456 Posts in 224 Topics by 67 members

Noise Attenuation

Forum » Noise Attenuation » Linear noise attenuation - Land Data

If this is your first visit, you will need to register before you can post. However, you can browse all messages below.

Moderators: Andy Juniper , Guy Maslen , Keleigh Jones

Page: 1 , 2 Go to End
Author Topic: Linear noise attenuation - Land Data 7547 Views

Re: Linear noise attenuation - Land Data Link to this post

in this process you used Fk can you send me the dump of fk analysis window, because i want to see the linear noise portion which to reject in the fk analysis.

Linear noise attenuation - Land Data Link to this post

Removing linear noise such as direct arrivals from Land data can often prove challenging because of issues related to the acquisition typically sparse receiver spacing leading to aliasing issues. The example flow attached to this forum topic shows the methodology to interpolate a land shot record from a nominal 25 metre group interval to a 6.25m group interval in order to dealias the input data ie a 4-1 interpolation. The flow incorporates the application of K Filters to prevent aliasing when the record is returned to it's original group interval, and uses an FK domain mute to attenuate the linear noise.

A powerpoint presentation is also provided to show the effects of the linear noise removal.

Re: Linear noise attenuation - Land Data Link to this post

please explain jobdeck, i have data with group interval 50m and i want to interpolate shot record from 50mgroup interval to 25m group interval in order to increase the fold of data.

Re: Linear noise attenuation - Land Data Link to this post

Masood,

I wil give you an overview of the flow, there is some replication in it as we are carrying out a four to one interpolation, and with Claritas better results are achieved with this sort of flow by doing this in stages ie running a 2-1 interpolation then running a second 2-1 interpolation on the output from the initial flow.

If you run as you suggest initially an interpolation from 50 to 25 metres then you can see if you are able to unwrap the aliasing successfully with just a 2-1 interpolation.

The front end of the job processes 3 to 4 are doing some initial data prep, replicating key headers and applying any edits as you would not want to interpolate noise. Processes 5-10 prepare the data for interpolation by setting the primary/secondary keys as required, updating headers and as we will NMO the data prior to interpolation increasing the data length and shiffting it down by 2000ms so that when we NMO we do not mute any data of above the 0 time axis. Processes 11-25 position dead traces in between the acquired live traces, we use the RENUMBER module to update the CHANNEL header so it increments by 2, the MISSING module then inserts the dead traces in the gaps, we then use HDRMATH and SETHEADER modules to create the key headers such as OFFSET into the headers so that the data will NMO correctly. Processes 26-28 then perform the actual data interpolation using the RUNMIX module set to only work on ZERO traces and running within an ENSEMBLE not across, all within an NMO wrap. Processes 29 to 47 are performing the second pass of the interpolation so may not be required if you only need to apply a single pass. Processes 48 and 49 reset the lasttr flags and back of the STATIC correction. Processes 51 to 57 applying the linear noise removal in the FK domain and K Filters the data to dealias the data prior to dropping out one lot of the interpolated traces. 60 to 62 drop these traces, and processes 63-70 drop the second lot of interp traces and KFilter to dealias. We then save the traces out at the same fold as the input data for further processing.

Re: Linear noise attenuation - Land Data Link to this post

i have used this but i stuck at Missing module, in job you used 3249 in SKEY2 filed. how we choose this value.
if i run the job with parameter already in it it gives error of runpython.

in job static module used to increase the length of data and apply bulkshift to data. should we apply bulkshift to nmo file before running the job.
please explain in detail.

Re: Linear noise attenuation - Land Data Link to this post

The eample job flow provided was developed on a particular dataset which had a max channel of 1625, the RENUMBER module takes the channels and inserts gaps into the shots ie the CHANNEL number changes from 1-1625 to 1-3249 ie every other channel is missing. The MISSING module then interpolates dead traces into the available spaces and these dead channels then have data interpolated onto them by the RUNMIX module. So the value 3249 in the MISSING module needs to be the maximum channel number on your dataset after the RENUMBER module has inserted the gaps.

The STATIC shift is in the job to prevent data being NMO corrected above T0 and being muted out, we do not need to apply the same static shift to the velocity field as we are using a suitable constant velocity as part of the interpolation process.

I hope this answers your questions.

Andy

Re: Linear noise attenuation - Land Data Link to this post

Masood,

Attached below are the requested FK Spectras.

Regards

Andy

Re: Linear noise attenuation - Land Data Link to this post

in the job example you used 1014 in OFF2 field, and in DX field used Trace. at this stage tarces are interpolated and now we have 3249 tarce per shot.
when i used this flow for our dataset, 120 channels data, in first part of interpolation my channels becomes 239, and after second partof interpolation my channels becomes 477. when i used this value 477 in kfilter, job finished after error, it gives erorr about inconsistent trace length. please suggest

Regards

    7547 Views
Go to Top