If you do not have any better or more detailed velocity information than this will be your best guess. As long as you state the limitation posed by using constant velocities there should not be a problem.

This depends on how detailed and accurate you want the depth conversion to be. "Evaporites" evokes an image of anhydrite and halite which have well known velocities, but if your section contains other minerals, such as dolomite or clays, the velocity depends on both mineral content and porosity (as you are no doubt aware). You might want to test several scenarios to get some idea of "error bars". If you can justify the methods you use AND provide a rough idea of uncertainty, I see no reason that most publications would not at least consider your work. Good luck!

The above replies work well for evaporites which are relatively incompressible. If you also have overburden layers composed of clastics, use a simple function such as v = v0 + kt (velocity increasing linearly with depth). See papers by Faust (Faust, L. Y., 1951, Seismic velocity as a function of depth and geologic time: Geophysics,16,192-206) and Marsden (Marsden Dave, January 1989, Layer cake depth conversion: The Leading Edge, 10-49).

Dear Immo Trinks

Thank you for your answer, I will do that.

Regards,

Dear Dr. Kevin Chesser

Thank you for adding your answer. I believe this best way to get the depth maps.

Regards,

The variability of the formations above the mapped horizons causes the velocity to vary, not variations in the formation itself. The data processing information should include the apparent velocity used to create the normal moveout correction. I suggest you use that information.

Well I agree with @Kevin Chesser and @William Dickson's. The velocity of a earth materials varies even within a formation.

There is always limitations to data and being aware of the fact that there is a better way to achieve this aim is apt. It helps to factor in this limitations when interpreting or analysing the result.

For completeness sake. I agree with Immo Trinks' answer "As long as you state the limitation posed by using constant velocities there should not be a problem". But the variability of the formations above the mapped horizons causes the velocity to that horizon to vary, not variations in the formation itself. Variations within the horizon will vary the velocity to deeper horizons. The data processing information should include the apparent velocity used to create the normal moveout correction. I suggest you use that information to update your three-dimensional velocity matrix.

Dear Dr. Ernest Berkman

Thank you for your answer. Unfortunately, I don't have the apparent velocity because I received this data from a petroleum company as time-migrated data without any additional data.

Dear Dr. Olatunbosun Kafisanwo

Thank you for adding your answer. I will do my best to get good results and If not I will use TWT as it.

Dear Moamen Ali:

You make two interrogations at once: A) one referring to time to depth conversion (“…is it acceptable to use constant…”), and further regarding B) the acceptance of your work in a magazine (“…If I do that and submit a paper…”).

A) There are several reasonable answers to your first question, there is enough material in the responses of colleagues, but let me share my point of view: to give to you a more useful answer, you must give us a little more description of your challenge, we're going on, for example, concern to:

• How is your structural/geological framework?
• Are you talking about a 2D or 3D survey?
• Are you talking about Exploration or Reservoir seismic scales?
• When you say you have 3 horizons, I understand that you have well-logs to correlate the seismic and the wells. Do you have at least one well in your work? or put it another way:
• How do you select your 3 horizons, which are the criteria?
• What did you notice about the paper in time instead of depth?

There are a variety of time/depth conversion techniques, but in general, you must visualize in the geological/structural context, it means: You may require a greater effort to go from TWT to m, for more and more complex structure, the more and more complex velocity distribution. It means your time to depth conversion if you are not enough confidential, may be made more pitfalls than solutions, due to your limitations associated with velocity model building and depth imaging.

A key point for me, I suggest making a review of the sources of error in each time-depth estimation, e.g., if you are working in a structural complex zone, you must evaluate the anisotropy velocity distribution, a key limitation of seismic velocity estimation.

B) According to your second question “…If I do that and submit a paper in a journal…”, please let me say that if you have good research, even in TWT or depth, I understand that there are no problems to accept it to publish. I think you must know that depth conversion concerns the Seismic Interpreter because seismic measurements are made in time, and wells based on a seismic interpretation are drilled in depth. Historically, interpreters have trusted in TWT subsurface imaging, due to the sophisticated ray-trace techniques, but when the velocity distribution and structural complexity are such that the time-image of the subsurface does not permit the interpreter to understand the geology, your time to depth conversion if you are not enough confidential, maybe make more pitfalls than solutions.

It means: maybe in your case study paper, an average velocity model allows you the direct mapping between time and depth, avoid some pitfalls associated with interval velocity modeling. It is a simple change in the scale, following for example the William Dickson's and Ernest Berkman´s brilliant answers.

Last idea or suggestion: thinking about a multidisciplinary workflow using - if you have - the gravity and magnetics together with seismic, answer first the primary question about the geometry and configuration of the basement, then the sedimentary column above.

Please, let me know if you need more help, best regards,

Mario E. Sigismondi