Annular Isolation via Perforated Casing Cement Flow
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Solution Overview
Problem
Existing methods for isolating annular areas behind multiple casings in subterranean wells are impractical and inefficient, particularly when multiple casings and annuli are involved, as they often require milling through casings, which is time-consuming and costly.
Innovation Solution
A method involving the isolation of an innermost annulus followed by the isolation of an outer annulus by flowing cement radially through the inner annulus, using perforating guns to create perforations and flushing tools to clear debris, allowing for efficient sealing without the need for milling through casings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional milling through casing is used to access annulus, then annulus can be accessed, but operational complexity and time increase significantly
Solution Approach 1:
The invention extracts the cement sheath from the annulus by dissolving it with acid, removing the barrier that traditionally required mechanical milling. This allows direct access to the annulus through chemical dissolution rather than mechanical removal, significantly reducing operational complexity and time.
Solution Approach 2:
The invention replaces the mechanical milling system with a chemical dissolution system. Instead of using mechanical cutters to remove the cement sheath, the method uses acid to chemically dissolve the cement, providing a non-mechanical approach to accessing the annulus that reduces equipment complexity and operational time.
2Reliability
If multiple casings and annuli are involved, then complete isolation is achieved, but process complexity increases
Solution Approach 1:
The invention segments the wellbore into discrete isolation zones by placing cement plugs at specific intervals and dissolving the cement sheath only in targeted annular sections. This allows each annulus to be isolated independently through a systematic process, achieving complete isolation across multiple casings while managing complexity through structured segmentation.
Solution Approach 2:
The invention uses acid as an intermediary substance to selectively dissolve the cement sheath in targeted zones. This intermediary chemical agent enables precise control over which annuli are accessed and which remain sealed, facilitating complex multi-annulus isolation scenarios through controlled chemical interaction rather than mechanical intervention.
3Ease of operation
If cement sheath is removed by milling, then annulus is accessed, but operational costs increase
Solution Approach 1:
The invention replaces expensive mechanical milling operations with a chemical dissolution process using acid. This substitution eliminates the need for specialized milling equipment, reduces operational costs, and provides a more economical method for accessing the annulus while maintaining ease of operation.
Solution Approach 2:
The invention changes the physical-chemical parameters of the cement sheath by exposing it to acid, transforming it from a solid barrier into a dissolved state. This parameter change enables annulus access without the high costs associated with mechanical milling, providing a cost-effective alternative that maintains operational effectiveness.
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 allows for convenient and economical isolation of annular areas, reducing operational complexity and costs by enabling fluid communication and cement flow between casings, thereby effectively sealing off annuli without the need for extensive casing milling.
Implementation Method 1
perforating guns to create perforations
Implementation Method 2
flowing cement radially through the inner annulus to the outer annulus
Data Source
AI summary
A method of isolating annular areas formed by multiple well casings can include providing fluid communication through a wall of one of the casings at a location where another one of the casings outwardly surrounds the first casing, then flowing a cement into an annulus formed radially between the first and second casings, then providing fluid communication through the wall of the first casing and a wall of the second casing, and then flowing another cement into another annulus external to the second casing. A method of abandoning a well can include perforating a casing at a location where another casing outwardly surrounds the first casing, flowing a cement into an annulus formed radially between the first and second casings, the cement including a tracer, perforating the first and second casings, and flowing another cement into another annulus external to the second casing, the second cement including a second tracer.