Statics Steps

 

 

Apply Statics Shift

Usage:

The Apply Static Shifts step allows you to apply source, receiver, CMP, and trace statics calculated by the various statics processing steps. The static shift values can be applied in either a coarse grain mode or fine grain mode. The coarse grain mode applies static shifts by shifting the trace to the nearest sample in the time domain. The fine grain mode uses a phase shift in the frequency domain to apply the shift, allowing an efficient method of shifting your data in increments less than the sample interval.

 

Input Links:

1) Seismic data in any sort order (mandatory).

2) CMP Statics cards (optional).

3) Receiver Statics cards (optional).

4) Source Statics cards (optional).

5) Trace Statics cards (optional).

 

Output Links:

1)      Seismic data in any sort order (mandatory).

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

Parameter Description:

 

Statics files: Specify the static shifts that will be applied from your selections.

 

Use source statics from data file (ms) — If checked, source statics shifts in milliseconds will be applied from a data file.

 

Use source statics from trace header (sec) — If checked, source statics shifts in seconds will be applied from a trace header.

 

Use receiver statics from data file (ms) — If checked, receiver statics shifts in milliseconds will be applied from a data file.

 

Use receiver statics from trace header (sec) — If checked, receiver statics shifts in seconds will be applied from a trace header.

 

Use CMP statics from data file (ms) — If checked, CMP statics shifts in milliseconds will be applied from a data file.

 

Use trace statics from data file (ms) — If checked, trace statics shifts in milliseconds will be applied from a data file.

 

Static application mode: Specify the mode of statics application.

 

Coarse grain — Statics shifts are applied to the nearest discrete sample position.

 

Fine grain — Statics shifts are applied as a precise phase shift operator in the Fourier domain.

 

Trace header statics: Specify the header location with statics to be applied to your data.

 

Apply header static to data — If checked, the value in the user selected trace header field will be applied to the seismic trace as a static shift.

 

Static header — Use the drop down menu to select the trace header field that will be applied to the trace as a static shift.

 

Bulk shift (ms) — Enter a constant statics shift in milliseconds to apply to all the seismic data traces.

 

Apply negative of static shifts — If checked, the negative of the static values will be applied.

 

Datum Statics

Usage:

 

The Datum Statics step inputs the trace headers from a Seismic Data file and outputs a set of Source and Receiver static files that adjust the data to a floating datum, and CMP static file that asdjusts the data from the floating datum to a flat datum. Alternatively, the Source and Receiver statics can be computed that adjust the surface data directly to a flat datum.  In both cases, the statics are applied using the Apply Statics step.

 

 

Input Links:

1) Seismic data file in any sort order (mandatory).

 

Output Links:

1) Source Statics cards (mandatory).

2) Receiver Statics cards (mandatory).

3) CMP Statics cards (optional, in the case of correction to a Floating Datum).

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

Parameter Description:

 

Reference datum: Specify datum preference.

 

Final datum — If selected final datum is considered.

 

Floating datum — If selected, a floating datum is considered.

 

Datum definition: Specify parameters that define your datum preference.

 

Final datum elevation — Enter a constant value for the elevation of the flat datum.

 

Floating datum: Specify the parameters for a floating datum function, if Floating datum is slected.

 

Mean datum static — If selected, an average operator for calculating the datum static will be used to define the datum.

 

Median datum static — If selected, a median smoothing operator for calculating the datum static will be used to define the datum.

 

Offset weighted datum static — If selected, a weighted CMP elevation function of the form weight = multiplier*(offset **exponent ) will be used to define the datum.

 

Multiplier — Enter the multiplier of the weighting function.

 

Exponent — Enter the exponent of the weighting function.

 

Apply spatial smoothing — If checked, apply spatial smoothing to the floating datum.

 

Radius of smoothing — Enter the radius of smoothing.

 

 

Elevation correction: Specify replacement velocities to correct the elevation.

 

Replacement velocity (Vp) — Enter a constant value to correct the traces to the final datum using the consolidated p-wave velocity.

 

Replacement velocity (Vs) — Enter a constant value to correct the traces to the final datum using the consolidated s-wave velocity.

 

Upholes: Specify whether to apply the uphole time.

 

Apply uphole time — If checked, the uphole static will be applied.

 

Static output: Specify how to output flat datum statics.

 

Output source statics file — If checked, source statics will be output as calculated from the surface to the flat datum.

 

Output receiver statics file — If checked, receiver statics will be output as calculated from the surface to the flat datum.

 

Output midpoint statics file — If checked, CMP statics will be output as zero.

 

First Arrival Picking

Usage:

Input Links:

Output Links:

Example Flowchart:

Step Parameter Dialog:

Parameter Description:

First Break Auto-Picking

Usage:

Input Links:

Output Links:

Example Flowchart:

Step Parameter Dialog:

Parameter Description:

 

Flat Datum Statics

Usage:

The Flat Datum Statics applies a static shift correction to all the traces in reference to a flat datum as defined by its elevation.

 

 

Input Links:

1) Seismic data file in any sort order (mandatory).

 

Output Links:

1) Seismic data file in any sort order (mandatory).

2) Source Statics cards (optional).

3) Receiver Statics cards (optional).

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

Parameter Description:

 

Consolidated P-velocity — Enter a constant value to correct the traces to the final datum using the consolidated P-wave velocity.

 

Consolidated S-velocity — Enter a constant value to correct the traces to the final datum using the consolidated S-wave velocity.

 

Final datum elevation — Enter a constant value for the elevation of the flat datum.

 

Include uphole time — If checked, the uphole static will be applied.

 

Output source statics file — If checked, source statics will be output as calculated from the surface to the flat datum.

 

Output receiver statics file — If checked, receiver statics will be output as calculated from the surface to the flat datum.

 

Stack-Power Optimization Statics

Usage:

The Stack-Power Optimization Statics step calculates surface consistent residual static time corrections by maximizing the power in the stack. Source and receiver super traces are cross-correlated with corresponding CMP super traces to determine a surface consistent static correction. 

 

For 3-D, the input seismic file is required to be a CMP binned seismic volume.  For 2-D, the input seismic file can be in any sort order, as long as Geometry Definition has been applied.  Binning geometry for 3-D surveys should include all shot and receiver locations.  Set the bin origin at the minimum source, receiver or CMP location.

 

Output stacks may be generated to evaluate the quality of the statics.  The stacks show the sorted input file stacked in the analysis window with static corrections applied.  The stacks are accumulated in the frequency domain and back transformed for the final stack trace.  Numerical round off may cause slight variations when compared with stacks from the CMP Stack processing step.   Stack type may be source, receiver or CMP.

 

Analysis stacks at specified intervals may be created to evaluate optimal convergence.  The analysis stacks are a selected subset of source, receiver or CMP lines output to a specified directory.  A unique filename suffix is assigned automatically for each iteration.  Small subsets are recommended to reduce disk storage requirements.  Full volume source, receiver and CMP stacks with user specified filename may be output for the final iteration.

 

An option exists to output to the console a summary of the static corrections generated at the end of each iteration.   The source and receiver statics output by the Stack-Power Optimization Statics Step are applied with the Apply Statics Shift step.

 

Input Links:

1)      Seismic data, 3-D binned or 2-D in any sort order with geometry applied (mandatory).

 

Output Links:

1)      Source statics cards (mandatory).

2)      Receiver statics cards (mandatory).

3)      Selected stack analysis files (optional).

4)      Selected stack volume (optional).

 

Reference:

Ronen J., and Claerbout, J., 1985, Surface-consistent residual statics estimation by stack-power maximization, Geophysics, vol. 50, no. 12, p. 2759-2767.

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

Parameter Description:

 

Pilot — Specify type of pilot to be used in stack-power optimization statics.

 

Use input seismic stack for pilot traces — If checked, pilot traces are built from the input stack seismic data.

 

Use window definition file to build pilot — If checked, pilot traces are built from an auxiliary Window definition card data from the input seismic data.

 

Use fixed window to build pilot —If checked, pilot traces are built from a constant time gate from the input seismic data.

 

Correlation window start time (ms) — Enter the start time in milliseconds for the correlation window used to build the pilot.

 

Correlation window stop time (ms) — Enter the end time in milliseconds for the correlation window used to build the pilot.

 

Output pilot stacks — Select from the drop-down menu to output the pilot stacks used for the optimization. Stacks can be from the midpoint, source, receiver or any combination of these.

 

Statics calculation: Specify the statics calculation parameters.

 

Maximum allowable static (ms) — Enter a value in milliseconds for the maximum static shifts for each iteration. The final static is the sum of statics at each iteration.  The total static may exceed the maximum allowable static per iteration.

 

Maximum number of iterations — Enter the maximum number of iterations for the processing step.

 

Minimum allowable fold — Enter the maximum allowable fold for the processing step.

 

Percent stack power change for termination — Enter the percentage value of the stack power change to terminate the optimization process.

 

 

Compute source term — Select from the drop-down menu to compute the statics for the source component.

 

Filter source term — Select from the drop-down menu to filter or not the source term component.

 

Source term filter radius — If filtering the source term, enter the filter radius.

 

 

Compute receiver term — Select from the drop-down menu to compute the statics for the receiver component.

 

Filter receiver term — Select from the drop-down menu to filter or not the receiver term component.

 

Receiver term filter radius — If filtering the receiver term, enter the filter radius.

 

Surface Consistent Residual Statics

 

Usage:

The Surface Consistent Residual Statics step calculates source and receiver residual statics using a Gauss-Seidel iterative method to solve for the source static, receiver static, structure term, and residual NMO) that provide a best fit to the linear traveltime equations in a least-squares sense.  linear inversion routine to decompose traveltime equations into source, receiver, CMP, and offset related terms. The pick times input to the inversion are picked automatically using cross correlation in a specified time window. You control the window of data for analysis as well as the maximum allowable static that can be computed. A damping filter can be applied to suppress any long period effects associated with the residual statics solution. Options exist for removing either or both the residual normal moveout (RNMO) term and a linear trend from the statics solution. The source and receiver statics output by the Surface Consistent Residual Statics Step are applied with the Apply Statics step.

 

Input Links:

1) Seismic data - NMO corrected CMP gathers (mandatory).

 

Output Links:

1) Source Statics cards (mandatory).

2) Receiver Statics cards (mandatory).

 

Reference:

Wiggins, R. A., et al., 1976, Residual statics analysis as a general linear inverse problem: Geophysics, vol. 50, no. 11, p. 2172ff.

See Technical Note TN-ResSt.doc

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

 

Parameter Description:

 

Statics calculation: Specify parameters related with the statics calculation.

 

 

 

Maximum allowable static (ms) — Enter the maximum allowable static shift in milliseconds.

 

RMS error change for termination (ms) — Error the minium RMS error change from iteration to iteration for the optimization to be considered finished.

 

Minimum allowable fold — Enter the minimum fold allowable for the optimization.

 

Compute source term — Select from the drop-down menu to compute the statics for the source term.

 

Smooth source term — Select from the drop-down menu to filter or not the source term.

 

Smooth source term — If filtering the source term, enter the filter radius.

 

 

Compute receiver term — Select from the drop-down menu to compute the statics for the receiver term.

 

Smooth receiver term — Select from the drop-down menu to filter or not the receiver term component.

 

Receiver term smoothing radius — If filtering the receiver term, enter the filter radius.

 

Compute structure term — Select from the drop-down menu to compute the statics for the receiver component.

 

Smooth structure term — Select from the drop-down menu to filter or not the receiver term component.

 

Structure term smoothing radius — If filtering the structure term, enter the filter radius.

 

Compute residual moveout (RNMO) term — If checked, a least squares linear fit will be removed from the final statics solution.

 

Smooth RNMO term   Select from the drop-down menu to filter or not the RNMO term component.

 

RNMO smoothing radius — If filtering the RNMO term, enter the filter radius

 

 

Trim Statics

Usage:

The Trim Statics step calculates small CMP statics shifts for the data based on alignment of events within the specified window. You specify the start time and the length of the analysis window for calculation and the maximum allowed static shift. The step finds the static shift within these limits using automatic picking of the peak of the cross-correlation amplitude between the trace and the stacked trace for the gather.

 

Input Links:

1) Seismic data in CMP sort order (mandatory).

 

Output Links:

1) Seismic data in CMP sort order (mandatory).

 

Example Flowchart:

 

 

Step Parameter Dialog:

 

 

Parameter Description:

 

Window start time (ms) — Enter the window start time in milliseconds for trim statics analysis.

 

Window length (ms) — Enter the length of the window in milliseconds for trim statics analysis.