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Input technical: reservoir
parameters
Reservoir parameters define how hydrocarbon
pore volume estimates are transformed into estimates of surface
volumes of oil and gas. They also define the factors that
are used to calculate quantities of associated gas and condensate.
For the Alpha case, the following estimates
have been provided for the two parameters that you need to
estimate for an oil case:
- Oil formation
volume factor (Bo) is 1.23 (Uniform with min=1.1, max=1.35)
- Gas-Oil Ratio
(GOR) is 200 scf/STB (Uniform with min=180, max=220)
Again, you can enter each parameter
estimate as a constant – implying that there is no uncertainty
in the estimate. Or you can signal uncertainty by entering minimum
and maximum values that imply a certain range in the estimate.
Assume that you have no reason to expect
any value in the estimates to be more likely and that there
is a 10% uncertainty range on all parameters. You therefore
enter the estimates as uniform distributions with the oil
formation volume factor as varying from 1.1 to 1.35 and the
GOR as varying from 180 to 220.
Note: The two other parameters
are irrelevant for this oil case and need not be edited.
Input technical: risk parameters
Risking is critical. The basic GeoX
analytical risk model supports a consistent and systematic
analytical approach to risking across prospects in a play.
You do this by distinguishing between risk factors that are
common to all prospects in the play and conditional risk factors
that can vary from prospect to prospect.
The default value for all risk factors
is 0. As a result, if you do not edit the risk factors, the
risked resource estimates will also be 0.
In the standard GeoX risk model, there
are four risk factors that are assumed to be common to all
prospects in a play: probability of source rock, probability
of migration, probability of timing and probability of reservoir
presence.
Given that Alpha is in a play that
has proven hydrocarbon accumulations, all the common (marginal)
risk factors should be set to 1.
There are three conditional risk factors:
probability of adequate trapping, probability of reservoir
quality and probability of hydrocarbon accumulation. The conditional
factors are estimated assuming that the common factors are
all OK.
Assume the following conditional risks
factor estimates that imply that trapping is the factor with
the greatest risk:
- Probability of
adequate trap is 0.5
- Probability of
effective porosity is 0.9
- Probability of hydrocarbon
accumulation is 0.9
Calculate results
Once you have reviewed and edited all
the input parameter estimates that are relevant for the Alpha
oil case, click the CALC toolbar button or press F9. The system
computes estimates of in-place and recoverable resources.
You review the output by browsing the result pages.
Results technical: In-place and
recoverable resources
The in-place and recoverable resources
pages have the same format. They show for each hydrocarbon
phase, the unrisked and risked estimates of resources. The
conditional risked estimate considers only the conditional,
prospect level risk while the unconditional risked estimate
also considers the common, marginal play-level risk. In the
Alpha case, the marginal risk is 1 and therefore the conditional
and unconditional estimates are identical. The mean expected
recoverable oil resources are 16.8 MBBL with a 5% chance of
a 24.8 MBBL accumulation.
Other result pages show the contribution
of the different input parameter estimates to the uncertainty
in the calculated resource estimates (variance diagram), the
reservoir yield factors (yield) and a graphical display of
the total hydrocarbon resources in oil equivalents (resource
diagram). For example, the variance diagram for recoverable
oil indicates that uncertainty in your porosity estimates
account for 43.2% of the variance in the calculated recoverable
oil resources
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