CO2-Soluble Compositions for Wettability Control in Tight Oil Formations
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Solution Overview
Problem
Existing methods for enhanced oil recovery in unconventional and low-permeability formations have limited success due to the high viscosity of water and low solubility of hydrocarbons, making it difficult to effectively alter wettability and enhance oil recovery.
Innovation Solution
Injecting a composition of carbon dioxide and carbon-dioxide-soluble compounds, such as surfactants or ketones, into the subterranean formation to alter wettability by diffusion and adsorption, reducing oil-wettability or increasing water-wettability, particularly in unconventional formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If aqueous surfactant solutions are used to alter wettability in unconventional formations, then water wettability should increase, but the high viscosity of water limits effectiveness in low-permeability formations
Solution Approach 1:
The patent changes the physical state of the fluid from liquid (aqueous solution) to gas (CO2). By using carbon dioxide in a gaseous or supercritical state, the viscosity is dramatically reduced compared to liquid water, enabling effective penetration into low-permeability unconventional formations while maintaining wettability alteration capability through CO2-soluble surfactants
Solution Approach 2:
The patent replaces the mechanical pushing force required to move high-viscosity aqueous solutions through tight formations with the solubility-driven transport mechanism of CO2. The CO2-soluble surfactant dissolves in the CO2 phase and is transported directly to the formation, eliminating the need to overcome high water viscosity resistance
2Productivity
If conventional CO2 foam methods are used, then mobility control is improved, but surfactant partitions into brine reducing transport efficiency
Solution Approach 1:
The patent inverts the traditional foam configuration from CO2-in-water (where surfactant stabilizes water lamellae) to water-in-CO2 (where surfactant stabilizes water droplets dispersed in CO2). This inversion changes the continuous and dispersed phases, allowing the surfactant to remain primarily in the CO2 phase and be transported efficiently while still providing mobility control through the resulting foam structure
Solution Approach 2:
The patent changes the phase composition and distribution parameters by creating a water-in-CO2 emulsion rather than a CO2-in-water foam. This parameter change affects which phase is continuous and which is dispersed, fundamentally altering surfactant partitioning behavior and transport mechanics while maintaining foam stability and mobility control benefits
3Ease of operation
If aqueous surfactant is injected into shale formations, then wettability alteration should occur, but low hydrocarbon solubility in water limits oil recovery
Solution Approach 1:
The patent creates a composite injection fluid combining CO2 and CO2-soluble surfactant. This composite material provides dual functionality: the CO2 phase offers high hydrocarbon solubility and swelling capability, while the dissolved surfactant provides wettability alteration. The synergistic combination resolves the contradiction by delivering both wettability change and enhanced hydrocarbon mobilization in a single injection fluid
Solution Approach 2:
The patent merges the functions of hydrocarbon solubilization (provided by CO2) and wettability alteration (provided by surfactant) into a single unified injection system. Instead of using separate aqueous surfactant and CO2 injections, the surfactant is dissolved in the CO2 phase, allowing simultaneous delivery of both functional components that work together to enhance oil recovery through combined wettability alteration and hydrocarbon extraction
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
Enhances hydrocarbon recovery by altering wettability, allowing for increased oil extraction through CO2-philicity and water-wettability, leveraging the solvent strength and low viscosity of CO2 to improve recovery rates in tight reservoirs.
Implementation Method 1
Injecting a composition of carbon dioxide and carbon-dioxide-soluble compounds, such as surfactants or ketones, into the subterranean formation to alter wettability by diffusion and adsorption
Implementation Method 2
Injecting a composition of carbon dioxide and carbon-dioxide-soluble compounds, such as surfactants or ketones, into the subterranean formation to alter wettability by diffusion and adsorption
Implementation Method 3
Carbon dioxide (CO2) has been used to fracture wells and/or to recover oil from shale that has already been fractured based on its solvent strength for oil
Implementation Method 4
Carbon dioxide (CO2) has been used to fracture wells and/or to recover oil from shale that has already been fractured based on its solvent strength for oil
Implementation Method 5
Carbon dioxide (CO2) has been used to fracture wells and/or to recover oil from shale that has already been fractured based on its solvent strength for oil, its ability to reduce oil viscosity
Implementation Method 6
Carbon dioxide (CO2) has been used to fracture wells and/or to recover oil from shale that has already been fractured based on its solvent strength for oil, its ability to swell oil
Data Source
AI summary
A method of recovering hydrocarbons from a subterranean formation includes injecting into the subterranean formation a composition including carbon dioxide and at least one carbon-dioxide-soluble compound under conditions favorable to diffusion into and adsorption of the carbon-dioxide-soluble compound on the subterranean formation so that oil-wettability is decreased or water wettability or CO2-philicity is increased in at least a portion the subterranean formation.