Interactive Petrophysics Basic User's Guide

Prepared for: Norwegian University of Science and Technology (NTNU) By: Dulce Cruz and Borja De Faria-Pereira Perez de Rada Date: July, 2012

Interactive Petrophysics Basic User’s Guide This guide is designed to introduce Interactive Petrophysics (IP) software to beginners, i.e. students taking the basic petrophysics course TPG 4175 taught at NTNU. IP is a PC-based software program used for well log property analysis. The guide is divided into chapters which cover the basics of working with IP from starting the IP program, navigating its interface, using the IP database organization, to covering a workflow of a basic petrophysical evaluation. This workflow will include data loading, data editing, data correcting, and calculation of volume of clay, porosity, and water saturation in order to compute reservoir summation in single well and multi-well environment.

Chapter 0, Data availability and Well parameters: Before starting to use the IP Software for performing a petrophysical evaluation, it is very important and recommended to first spend some time in looking at the data we have available and also at the parameters of the specific well. The parameters and data of any well are given in the well header. The well header is a section of the well record page that primarily contains information about the company that drilled the well, the country where it has been drilled, the field where the well is located with its coordinates; also contains technical information such as depth drilled, depth logged, bottom hole temperature (BHT), Rm, Rmf, Rmc, Rm temperature, Rmf temperature, Rmc temperature, depth, different logging runs, casing intervals, bit size, type of mud used, mud weight, mud salinity, etc. The data availability refers to the LAS binary files. LAS is the format that IP can open and inside them are the curves available, the depth of the run and sometimes depending on the data we can have some driller parameters. To open a LAS File and see its info right click on the file and go to → Open with, and select the text editing programs Textpad or WordPad. Once the file is open you will see at the beginning of the file description text the information available about the curves, their logged depth, their tools, etc; while the rest is just the numbers and symbols which complete the binary file and are the codes that IP reads. It is recommended to have those files as reference to review their information whenever needed. The following is an example of how a LAS looks like when opened with Textpad:

 

Chapter 1: Database Setup and Data Loading 1.1 Open IP and create a new database, create a new well and load LIS or LAS files: First of all we need to create a new Database or open one in case we have it already. Click File→ new database →browse and open where you want your data to be saved, usually the same folder where you have the data →OK. If we want to open data just click on File→ Open Database. 

When you have created your database next step is to create a new well.

Then you need to put a name to the well and select the units your data is. Usually we choose meters. Then click OK. Your new well should appear in the left column just below the name of the data base and in the bottom in red you can see that the well has successfully been created.

Notice that in the left of the well it appears a (-1). This means that the well is not saved, you also see the (-1) in the bottom. When you save your work you will be able to see (1). Next step is to Load the Data. Left click on Input/Output → Load Data and then just click on the type of data you want to load.

Once you load your data a new screen opens in the “(work area)”. There you can see the parameters your data has and the units it has. You can choose to load or not load then by click in the tick or check mark ✓.

Below that click Load and then close the window. If in that file we do not have all the data we need and we are missing something that is in another file we will click in New File and do the same. On the right we have the option: add to curve name. There you have the Pre-fix or the Extension options. This is really useful in case you want to compare two readings from two different runnings through the same depth interval. As an example we can have GR and then we put 1 as Extension. So we have GR and GR1.

Chapter 2, Managing Well Header Information The Well Header is the upper part of the well record page. It contains data about that well. Some Las and Lis files (the new ones) have the header on it. To create a Well Header click on Well → Manage Well Header info, or click in the Well Header sign in the toolbar. Then a new page will appear and some data might be already filled if the LAS or LIS file has it. Then just fill all the data. There are different windows such as General, Position, Default….

If we want to create an image to print or simply to have an image that can be opened in any computer, just click in the printer logo (left of the scale in the work area). Then a new screen will be opened with several options. In main plot you got the option to choose to send the plot to printer, make a PDF, an image (choose the format (con be tif, jpg,… and name the image)

To see the plot header on the image or Pdf just go to plot header and select full and add a title.

Chapter 3 Working with Log Plot and Program Default Plots The log plot window is launched in IP by: Click View → Log Plot, or Ctr+L or from the work bar click the Log Plot logo. You have two logos the one in red is for a vertical well and the one in green is for a horizontal well.

Then in the work area a window will appear. Click on File → Program Default Plots, there you have lot of options for the course we will use the 4 Tracks Blank.

Then a blank log page will appear. In the left we have the thinnest one with the depth. Then we need to plot each curve in a column. To do so we click in the Blanc space under the number of the column, a new page will appear, in this new page you can choose between

curves and shading. In the curves zone you can choose the items you want to display in that column. You set your scale, if it will be visible, if the scale is linear or logarithm, the color of the line, its style and width. Then just press Apply and OK. And the curve will appear. Be sure to have ✓in the lock space, like that once the well is saved the plot will appear when opening.

The shading tab can be used for example in the neutron-density plot for displaying the neutron-density or sand crossover that can imply the presence of clean (sand) zones, and moreover if this separation is very large it could be an indicative of gas presence.

Another example of using the shading option is in the caliper log, to detect the presence of a mudcake, which is a good indicator of permeability.  

Click Apply and OK to end the shading or curve editing. Once the curves are loaded in the tracks, more options regarding track editing can be found if we right click in the track and look for such as zoom in, create a new track, delete track, etc.

Chapter 4 Log Editing 4.1 Erase curve and edit the shape of the curve: Click on Edit→ Interactive Curve Edit, click on the curve you want. Name the result one with the same name, then select null the data and start edit. Say ok to overwrite curve names. In case you made a mistake you can go to undo edit. Then Finish edit and the zone you selected will be erased. If the null the data box does not have ✓ then we can edit the curve and just put the shape we want. As you can see in the example below. 4.2 Splice Log Curves: Splice two curves is like glue two curves together. This is used to splice two or more different runs into one curve. Click on Edit →Interactive Curve Splice. Then Name the result curve (it is recommended to use the word Splice in front of the curve for example: SpliceDT) and in the input curves add the ones you like to splice.

Then click OK, a new window will open with the Input curves in the left and the Result Curve in the right. Click finish Splice to finish and then you have the option to save.

4.3 Depth Shifting: Is this depth shifting? If the matching of the curves is not very accurate you need to edit as it is said in the chapter above. A good help to do so is put the curve near any other that has a similar behavior. In this case since it is sonic I put it near the Deep resistivity reading and change the scale until they are close enough to follow it.

←Before ; After→

Chapter 5 Environmental Corrections: 5.1 Create a temperature curve: The temperature curve is required for some logging tool corrections and it is created in IP by: Right click on Calculation→ Temperature Gradient. A new window will appear where you can select points of depth and put the temp you have. Remember to put the temperature in Celsius degrees. Then click Run.

Then in a new Track select the curve Temp and the temp gradient will appear.

5.1 Environmental Corrections It is important for bad borehole conditions to do the environmental corrections. To do so click on Calculations →Environmental Corrections→ then choose the company that did the logging (Schlumberger, Halliburton,…) Then a screen like this should appear. 

There you have all the corrections available and you just need to fill in with the good data (careful with units). Then you can run tab which means applying the corrections. You can check the results by plotting them in a new work area. Then just click on Load and the corrections will be applied to the logs and you are now able to plot them in the main work area.

Chapter 6 Clay Volume calculation: The calculation of the clay volume is very easy and fast with IP. Click on Interpretation→Clay Volume, Ctrl+Alt+C or the clay volume logo. There you have several ways of how to calculate the clay volume. You can use GR, Neutron, Resistivity, Sp and another where you can put another parameter such as thorium….

Also you can calculate the clay volume with double clay indicator. This means you use two curves to calculate the Vclay. Then click on run to get a new window and yes to the question: “Do you wish to initialize Clay parameter plot?”

Then a new window will open, in this window you have the curve or curves you used to calculate the Vclay and another column with the Vclay.

As you can see in the image above there are two arrows pointing at the GR maximum and minimum cutoff values. These arrows can be moved to select the maximum value for the GR and the minimum in different zones. By doing so, we can get a more accurate value of the Vclay in the different zones.

Chapter 7, Crossplots: The crossplot module is used to graphically represent relationships between data and to perform calculations on log curves. Data can be displayed simultaneously on the crossplots with two or three axes. Crossplots can be scaled with linear or logarithmic axes. There are some predefined overlays available to display on the crossplot.

To create a crossplot click on View → Crossplot. A new window will appear like the one bellow where you can choose what curve to load on the X Axis, the Y axis Z1 and Z1 axis, the scale and if you want logarithmic. It is recommended to put NPHI (neutron) in the X axis, RHOB in the Y axis and we can put optionally GR in the Z1 axis. In overlay lines you can choose between many options corrections from Schlumberger, Halliburton,… This info appear in the Well Header. You can select the interval depth, this means you can do a crossplot just in the zones where you are interested by clicking the option Interval Depths and selecting the Top and Bottom of the zone. Then click Ok.

A new window will appear like the one bellow where you have the crossplot with the 3 lines for  Sandstone, Limestone and Dolostone. We can also see that the GR appears in colours. 

 

Once the crossplot is done you have many options, if you click on file you can save the crossplot,  print it,…  If you click on edit you can return to the window where you put the parameters to change  the scale for example. If you go to function you can do a lot of things such as create areas, highlight  points (this can also be done clicking the highlight logo), pressure gradients, regression (Regression is  about fitting a curve to data),… You can also click the 3D box and you will be able to see the crossplot  in 3D. 

    

Chapter 8, Porosity and Water Saturation The calculation of porosity can also be done with IP. It can be done in two different ways:

8.1 Porosity and Water Saturation in the simple log: Porosity computed in the Simple Log Interpretation module is either from Density or Sonic log. And the water saturation is computed using the basic Archie formula. The simple module does not include hydrocarbon or bad-hole corrections, and no flushed zone Sxo calculations are made. To do this click on Interpretation → Basic Log Analysis. Then a new window will appear like the one you can see in the image bellow. You can choose the input curves and the output. You can go to parameters in the top of the window. There you can split in zones, set the good parameters for Vclay, the fluid density for the density calculation,…

Then first click on Run and after click Make Plot. A new window will appear like the one bellow. Where you have Porosity, Sw and some lithologies.

8.2 Porosity and Water Saturation Analysis module: The Porosity and Water Saturation Analysis module incorporates some commonly used porosity and saturation models. This module assumes that any neutron curve entered is in Limestone matrix units. If this is not the case then the curve should be converted to Limestone units using the appropriate environmental correction module. To do this click on Interpretation → Porosity and Water Saturation or Ctrl+Alt+P or click on the Porosity and Water Saturation logo.

Then a new window will appear. In the Input Curves you have to load the curves you have available and they have to be environmentally corrected. In the initial Porosity model you can choose between Neutron-Density, Density, Neutron-Sonic,.. Be sure to have the Temperature in Cº and bellow that you have 3 options that you can choose as if for example you have Oil Based Mud. Also you have to select which method you want to calculate Sw such as Archie, Poupon, Waxman Smits…. (for basic Course choose Archie). You can choose which output curves you want to display.

Then click OK > confirm by clicking Yes. A new window will appear like the one showed below.

Chapter 9, Creating Zones: We can split our well into different zones; this is useful for the zonation of lithology or permeable beds. We create a new track and then click on Input/Output→ Load Data→ Load Zone Tops. Then click on create new tops, a new window will appear. You can choose the name of the zone, its depth interval, and also set the color. Then click OK and the zone will be created. You can edit the zone by clicking on it in the window of zone sets and then click edit, there you can change the depth intervals, colors,…

Appendix? (extra chapters) Chapter 10: Interactive trend /square curve: The interactive trend square curve is used as a cutoff to calculate Vshale through GR for example. We select the max and minimum values of the curve for different sections of it. To make it we go to Edit→Interactive Trend/ Square Curve Edit. Then create a new curve and we Name the curve; name max for the maximum values curve, and min for the minimum. We start the trend and when it is done click Finish Trend.

We should get a curve like these:

Chapter 11: Add core images to the log: In some cases you might have core images in your data. Cores are the only way we have to see the information of the rock properties in the reservoir. To add them to your log click on Input/Output →Load Data→ Picture Curves. Then a new window will appear, you have to create a new curve and name it. On the graphics File name do click and then load then open the image you want, you have to give the depth interval of the image you upload.  

Then update plots. To open them you go to the main work window, create a new track, to do that right click→ New track. In that new track we do as in Chapter 2 but in the style column instead of a line put pictures. The scale goes from 0 to 1 and it represents width of the track.