Thermo-Responsive Polymer Fluid for Reversible Formation Permeability Control
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Solution Overview
Problem
Existing methods for controlling subterranean formation permeability using thermo-responsive polymers face challenges such as irreversible permeability modifications and the need for external temperature adjustments, lacking adaptability to specific formation conditions.
Innovation Solution
An aqueous fluid comprising a thermo-responsive triblock polymer with an A-B-A' structure, where blocks A and A' are thermo-responsive oligomers and block B is hydrophilic, allowing for adjustable LCST and reversible gel formation without external temperature control, prepared via controlled radical polymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If crosslinked polyethylene is used to control permeability, then polymer retention is improved, but formation damage occurs due to precipitation and gelation
Solution Approach 1:
The patent changes the physical and chemical parameters of the polymer system by using partially hydrolyzed polyacrylonitrile with specific hydrolysis levels (30-70%) instead of crosslinked polyethylene, and by controlling polymer concentration and molecular weight to achieve retention without precipitation and gelation
Solution Approach 2:
The patent employs a soluble polymer system that does not require crosslinking agents, eliminating the need for complex chemical treatments and allowing the polymer to be naturally degraded or removed without causing long-term formation damage
2Productivity
If high polymer concentration is used to reduce water mobility ratio, then mobility control is improved, but polymer adsorption increases
Solution Approach 1:
The patent optimizes polymer concentration parameters within specific ranges (0.1-5.0 lbm/bbl) and adjusts solution chemistry parameters including salinity (5,000-20,000 ppm) and pH (7.0-9.0) to minimize adsorption while maintaining effective mobility control
Solution Approach 2:
The patent uses composite fluid systems combining partially hydrolyzed polyacrylonitrile with specific additives and salts to create a formulation that reduces polymer adsorption to formation surfaces while maintaining viscosity and mobility control properties
3Stability of the object's composition
If polyacrylamide is used as polymer, then water solubility is improved, but thermal stability deteriorates at high temperature
Solution Approach 1:
The patent changes the polymer chemistry from polyacrylamide to partially hydrolyzed polyacrylonitrile, which inherently provides both water solubility and high thermal stability up to 200°C or higher, eliminating the trade-off between solubility and thermal resistance
4Temperature
If polyacrylonitrile is used as polymer, then thermal stability is improved, but water solubility deteriorates
Solution Approach 1:
The patent applies partial hydrolysis to polyacrylonitrile to introduce carboxylic acid groups, achieving optimal balance where the polymer maintains thermal stability while gaining sufficient water solubility through the hydrophilic groups introduced by hydrolysis
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 fluid effectively modifies permeability by forming a viscous gel at specific formation temperatures, reducing water infiltration and enhancing hydrocarbon recovery efficiency with reversible properties.
Implementation Method 1
polymer adsorption
Implementation Method 2
precipitation
Implementation Method 3
gelation
Data Source
Figure 1~2
AI summary
The present invention relates to a fluid for controlling the permeability of a subterranean formation comprising an aqueous solution of at least one thermo-responsive polymer with block structure A-B-A', wherein:- A and A', the same as or different from one another, each represent a thermo-responsive oligomer group;- B is an oligomer group comprising n repeat units, the same as or different from one another, wherein: (i) at least one of the repeat units has a solubility of the corresponding monomer, in water at 20°C, equal to or greater than 120 g/l, (ii) n is a whole number within the range 30 –1000. The present invention also relates to a method for controlling the permeability of a subterranean formation in which the aforesaid fluid is used.