An oil and gas operator collaborated with a service company to use bi-fuel fracturing pumps powered by natural gas to lower emissions during hydraulic fracturing operations. The operator supplied natural gas from existing pipelines to power 14 bi-fuel pumps, saving over $475,000 in fuel costs compared to diesel. Using natural gas also reduced the environmental footprint and eliminated the need for 16 diesel deliveries. The collaboration helped the operator achieve one of the cleanest shale gas completions in North America while improving efficiency.

1. World Oil / MARCH 2014 99
GreenercompletionsadvanceintheMarcellus
REDUCED EMISSION COMPLETIONS
Fracing operation underway in the
Marcellus region of rural Pennsylvania. The
use of bi-fuel fracing pumps reduced the
environmental footprint. Photo courtesy of
Cabot Oil & Gas.
An operator and service
company collaborate to
lower emissions and boost
efficiencies during hydraulic
fracturing operations through
the use of bi-fuel fracing
pumps and greener frac
fluids.
ŝŝ JERAMIE MORSCHHAUSER, Cabot Oil &
Gas Corporation; SEAN PARKER and BRIDGET
TODD, Baker Hughes
In the ongoing push to maximize pro-
duction at minimal environmental impact
and expense, oil and gas companies are
searching for more efficient and cleaner
E&P technologies that help achieve these
goals. At North American wellsites, this
search has led to a growing interest in en-
gines for drilling rigs and frac pumps that
are powered, in part, by natural gas. Bi-
fuel or dual-fuel engines use a combina-
tion of diesel fuel and natural gas—which
is abundant, relatively inexpensive and
clean—to help operators lower their op-
erating expenses and the environmental
footprints.
Cabot Oil & Gas has successfully used
bi-fuel engines on drilling rigs in its Mar-
cellus shale assets, and realized economic
and environmental benefits in its drilling
operations. Cabot wanted to extend these
benefits to its hydraulic fracturing opera-
tions by utilizing bi-fuel-powered pumps.
BI-FUEL ENVIRONMENTAL
DRIVERS
Like many operators, Cabot views in-
creased implementation of bi-fuel engines
as a way to satisfy the industry’s need for
greener completions. The term refers
to methods that minimize the release of
greenhouse gases and volatile organic
compounds (VOCs) during the comple-
tion phase of a well, by limiting the expo-
sure of the produced gas to the environ-
ment by capturing and injecting it into the
sales line, rather than flaring.
Much of the drive for green comple-
tions comes from increased regulations at
both the federal and state levels. As part of
the Clean Air Act, the U.S. Environmen-
tal Protection Agency (EPA) has adopted
multiple tiers of air emission standards for
non-road diesel engines. Most recently,
EPA has introduced a national program
aimed at reducing engine emissions by
integrating engine and fuel controls, as
a system, to gain the greatest emission
reductions. These Tier 4 emission stan-
dards will require engine manufacturers
to decrease exhaust emissions by more
than 90%, by producing engines with
advanced emission control technologies
similar to those already in place for high-
way trucks and buses.
Regulatory authorities at the state level
also have their own sets of emissions regu-
lations. In states such as California, Colo-
rado and New York, many regulations go
further, and are more restrictive than fed-
eral rules.
Apart from regulations placed on
the industry, many companies are go-
ing above and beyond the requirements,
whenever possible. One such example is
Cabot’s ability to directly turn wells in-
line after the completions process, rather
than flaring. New EPA regulations will
make this the industry standard in 2015,
but Cabot is already adopting the process
in areas, where pipelines are available.
GREEN COLLABORATION
Cabot has worked closely with Baker
Hughes to develop and implement frac
services in the Marcellus region that aim
to reduce the operator’s environmental
footprint while sharing the economic in-
centives for green completions. On the bi-
fuel engine front, Baker Hughes, working
with its engine supplier, Cummins, has
Originally appeared in World Oil
®
MARCH 2014 issue, pgs 99-102. Posted with permission.

2. 100 MARCH 2014 / WorldOil.com
REDUCED EMISSION COMPLETIONS
converted its Rhino hydraulic fracturing
pumping units to run on natural gas-die-
sel fuel blends.
The Cummins diesel engines are ret-
rofitted with bi-fuel conversion kits. The
engine supplier has developed bi-fuel
engines, ranging from 800 to 3,500 hp,
for high-horsepower markets, such as
oil and gas well servicing applications.
While the first engines met Tier 2 EPA
emissions regulations, Cummins is now
developing bi-fuel engines that meet
Tier 4 Final standards.
The process of converting a diesel en-
gine to run on a natural gas-diesel mix
is minimally invasive and requires little
modification to the original engine. A
conversion kit consists of a program-
mable logic controller (PLC), ductwork
to transport natural gas to the engine,
and a series of regulators to reduce the
gas pressure prior to entering the engine’s
combustion chamber. The PLC signals a
throttle valve that controls the natural gas
volume entering the engine, as well as the
subsequent substitution rate of natural
gas for diesel.
While natural gas can make up the
majority of the fuel mixture, some diesel
is required to act as the ignition source.
However, once the diesel starts the en-
gine, the PLC slowly ramps up the natural
gas injection. The injection rate of natural
gas increases with the horsepower output
of the engine, up to a current maximum
substitution level of 70% natural gas to
30% diesel.
The bi-fuel system responds quickly
to changes in natural gas supply pressure,
engine knock and cylinder temperature,
by making systematic adjustments to
optimize the substitution rate and pro-
tect the engine. If the natural gas supply
is compromised, the PLC can react and
turn off natural gas flow in as little as 250
msec, while the engine continues run-
ning without interruption on 100% die-
sel, until the gas supply problem is cor-
rected. The well completion experiences
no negative consequences with respect
to engine performance, due to natural
gas delivery variations.
FIELD APPLICATION
Cabot planned a stimulation opera-
tion that called for the service company
to provide a fleet of 14 bi-fuel pumps, to
stimulate a 10-well Marcellus pad, with a
total of 170 frac stages. While the pumps
could operate on natural gas supplied
as CNG or LNG, the operator chose to
use its own field gas as the source, which
was abundant and readily available from
gathering lines in close proximity to the
frac site.
LNG and CNG provide smaller
carbon footprints compared to diesel,
and they satisfy the lower emissions re-
quirements for green completions in
the field. However, these sources still
require processing at remote facilities,
over-the-road transportation to the field,
and onsite storage, all of which adds cost
and increased environmental and safety
concerns.
Field gas was the lowest-cost, most-
sustainable option, as its close proxim-
ity to the wellsite generated a lower, total
carbon footprint, compared to any other
natural gas source. Furthermore, Cabot’s
exceptionally pure field gas is rich in
methane, which increased the engine ef-
ficiency, required minimal processing and
eased concerns about supply disruptions.
While it was not required in this ap-
plication, the service company deployed
a Joule-Thompson skid in other liquids-
rich fields to separate heavier compo-
nents, such as ethane, propane and bu-
tane. Rather than flare off these heavier
hydrocarbons, the separated compo-
nents can be recirculated into the op-
erator’s sales line, further lowering both
emissions and costs.
The field plan called for piping field
gas from some of the operator’s produc-
ing wells to a gas processing unit (GPU)
near the frac pumps. The GPU contained
a dryer to remove condensate, and a filter
to remove particulates from the field gas
Fig. 2. Overview of frac pump setup.
Fig. 1. Baker Hughes Rhino pumps are driven by Cummins bi-fuel engines.

3. 102 MARCH 2014 / WorldOil.com
REDUCED EMISSION COMPLETIONS
to avoid any reductions in engine perfor-
mance. The pressure was then reduced
from 600 psi to approximately 50 psi, af-
ter which the natural gas was piped to a
conduit and distributed to each bank of
bi-fuel pumps.
The bi-fuel technology performed as
planned, consuming 15,100 Mcf of field-
supplied natural gas, and delivering ben-
efits in terms of both efficiency and en-
vironmental performance. There was no
loss in hydraulic horsepower, compared
to a diesel-only engine, and all 10 wells
(170 stages) were fractured in 27 days.
Cabot twice achieved a company record
of nine stages fraced in a 24-hr period.
Substitution rates were uniformly
high and frequently reached the maxi-
mum blend of 70% natural gas. Cabot
calculated that the use of the Baker
Hughes bi-fuel fleet allowed the firm to
offset approximately 110,000 gal of die-
sel with its own natural gas, and saved
more than $475,000 in fuel costs.
Cabot also eliminated as many as 16
diesel re-supply runs, based on the op-
erator’s use of 7,200-gal tanker supply
trucks, its simplification of logistics, and
its reduction in the amount of traffic at
the wellsite and through neighboring
communities. The reduced diesel us-
age also lowered potential HSE risks re-
lated to refueling, including challenging
and potentially dangerous “hot fueling”
operations.
FRAC FLUID SCREENING
Baker Hughes screened all frac fluid
components, using its Chemical Evalu-
ation Process Review (CEPR) program,
an evaluation methodology designed to
ensure that sustainable oilfield chemicals
are developed and deployed, and adhere
to all relevant regulatory requirements.
Chemicals evaluated and deemed to
meet stringent environmental and toxi-
cological standards are categorized as
SmartCare qualified products.
As part of the CEPR program, a team
of specialized chemists and toxicologists
evaluate the individual components of a
product to determine their compliance
with several criteria:
• Highly discouraged substances. All
chemical components are screened
to ensure that they do not fall on
the United Nations’ list of persistent
organic pollutants or the EPA’s lists
of persistent bioaccumulative and
toxic chemicals.
• OSPAR HMCS pre-screen. Formu-
lated products and their constituent
components are prescreened to reg-
ulatory criteria within the OSPAR
Harmonized Mandatory Control
System (HMCS), which oversees
the use and discharge of oilfield
chemicals in the North Sea.
• Regulatory assessment. Each chemi-
calisassessed,basedoncriteriafrom
more than 20 different regulatory
lists from throughout the world,
which helps Baker Hughes identify
potential regional usage concerns
and determine if suitable substitute
chemistries are available.
• Chemical hazard evaluation. Prod-
ucts and components are scored,
based on a quantitative assessment
of environmental, toxicological
and physical hazards. This method
is patterned after the UN Globally
Harmonized System (GHS) of Clas-
sifying and Labeling chemicals.
GREENER COMPLETIONS
The combined contribution of the bi-
fuel system and qualified fracturing addi-
tives is helping Cabot achieve one of the
cleanest completions in North America.
The operator plans to repeat this success
with Baker Hughes in future Marcellus
frac operations in the year ahead, and will
continue to collaborate to drive greater
operating efficiencies and lower emis-
sions from these service offerings, to stay
ahead of newer, more stringent regulatory
guidelines.
JERAMIE MORSCHHAUSER is
a completions engineer for
Cabot Oil & Gas Corporation,
where he manages completions
projects, including toe
preparations, hydraulic
fracturing, and flowback for the
North Region Marcellus shale
operations. Previous to working for Cabot, he
worked as a drilling engineer, supervising
day-to-day drilling operations at Consol
Energy. Mr. Morschhauser graduated from the
University of Pittsburgh with a BS degree in
chemical engineering.
SEAN PARKER is the technical
manager for the North
American Region at Baker
Hughes. Mr. Parker has held
positions as both a field and
R&D engineer for hydraulic
fracturing and cementing,
helping to facilitate the
integration of natural gas technologies into
pressure pumping equipment. He began his
career with Baker Hughes in 2007 and holds a
BS degree in mechanical engineering from the
University of Texas at Arlington.
BRIDGET TODD is manager of
the Environmental Conformity
Group within Baker Hughes,
with a focus on chemical
disclosure, product review and
refinement, and greenhouse
gas emissions. Prior to joining
Baker Hughes in 2011, Ms. Todd
worked as environmental consultant,
collaborating with energy companies globally
on mitigation/remediation design, regulatory
compliance, and litigation support. She
received a BS degree in geology from Sam
Houston State University.
Fig. 3. Connection point between field gas supply and bi-fuel manifold.
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