Supercritical CO2 and Organic Solvent Injection for Reservoir Sweep
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Solution Overview
Problem
The existing methods for enhanced oil recovery, particularly using supercritical carbon dioxide, suffer from gravity override and viscous fingering issues due to density and viscosity differences, leading to poor reservoir sweep efficiency and early breakthrough, with current thickening agents and solvents having limitations such as high solubility and operational challenges.
Innovation Solution
A blend of supercritical carbon dioxide with an organic solvent like triethyl citrate is injected into the oil reservoir, increasing the density and viscosity of the fluid, minimizing gravity override and viscous fingering, while maintaining a single phase at reservoir conditions and allowing for easy recovery of the solvent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If supercritical carbon dioxide is injected into the oil reservoir, then oil displacement efficiency is improved due to miscibility and viscosity reduction, but gravity override occurs causing poor reservoir sweep efficiency
Solution Approach 1:
The patent changes the physical parameters of the injected fluid by blending carbon dioxide with an organic solvent, thereby increasing the density and viscosity of the injection fluid to match reservoir conditions and prevent gravity override
Solution Approach 2:
The patent uses a composite fluid system consisting of carbon dioxide blended with an organic solvent, creating a multi-component injection fluid that combines the benefits of miscibility with oil while achieving density matching to prevent gravity segregation
2Ease of operation
If blocking agents such as foam, cross-linked polymers, and gels are used to prevent gravity override, then reservoir sweep efficiency is improved, but the agents cannot withstand high temperatures and high salinities of some oil reservoirs
Solution Approach 1:
The patent changes the chemical composition of the injection fluid by using an organic solvent blend that is specifically selected to be stable under high temperature and high salinity conditions, thereby achieving both sweep efficiency improvement and environmental tolerance
3Ease of operation
If carbon dioxide thickeners such as polymers and small-molecule materials are used to increase viscosity, then gravity override is reduced, but operational issues occur since thickeners exist as solids at ambient conditions requiring dissolution
Solution Approach 1:
The patent changes the physical state and properties of the viscosity-modifying agent by using an organic solvent that is liquid at ambient conditions and mixes readily with carbon dioxide, eliminating the need for complex dissolution processes and solid handling equipment
4Ease of operation
If blending supercritical carbon dioxide with alcohol is used to increase density, then gravity override is reduced, but a significant amount of alcohol is required and it cannot be readily recovered
Solution Approach 1:
The patent changes the selection criteria for the density-modifying additive by using an organic solvent with appropriate density characteristics that can achieve density matching at lower concentrations and allows for easy recovery through standard separation processes
Solution Approach 2:
The patent implements a solvent recovery system where the organic solvent is separated from the produced fluids through mechanical separation techniques, allowing the solvent to be reused and minimizing loss of valuable materials
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 method enhances reservoir sweep efficiency, increases oil recovery, and allows for the reuse of the organic solvent, reducing operational and financial costs by minimizing gravity override and viscous fingering.
Implementation Method 1
blending a displacement fluid with an organic solvent to increase the density
Implementation Method 2
blending a displacement fluid with an organic solvent to increase the viscosity
Implementation Method 3
in a supercritical state, carbon dioxide can be miscible with crude oil, e.g., by extracting nonpolar compounds from oil
Implementation Method 4
carbon dioxide can swell the oil, lower oil viscosity
Implementation Method 5
decrease oil interfacial tension (IFT) with water
Data Source
AI summary
A method for mitigating gas override in an hydrocarbon reservoir by increasing sweep efficiency and consequently improving incremental oil recovery is provided with at least one injection well, at least one production well, and an hydrocarbon reservoir. The injection well and the production well are in fluid communication with the hydrocarbon reservoir. An injection blend produced by mixing a displacement fluid with an organic solvent is transferred into the hydrocarbon reservoir through the injection well. Preferably, the displacement fluid is supercritical carbon dioxide and the organic solvent is triethyl citrate. The higher density and the viscosity of the injection blend are vital in reducing gravity override and improving sweep efficiency. A resulting injection blend is extracted from the production well and the organic solvent is separated. Since the organic solvent can be reused, the method of mitigating gas override can be financially and operationally beneficial.