capillary talk

An Investigation into the Prevention of Vertical Capillary Transport of Salt from

Brine Contamination

Carla Landrum1, J. Berton Fisher1, Eleanor Jennings2, Shoeb Munshi2, Kerry Sublette2, Bryan Tapp1 and Dan Weber1

1Department of Geoscience; 2 Department of Chemical Engineering

Center for Applied BiogeosciencesUniversity of Tulsa

Introduction• Brine:

– Produced water– Byproduct of oil production – High levels of salt

• Historic disposal occurred on surface– Prior to environmental regulations – Multiple, deliberate exposures at location

• Historic brine scar resulted

Photo Credited to the USGS

• Traditional method of remediation– Addition of amendments (organic matter

and/or gypsum) to improve permeability– Irrigation to mobilize salt

• Problem:– Does not remove salt in deep soil layers– Salt can migrate vertically via capillary

movement– Recontamination of surface soils

TOP SOIL(ROOT ZONE)

UNSATURATED ZONE

(VADOSE ZONE)

PERCHED SATURATED ZONE

TOP SOIL(ROOT ZONE)

UNSATURATED ZONE

(VADOSE ZONE)

PERCHED SATURATED ZONE

Historic wells

LEGEND

PedestalPedestal A

Pedestal CPedestal C

Pedestal BPedestal B

Photo credited to USGSPhoto credited to USGS

Observations

• Brine scar floor– Loss of vegetation– Erosion

• Pedestals– Significant plant life

Photo credited to the USGS

Question?

What allows for the growth of vegetation on top of the pedestals with significant brine contamination at the base of the pedestal?

Hypothesis

Common soil texture within pedestals that prevents vertical migration of salt upwards into plant root zone

Goals

• Define contaminated and uncontaminated zones within each soil pedestal

• Identify interval separating the two zones

Materials and Methods• Soil cores taken

– Approx. 12.5 cm intervals for total depth of pedestal (average of 134 cm)

• Major Soil Analytics– Soil Texture– Na+ and SAR

• SAR= [Na+]/{([Ca+2]+[Mg+2])/2}1/2

– Electrical Conductivity (ECs)– Boron (Weber, et al. 2005)

Photo is not to scalePhoto credited to the USGS

PedestalA1 10 100 1000 10000

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Incr

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% Sand % Silt % Clay

Soil Texture

(μmhos

Boron (ppm) x 5000Na (ppm)Ec /cm)

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Pedestal BIn

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Increments are as Indicated

% Sand % Silt % Clay

Soil Texture(μmhos

Boron (ppm) x 5000Na (ppm)Ec /cm)

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Pedestal C

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% Sand % Silt % Clay

Soil Texture(μmhos

Boron (ppm) x 5000Na (ppm)Ec /cm)

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ControlIncrements are as Indicated

% Sand % Silt % Clay

Soil Texture(μmhos

Boron (ppm) x 5000Na (ppm)Ec /cm)

Pedestal ECs/% Sand

ECs/% Clay

SAR/% Sand

SAR/% Clay

A -0.84 0.42 -0.81 0.87

B -0.87 0.87 -0.86 0.92

C -0.86 0.89 -0.94 0.97

Correlation coefficients in red are statistically significant at p<0.05

Correlation of ECs and SAR with Soil Texture at Skiatook A

Study Expanded

• Historic brine scars in Tallgrass Prairie Preserve in northern Osage County– S1 and S3– Clearly visible in aerial

photographs from 1937

– Sampled pedestals and erosion bluffs

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Depth (m)

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70%

Cla

y

Clay Skia Clay S1 Clay S3

Clay Content Variation with Depth

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% Clay

0

5

10

15

20

25

30

35

40EC

(mm

hos/

cm)

EC-Skia EC S1 EC-S3

ECs Variation with % Clay

0 10 20 30 40 50 60 70 80

% Sand

0

5

10

15

20

25

30

35

40EC

(mm

hos/

cm)

EC-Skia EC S1 EC-S3

EC Variation with % Sand

0 10 20 30 40 50 60 70

% Clay

0

5

10

15

20

25

30

35

40EC

(mm

hos/

cm)

EC-Skia EC S1 EC-S3

ECs Relative to Plant Growth

Negligible effects

Sensitive plants affected

Many plants

affected

Only salt tolerant plants

Only very salt

tolerant plants survive

SAR Variation with % Clay

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% Clay

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20

40

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SAR

SAR-Skia SAR-S1 SAR-S3

0 10 20 30 40 50 60 70 80

% Sand

0

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40

60

80

100

120

140SA

R

SAR-Skia SAR-S1 SAR-S3

SAR Variation with % Sand

SAR and Sodicity

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% Clay

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SAR

SAR-Skia SAR-S1 SAR-S3

Sodic

Conclusions

• Relationship between capillary movement of salt and soil texture is somewhat site specific

• These results suggest that significant vertical movement of salt in the soil column is prevented when % Sand > 60% and % Clay is < 10-15%

TOP SOIL

UNSATURATED ZONE

(ROOT ZONE)

VA

DO

SE

ZO

NE

Na+ Na+ Na+ Na+Na+ Na+

Capillary Break

PERCHED SATURATED ZONE

Project Significance

We have identified a common soil texture that inhibits the vertical migration of salt upwards into

a plant root zone.

This is a preliminary step towards a solution that prevents brine recontamination.

Acknowledgements

• Integrated Petroleum Environmental Consortium (IPEC)

• The University of Tulsa – Center for Applied Biogeosciences

• United States Geological Society (USGS)