Crosslinked Polymer Flooding Fluid for Enhanced Oil Recovery
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Solution Overview
Problem
Current enhanced oil recovery techniques face challenges with poor sweep efficiency due to differences in water and oil mobility, and permeability variations in oil reservoirs, leading to reduced oil recovery rates, as high molecular weight polymers degrade under temperature, shear, and oxidative stress.
Innovation Solution
Incorporating a crosslinked water-soluble polymer with a polyvalent metal ion, such as aluminum citrate, into the aqueous flooding fluid, maintaining a weight ratio of polymer to crosslinking agent between 60:1 and 200:1, to enhance viscosity and shear resistance, thereby improving oil recovery without increasing pressure differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight water-soluble polymers are used to improve sweep efficiency, then viscosity increases and oil recovery improves, but the polymers undergo molecular weight breakdown and degradation due to temperature, high shear, oxidative stress, and physical force
Solution Approach 1:
The patent applies composite materials by combining water-soluble polymers with crosslinking agents (such as borax, aluminum sulfate, or ferric chloride) to create crosslinked polymer networks. This composite structure provides both the high viscosity needed for improved sweep efficiency and the structural stability to resist degradation from temperature, shear, and oxidative stress. The crosslinked network maintains polymer integrity while delivering enhanced oil recovery performance.
2Reliability
If crosslinked polymers are used to maintain viscosity and shear resistance, then oil recovery improves, but pressure differential may increase
Solution Approach 1:
The patent applies parameter changes by optimizing the crosslinking density and polymer concentration to achieve the desired viscosity profile. By carefully controlling the amount of crosslinking agent and the molecular weight distribution of the polymer, the formulation maintains adequate viscosity for sweep efficiency while ensuring the pressure differential remains within acceptable limits for field injection operations.
3Productivity
If polymer concentration is increased to improve sweep efficiency, then oil recovery increases, but injectivity decreases due to higher viscosity
Solution Approach 1:
The patent applies parameter changes by utilizing crosslinked polymer chemistry to achieve high viscosity at lower polymer concentrations. The crosslinked structure provides enhanced rheological properties that improve sweep efficiency without requiring high polymer doses, thereby maintaining acceptable injectivity. Additionally, the crosslinked network provides shear-thinning behavior that facilitates injection while maintaining reservoir viscosity.
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 crosslinked polymer maintains high viscosity and shear resistance, improving oil recovery rates and sweep efficiency by maintaining unimpeded flow through the reservoir, reducing viscosity loss, and enhancing injectivity.
Implementation Method 1
the crosslinked water-soluble polymer is derived from reacting a crosslinking agent with a polymer and the crosslinking agent comprises a polyvalent metal ion
Data Source
AI summary
Mobility control polymers can be used to increase recovery of crude oil from a subterranean hydrocarbon-containing formation. A flooding fluid comprising the polymer are injected into a well that is in contact with the subterranean hydrocarbon-containing formation. The polymers are derived from reacting a crosslinking agent with a polymer and the crosslinking agent comprises a polyvalent metal ion having a weight/weight ratio of polymer to crosslinking agent of at least 60:1. These flooding fluids have improved injectivity into the well; the improved injectivity can be measured in terms of the flooding fluid's filter ratio, flow rate, and viscosity.