Retrofit Pressure Vessel for Gas Well Casing Sealing
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Solution Overview
Problem
Uncontrolled gas leaks from annular gaps between surface and production casings in oil and gas wells pose significant environmental and safety risks, with existing solutions being either unsafe or prohibitively costly, especially for non-commercially producing wells.
Innovation Solution
An elongate pressure vessel composed of mating shell portions with flanges and seals is assembled around the intersection of surface and production casings to form a sealed cavity, allowing controlled venting of accumulated annular gas, using TEADIT 24B PTFE joint-sealant tape for sealing and fasteners for assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If welding steel plates onto the surface casing stub is used to seal the annular gap, then sealing effectiveness is improved, but safety risks increase due to potential burning holes in the production casing and uncontrolled gas escape
Solution Approach 1:
The patent introduces a specialized sealing device that acts as an intermediary between the surface casing and production casing. This device includes a sealing element with a radial seal that engages the production casing and an axial seal that engages the surface casing, creating a barrier without direct welding to the production casing. The sealing element is installed in a sealing assembly that can be attached to the surface casing stub, providing the necessary seal while eliminating the safety risks of welding near the production casing.
2Ease of operation
If suspending production and installing a surface casing spool with vent is used, then gas venting capability is improved, but cost increases to $25,000 to $35,000 per well
Solution Approach 1:
The patent divides the sealing and venting function into separate modular components. The sealing assembly includes a sealing element with distinct radial and axial seal portions, while the venting function is provided by a separate vent cap that can be attached to the sealing assembly. This segmentation allows for a more cost-effective solution compared to installing an entire surface casing spool, as only the necessary sealing and venting components are installed rather than complete casing replacement.
Solution Approach 2:
The patent employs a cost-effective sealing assembly that can be installed without the need for expensive surface casing spool installation. The sealing element and associated components are designed to provide the necessary function at a fraction of the cost of traditional methods, making them suitable for wells that are no longer producing on a commercial scale where high installation costs are prohibitive.
3Adaptability or versatility
If not all production casings are centered in the surface casing, then adaptability of sealing solutions is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates adjustable elements in the sealing assembly that allow it to adapt to varying casing centering conditions. The sealing element can be positioned and adjusted to engage both the surface casing and production casing effectively, regardless of whether the production casing is perfectly centered. This dynamic adjustability enables the sealing solution to work with casings that have不同程度的 centering alignment.
4Ease of manufacture
If inadequate cementation is used in the annulus, then ease of installation is improved, but gas migration control deteriorates leading to sustained casing pressure
Solution Approach 1:
The patent extracts the gas migration control function from the cementation process and provides it through a mechanical sealing system. The sealing element with its radial and axial seals creates a physical barrier that prevents gas migration without relying on cement quality. This allows the annulus to remain uncemented or partially cemented while still achieving effective gas control through the mechanical seals of the sealing assembly.
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
The solution effectively prevents uncontrolled gas escape and allows for safe, cost-effective management of annular gas, reducing sustained casing pressure and environmental impact by creating a sealed cavity for gas collection and controlled venting.
Implementation Method 1
using TEADIT 24B PTFE joint-sealant tape for sealing
Data Source
AI summary
Disclosed apparatus and methods permit well-site operators to retrofit existing wells in order to comply with local regulations that restrict the escape of annular natural gas from hydrocarbon wells. Such allows sealing around an exterior of surface and concentric production casings, both above and below the point of their intersection, then assembling a pressure vessel around that point and between those seals so as to capture and hold gas rising up an intercasing annulus, for periodic controlled venting.