2 seis processing flow

7/28/2019 2 Seis Processing Flow

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Processing Flow


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The objectives of data processing may be summarized as :

To produce seismic cross-section representative of geology

To enhance the signal and reject the noise

To meet the exploration objectives of the client

Data Processing Overview


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The Sequence of EventsRaw shot records

(with some amplitude compensation applied)

Final migrated section

What do we start with in DataProcessing?

How do we get here?


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Before any processing can take place, we need to:

Internal project meeting

Client meeting - determine objectives etc

Perform inventory check Produce testing plan

Project set-up - resource allocation etc

Project Planning


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Data processing will usually commence with the receipt of thefollowing (or part thereof) :

New Data:

Tape containing recorded seismic data (trace sequential or

multiplexed)

Observer logs/reports

Field Geophysicist logs/reports and listings

Navigation/survey data

Field Q.C. displays Contractual requirements

Data Processing - In the beginning.


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Re-Processing:

Tape containing recorded seismic data with geometry applied

(usually).

Contractual requirements

Data Processing - In the beginning.


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Data Format defines:

How the data is arranged and

stored.

Reformat

Processing Sequence

Reformat

This will usually follow anIndustry standard convention.

e.g. SEGD, SEGY for

magnetic media


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Data Processing - raw shot data

Loss of ampl itude with

time

Loss of f requencies with

time

L inear noise e.g. dir ect arr ivals

Refl ection - hyperbolic

Data corresponding to one shot (located somewhere on the earth) wh ich was recorded into 96

(onl y data from 1-93 shown on plot) dif ferent receivers (also located somewhere on earth! )

Time zero ref.

i .e. reference

is time when

shot fi red


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Processing Sequence

Reformat

Geometry definition? ? ? ? ? ?

Where are the shotsand receivers located ?

Important values for data processing are

sourcereceiver OFFSETS!

Geometry Definition


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What if the surface

elevation changes ?

datum

Field Static Corrections

Processing Sequence

Reformat

Geometry definition

Field Static corrections(land, shallow water, transition zone)

i.e. remove the difference

in travel time caused by

shots and receivers being at

different elevations


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Wheres all the source

energy gone ? Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Geometric spreading, absorption etc

Amplitude Recovery


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How to remove noise? Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Noise Attenuation

Despike, K-filtering, AAA .


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How to improve the

vertical resolution? Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

Compensate for the filtering effects

of the earth etc

Deconvolution (An inverse of filtering process )


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How to order the data? Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Some processes must be carried out in the

CMP domain

Multiple Coverage Acquisition techniques

CMP Gather


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Velocity Analysis

Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

How to compute a

better velocity field?


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How to remove false

reflections?

CMP gather

offsettime

Demultiple

Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

Demultiple (marine)


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How to correct for time

differences due to offsetwithin the CMP?

offset

time time dif ferencedue to offset

CMP gather

NMO Correction

Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

Demultiple (marine)

NMO correction


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Do the reflections all comefrom a single point?

midpoint

Processing Sequence

Reformat

Geometry definition

Field Static corrections

(land, shallow water, transition zone)

Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

Demultiple (marine)

NMO Correction

DMO Correction

DMO Correction


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How to reduce the

number of traces?

CMP Stack

Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

Demultiple (marine)

NMO Correction

DMO Correction

CMP stack


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Migration

Processing Sequence

Reformat

Geometry definition


Amplitude recovery

Noise Attenuation

Deconvolution

CMP gather

Velocity Analysis

Demultiple (marine)

NMO Correction

DMO Correction

CMP stack

Migration

Do the reflections all come

from vertically below?

midpoints


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Pre Stack migration (2D marine)

SHOT SORTED

CMP SORTED

OFFSET SORTED

STACK SORTED

Energy spreading corrections

Low-cut / velocity filtering

Wavelet compression / demultiple

Velocity Analysis

Near/far offset noise removal

Lowcut / highcut / signal enhance

Time variant amplitude balancing

Cosmetic plotting test:bias/gain

Data re-ordering

Define positions and relationships

Removing multiples

Possible additional velocity AnalysisSumming traces within a cmp

Remove source wavelet from data

Field data in

Mute

Comp. Migr. Vels

Migration

Stack

Amplitude scaling

Filtering

Final products

Amplitude recovery

Noise rejection

Deconvolution

CMP gather

Geometry

Demultiple

Signature Decon.

P i S (3D i P t


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Processing Sequence (3D marine - Post

Stack Time Migration)

Amplitude recovery

Noise rejection

Deconvolution

NMO correction

Apply automatic f ield edits

QC navigation data and select

binning strategy

2:1 data reduction

Temporal resample

Initial velocity field

DMO on velocity lines

Nav./seismic merge

3D DMO & Stack

Migration

Demultiple

Time variant filtering

Time variant scaling

f ina l products

QC shot data

As early as possible!

For Shallow water.

For Depth Water we use INVQ or nothing

Signature Decon.

Optional

Field data QC & edit

Second velocity field

Optional

Processing Sequence (3D marine


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Processing Sequence (3D marine -

Pre Stack Time Migration)

Kirchhoff Migration

Amplitude recovery

Noise rejection

Deconvolution

Apply automatic fi eld edits

QC navigation data and select

binning strategy

2:1 data reduction

Temporal resample

Final Mig velocity analysis

Nav./seismic merge

Final Stacking Vel. Analysis

Demultiple

Time variant filtering

Time variant scaling

QC shot data

As early as possible!

Pre Stack Migration

For Shallow water.

For Depth Water we use INVQ or nothin g

Signature Decon.

Optional

Migration Vel Lines


Stacking

f ina l products

Field data QC & edit

P i S (2D l d)


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Processing Sequence (2D land)Basic Processes

Field data in

Geometry

Amplitude recovery

Noise rejection

Deconvolution

CMP gather

Mute

NMO correction

2D DMO & Stack

Migration

Amplitude scaling

Filtering

Final products

Residual statics

Field statics

loop


2D DMOFinal velocity field


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Summary

Virtually all processing projects will require the following:

Accurate locating of shots and receivers and their relationship

Time-correction to a known datum (land, shallow water, transition zone)

Amplitude recovery

Noise attenuation

Signal enhancement

Cmp gathering

Demultiple (marine)

Normal move-out correction (including muting any noise introduced)

Residual time-corrections (land data) Correction for smearing within a cmp - dip-moveout correction (for post stack

migration processing)

Data reduction - stacking

Repositioning / imaging - Migration

2 seis processing flow

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