Segmented Coiled Tubing for Extended Reach Drilling

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Solution Overview

Problem

Conventional coiled tubing strings in directional drilling operations face limitations due to non-rotatability and buckling issues, which restrict the reach and efficiency of drilling, leading to increased costs and potential premature failure of drill string components.

Innovation Solution

A segmented coiled tubing string configuration with a downhole motor located upstream from the bottom hole assembly, incorporating a non-rotatable segment and a rotatable segment, and a twisting-restraining tool to mitigate twisting, along with advanced analysis and design techniques to optimize the string configuration and fluid flow characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional coiled tubing strings are used in directional drilling, then the drilling operation can be performed without conventional rigs, but the reach of the string is limited due to inability to rotate and buckling issues

Engineering Contradiction:

Improveelimination of conventional rigsVSAvoidreach of tubing string

Core Design Contradiction:

Ease of operationVSLength of moving object

Solution Approach 1:

The coiled tubing string is divided into multiple segments with different functional characteristics. Rotatable segments allow the BHA to rotate for directional control and extended reach, while non-rotatable segments maintain stability and prevent buckling. This segmentation enables the string to achieve both rotation capability for extended reach and stability to prevent buckling, resolving the technical contradiction.

Inventive Principle:

Principle #1Segmentation

2Length of stationary object

If coiled tubing string is compressed deeper into the formation, then drilling depth increases, but buckling becomes more acute reducing efficiency

Engineering Contradiction:

Improvedrilling depthVSAvoiddrilling efficiency

Core Design Contradiction:

Length of stationary objectVSProductivity

Solution Approach 1:

The string is segmented into rotatable and non-rotatable portions. The non-rotatable segments act as stabilizers that prevent buckling under compression, allowing the string to be pushed deeper into the formation while maintaining drilling efficiency. The rotatable segments enable directional control without inducing buckling.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different segments of the coiled tubing string are assigned different functional qualities: rotatable segments near the BHA provide flexibility and directional control, while non-rotatable segments provide structural stability and buckling resistance. This local differentiation allows the string to achieve both depth and efficiency.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If coiled tubing string is used in deviated wells, then directional drilling is enabled, but lateral or sinusoidal buckling modes occur under compression

Engineering Contradiction:

Improvedirectional drilling capabilityVSAvoidtubing string stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The coiled tubing string is divided into rotatable and non-rotatable segments. The non-rotatable segments provide structural stability to prevent lateral and sinusoidal buckling modes in deviated wells, while the rotatable segments enable directional drilling capability by allowing the BHA to rotate and change direction.

Inventive Principle:

Principle #1Segmentation

4Length of moving object

If steel coiled tubing is used for extended reach drilling, then drilling can proceed, but fatigue from cyclic bending causes premature failure

Engineering Contradiction:

Improveextended reach capabilityVSAvoiddrill string component life

Core Design Contradiction:

Length of moving objectVSReliability

Solution Approach 1:

The string is segmented to distribute bending stresses. Rotatable segments accommodate directional changes with controlled bending, while non-rotatable segments provide structural support that reduces cyclic bending fatigue. This segmentation extends the operational life of the coiled tubing by preventing premature fatigue failure.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11142963B2Optimized coiled tubing string design and analysis for extended reach drilling

Publication Date: 2021.10.12 LANDMARK GRAPHICS CORP

AI summary

System and methods for optimizing coiled tubing string configurations for drilling a wellbore are provided. A length of a rotatable segment of a coiled tubing string having rotatable and non-rotatable segments is estimated based on the physical properties of the rotatable segment. A friction factor for the rotatable segment is calculated based on the estimated length. An effective axial force for one or more points of interest along the non-rotatable and rotatable string segments is calculated, based in part on the friction factor. Upon determining that the effective axial force for at least one point of interest exceeds a predetermined maximum force threshold, an effective distributive friction factor is estimated for at least a portion of the non-rotatable segment of the string. The rotatable and non-rotatable string segments are redefined for one or more sections of the wellbore along a planned trajectory, based on the effective distributive friction factor.