Got an aging oil or gas field that's
on its proverbial last leg?
Not to worry - the tonic du jour is
integrated reservoir characterization.
It's a proven relatively low cost, low risk
approach to building reserves, and it's used on a regular
basis to breathe new life into mature, often marginal fields.
"Field re-exploration strategies like resource-targeted
infill drilling and field or play extension wells, along
with strategic recompletions and waterflood optimization
strategies based on sophisticated reservoir characterization
programs are the preferred approach to revitalize old fields,"
said Roger Tyler, a partner in Advanced Reservoir Characterization
and Exploration Services (ARC).
"These applications have captured almost two-thirds
of the 40 billion barrels of oil that have been added to
the U.S. reserve base over the past 20 years."
Tyler noted an added benefit of applying
reservoir characterization technologies to mature fields:
New wells typically are more cost effective.
In Texas, for example, the volume of reserves
added per new well drilled has increased by 40 percent in
the first half of this decade as a direct result of these
Tyler co-authored a paper with colleagues
from ARC and the Texas Bureau of Economic Geology (BEG)
addressing integrated reservoir characterization of mature
fields and the application of 3-D visualization techniques
to reserve growth strategies. The paper was presented at
October's Gulf Coast Association of Geological Societies
annual meeting in Houston.
It's estimated that more than 100 billion
barrels of movable oil will remain in place in heterogeneous
reservoirs in the United States after recovery of existing
reserves, he said. This sizeable resource is in reservoir
compartments that are untapped or either vertically or laterally
bypassed by injected fluids, making them ideal targets for
integrated reservoir characterization programs.
Tyler predicted that reservoirs where the
greatest reserve growth will be realized are those with
the most accurate reservoir descriptions - where there is
a high degree of internal heterogeneity and substantial
volumes of untapped or bypassed hydrocarbons.
This reserve growth, according to the geoscientists,
can best be achieved by taking the reservoir characterization
process a giant step forward, enhancing it via the rapidly
evolving virtual reality technology.
"Immersive virtual reality promises to revolutionize
the way we traditionally do reservoir characterization,"
"Reservoir characterization programs rely
on thorough integration of geological, seismic, petrophysical
and production engineering data into a quantified description
of reservoir architecture and rock property structure by
individual professionals possessing specialized knowledge,
but in distinctly different disciplines," he explained.
"It's this, the very nature of how we do
reservoir characterization, that can benefit from immersive
virtual visualization technologies."
By synthesizing shared representational objects
of the evolving reservoir model, virtual reality removes
the barriers indigenous to mentally imaging multiple complex
data sets, Tyler added.
The interactive manipulation of the integrated
models and application of cutting-edge visualization techniques,
such as temporal mapping of reservoir dynamics, significantly
enhances the process of reservoir characterization, he said
- and identifying reserve growth opportunities.
Tyler and his colleagues have successfully
applied virtual reality analysis to stratigraphically and
structurally complex fields in Lake Maracaibo, Venezuela,
and along the Texas Gulf Coast. The effort took place at
the BEG's Virtual Imaging Visualization Environment (VIVE).
In the Venezuelan field, the main Eocene
producing reservoir is divided by a fault system, with numerous
minor faults influencing fluid flow in the reservoir.
Production performance differs markedly on
either side of the main fault. Production on the west side
is driven by an active aquifer, which provides pressure
support, and gas cap expansion provides the drive mechanism
to the east. Gas injection was first implemented in 1962
to supply producing energy to the reservoir on the east
"Our analysis was placed in the virtual environment
and focused on time-sequence motion mapping of the aquifer
encroachment, gas cap expansion and production response
to the injected gas," Tyler said. "The fluid dynamics were
illustrated in outputs from the virtual imaging and provided
a profound understanding of the compartmentalization in
"More important, the virtual imaging facilitated
the identification of bypassed compartments of the reservoir
that formed the basis for strategic infill drilling and
recompletion recommendations to target the estimated 100
million barrels of remaining mobile oil."
Recent advanced reservoir characterization
efforts by Tyler and his colleagues along the Texas Gulf
Coast included research and development programs focused
on multiyear oil and gas field analysis in Texas, with an
emphasis on Texas State Lands.
To identify the residency of the remaining
oil and gas resource base, the group's approach has been
to define and deploy on a field-to-field basis advanced
recovery strategies to ensure maximal recovery efficiency.
Tyler cited, for example, the Umbrella Point
Field in Galveston Bay, Chambers County, which is producing
oil and gas from Gulf Coast Frio barrier island strandplain
Through mid-1997, the field's mature Middle
Frio reservoirs had produced a total 17 million barrels
of oil and 103 billion cubic feet of gas from 36 wells developed
in 15 zones between 8,000 and 10,000 feet. Estimates indicated
the daily production rate in the field was 189 barrels of
oil and 2.8 million cubic feet (MMcf) of gas from 11 completions
in 10 wells.
As part of the State of Texas' Advanced Resource
Recovery Program, 3-D seismic data and virtual reality imaging
were used to help define bypassed gas compartments there,
and a new gas well was recommended and subsequently drilled
into the lower Frio in January 1998.
According to Tyler, the well tested 11.5
MMcf per day and 220 barrels of liquid daily. Cumulative
gas production for the well was more than 812 MMcf as of
May 1998, increasing total field production more then 2,600
percent since January 1998.
Such results, however, are only the tip of
the iceberg when you look at the numbers applicable to Texas
The research team concluded 1.6 billion barrels
of mobile oil will remain on these lands at reservoir abandonment,
which nearly equals the cumulative production to date. Team
members said this will be foregone without the continued
application of advanced geological and engineering technology.
This prediction holds true for natural gas
reservoirs as well, where an estimated 10 trillion cubic
feet, or the equivalent of cumulative production thus far,
will remain unrecovered without advanced recovery technology.
"Rather than being unattainable, we believe
a large volume of this remaining oil and gas is recoverable
through the strategic, or targeted, deployment of advanced
reservoir characterization technologies that should incorporate
3-D seismic and virtual reality imaging," Tyler said.
"In fact," he added, "incorporating virtual
reality imaging to reservoir characterization should be
an integral part of all advanced reservoir characterization
programs along the Gulf Coast."