American Oil and Gas Reporter - November 2015 - 90

SpecialReport: MWD/LWD Technology
From that value, and an estimated fluid
value, porosity can be calculated. The
plots at the top and bottom left of Figure
3 show the calculated Hingle value in
the y-axis displayed on a linear scale
with two porosity ranges. Adding BVW
lines to the Hingle plot shows that the

points with the lowest BVW values on
the southern edge of the data are at
BVWirr (Swirr), and should produce only
hydrocarbons. Those at the northwestern
edge of the data are in the water-bearing
zone, while the points between the two
edges will yield some combination of

FIGURE 4
Pattern Recognition Game Board with Default Parameter Values

FIGURE 5

Wet

Transition

Irreducible

Ideal Log Data with Range of Porosities in Wet,
Transition and Irreducible BVW Zones

90 THE AMERICAN OIL & GAS REPORTER

water and hydrocarbons.

Game Board Concept
Figure 4 shows the entire pattern
recognition game board with "ideal" data
plotted before making any modifications
to the initial default parameter values
(while standard spreadsheet software was
used to implement the method as a proof
of concept, the technology's capabilities
are better suited to petrophysical or geological software).
The upper left-hand image shows the
game board control area. The user can
change the values of Archie parameters,
matrix and fluid parameters, and BVWirr
using simple slider bars and arrows. The
porosity calculation (input calculated
porosity, density porosity, or sonic porosity) can be selected, which activates the
appropriate matrix and fluid values. Water
saturation and BVW lines also can be
changed.
As shown, the spreadsheet also consists
of two Buckles plots (linear and logarithmic), three Hingle plots (calculated
porosity, bulk density, and sonic travel
time), and a Pickett plot. The Pickett and
Hingle plots have both Sw and BVW
lines. Porosity, water saturation, and
BVW are calculated each time a parameter
value is changed.
The data (shown in log format in
Figure 5) are constructed to have a range
of porosity with a water zone, a transition
zone, and a zone of BVWirr. The value
of Swirr varies with porosity so that
BVWirr is a constant. The game board
has parameters defaulted to common values. For example, m is equal to n at 2.0,
the tortuosity factor is 1.0, and formation
matrix/grain density (RHOma) is 2.71
(limestone), while Rw is set at an arbitrary
value of 0.01.
The Hingle bulk density plot shows
the choice of RHOma to be incorrect. It
does not align with the plotted points as
does the Pickett plot, where the southwestern points show a curved rather than
a straight line. The misalignment of the
suspected water-bearing points on the
Pickett and Hingle plots is similar to
points at the east side of the Buckles
plots as well. The user could start the iteration of the data by changing any of
the variables, but the RHOma and Rw
variables probably would have the greatest
impact.
As the Sw lines and data points begin
to converge, the user could see from the
Pickett plot that a change in m would be
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