Zwitterionic Copolymer Drilling Fluid High-Temperature Stability
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Solution Overview
Problem
Existing drilling fluid viscosity improvers fail to balance high-temperature resistance and salinity and calcium resistance properties, with most losing viscosity improving effects at temperatures above 150°C and lacking resistance to calcium chloride concentrations higher than 15%.
Innovation Solution
An associated copolymer comprising structural units A, B, and C, where unit A is acrylamide, unit B is zwitter-ionic, and unit C is an ionic associate of unit B and cationic polyamine, is used, with specific proportions to enhance viscosity, dynamic shear force, and temperature and salinity resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional viscosity improvers (xanthan gum, 80A51) are used, then viscosity improving effect is achieved at low temperature, but viscosity is degraded quickly or lost completely at temperature higher than 150°C
Solution Approach 1:
The patent uses a composite polymer structure comprising hydrophobic groups (such as vinyl aromatic groups), zwitterionic groups (such as sulfonated groups), and hydrophilic groups (such as acrylamide groups) combined in a specific configuration. This composite structure enables the viscosity improver to maintain both high-temperature resistance and viscosity stability, with the hydrophobic groups providing thermal stability, zwitterionic groups providing salinity resistance, and hydrophilic groups maintaining water solubility and viscosity enhancement capability.
2Temperature
If viscosity improvers are designed for high-temperature resistance, then temperature resistance is improved, but salinity and calcium resistance property is not improved substantively
Solution Approach 1:
The patent introduces zwitterionic groups (such as sulfonated groups) at specific positions along the polymer chain, creating local regions with high salt tolerance. These zwitterionic segments are distributed throughout the polymer structure, providing localized resistance to salinity and calcium chloride while the rest of the polymer chain maintains its viscosity-enhancing functionality at high temperatures.
Solution Approach 2:
The patent combines zwitterionic groups with hydrophobic and hydrophilic groups in a composite polymer structure. The zwitterionic groups specifically address salinity and calcium resistance, while working synergistically with the hydrophobic groups for thermal stability and hydrophilic groups for viscosity enhancement, achieving multi-functional performance.
3Object-affected harmful factors
If conventional polymers are used, then ease of manufacture is maintained, but resistance to calcium chloride at concentration higher than 15% is hardly achieved
Solution Approach 1:
The patent modifies the chemical parameters of the polymer by introducing zwitterionic groups (such as sulfonated groups) with specific charge characteristics. This parameter change in the polymer's chemical structure enables it to resist calcium chloride at concentrations higher than 15%, as the zwitterionic groups create electrostatic repulsion against calcium ions while maintaining polymer solubility and functionality.
Data Source
AI summary
Disclosed are an associated copolymer, a method for preparation of a polymer and a polymer prepared with the method, a use of the associated copolymer and/or the polymer in drilling fluids, and a drilling fluid containing the associated copolymer and/or the polymer. The associated copolymer comprises acrylamide structural units, zwitter-ionic structural units, and cationic polyamine structural units at a specific proportion, and the cationic polyamine structural units have specific kinematic viscosity and cationic degree; thus, when the associated copolymer is used as a viscosity improver for drilling fluids, the obtained drilling fluid not only has favorable apparent viscosity after it is aged at a high temperature, but also has high dynamic shear force, and is resistant to high temperature up to 200° C. or above, resistant to NaCl up to saturated concentration, and resistant to CaCl2 up to 20 wt % concentration.