Nested Coiled Tubing for Extended Reach Wellbores
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Solution Overview
Problem
Conventional coiled tubing deployment techniques have limited extended reach capability, making it difficult to service wells that require deeper penetration, as existing downhole tractor solutions are complex and expensive.
Innovation Solution
A method involving a larger diameter coiled tubing with a dynamic sealing element at its bottom end, allowing a smaller diameter coiled tubing to be translated through it, with the annulus pressurized to inhibit bending and buckling, and equipped with a BHA for increased reach, including vibrators and tractors for further deployment assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional coiled tubing deployment techniques are used, then the deployment process is simple, but the extended reach capability is limited
Solution Approach 1:
The patent employs nested coiled tubing where an inner coiled tubing string is deployed through an outer coiled tubing string. The inner tubing has a smaller outer diameter than the inner diameter of the outer tubing, allowing it to pass through. This nesting configuration enables the inner tubing to reach further into deviated or horizontal wellbores than either tubing could achieve independently, thereby extending the reach capability without requiring complex downhole tractor systems.
2Length of moving object
If downhole tractor technology is used to increase pull force, then the extended reach is improved, but the device complexity and cost increase
Solution Approach 1:
The patent eliminates the need for complex downhole tractor systems by using nested coiled tubing configuration. The inner tubing can be deployed to greater depths and deviated sections by passing through the outer tubing, achieving extended reach through geometric configuration rather than mechanical pull force generation downhole.
Solution Approach 2:
The patent utilizes fluid pressure applied to the annulus between the outer and inner coiled tubing strings to reduce friction and enable deployment. By pressurizing the annular space, the system reduces the frictional resistance that would otherwise prevent the inner tubing from being pushed or pulled through the outer tubing to extended depths, thereby achieving long reach without complex downhole mechanical systems.
3Length of moving object
If friction reducing agents are used, then the extended reach is improved, but the deployment complexity increases
Solution Approach 1:
The patent uses controlled fluid pressure applied to the annulus between tubing strings as a systematic approach to friction reduction. Rather than relying on chemical friction reducing agents, the system uses mechanical pressure differentials to overcome friction, providing a more controllable and monitorable method for achieving extended deployment.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly increases the horizontal reach of coiled tubing, allowing deployment to locations previously inaccessible, with simpler and cheaper solutions compared to conventional downhole tractors, while maintaining operational flexibility for well treatments.
Implementation Method 1
The annular region between the first coiled tubing and the second coiled tubing can be pressurized during the deployment of the second coiled tubing. Pressurization of the annular region inhibits bending and buckling of the second coiled tubing string within the first coiled tubing.
Implementation Method 2
In cases where the BHA includes a vibrator, the second coiled tubing can be vibrated during deployment to further increase its horizontal reach.
Implementation Method 3
The technologies that have been considered for extending the reach of coiled tubing fall into two different categories: reducing friction or generating pull force downhole. Technologies that aim to reduce friction in order to increase coiled tubing reach include using friction reducing agents and downhole vibration technologies.
Implementation Method 4
For hydraulically powered downhole tractors, the pull force generated by available downhole tractors is between 4000-8000 lbs.
Data Source
AI summary
A larger diameter coiled tubing is run into an extended reach deviated wellbore to a location at or near its horizontal reach limit. The smaller diameter coiled tubing is then run through the larger diameter tubing until the end of the smaller tubing protrudes from the larger tubing. The smaller tubing is then run further into the wellbore to a location further than would have been possible if either tubing had been run alone. Supplementary reach-increasing techniques such as friction reducing vibrators and/or downhole tractors can also be used in combination with the described techniques.