isatis beginners (1)

ISATIS 2014Beginner's Guide

Beginner's Guide

Published, sold and distributed by GEOVARIANCES49 bis Av. Franklin Roosevelt, 77215 Avon Cedex, France

Web: http://www.geovariances.comIsatis Release 2014, March 2014

Contributing authors:Catherine BleinsMatthieu BourgesJacques DeraismeFranois GeffroyNicolas Jeanne

Ophlie LemarchandSbastien Perseval

Jrme PoissonFrdric Rambert

Didier Renard Yves Touffait

Laurent Wagner

All Rights Reserved 1993-2014 GEOVARIANCES

No part of the material protected by this copyright notice may be reproduced or utilized in any form or by any means including photocopying, recording or by any information storage and retrieval sys-

tem, without written permission from the copyright owner.

... There is no probability in itself. There are only probabilistic models. The only question that really matters, in each particular case, is

whether this or that probabilistic model, in relation to this or that real phenomenon, has or has not an objective meaning...

G. Matheron Estimating and Choosing - An Essay on Probability in Practice

(Springer Berlin, 1989)

1Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 About Isatis Beginner's Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72 Examples of Isatis Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .92.1 Mining: Accurate, Flexible and Reliable Geostatistics . . . . . . . . . . . . .102.2 Oil & Gas: Clarify Your E&P Assets With Isatis. . . . . . . . . . . . . . . . . .122.3 Environment: For a Reliable Mapping and a Better Cost Control . . . .14

3 Hints on Learning Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .174 Getting Help . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Getting Started With Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215 Handling Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235.1 Getting to Know the User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . .245.2 Organizing Your Data in Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315.3 Setting up the Study Environment . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345.4 Data Types you Import Into Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365.5 Exporting Results From Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385.6 Customizing the Interface Menus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .396 Tutorial: Familiarizing With Isatis Basics . . . . . . . . . . . . . . . . . . . . . .416.1 Creating a New Study. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .426.2 Importing Data Into the Isatis File System. . . . . . . . . . . . . . . . . . . . . . .446.3 Checking and Correcting Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .466.4 Selecting Samples of Interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .496.5 Computing Quick Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .526.6 Performing a Quick Interpolation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .546.7 Displaying Graphical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .576.8 Reporting & Exporting Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .606.9 Backing Up your Project & Exiting from Isatis . . . . . . . . . . . . . . . . . . .61

Getting Started with Geostatistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .637 Geostatistics in Short. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .657.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .667.2 Characterizing & Modeling a Spatial Structure . . . . . . . . . . . . . . . . . . .677.3 Ordinary Kriging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .747.4 Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .767.5 Suggested Reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .778 Tutorial: From Variography to Kriging & Simulations With Isatis. .79

28.1 Importing the Dataset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 808.2 Exploratory Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 828.3 Using Parameter Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 908.4 Fitting a Variogram Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 928.5 Mapping the Phenomenon Using Kriging . . . . . . . . . . . . . . . . . . . . . . 988.6 Performing Risk Analysis With Simulations . . . . . . . . . . . . . . . . . . . . 106

Going Further With Isatis Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

9 Displaying & Editing Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1219.1 Graphic Windows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1229.2 Printing Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1249.3 Creating Your Own Color Scales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1279.4 Familiarizing With Graphic Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . 1299.5 Tutorial: Editing Graphics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1369.6 Composing a New Graphic From Scratch . . . . . . . . . . . . . . . . . . . . . . 14510 Dealing With Polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15710.1 Delineating Areas of Interest With Polygons . . . . . . . . . . . . . . . . . . . 15810.2 Importing Polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15910.3 Displaying Auxiliary Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16310.4 Creating Polygons Directly in Isatis . . . . . . . . . . . . . . . . . . . . . . . . . . 16410.5 Customizing the Polygon Editor Displays . . . . . . . . . . . . . . . . . . . . . 16610.6 Editing Polygons and Contours . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16910.7 Discretizing Polygons to Compute Global Statistics . . . . . . . . . . . . . 17110.8 Splitting a Polygon Into Several Polygons . . . . . . . . . . . . . . . . . . . . . 17210.9 Controlling the Polygon Coverage of an Area . . . . . . . . . . . . . . . . . . 17410.10 Saving Polygons in an ASCII File . . . . . . . . . . . . . . . . . . . . . . . . . . 17511 Handling Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17711.1 Reproducing Geographical Discontinuities With Faults . . . . . . . . . . 17811.2 Importing Faults From an ASCII File. . . . . . . . . . . . . . . . . . . . . . . . . 17911.3 Creating and Editing Faults in Isatis. . . . . . . . . . . . . . . . . . . . . . . . . . 18111.4 Creating Polygonal Faults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18211.5 Simplifying Faults. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18311.6 Modifying the Priority Level of a Fault . . . . . . . . . . . . . . . . . . . . . . . 18411.7 Copying an Existing Fault System to Other Isatis Files . . . . . . . . . . . 18511.8 Saving and Managing Different Fault Systems . . . . . . . . . . . . . . . . . 18612 Batch Processing & Journal Files. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18712.1 Recording a Journal File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.2 Running a Journal File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19012.3 Editing a Journal File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19212.4 Running a Journal File in Expert Mode . . . . . . . . . . . . . . . . . . . . . . . 19613 Dealing with Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

313.1 Creating Selections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20013.2 Using Selections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20214 Exploring Your Data With the 3D Viewer . . . . . . . . . . . . . . . . . . . . .20314.1 Purpose of the 3D Viewer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20414.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20614.3 Clipping & slicing in 3D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20715 Getting to Know Isatoil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20915.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .210

15.2 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21115.3 Naming Convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21815.4 File Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22015.5 Master File Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22216 What's Next? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233

5Introduction

About Isatis Beginner's Guide 9

1.About Isatis Beginner's Guide

Thank you for choosing Isatis, the most complete geostatistical package. Isatis presents all the major methodologies that geostatistics can offer to the industry. It has been jointly developed by Geovariances and the Centre de Gostatistique de l'Ecole des Mines de Paris in Fontainebleau (France) and benefits from 40 years of experience of both contributors in the geostatistical domain.

This Beginner's Guide is a great place to start if you are new to Isatis. It contains four sections:

l Introduction

What you can do with Isatis, important tips on learning the software and how to get appropriate help while using it.

l Getting Started with Isatis

Quick overview of the package and a first Isatis project.

l Getting Started with Geostatistics

Basics about geostatistics and further references, tutorial about a standard geostatistical analy-sis, from exploratory data analysis and variography to kriging and simulations.

l Going further with Isatis objects

How to work with advanced Isatis objects and modules: graphic displays and edition, polygons & faults, batch processing, selections, advanced 3D Viewer and Isatoil.

If Isatis is not installed on your machine, please refer to the Isatis Installation Guide first.

This manual is based on Isatis version 2015, released in February 2015.

Examples of Isatis Applications 9

2.Examples of Isatis ApplicationsIsatis is the result of 40 years of experience in industrial applications and applied research in geostatistics. It is the only commercial profes-sional package which integrates all the geostatistical techniques within a user-friendly interface.Today, Isatis is widely used over the world by more than 250 private oil & gas companies, consultant teams, mining corporations and environ-mental agencies. It benefits from the expertise of a broad network of research centers and the feedback of more than 1500 Isatis users.The following pages provide a quick overview of the benefits you get from Isatis whatever your field of application is.

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2.1 Mining: Accurate, Flexible and Reliable Geostatis-ticsGeostatistics is now widely recognized by the mining industry as being a particularly effective tool at all stages from initial feasibility studies to production control. Coherent geostatistical models provide solutions to problems such as the formulation of grade tonnage relationships, the determi-nation of cut-off grades, the optimization of sampling pattern, selectivity studies and the evaluation

of the support effect on ore reserves.

Isatis offers geologists and mining engineers all the necessary tools for mining data analysis, esti-mation and simulations of deposits. Isatis is unique among geostatistics software packages, as it provides the best interactive analysis of 2D and 3D data with variogram maps and fitting, as well as many estimation techniques (simple and ordinary kriging, indicator kriging, disjunctive kriging, uniform conditioning) and grade or geology stochastic conditional simulations.

Isatis allows you to:m Make use of a fully integrated geostatistical solution;m Handle a very flexible and powerful advanced operational package;m Back your results on mathematically reliable and sound algorithms;m Make decisions based on transparent and reproducible procedures;m Handle a wide array of data, studies and analyses;m Visualize accurately your datasets and block models with the 3D Viewer module.

2.1.1 Clarify your Resources with Isatism Investigate and clean your data with Isatis unique Exploratory Data Analysis interactive

module;m Implement easily an automatic updating of your resource estimates from new drill holes

using batch procedures;m Optimize your drilling campaigns;m Obtain reliable resource estimation using multivariate modeling;m Obtain a realistic model when geology gets complex;m Assess the reserve sensitivity to SMU size and cutoffs;m Assess grade variability and evaluate the risk through simulations and estimates;m Classify your resources;m Reconcile production figures and estimates;m Facilitate the auditing and ensure clean archives of your projects with Isatis unique journal

file system.

Examples of Isatis Applications 11(snap. 2.1-1)

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2.2 Oil & Gas: Clarify Your E&P Assets With IsatisIn recent years, there has been a rapid development in geostatistics in the Oil & Gas industry. The reasons for this success are to be found in the significant contributions made by geostatistics to the analysis of spatial data and, above all, an overwhelming need for data quality and risk assessment.

Isatis is a powerful and exhaustive geostatistical package which allows geologists, geophysicists and reservoir engineers simple or complex workflows for reservoir modeling and assessing the vol-

umes and the uncertainties attached to their evaluation. Besides, Isatis full connectivity with usual market formats and its interfaces with Gocad and the RML, makes the software an incomparable tool for data integration.

m Isatis allows you to:m Get a risk indicator through the E&P cycle;m Increase data value by a secure quality process;m Enable team collaboration around a common database;m Obtain a realistic model when geology gets complex;m Back your reserve estimates on a full probabilistic framework;m Ensure clean archive of assets.

2.2.1 Time-to-Depth Conversion and Structural Modelingm Use the unique Exploratory Data Analysis interactive module for data QC;m Handle 2D and 3D faults from variography to kriging and simulations;m Get your 3D velocity cube from 3D stacking velocity processing using kriging;m Extract attributes from a velocity cube along interpreted time horizon;m Remove acquisition artifacts and noise in velocity cubes through variogram decomposition

in factorial kriging;m Perform accurate time-to-depth conversion by using multivariate techniques controlled by

seismic;m Quantify depth uncertainties using appropriate stochastic simulation algorithms;m Get the probability distribution of GRV with Isatis Volumetrics application;m Derive additional attributes using various arithmetical and morphological operators;m Determine the reservoir closure and identify the spill points.

Examples of Isatis Applications 13. (fig. 2.2-1)

2.2.2 Facies Modelingm Put the model in the original stratigraphic system by flattening the 3D grid;m Define the bedding geometry. Choose between parallel and proportional layering;m Build the 3D model of lateral and vertical facies distributions over the field from the Vertical

Proportion Curves. Distribute the facies over the 3D grid using the stochastic simulations. The various available techniques allow adapting the facies modeling to the amount of infor-mation and geology complexity.

m Petrophysical Modelingm Populate the grid with the petrophysical properties (porosity, permeability, water saturation)

from well logs using data integration techniques;m Get optimistic and pessimistic scenarios with stochastic simulation techniques;m Compute accurate volumes by zone or facies using the Volumetrics application;m Get the probability distribution of HCPV, STOIIP, GIIP from the stochastic simulations.

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2.3 Environment: For a Reliable Mapping and a Bet-ter Cost ControlGeostatistics is more and more integrated in environmental projects, whether it is for advanced mapping or risk analysis. Its added value lies in the use of auxiliary information for a better estima-tion of the phenomena you are interested in (air or soil pollution, soil properties, biomass resource, etc.) and in specific tools for quantifying the risk of exceeding thresholds (pollution, population

exposure, etc.).

Isatis is a fully integrated and operational geostatistical package which offers geoscientists a wide range of tools for in-depth data analysis, estimation and risk analysis. Its interfaces with standard GIS formats allow to integrate it in the general GIS framework.

With Isatis:m Valuate your data by a secure quality process;m Optimize your sampling strategies and investigation costs;m Take advantage of multiplicity of data sources;m Get accurate and reliable mapping;m Quantify the uncertainties and assess the risks;m Automatically update your communication media.

2.3.1 Site Investigation & Remediationm Validate your data with Isatis unique Exploratory Data Analysis interactive module;m Fully integrate all qualitative and quantitative available data so that no information is either

unused or lost;m Get a reliable estimate of contaminated volumes;m Classify the materials as contaminated or safe;m Avoid overspending by quantifying the uncertainty on your remediation budget.

2.3.2 Air Quality Monitoringm Investigate and clean your data with Isatis unique Exploratory Data Analysis interactive

module;m Combine all available information into a single database;m Take the sampling representativity and measurement errors into account;m Assess the precision of your map;m Map the pollutant at a local, regional or national scale;m Assess the population exposure to pollutants.

Examples of Isatis Applications 15(fig. 2.3-1)

Hints on Learning Isatis 17

3.Hints on Learning Isa-tis

The Beginner's Guide, the On-Line documentation tools and the Case Studies Manual are the main ways to get started with Isatis.

Using the Beginner's Guide to learn common tasksThis Beginner's Guide is a great place to start if you are new to Isatis. Find in this guide a quick overview of the package and several tutorials to learn how to work with the main Isatis objects. The Getting Started With Geostatistics part teaches you the basics about geostatistics and guides you from exploratory data analysis and variography to kriging and simulations.

Browsing the On-Line documentation toolsIsatis offers a comprehensive On-line Help describing the entire set of parameters that appears in the user interface.

If you need help on how to run a particular Isatis application, just press F1 within the window to start the On-Line Help system. You get a short recall about the technique, the algorithm imple-mented in Isatis and a detailed description of all the parameters.

Technical references are available within the On-Line Help System. They present details about the methodology and the underlying theory and equations. These technical references are available in pdf format and may be displayed on the screen or printed.

A compiled version of all the Isatis technical references is also available for your convenience: just click on Technical References on the top bar of any On-Line Help window.

Going through geostatistical workflows with the Case StudiesA set of case studies is developed in the Case Studies manual. The Case Studies are mainly designed:

18

l for new users to get familiar with Isatis and give some leading lines to carry a study through,

l for all users to improve their geostatistical knowledge by presenting detailed geostatistical workflows.

l Basically, each case study describes how to carry out some specific calculations in Isatis as pre-cisely as possible. You may either:

l replay by yourself the case study proposed in the manual, as all the data sets are installed on your disk together with the software, l or just be guided by the descriptions and apply the workflow on your own datasets.

Getting Help 19

4.Getting HelpYou have 3 options for getting help while using Isatis: the On-Line Help system, the Frequently Asked Questions and the Technical Support team ([email protected]).

Using the On-Line Help System

Isatis software offers a comprehensive On-line Help System to complement this Beginner's Guide. The On-Line Help describes the whole set of parameters that appears in the user interface. To use help, choose Help > Help in the main Isatis window or press F1 from any Isatis window.

Table of Contents and Index - These facilities will help you navigate through the On-Line Help System. They are available on the top bar of the main On-Line Help window.

FAQ - A local copy of Isatis Frequently Asked Questions is available on your system. Just click on FAQ on the top bar of the main On-Line Help window.

Support site - You may also directly access the Geovariances Support Web site to check for updates of the software or recent Frequently Asked Questions.

Register - Directly access the Ask for Registration section of Geovariances Support Web site in order to get personal login and password and access the restricted download area.

Technical References - Short technical references are available from the On-Line Help System: they present more detailed information about the geostatistical methodologies that have been imple-mented in the software and their underlying theory. In particular, you will find the mathematical formulae used in the main algorithms.

Accessing Geovariances Technical SupportNo matter where in the world you are, our professional support team manages to help you out keep-ing in mind the time and quality imperatives of your projects. Whatever your problem is (software installation, Isatis use, advanced geostatistical advice...), feel free to contact us:

[email protected]

If your message concerns an urgent operational problem, feel free to contact the Help Desk by phone: +33 (0)1 60 74 91 00.

Using Web-Based ResourcesYou can access the Support section of Geovariances Web site from the main On-Line Help menu of Isatis: just click on Support Site.

Geovariances Web site - Visit www.geovariances.com to find articles and publications, check the latest Frequently Asked Questions, be informed about the coming training sessions.

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Isatis-release mailing list - Send an e-mail to [email protected] to be registered on the isatis-release mailing list. You will be informed about Isatis updates, new releases and fea-tures.

Register - Get personal login and password and access the restricted download area.

Check for Updates - Check the Geovariances Web site for Isatis updates.

21

Getting Started With Isatis

Handling Isatis 23

5.Handling Isatis

This chapter familiarizes you with Isatis. It presents the different types of windows and widgets used in the software, as wells the data types,

import and export facilities.

24

5.1 Getting to Know the User Interface

5.1.1 Mouse and KeyboardThe User Interface of Isatis is based on window objects (widgets) that are manipulated through the keyboard and mouse devices. The terminology used throughout this Guide is presented hereafter.

5.1.1.1 Mouse ButtonsYour mouse is assumed to have three buttons (with a 2-button mouse, simulate the middle button by pressing both buttons simultaneously). The mouse buttons have special usages in graphic areas:

l Left button: to select graphic objects or to designate a point on a drawing.

l Middle button: to zoom into a part of a drawing, to drag and drop variables within file and vari-ables selectors.

l Right button: to pop up a menu.

5.1.1.2 Mouse Pointer

A mouse pointer is associated to the mouse. This symbol appears on the work space and represents the location of the mouse. Several mouse pointer symbols can be met in Isatis depending on the location of the mouse pointer and the current Isatis status:

General purpose - used in most window areas for single object selection and activation.

An action is in progress - area is not sensitive to further mouse actions.

This pointer is used in graphic areas as the select pointer shape

Blocking action - the action must be finished before doing anything else. The mouse pointer cannot be moved outside the current area.

You are currently moving a graphical object.

You want to resize a graphical object.

An action is expected in another window before input can be given to the current area.

Indicates a pending menu action.

You have to indicate a position or item to Isatis.

Indicates that you are within a text window, where keyboard input is required.

Handling Isatis 25

5.1.1.3 Keyboard Actions

The F1 key, when hit over any part of the interface, displays the On-Line help about the corre-sponding window. If available in a window, the Help key has the same function.

The following keys can be used on text widgets:

move to beginning of line move 1 character backward5.1.2 Isatis Main WindowThe following interface comes up when starting Isatis:

(snap. 5.1-1)

This Isatis Main Window is divided into three areas: the Title area, the Menu bar and the Status area. All other windows are accessed from this Isatis main window.

5.1.2.1 Title Area

The Title Area is the uppermost horizontal bar of the Isatis Main Window and contains informa-tion on:

delete the next character move to the end of line move 1 character forward kill to end of line refresh display move to next line open a new line move to the previous line kill selection undo the kill selection

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l the version number and hardware platform,

l the name of the current study, by default Isatis-Init as long as no study has been created.

5.1.2.2 Menu Bar

The Menu Bar is the horizontal bar that appears just below the title area and contains a list of top-ics. To select a topic in the menu bar you can:

l Position the mouse pointer over the topic of interest and click on the left button.l Type Alt + letter, where letter is the mnemonic underlined in the topic's name.

Selecting a topic pops up a pull-down menu that contains the available items related to that topic. Selecting a menu item followed by an arrow pops up a follow-up with more items.

The selection of a menu item followed by an ellipsis ... brings up the topic's window.

5.1.2.3 Status Area

The Status Area indicates the current state of the application, through several widgets:

l a status line that receives short messages at run-time,

l a green & yellow slider that grows from left (start) to right (end) to indicate the percentage of processing done for a given action,

l a status bitmap that indicates the current status of Isatis:

Idle mode: Isatis is waiting for an action from you.

Isatis is Running and you should wait for the end of its work.

Isatis is Running but can be interrupted if the user clicks on the STOP button. This is typical of calculations that could be long, or that the user may want to

interrupt.A run has stopped unsuccessfully, most of the time because of inconsistent or missing parameters in the application window. The program is waiting for a

Continue in a pop-up window.

Handling Isatis 27

l two bitmaps that let you know if there are messages in both Isatis Messages Window and IsatisError Messages Window:

Clicking on any of these icons pops up the corresponding window, which itself may be dis-missed with its Hide button. Two small Clear Buttons are provided to clear the Messages or

/ indicate that the Messages window is empty / contains messages.

/ indicate that the Error Messages window is empty / contains messages.Error Messages windows' contents without opening them.

l CPU time meters, displayed in the form hh:mm:ss for both the current application (top line) and since Isatis has been started (bottom line).

l the Isatis logo.

5.1.2.4 Messages & Error Messages Windows

Two separate windows are used to route errors and messages. The Messages Window is used whenever the program is asked to display some alphanumerical information (e.g. printing statistics on variables) and also when it needs to report messages about the current processing (e.g. interme-diate results, warnings, etc.).

(snap. 5.1-1)

28

The Error Messages Window is dedicated to important messages that explain why a particular processing has failed or is not possible.

You can pop up these windows by clicking on the corresponding images in the main Isatis window. Both windows are made up of a scrolling area containing the information and some of the following management Buttons:

l CLEAR, to clear the window's contents;

l SAVE, to save the contents into an output ASCII file;l PRINT, to print the contents to a local printer;

l EDIT, to edit the contents through a text editor (e.g. emacs, vi, notepad);

l HIDE, to dismiss the window from the screen.

5.1.3 Application WindowsIsatis is composed of application windows that are linked to the different menu items in the Isatis Main Window and correspond to a specific application. For instance, the Statistics / Quick Statis-tics window is dedicated to the computation of quick statistics on variables. Each application win-dow is composed of the following parts:

Handling Isatis 29

l a title at the top,

l a File Selector to define the data to work on,

l possibly a File Selector to define an output file into which some results will be stored,

l some parameters specific to the particular application,

l a Run button to execute an action (which could, possibly, take some time) related to the set of parameters defined in the window. While Isatis is performing this action (e.g. computing the

statistics in our example) the other windows are not active until the end of the RUN.

l a Close button to dismiss a window from the screen.

(snap. 5.1-2)

Note - Pressing the Close button saves all the parameters involved in the window; these parameters are automatically restored the next time the window is open. This automatic restore may be avoided if the Shift button is kept pressed during the opening of the window: in this case, all the parameters are reset to None or default values.Some graphical interactive windows (e.g. the Faults Editor) do not show a Run or Close button at first glance. In this case, these two buttons are located under the Application menu of these particular applications.

It is not compulsory to close windows after computations have been performed. You may keep sev-eral windows open at the same time and fill in parameters in any of them between different RUNs.

30

You can always press the F1 or Help while the mouse pointer is above any Isatis window; this will bring up your local internet browser in order to display all the information about the parameters required to run this particular application. A table of contents and an index help you to find in this On-Line documentation what you are looking for.

5.1.4 Graphical WindowsAll the graphical windows of Isatis are based on the same concepts. A graphical window can be edited or saved in a metafile for later use. Details and tutorials about the capabilities of Isatis graph-

ics can be found in the Displaying & Editing Graphics chapter of this Beginner's Guide.

Handling Isatis 31

5.2 Organizing Your Data in IsatisThe organization of the File System used by Isatis is fully described in the Isatis File System sec-tion of the On-line help: just press F1 or Help in the Isatis Main Window. Key aspects of this orga-nization are summarized hereafter.

5.2.1 Isatis File System

Several types of files are clearly distinguished inside Isatis:

l Data files are used to store variables and their corresponding geographical location;

l Parameter files contain the parameters associated to mathematical objects involved in geosta-tistical process: variogram model, neighborhood parameters, etc.;

l Metafiles are graphic files stored in a special internal format allowing their edition;

l Palettes and Color Scales are used for graphic displays;

l Arithmetic transformations saved in the File / Calculator application.

Data Files are presented hereafter; other types of files are discussed in further sections of this Guide.

5.2.2 Data StructureWith Isatis, you always work on one project at a time; this project is called a Study. The Study cor-responds to a disk compartment where all the datasets and procedures linked to your project are stored.

Within a Study, you are going to perform statistics on a given set of samples and interpolations on grid nodes for example. Numerical values, as well as their organization, need to be saved on disk. For this purpose, Isatis manages a hierarchical system of directories, files and variables. This sys-tem is accessible in the File / Data File Manager, that allows you to interactively visualize, man-age, get information about the organization of your Study.

The data are stored in a 4-level tree composed of:studies directories files variables

So, inside your Study, you create and manage Directories; each directory contains Files, and each file contains Variables.

In Isatis, a file is characterized by the geographical location of its contents: points, line segments, grid nodes. The coordinates are intrinsically attached to the file. All the variables defined in the file are informed at some of these geographical locations.

32

5.2.3 Naming Files & VariablesA file or variable name is constituted by a chain of maximum 49 characters. These characters may be constituted of letters, spaces or figures. Special control characters and accentuated characters are forbidden.

Nicknames may be attributed to variables and are useful in printouts to shorten the full names.

5.2.4 Types of Data Files

As Isatis deals with spatial statistics, each file sample should necessarily have two (or three) coor-dinates. The type of a Data File depends on the structures of its samples:

l Points Files are considered as a set of punctual samples in a 2D or 3D space (the 2D space is always defined by the X and Y axes).

l Polygons Files are a particular type of points file; each polygon is characterized by its gravity center and one or several contours (each contour is characterized by the coordinates of its verti-ces).

l Lines Files can be considered as a set of samples grouped into a set of lines in a 2D or 3D space. If these samples are punctual, the line is simply a link between samples. If they represent mea-surements along portions of lines, the line is also the support of the samples. A Points File can be linked to a Lines File. In fact, one sample of the Points File is attached to one line of the Lines File. This enables the storage of global information about one line (ID, name, accumula-tion, mean grade, etc.). When a Lines File is linked to a Points File, the link is deleted if one of the two files is modified (added or deleted samples), but the files are still available.

l Grid Files are considered as a set of samples exclusively distributed on each node of the grid. The coordinates always correspond to the grid nodes (the gravity centers). Grids may be rotated in 2D or 3D.

Note - Lines and Grid Files may be considered as Points Files everywhere in Isatis. In this case the variables are assumed to be punctual and located at gravity centers even if they represent cores or blocks.

5.2.5 Types of VariablesEach file contains variables. A Variable is a set of numerical or alphanumerical values. To each sample may correspond one or more Variables. Isatis deals with several types of variables:

l Alphanumerical Variables may be imported in the Isatis File System, mainly to create appro-priate selections and for graphic displays.

l Numerical Variables, generally called Float Variables in Isatis, can be imported or created dynamically whenever needed. Samples are not always analyzed and a variable may not be defined for some samples. An Undefined Value is set instead. This Undefined Value will not be taken into account during calculations. Undefined Values are identified by a character string which may be specified when importing data (it could be set to blank character or N/A for

Handling Isatis 33

example). By default, when reading a file, any blank character will be considered as an Unde-fined Value. This Undefined Value is also called ffff when used in mathematical expressions. Special types of numerical variables are also used in Isatis:m Readonly Variables are numerical variables that cannot be modified (except by specialized

operators). This is the case, for example, of variables giving the absolute or relative position of a sample in a file or the coordinates of gravity centers (or nodes) for a Grid File. These variables area automatically created by Isatis at File creation. Coordinate variables are also readonly, to avoid for instance any unwanted deletion or modification. Undefined val-

ues are prohibited in variables taken as coordinates.

m Length Variables are numerical variables that are stored in centimeters on disk at the data import and converted into the appropriate unit in displays and printouts. This is for example the case for the coordinates. The conversion operation is defined in the Preferences / Study Environment window by specifying a length unit. The conversion factor (i.e. the unit) can be different for calculation purposes and for graphical displays.

m Selection Variables are 1 bit Float variables, that can only take the value 0 or 1. A sample will be selected if the value of the selection variable is set to 1 and masked off if the value is 0. Many Isatis applications allow the use a selection during input/read File or output/write File. In the input phase, this means that some samples will not be used during the computa-tion. In the output phase, this means that you do not want the application to be performed on the masked samples.

l Macro Variables are Float Variables that contain more than one value for each sample (each data point), each value being stored in one index of the Macro Variable. As such, Macro Vari-ables are recognized by their particular names (for example, Gold[xxxxx]). Macro Variables may refer to:m different realizations of a variable: this is the case for simulation applications;m indicators or quantiles calculated on a single variable: these Macro Variables are outputs

from Simulation Post-processing, Indicator Post or Pre-processing, or from Bundled Indica-tor Kriging.

l Macro Selections are 1 bit Float Variables that contain more than one 0/1 value for each sam-ple, each value being stored in one index of the Macro Selection. Macro Selections are also rec-ognized by their particular names (for example, Geology[xxxxx]). The main interest of Macro Selections is to replace multiple selections by only one Macro Selection with different indices. These indices may be associated to different occurrences of an input variable, for instance dif-ferent geological facies, different types of data, etc.

Check the General introduction to Isatis > Isatis File System section of the On-Line documenta-tion for complete information about these structures.

34

5.3 Setting up the Study EnvironmentAll the parameters specific to your current study may be modified in the Preferences / Study Envi-ronment window. It is divided into nine parts which you can scan through by clicking on the TABS located in the top part. Please refer to the On-Line documentation for a detailed explanation of each parameter (press F1). Pay special attention to local parameters such as printers or directory names, as well as to the Units each time a new study is created.(snap. 5.3-1)

The Preferences / Copy Environment panel allows you to apply to the current study the environment of an already existing study.

When creating a new study, you can also recover for your new study the Study Environment of an already existing study. To achieve this, you just need to indicate in the File / Data File Manager /

Handling Isatis 35

Study Create window which Study for Default Parameters you want to use. You will also inherit the color scales, the calculator transformation templates and different types of graphic pages.

36

5.4 Data Types you Import Into IsatisIsatis has its own file system. This means that you need to import your datasets into the file system to be able to access and use them within Isatis. Numerous import facilities exist in Isatis, and are stored in the File / Import menus. They give you the possibility to import general file formats:

m plain ASCII files, using headers for describing data organization (CSV or fixed formats), either with projected or original latitude/longitude coordinates,m Excel spreadsheets,m direct database queries with the ODBC import,m binary files,m Autocad DXF files, for 3D visualization of wireframe objects (3D surfaces or volumes).

You may also import third-party software formats corresponding to particular sectors (asterisks (*) indicate that the data exchange is directly performed within the third-party software):

m Mining:- Datamine drill-holes or composites, regular and irregular block models, polygons (Data-

mine is trademark of Mineral Industries Computing Limited, MICL)- Vulcan composites and block models (Vulcan is trademark of Maptek)- Boreholes with deviated survey data- Direct database link with GEMs (*) point work spaces, point areas, drill-holes and

block models (GEMs is trademark of Gemcom). The link is only accessible from GEMs.m Environment:

- ArcView binary & ASCII grids, shapefiles (ArcView is trademark from ESRI)m Oil & Gas:

- Geocap wells properties & seismic data (Geocap is trademark of Shell Int. E&P)- Geoshare surface sets Geoshare is trademark of Schlumberger)- Direct database link with Gocad (*) wells, points, surfaces, grids with stratigraphic

transformations (Gocad is trademark of Earth Decision Sciences)- RML / Heresim 3D wells, points, grids, proportions and RML (*) (RML & Heresim 3D

are trademarks of IFP & Ecole des Mines de Paris)- Irap grids (Irap is trademark of Roxar)- SEG-Y seismic cube- Z-Map Plus grids & faults (Z-Map Plus is trademark of Landmark Graphics Corp.)- PDS wells & grids (Petrobank Project Data Store is trademark of IBM E&P Solutions)- LAS vertical and deviated wells- Direct database link with Petrel (*): boreholes and grid models (Petrel is a trademark of

Schlumberger). The link is only accessible from Petrel (Contact for more information: [email protected]).

Handling Isatis 37

Depending on the import type, these facilities will import into Isatis different types of data struc-tures: points, lines, grids or polygons. To get detailed information about these import facilities, just press F1 in the corresponding import window.

38

5.5 Exporting Results From IsatisOnce your geostatistical work is performed, Isatis offers you the possibility to directly copy/paste your graphics in reports.

You may also export your final results using general file formats:m plain ASCII files, using headers for describing data organization (CSV or fixed formats),m binary files,Third-party software formats corresponding to particular sectors may also be exported (asterisks (*) indicate that the data exchange is directly performed within the third-party software):

m Mining:- Datamine regular & irregular block models, polygons (Datamine is trademark of MICL)- Direct databse link with GEMs (*): any XYZ dataset, including 3D grids (GEMs is

trademark of Gemcom). The link is only accessible from GEMs.- Vulcan block models (Vulcan is trademark of Maptek)- Whittle Four-D block models (Whittle Four-D is trademark of Whittle)

m Environment:- ArcView binary & ASCII grids (ArcView is trademark from ESRI)

m Oil & Gas:- Geocap simulations (Geocap is trademark of Shell Int. E&P)- Eclipse grids (Eclipse is trademark of Schlumberger)- Direct database link with Gocad (*) wells, grids with back stratigraphic transformations

(Gocad is trademark of Earth Decision Sciences). The link is only accessible from Gocad.- CMG grids (CMG is trademark of Computer Modelling Group Ltd.)- VIP grids (VIP stands for Landmarks reservoir simulation technology suite and is trade-

mark of Landmark Graphics Corp.)- RML / Heresim 3D wells, points, grids, proportion (RML & Heresim 3D are trademarks

of IFP & Ecole des Mines de Paris)- Irap grids (Irap is trademark of Roxar)- LAS vertical and deviated wells - SEG-Y seismic cube- Z-Map Plus grids (Z-Map Plus is trademark of Landmark Graphics Corp.)- Direct database link with Petrel (*) grid models (Petrel is a trademark of Schlum-

berger). The link is only accessible from Petrel. (Contact for more information: [email protected]).

To get detailed information about these export facilities, just press F1 in the corresponding import window.

Handling Isatis 39

5.6 Customizing the Interface MenusThe Preferences / Menus window allows you to easily customize the list of applications that are vis-ible in each Isatis menu:

l deselect the application that you do not currently use,

l press OK. The corresponding application will be hidden from the Isatis menus until you select it again.(snap. 5.6-1)

Tutorial: Familiarizing With Isatis Basics 41

6.Tutorial: Familiarizing With Isatis BasicsThis tutorial gets you acquainted with the basic concepts of Isatis, through several exercises performed on a simple topography dataset:

creating a New Study,

importing data in the Isatis File System,

checking and correcting data,

selecting samples of interest,

computing basic statistics,

performing a quick interpolation,

displaying the results,

reporting.

42

6.1 Creating a New StudyBefore creating your first study, Isatis shows Isatis-Init in place of the study name, in the title area of the Isatis Main Window.

Start the File Manager by selecting File / Data File Manager in the Isatis main window; the follow-ing window comes up:(snap. 6.1-1)

Please click on Study menu and select Create. From now on the following syntax will be used in the manual to describe this type of action: select Study / Create.

A Create Study window pops up from which you should enter Topography as a New Study Name. You may choose where you want to save your Isatis study on disk; the location should be entered in the New Study Location on Disk. If you do not bother about this location, you may ask Isatis to use a default location on disk. In this case, a directory called Isatis is created under My Documents in Windows OS (under $HOME in UNIX OS) and a new sub-directory is created to contain the new Isatis project, with your New Study Name.

(snap. 6.1-2)

Some projects may require the use of particular variables for the coordinates instead of the usual X, Y and Z. Unless this is your case, it is recommended to switch on the toggle Use the Isatis Scaling Coordinate System. Finally, you may choose for the new Study Environment the Environment of an already existing study, by choosing it among the available Isatis studies.


Click on Create to actually build the new study.

Select Preferences / Study Environment... in the Isatis Main Window to bring up the Study Envi-ronment window. Modify the following default parameters:

m unit for distance quantities: meter,m printing format for distance (length) quantities: decimal, 9 digits, 2 digits after the period,m units for labels on the graphical axes: meter for both vertical and horizontal axes,m format attached to new variables: decimal, 9 digits, 2 digits after the period.Set the parameters as illustrated:

(snap. 6.1-3)

Click on OK to validate these choices.

Note - Remember that to obtain more information about the parameters of any window, you can always hit F1 or Help on your keyboard while the mouse pointer stands above this window.

44

6.2 Importing Data Into the Isatis File SystemImporting data into the Isatis File System is the first task. Since the data file is provided in flat ASCII, proceed as follows.

Select File / Import / ASCII. Click on ASCII Data File to pop up a File Selector that will enable you to select the ASCII file name: topography.hd.

In a standard installation, this dataset should be stored under:

m $GTX_HOME/Datasets (on Unix workstations)m C:\Program Files\Geovariances\Isatis\Datasets (on Windows)

In this directory you will find the directory Topography which contains the file topography.hd. This ASCII file is already formatted to be directly imported with Isatis. In particular, it contains a header describing its contents.

Note - You can obtain detailed information about ASCII headers within the On-Line Help: just press F1 while the mouse pointer stands above the File/Import/ASCII window.

Select the option: header is contained in the ASCII Data File.

In the Isatis File section, select the option: Create a New File.

Click on NEW Points File to bring up the File and Variable Selector window.

Click on New Directory and enter Data as new directory name.

Click on New File and enter Samples as new file name.

(snap. 6.2-1)

Click on OK.

Tutorial: Familiarizing With Isatis Basics 45(snap. 6.2-2)

Your Import window should be as above and you just have to click on Import to load the data.

The slider in the Status Area proceeds while the status is Running and until the end of the import action; the status then comes back to Idle. Click on the Isatis Messages icon to see the information printed in the Isatis Messages Window:

ASCII FILE HEADER INTERPRETATION: # structure = free# x_unit = m# y_unit = m# field = 1 , type = alpha , name = well name# ffff = " " , unit = , bitlength = -1# f_type = Free , f_length = 9 , f_digits = 2# description = ""# field = 2 , type = xg , name = X Gravity Center# ffff = " " , unit = , bitlength = -1# f_type = Decimal , f_length = 8 , f_digits = 2# description = ""# field = 3 , type = yg , name = Y Gravity Center# ffff = " " , unit = , bitlength = -1# f_type = Decimal , f_length = 8 , f_digits = 2# description = ""# field = 4 , type = numeric , name = elevation# ffff = " " , unit = m , bitlength = 32# f_type = Decimal , f_length = 8 , f_digits = 2# description = ""#+++++++++++++++---------------+++++++++++++++--------------- Number of Header Samples (*) = 0 Number of Samples read = 52 Number of Samples written to disk = 52

Click on Close to close the Import ASCII File window.

46

6.3 Checking and Correcting Data

6.3.1 Browsing the Data Through the File ManagerSelect File / Data File Manager to pop up the File Manager window, then click on the + signs at the nodes of the tree in order to open the Data directory and then the Samples File:(snap. 6.3-1)

Click on Data in the tree and select Directory / Information either in the menu in the top of the window or using the graphical menu (right button of the mouse) in order to get information about this Directory.

The Messages window opens and contains the requested information:

(snap. 6.3-2)

Click on Samples in the tree and select File / Information to get information on the File itself, including statistics about the field extension:


*** File Information *** Directory Name : Data File Name : Samples Organization : Points - 2D Number of Samples : 52 Last Modification : Jan 23 2006 14:11:28 Size : 18 Kb Physical Path : \\Server-in\doc\case_studies_60\Topogrphy\GTX\DIRE.1\FILE.1 *** END of File Information ***Click on elevation, then press the key to obtain information on this variable: *** Variable Information *** Directory Name : Data File Name : Samples Variable Name : elevation Variable Type : Float (Length) Bit Length : 32 Unit : m Last Modification : Jan 23 2006 14:11:28 Size : 2 Kb Physical Path :\\Server-in\doc\case_studies_60\Topogrphy\GTX\DIRE.1\FILE.1\

VARI.5 Printing Format : Decimal, Length = 8, Digits = 2 Variable Description:Creation Date: Jan 23 2006 14:11:28 *** END of Variable Information ***

Click on elevation, then press the key to obtain basic statistics on this variable: *** Variable Statistics *** Directory Name : Data File Name : Samples Variable Name : elevation Variable Type : Float (Length) Bit Length : 32 Unit : m Last Modification : Jan 23 2006 14:11:28 Size : 2 Kb Physical Path :\\Server-in\doc\case_studies_60\Topogra-phy\GTX\DIRE.1\FILE.1\

VARI.5 Printing Format : Decimal, Length = 8, Digits = 2 Variable Description:Creation Date: Jan 23 2006 14:11:28 MINI= 690.00m Q.25= 785.00m Q.50= 830.00m ST.D/MEAN= 0.0742358 Q.75= 873.00m MAXI= 960.00m Defined Samples= 52 / 52 MEAN= 827.08m ST.D= 61.40m*** END of Variable Statistics ***

48

6.3.2 Printing the Contents of the Data FileYou can printout the values that have been stored in the file system to the Messages Window. To achieve this:

l Select File / Print to bring up the print window,

l Click on Data File to pop up the File and Variable Selector window and in this window, click on Data, then Samples in the tree (please refer to the online help for the file & variable selector

usage by pressing F1),

l The Variable 1 item is selected by default in the question list located at the bottom of the win-dow (if this part of the window is too small, you can increase it by dragging the small square on the upper right corner of this part upwards),

l Click successively on X Gravity Center, Y Gravity Center and elevation in the variable list to add them to the bottom question list.

The window should be:

(snap. 6.3-3)

Click on OK, then Run in order to dump the content of the file into the Messages window:PRINTOUT: ++++++++ Directory: Data +++++++++++++ File: Samples ++++++++ Selection: None +++++++++ Variable: X Gravity Center (m) +++++++++ Variable: Y Gravity Center (m) +++++++++ Variable: elevation (m)


Total number of samples = 52 30.00 610.00 870.00 140.00 620.00 793.00 240.00 610.00 755.00 360.00 620.00 690.00 .../... 140.00 10.00 890.00 210.00 70.00 880.00 230.00 30.00 870.00 310.00 0.00 880.00

410.00 80.00 960.00 540.00 40.00 890.00 600.00 10.00 860.00 570.00 300.00 830.00 360.00 600.00 705.00 +++++++++ END OF PRINTOUT: 52 samples

Click on Close to close the Print window.

You can print the contents of the Messages window, edit them, save them in a text file or clear them.

Click on Hide to close the Messages window.

6.3.3 Correcting Errors With the Variable EditorDuring the previous operation, you may have detected some erroneous values. They can be cor-rected directly in Isatis to avoid having to re-import the dataset.

To achieve this, open the File / Variable Editor. Click on Load File to specify the file and the vari-ables that should be corrected. It is sometimes useful to set an identifier as v1, for instance a sample name, to recognize the values that should be corrected. The samples are then displayed in the Vari-able Editor, by increasing Sample Number.

Once identified the value to be corrected, just click on the cell and enter the correct value. Once all your corrections have been performed, click on Save to take them into account permanently.

Note - Once identified the sample number of the value to be corrected (using for instance the previous printout), use the Go to Sample #... option to directly access the sample of interest.

6.4 Selecting Samples of InterestIsatis files may contain a particular type of variable that takes only two possible values (0 and 1) and that are called selections. According to the value of a selection variable, a sample may be either selected (1) or masked off (0).

Selections are used whenever it may be necessary to work with a subset of the data instead of the whole data set (without modifying the data file itself), for instance:

50

l when there are outliers in the data that you would like to ignore at some stages of the project,

l when an interpolation should only be performed on a limited area of a grid.

There are several ways to build selections on samples, all of them being described in the Dealing with Selections chapter of this Beginner's Guide. An illustration is provided hereafter for a selec-tion corresponding to an interval of elevation values. In this exercise only the samples with an ele-vation below 900 m are kept in the selection:

l select File / Selection / Intervals,l click on Data File to pop up the File and Variable Selector window,

l select Data and Samples from the tree, then select elevation as the Variable to be processed,

l click on New Variable and enter elevation =< 900m as New Variable Name,

(snap. 6.4-1)


l click on OK,

l set the first interval of values to: ] ,900] as illustrated:(snap. 6.4-2)

l click on RUN and check for the results in the Messages window: SELECTION/INTERVAL STATISTICS: ----------------------------- New Selection Name = elevation =< 900m Total Number of Samples = 52 Masked Samples = 5 Selected Samples = 47

l click on Close to dismiss the Interval Selection window.

52

6.5 Computing Quick StatisticsCompute some raw statistics on that data, without taking into account the 5 highest elevations in the field:

l select Statistics / Quick Statistics,

l click on Data File to pop-up the File Selector window,l select Data and Samples from the tree, then continue clicking in the tree on the selection eleva-tion =< 900m in order to activate this selection on the samples,

l choose elevation, X Gravity Center and Y Gravity Center as variables 1, 2 and 3,

l switch ON the Univariate Statistics and ask to calculate the 10% quantiles:

(snap. 6.5-1)

l click on Run and check that the statistics reported in the Messages window are:QUICK STATISTICS: ++++++++ Directory: Data +++++++++++++ File: Samples ++++++++ Selection: elevation =< 900 m +++++++++++ Weight: None +++++++++ Variable: elevation (m) +++++++++ Variable: X Gravity Center (m) +++++++++ Variable: Y Gravity Center (m) Total Number of Samples: 52


Statistics: ------------------------------------------------------------------- ...| VARIABLE | Count | Minimum | Maximum | Mean | ...------------------------------------------------------------------- ...| elevation | 47| 690.00| 890.00| 816.49| ...------------------------------------------------------------------- ...| X Gravity Center | 47| 20.00| 630.00| 334.89| ...------------------------------------------------------------------- ...| Y Gravity Center | 47| 0.00| 620.00| 346.81| ...------------------------------------------------------------------- ...

Statistics (continued): --------------------------------------------------------------------------- | VARIABLE | Variat.C | Skewness | Kurtosis | Geometri | Harmonic | --------------------------------------------------------------------------- | elevation | 0.07| -0.53| 2.31| 814.62| 812.71| --------------------------------------------------------------------------- | X Gravity Center | 0.55| 0.06| 1.84| 262.93| 161.85| --------------------------------------------------------------------------- | Y Gravity Center | 0.55| -0.28| 1.93| N/A| N/A| ---------------------------------------------------------------------------Quantiles Calculation: ---------------------------------------------------------------------------... | VARIABLE | Q10 | Q20 | Q30 | Q40 | Q50 | ... ---------------------------------------------------------------------------... | elevation | 730.00| 765.00| 793.00| 805.00| 820.00| ... ---------------------------------------------------------------------------... | X Gravity Center | 90.00| 160.00| 210.00| 240.00| 340.00| ... ---------------------------------------------------------------------------... | Y Gravity Center | 40.00| 170.00| 230.00| 320.00| 380.00| ... ---------------------------------------------------------------------------...

l switch ON the Multivariate Statistics and change the Printing Format to Decimal(10,5); run the statistics again in order to obtain the correlation coefficients between the variables:Correlation Matrix: ----------------------------------------------------- | VARIABLE | elevatio | X Gravit | Y Gravit | ----------------------------------------------------- | elevation | 1.00000| -0.02791| -0.77227| | X Gravity Center | -0.02791| 1.00000| -0.03005| | Y Gravity Center | -0.77227| -0.03005| 1.00000| -----------------------------------------------------

l close the Quick Statistics window.

54

6.6 Performing a Quick InterpolationThis section describes how to perform a quick interpolation at the nodes of a regular grid.

6.6.1 Creating a Grid FileFirstly, you must define the target file for the interpolation. This target is usually a Grid file. Once created, the grid will be able to contain several variables per grid node.This 2D regular grid covers the field with a mesh 10m x 10m:m open the File / Create Grid File window,m build a new file called Grid under the Data Directory by clicking on New Grid File,m select 2D Grid File with the option button,m use Display File (optional) in order to select the initial data file: Data / Samples,m switch ON the Graphic Check toggle, so that a graphic window containing a basemap of the

samples comes up, and the Block mode of representation,m click on the Calculated from Samples button; this sets the X an Y Format to Decimal(8,2)

and the Unit to meters (accordingly to the contents of the Samples file topography.hd), and the mesh to 10 m in meters X and Y,

m just increase the number of grid nodes along X and Y to 65 x 65, and check for the area cov-ered by the grid on the basemap,

m click on Run to actually create the grid file and on Close to dismiss the window.

Tutorial: Familiarizing With Isatis Basics 55(snap. 6.6-1)

6.6.2 Interpolation by Inverse DistancesWith a classical interpolation method (inverse squared distances), you can quickly produce an ele-vation map.

In the Interpolate / Interpolation / Quick interpolation window, define in the Input File Selector the input data used in the estimation:

m Directory: Datam File: Samplesm Selection: elevation =< 900 mm Data Variable: elevation

Use the Output File Selector to define where the interpolation will be performed:m Directory: Datam File: Grid

56

m data variable: elevation estimated by I.D.

A search neighborhood has to be defined in order to select which data may be used for the estima-tion of a grid node. In this exercise a basic neighborhood is used: the Unique Neighborhood, which selects all the data for the estimation of any grid node.

l Click on Neighborhood to build a new set called unique (New Set Name string, Add button).

l Click on Edit; a Neighborhood Definition window comes up. It is meant to define all the param-eters of the search neighborhood, which are described in details later in the manual. Set the

Neighborhood Type to Unique.

(snap. 6.6-2)

l Click on OK to save the neighborhood in a parameter file and to close this panel.

Select Inverse Distances from the Interpolation Method and set the final parameters as shown:

(snap. 6.6-3)

Click on Run to perform the interpolation, and make sure in the Messages window that all 4225 grid nodes have been successfully estimated. Dismiss the Quick Interpolation window.


6.7 Displaying Graphical ResultsIsatis offers advanced facilities to produce sophisticated graphics. These facilities are contained in the Display menu of the Isatis main window.

The idea of an Isatis Display is to define the contents of the graphic and then to display it; for instance, you are going to create in this section a raster map of the elevation with the data samples overlaid. Once you have performed a Display, you can save:m the templates of your graphic, e.g. all its contents, to allow you to easily reproduce the graphic later;

m the graphic window itself.

Perform the following steps to create the graphic:

l Open the Display / New Page window. A menu pops up, as well as an empty graphic page that will fill contain your representations. Giving a name to this page is recommended if you wish to reproduce it later.

l Select in the Contents each representation you want to display in the Page Display by clicking on its name and copying in the Items list with the right arrow (you can also directly double-click on the name). Start with the Basemap, a window pops up to let you define the parameters for this item: Item contents for: Basemap.m File Definition: in the Data / Samples file, select elevation as the Proportional Variable.

Note - You can display at the same time a variable using proportional symbols (Proportional Variable), a second variable using a color scale (Color Variable) and an alphanumeric variable (Literal Variable).

m Data Related Parameters: by default, the lower and upper bounds of the variable to be dis-played are automatically adjusted to its minimum and maximum values; you can modify these values by switching off the Automatic button.

m Click on Display. The elevation basemap is displayed in the main Display page with pro-portional black crosses. All the symbol parameters may be changed in this window.

m Click on OK when you are satisfied with the parameters.

Note - Isatis defaults for general graphic environment parameters may be modified in the Preferences / Study Environment window, in the Graphics tab.

l Double-click on Raster to add a second item to the Display:m File Definition: in the Data / Grid file, select elevation estimated by I.D.m Legend Title: give a name to the legend that will be displayed: Elevation.m Use a default color scale, for instance Rainbow Reversed[READONLY][AUTO].m Click on Display and OK.

58

l The raster map is now displayed, but it overwrites the previous elevation proportional basemap. You can modify the order of your graphic contents using the Move Back and Move Front but-tons. Move the Raster item to the top of the Item list.(snap. 6.7-1)


l The Raster item being still selected, click on Legend then Display. You should obtain the fol-lowing graphic:(fig. 6.7-1)

l You can then Close the Contents window.

l The graphic page is entitled * Unnamed page [1] [Not saved]. The * indicates that your graphic has been modified since the last save.

l If you try to delete the graphic window (Management / Delete Window), a confirmation message pops up to ask you to confirm that you do not want to save your Graphic parameters.

l Just Cancel and enter a name in the Application / Store Page menu of the graphic window to save these parameters, for instance: elevation quick display.

l Note that this graphic is now directly available in the main Display menu and may easily be reproduced.

Note - You will find detailed information about how to edit graphics, create and edit your own color scales and other graphic capabilities in the Displaying & Editing Graphics chapter of this Beginner's Guide.

60

6.8 Reporting & Exporting ResultsUnder Windows, Isatis graphics may be directly inserted in usual Microsoft Office tools (Word, Powerpoint) using the Copy / Paste facility.

You may also store your graphics in Metafiles directories: just click on Management / Save in the graphic window. The File / Metafiles manager will then allow you to recover these graphics, orga-nize or combine them, etc. Read the Displaying & Editing Graphics chapter of this Beginner's

Guide for further information.

Obviously, you may also need to export numerical results towards third-party software. Several general and specific export formats are available in Isatis in the File / Exports follow-up menu. Check the corresponding On-Line Help for detailed information about their parameters.


6.9 Backing Up your Project & Exiting from IsatisTo exit from Isatis, select File / Exit and click on Confirm.

It is worth to know that every time you close a panel in Isatis, all the parameters involved in the corresponding application are saved and restored the next time you open the panel.

Exiting from Isatis does not delete these savings. Consequently, you will be able to recover your entire study and parameters the next time you start Isatis.Once your project is finished, it is worth backing it up to save disk space. This is feasible through the File / Data File Manager...: just click on Study / Save. Once this is done, you may delete your current study, as you will have the possibility to restore your backup later whenever you need it.

Note - Press F1 in the File / Data File Manager for further information about Study Save, Copy and Restore.

63

Getting Started with Geostatistics

Geostatistics in Short 65

7.Geostatistics in Short

This chapter gives you the main steps of a standard geostatistical anal-ysis: characterizing the spatial structure of the variable of interest,

modelling it and the applying kriging and simulations techniques. Fur-ther reading references are provided.

66

7.1 IntroductionGeostatistics has been defined by Georges Matheron as the application of probabilistic methods to regionalized variables. A regionalized variable designates any function displayed in a real space. At the difference of conventional statistics, whatever the complexity and the irregularity of the real phenomenon, geostatistics search to exhibit a structure of spatial correlation. This accounts for the intuitive idea that points close in the space should be likely close in values.What makes geostatistics powerful is its capability to characterize this spatial structure by means of a consistent probabilistic model. Therefore the predictions made using the geostatistical methods are tailored to the intrinsic structure of the variable and not only to the samples numbers and sam-pling patterns. This spatial structure is characterized by the variogram.

Because of its probabilistic framework, the geostatistical approach is claiming that the descriptions of the reality are subject to uncertainty, which can be quantified and provide efficient decision tools for practitioners and managers.

Because of the large variety of domains and the related specific problems, many methods are now proposed in literature and software. Basically two groups of methods are available:

m for mapping or estimating, the variogram is used to interpolate between the data points, this is the kriging.

m for characterizing the uncertainty on estimates (oil volumes, grade above cut-off, risk of pollution), the same variogram can be used in a different way for making simulations of the unknown reality.

These methods are presented in this chapter and then illustrated in the following chapter.


7.2 Characterizing & Modeling a Spatial StructureA classical geostatistical workflow usually begins with a detailed exploratory data analysis (base-map, histogram). The last step of this analysis is the experimental calculation of the spatial structure (experimental variogram). Then, a mathematical function is fitted to this experimental quantity: this function is called the variogram model.

All the further geostatistical calculations (kriging or simulation) will only use this model to charac-

terize the variables under study.

In the intrinsic case where the variable does not show a systematic trend, the common experimen-tal tool is the variogram which can be calculated from the data using a variety of parameters (direc-tions, tolerances, etc.). In the case of several variables, you must also characterize there spatial behavior by taking them two by two this leads to the calculation of the simple and the cross vario-grams.

Note - The variogram is sometimes also called semi-variogram in the literature. However, the term variogram tends to become established for its simplicity and can be supported by theoretical arguments. Only this term is used in Isatis and its manuals.

7.2.1 Experimental variogramThe experimental variogram describes the spatial correlation of a variable as a function of the dis-tance. It is calculated by comparing the values of the variables at two different locations by means of the quantity:

(eq. 7.2-1)

It is depending on the distance between the data locations (x) and (y). Making these locations vary among the available data leads to the variogram cloud (see figure hereafter).

Each symbol represents, for a given pair of data, the quantity mentioned above (vertical axis) as a function of the distance between two data points (horizontal axis). There are as many points in the variogram cloud as pairs of data considered in the calculation; one pair of data is represented in blue in the graphics below:

12--- Z x Z y 2

68(fig. 7.2-1)

(fig. 7.2-2)

As the main information is the behavior of this variability function at a short distance, it is usually recommended to limit the maximum distance for considering the pairs.

The next step consists in summarizing the information carried by this variogram cloud in one or several experimental variograms. This is done by defining classes along the horizontal (or distance) axis. Each class is centered on a multiple of a value called the lag. The (half-)width of each class is


called the tolerance on distance. When equal to one half of the lag value, all the classes are contigu-ous which means that each pair belongs to one class exactly.

Note - The first class, centred on the zero-distance, is only one-sided as the distance axis is always positive; hence its width is only half of the other classes, which explains why the contents of this class are usually much smaller than the one of the other classes.

When the data is located on the nodes of a regular grid, decreasing the tolerance on distance to a very small value may be interesting. Indeed, in this case, if the lag is equal to the grid mesh, the

experimental variogram only contains pairs calculated from points located on the same row or col-umn.

In some cases, it can be useful to check if the variable behaves similarly in all the directions of the space. For that purpose, the variogram cloud is split into its directional components. A directional variogram is characterized by an orientation and an angle. If you consider the line drawn through the first point of the pair, parallel to the orientation, this line constitutes the axis of a cone with an opening equal to the angle: if the second point lies within the cone (or its symmetrical), the pair is retained; otherwise the pair is discarded.

(fig. 7.2-3)

A drawback of this cone shape is that the width of the cone increases with the distance between points, and this misses the point of accurately describing the behavior of a field in a specific direc-tion. Hence the use of the slicing criterion. The orientation axis also serves as the center axis of a cylinder with a rectangular section characterized by its two extensions called width and height.

The slicing height is only used in 3D. In fact, in 3D, the first task consists in defining the reference plane (characterized by its dip and azimuth): the slicing height is the thickness of the tolerance in the direction orthogonal to this plane. Otherwise the remaining criteria are specified in this refer-ence plane, for a 2D case.

70

Note - Further illustrations about these parameters are available in the On-Line Help.

Two particular cases of definition for experimental variograms can be specified:

l when data is collected along lines, it may be convenient to calculate the variogram along the line, regardless of the direction of the line: two points of a pair must belong to the same line.

l when data is collected on a regular grid, it usually makes sense to consider the experimental var-iograms calculated along the main axis (and possibly main diagonals) of the grid: this is similar to setting the lag equal to the grid mesh and both the tolerance on the distances and cone angle

to zero. The calculations are speeded up since the system is aware of the specific pattern of the information.

7.2.2 Variogram modelThe following step in a standard geostatistical study is to fit a model to the set of experimental var-iograms calculated as described previously.

In any geostatistical study, you have to define the spatial characteristics of the variable(s) of inter-est. These characteristics are captured in a single set of parameters called the Model. It must describe the phenomenon whatever the dimension of the space and whatever the number of vari-ables that will be studied simultaneously. It consists of a linear combination of basic functions. The set of basic functions available has been carefully selected in order to ensure the Model to be authorized. When using a non-authorized model, there is no guarantee that the variance quantity remains non-negative and, for example, the estimation procedure (kriging) which is precisely based on a minimum-variance property could produce wrong results.

A first, essential remark is that the model is compulsory: in fact, one might think of bypassing this step and using directly the experimental curves through the kriging procedure. This hypothesis does not work properly as kriging requires the numerical values of the variogram not only for the dis-tances between the data points but also between data and target grid nodes. These distances are obviously not accessible from the experimental variograms.

All the experimental variograms must then be fitted using a linear combination of basic functions (called variogram models) which constitutes the Model. Obviously each basic function can have different behaviors in the different directions of the space to reproduce the anisotropy experimented on the data. In the case of several variables, all the simple and cross variograms that can be estab-lished must also be fitted using linear combinations of the same basic functions: there are some additional constraints on the coefficients of these combinations in order to ensure that the final model is authorized. The fitting procedure is mainly performed graphically in a trial-and-error pro-cedure which allows the user to decide the fitting quality.

When there is no drift (the expected value of the increment Z(x)-Z(y) is 0), the variogram exists and can be fitted as explained above (intrinsic case). This case also includes the strict stationary one, where the only valid tool consists in covariances. But one can demonstrate that the covariances constitute a restricted family of variograms (the bounded ones) and no difference will be made between these two cases as far as the Structure Identification is concerned.


In Isatis, the Model term is used for both the intrinsic and the non-stationary case (presence of drift). This Model therefore always contains two parts:

l The covariance part (where covariance is used in the broad sense) which will give the parame-ters of the linear combination of basic functions (defined either in terms of covariance, vario-gram or generalized covariance).

l The drift part where the hypotheses on the trend or the drift are stated.

A variogram consists of an authorized function describing the behavior of the variable (its regular-

ity) as a function of the distance. It is constituted of a linear combination of several nested basic structures, each one being an authorized function. Nesting means that the contribution of each basic structure is arithmetically added for any distance value, as illustrated in the next figure.

(fig. 7.2-4)

Each basic structure is a function of the distance. It is usually expressed using:

l A coefficient which gives the order of magnitude of the variability along the vertical axis (homogenous to the variance). In the case of bounded functions (covariances), this value is sim-ply the level of the plateau reached and is called the sill. The same concept has been kept even

0 50 100 150 200 Distance

0

1000

2000

3000

4000

Vari

ogra

m

0 50 100 150 200 Distance

0

1000

2000

3000

4000

0 50 100 150 200 Distance

0

1000

2000

3000

4000

Vari

ogra

m

1 h 2 h

1 h 2 h +

72

for the non-bounded functions and is still called sill for convenience. The interest of this value is that it always comes as a multiplicative coefficient and therefore can be calculated using auto-matic procedures, as explained further.

l A parameter which affects the horizontal axis by normalizing the distances: hence the name of scale factor. This term avoids having to normalize the space where the variable is defined beforehand (for example when data are given in microns whereas the field extends on several kilometers).When the function is bounded, it reaches a constant level (sill) or even changes its expression after a given distance: this distance value is the range (or correlation distance in statistical lan-guage) and is equal to the scale factor. For the bounded functions where the sill is reached asymptotically, the scale factor corresponds to the distance where the function reaches 95% of the sill (also called practical range). For functions where the sill is reached asymptotically in a sinusoidal way (hole-effect variogram), the scale factor is the distance from which the variation of the function does not exceed 5% around the sill value.

Finally, the scale factor is used in case of anisotropy. For bounded functions, it is easy to say that the variable is anisotropic if the range varies with the direction. This concept is generalized to any basic function using the scale factor which depends on the direction, in the calculation of the distance.

The following figure illustrates a classical basic structure: the spherical model, for a range a vary-ing from 1 to 10. Its mathematical expression for a sill equal to C is given by

(eq. 7.2-2) C32--- h

a---

12--- h

a---

3h a

C h a

=


0.75

1.00 (fig. 7.2-5)

0 1 2 3 4 5 6 7 8 9 0.00

0.25

0.50

74

7.3 Ordinary KrigingKriging is the standard geostatistical estimation technique. All the kriging variants are detailed in the Isatis Technical Reference about Linear Estimation, available in the On-Line Help system. Only the principle of the ordinary kriging is presented hereafter.

Let Z be a random variable. The kriging estimate, denoted Z*, is defined as a linear combination of the neighboring information , introducing the corresponding weights

(eq. 7.3-1)

For better legibility, the summation symbol will be omitted whenever it is possible using the Ein-stein notation. The estimation error, i.e. the difference between the estimation and the true value, is Z*-Z0.The kriging estimator at the target (denoted 0) is expected to:

l be unbiased:

(eq. 7.3-2)

Assuming that the random variable Z has a constant unknown mean value: E[Z]=m, equation (eq. 7.3-2) can be expanded:

(eq. 7.3-3)

which leads to:

(eq. 7.3-4)

This is usually called the Universality Condition. Actually, in the Intrinsic case (where no drift should be defined by definition), the drift part is not empty but reduced to a constant (referred to by a monomial of degree 0: 1). The Universality Condition is applied in order to filter out this constant, leading to constrain the sum of weights to sum up to 1.

l have minimum variance (optimal):

(eq. 7.3-5)

minimum

Minimizing equation (eq. 7.3-5) leads to the resolution of a linear system with constraints, known as the kriging system, that let appear the variogram values between the data:

Z

Z Z=

E Z Z0 E Z Z0 0= =

E Z Z0 m 1 0 m= =

1=

Var Z Z0 Var Z Z0 =


(eq. 7.3-6)

+ 0 =

1=2 00 0 +=

Solving this system leads to the kriging weights . By replacing them in the equation (1), it leads

for the current target 0 to the kriging estimate Z* and to the kriging variance , which gives an indication about the precision of the kriging estimate.

2

76

7.4 SimulationsA simulation of a random function is a realization, on a given domain, of the model describing this random function. In particular, this realization reproduces the statistical and geostatistical variabil-ity characteristics of the random function, for example its histogram and

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