Wireline Milling Tool for Casing Window Notch
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Solution Overview
Problem
The existing methods for milling a window in the casing of an oil or gas well, particularly for sidetracking, are challenging due to the difficulty in initial phase operations, especially with high-grade casings like Q-125, and the lack of a viable system for wireline milling.
Innovation Solution
A two-stage process is introduced, where a wireline milling tool is used to establish a small ledge or notch in the casing, followed by a coiled tubing or jointed drill pipe operation to complete the window milling, thereby reducing the initial risk and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If wireline milling tool is used to mill a window in casing, then equipment mobilization time and cost are reduced, but the tool requires gripping apparatus and stroking mechanism which complicates the device and creates debris management issues
Solution Approach 1:
The milling operation is divided into two distinct phases: an initial phase using a wireline milling tool with gripping apparatus to create a small opening, and a completion phase using coiled tubing or drill pipe to mill the full window. This segmentation allows the complex wireline tool to perform only the initial breakthrough function, reducing the overall system complexity requirements.
Solution Approach 2:
The wireline milling tool performs preliminary action by creating a small opening or notch in the casing before the main milling operation. This preliminary opening eases subsequent access for coiled tubing or drill pipe, reducing the complexity of the gripping and stroking mechanisms needed for the complete operation.
2Productivity
If wireline milling tool mills a full 4 to 6 feet window, then the complete window is created in one operation, but the stroking length must be very long and the tubing strength is significantly impaired
Solution Approach 1:
The window milling operation is segmented into an initial opening phase (creating a small notch) and a completion phase (milling the full 4-6 foot window). The wireline tool performs only the initial phase, requiring minimal stroking length and preserving tubing strength, while the second phase is performed when the window is already partially open.
Solution Approach 2:
The wireline milling tool performs partial action by creating only a small opening or notch rather than the complete window. This partial action is sufficient to enable subsequent access for coiled tubing or drill pipe, avoiding the need for the wireline tool to perform the full milling operation which would require excessive stroking length.
3Device complexity
If wireline milling is used, then fluid circulation for debris removal is not possible, but the initial risky phase can be completed with less equipment
Solution Approach 1:
The milling operation is segmented so that the wireline tool handles only the initial opening phase where debris generation is minimal, and the coiled tubing or drill pipe handles the main milling phase where fluid circulation can effectively remove debris. This segmentation matches the debris management capability with the operation phase.
Solution Approach 2:
The small opening or notch created by the wireline tool acts as an intermediary that enables subsequent access for coiled tubing or drill pipe. This intermediary opening allows the transition from a system without fluid circulation capability to a system with fluid circulation capability for effective debris removal.
Data Source
AI summary
A process is described for milling a window in the casing (2) of an oil or gas producing well, for example in order to drill a lateral well branching off from the main well. A wireline milling tool is first used, in a relatively low cost operation, to create a small window (14) or notch in the casing (2). Provided a small window (14) or notch can be created successfully, an expensive heavy duty coil tubing milling operation can then be conducted to create the full window, some 4-6 feet in length. Previous attempts to create a full window using wireline tools have encountered difficulties due to there being no circulating drilling fluid to remove metal swarf and due to the need for the tool to be supported by casing during the milling operation, when the integrity of the casing is being compromised by drilling the window. The proposed wireline tool has an actuator (4) with relatively small stroke length and a relatively small container (8) to manage the swarf produced by the milling process.