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E X T R A C T S F R O M P R E V I O U S
W O R K
This page shows some extracts from previous work to highlight the
special skills we have available.
Porosity and Permeability Estimation
The three Figures below show comparisons between core and log measured
porosities and permeabilities in a gas-bearing
sandstone reservoir. The first Figure is a depth plot showing all the
data, while the second plot shows the difference between the core and
log derived porosities.The third plot shows the differences between the
core and log derived permeabilities.
The porosity and permeability estimated from
log
measurements in Unknown-1 are compared with those from core over the
same interval. The curve PHIT is total porosity from logs, while cporis
is the core porosities corrected to in-situ stress. The curve kis is
the in-situ estimate of log permeability, while cpermis is the core
permeability corrected to in-situ stress and fluids.
The differences between the log and core
porosities are shown as a histogram for Unknown-1. Note that the log
porosities have not
been scaled to match the core data! The match is still excellent owing
to the correct selection of grain density and an appropriate porosity
model.
The differences between the log and core
permeabilities are shown as a histogram for Unknown-1. Note that the
log permeabilities have not been scaled to match
the core data! The match is still excellent owing to selection of an
appropriate permeability model.
Saturation-Height Reconciliation with Logs
The Figure below compares water saturations from logs with estimates
from drainage, imbibition and residual saturation-height functions. The
match (green curve) is excellent.
Porosity based drainage and imbibition
saturation-height functions are compared with the client’s
wireline log evaluation. The red SWT curve is the log-based water
saturation, while the green SWI curve shows the residual hydrocarbon
relation at the base of the column and the imbibition based water
saturation at the top of the column. The blue SWD curve is the drainage
saturation-height function i.e what the column would have looked like
had there been no production.
Conventional vs. NMR Log Comparison
The Figure below compares porosities and permeabilities from NMR
logging with those from the conventional log interpretation. The
comparison is excellent.
The porosities and permeabilities from
conventional log interpretation are compared with those from NMR log
interpretation in Unknown-2. The curve PHITC is the total porosity from
density log interpretation, while TCMR is the total porosity from the
CMR log. The curve KISC is the in-situ permeability estimate from
conventional logs, while KTIM is the permeability estimated from the
CMR log using a Coates-Timur Model.
Exploration Well Evaluation
The Figure below shows the Petrophysical Evaluation delivered to the
client within 3 hours of data receipt, compared with the later MDT
permeability estimates. The comparison is again very good!
The petrophysical evaluation for well
Unknown-3.
Of particular note is the comparison between the conventional log
derived permeability estimates (kis) and the wireline formation tester
build-up based permeability estimates (mobi). It is also interesting to
note comparison between the hydrocarbon saturations (Sh) and the
estimated irreducible water saturation (Swirr) from a nearby Field.
Again, the comparison is excellent.
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