Low pH Self-Crosslinking Polymers for CO2 Flood Diversion
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Solution Overview
Problem
Current polymer systems used in CO2 flooding are not effective in increasing viscosity and forming gels under acidic conditions, leading to inefficient oil recovery due to low viscosity at pH ranges typical of CO2 floods, and are prone to washout and incompatibility with brine conditions.
Innovation Solution
Development of acrylamide-based polymers that self-crosslink or crosslink with phenolic crosslinkers like phenol, resorcinol, or catechin at low pH, forming gels suitable for diverting CO2 to lower permeability zones, thereby enhancing oil production by increasing viscosity and stability under acidic conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer systems are used in CO2 flooding, then the process is simple to implement, but the polymers cannot maintain viscosity and form gels under acidic conditions (pH 2-4)
Solution Approach 1:
The patent modifies the chemical structure of polymers by introducing pH-sensitive functional groups (carboxylic acids, phenolic hydroxyls) that undergo conformational changes and crosslinking at low pH values (2-4), transforming the polymer from a linear chain to a gel network structure that maintains viscosity under acidic conditions typical of CO2 flooding
Solution Approach 2:
The invention creates composite gel systems by combining pH-sensitive polymers with crosslinking agents (metal ions, organic crosslinkers) that form stable three-dimensional networks under acidic conditions, resulting in a composite material that resists washout and maintains structural integrity in brine environments
2Productivity
If polymers are used to increase viscosity and block high permeability zones, then CO2 diversion to unswept zones is improved, but the polymers are prone to washout under high velocity flow conditions
Solution Approach 1:
The patent employs polymers that undergo spontaneous crosslinking and gel formation upon contact with acidic brine in the reservoir, creating a pre-formed gel structure before CO2 injection begins, which provides immediate resistance to high velocity flow and prevents washout during the flooding process
Solution Approach 2:
The invention utilizes polymers with dynamic rheological properties that allow them to remain soluble and pumpable at injection conditions but undergo rapid gelation in situ when exposed to acidic brine, creating a dynamic system that transitions from fluid to gel state to resist washout under production conditions
3Reliability
If crosslinking is used to enhance gel stability and viscosity, then polymer performance under acidic conditions is improved, but the crosslinking process increases system complexity
Solution Approach 1:
The patent employs polymers with self-crosslinking capability through pH-sensitive functional groups that automatically form crosslinks when exposed to acidic brine without requiring external crosslinking agents or complex addition systems, simplifying the overall system while achieving stable gel formation under low pH conditions
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 polymers effectively divert CO2 to unswept zones, improving oil recovery by forming stable gels that maintain viscosity and resist washout, even at low pH and brine conditions, thereby increasing the sweep efficiency of CO2 floods.
Implementation Method 1
polymers that can self-crosslink or crosslink with organic crosslinkers, such as phenol, resorcinol, catechin, and the like at low pH
Implementation Method 2
Occurrence of such crosslinkings will result in the increase of polymer molecular weight and/or allow gel formation
Implementation Method 3
CO2 dissolves in the water making carbonic acid
Implementation Method 4
CO2 dissolves in the water making carbonic acid. This often results in acidic conditions
Data Source
AI summary
The invention is directed to polymers that self-crosslink at acidic pH or can be crosslinked by phenolic agents in brine. Such polymers have lower viscosity and can be pumped deep into reservoirs, where they will cross link in situ, thus increasing their viscosity and/or form a gel and blocking thief zones. Methods of making and using such polymers are also provided.