NATURALLY FRACTURED RESERVOIRS
YEAR 2011
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WE SPECIALIZE IN THE STUDY OF NATURALLY FRACTURED RESERVOIRS WORLDWIDE
“Many
naturally fractured reservoirs are composed of matrix, fractures and
non-touching vugs (it can also be any other type of non-connected porosity that
can occur, for example, in intragranular, moldic
and/or fenestral porosity). An improved triple porosity model is presented that
takes into account these different types of porosities. The model can be used
continuously throughout a reservoir with segments composed of only matrix
porosity, or only matrix-fractures, or only fractures-vugs, or the complete triple
porosity system.” A. Al-Ghamdi, B. Chen, H. Behmanesh, F, Qanbari and R.
Aguilera, SPE Reservoir Evaluation and Engineering (August 2011).
“271
wells producing exclusively from the Nikanassin and equivalent formations in a
very large area of more than 15,000 km2 in the Western Canada Sedimentary basin
(WCSB), Alberta and British Columbia, Canada, have been evaluated with a view
to determine the distribution of cumulative gas production and the
possibilities of intensive infill drilling… Because the
Nikanassin is considered a continuous gas accumulation [definition by Schmoker (2005)], the results of the present study open
possibilities for drilling thousands of Nikanassin wells.”N.
Solano, L. Zambrano and R. Aguilera, SPE Reservoir Evaluation and Engineering
(June 2011).
“This
study presents an integrated workflow for modeling the low permeability Doig gas
reservoir. A stochastic geostatistical reservoir
model was developed based on concepts emanating from an outcrop analog analyzed
with terrestrial LiDAR technology and 60 wells that represent the fundamental
rock characteristics, structure, facies proportions and petrophysical
properties of the Doig Anomalously Thick Sandstone Bodies (ATSB). Structural
tops were interpreted from well logs and permeability/porosity relationships
established from quantitative log analysis and core-log calibration.”H.
Deng, R. Aguilera, M. Alfarhan, L. S. White, J. S. Oldow,
and C. L. Aiken, SPE Journal of
Canadian Petroleum Technology (May 2011).
“Subsurface
fluid injections, such as wastewater disposal, waterflooding,
and CO2 sequestration, cause reservoir dilation. The reservoir dilation induces
displacements in the overburden extending up to the ground surface and
resulting in surface heave. Previous studies have illustrated that it is
possible to delineate the extent of the reservoir dilation from the surface
heave measurement using an inverse technique. This paper proposes that the
inverse technique can be extended to estimate the growth and propagation of the
reservoir dilation during the fluid injection if the surface heave is monitored
continually.” Li
Ping Qiao, R.C.K. Ron Wong and Roberto Aguilera, SPE Journal
of Canadian Petroleum Technology (February 2011).
“The
importance of North, Central, and South America is highlighted by a hydrocarbon
output during 2007 that accounted for 25% of the world oil production and over
31% of the natural gas production. It is concluded that there is a large
petroleum endowment in North, Central and South America that will last for
several decades and will help to contribute significantly to the energy needs
of these regions. It is recommended to actively pursue research and development
of this endowment.” Roberto F. Aguilera and Roberto Aguilera, SPE
Economics & Management Vol. 2, No. 2 (October 2010).
“A
model is developed for petrophysical evaluation of naturally fractured reservoirs
where dip of fractures ranges between zero and 90 degrees, and where fracture
tortuosity is greater than 1.0. This results in an intrinsic
porosity exponent of the fractures (mf) that is larger than 1.0. The
finding has direct application in the evaluation of fractured reservoirs and
tight gas sands, where fracture dip can be determined, for example, from image
logs.” Roberto Aguilera, Journal of Canadian Petroleum Technology
(September 2010).
“A
method, based on factual observations of naturally fractured reservoirs in
several countries is presented for estimating distribution of hydrocarbon
cumulative production in wells drilled in fractured reservoirs of types A, B or
C. These observations indicate that in reservoirs of type C most of the
cumulative production is provided by just a few wells while the majority of the
wells contribute a small part of the reservoir cumulative production. In
reservoirs of type B the number of wells contributing significantly to
cumulative production becomes larger relative to the case of type C reservoirs.
Finally in reservoirs of type A, a large number of wells contribute to field
production, as compared with type B reservoirs.” Roberto Aguilera, Journal
of Canadian Petroleum Technology (August 2010).
“Most
tight gas reservoirs we are familiar with contain the presence of natural
microfractures. However, these fractures are usually ignored in pressure
transient analysis and the reservoirs are evaluated nearly always using single
porosity models. One possible reason is the complex behavior of the
hydraulically fractured, naturally fractured tight gas reservoir, which causes
their build up plots to look sometimes like single porosity reservoirs.” Ashkan Jahanbani Ghahfarokhi and Roberto Aguilera, Journal of Canadian
Petroleum Technology (October 2009).
“The
petrophysical analysis of fractured and vuggy reservoirs has been an area of
abundant interest in the oil and gas industry. For example, a key ingredient
for successful completion of wells in naturally fractured tight gas formations
is the ability to distinguish gas from water-bearing intervals. Proper
estimates of petrophysical parameters, including the porosity or cementation
exponent m, play an important role in correct estimations of water saturation
(Sw).” “… the change in fracture dip
can have a large effect on the value of m. Not taking this into account can
lead, in some cases, to significant errors,” Carlos G. Aguilera and
Roberto Aguilera, Journal of Canadian Petroleum Technology (July 2009).
“At
present, while society is deeply concerned about the environment, hydrogen
might emerge as a white knight. There is evidence that, since 1850, the
relative hydrogen consumption has been increasing steadily”. “In
the case of oil and natural gas, eventually there will be a maximum peak in
production. The question is if it will occur sooner or later, and if it will
happen because of depletion or because of substitution to other energy sources,
perhaps unconventional or non-fossil. Recent work suggests that there are
enough hydrocarbons, available at production costs far below current prices,
for society to substitute alternative sources before depletion becomes a
problem,”
“To
assist with improvements in tight gas recoveries and the economic extraction of
this resource we have created the GFREE research program at the Schulich School
of Engineering, University of Calgary. The acronym stands for a
multi-disciplinary program that involves: (1)Geoscience
aspects (G), (2)Formation evaluation by petrophysics and well testing (F),
(3)Reservoir drilling, completion and stimulation (R), (4)Reservoir Engineering
(RE), and (5)Economics and
Externalities (EE). To convert the large Canadian resource into reserves,
technological advancements will be required. The GFREE research primarily
targets tools and methodologies that will enable producers to quickly,
effectively and efficiently assess the economic potential of tight gas resources.”
Roberto Aguilera and Thomas G. Harding, Journal of Canadian Petroleum
Technology (December 2008).
“A
limited amount of information suggests that tight gas formations are generally
found in older rocks in the same petroleum provinces where ‘conventional
gas’ is produced. This observation, supported by various examples and
illustrated with a gas resource pyramid, permits the use of conventional gas
formations as a proxy for the presence of tight gas in basins and petroleum
provinces throughout the world. A variable shape distribution (VSD) model leads
to the conclusion that there is a significant potential endowment in tight gas
formations that rivals the endowment from conventional gas accumulations
(15,100 tcf). Thus, tight gas formations have potential to provide a
significant contribution to global energy demand estimated at approximately 722
quads by 2030.”, Roberto. F. Aguilera, Thomas G. Harding, Federico
Krause, R. Aguilera, 19thWorld Petroleum Congress, Madrid, Spain (June
29-July 3, 2008).
“The model presented in this paper
leads to what we are calling the “2030 1/3 forecast”. It indicates
that global energy needs will be met by approximately 1/3 of liquids, 1/3 of
solids and 1/3 of gases by 2030… If there is a supply problem in the near
future, it will not be the result of depletion, but rather the failure of
society to invest in the research and development of technology needed to
provide conventional oil and gas, as well as alternatives, on a timely
basis.” Roberto F. Aguilera and Roberto Aguilera, SPE
paper 110215 (November 2007), Journal of Petroleum Technology (May
2008).
“Historically,
non-fractured aquifers have been attached to material balance calculations of
naturally fractured reservoirs. This is not realistic from a geologic point of
view as it implies that fractures are present in the oil portion of the
reservoir, but disappear the moment the water oil contact is reached. It is
shown that the use of an unfractured aquifer in a
naturally fractured reservoir can lead to erroneous oil recovery
estimates.” Roberto Aguilera, Journal of Canadian Petroleum Technology
(July 2007).
“Historically,
compressibility has been neglected when carrying out material balance
calculations of conventional reservoirs producing below the bubble point. This
assumes that the reservoir strata are static. It is shown, however, that under
some conditions, fracture compressibility can have a significant impact on oil
rates and recoveries of naturally fractured reservoirs as the fracture
permeability and fracture porosity are
stress-dependent.” Roberto Aguilera, Journal of Canadian Petroleum
Technology (December 2006).
“The
underlying but important message is never to overlook low-porosity intervals in
naturally fractured reservoirs. It is safer not to use porosity as a cutoff
criterion in fractured reservoirs, particularly in exploration wells, unless
there is some solid supporting information that asserts the opposite. The use
of a porosity cutoff can leave as undiscovered a reservoir that, if tested,
could prove to be commercial.” Roberto Aguilera, AAPG Bulletin
(May 2006).
“In
addition to rock fabric, it is possible to have in a Pickett plot, water
saturation, capillary pressure, pore throat aperture, Kozeny’s
constant, permeability, process speed, and height above the free water table.
The integration of these geologic, petrophysical and reservoir engineering
properties permits determination of flow units and a more rigorous
characterization of carbonate reservoirs. The method helps to reconcile geology
to fluid flow.” Roberto Aguilera, AAPG Bulletin (April 2004).
“There
are instances where the reservoir is composed mainly of matrix, fractures and
non-connected vugs. In these cases a triple porosity model appears more
suitable for petrophysical evaluation of the reservoir. A new technique is
presented for these types of reservoirs that is shown
to hold for all combinations of matrix, fracture, and non-connected vug
porosities.” Roberto F. Aguilera and Roberto Aguilera, Petrophysics
(March-April 2004).
"If
total porosities and resistivities of the composite system are used on a
Pickett plot when the partitioning coefficient (v) is constant, then the usual
straight lines for fixed values of water saturation are not obtained. In this
case, the Pickett plot results in downward concave lines. Not recognizing this
effect might lead to significant errors in the calculation of water
saturation." Roberto Aguilera, Journal of Canadian Petroleum Technology
(December 2003).
"Ultimately,
the simulation indicated that by producing the largest possible amount of water
from the wells in the north and the south of the structure that had been killed
by water, the field would be saved and the ultimate gas recoveries would be
increased." R. Aguilera, J. J. Conti and E. Lagrenade,
SPE Reservoir Evaluation and Engineering (December 2003).
"We
have found that some of the models for non-connected vugs fail for certain
combinations of matrix and non-connected vug porosities. The reason for the
failures is an improper scaling of the matrix porosity." Maria S. Aguilera
and Roberto Aguilera, Petrophysics (Jan-Feb 2003).
SERVIPETROL
Techniques
for evaluation of dual and triple porosity reservoirs, flow units, rock fabric,
pore throat aperture, permeability, capillary pressure, and height above the
free water table are incorporated in Servipetrol's
Fracture Completion Log. The techniques were published recently by Dr. Roberto
Aguilera in leading scientific journals of the oil and gas industry.
The
scope of projects undertaken range from brief informal discussions with
clients, to detailed, fully documented, comprehensive
studies. Our final reports include definitive conclusions and recommendations.
We can work in conjunction with client geologists and engineers or we can
develop completely independent studies.
Training Services (Year 2011)
Industry-Related
Links
- Naturally Fractured
Reservoirs
- APEGGA
(ALBERTA, CANADA)
- Society
of Petroleum Engineers (SPE)
- Canadian
Well Logging Society (CWLS)
- The
Petroleum Society of CIM
- Canadian
Society of Petroleum Geologists (CSPG)
- American
Association of Petroleum Geologists (AAPG)
- H.
K. van Poollen
For
comments, suggestions, or questions please email: aguilera@servipetrol.com
903 - 19th Avenue SW, Suite 502
Calgary, Canada T2T 0H8
Ph. (403)2662535, Fax (403)2648297
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2011 Copyright by Servipetrol Ltd. All rights reserved.