Presentation Identifier (Title or Location), Month 00, 2008

Design and Rationale for a Field 

Experiment using Tracers in Hydraulic 

Fracture Fluid

Daniel J. Soeder, NETL

Morgantown, WV

USEPA Technical Workshop, March 10-11, 2011

Well Construction and Operations
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Marcellus Shale in Hanson Quarry, NY

Oatka Creek Member

Cherry Valley LS

Union Springs Member
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Appalachian Basin Stratigraphy
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Hydraulic Fracturing

• Hydraulic fracturing is used to create high-permeability pathways into a 

formation.

• Hydraulic fractures are made by filling the well with fluid and then 

increasing the pressure until the rock strength is exceeded.

• Fluid and proppant are pumped out into the fractures; the proppant stays 

behind and keeps the fractures open after pressure is released.
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Potential for Aquifer Contamination

• Does the frac fluid get into shallow, 

freshwater aquifers (USDW) when 

under pressure creating the fractures?

• Unlikely because of:

– Low hydraulic conductivity

– Flow gradients wrong direction

– Depth of target formation

– Long groundwater travel times

• What if there are flow conduits to the 

surface like faults or abandoned wells?

• No definitive evidence of direct water 

contamination from deep hydraulic 

fracturing has been documented, but a 

tracer test would help provide rigorous 

data. 
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Formation Water Chemistry

• Fluid recovered from the well after the frac is called flowback.

– Mix of frac water and formation water – how much of each?

– Starts fresh, then turns very salty with high TDS and odd chemistry

– Only about 1/4 - 1/3 of the injected fluid is recovered as flowback

• What happens to the frac fluid that remains downhole?

– Pools in the bottom of fractures?

– Evaporates and is transported out with the gas?

– All of the above?

– None of the above?

• Source of the TDS, and links between brine chemistry and bulk 

rock geochemistry of shale are not well understood.

• Relationship of Marcellus water chemistry to other waters in the 

basin (i.e. Oriskany) is not well understood either. 
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What is a Tracer?

• Tracers are elements, compounds, or isotopes that can be used 

to delineate groundwater flow paths and estimate time-of-travel 

(USGS). 

• Environmental tracers: anthropogenic compounds that entered 

into the hydrologic cycle at a known time and concentration

– CFCs, sulfur hexafluoride (SF6) from atmosphere

– Tritium/helium-3, chlorine-36, other radionuclides from aboveground weapons testing in the 1950’s (spikes)

• Introduced tracers: dyes, chemicals, or isotopes added for a test

– Conservative tracers travel with the plume; non-conservative 

tracers may diffuse or disperse out ahead of it.

– An ideal tracer is easily detectable, obvious, moves with the water 

flow, does not chemically react with passing substrates, and does 

not alter the properties of the water. 
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Proposed Hydraulic Fracture Tracer Test

• Collect baseline data on site 

groundwater, structure and geology.

• Drill parallel laterals at site and 

prepare for frac.

• Add a conservative tracer in the frac 

fluid mix; place instruments on-site

• Hydraulically fracture the wells in the 

normal manner.

• Monitor frac physics and sample 

groundwater for tracer.

• Drill a vertical well to the Oriskany

some time after frac.

• Sample formation water all the way 

down to and including the Oriskany 

Sandstone.

• Run lab analyses of groundwater 

and formation water to determine 

fate of frac fluid from detection of 

tracer.

• Government control of design, 

sampling, analysis and data, with 

other selected participants (industry, 

university, etc.) following same QA.

• Security is required to protect sample 

sites and data integrity (more QA).

• Status: site and alternate sites 

identified, driller agreeable but 

service company not approached, 

interagency collaborators identified 

(USGS, EPA)

• Sites: NETL-Morgantown, locations 

near Waynesburg, PA, possible 

central WV locations.
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DOE NETL Site, Morgantown, WV
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EGSP WV-6 Well and Core (MERC#1) 
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Site Issues

• NETL: Management has not confirmed support; not sure 

how facilities/safety people will react, may be difficulties 

with pipeline capacity to take gas.

• NETL: One landowner has control of land, site is 

secured with fence and guards, oriented properly, old 

Marcellus well for stratigraphic control.

• Waynesburg: Multiple landowners, may be denied 

access, unsecured sites near interstate highway, 

schedule moving rapidly.

• Waynesburg: more timely, leases and permits in place 

and gas lines in area, existing water wells, multiple 

landowners might be a good thing for options.
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Cost (Guess)timates

• Drill the vertical wells to kickoff, drill the laterals, case, perf, zipper 

frac, complete: ~$4 million; industry cooperator will cover these 

costs in return for the gas.

• Install groundwater monitoring wells and surface or downhole 

geophysical instrumentation: $300K

• Construct a vertical well from surface to Oriskany Sandstone, 

including ~100 ft of Marcellus core: $800K

• Interagency funds for selecting tracer, monitoring frac, collecting 

samples: $250K

• EPA, USGS laboratory analysis of water samples: $300K

• Analysis of other data (geophysics, soil gas, etc.): $250K

• Assessing results and writing/publishing report: $100K

• Total estimated government cost for one field experiment: $2 mill
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DOE Marcellus Tracer Test

Goals

Assess environmental impacts to aquifers.

Address scientific issues related to 

hydrology and geochemistry

Outcomes

Rigorous study with well-documented 

data, solid QA pedigree, no question 

about data integrity.

Applications

Provide public information to help 

regulators, and create a more informed 

environmental debate.

Benefits

Improve understanding of hydraulic 

fracture injection and downhole

movement.

Document formation water chemistry and 

links to Marcellus brine.