nips paper21
TRANSCRIPT
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THE VISUAL BASIC PLOTTER MANAGER: MEETING THE CHALLENGES
OF WELL LOG DIGITAL DATA CONVERSION
By
A.J. Ilozobhie*, E.E. Okwueze*, F.I.N. Faithpraise*, A.M. George*, and
D.O.Obi+
+Physics department,University of Calabar. Calabar
*Geology department, University of Calabar, Calabar
E-mail: [email protected]
Abstract
A geophysical well log plotter manager was developed using
visual basic software in order to address the challenges faced by
researchers in converting digital well log data to well log curves
so as to facilitate qualitative well log interpretation.
The plotter was used to plot well log curves of five oil wells
namely: Kinasar, Gabiu, Wadi, Masu and Krumta in the Bornu
basin. The advantages of the plotter over Excel were enumeratedwhile its limitations as compared to some standard oil company
well log plotter softwares were outlined. The generated log curves
were correlated with the well log curves given by the company
and the result show a perfect curve match.
Introduction
At the reconnaissance stage of hydrocarbon exploration, the
first target is to delineate the basin in which a thick sequence of
sedimentary rock has been deposited. It is those basins that
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harbor petroleum source rocks e.g. shale which having been
deeply buried and subjected to suitable temperatures generated
and expelled oil and gas into porous and permeable reservoir rock
e.g. sandstones, limestone etc. at this stage, only a generalized
picture of the subsurface in required and mostly gravity and
magnetic methods are utilized to indicate area of seismic
exploration. The next phase of exploration is to use the seismic
reflection method in the identification of geologic structures and
for features that hold promise of being oil or gas traps. These
structures include anticlines, faults domes, pinchouts and
unconformity etc. the next phase is to use well logging technique
to explore into the above structures to determine the volume of
recoverable hydrocarbon, location of reservoir, the fluid content,
fluid pressure etc. from the log signature both qualitative and
quantitative evaluation of hydrocarbon bearing zones are carried
out.
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Fig. 1.0 Typical Well log procedures
Well logging in Hydrocarbon exploration
Well logging is a standard operation in petroleum
exploration. It involves measuring the physical properties of
surrounding rocks (or formation) with a sensor located in a
borehole or well. The record of the measurement(s) as a function
of depth is called a well log (Telford et al., 1990). In common
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usage, the word log may refer to a particular curve; a suite or
group of curves, a logging tool (or sonde) or the process of
logging (Asquith and Gibson, 1983).
The principal objectives of any well logging exercise in the
petroleum industry include:
- The identification of geological formations and fluids
- Correlation between holes
- Evaluation of the productive capabilities of reservoir
formations encountered by the drill bit
Different logging tools are used to acquire different
geophysical properties such as formation thickness and
lithology, porosity, permeability, proportion of water and/or
hydrocarbon saturation, stratal dip and temperature (Keary
and Brooks, 1991). Each of the logging tools has particular
characteristics that depend upon the physics of the
measurement of their particular parameters, and upon the
borehole environment. These characteristics affect the log
quality (Bell, et. al., 1990 and Glover, 2000).
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Aims of present study
The presentation of well log data in digital format has
greatly hampered qualitative interpretation among many
researchers that work with such data, since most of the software
used for the conversion of the data to well log curves are not
made available to the researcher and if available, are very
expensive, hence the plotter manager was developed to meet this
challenge.
Qualitative (diagnostic) interpretation of well log
There are basically two forms of well log interpretation;
qualitative and quantitative. These two are usually inseparable.
To perform a quantitative interpretation, one has to carry out a
qualitative assessment of the formation encountered in the well.
The qualitative interpretation is well log interpretation by
visual inspection. It is based on the appearance of log curve(s) or
the shape(s) of log curve(s).
Curve features provide information that enable relatively
quick identification of lithologies, permeable beds, gas-bearing
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zones etc. for instance permeable beds are often pickable from
evidence of invasion as shown by the separation of resistivity
logs and high value recorded by caliper log. Typical gamma ray,
Spontaneous potential and neutron response curves provide
information that facilitates the identification of different types of
formation. While the available porosity logs (sonic, neutron and
density tools) compliment. The foregoing confirmed likely
reservoirs rock and often buttress by the high sonic transit
interval time while the density and neutron logs give relatively
low values. Although the preceding logs aids in determining the
quality of possible prospects, yet do not reveal whether they
contain hydrocarbon. To obtain this information the resistively
tools are utilized. They give very high reading in oil and gas zones
because these substances are non- conductive and the
characteristics divergence between the neutron and formation
density log curves because of an increase in density porosity and
a corresponding decrease in neutron porosity is indicative of a
gas bearing zone. This divergence effect is called the gas effect.
Many of the curve features on a log to a trained observer,
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actually mean oil (or gas) or water (Ellis, 1986, Helander, 1983
and Schlumberger, 1991). Hence, the routine use of qualitative
interpretation in the preliminary identification of potentially
productive hydrocarbon bearing zones (Fig. 2.0)
The shape of the log curve also aid in proper environmental
depositional study.
Fig. 2.0 Common Log curve and their qualitative interpretation
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THE Plotter Manager
The Plotter Manager is customized software for analysis and plotting of
well log data. It is developed around the Microsoft .NET Framework 2.0with Microsoft Visual Basic as the programming language. It is User-
Friendly software with a multi-graphical user interface (M-GUI) also
known as the Single Plotter, Dual Plotter and the Multi Plotter. Unlike
the convectional Excel program which has limitation in data input with
specific skills the plotter manager has no limitation in this area
(Robertson, 1992, Ochi- Okorie, 1993). Various files that made up the
plotter manager software are displaced below:
-Load data (mnufileload data_click): Load the well data flie via thesystem open dialog box
- Prepare graph (preparegraph_click):Pre construct the graph sheet for
plotting based on the well data file either as log or linear scale
-Worksheet form (frmworksheet.vb):
-Capture data (mnucapture_click):Extracts the loaded well data
into a worksheet for data processing
The block diagram (Fig. 3.0) below represents the internal
architecture of the software which is built around the following basic
modules:
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Fig. 3.0 Block diagram of the Plotter Manager internal architecture.
Multi-Graphical User Interface:
Controls the plotting view of the software to the following:
Single Plotter: Used to plot each of the logged data in a well log file
discretely per view. Based on the current plotted data, the calibrator
changes the view from linear to logarithmic.
Dual Plotter: Used to plot both linear and logarithmic data in a well
log file. The view is split in two, with the left view for linear and the
right for logarithmic data.
Multi Plotter: Used to plot both linear and logarithmic data in a welllog file. The view is split in three, with the left and right view for linear
and the middle for logarithmic data.
Plotter Graphics Engine:
Multi-
Graphical
UserInterface
Plotter
Graphics
Engine
PrinterManager
Application
Processing
and I/O
Logic
Calibrator
Module
Data-File
System
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Handles the processed well log data using its 2D vector graphics
engine and converts the data into graphic points and unique color
symbol for plotted graphs to enhance user perception of the result.
Printer Manager:
Controls the conversion of the processed and plotted well log data to
hard copies (Printer). It handles print and preview operations, page
settings and plotting formats either as detailed, economical or analysis
mode.
Calibrator Module:
Generates and manages the graph marking logic for linear and
logarithmic plotting, which is used both by the Plotter Graphics Engine
and the Printer Manager. The plotter user interface is displayed in Fig.
4.0.
Data-File System:
Well Log data file comes with the file extensions of *.txt and *.las
and the data-file system is built to read data file that comes with any
of the listed file extensions. It can also read data file with a completely
different file extension, provided its internal organization follows the
well log data file format.
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Fig. 4.0 The Plotter Manager User Interface.
Software Operation
When using the Plotter Manager on Windows XP, it runs on full
administrative privilege, therefore file operation restrictions do not
occur. However when using it with Windows Vista and Windows 7,
there may be file operation restrictions, depending on the directory on
which the data file is located. In case of such restriction errors usually
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caused by the User Account Control (UAC) of the operating system
(OS), the software must be run as an administrator.
Run software as Administrator:
1. Right-Click on the softwares executable file or its shortcut todisplay a context menu.
2. Choose Run as administrator from the displayed context menu
(Fig. 5.0).
Fig. 5.0 User Account Control (UAC) dialog box showing details.
3. On the UAC prompt that appears requesting your permission,
choose Yes.
Load Well Log data to Plotter Manager
1. Click on File menu and then click on Load Data or press
Ctrl+O on the keyboard to display a Load Data dialog box.
2. Choose the well log data file to load from the list of displayed files
and click Open (Fig. 6.0).
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Fig. 6.0 The Menu commands on the Plotter Manager.
Fig. 7.0 The Load Data dialog box.
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3. Change the Files of Type extension to All Files to display all
files in a directory in case of well log data files without the *.txt
or *.las extensions.
4. Choose the well log data file to load from the list of displayed files
and click Open.
Note: Step 3 and 4 are only important when the file extensions is
not either *.txt or *.las file format as the Files of Type is set to
Data Files (*.LAS; *.TXT) by default and only files with the
enumerated extensions are visible in the dialog.
Changing the Plotter Manager View
Click on View menu and click on the preferred view to use, either
Single Plotter, Dual Plotter or Multi Plotter. Note that whenever the
view is changed, (Fig. 8.0) previously loaded well log data are
unloaded.
Fig. 8.0 Option for viewing the plotter
Adjusting the Page
This software is designed in such a way that it afford the user to print
the plotted data with options bearing in mind that most of the hard
copies giving by oil industries comes in rolling paper. To adjust the
paper the following steps are taken:
1. Click on File menu and then click on Page Setup to display
the Page Setup dialog.
2. Adjust the paper size from the Size drop-down field under
Paper category.
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3. Adjust the paper orientation, either portrait or landscape from the
options under the Orientation category.
4. Adjust the paper margins from the margin fields under the
Margins (Inches) category.
5. Click OK to accept changes.
Fig. 9.0 The Page Setup dialog box.
Print Preview and Printing
1. Click on File menu and then click on Print Preview to display
the Print Mode dialog box.
2. Choose any of the appropriate options and click OK to display
the print preview window using the selected option.
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Fig. 10.0 The Print Mode dialog box.3. After preview, click on the Print icon on the preview window to
print.
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