Posted by asefunc on Jul 26, 2015 in TracePAK | 1 comment
I need to have a 3D velocity volume for explanation of fluvial-deltaic processess.
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If you know your interval velocities, I can give you a simple workflow below in regards to creating a velocity volume through “Trace Calculations”
– Go to Tools>Calculators>Extended Math
– Create a dummy horizon for time=0
– You can simply do that by multiplying one of your existing horizon by “zero”
– Let’s call it “Horizon-t0” as an output horizon
Now you have a horizon at time=0 required for the later calculations.
– Go to Grids>Create Grid and grid all of your horizons, including the “Horizon-t0” with the same gridding parameters
Now, you have the “time” grids of your horizons.
– Go to Grids>Create Grid
– Select your “Horizon-t0” and re-gird it with a new output grid set to “TVD Seismic”
– Go to Tools>Depth Conversion Compute Isochore Map to create an isopach between Horizon-t0 and your first horizon down. Let’s call it “Horizon-1”.
– Give a name for the new isopach. This actually be the depth map of Horizon-1.
– Your Input Map Type would be “Grid”
– Your Grid Type would be “Time”
– Select Horizon-t0 as upper grid; and Horizon-1 as lower grid
– Enter your constant interval velocity value and hit OK
– Set the grid parameters for your need, otherwise accept the default values, and hit OK
Repeat the above steps for the other horizons. At the end, you will have several isopach mas depending on the number of your interpreted horizons.
Now, you need to convert those isopach maps to depth maps.
– Go to Tools>Depth Conversion>Depth Map by Isopach Maps
– Give a new name, i.e “Horizon-1_depth”
– Select the isopach maps to sum. In this case, isopach from Horizon-t0 to Horizon-1
– After setting/accepting grid parameters, hit OK
You need to repeat the above steps to you have the depth grids of your each interpreted horizon.
Now, you can create a velocity volume.
– Got to Tools>Trace Calculations>Generate Velocity Volume
– Choose your Survey
– You can either choose to generate velocity volume in time or depth. The process would be similar for either case.
– Create a New Type for Seismic Data Type, i.e. “Tracepak Velocity”
– Click Next
– Choose your horizons in an order from top to bottom
– Choose “TVD Seismic”
– Choose a high enough but reasonable interval velocity for velocity extrapolation below your grids
– Set your starting time=0
– Set your end time to whatever value you want your velocity cube calculation to stop
– Set your sampling rate in accordance with your seismic data
– Click Next to compute
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