Electromagnetic Underreamer Actuating Cutter Blocks for Rat Hole Enlargement
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Solution Overview
Problem
Existing underreamers are unable to increase the diameter of the lower portion of the wellbore, known as the 'rat hole,' due to the drill bit contacting the subterranean formation, preventing further downward movement and limiting the enlargement of this section.
Innovation Solution
An underreamer system equipped with an electromagnetic activation system, a valve, and movable cutter blocks that transition from an inactive to an active state upon signal reception, allowing radial outward movement to enlarge the wellbore diameter, even in areas where the drill bit is in contact with the formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drill bit contacts the subterranean formation at the base of the wellbore, then the drilling process is completed, but the underreamer cannot move further downward to enlarge the lower portion (rat hole) of the wellbore
Solution Approach 1:
The wellbore enlargement operation is segmented into two distinct phases: first, the drill bit drills the wellbore to the desired depth; second, the underreamer is actuated to enlarge specific portions including the rat hole. This segmentation allows the underreamer to be positioned and actuated independently after drilling is complete, enabling enlargement of the lower portion without requiring the drill bit to be pulled out or the wellbore to be re-drilled.
Solution Approach 2:
The drill bit performs the preliminary action of drilling the wellbore to the required depth, creating the initial hole structure. After this preliminary drilling is complete, the underreamer is then actuated to perform the enlargement action on the rat hole section. The preliminary drilling creates the access pathway that allows the underreamer to subsequently enlarge the lower portion of the wellbore.
2Productivity
If the underreamer is positioned above the drill bit by 30-60 meters, then the underreamer can be actuated to enlarge the wellbore diameter, but the lower portion (rat hole) remains at pilot hole diameter because the drill bit prevents further downward movement
Solution Approach 1:
The wellbore is segmented into different diameter zones: the upper portion enlarged by the underreamer and the lower rat hole section at pilot hole diameter. The underreamer is designed with cutter blocks that can be actuated to enlarge the wellbore diameter in the upper portion, while the drill bit remains in place to maintain the smaller diameter in the lower portion, creating a segmented diameter structure that satisfies both enlargement requirements and structural integrity.
Solution Approach 2:
Different portions of the wellbore are given different diameters based on local requirements: the upper portion is enlarged to a larger diameter for production or access purposes, while the lower rat hole section maintains the original pilot hole diameter for structural stability and to prevent collapse. This local differentiation of wellbore diameter allows each section to optimize for its specific function.
3Ease of operation
If the cutter blocks are folded or retracted inwardly into the underreamer body, then the underreamer can be transported through the wellbore, but the cutter blocks cannot contact the wellbore wall to increase diameter
Solution Approach 1:
The cutter blocks are designed with dynamic positioning capability, allowing them to transition between a retracted state during transport and an extended state during operation. The cutter blocks can be moved radially outward from the underreamer body to contact the wellbore wall and perform enlargement, then retracted inwardly for transport through the wellbore. This dynamic repositioning enables the underreamer to perform both transport and enlargement functions.
Solution Approach 2:
The underreamer operation involves periodic cycles of retraction and extension of the cutter blocks: during transport, the cutter blocks are retracted inwardly; upon reaching the target depth, they are extended outwardly to enlarge the wellbore; after enlargement is complete, they are retracted again for withdrawal. This periodic action of retracting and extending allows the underreamer to efficiently perform wellbore enlargement while maintaining transportability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables effective enlargement of the wellbore diameter, including the previously inaccessible 'rat hole' section, by actuating the cutter blocks to expand the wellbore radius even when the drill bit is at the base, thereby increasing the wellbore's diameter efficiently.
Implementation Method 1
An electromagnetic activation system (e.g., a motor) may be disposed at least partially within the bore of the body
Data Source
AI summary
An underreamer for increasing a diameter of a wellbore. The underreamer may include a body having an axial bore extending at least partially therethrough. An electromagnetic activation system may be disposed at least partially within the bore of the body. A valve may be disposed within the bore of the body and coupled to the electromagnetic activation system. The valve may include a mobile element and a static element. The mobile element may be coupled to the electromagnetic activation system and move from a first position where the mobile element obstructs fluid flow through the valve to a second position where the mobile element permits fluid flow through the valve. A cutter block may be movably coupled to the body and move radially-outward as the mobile element moves from the first position to the second position.