Nips Paper21

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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
mailto:[email protected]:[email protected]


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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.

REFERENCES

Bell, A., Chesshire, B, Gowans,K. Jahn, F. and Wilson, C. (1990)

Training manual IV Spectial Topics. Shell Internationale

Petroleum, Maatschappij

Helander, D. P. (1983) Fundamental of Formation Evaluation. Oil

and Gas Consult. International Inc. Tulsa.

Rider, M.H. (1990) The Geological Interpretation of Well Logs.Kingsman USA

Schlumberger, (1985) Well Evaluation Conference. Nigeria

Schlumberger Ltd., Texas.


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Schlumberger, (1994) Log Interpretation, Principles and

Application (3rd edition) Schlumberger Educational Services

Houston 1.1 -4.5

Scientific Software Corporation (1983) Well logging manual,

scientific software company . New York 210-217.

Ellis, D.V. (1986) Neutron Porosity Devices- What do they

measure? First Break Vol. 4(3) 1-8

Brassard, G and Bratley, P. (1988) Algorithmics- Theory and

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Ochi-Okorie, A.S. (1993) Computer Fundamentals, Introduction

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Visser, R and Baaren, J.P. (1985) Optimasation of the Shale

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Brightman, R.W and Dimsdale, J.M (1986) Using Computer in an

information Age. Delmar Publishers, Inc, New York

Argand, M, Glouse, H Straley, C Tomanic,J. Winker, K (1989)

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Robertson, L.A (1992) StudensGuide to Program Design.

Butterworth- Heinemann Ltd, Oxford. 175-180.

Telford, W.W. Geldart, L.P and Sheriff, R.E (1990) Applied

Geophysics (2nd edition). Cambridge University press Cambridge

770

Asquith, G.B and Gibson, C.R. (1983) Basic well Log Analysis for

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