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CycloLog Version 2012 Tutorial Manual – Part 3

Version July 2012 ENRES International

Version 2012

Tutorial Manual

Part 3 Generating and displaying log transform

INPEFA curves

Includes following topics:

1. Introduction to PEFA and INPEFA 2. Making PEFA and INPEFA curves 3. Displaying INPEFA 4. Using Dynamic-INPEFA 5. Batch generation of INPEFA curves

Copyright The CycloLog® Software and all accompanying documents are patented and copyrighted with all rights reserved by ENRES Energy Resources International B.V. The Software and documentation may not be given or sold except by ENRES Energy Resources International B.V. and its designated suppliers. Unauthorised copying, duplicating, selling or otherwise distributing the Software or documentation is a violation of the Copyright Law. CycloLog Patents Nr. 1015928 Netherlands, Nr. 1-182466 Europe CycloLog is a registered trademark of ENRES Energy Resources International BV INPEFA is a registered trademark of ENRES Energy Resources International BV ENRES is a registered trademark of ENRES Energy Resources International BV



Introducing log transform curves

ENRES workflow in well analysis and well correlations is unique in its approach. It consists of a data-driven analysis of well data, followed by a model-driven interpretation using the state-of-the-art stratigraphic conceptual models. Data-driven analysis of wireline log data in CycloLog is a mathematical calculation using spectral analysis (Maximum Entropy Spectral Analysis). The results are two types of log transform curves – the PEFA and INPEFA curves which are unique to CycloLog. The INPEFA log transform is commonly used in well zonations and correlations.

INPEFA is used to define real (bounding) surfaces and trends. This section of the CycloLog Tutorial describes how to use

CycloLog to make PEFA, INPEFA, and Dynamic-INPEFA curves. Model-driven interpretation of INPEFA is described elsewhere

(see A Guide to the Stratigraphic Interpretation of INPEFA).

PEFA = Prediction Error Filter Analysis, referring to the mathematical method used. INPEFA = Integrated PEFA.



Some words on the science behind

Log transform curves describe changes in the spectral (waveform) properties of a log. A log, like any other complex waveform, has properties of

amplitude, wavelength, and phase. These properties change from bottom to top of the log; some

changes are bigger than others. CycloLog’s calculations use spectral analytic methods to detect

such changes.

CycloLog generates two related log transform curves, PEFA and INPEFA.

PEFA shows the relative amount of change between one data-point and the next, based on the information in a window of analysis. (The default window-length is 10m/30feet.)

INPEFA is the integral of PEFA; it is a cumulative plot of the changes found in the PEFA curve.



Making PEFA and INPEFA curves

We first show the classic way of making PEFA and INPEFA, to illustrate the principles. Note, however that (a) PEFA is rarely used, and (b) we recommend the Dynamic-INPEFA function for routine use (see below).

NOTE: Log transform INPEFA curves are most often made from the GR log.

Right-click over the GR log in the Workspace and select Duplicate. Make another duplicate.

Open the GR and the two duplicated GR logs.

The picture shows a GR log with two duplicates.

Right-click over one of the duplicates and select Processing → Spectral attributes → PEFA. Keep the default values. CycloLog calculates and displays the PEFA transform of the log.

Right-click over the other duplicate and select Processing → Spectral attributes → INPEFA. Keep the default values. CycloLog calculates and displays the INPEFA transform of the log.

If you plan to keep the transformed logs, rename them (in the Workspace).



The following picture shows the results of these actions; vertical scale is 1:1,000.

Note: you can undo the PEFA and INPEFA processing by clicking on Edit → Undo on the menu bar or pressing the Undo button on the Standard toolbar.

IF YOU WANT TO MAKE INPEFA ONLY – YOU MAY USE THE DYNAMIC INPEFA OPTION (SEE PAGE 10)



Displaying INPEFA

Unlike standard log curves, INPEFA curves are characterised by short-term and long-term trends. These are best seen if INPEFA is displayed in a broad track; their appearance may also be improved if the vertical scale is reduced. In the following picture, the vertical scale has been reduced to 1:2,500; INPEFA is shown adjacent to mirror and colour-classified GR

displays; The INPEFA pane has been widened to show its features better.

Note the validation of the INPEFA with the GR log and colour-classified GR display: the more shaley intervals with positive (up-to-the-right) INPEFA

trends; the more sandy intervals with negative (up-to-the-left) INPEFA

trends.

In the following pages we explain the effect of using different filters and parameters on the INPEFA curve.



INPEFA: changing the parameters

A frequently asked question is: What difference does window-length make to INPEFA? Make another duplicate of the GR curve. Right-click over the curve, then select Processing → Spectral

attributes → INPEFA.

In the dialogue box, Filter size specifies the window-length in

depth units (feet or metres). The default value is 10 metres, or 30 feet.

Change Filter size to a larger number, and click OK.



The picture below shows the result of using filter lengths of 10m (the default), 50m, and 100m. Note the following: The form of the INPEFA curve is very little different, but: The portion of the data omitted from the calculation increases

with the window-length.

We therefore recommend using the default window-length at all times.



The default depth interval (shown in the dialogue box above) is the full depth interval of the data. This can be changed:

To calculate INPEFA for only part of the total interval: Right-click over the (duplicated) log pane, and select Processing →

Spectral attributes → INPEFA. Change the Start depth and End depth to the required values. Click OK.

The picture below shows INPEFA calculated for the interval 3600-3800m.



Using Dynamic-INPEFA (D-INPEFA)

Interpretation of INPEFA curves usually requires experimenting with the depth interval over which INPEFA is calculated.

This is most easily done with the Dynamic-INPEFA function.

To invoke Dynamic-INPEFA: Select from the menu bar Calculations → Dynamic INPEFA Or use the keyboard shortcut CTRL + D Or right-click on the log in the workspace and select Create

Dynamic INPEFA Log

In the Calculate Dynamic INPEFA dialogue box: [If there is more than one well in the project, select the required

well.] Select the GR log (this will be the default if it is the first log in the

Workspace list);



Specify the interval (note that this can easily be changed later); If more than one D-INPEFA curve is required, check the box and

specify the number. EITHER you create an x number of INPEFA duplicates on the full

interval range; OR you subdivide the INPEFA curve into a specified number of

curves. The curves will be equally subdivided within the given interval range. Check the box Create a total log.

The colour and name of the INPEFA curves are automatically assigned but they can be edited in the dialogue box. CycloLog uses a default colour set and name for the different INPEFA curves. To change the default colour set go to the menu bar: Tools → Colour Set.

Click OK. The INPEFA curves are saved to the workspace.

The following picture shows an INPEFA curve calculated for the entire dataset, and two D-INPEFAs calculated for short sub-intervals of the data.



To change the interval over which a D-INPEFA curve is calculated: Right-click over the curve; Select Change Interval;

Horizontal bands appear at the top and base of the current interval; The cursor changes to a hand. Click one of the horizontal bands and drag it up or down; The INPEFA is re-calculated in real time.

The next picture shows the red D-INPEFA curve in the process of being modified:



Overlaying D-INPEFA curves

If creating several D-INPEFAs for non-overlapping or partially overlapping intervals of the same well, it can be useful (and saves space) to overlay them in a single pane: Adjust the intervals of the D-INPEFAs individually; Go to View menu → Log Overlay and select the D-INPEFAs from

the list of available logs. Note that the depth intervals of the individual D-INPEFAs cannot

be changed in the overlay display (compare the use of Composite Well Charts in Part 4).

In the following picture, three D-INPEFA curves for the same well have been adjusted to overlap slightly, and then overlaid in a single panel at the right.



Batch generation of Dynamic INPEFA curves In the CycloLog version 2012 an option to generate Dynamic INPEFA curves for more than one well has been implemented. This operation is especially useful and time-saving when dealing with many wells that require one or more INPEFA curves. To generate a batch of Dynamic INPEFA curves: On the main menu bar, go to Batch Operations; Select INPEFA, the Select logs to generate INPEFA dialogue box

opens; Drag the Pane name to the left hand position; the red arrows will

indicate its position;

Order the logs by clicking on the column header; Select the GR logs for INPEFA calculation by checking the boxes; Click on Do INPEFA…



Select the GR logs for INPEFA calculation by checking the boxes; Click Do INPEFA… The dialogue box Calculate Dynamic INPEFA opens;



Enter the interval range and window size (default=10); Check the box Generate multiple curves for more curves; Enter the number of curves to be generated; If you prefer to have the curves subdivided, then check Sub-

division logs from range, in this case also check the box Create a total log;

The log name and colour is automatically generated for each well and added to the workspace;

Note that you can edit the log name and colour. To change the default colour set go to Tools → Colour Set.

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