Encapsulated Polymer Shell for Subterranean Permeability Control
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Solution Overview
Problem
Existing methods for modifying subterranean formation permeability using polymer solutions are limited by mechanical and chemical degradation, leading to reduced effectiveness and the need for excessive polymer usage, as well as environmental hazards from chromium salts and uncontrolled gelation kinetics.
Innovation Solution
A method involving a cross-linked (co)polymer that forms a hydrogel in the presence of water, encapsulated in a shell resistant to mechanical and chemical stresses, which is either pre-cross-linked or cross-linked in situ, to modify permeability by forming a hydrogel upon injection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymer solutions are injected into high-permeability zones to reduce water permeability, then water permeability is reduced and hydrocarbon recovery is improved, but the polymers undergo mechanical and chemical degradation leading to reduced effectiveness
Solution Approach 1:
The polymer is pre-encapsulated in a protective shell before injection, which shields it from mechanical shear stresses and chemical oxidation during injection and transport. This preliminary protective action prevents degradation before the polymer reaches the target zone, maintaining its effectiveness for permeability modification.
Solution Approach 2:
The encapsulating shell acts as an intermediary between the polymer and the harsh environment (oxygen, shear stresses). It mediates the interaction by providing a protective barrier that allows the polymer to survive injection conditions without direct exposure to degrading factors.
2Adaptability or versatility
If cross-linking agents are added to polymer solutions to control gelation, then gelation kinetics can be controlled, but environmental hazards arise from chromium salts and resins
Solution Approach 1:
The invention uses biodegradable, environmentally benign cross-linking agents that replace hazardous chromium salts and resins. These alternative agents provide the necessary gelation control but decompose into harmless substances, eliminating long-term environmental contamination while maintaining functional performance.
Solution Approach 2:
The invention changes the chemical parameters of the cross-linking system by selecting alternative agents with different chemical compositions that are environmentally friendly. This parameter change maintains gelation control capability while removing toxic components from the system.
3Ease of operation
If gel-based methods are used to block high-permeability zones, then water flow is diverted towards less permeable zones, but the high viscosity prevents oil or gas zones from being invaded
Solution Approach 1:
The treatment process is segmented into distinct phases: first, the encapsulated polymer is injected and protects itself during transport; second, the shell degrades and releases the polymer in the target zone; third, the polymer gels and blocks water flow. This segmentation allows each function to be optimized independently, achieving both flow diversion and hydrocarbon recovery.
Solution Approach 2:
The system transitions dynamically from a low-viscosity injectable state (encapsulated polymer) to a high-viscosity gel state (released and cross-linked polymer). This dynamic change allows the material to be easily injected through the wellbore while subsequently providing the high viscosity needed for flow diversion and zone blocking in the formation.
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 shell protects the polymer from degradation, allowing for controlled gelation and effective permeability modification, reducing the risk of environmental harm and improving hydrocarbon recovery by blocking high-permeability zones and diverting fluid flow towards less permeable zones.
Implementation Method 1
a cross-linked (co)polymer PR forming a hydrogel in the presence of water
Implementation Method 2
the shell protects the polymer from degradation
Data Source
AI summary
The invention relates to a method for modifying the water permeability of a subterranean formation, comprising at least the following steps:Preparing an injection fluid from a dispersion of a hydrophilic phase in a lipophilic phase, with water or brine, the dispersion comprising:a hydrophilic phase comprising at least one cross-linked (co)polymer PR,a lipophilic phase,at least one interface polymer composed of at least one monomer of formula (I):Injecting the injection fluid into the subterranean formation,said cross-linked (co)polymer PR forming a hydrogel in the presence of water.