Shear-Resistant Crosslinked Polymer Fluid for Hydraulic Fracturing
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Solution Overview
Problem
Zirconium-crosslinked polymer fluids used in hydraulic fracturing are sensitive to shear, leading to irreversible viscosity loss, particularly in high-temperature environments, which hampers hydrocarbon recovery from subterranean formations.
Innovation Solution
The development of shear-resistant crosslinked polymer fluids incorporating a water-soluble polymer, a crosslinking agent, and an acidic pH adjusting agent, along with a delayed release alkaline additive, such as urea or alkaline earth metal carbonates/oxides, to maintain fluid viscosity and stability under high shear and temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If zirconium-crosslinked polymer fluids are used to maintain viscosity in hydraulic fracturing, then fluid viscosity is improved, but shear sensitivity causes irreversible viscosity loss
Solution Approach 1:
The patent changes the pH parameter of the fluid system by introducing an acidic pH adjusting agent to maintain pH below 7. This parameter change modifies the chemical environment to reduce crosslinking sensitivity to shear, allowing the fluid to maintain viscosity while reducing irreversible viscosity loss. The pH adjustment fundamentally alters the chemical state of the system to resolve the contradiction between viscosity maintenance and shear resistance.
2Reliability
If crosslinking is delayed to avoid high-shear regions, then shear sensitivity is reduced, but crosslinking initiation timing becomes difficult to control
Solution Approach 1:
The patent introduces an acidic pH adjusting agent as an intermediary substance that mediates the crosslinking process. Rather than directly controlling crosslinking timing through complex mechanisms, the acid acts as an intermediary that modifies the chemical environment to suppress premature crosslinking in high-shear regions. This intermediary approach simplifies the control mechanism while effectively reducing shear sensitivity.
3Reliability
If low pH is used to improve shear recovery, then viscosity recovery after shearing is improved, but polymer instability occurs in high-temperature environments
Solution Approach 1:
The patent carefully adjusts the pH parameter to a specific range (below 7) that balances two competing requirements: low enough to promote shear recovery and viscosity recovery, but not so low as to cause severe polymer degradation at high temperatures. This precise parameter control resolves the contradiction by finding the optimal pH window that satisfies both shear recovery and polymer stability requirements.
4Stability of the object's composition
If high pH is used to prevent polymer deterioration at high temperature, then polymer stability is improved, but shear recovery becomes poor
Solution Approach 1:
The patent modifies the pH parameter from conventional high pH values to a controlled lower pH range (below 7). This parameter change simultaneously improves shear recovery while maintaining adequate polymer stability through the use of acid-stable crosslinking systems. The pH adjustment fundamentally shifts the chemical environment to favor shear recovery without sacrificing polymer stability.
Data Source
AI summary
A method of treating a subterranean formation penetrated by a wellbore utilizes a treating fluid formed from an aqueous solution of a water-soluble polymer. The treating fluid further contains a crosslinking agent and an optional delayed release alkaline additive. The delayed release alkaline additive may be at least one of urea, a urea derivative, a solid alkaline earth metal carbonate, a solid alkaline earth metal oxide and combinations of these. The treating fluid further includes an acidic pH adjusting agent used in an amount to provide the treating fluid with a pH of less than about 5. The treating fluid is then introduced into the formation.