Perforated Casing Recovery Through Partial Annulus Washing
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Solution Overview
Problem
Existing methods for removing casing from wells are time-consuming and inefficient due to the need for multiple trips into the well to cut and pull casing sections, often hindered by debris in the annulus, and lack effective well control during cutting.
Innovation Solution
A method involving determining a casing cutting target depth, cutting the casing, perforating along a section, washing the annulus with fluid through perforations to clear debris, gripping the casing, and pulling it out, optionally using a downhole power tool to exert greater forces, and a bottomhole assembly with integrated tools for perforating, washing, and gripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple trips into the well are made to cut and pull casing sections, then complete casing removal is achieved, but operation time and cost increase significantly
Solution Approach 1:
The patent combines multiple casing removal operations (cutting, washing, and pulling) into a single integrated tool assembly that can perform all functions during one trip into the well. The tool string integrates a cutting tool, washing tool with fluid injection capability, and pulling mechanism with spear engagement, eliminating the need for multiple separate trips and significantly reducing operation time while maintaining complete casing removal effectiveness.
Solution Approach 2:
The tool assembly is designed as a multi-functional device that can cut casing at different depths, wash debris from the annulus using fluid injection through ports, and pull casing sections simultaneously or in sequence during a single operation. This universal tool replaces multiple specialized tools and operations, achieving complete casing removal in one trip.
2Loss of time
If the casing is pulled without washing out debris in the annulus, then operation time is reduced, but the casing becomes stuck and cannot be pulled
Solution Approach 1:
The washing function is performed preliminarily before the pulling operation within the same trip. The tool assembly injects fluid through ports into the annulus to wash out debris and cement before the casing is pulled, ensuring the casing can be freely pulled without sticking while minimizing total operation time by combining both actions in one sequence.
Solution Approach 2:
The washing and pulling operations are merged into a single continuous operation using the same tool assembly. The washing tool and pulling mechanism are integrated, allowing fluid injection to clear debris followed immediately by casing engagement and pullout without requiring separate trips or operations.
3Reliability
If short sections of casing are washed and pulled on each trip, then the washing process can be completed, but the total time to remove the entire casing section increases very long
Solution Approach 1:
The tool assembly can cut the casing into multiple sections at different depths during a single trip, with each section then being washed and pulled in sequence or simultaneously. This segmentation allows the washing function to be applied to multiple casing sections without requiring multiple trips, as all cutting, washing, and pulling operations are performed during one intervention.
Solution Approach 2:
The tool assembly maintains continuous useful action by performing cutting, washing, and pulling operations in an uninterrupted sequence during a single trip. The fluid injection system continuously washes debris while the pulling mechanism continuously engages and extracts casing sections, maximizing productivity and minimizing total removal time while ensuring complete washing of all casing sections.
4Loss of time
If cutting and pulling tools are combined for single trip operation, then time and cost are reduced, but debris in the annulus prevents the casing from being pulled
Solution Approach 1:
The tool assembly introduces fluid as an intermediary substance to wash out debris from the annulus before casing pulling. The washing tool injects fluid through ports into the annulus, using the fluid as a mediator to remove harmful debris and cement that would otherwise prevent successful casing extraction, enabling the combined cutting and pulling operation to succeed in a single trip.
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
This method significantly reduces the time required to remove casing by allowing partial washing and pulling on a single trip, utilizing a downhole power tool to apply higher forces, thus overcoming the limitations of prior art techniques.
Implementation Method 1
passing a fluid at high pressure through the string and into the annulus via the perforations so that the viscous and/or solid mass is displaced up the annulus, circulated out of the well
Implementation Method 2
forming perforations into the casing with said cutting tool at a second depth in the well
Implementation Method 3
setting a first sealing element into fluid-sealing engagement with the inside of the casing at a first depth in the well
Data Source
AI summary
Method of removing casing from a well, in which an annulus between the outside of the casing and the inside of a surrounding downhole body is at least partially filled by debris, the perforated section of casing is washed in casing lengths shorter than the perforation length and an attempt made to pull the casing after each shorter length is washed. If the casing is free after washing only a shorter section of the perforated section of casing then it can be recovered and saves the washing time. A bottom hole assembly is described which includes a downhole power tool to exert a greater force to pull the section of casing between washing steps.