Annulus Barrier Plug Segmentation for Well Integrity
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Solution Overview
Problem
Existing methods for establishing annulus barriers in subterranean wells often fail due to poor cement quality, weak formations, and impurities, leading to compromised sealing and increased pressure, necessitating costly re-drilling and re-plugging of both old and new wells.
Innovation Solution
A method involving perforation of the casing to create holes, directional washing to clear debris, and placement of fluidized plugging material to form a cross-sectional plug, followed by drilling out a central portion to maintain a barrier around the casing, ensuring a fluid-tight seal with a connection pipe and plugging material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cement plugging material is used in the annulus, then the barrier plug can be established, but the plug integrity becomes damaged due to weak formations, impurities, and poor cement quality
Solution Approach 1:
The invention changes the physical state and flow characteristics of the plugging material by fluidizing it with air or gas before injection. This transforms the cement from a dense, hard-to-place material into a fluidized slurry that can flow through weak formations and impurities more effectively, then sets into a strong barrier plug after placement
Solution Approach 2:
The invention uses pneumatic fluidization by injecting air or gas through the cement slurry to reduce its density and improve flow properties. This allows the plugging material to be pumped through difficult formations and impurities while maintaining placement integrity, resolving the contradiction between ease of placement and final strength
2Reliability
If the well path is blocked by a barrier plug, then well integrity is protected, but the well path must be re-drilled to access the formation, incurring substantial additional costs
Solution Approach 1:
The invention segments the barrier plug into two distinct parts: a removable central portion that blocks the well path and a permanent annular portion that remains around the casing to provide the barrier function. This segmentation allows the central part to be drilled out later to restore well access while the annular portion maintains well integrity throughout the process
Solution Approach 2:
The invention extracts the central through-going portion of the plug as a separate, removable element. This extracted central portion can be removed by drilling after the annular barrier portion has been established, allowing well path restoration without compromising the permanent annular barrier that protects well integrity
3Reliability
If impurities are present in the annulus, then circulation and adhesion of plugging material are prevented, but the plugging material still needs to be placed to form a barrier
Solution Approach 1:
The invention performs preliminary cleaning of the annulus by circulating washing fluid through the formation before injecting the plugging material. This preliminary action removes impurities that would otherwise prevent proper adhesion of the cement, ensuring the plugging material can bond effectively to the formation and casing
Solution Approach 2:
The invention uses hydraulic circulation of washing fluid to clean the annulus of impurities before plugging material placement. The fluid circulation system removes contaminants that would interfere with cement adhesion, while the subsequent pneumatic fluidization of the cement ensures smooth placement through the cleaned annulus
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 effectively establishes and maintains a reliable annulus barrier, enhancing well integrity and reducing the risk of uncontrolled fluid flows and blowouts, thereby adhering to safety standards and minimizing costly re-drilling operations.
Implementation Method 1
pumping a washing fluid down through the string and out into the casing via the washing tool; conducting the washing fluid out into an annulus between the outside of the casing and a surrounding formation
Implementation Method 2
pumping a fluidized plugging material down through the string and out into the casing, thus also into the annulus via the holes in the casing
Implementation Method 3
Sealing, in a fluid-tight manner, an annulus between the casing and the connection pipe along at least the holes formed in the casing
Data Source
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AI summary
A method for establishment of an annulus barrier (51, 51') in a subterranean well (1) is described, wherein the method is characterized in that it comprises the following steps: (A) providing a plug (25, 25') in the well (1) and along a longitudinal section (LI, LI') thereof, wherein the plug (25, 25'), at least in a portion of the the longitudinal section (LI, LI'), covers substantially the entire cross-section (Tl) of the well (1) in such a manner that the plug covers both the inside and the outside of a casing (21); (B) removing a central through portion of the plug (25, 25') internally in the casing (21) in such a manner that a through central opening is formed in the plug (25, 25'), and in such a manner that at least a cross-sectional section (T3) of the plug (25, 25') remains on the outside of the casing (21); (C) disposing and anchoring a connection pipe (27, 27') in the well (1), and internally in the casing (21), in such a manner that the connection pipe (27, 27') extends at least along a length (L2, L2') of the remaining cross-sectional section (T3); and (D) sealing, in a fluid-tight manner, an annulus (26, 26') between the casing (21) and the connection pipe (27, 27').