38
LNG
INDUSTRY
SEPTEMBER
2014
Next, Antero conducted a bid process to choose its
LNG and related services supplier. It ultimately selected
Prometheus Energy, a specialist in providing LNG fuelling
solutions to the oil and gas industry. The following
objectives have been completed and sustained:
To operate safely and reliably at all times.
To reduce costs.
To significantly reduce overall emissions from
operations.
To reduce truck traffic on challenging rural roads and
pad sites.
It is important to note that as the domestic merchant
LNG industry continues to build out, transport distances
will decrease over time, and LNG delivered costs to
customers should become even more competitive.
The value of this network supply configuration cannot
be overestimated. Figure 3 presents a visual summary of
LNG deliveries made to one of Prometheus’ drilling
customers in the Rockies, which operates multiple 100%
dedicated gas rigs. Note how many different sources of
LNG may be required to supply one rig. As a result, for its
supply regions, the company will typically have three to
four sources available to customers in order to provide
LNG supply assurance.
As important as LNG supply reliability is to the
customer, the reliability of the equipment to both safely
store and vaporise the LNG to meet the fuel demand of
the rig is equally essential. Prometheus deployed its LNG
storage and vaporisation units (equipped with all the
modules of a safe and reliable LNG fuel platform) to
support Antero’s onsite drilling operations, including a
mobile LNG storage trailer, an integrated electric
vaporiser, a supplemental ambient vaporiser, and an
integrated flow control and emergency shutdown (ESD)
system.
To date, Antero has had Prometheus deploy as many
as seven LNG supply systems to support its transition to
100% dedicated gas drilling operations. For each LNG
supply solution, Prometheus tracks and regularly reports
its total system safety and reliability performance.
Prometheus also maintains on-stream factors in excess of
99.5%.
Conclusion
Many operators have chosen to test natural gas based
drilling by application of dual fuel conversion technology
to existing diesel engines. The results have been mixed.
By its nature, natural gas does not readily burn in a diesel
engine. With a narrow flammability range and a much
higher autoignition temperature than diesel, the injection
of natural gas to a diesel engine has to be done with
precision and care. In addition, the dual fuel system has
to be carefully maintained in order to ensure that mixing
and high diesel substitution rates can be maintained
throughout the entire well drilling time period.
Many third party suppliers rushed to supply these
engine conversion kits several years ago as natural gas
prices fell in comparison to distillate/diesel fuels. The
engine OEM suppliers are now responding to this market
with improvements to their own technology, and at prices
that are deemed more competitive by operators and
drilling contractors alike.
In short, maintaining diesel substitution rates at or
above 50% over the entire drilling cycle has proved to be
a challenge. Initially suppliers claimed 70+% diesel
substitution rates. While this performance can be achieved
under very carefully controlled conditions and across a
very narrow load range on the engine, that level is not
sustainable across the entire drilling load cycle.
Furthermore, diesel substitution is dependent on gas
quality. When using field gas, the presence of NGL
hydrocarbons can de-rate the substitution performance
significantly. Operators have experienced substantial
performance drop-off when moving these systems to
different pad sites with different field gas quality. While
LNG solves this problem by providing consistent quality
from well to well, it is more expensive than field gas.
If diesel substitution rates can be maintained at or near
50%, which is finally being consistently achieved, LNG
supply is not only a simple, easy solution, but it becomes
economic with paybacks on the added investment for dual
fuel conversion kits typically less than 12 - 18 months.
In addition, field gas can be economic in the dual fuel
application and even at lower diesel substitution rates,
provided that the field gas conditioning equipment can be
readily moved to new locations and that the equipment is
well maintained. It is also important to note that when the
field gas quality changes, the dual fuel kits must be
recalibrated to provide the unique diesel substitution
profile required by the specific field gas quality. One big
advantage of LNG is that the quality is consistent from
well-to-well. This significantly simplifies the process for
dual fuel usage and does not require frequent recalibration
of the dual fuel kit.
Prometheus, along with many operators, understands
the significant economic advantage of 100% gas drilling
over dual fuel operation. The LNG equipment (and cost)
required is similar, yet the fuel savings are doubled in
dedicated gas drilling, thus providing paybacks of less
than one year, even when using LNG in most cases. Antero
Resources has demonstrated an innovative approach to
maximising 100% gas drilling, and it has paid off in more
than just a monetary fashion as it continues to accelerate
asset development in the Appalachian basin.
Figure 3.
Sources of LNG supply.
