American Oil and Gas Reporter - December 2018 - 67

SpecialReport: Well Stimulation & Completion Technology

Chemistry Bolsters Completion Fluids
By Colter Cookson
Engineers who design completion
fluids must balance two competing goals:
the desire to keep chemical costs as low
as possible and the need to ensure fluids
have the desired characteristics. Using
laboratory tests, previous results and
sound theories, they work to identify the
chemical mix that will provide the desired
performance at the lowest total cost.
As the industry learns more about
how chemicals behave down hole, and
as chemical manufacturers invent improved
solutions to meet changing requirements,
the number of tools at engineers' disposal
continues to grow. The latest additions
include more efficient high-viscosity friction reducers and surfactants, as well as
a versatile sodium silicate monomer and
solid chemical carriers that gradually release scale, corrosion and paraffin inhibitors down hole.
Qi Qu, vice president of research and
innovation for oil and gas for Solvay
Novecare, says today's completion fluids
must be more robust than ever. "As operators move toward longer laterals, the
fluids have to endure greater physical and
mechanical stress," he notes. "They also
need to carry proppant longer distances."
Because there is a direct correlation
between initial hydrocarbon production
and proppant intensity, the amount of
proppant that completion fluids must
transport through formations continues
to rise, Qu adds. "To carry the proppant,
operators could increase the amount of
fluid they pump, but that is expensive
and inefficient. Instead, they generally
viscosify the fluid so it can keep more
proppant in suspension for longer. This
has allowed them to gradually increase
proppant loading from one-half to one
pound per gallon to two, three or sometimes even four pounds per gallon."
Rather than using cross-linked gels or
guar to achieve the necessary viscosity,
operators frequently rely on synthetic
polymers that act as both friction reducers
and gelling agents. Qu says these highviscosity friction reducer (HVFR) polymers must be efficient, versatile and easy
to break.
"HVFRs face many challenges," he
comments. "One of the biggest is effectively generating viscosity in produced
water, which often is recycled for use in

completion fluids. Even after treatment,
most produced water has high total dissolved solid levels. Maintaining viscosity
is difficult once TDS levels reach 10,00015,000 parts per million."
Qu says Solvay is conducting research
to develop more efficient and reliable
HVFRs and other chemical solutions.
"Our research center in The Woodlands,
Tx., has the ability to synthesize new
chemicals and test their characteristics,
including their ability to reduce friction
and improve proppant transport. This
helps us create and evaluate new formulations quickly," he says.
"Our goal is to deliver the most efficient proppant transport solution to the
industry," Qu describes. "In addition,
we want to make sure the product works
well in both high and low-TDS water.
Fracturing water quality can vary dramatically within the same well and from
well to well, so flexibility is needed to
keep fluid design and logistics as simple
as possible.
"Proppant transport solutions also need
to break down quickly and leave almost
nothing behind," Qu continues. "This is
becoming more important as the industry
moves to smaller and smaller sand, replacing traditional 20/40 mesh with 40/70
and 100 mesh. These smaller sands create
flow paths that are harder to clean and
more likely to plug."
As it refines its high-viscosity friction

reducers, Qu says Solvay is looking for
additional ways to optimize proppant
placement. "We are developing a new
family of chemistries that is changing
the conventional view of how effectively
a given viscosity fluid can carry proppant
under downhole conditions," he relates.
"This will allow operators to increase
the propped surface area without increasing
proppant intensity, giving them another
way to raise production."
Flowback Surfactants
Qu reports Solvay has developed a
suite of flowback surfactants, including
an environmentally-friendly formulation
that is compatible with any type of frac
fluid.
"These surfactants are a step forward
from traditional alternatives, which are
designed primarily to help fracturing fluid
return to the wellbore," he says. "While
the new surfactants retain that capability,
core flood testing shows they also significantly increase hydrocarbon production
rates across different pressures. This
occurs because we have optimized surfactant properties that are critical to production, including surface tension, interfacial tension and contact angle."
The company also is investigating new
techniques to release chemicals gradually
down hole to extend the effective lives of
scale, corrosion and paraffin inhibitors,
Qu reports. "For example, we are devel-

To ensure that completion ﬂuids can handle rising proppant intensities, Solvay reports
it is developing more efficient high-viscosity friction reducers. These new products work
well in produced water and break easily, the company says.

DECEMBER 2018 67

American Oil and Gas Reporter - December 2018

Table of Contents for the Digital Edition of American Oil and Gas Reporter - December 2018