Which one is more sensitive to multiples, PSDM or PSTM?

Oil and natural gas exploration -- geology and geophysics
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shahriar123
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Which one is more sensitive to multiples, PSDM or PSTM?

Post by shahriar123 »

Consider a geology setting with nearly flat layering in which, CMPs contain multiples. If two imaging approaches, PSTM and PSDM, is going to be used on this data, which one would be more sensitive to multiples? I mean, the effect of multiples in deteriorating image quality and resolution.

GuyM
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Re: Which one is more sensitive to multiples, PSDM or PSTM?

Post by GuyM »

It's more that the multiples (and any residual) will make it harder to determine the velocities.
That in terms makes it easier to do PreSTM, which requires a less accurate velocity field.

However - would you ever run a PreSDM without doing a PreSTM first? Probably not

Either way - the presence of multiples (prior to any demultiple) isn't always a good indicator of how effective you might be at suppressing or removing those same multiples; strong multiples are usually the easiest to address.

shahriar123
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Re: Which one is more sensitive to multiples, PSDM or PSTM?

Post by shahriar123 »

Yes, you are right.

I am looking for reasons that makes the result of PSDM be of less resolution than PSTM. Since the CMPs contain multiples, I am look at as a possible reason.

GuyM
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Re: Which one is more sensitive to multiples, PSDM or PSTM?

Post by GuyM »

What do you mean by "less resolution"?

if you convert the preSDM back to TWT and compare to the PreSTM what do you see?

Look for faults - are the sharper? The PreSTM will probably have small diffractions along the fault-plane; these should be focussed on the PreSDM.

It may be that your velocity model is incorrect; this is usually the hard part of PreSDM work.

shahriar123
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Re: Which one is more sensitive to multiples, PSDM or PSTM?

Post by shahriar123 »

If we have a pull up in PSTM, should this pull up be visible in PSDM converted to time?

GuyM
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Re: Which one is more sensitive to multiples, PSDM or PSTM?

Post by GuyM »

Of course. But the imaging beneath the pull up will be better.

The overall effect of PreSDM will be to focus the energy more, so the image is better resolved.

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