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7th Middle East Geosciences Conference and Exhibition
Manama, Bahrain
March 27-29, 2006
Pore
Geometries and Their
Relationships to Reservoir Properties for the Arab D Limestones
Saudi Aramco, Box 10607, Dhahran 31311 Saudi Arabia, phone: 966 3 874 5176, edward.clerke@aramco.com
The Rosetta Stone project was launched in 2001, to acquire a much more extensive data set from 10 cored wells and containing: geological, petrophysical and reservoir property data.
Four porositons (distinct and separable pore
-throat size distribution modes) are the fundamental building blocks of the Arab-
D limestone
pore
systems
. The “M” porositon (macroporosity) carries 99.98% of the permeability of the multimodal
pore
systems
. Of the three forms of microporosity, the one with the largest
pore
throats (porositon “1”) is prevalent in the best
reservoir rocks (that is, they have an “M_1” porositon combination). The presence of macropores and micropores, e.g.,
M_1, in certain of the HWM facies types causes them to act to a first approximation as dual porosity – single permeability
system.
Conclusions about the relationships between porositons and reservoir properties include:
- Efforts on permeability modeling are focused on the M porositon resulting in an improved permeability model.
- Relative permeability shows significant
pore
geometrical controls in addition to wettability, especially in that microporosity contributes to measurable relative permeability primarily through a water saturation offset.
- Among a range of M_1 dual porositon samples prepared consistently with regards to wettability, Type 1 microporosity controls the water saturation value at which the oil relative permeability curve, Kro, starts to decrease from 100%.
- Among a range of M_1 dual porositon samples prepared consistently with regards to wettability, the curve shape of the oil relative permeability curve, Kro, as it declines from 100%, is controlled only by the permeability of the M porositon and steepens as that permeability increases.
- Ultimate recovery forecasts from relative permeability concepts require knowledge of the micro and macro
pore
systems
.