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| IntroductionThis documentation goes through the working steps and menus in Geocap for depth conversion of time surfaces applying a time-velocity cube. There are other methods for depth conversion than those described here, but this method is favorable when stacking velocities and well data are present. This depth conversion documentation deals with quality control and analysis of input data. Then gridding into a time-velocity cube and finally performing depth conversion of time grids in a Layer Model into depth grids. The velocity cube reflects the information in the velocity data in an organized way. Working with velocity cubes will make depth conversion of time data to depth data more easy. |
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Steps in depth conversion
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| title | Steps in depth conversion of time data using time-velocity cube |
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- Reading stacking velocities into a folder as: x y time velocities
- Inspecting the velocity data
- Gridding into a velocity cube
- Displaying the velocity cube
- Checkshot wells can be used to trim the velocity cube through sophisticated updating techniques
- The velocity cube is then used for depth conversion of time grids into depth grids
- Calculation of cubes for RMS and Interval velocities using the generated velocity cube. (Option)
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The folders used to save data in this project are of type Generic and renamed to indicated their contents. The various datasets will also be set to their proper schema type so that only relevant command objects are shown.
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| title | Reading stacking velocities into a project |
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- Create a Generic folder, give it a proper name
- Right click on the folder and select *Import->Stacking Velocities.
- Browse in all stacking velocity datasets
- The cell structure is kept by specifying 'Value change' and set up 'cell separator' for the actual column
- The schema type is set to 'Stacking velocities' to get the correct commands visible on the dataset
- In this case the time values are in the z coordinates and the velocity values are scalar values
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Geocap project for stacking velocity data and velocity cubes
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| title | Fast and convenient method for depth converting all time grids in a folder using a velocity cube |
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- Set schema of the folder with the time grids to Layer model
- Copy the entire time grid folder to a new folder
- Rename the copied folder to Depth grids. It is still time grids, but will soon be converted to depth grids
- On the folder with depth grids, activate the commands *Layer utility ->Depth > Depth conversion of time grids grids in folder using velocity cube
- Browse in the velocity cube and hit Execute
- As a result all grids in the folder that were time grids are now converted to depth grid
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The central command in depth conversion is the pro command which does the probing of the time grid into the velocity cube. The time grid must be converted to polydata in order have a scalar part: x y time scalar. After probing this dataset into the velocity cube, the scalars are assigned values from the cube at their positions and the whole dataset is now transferred into x y time velocity.
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A time-velocity cube can be smoothed and recalculated to other forms like an RMS (Root Mean Square) or an Interval Velocity cube or even a depth-velocity cube. Read more about these options in Creating RMS cube, Interval cube and Depth-Velocity cube