Zwitterionic Crosslinkable Polymer for High TDS Fluid Rheology
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Solution Overview
Problem
Existing viscosifiers for oilfield fluids, particularly those used in high total dissolved solid (TDS) or heavy brine environments, face challenges in controlling rheology and achieving yield stress due to limited solubility and stability issues, especially with multivalent cations, which hinder their application in ultra-deep wells and fracturing operations.
Innovation Solution
A zwitterionic and crosslinkable polymer is developed through inverse emulsion polymerization, comprising monomers with betaine groups, nonionic monomers, and metal ion crosslinkable groups, which maintains solubility and stability even in high salt concentrations, allowing for effective rheology control and yield stress generation in heavy brines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If natural or synthetic polymers are used to control rheology in high TDS fluids, then viscosity control is achieved, but solubility is limited and polymer stability at elevated temperature is disappointing
Solution Approach 1:
The patent changes the chemical composition parameters of the polymer by incorporating zwitterionic groups (betaine groups) and crosslinkable units in specific ratios. This compositional modification enables the polymer to maintain stability in high TDS environments while preserving rheology control performance, directly resolving the contradiction between stability and reliability
Solution Approach 2:
The patent creates a composite polymer structure combining zwitterionic monomers (for stability in high salt environments), nonionic monomers (for solubility), and crosslinkable monomers (for rheology control). This composite approach integrates multiple functional properties into a single polymer system that simultaneously achieves stability and reliability in high TDS conditions
2Force
If polymers are crosslinked via metal ion crosslinkers to obtain yield stress, then yield stress is achieved, but solubility is limited and precipitation occurs in high salt concentration fluids
Solution Approach 1:
The patent applies local quality by creating micro-scale crosslinked structures within a soluble polymer matrix. The crosslinking occurs locally to provide yield stress, while the bulk polymer remains soluble due to the zwitterionic and nonionic components. This localized crosslinking approach prevents macro-scale precipitation while achieving the desired yield stress
Solution Approach 2:
The patent modifies the crosslinking parameters by using specific metal ions (Ca2+, Sr2+, Ba2+) and controlling the crosslinking density through monomer C content (0.5-15 mol%). This parameter optimization ensures sufficient crosslinking for yield stress while maintaining solubility in high salt environments, resolving the contradiction between force generation and compositional stability
3Stability of the object's composition
If high molecular weight polymers are used for rheology control, then viscosity control is improved, but hydration is difficult and hydration kinetic is extremely slow
Solution Approach 1:
The patent segments the polymer chain into repeating units with specific functional groups (zwitterionic, nonionic, and crosslinkable units). This segmentation creates a structure that balances molecular weight for rheology control with sufficient hydrophilic character for rapid hydration. The segmented structure allows water penetration and hydration without requiring excessively long hydration times
Solution Approach 2:
The patent optimizes the molecular weight and compositional parameters of the polymer to achieve rapid hydration. By controlling the ratio of zwitterionic to nonionic monomers and limiting crosslinkable unit content, the polymer achieves a balance between molecular weight (for rheology) and hydration rate, reducing hydration time while maintaining viscosity control capability
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 system effectively controls rheology and imparts yield stress in high TDS fluids and heavy brines, enhancing the performance of fracturing, completion, and conformance control fluids by maintaining viscosity and stability across varying salt concentrations.
Implementation Method 1
a zwitterionic and crosslinkable polymer, prepared by inverse emulsion polymerization... a metal ion compound leading to the crosslinking of the groups carried by monomers C
Implementation Method 2
metal ion crosslinkers such as a zirconate or titanate that interact with crosslinkable units present on the polymer
Implementation Method 3
a zwitterionic and crosslinkable polymer... that maintains solubility and stability even in high salt concentrations
Implementation Method 4
A specific rheology control that is especially difficult to obtain with heavy brines or high TDS fluids is yield stress... this yield stress prevents the settling of proppant particles
Data Source
AI summary
The invention relates to aviscosifier useful for oilfield fluids, especially high TDS fluids and heavy brines, comprising:at least a zwitterionic polymer, prepared by inverse emulsion polymerization of:monomers A comprising a betaine group;nonionic monomers Bmonomers C including a metal ion crosslinkable group with a molar ratio of the monomers A to the monomers B between 4/96 and 40/60; andat least a metal ion compound leading to the crosslinking of the groups carried by monomers C.