Page 248 - Well Logging and Formation Evaluation

238 Well Logging and Formation Evaluation

For R = 0.7, the DEMV becomes $-0.188M; the R required for 0 DEMV
becomes 0.80.

If there is a 50% chance of the zone being flushed, and the tool pre-
dicts the zone to be unflushed with 70% reliability but is only reliable 60%
of the time in predicting a flushed case. When the zone is flushed, the
EMV becomes:

+
.
.
*
.
()
.
DEMV R =-002 0 70 05* (14. )+ (04. ) 05* . * ( -22 ) = 003$ . M
CHAPTER 9: EQUITY DETERMINATION
Exercise 9.1: Optimizing Equity

Note that the test2 well has significantly better sand quality than test1.
It is also updip and does not see the OWC.
You would obviously maximize your equity if the determination were
to be done on the basis of GBV or NPV. However, you have no technical
case to support this, so you must expect that the final basis will be on
HCPV. Since neither well encountered gas, there is no gas conversion
factor to consider in this example.
The test2 well was drilled with OBM and it appears that the induction
tool is saturating, giving unrealistically high values of R t that in turn lead
to very low Archie water saturations.
On this basis you should definitely push for a saturation/height based
model for the saturations:
Within the range of reasonable V sh cutoff values that could be chosen
there is no dependence between V sh cutoff and equity. This is hardly sur-
prising since the sands are very well defined.
Increasing matrix and fluid densities, both of which have the effect of
increasing the porosity, is in your advantage. This is because the test2 oil
company gains proportionally less than you do when their porosities are
already better than yours.
It also pays you to define a saturation/height function that gives more
oil. Hence lowering the a value and making the b value more negative
both improve your equity position.