2010
NATURALLY FRACTURED RESERVOIRS
WELCOME TO SERVIPETROL’S 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.”
“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.”
"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 Silvia 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)
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or questions please email: aguilera@servipetrol.com
Servipetrol Ltd.
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