Petrolog v10.2 Help Manual
Formation image logs are recorded at very high density (Fast Channel speeds of 0.1 in. 0.2 or 0.025 m depth increments) and should therefore not be loaded into a slow channel speed log data file recorded (say) at 6 inch depth interval.
Users must make sure that the maximum resolution used in the field tape (FMI = 0.1 in) is used when creating a new logdata file.
Additional tool informations are available at the end of this chapter.
Avoid mixing FMI arrays with slow channel arrays like CMR and DSI array logs with large arrays recorded every 6in instead of the 0.1 inch depth increment of borehole image tools.
STEP BY STEP PROCEDURE:
STEP 1: Copy your LIS or DLIS file on your hard disk into a field project and the specific well directory.
STEP 2: Start Petrolog and move the the new directory in the Project Explorer Window and right mouse click on the DLIS or LIS file as shown in figure 2.
Figure 1 shows in the Project Explorer window the well directory FMI with the DLIS file called FMI1 and the pop up window when the user right mouse click on the DLS file with options available. Selecting Import will start the following series of events:
A verification file will be created with the file extension .VER
A new wellheader file for this file will be created and all the well and run and remarks available in the field tape will be loaded.
The program will auto select the logs to download from the log default table: See Log Defaults and display the selection shown in figure 2.
STEP 3: Click import to start the process of importing the FMI data and obtain the log selection as shown in figure 2.
Figure 2 shows a typical SLB DLIS file with an FMI data set. Only one file is available in this DLIS but the data is stored in 4 different frames as follows:
Frame 1: Frame spacing = 6 in: The only essential logs required to process and display the FMI image in this frame spacing are: CS, DEVI, HAZI, P1AZ. however some of the other logs can be loaded for plotting and other log analysis purpose.
Frame 2: Frame spacing = 1 in: Time only has been selected but we will only use the fast time FTIM found in Frame 3.
Frame 3: Frame spacing =0.1 in: The 16 button arrays must be selected (see figure 3) here before loading the data.
Frame 4: Frame spacing = 1.5 in: Only C1 and C2 are needed from this group of logs since the the other logs are also available in Frame 3 and in more details.
Figure 3 shows the final fast channel selection including the 16 arrays of 12 buttons each. The EV (Emex voltage) has also been added and should be selected if the user wants tom compute the true conductivity since the button readings are measuring the button current only.
The old SHDT DIP buttons equivalent logs (DB1 to DB4, DB1A to DB4A) are also available and can be optionally loaded.
STEP 4: Edit the Logs to transfer in each frame making sure that the 16 sets of button arrays are added and add the following single logs
Required selection: FCA1 to FCD4 (16 set of arrays) + DEVI, HAZI, P1AZ, C1, C2
Optional logs (needed for Speed corrections, recomputing P1AZ and converting buttons readings to resistivity etc: ETIM, CS, CVEL, FCAX, FCAY, FCAZ and magnetometer logs FX, FY, FZ, EV
DPTR, DPAZ and QUAF are the Schlumberger computed dips often processed in the field from the DB1 to DB4A logs. These can be potted against the FMI computed dips as a reference and optionally.
Figure 4 shows the final selection with duplicate or unnecessary logs loaded. Note that in Frame 4, we have added the Magnetometer logs FX, FY and FZ which are only needed if the user plans to recompute the P1AZ from the magnetometer and Accelerometer data sets. In low deviated well the P1AZ calculated in the field is very food but for higher deviation above 25 Degreed, P1AZ should be recomputed as PD1N and compared to the field results before proceeding.
STEP 5: Turn Off the Interpolate slow channels (bottom left for Figure 4) if angle units are in RAD instead of Degrees.
The Interpolate Slow channel default = ON and will cause the loader to interpolate all the slow channel speed logs. Measurements made in Degrees will be interpolated correctly so that jumping from 360 to 1 Deg will be 0 and not 180 Deg.
If field measurement are not in Degrees but in RAD. The interpolate slow channel should be disabled here.
STEP 6: Change the Petrolog output filename if needed.
STEP 7: Click OK to create load the selected logs and arrays into the Petrolog logdata file.
STEP 8: The Project explorer window should now show all the new files created as shown in Figure 5
Figure 5 shows the new file created when loading the FMI_DSI DLIS tape in the Project explorer and including:
.logaudit.txt file: This is a text file that records which logs were loaded from what file at what time. This audit file will be updated as some processes are requested in the future.
.logheader file. This is an XML file that contains the long log names for the logdata file itself and many other information about the file itself.
.ver file: This is a text file that contains the verification listing of the DLIS tape. It can be viewed to check the statistics of all logs in the DLIS file.
.wellheader file: Contains the well, run and remarks as entered by the field engineers in the DLIS tape.
STEP 9: Double click on the .logdata file to open it in the working window and to list all logs available in the Log listing Explorer window as shown in Figure 5
STEP 10: Scroll the log list in the working window and check that log values are correct and that none are missing.
List some of the button log values and scroll down until the first good value is recorded. In the example of Figure 5 the first good log value starts below 1354 which is more that 50% down the file. There is more than 800m of FMI data in the casing with reading values from -1 to +1.
Some other files will have NAN or incredibly small or large log values in the casing since the electric currents can saturate the tool. Since the plot files will consider all the values loading in the logdata file it is therefore important to remove all non-formation related values by setting them to missing or by reducing the depth interval of the FMI logdata file itself as described in Step 11
STEP 11: Reduce the depth interval of the file using Continuous Log Management _ Modify log Data file to obtain figure 6
Figure 6 shows the original details of the logdata file. As per Figure 5 the Start depth should be changed to 1360 and the bottom depth to 1970 to remove the button values that are recorded with the tool closed or in the casing.
STEP 12: Add 4 DIPI, AZI, DIPS, DIPQ. See Imagelog Preprocessing
STEP 13: Close the working window in Figure 5 and double click on the .wellheader file. Edit and upgrade this file as some of the mud properties will be loaded from this data set when processing the Image later on. See Edit Well Header
STEP 14: In the Workflow Window, click on Graphics + Create Log Plot + Imagelog to get Figure 6 and select FMI Dynamic + Dips
Figure 7 shows the current set of default plots for various Imagelog displays. Since the primary objective of the FMI is to extract dips the dynamic image plus dips default should be used initially. Therefore select FMI DYNAMIC + DIPS to obtain figure 11
Figure 8 is the plot that will automatically be generated. Since this image if from an SLB field tape, only the pad and button depth shifts have been done in the field and although some of the formation dips appear very good there are many places where the flap appears off-depth. Accelerometer speed corrections should fix most of these problems.
To make changes and improve the image presentation. See Image Plots
The scale of the image is at 1/7.2 so that for normal screens there 72 values per inches which is the standard screen resolution of 72 DPI. This ensures the optimal vertical resolution to extract dips from the image.
Track 1 plots the following curves: GR, C1, C2, DEVI, HAZI and P1AZ as curves and also DEVI, HAZI, P1AZ as a tadpole every 2m.
Track 3 is ready to enter new dips from images.
Track 4 is the dynamic image with P1AZ to indicate the relative position of track 1.
STEP 15: If the P1AZ is erratic or unreliable. Recompute the Pad 1 North using the Accelerometer and magnetometer data. See Dip and Azimuth Computations
STEP 16: Make the necessary corrections such as: Speed corrections, dead button corrections, de-stripe the image and do the arm swing corrections. See Image Enhancement
Figure 12 is the same FMI image as figure 11 but after all corrections have been applied. This is an extreme case where, without speed corrections the image is practically useless.
STEP 17: Convert the button currents to conductivity and calibrate the conductivity against an OH shallow resistivity log. See Calibrate Pad Sensor Data
STEP 18: Extract dips from the image. See Imagelog Dip Extraction
STEP 19 (Optional) Extract Volumetrics. See Image Volumetrics Analysis
STEP 20: (Optional) Compute the Porosity distribution, permeability, anisotropy from image. See Image Porosity Analysis, Image Textural Analysis and Image Porosity Analysis
STEP 21: (Optional) Do a thin bed analysis from the image. See Image Porosity Analysis
STEP 22: Make your final presentation plot, add stereonets, walkout plots and text remarks annotations. See Image Plots
ADDDITIONAL TOOL INFORMATIONS:
Figure 13: FMI sensor geometry and the Schlumberger Tool Comparison chart.
Most FMI logs are delivered either using the LIS or DLIS format standards.
Figure 11 is a tool diagram of the SLB FMI tool
Figure 12 shows the position of the buttons on the pad and flap of the current FMI tool. This information is used to do the speed corrections and to do the pad and button depth shifts.