Corrosion-Resistant Casing Shoe for Compressed Air Storage Boreholes
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Solution Overview
Problem
Compressed air storage caverns require borehole completions that can handle high volume flows and withstand increased pressure cycling and corrosion from moist, corrosive air, which existing designs struggle to manage effectively.
Innovation Solution
A borehole completion featuring a standpipe string, an anchor casing string, and a production casing string with a corrosion-resistant stainless steel casing shoe and a glass fiber reinforced polymer insulating pipe socket, isolating the casing shoe from the rest of the string to prevent contact corrosion, and using a protective fluid to seal the annular space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional casing string is used for compressed air storage, then the structure is simple and cost-effective, but the corrosion resistance is insufficient due to exposure to moist compressed air
Solution Approach 1:
The patent applies local quality by using different materials for different sections of the casing string. The casing shoe (lower section exposed to compressed air) is made of corrosion-resistant material, while the upper casing string can be made of conventional steel. This localized material differentiation provides corrosion protection where needed without unnecessarily complicating the entire casing structure.
Solution Approach 2:
The patent employs composite materials by combining corrosion-resistant material with conventional steel in a single casing string assembly. The casing shoe uses corrosion-resistant material while the upper sections use standard steel, creating a composite structure that balances corrosion resistance with structural integrity and cost-effectiveness.
2Productivity
If a larger production casing string is used to handle high volume flows, then the volume flow capacity is improved, but the frictional pressure losses increase
Solution Approach 1:
The patent applies parameter changes by optimizing the inner diameter of the production casing string to balance volume flow capacity with frictional losses. By carefully selecting the diameter parameter, the system achieves sufficient throughput for compressed air storage while minimizing energy losses due to friction.
3Reliability
If the casing shoe is made of corrosion-resistant material, then the reliability under corrosive conditions is improved, but the contact corrosion between different materials increases
Solution Approach 1:
The patent uses an insulating pipe socket as an intermediary element between the corrosion-resistant casing shoe and the conventional steel casing string. This intermediate component electrically isolates the two different materials, preventing galvanic (contact) corrosion while allowing the corrosion-resistant material to protect the critical lower section.
4Reliability
If the insulating pipe socket is used to prevent contact corrosion, then the material compatibility is improved, but the device complexity increases
Solution Approach 1:
The insulating pipe socket serves as a relatively simple intermediary component that effectively prevents contact corrosion between dissimilar materials. While it does add a component to the assembly, its function is straightforward and it can be integrated into existing casing string designs with minimal additional complexity.
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 design enhances corrosion resistance and internal pressure handling, reducing frictional losses and maintaining efficiency under high pressure cycling and corrosive conditions, ensuring reliable operation for compressed air storage caverns.
Implementation Method 1
the casing shoe is connected to the casing string via an insulating pipe socket made of a third material... so that in this way contact corrosion between the casing shoe and the rest of the casing string is reliably avoided
Implementation Method 2
The annular space between the production pipe string and the casing string above the casing shoe is expediently sealed off from the compressed air cavern
Data Source
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AI summary
The invention relates to a borehole completion of a storage borehole (1) of a compressed air cavern, comprising a standpipe assembly (4), an anchor pipe assembly (5), a casing pipe assembly (6) made of a first material, and a delivery pipe assembly (3) extending into the compressed air cavern (2). In the borehole completion according to the invention, the casing pipe assembly (6) comprises, as a casing pipe shoe (10), at least one casing pipe section made of a second corrosion-resistant material, which is different from the first material, at its end leading into the storage borehole (1). The casing pipe shoe (10) is connected to the casing pipe assembly (6) via a pipe socket made of a third material, and the third material is different from the first and second materials.