Expandable Tubulars for Gas-Tight Casing Sealing
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Solution Overview
Problem
Existing wellbore operations face challenges in maintaining gas-tight seals between production casings, particularly during gas-lift operations, due to deteriorated thread connections and leaks in the casing-casing annuli, which can compromise well integrity and reduce hydrocarbon production efficiency.
Innovation Solution
The use of expandable tubulars that can be hydraulically or mechanically expanded to form a metal-to-metal gas-tight seal with the production casing, eliminating the need for cement and allowing for a larger wellbore diameter, thus preventing gas leakage and maintaining well integrity by overlaying the old casing with a fresh layer of tubulars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement is used to seal the annulus between production casings, then gas-tight sealing is achieved, but the wellbore diameter is reduced and the process becomes more complex
Solution Approach 1:
The invention extracts and eliminates the cementing process entirely from the sealing system. Instead of using cement to seal the annulus between production casings, the system uses expandable tubulars that can be mechanically or hydraulically expanded to form a metal-to-metal seal, thereby removing the harmful complexity of cementing operations while maintaining gas-tight sealing reliability
Solution Approach 2:
The invention replaces the chemical/mechanical cementing system with a purely mechanical expansion system. The expandable tubulars are inserted in the unexpanded state, then expanded using hydraulic or mechanical forces to contact and seal against the production casing inner wall, substituting the cement bonding mechanism with a controlled mechanical expansion and contact mechanism
2Reliability
If a new production casing is installed to replace deteriorated connections, then gas-tight integrity is restored, but the wellbore diameter is reduced requiring a smaller casing
Solution Approach 1:
The invention applies dynamics by using an expandable tubular system that transitions from a compact unexpanded state during insertion to a fully expanded state for sealing. This dynamic transformation allows the system to access the full wellbore diameter during installation, then expand to contact the production casing for sealing, thereby maintaining maximum wellbore diameter while achieving gas-tight integrity
Solution Approach 2:
The expandable tubular is inserted in a collapsed or unexpanded state within the production casing, similar to a nested doll structure. Once positioned, it expands outward to contact the production casing inner wall, maintaining the nesting concept while achieving full radial contact for sealing without reducing the original wellbore diameter
3Ease of manufacture
If thread connections are used to join production casings, then assembly is simplified, but gas leakage occurs due to deterioration over time
Solution Approach 1:
The invention extracts and removes the thread connection interface from the gas-tight sealing path. By using expandable tubulars that seal against the production casing inner wall, the system eliminates the reliance on thread connections for gas-tight integrity, thereby removing the source of leakage while maintaining assembly simplicity through the expansion mechanism
Solution Approach 2:
The expandable tubular acts as an intermediary sealing element between the new production casing and the existing production casing. Instead of relying on the thread connections of either casing, the expandable tubular creates a new sealing interface that mediates the gas-tight connection, isolating the system from the deteriorated thread connection vulnerabilities
4Productivity
If gas lift operation is performed to increase hydrocarbon production, then production efficiency improves, but gas leakage into the annulus reduces efficiency and compromises well integrity
Solution Approach 1:
The invention converts the potential harm of gas leakage into a benefit by creating a sealed environment that directs all injected gas into the production string. The expandable tubular sealing system transforms the annulus from a potential leakage path into a controlled isolation zone, ensuring that gas lift operations benefit fully from the injected gas without loss to the annulus, thereby maximizing production efficiency while maintaining well integrity
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 solution ensures a gas-tight system for gas-lift operations, maintains well integrity by sealing non-gas-tight connections, and allows for the same production volumes and flow rates as the original method, while avoiding the need for cementing a new smaller casing, thus ensuring efficient hydrocarbon production.
Implementation Method 1
The expandable tubular can be expanded, such as hydraulically or mechanically
Implementation Method 2
The expandable tubular can be expanded, such as hydraulically or mechanically
Implementation Method 3
an outer surface of the expanded tubular forms a metal-to-metal, gas-tight seal against an inner surface of the production casing
Data Source
AI summary
A production well has nested casings including a first production casing and a first production tubing installed within the first production casing, which extends from a surface to a depth within the wellbore. Before implementing a gas-lift operation in the production well, the first production tubing is removed. A second production casing is lowered within the first production casing. The second production casing has a smaller outer diameter than an inner diameter of the first production casing. From the surface of the wellbore to the depth within the wellbore to which the second production casing extends, the inner diameter of the second production casing is expanded until an outer wall of the second production casing forms a gas-tight seal with an inner wall of the first production casing.