HYDRAULIC FRACTURING ADVANCES
Metal-seal dissolvable frac plugs
use simplified design to improve
reliability during plug and perf
BY JINLU WANG, VERTECHS GROUP
Compared with composite frac plugs, dis-
solvable frac plugs currently only have less
than 20% of the market share of the plug-
and-perf completion method. Frequently
cited disadvantages include casing ero-
sion and issues with dissolving too fast
or too slow, leading to increased costs and
longer completion times. However, newer
and more simplified dissolvable frac plugs
could help to address these challenges and
have the potential to achieve efficiency
and cost savings in major unconventional
plays around the world.
One source of limitation with frac plugs
is the elastomer. The oil and gas industry
has used elastomers as a material for
frac plugs – both in traditional composite
frac plugs and dissolvable frac plugs – in
zonal isolation for years. However, recent
research and observations made through
the use of downhole cameras indicate that
elastomers can sometimes fail or extrude,
leading to leakage and casing erosion. The
chemical nature of elastomers tends to
cause them to extrude under high pressure
and temperature conditions.
Still, elastomers can provide reliable
isolation when properly designed with
anti-extrusion mechanisms. These can be
made of overlapping plates or rings that are
compressed and flattened into a disc-like
shape, blocking the elastomer from slipping
through the gap of slip segments. In com-
plex downhole conditions, however, these
anti-extrusion mechanisms can sometimes
fail or not deploy fully, leaving weak points
that allow for extrusion to occur.
To address the issues associated with
elastomers, metal-seal dissolvable frac
plugs have been developed. These plugs
use a metal-to-metal seal to provide reli-
able isolation under high pressure and
temperature conditions, eliminating the
need for anti-extrusion mechanisms. As
a result, the design of the plug is sim-
plified, requiring fewer components and
materials. This can also make clean-out
runs faster and more efficient. In addition,
metal seals can eliminate running risks in
high annular velocities.
In challenging situations, hybrid seals
can also be used; it combines both an elas-
tomer ring and a metal-seal mechanism.
The elastomer serves as the initial pres-
sure barrier during stimulation, while the
metal seal undergoes plastic deformation
and fully engages with the casing wall
as the pressure increases. This not only
provides reliable isolation of the casing,
but the metal seal also serves as a robust
anti-extrusion component
Compared with these newer and more
simplified plugs, traditional dissolvable
frac plugs are typically made of complex
components that can be prone to failure
risks. These components may be sensitive
to temperature, pressure and other factors,
which can make it difficult to predict and
control the rate at which the plug dissolves.
Another potential limitation of tradi-
tional dissolvable frac plugs is that they
are often heavily customized to dissolve
at specific rates, which can be difficult to
predict and control. This can make it chal-
lenging to use these plugs in a wide range
of wellbores and production scenarios, as
the specific conditions and requirements
of each well can vary significantly.
Using dissolvable technology can be
both beneficial, but it does comes with its
challenges. To customize plugs that are
suitable for different conditions, a thor-
ough understanding of both application
challenges and engineering are neces-
sary. The tool supplier must consider all
operational details, including the condi-
tions and requirements, to design, simu-
late, validate and optimize the plug in
order to achieve optimal performance and
results for end users. This requires a care-
ful balance between tool performance and
dissolvability. Striking a balance between
the trade-offs in different applications and
scenarios is crucial for success. DC
LEFT: Vertechs’ traditional dissolvable frac plug design (left) versus its new design (right).The metal-seal dissolvable frac plugs
use a metal-to-metal seal, eliminating the need for anti-extrusion mechanisms. RIGHT: A metal-seal dissolvable frac plug is
rigged up before being run in hole. The plug’s simplified design meant fewer components and materials were needed.
36 M A R C H/A P R I L 2023 • D R I L L I N G C O N T R AC T O R
GLOBAL WORKFORCE DEVELOPMENT
ExxonMobil’s Guyana project
provides blueprint for building
local workforce, infrastructure
in emerging E&P markets
Center for Local Business Development shows
Guyanese suppliers how to maximize growth
opportunities, improve safety management
BY STEPHEN WHITFIELD, ASSOCIATE EDITOR
In developing countries like Guyana, an oil
company won’t be successful in their E&P
projects if they see the oil and gas in
the ground as the only resource being
developed. They also must consider the
potential local workforce and its techni-
cal and business capacities as valuable
resources, and then identify ways to devel-
op them. For ExxonMobil, as it embarked
on its exploration and development of the
Stabroek Block in Guyana, it recognized
that those efforts must also encompass
programs to build a competitive and thriv-
ing local business community.
In 2017, as it began Phase 1 of the
Liza project, the company launched the
Center for Local Business Development in
Guyana’s capital city of Georgetown. The
aim was to provide training to Guyanese
businesses and employees, developing
their skills, knowledge and abilities so
they could work more effectively in the oil
and gas industry.
The effort has been so successful in the
past four to five years that Susan Scott,
Socioeconomic Manager at ExxonMobil,
said it can provide a model for other com-
panies looking to jump-start local content
development in other emerging markets.
“The center really is a one-stop shop for
local capacity building, mentoring, cre-
ating networking opportunities and pro-
viding a platform for information shar-
ing,” she said. “The insights that we’ve
gained from this experience can really be
a benefit for others in determining how
they can foster that local participation
in emerging economies, whether through
doing something like this or taking the
individual components and applying them
to their own initiatives.” Ms Scott spoke
about the center’s development at the 2022
SPE Annual Technical Conference and
Exhibition (ATCE) in Houston, Texas, late
last year.
When the center first launched, the
focus was on engaging with local sup-
pliers and enhancing the competencies
of their workforce, as well as providing
general business support. There were sig-
nificant gaps in their awareness, not only
of how the oil and gas sector functioned
but also around its standards, practices
and requirements, Ms Scott said.
The center began holding three types of
basic awareness seminars – HSSE (health,
safety, security and environment), intro
to offshore oil and gas, and procurement.
The intro to offshore class was formulated
to teach local suppliers about the fun-
damentals, like what are the differences
between the various tiers of contractors
in the oil and gas sector. For example,
local companies were often seeking to
gain specific contracts directly with the
operato r because they didn’t understand
how the sector’s specialized business eco-
system or procurement process operated.
The seminar also showed attendees how
to leverage opportunities created by local
content requirements, along with the ben-
efits their country could see from oil and
gas development.
“In the early days, we were in a country
that had little to no energy literacy, par-
ticularly within the local business com-
munity. We had to ensure that the local
business community was engaged and
really in a position to benefit from the
industry ,” Ms Scott said.
The procurement seminar focused on
the processes around electronic procure-
ment and bidding for work with operators.
Participants learned, for example, about
standard payment systems in the industry,
which are typically based on milestones
and completed work instead of the upfront
payments that were more common with
Guyanese government contracts.
From 2017 to 2021, more than 6,000 peo-
ple attended the center’s seminars, and new
courses have also been added on financial
management, supply chain management
and human resources management. “ We
saw that the local companies we were
working with were growing at a fast pace.
As a center, we knew that we had to evolve,”
said Natasha Gaskin-Peters, Director of the
Center for Local Business Development.
“While these businesses had a base knowl-
edge of the fundamentals, they did not
know how to build management systems,
so we had to take them through the process
of building those systems.”
From 2017, when the Center for Local Business Development began operations in
Guyana , to 2021, the country saw a surge in the number of local suppliers.
D R I L L I N G C O N T R AC T O R • M A R C H/A P R I L 2023
37