Degradable Polymer Coatings for Fracturing Proppant
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Solution Overview
Problem
Conventional fracking techniques face issues such as material deficiencies, rheology limitations, and environmental concerns in hydraulic-based recovery systems, particularly in low permeability subsurface formations, which hinder economical extraction of hydrocarbons.
Innovation Solution
A degradable polymer composition that remains solid under dry conditions but depolymerizes into a viscous liquid when exposed to water, allowing for hydraulic fracturing and subsequent breakdown into water-soluble components, enhancing formation permeability and facilitating hydrocarbon extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fracking materials are used, then hydraulic fracturing can be performed, but material deficiencies and rheology limitations occur that hinder effective treatment of low permeability formations
Solution Approach 1:
The patent applies parameter changes by utilizing the temperature-dependent solubility characteristics of polymers in supercritical CO2. The polymer is selected to be substantially insoluble at reservoir temperature (maintaining solid proppant coating) but soluble at surface temperature (enabling disposal). This parameter change resolves the contradiction by making the same material suitable for both low permeability formation treatment and easy disposal, while maintaining fracturing effectiveness throughout the process
Solution Approach 2:
The patent employs composite materials by combining polymer coatings with proppant particles. The polymer-proppant composite provides both the mechanical support needed for fracturing effectiveness and the temperature-responsive solubility characteristics. This composite structure enables the material to function effectively in low permeability formations while remaining dispensable, thus resolving the adaptability contradiction
2Reliability
If solid proppant is used to maintain fracture openness, then fracture conductivity is improved, but proppant disposal becomes difficult and costly
Solution Approach 1:
The patent utilizes parameter changes in polymer solubility with temperature. At reservoir temperature, the polymer is insoluble and maintains solid proppant characteristics for fracture conductivity. At surface temperature, the polymer becomes soluble and can be easily disposed of by flushing with CO2. This resolves the contradiction between maintaining fracture conductivity and enabling easy disposal
Solution Approach 2:
The patent applies the disposable principle by using polymer-coated proppant that is designed to be temporary. The polymer coating provides necessary fracture conductivity during production, then becomes soluble and removable via CO2 flushing. This replaces permanent proppant with a disposable alternative, resolving the disposal difficulty while maintaining fracture conductivity during the needed period
3Productivity
If polymer viscosity is increased to improve fluid carrying capacity, then proppant transport capability improves, but fluid rheology becomes more difficult to control
Solution Approach 1:
The patent extracts the viscosity-control function from the bulk fracturing fluid and places it solely on the polymer-coated proppant particles. The polymer coating provides the necessary viscosity and carrying capacity at the particle level, while the bulk fluid maintains simple, easily controlled rheology. This separation resolves the contradiction between proppant transport capability and fluid rheology control complexity
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 degradable polymer composition effectively increases formation permeability, enabling efficient hydrocarbon extraction by transforming into a viscous, pumpable form that can be used for fracturing and subsequently breaks down into environmentally benign components, reducing equipment costs and environmental impact.
Implementation Method 1
the polymer chains are slowly 'degrading' due primarily to hydrolytic action, referred to at times herein as 'depolymerization,' which eventually manifests qualitatively as an observable transition of the polymeric material from an essentially solid form to a less and less 'solid' state, then ultimately to dissolved or dispersed state
Data Source
AI summary
The present disclosure is directed degradable polymers. The polymers are solid when maintained under substantially dry conditions at a temperature of up to about 90 degrees C. When contacted with water at a temperature of up to about 90 degrees C, however, the polymers initially remain solid for a period of up to about 6 to about 24 hours, then depolymerize to provide a liquid having a viscosity of from about 1 to about 200,000 centipoise after a period of time from about 8 hours to about 3 days and then further depolymerizes to water-soluble components after a period of time at least about 3 days. Also disclosed are sand screen coatings made with the polymers and hydraulic and acid fracturing methods using the polymers.