Expandable Mill Blades for Subterranean Well Cleaning
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Solution Overview
Problem
Existing well cleaning technologies face limitations in effectively cleaning underground surfaces in subterranean wells, including the need for multiple trips, inability to function during torque-related issues, inadequate coverage in deviated or horizontal wells, and inefficiencies in handling debris and fluid flow.
Innovation Solution
A drift sub equipped with radially movable mill blades that can extend and retract within a tubular housing, allowing for cleaning of the well interior surface before completion hardware installation, with a mechanism involving inner and outer sleeves to control blade position and ensure full coverage and debris removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional mills are used for cleaning well surfaces, then cleaning function is provided, but multiple trips into the well are required and tool retrieval is needed when obstructions are detected
Solution Approach 1:
The patent combines the drift sub (used for detecting obstructions during casing drifting) with mill blades (used for cleaning) into a single integrated tool. This merging eliminates the need for separate trips to detect obstructions and clean the well, as both functions are performed by one tool during a single deployment.
Solution Approach 2:
The drift sub is designed to perform multiple functions: it can detect obstructions during drifting operations and simultaneously function as a cleaning tool with mill blades. This multi-functionality allows the tool to adapt to different operational needs without requiring tool changes or additional trips.
2Area of stationary object
If mill blades are extended to contact the interior surface of the casing, then cleaning coverage is improved, but the tool diameter increases and may cause interference with completion hardware
Solution Approach 1:
The mill blades are designed to be movable between retracted and extended positions. During deployment and navigation, the blades remain retracted to maintain a compact tool diameter. When cleaning is required, the blades extend to contact the casing interior surface, providing full cleaning coverage only when needed.
Solution Approach 2:
The cleaning function is segmented from the main tool body through movable mill blades that can be independently positioned. This segmentation allows the blades to extend outward for cleaning contact while the main tool body maintains a smaller diameter for navigation and completion hardware compatibility.
3Ease of operation
If the drift sub is entirely removed from the well when obstructions are detected, then proper cleaning tool insertion is enabled, but additional round trips are required
Solution Approach 1:
The drift sub and mill blades are merged into a single tool assembly, eliminating the need to remove the drift sub before inserting a separate cleaning tool. The integrated design allows the tool to transition from obstruction detection to cleaning function without tool changes or additional trips.
4Device complexity
If existing cleaning tools are limited to rotation-only operation, then simple design is maintained, but torque-related problems and deviated well coverage are limited
Solution Approach 1:
The mill blades are designed to be movable between retracted and extended positions rather than fixed. This dynamic configuration allows the tool to adapt to different well geometries including deviated and horizontal wells, while maintaining a relatively simple overall design structure.
Data Source
AI summary
In some embodiments, apparatus useful for cleaning at least part of the interior surface of a generally cylindrically-shaped member disposed in a subterranean well includes a housing and a plurality of retractable mill blades supported on the housing and movable from an initial retracted position to an extended position and thereafter to a final retracted position.