High-Temperature Molecular Membrane Acid Copolymer for Carbonate Reservoirs
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Solution Overview
Problem
Existing retarded acid systems for acidizing carbonate reservoirs face challenges in maintaining viscosity and stability at high temperatures, leading to reduced effectiveness and potential harm to the reservoirs.
Innovation Solution
A high-temperature-resistant deep penetration molecular membrane acid copolymer is developed, comprising a specific structural formula and prepared through inverse emulsion polymerization using four functional monomers, which forms a molecular membrane agent that can be added to an acid solution to enhance its retardation and penetration capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If gelling acid or crosslinking acid is used to improve viscosity through polymer thickening agents, then the acid rock reaction rate is reduced, but the polymer molecular chains curl and fracture under high temperature and high shear conditions, reducing viscosity and retardo ability
Solution Approach 1:
The patent changes the chemical structure parameters of the polymer by introducing fluorinated side chains with specific lengths (C8-C18) and incorporating quaternary ammonium groups. These parameter changes enable the polymer to maintain viscosity stability at high temperatures (up to 150°C) by preventing molecular chain fracture through enhanced thermal stability and hydrophobic interactions.
Solution Approach 2:
The patent creates a composite polymer structure combining hydrophobic fluorinated chains, hydrophilic polyacrylamide backbone, and quaternary ammonium functional groups. This composite structure integrates multiple functions: thermal stability from fluorinated chains, viscosity enhancement from polyacrylamide, and high-temperature resistance from quaternary ammonium groups, resolving the contradiction between viscosity stability and temperature resistance.
2Stability of the object's composition
If polymer molecular chains are used to thicken acid system, then the acid rock reaction rate is reduced, but the polymer molecules cause harm to oil and gas reservoirs by reducing reservoir permeability
Solution Approach 1:
The patent applies local quality by concentrating the retardo function in specific quaternary ammonium functional groups located at side chains, while the main polymer chain maintains appropriate molecular weight and structure for viscosity enhancement. This localized functional distribution provides effective retardation without requiring excessive polymer concentration, thereby minimizing reservoir damage and preserving permeability.
Solution Approach 2:
The patent optimizes the molecular weight parameter of the polymer (50,000-2,000,000 g/mol) and the concentration of quaternary ammonium groups to achieve effective retardation with minimal polymer dosage. By changing these parameters, the patent reduces the total polymer volume in the reservoir, thereby minimizing permeability reduction while maintaining adequate retardo ability.
3Speed
If emulsified acid or foam acid is used to slow down acid rock reaction rate, then the reaction rate is reduced, but the two-phase emulsion or foam has poor stability at high temperature and high viscosity
Solution Approach 1:
The patent replaces the mechanical two-phase emulsion or foam system with a molecular membrane acid system. Instead of relying on physical phase separation and interfacial tension to slow reaction rates, the patent uses molecular-level interactions between quaternary ammonium groups and rock surfaces to create a molecular membrane that retards acid diffusion. This substitution eliminates the stability issues of high-temperature emulsions and foams while maintaining effective reaction rate control.
4Length of moving object
If conventional acid is used for acidizing, then the acid enters the stratum and unblocks oil reservoir blockage, but the H+ is consumed in large quantities, resulting in shortening of effective distance of acid in the stratum
Solution Approach 1:
The patent introduces a molecular membrane as an intermediary between the acid and the rock surface. The quaternary ammonium-containing polymer forms a molecular membrane on the rock surface that selectively retards H+ diffusion while allowing other beneficial components to penetrate. This intermediary layer reduces unnecessary H+ consumption near the wellbore and directs acid flow deeper into the formation, thereby increasing effective penetration distance and reducing overall H+ consumption.
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 molecular membrane acid copolymer effectively retards the acid rock reaction rate, exhibits deep penetration capabilities, and maintains stability at high temperatures, reducing residue content and corrosion while improving the acidizing effect.
Implementation Method 1
the copolymer emulsion...as a molecular membrane agent...to prepare the molecular membrane acid...when the molecular membrane acid contacts with the carbonate reservoir, the N—H groups in the molecules form hydrogen bonds with the metal ions on the surface of the ore
Implementation Method 2
the N—H groups in the molecules form hydrogen bonds with the metal ions on the surface of the ore
Implementation Method 3
the sulphonic acid groups form ion-pair interactions with the metal ions
Implementation Method 4
the quaternary ammonium cations in the molecules act on the CO32− sites by electrostatic adsorption
Implementation Method 5
the phosphate groups retard the acid rock reaction rate by capturing a portion of H+, and releases the portion of H+ when an acid concentration decreases, realizing a buffering effect
Data Source
AI summary
The present disclosure provides a high-temperature-resistant deep penetration molecular membrane acid copolymer and a preparation method thereof. The copolymer is formed by polymerizing four raw monomers including 2-acrylamido-2-methylpropanesulphonic acid, vinyl phosphonic acid, alkyl dimethylallyl ammonium chloride, and perfluoropolyether acrylate. The method comprises: S1: mixing and stirring solvent oil, an emulsifier, the alkyl dimethyl allyl ammonium chloride, and the perfluoropolyether acrylate to be dispersed homogeneously to obtain an oil phase; S2: mixing and stirring the 2-acrylamido-2-methylpropanesulphonic acid, the vinyl phosphonic acid, a complexing agent, and distilled water, and adjusting pH to obtain an aqueous phase; S3: slowly dropwise adding the aqueous phase to the oil phase; and S4: introducing nitrogen into the water-in-oil emulsion to remove oxygen, then adding an initiator and carrying out a heating polymerization reaction to obtain copolymer emulsion (i.e., a molecular membrane agent). The copolymer emulsion is added to an acid solution to obtain molecular membrane acid.