Non-aqueous Solvent Filter Cake Removal
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Solution Overview
Problem
Existing methods for removing water-based filter cake from wellbores using aqueous solvents often result in localized reactions that create holes, leading to incomplete removal and inhibition of fluid flow during production, as the breaker fluid leaks off into the formation before fully breaking down the filter cake.
Innovation Solution
A method involving a non-aqueous, polar solvent mixture with a breaker agent, where the solvent has a dielectric constant greater than 15, and typically comprises less than 5 wt% water, slows the reaction rate to ensure more even breakdown of the filter cake, using potassium EDTA and optional oxidizers or enzymes to target polymers and calcium carbonate, thereby minimizing loss through the filter cake.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If an aqueous solution of sodium-EDTA is used to remove filter cake, then the calcium carbonate in the filter cake is removed, but the reaction is localized and creates holes through which the breaker fluid leaks off into the formation, leaving much of the filter cake intact
Solution Approach 1:
The patent changes the solvent parameter from aqueous to non-aqueous (using solvents like glycols, esters, or hydrocarbons with specific properties). This parameter change slows the reaction rate between the breaker fluid and filter cake, allowing more uniform penetration and reaction throughout the filter cake rather than localized rapid reaction that creates holes and leakage paths.
Solution Approach 2:
The patent makes the reaction rate dynamic by controlling it through solvent selection. The non-aqueous solvent creates a controlled, slower reaction that progresses uniformly through the filter cake, transforming the static rapid reaction of aqueous solutions into a dynamic, controllable process that maintains fluid integrity throughout treatment.
2Productivity
If the reaction rate of the breaker fluid with the filter cake is increased, then the filter cake breakdown is faster, but the breaker fluid leaks off into the formation before fully breaking down the filter cake
Solution Approach 1:
The patent changes the reaction kinetics parameter by selecting non-aqueous solvents that inherently slow the reaction rate between the breaker fluid and filter cake components. This parameter adjustment allows the breaker fluid to penetrate deeper into the formation and react more completely with the filter cake before leaking off, improving overall treatment effectiveness.
Solution Approach 2:
The non-aqueous solvent acts as an intermediary medium that mediates the reaction between the breaker fluid and filter cake. It controls the interaction by providing a reaction environment that slows the rate of reaction, allowing more complete breakdown while preventing premature leakage into the formation.
3Manufacturing precision
If a non-aqueous, polar solvent is used to slow the reaction rate, then the breaker fluid penetrates more evenly through the filter cake, but the solvent must have specific properties (dielectric constant >15, oil-soluble)
Solution Approach 1:
The patent specifies particular parameter ranges for the non-aqueous solvent (dielectric constant between 15-40, specific solubility characteristics) to achieve the desired reaction rate and penetration uniformity. These parameter specifications ensure consistent, controlled breakdown of the filter cake while maintaining practical applicability in wellbore environments.
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 approach allows for a more controlled and complete breakdown of the filter cake, reducing the risk of premature leakage and ensuring better fluid flow by maintaining the breaker fluid's activity as it penetrates the filter cake and formation, with the non-aqueous solvent reducing hydration and gelatinous polymer barriers.
Implementation Method 1
The use of such non-aqueous, polar solvents slows the reaction rate of the agent with the filter cake
Implementation Method 2
with the non-aqueous solvent reducing hydration and gelatinous polymer barriers
Implementation Method 3
an agent selected to breakdown the filter cake
Data Source
AI summary
A method of removing a water-based filter cake from a wellbore, the method comprising: contacting the filter cake with a mixture comprising: a non-aqueous, polar solvent; an agent selected to breakdown the filter cake; said mixture comprising <5 wt % water and preferably being essentially anhydrous. The low water content of the mixture actually slows the degradation of the filter cake which has surprisingly been found to be more effective as it allows a more even removal of the filter cake and a more efficient use of the mixture; without the tendency to create local holes in the filter cake where the mixture could escape. Embodiments of the present invention use a polar solvent with a dielectric constant of more than (15), preferably more than (30) such as (15) monoethylene glycol (MEG). In preferred embodiments the agent comprises a salt based on potassium EDTA (ethylenediaminetetraacetic acid).