Best practices for seismic data acquisition in highly undulated terrain

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Ramesh Srivastava
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Best practices for seismic data acquisition in highly undulated terrain

Post by Ramesh Srivastava »

Hello Everyone,

Hope you are doing well. Would you please help me to get the answer for the following question, related to Ongoing project. Prescribed reward for the question is now 100 USD, If your answer get selected by client & found 100% satisfactory

What are best practices or Geophysical seismic data acquisition technology in highly undulated terrain areas like Mizoram part of India?
1. Elevation is varying from 20 m to 1800m above mean sea level
2. Highly undulated area
3. Complex geological setting
4. Unable to get subsurface image so far by using seisloop 3D and crooked line seismic 2D.

Looking for your continuing support!
Thanks.

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geophix
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Re: Best practices for seismic data acquisition in highly undulated terrain

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What's your targeted investigation depth and what's the purpose of the survey?

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Re: Best practices for seismic data acquisition in highly undulated terrain

Post by GuyM »

Can you provide some more information please?

- what's the main structural components of the regional geology? Are we talking about a thrustbelt system for example?
- what's the surface and near-surface geology? How rapidly does it change? Are there any shallow, high velocity anomalies (basalts, limestones etc)?
- what's the target depth and structure?

It would also be useful to know:

- a full description of the "failed" surveys to date; source types, receiver types, offset distribution, shot sizes and depths
- what testing was conducted prior to the acquisition geometry being selected in the past; were modelling studies done?
- processing sequence used on the data, including specifics of the software used and algorithms

Reasoning - rugged topography and rapid undulations alone are "solved problems" - there are software packages that are perfectly suited to getting excellent results in these types of areas. So is complex imaging to the resolution of the sampling of the sub-surface wavefield.

However - this is a difficult class of problem, that needs a high quality seismic wavefield and the right tools to resolve.

This tends to mean that "imaging problems" are related to the following broad areas

a) not enough signal getting through the near surface
- absorption, reverberation from high velocity layers, scattering, poor coupling of sources/geophones etc etc
b) signal undergoing complex scattering
- heavily faulted, steep dip, high angle faults, high velocity layers
c) reflected and scattered signal not captured in the acquisition footprint
- offsets too short, spread too small, single componenbt (P-wave) not multi-component (for P-S conversions)
d) reflected wavefield is too sparsely sampled spatially
- so that steep dip aliased noise trains cannot be removed; complex reflections are aliased
e) lack of acoustic impedance contrast at the target zone
- sometimes "no image" is because there is no image
f) the wrong processing tools, or the right tools not used optimally
- specifically near-surface statics, wavefield interpolation, long-offset moveout, and more complex imaging methods

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