Electrolyte-Containing Polymer Solution for High-Saline Oil Recovery
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Solution Overview
Problem
Current enhanced oil recovery (EOR) methods, such as polymer and surfactant flooding, face challenges in maintaining viscosity in high-saline environments and are economically limited due to high surfactant requirements and incompatibility with divalent ions, leading to precipitation and clogging issues.
Innovation Solution
An electrolyte-containing aqueous polymer solution is developed, using copolymers derived from carboxamides and ethylenically unsaturated sulfonic acids, with specific structural units and a nonionic surfactant, which maintains viscosity and filterability even in high-saline conditions, preventing precipitation and improving injectability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surfactant flooding is used to reduce interfacial tension and emulsify oil, then oil recovery efficiency is improved, but the amount of surfactant required becomes very high (1 to 5% of crude oil), making the method uneconomical
Solution Approach 1:
The patent combines polymer flooding and surfactant flooding into a unified ASP (alkali-surfactant-polymer) flooding system. The polymer provides viscosity control and mobility management, while the surfactant reduces interfacial tension. This merging allows lower surfactant concentrations (0.2-2% of crude oil) to achieve effective oil recovery by synergistic action with the polymer, reducing the economically prohibitive surfactant requirements of pure surfactant flooding
Solution Approach 2:
The invention uses a composite flooding agent consisting of polymer, surfactant, and alkali components working together. The polymer-surfactant-alkali composite system provides multiple functions simultaneously: viscosity enhancement, interfacial tension reduction, and emulsification. This composite approach allows effective oil recovery at reduced surfactant concentrations compared to pure surfactant flooding
2Quantity of substance
If alkali surfactant polymer flooding (ASP) is used to reduce surfactant concentration, then economic feasibility is improved, but divalent ions react with alkali components causing precipitation and reservoir clogging
Solution Approach 1:
The patent modifies the chemical parameters of the flooding system by carefully controlling pH, ionic strength, and component ratios. The alkali concentration is optimized to maintain surfactant effectiveness while minimizing precipitation reactions with divalent ions. Polymer concentration and molecular weight are adjusted to provide viscosity control that compensates for reduced surfactant levels, allowing operation in brine environments without clogging
Solution Approach 2:
The polymer acts as an intermediary between the alkali and surfactant components, stabilizing the system in the presence of divalent ions. The polymer structure provides a protective matrix that prevents direct harmful interactions between alkali and metal ions, while maintaining the surfactant's emulsification capability. This intermediary role allows ASP flooding to proceed without the precipitation and clogging problems that would otherwise occur
3Stability of the object's composition
If polymer concentration is increased to maintain viscosity in high-saline environments, then mobility control is improved, but filterability decreases and injection becomes difficult
Solution Approach 1:
The patent optimizes polymer concentration to the minimum level required for effective viscosity control (typically 500-5000 ppm), rather than using high concentrations. The polymer molecular weight and hydrolysis degree are adjusted to maximize viscosity efficiency at lower concentrations. Surfactant addition further enhances viscosity stability through hydrophobic association, allowing effective mobility control at polymer concentrations that maintain good filterability and injectability
4Productivity
If conventional polymers are used in high-temperature reservoirs, then oil recovery is achieved, but polymer degrades due to thermal instability and microbial activity
Solution Approach 1:
The patent employs a composite polymer-surfactant system where the surfactant provides thermal and microbial stability to the polymer. The surfactant forms protective complexes with the polymer chains, reducing their susceptibility to thermal degradation and microbial attack. This composite structure allows the polymer to maintain its viscosity-enhancing properties and oil recovery effectiveness in high-temperature reservoir environments where conventional polymers would rapidly degrade
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 solution effectively builds and maintains viscosity in high-saline environments, ensuring stable injection and filtration behavior, reducing the risk of blockages and enhancing the efficiency of oil recovery without the need for extensive surfactant concentrations.
Implementation Method 1
The invention relates to electrolyte-containing aqueous polymer solutions... copolymers... with structural units... derived from carboxamides and ethylenically unsaturated sulfonic acids... which build viscosity in aqueous media via hydrophobic association of the structural units
Implementation Method 2
The aqueous polymer solution contains... a nonionic surfactant... Many surfactants exhibit clouding ('cloud point') when introduced into hot, saline aqueous solutions. This means that these surfactants agglomerate in hot saline water.
Data Source
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Figure 3
AI summary
The invention relates to an electrolyte-containing aqueous polymer solution having a salt content of 5 to 35 wt% with respect to the total amount of the polymer solution. Said polymer solution contains: at least one dissolved synthetic copolymer, which contains structural units that are derived from (i) at least one amide of an ethylenically unsaturated carboxylic acid and from (ii) at least one ethylenically unsaturated sulfonic acid or alkali metal salts and/or ammonium salts thereof; and at least one non-ionic surfactant selected from the group of the alkoxylated fatty alcohols, the alkoxylated alkylphenols, and/or the alkoxylated fatty acids, with the stipulation that the average degree of alkoxylation of said surfactants is 8 to 10. The aqueous polymer solution is used in the tertiary recovery of petroleum and is distinguished by very good filtration behaviour, in particular if saline water is present.