Flexible Casing Guide for Curved Wellbore Navigation
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Solution Overview
Problem
The difficulty in running large diameter casing through curved sections of wellbores due to high deflection forces, which can cause the casing to 'dig into' the rock formation, leading to sticking and damage, especially in formations with unplanned deviations and high curvature.
Innovation Solution
A flexible casing guide with reduced stiffness, positioned at the leading edge of the casing, which allows for easier deflection through curved sections by distributing the bending force and reducing compressive stress on the formation, constructed from materials like aluminum or fiber-reinforced composites with adjusted modulus and area moment of inertia.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large diameter steel casing is used, then casing strength and structural integrity are improved, but the force required to deflect the casing through curved wellbores increases significantly
Solution Approach 1:
The casing string is segmented into two distinct parts: a flexible guide section (20-500 ft) with lower stiffness attached to the leading end of the stiffer production casing. This segmentation allows the flexible section to absorb bending stresses and navigate curved wellbores, while the main casing body maintains its structural strength and integrity for production requirements.
2Stress or pressure
If the casing shoe contact area with the formation is increased, then compressive stress on the formation is reduced, but the device complexity increases
Solution Approach 1:
The guide section functions as a flexible shell that distributes contact forces over a larger area of the formation. Its flexibility allows it to conform to curved wellbore paths while spreading the compressive stress, preventing the casing from digging into the formation without requiring complex shoe structures.
3Force
If the stiffness of the casing is reduced to ease deflection through curves, then the force required to traverse curved sections is reduced, but the casing strength and structural integrity deteriorate
Solution Approach 1:
Different sections of the casing string are assigned different stiffness properties tailored to their specific functions. The guide section at the leading end has lower stiffness (EI about 5% to 80% of the casing) to facilitate navigation through curves, while the main production casing maintains high stiffness to ensure structural integrity and strength for production requirements.
4Strength
If a rigid casing shoe is used, then the casing maintains structural integrity, but the casing may dig into the formation in highly curved sections
Solution Approach 1:
The flexible guide section serves as an intermediary between the rigid production casing and the curved wellbore environment. It absorbs the bending stresses and adapts to curved paths, preventing the rigid main casing from directly contacting and digging into the formation while maintaining overall structural integrity.
Data Source
AI summary
A flexible wellbore casing guide having a tubular body positioned at an end of a wellbore casing having a lower stiffness than the wellbore casing, the casing guide can be a section of fiber reinforced composite tubing.