Description

Main function for MF Search that determines all parameters of MF

This procedure prepares MF parametrization tables that used by MF Engine procedures. This procedure determines all parameters for all types of implemented MultiFocusing engines

Output data – MF Tables Parametrization

Input data

SEG-Y data handle (for auto Time Range)

Service object provides the ability to read seismic data in specified format. It used for automatic determination of time range in seismic data (optional)

Trace headers (for auto Aperture Offsets)

Table of trace headers. Is used for automatic determination of minimum and maximum offsets (optional)

Parameters

V0

Average velocity in the upper part of the section.

Used for calculation of time correction in MF and transformation R CRE<->V RMS-MF.

Usually is set equal to the Replacement Velocity.

Default: 1500

Dimension Of MFT Process

Dimension of MF search:

• 2D
• 3D or Wide
• 2D Line

Default: 2D

Values: 2D, 3D, wide 2D line

Search Type

Type of MF search:

• Reflection Only – simplest MF Search aimed to stack only reflection events.
• Reflection and Diffraction - search aimed to stack reflection events and enhance diffraction. To each iterated R CREadded additional R CEEequal R CRE.
• Diffraction Only – aimed to stack only diffraction events. Searching only for pairs R CRE=R CEE.

Default: Reflection and Diffraction

Values: Reflection and Diffraction

           Diffraction Only

           Reflection Only

Use Prestack Mute function

Determination of type and form of MF Mute Function. There are 3 types of MF Mute functions; two of them based on the correlation between the time-offset and R CRE. For the shallow part of the data, the radius of the wave-front approximation cannot be much greater than the offset. For each time determines max offset for stacking using following equation:

OffsetMAX(t)=R CRE(t)*Mute Factor(t);

The difference between the types is in R CREdetermination.

• Firsttype– maximum offset determinate for each iterated CRE,
• Second type – the R CREvalues calculate from the low (left) border of the velocity constrain function for given imaging point location.
• Third type of MF Mute function is based on the limitation of maximum time correction during MF stacking.

Turn ON/OFF in order to switch to the second type MF Mute Function calculation, based on the velocity constrain.

Offset-mute function

Table for time-variant Mute Factor calculation

Default: Time – 1sec

Mute Factor – 3

Mute Factor range: 0.2-4

Mute cee factor

Delta Velocity OffsetMute(-1 not use)

Min-Max Velocity Contour

Time Range

Start

Seismic data start time.

Filled automatically when  SEG-Y Data Handle (for auto Time Range)connected, otherwise must be defined by user.

End

Seismic data end time.

Filled automatically when  SEG-Y Data Handle (for auto Time Range)connected, otherwise must be defined by user.

Step

Size

Dip Range(Beta)

From

First value of angle range to scan

To

Last value of angle range to scan

Default:±0.8 rad

Range:±1.57 rad

Step

Quantization step during the search

Default:0.01 rad

Range:0.08-0.0001 rad

Size

Number of angles that will be searched, recalculates automatically

Azimuth of Dip Range(Gamma)

From

First value of angle range to scan

To

Last value of angle range to scan

Default:±0.8 rad

Range:±1.57 rad

Step

Quantization step during the search

Default:0.01 rad

Range:0.08-0.0001 rad

Size

Number of angles that will be searched, recalculates automatically

R-cre Range

Reference CRE Offset

Reference offset for CRE table calculation.

Default:3500

Range:usually around max offset of the seismic data

Minimum CRE Radius

Minimum CRE radius matches to low velocity

Default: 5

Maximum CRE Radius

Maximum CRE radius matches to high velocity

Default: 100000

Time Step

Used for CRE radius table construction

Default: 8

Size

Number of CRE radii that will be searched, recalculates automatically

R-cee Range

Parameterization for digitization of CEE radii search table. Table of radii is created as following; the difference between kinematic corrections for two neighbor radii on reference offset shouldn’t exceed the time step.

Reference offset corresponds to the stacking aperture (base of super-gather).

CEE Aperture

Reference offset for CRE table calculation

Default: 300

Range: usually corresponds to the stacking aperture

Minimum CEE

Default:-500

Maximum CEE

Default:500

Time Step

Used for CEE radius table construction

Default:8

Max Number of CEE per CRE

Number of CEE radii that will be searched, recalculates automatically

Velocity Range

Parametrization of velocity, while search performed in radii more useful, ranges to be defined as velocity

From

Minimum velocity for velocity analysis (search)

Default: 1500

To

Maximum velocity for velocity analysis (search)

Default: 8000

Step

Parameter used for visualization of the velocity semblance

Default: 50

Size

Number of velocities for visualization, recalculates automatically

Anisotropy

Anisotropy of the wave-front elements in MF is defined by three parameters R 1 CRE, R 2 CREand ɸ CREwith assumption that reflectors above the target reflector have low curvatures and anisotropy is limited. Parameters R 1 CRE, R 2 CRE, which can be recalculated into V RMSand V INT, are not dependent on dip unlike in CMP where Vst depends on dip.

Azimuthal variation of MF move out velocity is an ellipse in the horizontal plane, irrespective of the type or degree of intrinsic anisotropy. Parameters R 1 CREand R 2 CREare transformed into V 1 RMS==V FASTand V 2 RMS==V SLOW. These additional parameters make possible to take into the account the anisotropy of the subsurface. In the same time this dramatically increase the calculation time.

Anisotropy

Turn on/off the anisotropy search.

• NON – no anisotropy.
• One Azimuth In Line Direction – Anisotropy search performed only along 1 azimuth.
• All Azimuths – search performed for all azimuths.

Default:NON

Values: NON, One Azimuth In Line Direction, All Azimuths

Max CRE Anisotropy

Maximum difference between VFAST and VSLOW to be searched, directly influence on calculation time

Default:0.2

Values:0,6-0.9

Azimuth Factor

Sparsing of number of azimuths that will be searched

1- all azimuths

Default: 1

Values:1-10

Aperture

Parametrization of super-gather formation.

Super-gather is actually a time projection of the First Fresnel Zone.

All events within this range will be stacked into one sum trace.

Aperture In Inline Direction

Aperture in stack line direction for 2D case and InLine direction for 3D case.

Measured in in the percentages of the First Fresnel Zone.

Default: 50

Range: 10-100

Aperture In Xline Direction

Aperture in perpendicular to stack line direction for 2D case and XLine direction for 3D case.

Measured in in the percentages of the First Fresnel Zone.

Default: 50

Range: 10-100

Azimuth aperture

Maximum offset

Minimum offset

Min Fresnel Zone

Average Frequency

Frequency used to compute size of the First Fresnel Zone.

Default:45

Range:Usually used nominal frequency of the seismic data

Max Reflection Angle

Set Initial azimuth manually

InitialAzimut

Correlation parameters

Parametrization of semblance MF calculation

Correlation Type(Don't change)

Use max time arrival shift

Turn ON/OFF third type of MF Mute Function calculation according to limitation of maximum time shift during the MF stacking. It can be used together with first or second type

Max time arrival shift

Value of maximum Time Shift during MF stacking

Selection Window

Min Fold

Minimum MF Fold used for calculation, if fold is smaller than Min Fold the semblance of such sample is set to zero

Default: 5

Range: 5-30, influence the shallowest part of the section

Max Fold

Maximum number of traces considered for stack. Algorithm of sparsing super-gather implemented in order to leave equal number of traces per offset class

Default:99999

Time variant correlation Window

Window used to smooth semblance in time

Default: 14

Range: 5-30

Wave Values

Smooth For Detection Type(Don't change)

Smoothing Cre

Smoothing Angle

Correlation Cre

Window used to smooth semblance along velocity axis

Correlation Angle

Window used to smooth semblance along angle axis

Selection distance Cre

Selection distance Angle

Max number of directions

Number of MF-NMO applied events to be saved in database for each time sample.

Wavelets (events) preserved in database according to the semblance value, starts from the highest.

Default: 10

Range: 5 – 100

Limit number of direction by semblance

v

Cmp fold

Cmp step

Velocities for view

Comments

Angle ranges– usually angle range is a separate test. This is an important parameter in 2D processing that can suppress out “of plane energy” coming with anomalous high angles (parallel to the surface). In 3D processing this parameter directly influence on calculation time.

R CREParameters – In general import the total number of CRE radii that will be searched, for test it might be around100-130 while for “Final Case” might be 200+. This parameter directly influence on calculation time.