Foam Barrier for CO2 Injection in Gravity Drainage
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Solution Overview
Problem
In gravity drainage/CO2 injection processes for tertiary oil recovery, premature breakthrough of CO2 occurs due to viscosity differences and heterogeneities in reservoirs, leading to reduced sweep efficiency and wasted injection fluid, as the carbon dioxide injection rate must be maintained below the critical gas injection rate to prevent viscous fingering.
Innovation Solution
Introducing a foaming surfactant solution and foaming gas to form a stable foam barrier at the CO2/crude oil interface, which prevents CO2 breakthrough by creating a physical barrier that can be swept into high-conductivity zones, allowing for increased CO2 injection rates without bypassing untreated areas, using gases with low solubility in both water and crude oil to maintain foam stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If CO2 injection rate is increased to improve productivity, then hydrocarbon recovery increases, but CO2 breakthrough occurs due to viscosity differences causing viscous fingering
Solution Approach 1:
The patent introduces a foam barrier as an intermediary substance between the CO2 and crude oil. This foam barrier, formed by injecting foaming gas and surfactant solution, acts as a mediator that prevents direct CO2 breakthrough while allowing controlled displacement of crude oil. The foam stabilizes the interface and prevents viscous fingering, enabling higher CO2 injection rates without premature breakthrough.
Solution Approach 2:
The patent changes the physical and chemical parameters at the CO2-crude oil interface by introducing surfactants and foaming agents. These parameter changes create a foam barrier with different interfacial tension properties, viscosity characteristics, and stability features that prevent CO2 breakthrough while maintaining displacement efficiency.
2Reliability
If CO2 injection rate is maintained below critical rate to prevent breakthrough, then sweep efficiency is maintained, but productivity is reduced due to wasted injection fluid
Solution Approach 1:
The foam barrier serves as an intermediary that improves sweep efficiency by preventing CO2 bypass through high-permeability zones. The foam selectively blocks preferential flow paths while allowing CO2 to displace crude oil more uniformly, thereby improving sweep efficiency and reducing wasted injection fluid.
Solution Approach 2:
The foam barrier creates local quality changes in the reservoir by selectively blocking high-conductivity zones and preferential flow paths. This local modification of flow characteristics ensures more uniform CO2 distribution and improves sweep efficiency in previously bypassed areas.
3Stability of the object's composition
If foaming gas with low solubility is used to maintain foam stability, then foam barrier stability increases, but gas selection constraints increase
Solution Approach 1:
The patent specifies parameter changes by selecting gases with low solubility in both water and crude oil. This parameter selection (low solubility) ensures foam stability by preventing gas dissolution that would collapse the foam structure. The surfactant concentration and foam quality are also adjusted as parameters to maintain stable foam barriers.
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
This approach enhances crude oil production rates and sweep effectiveness by maintaining a stable foam barrier that prevents CO2 bypass, allowing for prolonged exposure of crude oil to supercritical CO2, resulting in increased hydrocarbon recovery and improved reservoir treatment uniformity.
Implementation Method 1
The foaming gas is introduced such that the surfactant solution and the foaming gas intimately intermingle and form barrier foam bubbles in the upper portion of the reservoir
Implementation Method 2
CO2 at super/critical conditions is used for its favorable phase behavior characteristics with crude oil means, such as swelling, viscosity reduction, and reduced fluid-crude oil interfacial tension
Implementation Method 3
Mobilized, the crude oil flows downward in the reservoir towards the recovery wellbore. Such crude oil drainage occurs through a combination of both film flow, caused by interaction with and absorption of some of the super/critical CO2, and gravity drainage
Implementation Method 4
The foam barrier is positioned at an interface between the hydrocarbons to be treated in the reservoir and the CO2 cap
Data Source
AI summary
Described is a method for treating hydrocarbons in a reservoir. A foaming surfactant solution and a foaming gas are introduced into the upper portion of a reservoir such that barrier foam bubbles form. Then, super/critical carbon dioxide is introduced such that a CO2 cap forms. The CO2 cap is formed above a foam barrier of aggregated barrier foam bubbles positioned at an interface between hydrocarbons to be treated in the reservoir and the CO2 cap. The super/critical carbon dioxide is introduced into the reservoir at an injection rate that is greater than a pre-treatment critical gas injection rate. Hydrocarbons are recovered from a lower portion of the reservoir.