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Mobility Control in Surfactant Floods: Improving NAPL recovery by in-situ control of viscosity

Dick JacksonINTERA Inc., Austin, Texas

EPA NAPL Seminar, ChicagoDecember 11, 2002

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Mobility Control

The term refers to controlling the viscosity, and subsequently, the direction of flow of injected fluids in heterogeneous oil reservoirs

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Mobility Control

Mobility ratio:mobility of NAPL ÷ mobility of injectate

Where mobility = µj ÷ keff, j

If µINJ>µNAPL , there is better sweep in-situ and higher NAPL recovery

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Choice of Approaches

There are two ways of changing in-situ viscosities and thereby overcoming the effects of heterogeneities1. Surfactant-Foam flooding2. Surfactant-Polymer flooding

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1: Foam Flooding

Surfactant solutions foam when air is injected into them

In-situ this forms a high viscosity and therefore stationary environment in the high perm zones,

Foam is temporary & reversible

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1: Foam Flooding

Sequential injection of slugs of first surfactant solution then air cause temporary blocking of high-perm units, i.e., low mobility, thus

Foam causes redirection of surfactant into low-perm zones

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Applications of Foam Flooding

Pilot Scale Test at Hill AFB in 1997 by INTERA and Rice University

Two large-scale Foam floods at Hill in 2001 and 2002 to remove TCE DNAPLAdvisor: George Hirasaki, Rice

University

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1997 AATDF Surfactant-Foam Flood Demonstration, OU2, Hill AFB

Cross Section Showing Growth of Foam Front, seeMeinardus et al., 2002, JCH 54:173-193

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A

B

C

Foam is produced from upper ports, DNAPL from the base

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SCADA, Flow Control, Autosampling

Mixing/InjectionOn-line GC

Electrolyte(Brine)Staging

Surfactant/Alcohol Staging

InjectionWells (3)

ExtractionWells

ExtractionWells

Wasatch Range

North South

•110 ft Divergent Line Drive•65,000 gal Swept Pore Volume

•Total Remediation Time = 35 days

Full-Scale SEAR at Hill AFB OU2, UtahDNAPL (70% TCE)

Surfactant/Alcohol Staging

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2: Polymer Flooding

Hundreds of polymer floods conducted since 1960s by the oil industry

The purpose is to maintain local hydraulic gradients and thus cause the injected polymer solution to enter low perm units

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2: Polymer Flooding

Polymer solutions have high viscosity, e.g., 5 – 20 cP, relative to the NAPL they are to displace

Polymer flooding will displace only free-phase NAPL not residual

Surfactant-polymer flooding displaces both free- and residual-phases– Advisor: Gary Pope, UT-Austin

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Mobility Control with Polymers:-allows surfactants or biostimulants to be pushed into low-k zones

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0 10 20 30 40 50

02

46

8

Horizontal Extent (ft)

Depth (ft)

0 10 20 30 40 50

02

46

8

Horizontal Extent (ft)

Depth (ft)

0 10 20 30 40 50

02

46

8

Horizontal Extent (ft)

Depth (ft)

0.0 0.2 0.4 0.6 0.8

Normalized Tracer Concentration

Permeability field for UTCHEM simulations

Progress of fluids without polymer

Progress of fluids with polymer

10 Darcy

2 Darcy

1 Darcy

Polymer induced crossflow

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Removal of Coal Tar by Surfactant-Polymer Flooding, Illinois

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Coal Tar at Manufactured Gas Plants

Coal tar may form both LNAPL [“floaters”] and DNAPL [“sinkers”]

the NAPL will probably wet the soil

most NAPL will be residual phase

remediation by waterflooding is limited by viscous fingering [µw<µNAPL]

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Characteristics of the Bloomington Site

Coal tar viscosity : 65 cP Mostly a DNAPL but some naphthalene-

rich LNAPL is also present The (aqueous) benzene concentrations

are the risk driver depth to water: 10 feet ~20-ft thick aquifer fining upward alluvium with basal coarse

sand average hydraulic conductivity ~5x10-3

cm/s

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Soil Boring Log

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50-60% coal tar recovery

85-90% coal tar recovery

Column Study Results: The Effect of Polymers

Polymer/ surfactant flood

Surfactant flood

Flo

w d

irec

tion

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Surfactant System

4% Alfoterra 123-8 PO-Sulfate 8% Secondary Butyl Alcohol 0.13% Xanthan gum biopolymer 0.08% Calcium Chloride

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0%

10%

20%

30%

40%

50%

60%

70%

0 1 2 3 4 5 6

Time (days)

Su

rfac

tan

t R

eco

ver

y

3 HC run9 run10 run11 run12

run13 run14 run15

Design simulations for different well configurations using UTCHEM

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Piezometric Surface during Floodnatural grad = 0.001imposed grad = 1.7 (60º)

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Wellfield

extractorsinjector

hydraulic control

Pore volume = 7,000 L

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Temperature History

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0

2

4

6

8

10

12

14

16

18

0 12 24 36 48 60 72 84 96

Flo

w R

ate

[L

/ min

]

Elapsed Time [hours]

Pumping Rates during the Surfactant Flood

surfactant flood post-flood

EX-1 {inboard extractor}

EX-2 {outboard extractor}

Polymer breakthrough reduces Q

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4/11

080

0

4/11

120

0

4/12

080

0

4/12

150

0

4/12

180

0

4/13

080

0

4/13

180

0

4/14

111

5

4/14

170

0

4/15

080

0

Flood begins 04/11 1000 Post-Flood begins 04/14 0300

Samples from EX-1

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1

10

100

1,000

10,000

0 12 24 36 48 60 72 84 96

Coal Tar Solubilization at Well EX-1

Elapsed Time [hours]

Sol

ubili

zed

Coa

l Tar

Con

stitu

ents

[m

g/L

]

surfactant flood post-flood

solubility enhanced by heating

ambient coal tar solubility

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4/11

080

0

4/12

000

0

4/12

080

0

4/12

120

0

4/12

150

0

4/12

180

0

4/12

202

8

4/13

120

0

4/14

030

0

4/14

170

0

4/15

080

0

Flood begins 04/11 1000 Post-Flood begins 04/14 0300

Samples from EX-2

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1

10

100

1,000

10,000

0 12 24 36 48 60 72 84 96

surfactant flood post-flood

Sol

ubil

ized

Coa

l Tar

Con

stit

uent

s [

mg/

L]

Coal Tar Solubilization at Well EX-2

Elapsed Time [hours]

ambient coal tar solubility

solubility enhanced by heating

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Coal-Tar Recovery

2,621 L free-phase by mobilization

305 L of residual by solubilization Total recovery=2,926 L

– i.e., 42% of the 7,000 L test pore volume

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Performance Assessment

Conducted by on-site contractors – [Burns & McDonnell, Oak Brook IL]

Before and after soil sampling indicated removal of – 92% of benzene and – 86% of PAHs

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SEAR is Cost Competitive

Estimate for SEAR at Bloomington:~$95 / yd3 of aquifer volume

Typical excavation/disposal costs:~$100 - $150 / yd3

(both estimates are based on excavated yardage)

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Summary

Heterogeneities in alluvium and fractured rock can be overcome by controlling the injectate viscosity1. Surfactant-foam flooding2. Polymer flooding3. Surfactant-polymer flooding

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Path Forward

Coupling Pressure Pulse Testing with surfactant-polymer flooding for creosote removal at Cape Fear NC

Use of polymer to push biostimulants or oxidants into low-perm units following surfactant flooding