See the paper below it may help. http://dx.doi.org/10.1190/segam2013-0137.1
Mousavi Faezeh:
Pore pressure prediction in Hampson Russell performs and by the module, VelPro can be performed using one of two main methods: the Eaton method (using a velocity ratio), and a modified Eaton method known as the Gamma EB (Eaton- Bowers) method.
VelPro is a velocity modeling tool, so the Vi/Vn portion of both equations will come from VelPro. The Vi is the interval velocity observed at a location, and Vn is the normally pressured velocity (i.e. as if overpressure is not present). Vn is modeled by one of the velocity functions on the left side of the display, by plotting seismic velocity functions and fitting them.
The other parameters, such as the density equation, the stress equation, the Eaton exponent, etc. are empirically derived, and deriving them is outside of the scope of VelPro. For example, to calculate the coefficients in Gardner’s interval velocity to density equation one needs to cross plot interval velocity (say from a sonic) with density logs at multiple wells, and do a curve fit. This is not something that can be done in VelPro currently, but we have other packages in the Geosoftware suite that can.
The main purpose of the pore pressure prediction module in VelPro is not to derive all of these parameters (other than the Vn equation), but to use them to compute entire volumes of pore pressure, vertical effective stress, etc. from velocity volumes in the VelPro project.
A suggestion workflow is perhaps the following:
1- Seismic velocity quality control. You may have a velocity volume from seismic inversion.
2- Calibrate seismic interval velocities to well-sonic logs.
3- If you have a prestack seismic inversion, this is a critical step, and because you calibrate the well-logs before, it is a new check of this step, when you correlate the wells and build the initial model and therefore, you know by the inversion analysis the quality of your inversion.
4- Modeling and compute the normal pressure velocity-trend function.
5- Calibrate the computed pressure-gradient to well-logs data available.
6- Calibrate pore pressure-volume from velocities and pore pressure parameters from well-logs.
7- Estimate and extract overburden gradient, pore pressure gradient, and fracture gradient in proposed new locations.
Best regards, let me know if you need more questions,
Mario E. Sigismondi
Mario Emilio Sigismondi
What format of input data in VelPro? Segy or something?
use velocity inversion or seismic data in input?
Mousavi, please, check the file Tutorial from HR.
Also, I think the best velocity volume (3D) or section (2D) is related to the output of your seismic inversion because you use it to calibrate your key-well-logs dataset. Also, remember that if you have a post-stack acoustic inversion, you DO NOT have velocities as an output, only in a prestack / elastic/simultaneous inversion you can get output volumes such as Vp (Zp, Zp, Density, etc.).
Let me know if you have additional issues. Best regards, Mario
.
Mario Emilio Sigismondi
How can I output the impedance section obtained from inversion?
Dear Mousavi:
Hampson Russell: One option is:
Data Explorer ---> Seismic ---> You choose the seismic file ---> Options (below tab) ---> Export.
Another option is: go to the address of your project ---> choose the seismic file ---> Copy
Cheers, Mario
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