This section documents the processing steps available in the VSP Steps category.
Processing steps currently available are:
Usage:
The Apply VSP Traveltimes step applies the traveltimes corrections stored in the trace headers of the seismic file, as computed from Calculate VSP Traveltimes, so the gather can be flatten according to these corrections.
Input Links:
1) Seismic data in any sort order (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Correct first arrival traveltime to : Specify where the VSP first arrival traveltimes will be corrected to.
Constant time If selected, VSP first arrival traveltimes will be correct to a constant two-way time as defined in Constat Time (ms).
One-way direct arrival time If selected, VSP first arrival traveltimes will be correct to the one-way direct arrival time as defined in the picking file.
One-way vertical time from Ground level If selected, VSP first arrival traveltimes will be corrected vertically to the one-way time corresponding to the ground level location.
One-way vertical time from Seismic datum If selected, VSP first arrival traveltimes will be corrected vertically to the one-way time corresponding to the ground seismic reference datum.
Two-way vertical time from Ground level If selected, VSP first arrival traveltimes will be corrected vertically to the two-way time corresponding to the ground level location.
Two-way vertical time from Seismic datum If selected, VSP first arrival traveltimes will be corrected vertically to the two-way time corresponding to the seismic reference datum.
Application mode: Specify the mode of statics application.
Coarse grain If selected, statics shifts are applied to the nearest discrete sample position.
Fine grain If selected, statics shifts are applied as a precise phase shift operator in the Fourier domain.
Apply negative static shifts If, checked apply a negative of the static shifts.
Constant time (ms)/ Bulk shift (ms) Enter the constant time in millisecond to be used as reference if Constant time is selected. Enter a bulk shift value in milliseconds to shift all the data simultaneously with this value.
Usage:
The Calculate VSP Traveltimes step computes corrections for the travel times based on the picking of the first arrivals (auxiliary VSP Frist Arrivals card data). The output seismic file has the trace headers corresponding to VSP depths, times and velocities update accordingly. This file can then be used as input for the Apply VSP Traveltimes step in order to flatten the record.
Input Links:
1) Seismic data in any sort order (mandatory).
2) VSP First arrivals card data (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Well location: Specify general parameter related with the well corresponding to the VSP.
Kelly bushing Enter a value for the Kelly bushing (KB) of the well corresponding to the VSP. KB is defined in project units (m or ft).
Seismic reference datum Enter a value for the seismic reference datum (SRD). SRD is defined in project units (m or ft).
Ground elevation Enter a value for the ground elevation/level (GL). GL is defind in project units (m or ft).
Mean sea level Enter a value for the mean sea level (MSL). MSL is defined in project units (m or ft).
Project updates: Specify either if the geometry is updated from the project or if the project settings will be updated with current parameterization.
Update from project Updates the corner points from the SPS data that has been associated with the project using the Survey > SPS Database menu.
Update project Use this to broadcast the corner points so that they can be used by to set the Easting and Northing ranges of plotting functions, such as the Attribute Map used later in this flow.
Near surface model: Specify parameters related with the near surface model.
Weathering depth Enter a value for the total depth of the weathering layer. Depth defined in project units (m or ft).
Weathering velocity Enter a value for the velocity of the weathering layer.
Replacement velocity Enter a value for the replacement velocity to be used to comput the VSP traveltime correcitons.
Marine VSP If checked, VSP is assumed to be acquired in marine environment.
Fluid velocity Enter the fluid velocity if VSP was acquired in marine environment.
Usage:
The VSP CMP Transform step moves offset VSP data to the reflecting point location (approximately half the distance for the largest offset) assuming that there is no dip.
Input Links:
1) Seismic data in any sort order (mandatory).
2) VSP First arrivals card data (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Line orientation: Specify which CMP location is closer to the well head.
First CMP located at well If selected, first CMP is assumed to be located at the well.
Last CMP located at well If selected, last CMP is assumed to be located at the well.
CMP line number Enter the CMP line number.
First CMP location number Enter the first CMP location number.
CMP location increment Enter the CMP location increment.
CMP bin size Enter CMP bin size.
Output sample interval (ms) Enter the sample interval of the output VSP data.
Usage:
The VSP Corridor Stack stacks a VSP record after a corridor being extracted. The resulting VSP seismic file has the number of traces as defined in Number of duplicate traces parameter.
Input Links:
1) Seismic data in any sort order (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Corridor length (ms) Enter the length of the corridor of data to be extracted in milliseconds.
Number of duplicate traces Enter the number of duplicated traces in the corridor stack.
Number of full length traces Enter the number of full length traces to be extracted.
CMP line number Enter the CMP line number corresponding to the VSP location.
CMP location number Enter the CMP location number corresponding to the VSP location.
Usage:
The VSP Deconvolution step applies deconvolution operators using Wiener-Levinson algorithm to the VSP data. VSP Deconvolution is normally applied to records representing the downgoing or upgoing wavefields.
Input Links:
1) Seismic data in any sort order (mandatory).
2) Seismic data with downgoing wavefield (optional).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Operator type selection:
Spiking If selected, applies a spiking deconvolution to the VSP data.
Predictive If selected, applies a predictive deconvolution to the data.
Prediction length (ms) Enter the prediction length of the predictive deconvolution operator.
Pre-whitening % Enter the amount of white noise to add. The zero lag of the autocorrelation function is increased by this amount to induce stability in the matrix solution.
Operator length (ms) Enter the length of the operator to be calculated and applied in milliseconds.
Window start (ms) Enter the start time in milliseconds of the deconvolution design window.
Window length (ms) Enter the length in milliseconds of the deconvolution design window.
Input downgoing data and apply operators If selected, an auxiliary seismic file with the downgoing field is used as auxiliary data.
Usage:
The VSP Downhole Locations carda data is used to store the positional downhole receiver locations to be used by VSP Geometry Definition step.
Step Parameter Dialog:
Parameter Description:
Downhole line Enter the downhole lin value.
Downhole location Enter the downhole location.
Surface Easting Enter the surface Easting coordinate corresponding to the downhole location.
Surface Northing Enter the surface Northing coordinate corresponding to the downhole location.
Surface elevation Enter the surface elevation corresponding to the downhole location.
Measured depth Enter the measured depth coordinate corresponding to the downhole location.
Usage:
The VSP Extract Corridor step extracts a corridor of data base on the first arrivaltimes. This allows removing noisy data and focus on reflections close to the well location.
Input Links:
1) Seismic data in any sort order (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Corridor length (ms) Enter the length of the corridor of data to be extracted in milliseconds.
Number of full length traces Enter the number of full length traces to be extracted.
CMP line number Enter the CMP line number corresponding to the VSP location.
CMP location number Enter the CMP location number corresponding to the VSP location.
Usage:
Input Links:
Output Links:
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Usage:
The VSP Geometry Definition step assigns survey information to the VSP trace headers based on the source, receiver, and observer notes SPS files. The VSP Geometry Definition step assigns CMP number based on the source and receiver numbers using the following formula: CMP Location = (Source Location + Receiver Location) / 2. Therefore, for 2D lines it is imperative that source and receiver locations as defined in the SPS files share the same coordinate system. This implies that Source location 1 has the same X,Y position as Receiver location 1, and that Source location 2 has the same X,Y position as Receiver location 2, etc .
Input Links:
1) Seismic data in any sort order (mandatory).
2) Observers Notes SPS Format cards (mandatory).
3) Receiver Locations SPS Format cards (mandatory).
4) Source Locations SPS Format cards (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Well description: Specify general parameters related with the well.
Well name Enter the name of the well corresponding to the VSP.
Well number Enter well number corresponding to the VSP. Well number can be defined as the UWI.
Well Easting Enter Easting coordinates of well head.
Well Northing Enter Northing coordinates of well head.
Project updates: Specify either if the geometry is updated from the project or if the project settings will be updated with current parameterization.
Update from project Updates the corner points from the SPS data that has been associated with the project using the Survey > SPS Database menu.
Update project Use this to broadcast the corner points so that they can be used by to set the Easting and Northing ranges of plotting functions, such as the Attribute Map used later in this flow.Azimuth definition: Specify the origin of azimuth.
Zero degrees azimuth = East If selected, then zero degrees of source-receiver azimuth will be set equal to due East.
Zero degrees azimuth = North If selected, then zero degrees of source-receiver azimuth will be set equal to due North.
Kill undefined traces and records If checked, traces undefined after applying the geometry will be flagged as dead.
Reverse VSP (source in Well) If checked, reverse VSP source location in well.
Norminal receiver spacing Enter the nominal (in m or ft) distance between receivers within the well.
Usage:
The VSP SPS Relation Locations carda data is used to store the relationship between surface and downhole receiver locations to be used by VSP Geometry Definition step.
Step Parameter Dialog:
Parameter Description:
Record number Enter the record number. This value should correspond to the FFID store in the VSP seismic file.
Source line Enter the source line as defined in VSP Surface Locations.
Source location Enter the source location as defined in VSP Surface Locations.
From channel Enter the number of the first active channel.
To channel Enter the number of the last active channel.
Channel increment Enter the channel increment.
Receiver line Enter the receiver line as defined in VSP Downhole Locations.
From receiver Enter the number of first receiver.
To receiver Enter the number of last receiver.
Receiver increment Enter the receiver number increment.
Usage:
The VSP surface Locations carda data is used to store the positional surface locations to be used by VSP Geometry Definition step.
Step Parameter Dialog:
Parameter Description:
Surface line Enter the point lin value.
Surface location Enter the point location.
Surface Easting Enter the surface Easting coordinate corresponding to the point location.
Surface Northing Enter the surface Northing coordinate corresponding to the point location.
Surface elevation Enter the surface elevation corresponding to the point location.
Point depth Enter the measured depth coordinate corresponding to the point location.
Uphole time Enter the uphole time.
Usage:
The VSP Wavefield Separation steps allows filtering the downgoing or the upgoing wavefields by applying a moving average, a median or a F-K filter.
Input Links:
1) Seismic data in any sort order (mandatory).
Output Links:
1) Seismic data in any sort order (mandatory).
Example Flowchart:
Step Parameter Dialog:
Parameter Description:
Filter type: Specify type of filter to be used for the wavefield separation.
Use moving average filter If selected, uses a moving average filter to separate wavefields.
Use median filter If selected, uses a median filter to separate wavefields
Filter length (number of levels) Enter the filter length in nu