Geophysics Forum

So - : https://oilprice.com/Energy/Crude-Oil/T ... ustry.html

What is the difference between time and depth when it comes to diffraction and sensitivity to velocity ? Well you'd never normally depth convert a stacked (normal ray) section, so it doesn't really come up. Or rather, I'd be asking what your goal is when you do it(!) Mostly depth conversion is for ...

Is this question tied to depth conversion at all? One of the approaches you can use is: - interpret horizons in two-way-time on a pre-stack time migration - develop a layer based interval velocity model using the V(rms) velocities from Pre-stack time migration and well control - depth convert layer ...

Well - I'm mostly pointing you to the SEG Wiki, which is mostly Oz Yimaz's book. If you can get hold of a copy it will be a big help.

The SEG Wiki Pages may help : https://wiki.seg.org/wiki/Kirchhoff_summation "The diffraction summation that incorporates the obliquity, spherical spreading and wavelet shaping factors is called the Kirchhoff summation, and the migration method based on this summation is called the Kirchhoff migratio...

It's how fast the velocity varies horizontally. If you had very boring geology - just horizontal, flat layers, deposited and compacted normally - then you would see a vertical variation in seismic velocity, but no lateral variations. On the other hand, when you have those same flatish layers overlyi...

Ah - you misunderstand, I just found this library : https://pyswarms.readthedocs.io/en/latest/ and this thread on research gate: https://www.researchgate.net/post/Is_it_easy_to_implement_Genetic_algorithm_and_Particle_swarm_optimization_on_Python My observation was that we tended to find better main...

Well, no, but you might want to consider making the leap to Python at some stage. A quick google shows a bit more activity on PSO in terms of open libraries in that community. More or less anything we looked for we found very quickly in Python. Even stuff like single-click outputs of Powerpoint file...

I used to have a nice powerpoint slide illustrating this; it was animated and added in more and more circles centered on the same straight line until a new "wavefront" formed; that's back when I used to run seismic processing training courses

Hmm - I'm not sure how critical this one area is to the industry survival; WesternGeco have no boats, and I'm prepared to wager the other companies are all in the "data library" game as well. They like new real estate (ie under explored areas) for the speculative potential, rather than the actual po...

Not come across that term but it seems to be used when there's complex back-scatter patterns. Back-scatter is another way of saying diffractions. Where you have a rough surface - for example a seafloor that has a small amount of soft sediment over a steeply dippling, uplifted, harder and layered roc...

What will happen for diffraction? You get a curve shape on an CDP gather; this can be "flattened" using NMO, but the velocity needed to flatten the diffraction will be higher than the true stacking velocity that flattens the reflections. Not that diffractions and reflections can appear at the same ...

Seismic testing uses powerful airguns that blast sounds at the ocean floor repeatedly for months at a time. Marine experts say these sounds can harm marine and coastal resources – and could have significant impacts on the state’s fishing and tourism industries. After a lot of R+D it looks like effe...

Coherence is how similar two traces are to each other.
There's a few ways of calculating this (or terms it can mean) : https://wiki.seg.org/wiki/Coherence

A surface in a sub-surface modelling package can be multi-valued; like the top of a salt dome, that can bend over. Or a thrut fault. By multi-valued, I mean that at give X,Y coordinates the surface is present in the model more than once. With a grid, you have an z, y and z value. There's only one z ...

Well - I have run a written and run a few seismic processing courses in my time

Oh - thank you for asking these questions! I've stepped back from geophysics after >25 years in seismic and while I'm very happy with my new career direction, it is also nice that all of the stuff that I have learned over the last quarter of a century is not sitting in my head not helping anyone :-)...

When you have lot of seismic data containing the same information. For example, modern marine seismic is often collected at a 2ms sample interval, and with a receiver group interval of 12.5m This would allow for frequencies up to 250Hz (Nyquist) and a CMP bin spacing of 6.25m Given the filtering eff...

How do you relate the NMO equation to Pythagorean theorem? In the picture, you have a right angled triangle formed by : - half the source receiver distance; ie from the source to the mid point - the vertical depth of the reflector below that midpoint - the ray-path from the source to the mind point...

I'll keep that in mind, if I can.

It is hard when there is so much technical language at play.

Did you read the second link? That walks you through how DMO and NMO are combined when it comes to a dipping interface. Remember we are working with events in two-way-time; if you want to consider angles, then you have to be dealing with distances (or depths), not times. Think about the method of di...

You are confusing NMO (equation 1) and DMO (equation 2) https://wiki.seg.org/wiki/NMO_for_a_flat_reflector https://wiki.seg.org/wiki/Principles_of_dip_moveout_correction DMO is a partial prestack time migration with a weak velocity dependence, that corrects the velocity for dip and reducing CMP smea...

"Sudden change in facies" means that the rock type changes very quickly. "near surface scattering" is where small faults and heterogeneities in the weathered layer diffract seismic energy; this is often under-sampled spatially and so appears as noise. It'sthe reason why you don't see further signal ...

Seismic wave theory.

You are using an integral form of the wave equation.

SEG Wiki has you covered :
https://wiki.seg.org/wiki/Dictionary:Wave_equation
https://wiki.seg.org/wiki/Dictionary:Ki ... s_equation

Huygens' Principle says that every point in a reflector can be considered to be a source of secondary wavelets. So try this. Get a pencil, a ruler, a coin and a piece of paper. - draw a straight line with the ruler, about 15cm long - place the coin on that line, so that half is on one side, and half...