Star Macromolecule Thickening Agents for Hydraulic Fracturing Fluids
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Solution Overview
Problem
Current hydraulic fracturing fluids face challenges in maintaining fracture width and proppant stability, especially at higher depths, due to high pressures and stresses, which affect the efficiency of oil and gas extraction.
Innovation Solution
A polymer composition comprising star macromolecules with a core and multiple arms, where the arms are covalently attached and exhibit different solubility, is used to thicken hydraulic fracturing fluids, providing a dual mechanism for thickening via self-assembly and crosslinking with borate-type additives, enhancing viscosity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional thickening agents are used in hydraulic fracturing fluids, then the fluid can be pumped and injected, but the viscosity is insufficient to maintain fracture width and proppant stability under high pressure and stress conditions
Solution Approach 1:
The patent employs star macromolecules with multiple arms that can simultaneously perform thickening, crosslinking, and proppant stabilization functions. These composite polymeric structures combine multiple functional capabilities in a single material system, enabling the fluid to maintain adequate viscosity and fracture width under high downhole pressures where conventional single-function additives fail
Solution Approach 2:
The star macromolecules exhibit variable viscosity characteristics that change in response to pressure and stress conditions. The polymeric structure undergoes conformational changes and crosslinking reactions that increase viscosity under high pressure, allowing the fluid to adapt its rheological properties to maintain fracture width and proppant stability in high-stress downhole environments
2Strength
If high viscosity fracturing fluids are used to maintain fracture width, then proppant transport and retention improve, but the fluid requires more energy to pump and inject
Solution Approach 1:
The star macromolecule-based fracturing fluid exhibits dynamic rheological properties where viscosity is not fixed but responds to flow conditions and stress. The fluid maintains lower viscosity during high-speed pumping to reduce energy requirements, then increases viscosity under static or low-flow conditions to improve proppant retention and fracture width maintenance, creating a dynamic balance between pumpability and proppant support
Solution Approach 2:
The crosslinking mechanism of the star macromolecules operates periodically, forming and breaking crosslinks in response to shear stress during pumping and injection. This periodic crosslinking allows the fluid to have low viscosity during the pumping phase (reducing energy use) and high viscosity during the proppant placement and fracture maintenance phases (improving retention)
3Reliability
If multi-functional polymer compositions are used to address multiple challenges, then performance under high stress improves, but the device complexity and formulation difficulty increase
Solution Approach 1:
The star macromolecules are designed with multiple functional arms that can simultaneously perform thickening, crosslinking, and proppant stabilization functions. This multi-functionality is achieved through the molecular architecture where different arms can interact with various components of the fracturing fluid system, reducing the need for multiple separate additives and simplifying the overall formulation while improving reliability under high stress conditions
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 polymer composition effectively increases the viscosity of hydraulic fracturing fluids, improving proppant transport and retention, and maintaining fracture width, even under high stress conditions, thereby enhancing oil and gas extraction efficiency.
Implementation Method 1
providing a dual mechanism for thickening via self-assembly and crosslinking with borate-type additives
Implementation Method 2
crosslinking with borate-type additives, enhancing viscosity and stability
Implementation Method 3
The polymer composition effectively increases the viscosity of hydraulic fracturing fluids, improving proppant transport and retention
Data Source
AI summary
The present invention relates to multi-arm star macromolecules which are used as thickening agents or rheology modifiers, including use in hydraulic fracturing fluid compositions. In one aspect of the invention, a star macromolecule is capable of thickening via a dual mechanism comprising (1) self-assembly of the hydrophobic polymerized segments of the star macromolecules via hydrophobic interactions or associations, and (2) association, reaction, or combination of the hydroxyl-containing polymerized segments of one or more of the star macromolecules.