Anionic Polymers for High-Temperature Oil Recovery
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Solution Overview
Problem
Current polymers used in enhanced oil recovery (EOR) techniques face thermal instability and degradation issues at high temperatures and in the presence of divalent ions, leading to reduced viscosity and poor performance, limiting their effectiveness in tertiary recovery processes.
Innovation Solution
Development of water-soluble anionic polymers comprising N-vinylpyrrolidone, Acrylamido tertiary butyl sulfonic acid, and acrylamide, with a weight average molecular weight of 1-20 million, in equimolar amounts, which provide improved thermal stability and viscosity retention, suitable for high-temperature applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If partially hydrolyzed polyacrylamides (PHPA) are used to increase viscosity, then areal sweep and mobility ratio are improved, but thermal stability is lost at temperatures higher than 80°C
Solution Approach 1:
The patent changes the chemical parameters of the polymer by using acrylamido tertiary butyl sulfonic acid instead of partially hydrolyzed polyacrylamide. This parameter change allows the polymer to maintain viscosity stability at high temperatures (above 80°C) while still providing the necessary areal sweep and mobility ratio improvements for enhanced oil recovery.
Solution Approach 2:
The patent employs a composite polymer structure containing acrylamido tertiary butyl sulfonic acid units combined with other compatible monomers. This composite approach creates a polymer that integrates both thermal stability and viscosity-modifying properties, resolving the contradiction between maintaining reliability at elevated temperatures.
2Reliability
If anionic polymers are used to modify viscosity, then areal sweep is improved, but polymer precipitation occurs in the presence of divalent ions
Solution Approach 1:
The patent changes the chemical parameters by selecting acrylamido tertiary butyl sulfonic acid as the primary functional monomer. This specific chemical structure modifies how the polymer interacts with divalent ions, preventing precipitation while maintaining anionic charge for effective viscosity modification and areal sweep improvement.
Solution Approach 2:
The patent converts the potential harmful interaction between anionic polymers and divalent ions into a beneficial relationship. The acrylamido tertiary butyl sulfonic acid structure is designed to tolerate or even utilize the presence of divalent ions, transforming what would normally cause precipitation into a stable polymer solution that maintains its viscosity-modifying function.
3Productivity
If polymers are exposed to high temperature for prolonged periods, then oil recovery continues, but thermal degradation reduces viscosity
Solution Approach 1:
The patent changes the thermal parameter resistance by incorporating heat-stable acrylamido tertiary butyl sulfonic acid units in the polymer chain. This parameter change enables the polymer to withstand prolonged exposure to high temperatures (above 80°C) without significant thermal degradation, maintaining viscosity and continuing to enhance oil recovery over extended periods.
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 polymers maintain their viscosifying properties, enhancing oil recovery efficiency by reducing thermal degradation and viscosity variations, allowing for more effective oil displacement and recovery even under prolonged exposure and high-salinity conditions.
Implementation Method 1
The polymer is able to provide various viscosity levels by entanglement and inter chain interactions
Implementation Method 2
Chemical injection traditionally uses polymers to increase the viscosity of the water phase
Implementation Method 3
The thermal degradation behavior of the polymers is more associated with chemical modifications or the polymer chemistry and with the temperature and the time of exposure
Implementation Method 4
it has been shown that above 95° C., the sulfonated acrylamide hydrolyzes and, thus, renders this class of polymer only suitable for temperatures lower than 95° C.
Data Source
AI summary
The present invention refers to the use of anionic water-soluble polymers being partially or totally neutralized with an organic counter-ion for oil filed application, especially tertiary oil recovery steps.