NATURALLY FRACTURED RESERVOIRS
YEAR 2010
WELCOME TO OUR HOME
WE SPECIALIZE IN THE STUDY OF NATURALLY FRACTURED RESERVOIRS WORLDWIDE
“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 2010)
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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