American Oil and Gas Reporter - November 2015 - 86

SpecialReport: MWD/LWD Technology

Approach Speeds Data Interpretation

86 THE AMERICAN OIL & GAS REPORTER

FIGURE 1
Linear (Left) and Logarithmic (Right) Buckles Plots
BVW=0.05

1.0

BVW=0.07
BVW=0.1

BVW=0.15

BVWirr=0.04
Data

0.6

BVWirr
Porosity

0.8

Porosity

0.1

0.4

sin

0.01
0.01

0.2

0.1
Sw

1.0

BVWirr
0
0

0.2

0.4

0.6

0.8

1.0

FIGURE 2A
Pickett Plot with Sw Lines at Data Point Locations
1.0

ing

a*Rw

De
cre
as

DENVER-From its beginnings, petrophysics has used graphical displays to
identify zones of interest, speed the identification and analysis of key reservoir
properties, and determine the parameters
needed to calculate those properties.
Graphical pattern recognition displays
range from "quick look" depth displays
of raw log data to cross-plots and 3-D
views of acquired petrophysical data.
In recent years, the focus of pattern
recognition techniques has turned from
determining reservoir properties such as
porosity and water saturation to predicting
and analyzing the parameters needed to
calculate reservoir properties in a more
detailed and robust manner. The goal is
to leverage proven methods in new ways
to improve both the speed and accuracy
of petrophysical interpretations.
A new methodology combines three
conventional pattern recognition techniques that are not usually linked: Buckles,
Hingle and Pickett plots. This approach
allows users to simultaneously determine:
* Archie equation porosity/cementation (m), saturation (n) and water resistivity
(Rw) parameters;
* Matrix parameters for converting
bulk density or acoustic slowness to
porosity; and
* Irreducible bulk volume water
(BVWirr) to help predict water production
from hydrocarbon-bearing zones.
The data from all the plots are displayed
simultaneously in a "game board" format.
The graphical representation is referred
to as a game board because, as with a
board game, a change made directly on
the board will cause other parts to respond
immediately (like game pieces). In this
way, adjustments made to any parameter
determined from one plot are reflected
in the other plots as well as the computations derived from those plots.
The interpretation process is shortened
by integrating a number of pattern recognition techniques and predicting parameters simultaneously. The user determines
interpretation parameters in an interactive
mode, and the parameters are more coherent, since they are determined together
rather than independently.
The ability to change the values of

Pattern Recognition Techniques
Buckles, Hingle and Pickett plots are
well established and proven pattern recognition techniques. The Buckles method
plots water saturation (Sw) versus total
porosity. In intervals at irreducible water
saturation, the product of water saturation
and porosity is a constant (the Buckles
number). When porosity is plotted against
water saturation for those points, the resulting curve is a hyperbola, while points
in a transition zone plot at values above
the points at irreducible saturation.

any parameter on the game board display,
and immediately see how it subsequently
impacts the other parameters and values
such as calculated porosity, water saturation and bulk volume water, allows the
petrophysicist to try different interpretive
scenarios to quickly determine which results best honor all the data. In addition,
information such as core measurements
can limit or set the values of some parameters while still allowing the values
of other parameters to be determined in
the context of the other data.

Porosity

By Daniel A. Krygowski
and Robert M. Cluff

0.1
Slope = -1/cementation exponent, m
Sw=1.0
Sw=0.8
Sw=0.6
Sw=0.4

Sw=1.0

Sw=0.2
0.01
0.01

0.1

10
Resistivity

100

1,000

American Oil and Gas Reporter - November 2015

Table of Contents for the Digital Edition of American Oil and Gas Reporter - November 2015