Self-healing cement sheath with swelling additives
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Solution Overview
Problem
High internal pressure in wellbores causes tensile stress on cement sheaths, leading to damage such as cracking or fracture, especially in high-density cements with low porosity, which can result in undesired hydrocarbon migration and contamination.
Innovation Solution
Incorporating swelling additives like micronized rubber, distillates, and solvent-refined heavy paraffinics into cement slurries to increase tensile strength and self-healing capabilities, allowing the additives to migrate into cracks and expand upon exposure to hydrocarbons, thereby sealing damage and preventing further migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high density cement materials are used to reduce voids and hydrocarbon migration, then the cement structure becomes more brittle and susceptible to damage under pressure
Solution Approach 1:
The patent introduces microcapsules with hollow interiors containing swelling agents into the cement matrix. These microcapsules create controlled porosity that allows the cement to absorb tensile stress through capsule deformation and rupture, preventing catastrophic failure while maintaining overall structural integrity and preventing hydrocarbon migration.
Solution Approach 2:
The patent creates a composite cement material by incorporating microcapsules containing swelling agents (such as water, alcohol, or hydrocarbons) into the cement matrix. This composite structure combines the strength of high-density cement with the damage-mitigating properties of the embedded microcapsules, resolving the contradiction between density and brittleness.
2Reliability
If cement sheath is subjected to high internal pressure, then tensile stress causes cracking or fracture leading to leaking
Solution Approach 1:
The patent embeds microcapsules containing swelling agents throughout the cement matrix before the cement is subjected to pressure. When tensile stress develops, these pre-positioned microcapsules rupture and release swelling agents that fill crack spaces, providing cushioning that prevents crack propagation and maintains sheath integrity.
Solution Approach 2:
The patent converts the harmful effect of tensile stress-induced cracking into a beneficial self-healing mechanism. The swelling agents contained in microcapsules are released specifically when cracks form, and their expansion fills the crack spaces, transforming the damage event into an opportunity for automatic repair and leak prevention.
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 swelling additives enhance the tensile strength of cement materials, reduce the likelihood of damage from internal pressure, and prevent hydrocarbon migration, improving the durability and integrity of cement sheaths in wellbores.
Implementation Method 1
The presently described swelling additives address these needs by migrating into cracks or fractures formed in a cement sheath by swelling, or increasing in size or volume, upon exposure to hydrocarbons in either their gaseous or liquid form.
Implementation Method 2
The swelling additive comprises at least one micronized rubber, at least one distillate, and at least one solvent-refined heavy paraffinic.
Data Source
AI summary
According to at least one embodiment of the present description, a cement slurry includes 1% to 90% BWOC of a cement precursor material based on the total weight of the cement slurry; and from 1% to 40% BWOC of a swelling additive based on the total weight of the cement slurry. The swelling additive comprises at least one micronized rubber, at least one distillate, and at least one solvent-refined heavy paraffinic.