Deep-Eutectic Surfactant Formulation for Low-Permeability Sandstone
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Solution Overview
Problem
Existing surfactants are not effective in enhancing the recovery rate of oil from low-permeability sandstone reservoirs due to high water injection pressure, water-sensitive damage, and incompatibility between injected water and formation fluid, leading to reduced permeability and ineffective conventional water flooding.
Innovation Solution
A method involving the preparation of a surfactant using a deep-eutectic solvent made from choline chloride and carboxylic acid, combined with CTAB, to reduce oil-water interfacial tension and inhibit clay mineral hydration, utilizing a mole ratio of 1:1 for choline chloride to carboxylic acid and 5:5 or 6:4 for the solvent and CTAB, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional water flooding is used in low-permeability reservoirs, then the injection process is simple, but the injection pressure is high and recovery rate is low
Solution Approach 1:
The patent changes the chemical parameters of the injection fluid by introducing a surfactant system comprising deep-eutectic solvent and CTAB. This chemical modification reduces oil-water interfacial tension to ultra-low levels (10^-3 mN/m), enabling effective oil displacement at lower injection pressures and improving recovery rates in low-permeability reservoirs
Solution Approach 2:
The patent creates a composite surfactant system by combining deep-eutectic solvent (formed from choline chloride and carboxylic acid) with cetyltrimethylammonium bromide (CTAB). This composite material provides both ultra-low interfacial tension and reservoir protection effects, resolving the contradiction between injection pressure and recovery rate
2Reliability
If water injection is performed in low-permeability reservoirs with high clay content, then the injection process is straightforward, but water-sensitive damage occurs reducing permeability
Solution Approach 1:
The deep-eutectic solvent acts as an intermediary substance that prevents direct harmful interaction between injected water and clay minerals. The solvent forms a protective interface that inhibits clay mineral hydration and swelling, thereby protecting reservoir permeability while allowing water injection to proceed
Solution Approach 2:
The patent modifies the chemical composition and properties of the injection fluid by incorporating deep-eutectic solvent, which changes the interaction parameters between water and clay minerals. This parameter change transforms the injection fluid from one that causes water-sensitive damage to one that protects the reservoir
3Productivity
If existing surfactants are used for oil displacement, then some oil recovery improvement is achieved, but they fail to provide adequate reservoir protection effects
Solution Approach 1:
The patent designs a surfactant system that performs multiple functions simultaneously: (1) reduces oil-water interfacial tension to ultra-low levels for effective oil displacement, and (2) protects reservoir minerals from water-sensitive damage. This multi-functional surfactant system resolves the contradiction between oil recovery improvement and reservoir protection
4Productivity
If deep-eutectic solvent and CTAB are mixed in certain ratios, then ultra-low interfacial tension is achieved, but the formulation complexity increases
Solution Approach 1:
The patent identifies specific optimal ratios for mixing deep-eutectic solvent and CTAB that achieve ultra-low interfacial tension. By establishing these precise parameter values (formulation ratios), the patent simplifies the complex formulation process into a standardized procedure that is easy to implement while maintaining high effectiveness
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 surfactant achieves ultra-low interfacial tension of 10−3 mN/m, inhibits clay mineral hydration, exhibits temperature and salt resistance, and is cost-effective, enhancing oil recovery by 38.4% with reduced injection pressure.
Implementation Method 1
The obtained surfactant reduces the oil-water interfacial tension to 10−3 mN/m
Implementation Method 2
The deep-eutectic solvent...can attach to the surface of clay minerals and inhibit the hydration expansion of clay minerals
Data Source
AI summary
The present invention provides a method of preparing a surfactant for improving the recovery rate of oil reservoirs in a low-permeability sandstone, including two steps of preparing a deep-eutectic solvent and preparing a surfactant. The surfactant of the present invention significantly reduces the interfacial tension between oil and water and has the effect of inhibiting the hydration expansion of clay minerals.