Extensional Capillary Number for Polymer Viscoelastic Sor Prediction
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Solution Overview
Problem
Current methods for predicting residual oil saturation during viscoelastic polymer flooding in enhanced oil recovery (EOR) are limited by the use of conventional capillary number (Nc) and Deborah number, which fail to accurately account for the viscoelastic effects of polymers, leading to incorrect estimates of oil recovery potential and suboptimal polymer selection.
Innovation Solution
The method calculates an extensional capillary number (Nce) using flux, pore-scale apparent viscosity, and interfacial tension to quantify the viscoelastic forces responsible for residual oil saturation reduction, and compiles these values in a database for use in a reservoir simulator to predict Sor reduction potential, incorporating extensional rheological properties to better model polymer behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capillary number (Nc) is used to predict residual oil saturation reduction, then the prediction method is simple, but the prediction accuracy is poor because it fails to account for viscoelastic effects
Solution Approach 1:
The patent introduces a new parameter - extensional capillary number (Nce) - that incorporates extensional viscosity to replace the conventional capillary number. This parameter change enables accurate prediction of Sor reduction by accounting for viscoelastic effects while maintaining the predictive framework's usability
Solution Approach 2:
The patent introduces an intermediary concept - extensional viscosity - that mediates between the polymer's viscoelastic properties and the capillary number calculation. This intermediary allows the conventional Nc framework to capture viscoelastic effects without requiring complete reformulation of the predictive method
2Reliability
If Deborah number is used to account for viscoelastic effects, then the viscoelastic influence is considered, but the estimation of oil recovery potential remains incorrect
Solution Approach 1:
The patent transforms the Deborah number approach by introducing extensional viscosity into the capillary number framework. This parameter transformation creates a new metric (Nce) that correctly estimates oil recovery potential while preserving the viscoelastic effect accounting capability
3Measurement precision
If polymer viscosity is increased to enhance Sor reduction, then the capillary number increases, but injectivity problems occur
Solution Approach 1:
The patent changes the viscosity parameter from conventional apparent viscosity to extensional viscosity in the capillary number calculation. This allows accurate prediction of Sor reduction using extensional rheological properties that can be optimized independently of shear viscosity, potentially resolving the injectivity-Sor reduction trade-off
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
This approach allows for the selection of optimal polymers and improves the prediction of residual oil saturation reduction, overcoming the limitations of conventional methods by accurately accounting for viscoelastic effects, leading to enhanced oil recovery efficiency.
Implementation Method 1
residual oil by definition is the oil that is swept well by the displacing water but that failed to become mobilized due to high interfacial tension (IFT) between the water and oil
Implementation Method 2
Capillarity will be higher when the IFT is high. Smaller pore radius also leads to higher capillary forces
Implementation Method 3
The interplay between the viscous and capillary force has been well described by the dimensionless number called capillary number (Nc). Generally, oil will be trapped at the capillary pressure of 1000 psi/ft while the viscous force is of the order of few psi/ft
Implementation Method 4
In recent times, viscoelastic polymer flooding was reported to cause an increase in Sor reduction
Implementation Method 5
The method calculates an extensional capillary number (Nce) using flux, pore-scale apparent viscosity, and interfacial tension to account for the polymer's viscoelastic forces
Data Source
AI summary
A method of quantifying a viscoelastic effect of a polymer on residual oil saturation (Sor) including calculating an extensional capillary number (Nce) using flux, pore-scale apparent viscosity, and interfacial tension to account for the polymer's viscoelastic forces that are responsible for Sor reduction. The polymer is used polymer flooding during enhanced oil recovery. An extensional capillary number is calculated for a plurality of polymer materials, which are then compiled in a database. Also provided is a reservoir simulator for predicting the Sor reduction potential of the viscoelastic polymer, which includes a database of calculated extensional capillary numbers for a plurality of polymers. The database includes a curve generated from the calculated extensional capillary numbers for a plurality of polymers properties, flux rates, formation nature, oil viscosities, and rheological behaviors.