CO2 Responsive Core-Shell Microspheres for Tight Oil Reservoir Plugging
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Solution Overview
Problem
Conventional gel particles used in CO2 flooding for tight oil reservoirs have short swelling times, are prone to dehydration in CO2 atmospheres, and exhibit limited secondary swelling and reduced strength after swelling, leading to low sweep efficiency and channeling prevention effectiveness.
Innovation Solution
A CO2 responsive core-shell multi-stage swelling microsphere is developed through a preparation method involving emulsion polymerization and specific chemical reactions to create a microsphere with three-stage swelling characteristics, enhanced hydrophilicity, and maintained strength, allowing for effective plugging of CO2 channeling paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional gel particles are used for CO2 flooding, then the channeling path can be plugged, but the particles dehydrate in CO2 atmosphere and lose plugging strength
Solution Approach 1:
The patent introduces CO2-responsive functional groups (amidine, zwitterion, ammonium) that change their hydration state in response to CO2 concentration. These groups undergo protonation reactions with CO2 to form hydrated species, dynamically adjusting the particle's hydrophilicity parameter to maintain swelling and plugging strength in CO2-rich environments.
Solution Approach 2:
The gel particles are constructed as composite materials containing both CO2-responsive functional groups and water-soluble polymer networks. This composite structure enables the particles to exhibit both mechanical strength for plugging and dynamic hydrophilicity adjustment in response to CO2, resolving the contradiction between stability and adaptability.
2Productivity
If CO2 responsive gel particles are used to achieve multi-stage swelling, then the sweep efficiency is improved, but the particles significantly reduce strength after swelling
Solution Approach 1:
The patent creates particles with heterogeneous internal structure containing regions of different cross-linking density and functional group distribution. This local quality variation allows different parts of the particle to undergo swelling at different stages, achieving multi-stage swelling that progressively plugs channels while maintaining overall structural integrity and strength.
Solution Approach 2:
The gel particles incorporate dynamic cross-linking mechanisms that allow reversible bond breaking and reforming during swelling. This dynamic behavior enables the particles to adapt their network structure during multi-stage swelling, dissipating stress and preventing catastrophic strength loss while maintaining plugging capability.
3Speed
If conventional gel particles reach swelling equilibrium quickly, then the process is fast, but the swelling time is short and dehydration occurs
Solution Approach 1:
The patent designs particles with multiple swelling stages triggered by periodic or sequential changes in CO2 concentration. The CO2-responsive groups undergo repeated protonation-deprotonation cycles, creating periodic swelling and deshvinging behavior that extends the duration of action while maintaining rapid response at each stage, effectively converting a single fast event into multiple sustained events.
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 microsphere achieves significant CO2 flooding sweep efficiency improvement by expanding multiple times in response to CO2, maintaining strength, and selectively plugging CO2 channels without affecting oil flow, thereby enhancing the recovery ratio and reducing construction costs.
Implementation Method 1
the CO2 responsive groups on polymer chains and CO2 are subjected to a protonation reaction to generate amidine bicarbonate, zwitterion adducts or ammonium carbamate
Implementation Method 2
the particles absorb water again to swell
Implementation Method 3
performing emulsion polymerization at 30-50° C. for 2-3 h to obtain a spherical polystyrene solution
Implementation Method 4
the hydrophilicity of the particles is enhanced, and two-stage swelling occurs
Data Source
AI summary
The present invention discloses a CO2 responsive core-shell multi-stage swelling microsphere and a preparation method thereof. The preparation method comprises the following steps: adding a styrene monomer into a sodium dodecyl sulfate solution for emulsion polymerization to obtain a spherical polystyrene solution, taking azobisisobutyronitrile and ethylene glycol for Pinner reaction to obtain an azo compound with hydroxyl functional groups at two ends, taking the azo compound with the hydroxyl functional groups at two ends as a raw material for Schotten-Baumann reaction with methacryloyl chloride to obtain BPAB, adding the BPAB into the spherical polystyrene solution to prepare an active polystyrene core solution, and dissolving the active polystyrene core solution, acrylamide, a CO2 responsive monomer, a CO2 responsive cross-linking agent and a stable cross-linking agent into water to obtain a target product. The CO2 responsive core-shell multi-stage swelling microsphere of the present invention can remarkably improve the CO2 flooding sweep efficiency.