Inducing Annulus Seal via Overburden Creep
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Solution Overview
Problem
The existing methods for plugging and abandoning hydrocarbon wells are costly and time-consuming due to the inefficiency of natural formation creep in creating an effective seal between the steel casing and the surrounding rock, often requiring expensive and complex procedures to inject cement or other materials into the annulus.
Innovation Solution
The process involves reducing the pressure in the annulus to induce creep by using underbalanced drilling techniques, either through casing valve outlets or perforations, and applying cyclic pressure or mechanical stress to promote fatigue in the formation, allowing for the formation of a natural seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement is pumped into the annular space to seal it off, then the seal effectiveness is improved, but the cost and time required for the operation increase
Solution Approach 1:
The patent applies preliminary action by reducing annulus pressure before the well abandonment to induce formation creep and create a natural seal. This pre-conditioning of the formation eliminates the need for subsequent cement pumping operations, thereby reducing both time and material costs while maintaining seal effectiveness.
2Reliability
If cement is pumped into the annular space to seal it off, then the seal effectiveness is improved, but the complexity of the operation increases
Solution Approach 1:
The patent employs self-service by utilizing the formation's natural creep properties to create the seal. By reducing annulus pressure, the formation automatically creeps and seals the annulus without requiring external cement injection equipment or complex operational procedures, thereby simplifying the abandonment process.
3Ease of operation
If casing is milled away to expose the formation, then access to the annulus is improved, but the cost and time required increase
Solution Approach 1:
The patent applies preliminary action by reducing annulus pressure early in the process to induce formation creep. This creates a natural seal that eliminates the need for subsequent casing milling operations to access the annulus, thereby saving significant time and reducing operational complexity.
4Ease of manufacture
If pressure is reduced in the annulus to induce creep, then the need for cementing is reduced, but special surface equipment is required
Solution Approach 1:
The patent applies parameter changes by modifying the pressure parameter in the annulus to induce formation creep. By reducing annulus pressure below formation pressure, the formation naturally creeps and seals the annulus, eliminating the need for cementing operations and simplifying the overall process despite requiring pressure control equipment.
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 induces creep in the overburden formation, potentially creating a reliable seal without the need for extensive cementing or milling, thereby simplifying and cost-reducing the plug and abandon process.
Implementation Method 1
it is believed that the formation rock in the overburden creeps after the casing is installed, possibly forming an effective natural seal between the overburden formation and the casing
Implementation Method 2
applying cyclic pressure or mechanical stress to promote fatigue in the formation, allowing for the formation of a natural seal
Data Source
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AI summary
The invention relates to the decommissioning of hydrocarbon wells. It concerns the artificial promoting or inducing of creep in the overburden formation 3 surrounding an oil well 1, so that the formation rock 3 encroaches against the casing 5 to form a seal. This avoids the need to plug the annulus between the casing 5 and formation 3 with cement. The overburden may be caused to creep by reducing the pressure in the annulus, by applying heat to the overburden rock or by stressing the rock repeatedly to cause fatigue in the rock 3.