Well Abandonment Using In-Situ Scale Precipitation for Permanent Sealing
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Solution Overview
Problem
Existing well abandonment methods using cement as a barrier are insufficient due to potential hydrocarbon leaks through annuli and cracks, and alternative methods like milling the casing are costly and inefficient.
Innovation Solution
A two-component scale formation method using blended scale precursors with a scale inhibitor, forming a stable and insoluble scale like calcium sulphate or carbonate to create a permanent barrier within the well, combined with a third substance to block annular spaces and cracks, and optionally filling the well with cement or concrete for enhanced sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cement is used to plug the well, then the well can be abandoned, but hydrocarbons may escape through annuli and cracks behind casing and through the cement
Solution Approach 1:
The patent uses a composite plugging system combining multiple materials: cement for structural support, scale precursors (calcium chloride and sodium sulphate) that react to form insoluble calcium sulphate scale for sealing, and optionally resin for additional barrier properties. This multi-material approach creates synergistic effects where each material addresses specific failure modes of the others, providing redundant sealing barriers against hydrocarbon leakage through annuli and cracks.
Solution Approach 2:
The patent changes the chemical state of the plugging material by injecting scale precursors that react in-situ to form insoluble calcium sulphate scale. This chemical transformation occurs after injection, changing the physical and chemical parameters of the plugging material to create a more effective seal that is resistant to hydrocarbon penetration, addressing the limitations of conventional cement alone.
2Reliability
If the casing is milled away and the space is filled with cement to create an artificial cap rock, then hydrocarbon leakage is prevented, but the cost increases significantly due to requiring a drilling rig
Solution Approach 1:
The patent extracts the most expensive and complex step from the conventional process by eliminating the need for casing removal and drilling rig operations. Instead, it injects plugging materials through the existing wellbore infrastructure, retaining only the essential function of creating a seal while removing the costly mechanical intervention steps.
Solution Approach 2:
The patent replaces the mechanical system of casing removal and cement filling (requiring drilling rigs) with a chemical injection system. Scale precursors are pumped through the existing wellbore and react in-situ to form sealing scale, substituting complex mechanical operations with simpler chemical processes that achieve the same sealing objective at lower cost.
3Ease of manufacture
If cement is used as a plugging material, then the well can be abandoned, but the cement may fracture and fail over time due to cycles of tension and compression
Solution Approach 1:
The patent applies preliminary action by injecting scale precursors that proactively form insoluble calcium sulphate scale within the cement matrix and annular spaces before any potential fracturing or failure can occur. This pre-formed scale network creates a robust sealing barrier that is resistant to the cyclic tension and compression that would otherwise cause cement failure over time.
Solution Approach 2:
The patent provides beforehand cushioning by creating a distributed network of insoluble calcium sulphate scale throughout the cement and annular spaces. This scale network acts as a reinforcement and cushioning structure that absorbs and distributes stresses from cyclic loading, preventing crack propagation and maintaining seal integrity over the long term.
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 method provides a stable, long-lasting seal that reduces permeability and prevents hydrocarbon leaks, offering a more effective and cost-efficient solution compared to traditional methods by controlling scale formation and using a self-healing barrier to mitigate leaks.
Implementation Method 1
The first and second scale precursors i.e. the first and second solutions containing these materials are blended together prior to being introduced into the reservoir... so they mix just prior to entering the reservoir and are then able to react together to form a scale
Implementation Method 2
forming a stable and insoluble scale like calcium sulphate or carbonate to create a permanent barrier within the well
Data Source
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AI summary
A method of a bandoning a well in a reservoir. The method including the step of forming a scale in the reservoir by introducing into the reservoir a first solution comprising a first scale precursor and a second solution comprising a second scale precursor and a scale inhibitor. The first solution and second solution are able to react together to form the scale. The method further includes the step of at least partially filling the well with cement.