American Oil and Gas Reporter - June 2018 - 86

SpecialReport: Artificial Lift Technology

Advances Optimize Lift In Horizontals
By Lou Martensen
OKLAHOMA CITY-Horizontal
drilling, completion and production techniques have evolved over the past decade
as operators have optimized the development of onshore resource plays, leading
the way to significant improvements in
the way artificial lift systems are used in
unconventional applications.
Characterized by steep decline curves,
turbulent fluid production and irregular
wellbore geometries, horizontal well conditions presented formidable challenges
for conventional artificial lift technologies.
Before the upstream sector was able to
establish predictable, profitable recovery
in horizontal wells, the industry first had
to adapt to a new way of operating and
develop production technologies that
would be fit for purpose.
Since 2011, hydraulically fractured
horizontal wells in the United States have
dominated the landscape, with good reason.
Among the various advantages to lateral
drilling, by far the primary driver behind
the unconventional boom is the ability
for operators to access a much greater
area of the producing formation than
what's possible with a vertical well. Rather
than hitting the pay zone once at a perpendicular angle, a horizontal wellbore
can maintain contact with the producing
formation for the extent of its lateral
section, which in some cases can reach
up to several miles. Additionally, because
a single horizontal well has the potential
to hit several stacked pay zones, operators
are able to produce more economically
while minimizing surface impact.
Proportional to the impressive gains,
however, are the significant obstacles
encountered in unconventional applications. For instance, a typical U.S. horizontal well experiences a 60-80 percent
decline in production in the first year,
producing about half of its estimated
lifetime oil production by the third year
of operation. With experience under its
belt, the industry now has a much better
understanding of decline curves in hydraulically fractured low-permeability
formations, which allows operators to
more accurately predict and manage production in unconventional wells. This
trend impacts the operator's reservoir
economics by influencing how capital
and operating costs are invested, as well
86 THE AMERICAN OIL & GAS REPORTER

as informing the amount of time required
to recover that investment.
At the same time, the steep transition
from high to low volume production has
direct implications in selecting and designing effective artificial lift systems. Because unconventional wells require some
form of artificial lift earlier in their life
cycles to maximize recovery from the production zone, these technologies play an
important role in unconventional wells. In
horizontal wells, artificial lift systems help
increase production and recover more reserves over time by reducing wellbore
pressure, encouraging nearby oil to drain
through natural and induced fractures into
neighboring areas of the reservoir.
Flexibility Is Key
However, selecting a type of artificial
lift for horizontal wells is complicated
by factors such as wellbore casing size,
severity of the curvature of the well and
the production flow rate. In horizontal
well conditions where production declines
considerably after a certain period, operators must select artificial lift systems
capable of handling the wide fluctuations
in production volumes.
FIGURE 1
ESP Modiﬁcations for
Unconventional Applications

Abrasion-Resistant Pump
Designs & Solids Handling

Gas Management Solutions

Anti Gas-Locking
VSD Motor Controls

Producers have experimented with various artificial lift methods in horizontal
tight oil plays-electric submersible pumps,
beam pumps, jet pumps, progressive cavity
pumps, plunger lift, gas lift, multiphase
pumps, etc.-but the high initial rates, steep
decline curves, proppant flowback, well
architectures and other factors make it extremely challenging for any single lift
method to efficiently transition through a
well's full productive lifecycle. To achieve
the required flexibility, implementing different artificial lift types at different points
throughout the life of the well has become
the most widely accepted strategy.
While changing out lift systems incurs
additional costs, this tactic allows operators
to optimize a well's performance as its
production profile changes over time.
High-volume systems such as ESPs can
be used to maximize early peak production,
switching to a rod lift system to continue
production at lower flow rates, and maybe
eventually installing gas lift or plunger
lift as gas-to-liquids ratios increase.
Perhaps one of the most critical turning
points for the industry has been the development of artificial lift technologies
specific to unconventional applications.
When horizontal drilling began to gain
popularity, artificial lift suppliers had not
yet invented the specialized equipment
that is available today. Without an alternative solution, operators simply installed
the same artificial lift systems designed
for vertical wells in their horizontal wells.
However, the conventional systems were
not equipped to operate in the abrasive,
unstable conditions of unconventional
production, causing operators to experience
frequent failures and excessive wear on
the equipment.
To make production sustainable, the
systems evolved to meet the specific requirements of the applications. By nature
of innovation, the deficiencies of the existing technology became areas for improvement, ultimately leading to a new
portfolio of solutions tailored specifically
for unconventional wells. Today, these
purpose-engineered solutions include reinforcing the equipment with more durable
and protective materials, designing pumps
to prevent accumulation of solids, implementing gas management devices, and
modifying pump configurations to allow
greater flexibility and permit installation
beyond the well's vertical section.
American Oil and Gas Reporter - June 2018

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