore and offshore. Its continuous length and flexibility allow it to be deployed quickly without the need for time-consuming pipe connections. Below are the key areas where welded coiled tubing plays a major role:
Welded coiled tubing is commonly used in well intervention services, where it helps restore or enhance the productivity of an oil or gas well. It is often used for:
Cleaning and flushing wells
Removing sand or scale deposits
Delivering chemical treatments
Logging and monitoring
Its flexibility allows it to access highly deviated or horizontal wells, improving efficiency compared to traditional pipe-based interventions.
In acidizing operations, welded coiled tubing is used to deliver acid into the reservoir to dissolve rock formations and improve flow. It can also serve as a delivery method for hydraulic fracturing fluids in low-volume fracturing jobs, particularly in tight gas or shallow formations.
When wells stop flowing naturally, nitrogen is pumped through coiled tubing to displace fluids and reduce bottom-hole pressure, allowing oil or gas to resume flowing. Welded coiled tubing is well suited for these operations because it can be rapidly mobilized and inserted into live wells.
Slim-hole and underbalanced drilling operations increasingly use coiled tubing. Welded coiled tubing can be fitted with drilling tools and sensors for re-entering older wells or sidetracking without removing the entire casing. This minimizes downtime and reduces costs.
Cement plugs or bridge plugs can be accurately placed using coiled tubing. The continuous nature of the tubing ensures precise depth control and minimizes fluid losses during placement.
Beyond well operations, welded coiled tubing is also used in cleaning and maintenance of pipelines. It can carry cleaning pigs, scrapers, or pressurized fluids to remove debris, hydrate plugs, or perform hydrostatic tests.
Welded coiled tubing offers several significant advantages that make it an appealing option in the oil and gas industry. Here are some of the key benefits:
The welded process allows for greater control over raw material usage and production efficiency. Unlike seamless tubing, which requires extensive forging or extrusion, welded tubing is more material-efficient and less labor-intensive, lowering the overall manufacturing cost.
Welded coiled tubing can be produced in custom wall thicknesses, diameters, and lengths, often exceeding 30,000 feet in a single reel. This flexibility allows engineers to specify tubing that fits unique well conditions or operational needs.
Modern welding technology produces tubing with mechanical properties that closely match or even surpass seamless products. Proper post-weld treatments and testing ensure that the weld seam does not become a weak point in high-pressure, high-stress environments.
Because the manufacturing process is streamlined, welded coiled tubing is often available faster than seamless alternatives. This can be critical for operators facing tight drilling or completion schedules.
Thanks to precise thickness control, welded coiled tubing can be optimized for lighter weight without sacrificing strength. Its flexibility makes it easier to deploy in tight well paths or complex reservoir geometries.
Welded tubing production generates less waste and consumes less energy compared to seamless tubing, making it a more sustainable option for environmentally-conscious operators.
While welded coiled tubing has many advantages, there are certain situations where seamless tubing may still be preferred. For example:
In ultra-high-pressure or corrosive environments, seamless tubing may offer additional safety margins.
Weld quality must be rigorously controlled; any flaw in the weld can lead to early failure under load.
Operators must ensure that the tubing meets industry standards such as API 5ST, particularly for offshore and critical applications.
However, with today’s advanced testing and manufacturing techniques, these risks are largely mitigated when sourced from reputable manufacturers.
Welded coiled tubing has proven itself as a reliable and efficient tool in modern oilfield operations. With a wide range of applications—from well intervention to drilling support and fluid delivery—it has become an essential asset for improving well productivity and reducing downtime. Its lower production cost, customizable design, and improved mechanical performance make it an increasingly attractive alternative to traditional seamless tubing.
As the demand for faster, more efficient oilfield operations continues to grow, welded coiled tubing will play an even greater role in meeting these challenges. Operators who understand its benefits and limitations can make more informed decisions that optimize both performance and cost.