Remediation of Oilfield Brine-impacted Soil Using a Subsurface Drainage

System and Hay

Thomas M. HarrisDept. of Chemistry and Biochemistry

J. Bryan TappDept. of Geosciences

Kerry L. SubletteCenter for Applied Biogeosciences

University of Tulsa

Remediation Strategies for Brine Spills

• Goal is reduction in salinity and revegetation• Most cost-effective approach is gradual leaching of salt

and dilution over a large area using natural drainage patterns and organic matter

• Organic matter– Enhances movement of brine components through the soil– Stimulates soil biota and nutrient cycling which aids in

revegetation– Biodegradation of organic matter improves soil structure by

enhancing aggregate formation which in turn improves soil permeability

• Brine components must have a pathway through which to migrate out of the root zone for revegetation to occur

• What if there is no safe place to drain leachate?

Carter Site (site B)

• Rupture of a salt water linein December 1995 inOsage County, OK; about400 bbl and two acresimpacted

• Underlying clay layer atabout 3 ft

• Site drained to a farmpond 600 yds away

Site History and Description

• Rupture of a salt water line in December 1995 in Osage County, OK– about 400 bbl of brine (130,000 mg/L TDS)– two acres impacted

• Topsoil silt loam; underlying clay layer at about 3 ft• Site drained to a farm pond 600 yds away• Significant impact on aquatic life in the pond

Treatment # Salt Away II Adsee 799 sulfur fertilizer hay FW

1 105 L / 4.8 m3 FW 19 L / 1.0 m3 FW

2 105 L / 4.8 m3 FW

3 136 kg 11 kg 65 bales

6.1 m3

4 38 L / 2.1 m3 FW

(Salt Away II: commercial calcium nitrate solution; Adsee 799: commercial wetting agent solution; fertilizer: 10-20-10-7 pellets; hay: small rectangular bales; FW = fresh water)

Remediation Treatments Applied to Site BTwo Months After the Brine Release

All treatments included ripping to 30 cm in depth

After 3 growing seasons site still bare.

August 1995

Remediation Protocol

• Drainage was a major issue• Installed subsurface drains above clay layer in January

1998– French drain pipe in limestone gravel bed– Drained to sump (25 bbl steel tank)– Operator pumped leachate to salt water storage tank each day

• Installed berms downgradient of each subsurface drain to increase penetration of rainfall into the soil

• 4-inch layer of hay tilled in after installation of SDS except in NW corner (too wet at time of tilling)

• Rainfall only source of moisture

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Depth (cm)

L1, ChlorideL1, SodiumL2, ChlorideL2, SodiumC, ChlorideC, Sodium

Sampling Dates2/983/997/005/01

Sampling Dates2/983/997/005/01

Follow-up Treatment of L1S1 and L1S2

• No revegetation after first growing season• L1S1 treated with gypsum (API Guidelines) and tilled• L1S2 covered with 4 inch of hay and tilled• Observations:

– Faster sodium removal with hay– Faster revegetation with hay – section with hay was

two years ahead of the section treated with gypsum

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Soil Sodium Concentrations (mg/kg) Hay and Gypsum Test Sections

Hay

Gypsum

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Soil Chloride Concentrations (mg/kg) Hay and Gypsum Test Sections

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Gypsum

Leachate Characteristics – First 6 Months

• About 7000 bbl collected• Salt concentrations 1000-1700 mg/L

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Early spring 1998

Late spring 1999; good crop of ragweed, some bare spots still

Spring 2000; lots of ragweed but lots of grasses too!

Spring 2002; buffalo now graze here!

Remediation Cost

• $3,500/acre• Cost inflated by:

– Replacement of sump tank– Weather-related construction delays– High-integrity bison fence– Above accounted for at least half the cost

RecommendationsTwo-stage process:• Stage 1

– Use natural drainage patterns to convey and dilute salt– Organic matter (and fertilizer) in improve permeability and

build soil structure– Monitor downgradient

• Stage 2 – Leachate has no acceptable path or Stage 1 does not work

completely– No acceptable path – subsurface drainage system and

leachate collection– Stage 1 does not work completely – use limited gypsum

application to address sodicity

Why Limit Gypsum?

• Yes, gypsum displaces bound sodium from clay particles

• Gypsum also interferes with phosphorous cycling in the soil

• Large applications can have drastic effect on the soil ecosystem

• Effects of gypsum occur primarily throughout the depth incorporated; the effects of plant growth occur throughout the root zone

ACKNOWLEDGEMENTS

• We thank The Nature Conservancy for access to the site

• Funded by the National Energy Technology Office of U.S. Department of Energy and Carter Oil Co.