Studies on the Characterization, Interfacial Tension and Rheology of a Novel Polymeric

Surfactant Derived from Castor Oil for Enhanced Oil Recovery

Presented by: Nilanjan Pal

Adm. No. 2013MT0087

M.Tech (2nd Year)

Under the Guidance of-Dr. Ajay MandalAssociate ProfessorDeptt. Of Petroleum Engg.ISM, Dhanbad

Introduction

Traditional oil extraction methods produce 20 to 40% OOIP

Remaining oil is still trapped in porous media resulting in poor

displacement efficiency

This revelation has led to the application and development of many

Enhanced Oil Recovery methods.

EOR processes involve a variety of mechanisms, including use of

polymers and surfactants that alter the properties of reservoir fluids

Potential possibilities in the application of a new polymeric surfactant

Polymer Injection improves mobility ratio and sweep (displacing) efficiency

Surfactant flooding reduces oil-water interfacial tension and improve oil

recovery.

Polymeric surfactant, synthesized by the appropriate mixing of polymer

and surfactant, encompassed the beneficial effects of both polymer and

surfactant flooding with cost-effectiveness

Proper formulation (grafting of the sulfonate group to acrylamide group) is

necessary to avoid undesirable phase separation

Work Overview

Study of FTIR Characterization

DLS experimental investigations by using ZetaSizer (DLS apparatus)

Interfacial Tension measurements by using Spinning Drop Tensiometer

Rheological studies (Viscosity and Viscoelasticity) by using Rheometer

Polymeric Surfactants with different acrylamide-to-sulfonate ratios

Acrylamide-to-sulfonate Ratio 0.4:1 0.5:1 0.6:1 0.8:1 1:1

Notation P1 P2 P3 P4 P5

FTIR Characterization

Resultant absorption (transmittance) spectrum in IR region obtained from FTIR analysis indicates the presence of various chemical bonds and functional groups.

Different polymeric surfactants with varying acrylamide-to sulfonate ratio were characterized by FTIR.

The IR spectra recorded for all synthesized polymeric surfactants showed similarity in the pattern of infrared spectrum with different transmittance percentages.

Identified presence of ester, sulfonate, amide, methyl and acrylamide groups.

DLS Characterization

One of the most techniques employed for the determination of average particle size and distribution in aqueous solutions.

Works by measuring the intensity of light scattered by the molecules in the sample as a function of time.

DLS measures Brownian motion and relates this to the size of the particles.

The diameter that is measured in DLS is a value that refers to how a particle diffuses within a fluid so it is referred to as a hydrodynamic diameter.

By measuring the time scale of light intensity fluctuations, DLS provides information regarding the average size, size distribution, and poly-dispersity of molecules in solution.

Results- Effect of Concentration

Hydrodynamic diameter increases with increasing PMES concentration

This is due to the aggregation of molecules as PMES concentration is increased

3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 85000

500

1000

1500

2000

2500

3000

P1 P2 P3 P4 P5

PMES Concentration (ppm)

Hydr

odyn

amic

Diam

eter

(nm

)

Fig. Effect of PMES concentration on particle size distribution profile

Results- Effect of Salt addition

3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 85000

200

400

600

800

1000

1200

1400

1600

P1 (2% NaCl) P2 (2% NaCl) P3 (2% NaCl) P4 (2% NaCl)

P5 (2% NaCl)

PMES Concentration (ppm)

Hydr

odyn

amic

Diam

eter

(nm

)

Fig. Effect of salt addition on particle size distribution profile (2%)

Hydrodynamic diameter was generally found to decrease with increase in salt (concentration) addition since micelles may disaggregate to smaller size and may even break down acrylamide chains.

Phenomenon of rolling up of CMC segments in aqueous salt solutions, thereby changing particle structure from rod-like to spherical shape. As a result, the size of micelles becomes smaller. This could help decrease the surface tension and interfacial tension

Interfacial Tension Studies

A droplet of crude oil is injected into a surfactant solution (higher density) contained inside a rotating horizontal capillary glass tube

Rotation of the horizontal tube creates a centrifugal force towards the tube walls, the liquid drop will start to deform into an elongated shape

Drop attains a stable shape when the interfacial tension and centrifugal forces are balanced

A device for such measurements is “Spinning Drop Tensiometer”

Experimental setup for Spinning Drop Tensiometer

Result- Effect of Concentration On IFTEffect of concentration on IFT of polymeric surfactant (PMES) solutions with different acrylamide-to-surfactant ratios

3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 80000

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

P1 (0.4:1) P2 (0.5:1) P3 (0.6:1) P4 (0.8:1) P5 (1:1)

Acrylamide-to-Sulfonate Ratio

Inte

rfac

ial T

ensio

n (m

N/m

)

IFT values found to decrease with concentration, and after that particular concentration, it begins to increase slightly. This is called Critical Micelle Concentration (CMC).

CMC values of P1, P2, P3, P4 and P5 were 6500 ppm, 5500 ppm, 5500 ppm, 4500 ppm and 4500 ppm respectively.

Lowest IFT value obtained was 0.0352 mN/m for P5 solution at 4500 ppm.

Result- Effect of salt addition

Fig. Effect of NaCl addition on the most effective polymeric surfactant solution

0 1 2 3 4 5 60

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

NaCl Concentration (%)

Inte

rfac

ial T

ensio

n (m

N/m

)

Interfacial tension decreased with salt addition

IFT values found to decrease with concentration, and after that particular concentration, it begins to increase slightly.

Optimal salinity was measured at 4.5% NaCl concentration with IFT value of 0.000432

This combined effect of salt and polymeric surfactant in crude oil-water systems is the synergistic effect.

Rheological Studies

Rheometry is a powerful technique for the measurement of complex shear rheology across all material types

Sensitive enough to measure the viscosity of dilute polymer solutions, and yet robust enough to measure the viscoelasticity of high modulus polymers or composites

Viscometric and oscillatory mode measurements were carried out using cup and bob (coaxial cylinder) measuring system.

Force exerted by fluid sample (in the vertical gap between bob and cylinder ~0.5 µm) measures the shear stress and viscosity with shear rate.

Oscillatory mode is useful in determining both elastic and viscous characteristics when undergoing deformation.

Experimental setup

Result- Effect of Temperature on Viscosity

Fig. Effect of Temperature on PMES viscosity at 2500 ppm

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.20

0.005

0.01

0.015

0.02

0.025

298 K313 K333 K

Acrylamide-to-Surfactant Ratio

Visc

osity

(Pa.

s)

ν= 80 s-1

Viscosity was found to decrease with temperature for all polymeric surfactants.

With temperature rise, increased velocities of individual molecules causestime period of contact between the neighboring molecules to reduce and as a result, cohesive forces are decreased.

Result- Effect of Temperature on Viscosity (Cont’d)

The dependence of temperature on the viscosity of the polymeric surfactant is explained by Arrhenius equation.

η = A exp (ΔEη / RT)

ln η and temperature reciprocal shows a straight line relationship with a slope of (ΔEη/R) measured at 80 s-1 shear rate.

The viscous activation energies for different polymeric surfactants were calculated from the slopes of the straight lines.

Values of activation energies for P1, P2, P3, P4, P5 solutions were found to be 12.70, 14.37, 15.81, 16.53 and 17.49 kJ/mol respectively.

Greater the value of activation energy, higher is the influence of temperature on viscosity.

0.00295 0.003 0.00305 0.0031 0.00315 0.0032 0.00325 0.0033 0.00335 0.0034 0.003452

2.5

3

3.5

4

4.5

P1 P2 P3 P4 P5

I/T (K-1)

ln η

Result- Effect of Concentration on Viscosity and Shear Stress

1 10 100 10000.001

0.01

0.1

1500 ppm 3000 ppm 4500 ppm 6000 ppm

Shear rate (1/s)

Visc

osity

(Pa.

s)

Fig. Experimental Steady shear viscosity profile of P5 solution (with acrylamide-to-sulfonate ratio 1: 1) at 298 K at varying concentrations

0 50 100 150 200 250 3000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

1500 ppm

3000 ppm

4500 ppm

6000 ppm

Shear Rate (1/s)

Shea

r Str

ess (

Pa)

Fig. Experimental Steady stress profile of P5 solution (with acrylamide-to-sulfonate ratio 1: 1) at 298 K at varying concentrations

Result- Effect of Concentration on Viscosity and Shear Stress (Cont’d)

Viscosity and shear stress were found to increase with concentration of the polymeric surfactant in aqueous solution.

Viscosities of solutions were also found to increase with increasing acrylamide-to-sulfonate ratios due to their increased hydrodynamic volume which has the twin effect of blocking the motion of solvent molecules and retarding their motion by binding.

Polymeric surfactant solutions showed Newtonian behavior upto 50 s-1 (critical shear rate) after which it exhibits pseudoplastic or shear thinning properties.

P5 permits better mobility control and greater sweep efficiency than other polymeric surfactants during displacement and recovery processes

Result- Viscoelastic Properties

Effect of concentration on dynamic viscoelasticity

0.1 1 10 100 10000.0001

0.001

0.01

0.1

1

10

100 G' 1500 ppm G'' 1500 ppm G' 3000 ppm G'' 3000 ppm G' 4500 ppm G'' 4500 ppm G' 6000 ppm G'' 6000 ppm

Angular Frequency (rad/s)

G' &

G''

(Pa)

Viscoelastic properties represented by storage modulus G' and loss modulus G'' increased with increasing PMES concentration.

A crossover point (specific frequency) was found for G' and G'' of each polymer surfactant solution.

The value of specific frequency signifies the point of transition between the elastic phase and viscous phase.

G'' was higher than G' when angular frequency was less than SF and vice-versa

Summary

FTIR characterization was useful in finding the chemical functional groups present in the polymeric surfactant.

DLS experiments were instrumental to determine the average particle size of polymeri surfactants in aqueous solutions.

Measurements were obtained in a spinning drop tensiometer with an aim to reduce interfacial tension to improve oil recovery.

Rheological investigations were made to understand the flow behavior (viscosity, shear stress and viscoelasticity) of the polymeric surfactant.

The data obtained is very useful for the formulation of effective salt-polymeric surfactant mixtures for improved oil recovery by mechanism of interfacial tension reduction and desired mobility control.

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