American Oil and Gas Reporter - January 2015 - 173

Production Technology

ESP Configuration Lifts Problem Wells
By Adam Buehler
and Nathan Holland
HOUSTON-Developing unconventional oil and gas plays has proven a
boon to the North American exploration
and production industry over the past
decade, bringing production back to levels
not seen for nearly 30 years. However,
this increased production has not come
without some serious challenges that, if
ignored, threaten to shorten the lives of
unconventional wells and leave the majority of reserves in the reservoir.
Shale oil wells, for example, typically
contain a high level of associated gas,
which is produced (along with fracture
fluids and proppants) with the oil. Wells
in these plays also are prone to buildups
of scale, paraffin and other deposits, and
typically also yield emulsified fluids.
For wells on some form of artificial
lift, these conditions combine to cause
problems that include gas locking, abrasive
wear and pump plugging. For operators,
these challenges reduce pumping efficiency, increase power consumption, and
may require frequent well interventions
and workovers to repair or replace equipment. Interventions require taking the
well off line to correct problems, resulting
in costly downtime and deferred production.
Rod pumping is the most common
method of artificial lift, bringing oil and
water to the surface using the reciprocating
motion of a downhole pump assembly. A
continuous rod string connected to a large
surface pumpjack raises and lowers a
plunger within the pump assembly, which
lifts fluid in surges. While rod-lift systems
have been used effectively in conventional
oil fields that produce from vertical wells,
they are less efficient when used to pump
fluids from unconventional oil plays. In
wells producing heavier oil, the rods'
lifting efficiency is severely limited.
Kansas Field
This was the challenge facing an operator of a Kansas oil field. The operator
had a production goal of 200-300 barrels
a day from his oil wells, but the characteristics of the oil in the reservoir made
maintaining this rate with rod lift nearly
impossible. The operator tried many forms

of artificial lift, including jet pumps and
gas lift, but these systems were unreliable
because of the excessive gas entrained in
the produced fluid.
The operator then reached out to the
service industry to determine whether an
electric submersible pumping system
could produce these wells at the desired
production rates. While ESPs have provided a relatively efficient form of artificial
lift across a broad range of flow rates
and well depths, the presence of gas and
solids in the form of sand, scale and iron
sulfide deposits posed a challenge in
terms of operating efficiencies of pumps
in these wells.
The operator and service provider
worked together to identify the optimal
system configuration that would maximize drawdown and reliably increase
production, while also preventing gas
and solids ingress into the pump. They
settled on a solution consisting of one
or two uniquely designed, multistage
centrifugal pumps that could produce
reliably across a flow range of 50 to
2,900 barrels of fluid a day. A pump set
to a higher production rate typically is
installed first, and once rates naturally
decline, it can be switched for a lowerflow pump.
This strategy minimizes downtime and
workover costs, since all other components
of the ESP system stay in place and can
be used with the lower-flow pump. This
represents a departure from typical artificial

lift replacements, in which a higher-flow
lift method is completely switched to a
rod-lift pump once production rates declines.
To withstand the harsh downhole conditions that these high-solids wells present,
a mesh-type sand screen is installed. This
granular and flow-specific screen hangs
from a packer to filter the sand before
the produced fluids reach the ESP. This
helps prevent plugging and erosion, while
increasing the pump's run life and resistance to abrasive wear.
Additional protection is provided by
incorporating tungsten carbide bearings
and sleeves throughout the pump to ensure
stability and wear resistance. In addition,
abrasion-resistant coatings could be applied
to the individual pump stages. Wider
stage vane openings in the pump further
enhance system reliability by reducing
the potential for pump plugging while
improving solids handling.
Cooling The ESP
The ability to keep the ESPs cool
during operations also is a priority in
these wells. Unlike high-water-cut wells,
where the presence of water has a natural
cooling effect on pumps, the high oil cut
and gravity of the oil present greater
cooling challenges.
The solution came in the form of a
patented ESP recirculation system set
below the well perforations. These systems
have been used successfully since the

Incorporating innovative hydraulic design concepts that expand their operational range, the
latest generation of electric submersible pumps is designed to
maximize production and ultimate reserves recovery from
wells in conventional oil ﬁelds,
low-ﬂow rate mature oil ﬁelds,
and unconventional resource
plays with rapid production declines. High-performance ESPs
provide the operational ﬂexibility
required in dynamic well conditions to minimize system
change-outs and nonproductive
time, while reducing operating
expenses.

JANUARY 2015 173

American Oil and Gas Reporter - January 2015

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