Considerations for

Fate and Transport Evaluation

Of Potential Release Scenarios 

during Hydraulic Fracturing Operations

EPA Hydraulic Fracturing 

Technical Workshop 

on Fate and Transport

March 28-29, 2011 
Set up a Site Conceptual Model
To Production Zone (thousands of feet)

Not to Scale

Drilling

& 

Operations

Conductor 

Casing

Surface Casing

Groundwater

Groundwater Protected

through Well Design 

and Testing

Groundwater Protected 

through Primary and 

Secondary Containment

Distance to

Water Supplies Considered

Water Well

Surface Water

Shot Hole

Properly Abandoned

Intermediate 

Casing

Production Casing, Production Tubing, and Associated Protections

Closed Mud 

System

Consider likelihood of Event
Depth to Useable

Groundwater

(10s to 100s feet)

Depth to LimitedUse Groundwater

(10s to 1,000s feet)

Depth to NonUseable Groundwater

(10s to 10,000s feet)

Depth to Gas 

Producing Formations

(1,000s to 10,000s of feet)

Useable Groundwater 

Limited-Use Groundwater 

(Quality & or Quantity)

Non-Useable Groundwater

(Quality & or Quantity)

Non-Useable Groundwater 

(Quality & Quantity)

Depth to NonUseable Groundwater

(10s to 10,000s feet)

Non-Useable Groundwater 

(Quality & or Quantity)

- 0 feet

- 100 feet

- 1,000 feet

- 10,000 feet

50,000 gal 

leak displacement

(equivalent to a sphere 

of about 18.5 ft radius)

50,000 gal 

leak displacement

Potential Total Volumes from HF are Limited

And Starting Concentrations are Low.
Consider Potential Chemicals of Concern 

for Hydraulic Fracturing

Additives (Low starting concentrations) 

Salts, organics, metals, 

Produced water (actually not part of HF process) 

Salts, organics, metals, 
Methods for Examining Potential Produced 

Water Impacts are Available
Geochemical methods use common water chemistry parameters to identify mixing 

of saline and potable water. 

Parameters of interest may include: Na, K, Ca, Mg, Cl, SO4, Co3, HCO3, TDS, Br, I, etc. ,

and take advantage of potentially great differences between the makeup of saline and

potable water.

For example, a large database of produced water (fractionation water base) and well waters from

an area show their distinct character when comparing various parameters. (Note: These 

plots show data from hundreds of samples from throughout a large area. Focusing on 

specific locations, depths, etc. may likely show more separation of the produced water and well water.)

By evaluating the differences between waters, appropriate parameters or combinations may be

selected for evaluation of potential mixing.

Average ≈ 5,400 mg/L

Average ≈ 20 mg/L

Average ≈ 9,700 mg/L

Average ≈ 5,300 mg/L

Average ≈ 400 mg/L

Average ≈ 140 mg/L
Produced Water Well Water

Piper plots of major ions is another way 

of showing distinct chemical types of water.

Produced waters (used to makeup fractionation water) have a fairly tight 

geochemical fingerprint, while well waters are generally different than produced 

water and variable in composition. Note that these diagrams represent water 

type, not concentrations. 
Anions Cations

Na + K

Mg

Ca

SO4

HCO3 + CO3

Cl

100% PW

Anions

Na + K

Mg

Ca

SO4

HCO3 + CO3

Cl

100% WW

Cations

Anions

Na + K

Mg

Ca

SO4

HCO3 + CO3

Cl

1% PW inWW

Cations

Anions

Na + K

Mg

Ca

SO4

HCO3 + CO3

Cl

5% PW inWW

Cations

Anions Cations

Na + K

Mg

Ca

SO4

HCO3 + CO3

Cl

20% PW in WW

Stiff Diagrams of major ions indicated the general chemistry of waters and mixtures. 

These may be used to indicate water type visually and relative concentrations.

Water Well (WW)

Produced Water (PW)
BIODEGRADATION HALF LIFE IN SOIL

Half Life Increases

with Molecular Weight

and Complexity

Half Lives for BTEX 

compounds are on the

order of one month
METALS

Solid (Soil)

Phase

Aqueous (Water)

Phase

Petroleum (Oil)

Phase

EL

ML

Pb

Pb

Pb

Pb

PbSO4

Pb

Pb

X

X X

X X

X X

Mineral Lead

Occluded (Trapped)

Lead

Soil Surface

OH

O -

Soil Organic Matter ( Humics)

Dissolved

EL or ML

(Ethyl or Methyl Lead)

Inorganic 

Lead

Species

Exchanged Lead

Precipitated Lead

Soluble Lead

Adsorbed Lead

OrganicallyComplexedLead

Organic

Lead

Pb

PbSO4

PbS

PbCl2

PB(CO3)(Cl)2

PbCO3

PbO

Pb5(AsO4)3Cl

Pb2OCO3

PbSO4O

Pb2O2SO4

Pb4O3SO4

Pb3(AsO4)2

Minerals

Pb+2

PbCl2(aq)

PbCl3

-

PbCl4

-2

Pb(CO3)2

-2

Pb(OH)+

Pb4(OH)4

+4

Pb6(OH)8

+4

PbCl+

PbHCO3

+

PbCO3(aq)

Pb(OH)2(aq)

Pb(OH)3

-

Pb2OH+3

PbSO4(aq)

Pb(HS)2(aq)

Pb(HS)3

-

Pb3(OH)4

+2

Pb(OH) -2

Pb(SO4) -2

Pb+2

Soluble

Pb(OH)2

PbSO4

PbCO3

PbS

Precipitates

Species and Interactions

Previous Work indicate that Metals from O&G

Materials are Immobile if Released to Soil.
MINTEQA2, HSC3

0 2 4 6 8 1 0 1 2 1 4

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

Pb - Cl - H2O - System at 25.00 C

File: C:\HSC3\PBCL25.IEP pH

Eh (Volts)

Pb

PbCl2

PbO

PbO2

Pb3O4

Pb(+2a) Pb PbO PbCl2

PbO2

Pb2O3

Pb3O4 Pb(OH)2

Pb(+2a) PbCl2(a)

Pb3(OH)4(+2a)

Pb4(OH)4(+4a)

Pb6(OH)8(+4a)

•Useful for forward modeling (Tier 2).

•Data limited for reverse modeling.

•May be linked to transport model.

•May incorporate sorption.

•Use to establish system boundaries.

PbCl2 H2O

METALS
Natural parameters are preferable to frac fluid additives for evaluating potential

salt water influences because of variety of additives, variety of analytical procedures,

natural presence of some constituents, and detection limit constraints.

For example, an www.energyindepth.org reference summarizes a typical frac fluid 

(http://www.energyindepth.org/frac-fluid.pdf).

From that data, estimate possible levels of some components at a 0.5% produced water 

mixture with well water:

mg/L at 0.5% mg/L Detection Limit 

Component PW in WW for component Detectable

citric acid 0.2 1 No

ethylene glycol 2.2 10 No

n,n-dimethyl formamide 0.1 0.1 Maybe

gluteraldehyde 0.05 1 No

isopropanol 4.3 0.01 Yes 

petroleum distillate 4.4 0.001 (xylene) Yes (at 0.2% Xyl)

Note that in this case two of the chemicals are potentially detectable at a level equivalent

to standard inorganic parameters. Of these isopropanol is a natural component and may

degrade prior to sampling and analysis or be present in background, while petroleum 

components are already commonly analyzed. Such evaluation must be done for each

component considered.
2

 

4

 

4

1 1

2

exp 

x

S

erf

x

S

erf x RDF

C

C

z

d

y

x w

x

sat

x

s

where:

•Cx= dissolved component at a distance x from the source (mg/L)

•x = horizontal distance to point of extraction (cm)

• = first-order degradation constant (day-1)

•R = constituent retardation factor(dimensionless)

• = specific discharge (cm/day)

• x= longitudinal dispersivity (cm)

• y= transverse dispersivity (cm)

• z= vertical dispersivity (cm)

•Sw= source width (cm)

•Sd= source depth (cm)

Domenico Equation
Figure 2. Distance to 1.56 mmhos/cm (1,000 mg TDS/L)

with Various Source Concentrations

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300

Source Width (ft)

Distance Downgradient (ft)

Soil EC = 400 mmhos/cm

GW EC = 24 mmhos/cm

Soil EC = 320 mmhos/cm

GW EC = 16 mmhos/cm

Soil EC = 240 mmhos/cm

GW EC = 12 mmhos/cm

Soil EC = 200 mmhos/cm

GW EC = 10 mmhos/cm

Soil EC = 160 mmhos/cm

GW EC = 8 mmhos/cm

Soil EC = 80 mmhos/cm

GW EC = 4 mmhos/cm

Soil EC = 31 mmhos/cm

GW EC = 1.56 mmhos/cm

Source Concentrations

Figure 2. Distance to 1.56 mmhos/cm (1,000 mg TDS/L)

with Various Source Concentrations

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250 300

Source Width (ft)

Distance Downgradient (ft)

Soil EC = 400 mmhos/cm

GW EC = 24 mmhos/cm

Soil EC = 320 mmhos/cm

GW EC = 16 mmhos/cm

Soil EC = 240 mmhos/cm

GW EC = 12 mmhos/cm

Soil EC = 200 mmhos/cm

GW EC = 10 mmhos/cm

Soil EC = 160 mmhos/cm

GW EC = 8 mmhos/cm

Soil EC = 80 mmhos/cm

GW EC = 4 mmhos/cm

Soil EC = 31 mmhos/cm

GW EC = 1.56 mmhos/cm

Source Concentrations Domenico Equation Applied to Salt Transport

18.5 ft – Approx. soil volume of 50,000 gal release.
Tools are available for evaluating the fate and transport of selected 

reasonable release scenarios in hydraulic fracturing operations. 

These methodologies consider controls in the hydraulic fracturing 

process as reflected in existing regulations and best management 

practices before selecting scenarios. 

This process will allow focusing on realistic release scenarios, 

chemicals, pathways, and receptors.

Background chemicals, both anthropogenic and natural, must be 

considered in any analysis. 

Tools must be used that are appropriate for uncertainty in available 

data and analytical techniques. 

Consider previous work that showed oil field waste to be high volume 

and low toxicity, i.e. produced water,

drilling mud.