Technical

Technical Leaders
How to Tackle the Challenge
of Mature Field Development
Thais McComb, Chevron; Brian F. Towler, University of Wyoming
Question: What is a mature oil field in
your opinion?
TM: An oil field can be classified
as mature when its production
rate is significantly declining and/
or when it is close to reaching its
economic limit. A field might also be
considered mature when it is close to
attaining a recovery factor considered
acceptable for its reservoir mechanisms.
Typically, a mature field will have
very old wells and aged equipment and
infrastructure which have a higher risk
of safety and environmental issues.
BT: One that has been in
production for many years and has
depleted its primary and secondary
reserves. Consequently, its
facilities and technology are usually also
very old.
Question: What are the methods and
technologies used to produce mature
oil fields?
TM: There are several methodologies
and technologies available to revitalize
mature fields. However, before
selecting which one will be used, it
is necessary to assess what is the “target
prize” of your revitalization project.
The first step is to get a solid
characterization of the reservoir to
reduce the technical uncertainty of
the resources associated with your
project. Today there are many new
tools including logs, modeling and
visualization software, and seismic to
help you to identify bypassed oil in
your reservoir.
Once you have determined the
“target prize,” you could decide between
using an improved oil recovery (IOR)
technology (e.g., waterflood, gasflood,
horizontal or infill drilling, conformance
control, stimulation), an enhanced
oil recovery (EOR) technology (e.g.,
continuous steamflood, hydrocarbons/
N2/CO2 injection, polymers/surfactants/
alkali/low-salinity injection), or a
combination of IOR/EOR processes.
Thais McComb currently works as a CO2 enhanced oil
recovery (EOR) advisor for Chevron in Houston. With 30
years of broad experience in reservoir engineering, she has
worked for 15 years in research and development related to
CO2 injection (fluids phase behavior, rock characterization,
slim-tube and core experiments, asphaltene precipitation
and dispersion), water injection (conformance control and
formation damage), chemical EOR, and heavy oil with Elf
Aquitaine (France) and PDVSA (Venezuela). McComb has also held numerous
reservoir-management team lead positions in Venezuela (PDVSA and Shell) and the
US (Chevron) that involved high-temperature/high-pressure hydrocarbons, N2 and
CO2 injection, chemical EOR, high H 2 S production, and heavy oil. She holds a BS in
petroleum engineering from the University of Zulia, Venezuela, and an MS and a
PhD in chemical engineering from the Institute Nationale Polytechnique de
Toulouse (INPT) in France.
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You can even just choose to revamp
your wells and facilities keeping the same
production scheme.
By using some of these integrated
reservoir-management techniques, a
young professional will be able to design
a field-rejuvenation plan that maximizes
production and reserves.
BT: Various techniques that can be
used include waterflooding, miscible
and chemical (e.g., polymer, surfactants,
alkali, and ASP) flooding, and
steamflooding (for heavy viscous oils).
Question: How have these methods
changed over time?
TM: Technology and computing
power have evolved significantly,
which streamlines the process and
timeframe to develop a more accurate
characterization of the reservoir. The
new technologies and techniques include
3D and 4D seismic for data processing
and interpretation, 3D visualization, new
coring and well testing, and advanced
software for modeling and simulation.
These tools allow you to build models
with thousands of wells and finer
gridding with faster run times.
In addition, we need to recognize
recent technology developments that
include advanced drilling and completion
techniques (including directional and
horizontal extended wells); smart wells;
remote, real-time wireless surveillance
and control systems; reduced footprint
rigs; third-generation modular facilities;
novel materials and composites which
resist high temperatures, abrasion
and presence of acid gases; hightemperature-/high-salinity-resistant
chemical additives for IOR/EOR
processes; and new techniques for
selective stimulation.
BT: In the past only waterflooding was
used. Now a variety of EOR technologies
are applied. CO2 miscible flooding has
become very popular as well. Previously,
some hydrocarbon miscible flooding
was implemented where applicable. But
the hydrocarbon molecule being used
became too valuable to inject into the
ground. CO2 does not have as much use
or value, so it became more economical
to use CO2 instead of the more valuable
intermediate hydrocarbons (ethane,
propane, butane, and pentane).
For shallow heavy-oil reservoirs,
steamflooding has become popular.
In certain limited locations, chemical
flooding has been gaining ground.
Question: What factors play important
roles in determining the appropriate
techniques for specific fields?
TM: If a field has considerable remaining
saturation, in part, the reservoir and
fluid properties will control which IOR
or EOR process(es) are most suitable.
There are many industry tools that can
be used for preliminary screening of
these processes. However, the integrity
of the infrastructure and wells, the
field location, and the availability of
the injectants or additives significantly
influence the economic feasibility of any
of these processes.
An example is a mature offshore
field, with properties that make it an EOR
candidate, and that still has high movable
oil saturation. In practice, the feasibility of
applying an EOR process in this case is
low due to the status and capacity of the
infrastructure and the capital investment
required to upgrade the facilities to
accommodate an EOR infrastructure.
Operational expenses associated with
the transportation or manufacture of
injectants or additives might also be
cost-prohibitive. This could also be the
case with remote onshore fields, where
the cost of transportation of additives/
injectants, equipment, supplies, and
spare parts would outweigh the benefit of
extending their productive life.
BT: Initially some simple screening
techniques are applied but, in my
opinion, these have limited applicability.
Nearby analogies can be useful because,
if a similar nearby field has been
successfully flooded, it increases the
chance of success in your mature field.
Reservoir simulation can give a good
indication of the recoveries and rates
to be expected from an enhanced oil
recovery project. Core floods and other
lab tests are important tests to be done
which can give an indication of the results
to be expected from a particular flooding
technique. Such lab tests also provide
important data for input to reservoir
simulation models.
Question: What type of mature fields do
you foresee as attractive candidates for
trying enhanced oil recovery methods?
TM: An ideal EOR candidate field should
have remaining oil saturations greater
than 35%, reservoir properties that are
conducive to EOR, access to an injectant
source (e.g., water, CO2), accessible
location, and acceptable infrastructure
and well integrity.
BT: In general, fields with high
permeabilities and high oil saturations,
and fields that have already undergone
successful IOR methods, such as
waterfloods, make the best candidates.
Reservoir continuity is also important and
desirable. Large reserves of remaining
oil in place and thick formations can also
be important. But less ideal reservoirs
should not be ruled out. If money can
be made, EOR techniques should
be applied.
Question: How does a mature oil
field’s cost of production compare to a
regular field?
TM: In most cases, production
costs of mature oil fields are low
when compared to regular fields.
Undoubtedly, the cost of extending
the field’s productive life will require
extensive capital investment. To do a fair
comparison, one needs to analyze and
prioritize each project under the current
oil industry economic scenario, whereby
sustained high oil prices have been
driving production cost increases due to
the scarcity of rigs and skilled manpower.
It is worth mentioning that the majority
of new conventional oil production is
coming from deepwater basins where
production costs are very high. Secondly,
the current discovery rate of new
fields is low and the costs associated
with the development of this new oil is in
some cases four to five times the cost
of producing oil from onshore, shallow
offshore, and mature fields.
BT: Generally the cost of production is
higher because water/oil ratios and gas/
Brian F. Towler is the CEAS (College of Engineering &
Applied Science) fellow for hydrocarbon energy resources
and professor of chemical and petroleum engineering at the
University of Wyoming. He began his career as a senior
reservoir engineer at Arco in Plano, Texas. He returned to
Australia to work as the principal reservoir engineer for
Oilmin and Moonie Oil. Towler served as chairman of the
SPE Queensland Section. Subsequently, he joined the
University of Wyoming as an assistant professor in petroleum engineering, where
he has conducted research in reservoir simulation, wax mitigation, wellbore
stability, coal gasification, and bentonite plugging. In 2004, he was promoted to
professor and appointed head of the Department of Chemical and Petroleum
Engineering. In 2008, he was appointed CEAS fellow. Towler received his PhD in
chemical engineering from the University of Queensland (Australia). He has two
published books: Fundamental Principles of Reservoir Engineering (SPE) and Coal
Gasification and Its Applications (Elsevier). He has been a registered professional
engineer in the state of Wyoming since 1998.
Vol. 9 // No. 3 // 2013
19
Technical Leaders
oil ratios can be high and production
rates are low.
Question: Where are mature oil fields
mostly concentrated in the world?
TM: I have not done an extensive search
on the number of mature oil fields
recently, but I will guess that China,
the US, Middle East, and former Soviet
Union contain the largest number of
fields—followed by some members of the
Organization of the Petroleum Exporting
Countries (OPEC), such as Venezuela.
BT: Mature oil fields are located all over
the world because the oil industry is a
mature industry. But the places where
they are most concentrated are: the USA,
Russia, Middle East, and China.
Question: Are there additional
environmental regulations to be followed
for mature oil fields?
TM: Generally, mature fields have an
infrastructure that is aging and was
likely built before many of the current
environmental regulations were adopted.
It is likely that the highest exposure are
oil spills from aged wells and facilities,
as well as gas venting due to the need for
shutdowns for maintenance and repair.
BT: Not really. Different conditions may
mean different regulations are relevant.
In the USA, for example, the Clean
Air Act and Clean Water Act still must
be followed.
Question: Mature reservoirs are
accompanied by old wells. So what are
the different well-integrity practices
used in these mature oil fields?
generally have to be plugged and
abandoned and/or re-drilled.
Question: Do you think young
professionals should consider working
on a mature reservoir where many
processes and methods have already
been tested or on a new field where he/
she can implement novel technologies?
TM: Well-integrity practices might
include scheduled Christmas tree or
wellhead maintenance, cement-bond
logs, pressure tests, temperature and
ultrasound logs, or downhole sensors
to detect casing, tubing, and valve
leaks. Repairs or intervention activities
must have very specific and rigorous
plans for addressing barriers to prevent
uncontrollable flow from the wellbore
to the external environment: At least
two independent barriers need to be
in place during all well activities and
operations, including suspended or
abandoned wells.
TM: I believe mature fields give you
the opportunity of reviewing the field
history and learning from past events.
This allows you time to expand your
knowledge and become more proficient
in reservoir and production engineering.
Additionally, in the current economic
scenario where oil prices seem to stay
above USD 80/bbl, it is reasonable to
expect that oil companies will continue
to develop projects to revitalize
or extend the production of their
mature fields. This focus gives young
professionals the opportunity to use
their creativity and enthusiasm to apply
novel technologies.
BT: Wells have to isolate formations so
that oil and salt water cannot contaminate
drinking water supplies. It is also
necessary to keep hydrocarbons from
migrating into other formations and
becoming lost. Wells that lose integrity
BT: It doesn’t really matter. Each
situation creates its own challenges
and experience. The oil industry is an
exciting business. It is always interesting.
So take your opportunities when
they arise. TWA
had been a struggling program. It is now
alive and well with regular technical and
social activities. Now serving as our section
membership chair, Maria has identified
a number of innovative ways our section
can recruit and retain members. We are
starting to implement her ideas.”
Letters of recommendation are
an important part of most award
nominations. When considering whom
to ask for a letter of recommendation,
consider their knowledge of the
candidate and their stature within SPE.
It may be desirable to show the breadth
of an individual’s contribution by having
letters submitted by colleagues working
for a different company than your
nominee. Be sure to check www.spe.
org/awards to verify the requirements
regarding recommendation letters for the
specific award you are considering.
Preparing a great nomination isn’t
as hard as it may seem. Giving your
candidate the best chance to succeed
does take effort, so bear in mind that
nominations are typically due by 15
February and that they may take several
weeks to prepare. If you’re overwhelmed
by the process or have questions, SPE
staff are always available to help (contact
awards@spe.org for international
awards or sections@spe.org for regional
awards). All nomination materials will be
kept confidential. TWA
SPE 101
Continued from page 14
committee understand what sets
your candidate apart by using clear,
concise statements to illustrate why a
nominee is deserving of an award. Be
specific. It’s unfortunate, but sometimes
nominations are poorly written. Consider
this fictitious example: “Maria served
on our scholarship committee and as YP
liaison. She is now our membership chair.”
Nothing here makes Maria stand out.
Instead, the nominator could write “While
serving on the scholarship committee,
Maria helped us to engage a larger
student audience than we had previously
been able to reach. Our applicant pool
is now twice as big as it used to be. As a
YP liaison, Maria brought energy to what
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