Flexi-string Anchor and Centralizer for Washout Section Navigation
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Solution Overview
Problem
Open hole completions in petroleum wells often result in washout sections due to the flow of hydrocarbons, which can cause tools to become stuck, as the enlarged section is larger than the casing shoe and third casing string, leading to operational challenges.
Innovation Solution
A flexi-string system is deployed with a smaller outer diameter than the casing shoe, featuring an anchor, centralizers, and a roller guide to center and secure the string within the casing shoe, preventing tools from contacting the washout section and allowing for tool passage without getting stuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an open hole completion is used to allow hydrocarbons to flow freely from the formation, then production efficiency is improved, but washout sections are created that cause tools to become stuck
Solution Approach 1:
The patent introduces a casing shoe as an intermediary structure between the casing and the washout section. The casing shoe has a smaller outer diameter than the washout section, creating a tapered transition zone that prevents tools from becoming stuck while still allowing the washout section to exist for production purposes
Solution Approach 2:
The wellbore is segmented into distinct zones: the cased section, the casing shoe transition zone, and the open hole washout section. This segmentation allows each zone to serve its specific function - the casing shoe acts as a mechanical transition that prevents tool snagging while the washout section maintains production capability
2Ease of operation
If the outer diameter of the flexi-string is made smaller than the casing shoe inner diameter to allow passage, then tool passage through washout section is enabled, but anchoring and centering stability may be compromised
Solution Approach 1:
The flexi-string incorporates dynamic elements including rollers that can rotate to accommodate the tapered geometry of the casing shoe, and centralizers that can expand or adjust to maintain centering. This dynamic adaptability allows the string to pass through the transition zone while maintaining stability
Solution Approach 2:
The anchor mechanism is designed to engage with the casing shoe before the tool string reaches the washout section. The centralizers are pre-positioned to ensure proper centering is established during the passage through the tapered zone, preventing tool snagging before it occurs
Data Source
AI summary
A system includes a flexi-string having a first lateral end, a second lateral end, and an outer diameter. The outer diameter defines an outer circumferential surface, and the outer diameter is smaller than an inner diameter of a casing shoe. The system further includes an anchor disposed on the outer circumferential surface of the first lateral end, where the anchor interacts with the casing shoe, or a last joint of casing, to hold the first lateral end of the flexi-string within the casing shoe. The system also has centralizers located between the first lateral end and the second lateral end of the flexi-string. The centralizers are configured to center the flexi-string within the casing shoe and the washout section. Finally, the system includes a roller guide for lowering the flexi-string inside the casing shoe and to a depth below the washout section of the well.