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7/18/2019 ProMAX

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Introduction to Marine SeismicProcessing - ProMAX

Andrew Goodliffe

University of Alabama

Socorro, NM, ednesday May !"

7/18/2019 ProMAX


ProMAX #$ercise

•What is ProMAX?

•A software package for processing reflection seismicdata

•Commonly used in the energy industry•Not free!

•here are many other programs that will do the samesort of thing they differ mainly in their user interface"or lack thereof#

•$uns on many fla%ors of &N'X

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%ere did t%e data come from&• A short seismic reflection sur%ey in Papua New (uinea

• )eptem*er +,,,• $-. Maurice /wing +01 km streamer

23 channels

14 m group inter%al

+5,4 inch5 tuned si6 airgun array

14 m shot inter%al 127fold CMPs +104 m apart

• + Arc7second "859 m# grids

• :ownloaded from the &)() )eamless ser%er "http;--seamless0usgs0go%-# and

con%erted to a (M format "NetC:<# grid $e7sampled "using grdfilter # to a 909994 degree grid

• Also a%aila*le from NA)A "ftp;--e9srp9+u0ecs0nasa0go%#

http://seamless.usgs.gov/

http://seamless.usgs.gov/

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oodlar' (asin

•A rift *asin in Papua New

(uinea

•A classic place to study theorogenic rifting to seafloorspreading transition

•he line that we will look atcrosses a large rift *asinclose to the transition toseafloor spreading

•he sur%ey was carried outas part of an =cean :rillingProgram site sur%ey

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)ig% Pressure AirSources* +%e Air Gun

Ready Fire! FiredLower chamber has a top diameter

that's smaller the bottom diameter -air pressure forces the piston down

and sealing the upper, firing

chamber. High pressure air is filling

the firing chamber through the T-

shaped passage, and the firing, or

actuating air passage is blocked

(solid black) by a solenoid ale.

!ull pressure has built up in the

upper chamber. The "olenoid hasbeen triggered, releasing high-

pressure air into the actie air

passage, which is now yellow.

The air fills the area directly

below the piston, oercoming the

sealing effect of the air in the

lower, control chamber. The

piston moes upwards, releasing

the air in the upper chamber intothe water.

# large bubble of compressed air is

e$panding into the surrounding water.

The air in the lower control chamber

has been compressed. The triggered

air, released into the space below the

piston, is fully e$panded, and can now

e$haust at a controlled rate through

the ent ports. #s this takes place, the

piston rapidly but gently moes

downward, re-sealing the chamber, andreadying the sound source for refilling.

< r o m ; h t t p

; - - w w w 0 l d e o 0 c o l u m * i a 0 e d u - r e s - f a c - o m a - s s s

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•Airguns susended fromstowed booms

•Single Air gun note airorts

Air Guns

.t%er source&

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•Summing t%e signal of multile guns creates a more desirablesignal•Note t%e relative scales of t%e left and rig%t lots

+uning An Air Gun Array

< r o m h

t t p ; - - w w w 0 l d e o 0 c o l u m * i a 0 e d u - r e s - f a c - o m a - s s s - t

u n i n g 0 h t m l

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/istening• )ydro%one

Pie0oelectric material

Pressure c%anges in t%e water generate small currents w%ic%are amlified

• Geo%one

Mec%anical

Motion of coil relative to magnet generates a small currentw%ic% is t%en amlified

< r o m > e a r e y ? @ r o o k s ? a n d A i l l ? 1 9 9 1

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)ow is a Marine Seismic 1eflectionSurvey S%ot&

:efinition of shot and common mid7point "CMP# gathers

)hot gather; All the datarecorded on all the channels*y a single shot

CMP gather; A collection oftraces that ha%e *eenrecorded at the same

location0

)hot and CMP gathers are simply different ways of sorting thedata0

What is the natural CMP spacing relati%e to the group inter%al?

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Starting ProMAX

• ype Proma6 on the command line

• )elect the sur%ey

• )elect the line that includes your name

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Anatomy of ProMAXClick on the /W,,+9 area then /W,,+9 Bine =:P++

Bist offlows

operationsthat we willapply to thedata

his area tells you what each of your mouse *uttons will

do ProMAX uses three mouse *uttons

)tatus ofany o*sthat arerunning

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Anatomy of ProMAXClick on 9+ :isplay )hots Bist of

indi%idualprocesses things we cando to the data0<lows are *uiltup of a

seDuence ofprocesses0 Clickon one and itwill appear inthe left7handwindow0 :elete

and processesaccidentallyadded *yclicking ondelete in theleft7hand

windowhis flow reads in the seismicdata and displays it

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Anatomy of ProMAXClick on :isk :ata 'nput with the middle mouse *utton0 his will

parameteriEe the process0 ere we see that we are reading in ++ )hotsw-geom "raw shot file with na%igation added to the headers# sorting thedata *y )ource inde6 num*er "shot num*er# reading in e%ery +9th shot fromshot 599 to the end of the file

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Anatomy of ProMAXClicking on the data file ++ )hots w-geom with the left7hand mouse *utton

"BM@# will take you to a list of data files0 Click on ++ )hots w-geom withthe middle mouse0 he details of the data file are now displayed

We can now see how many traces there are in the file the sample rate "inmilliseconds# how many samples there are per7trace the minimum andma6imum C:P and the minimum and ma6imum shot ")'N #0 Mo%ing yourcursor to the top of the screen will take you *ack to the flow

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2islaying a S%otClicking on /6ecute with the BM@

:irect ray path sound tra%elsdirectly from

the airgun arrayto thehydrophones forms a straightline

$eflected raypath sound*ounces of theseafloor andunderlyinglayers forms a

hyper*ola

Water column noise

$eflected raypath sound*ounces of theseafloor andunderlyinglayers

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ater 3elocityClicking on the Eoom icon0 @y holding down the BM@ and dragging a *o6

Eoon into the area where we see the direct wa%e0 he gradient of the directwa%e gi%es us the water %elocity0 Click on the gradient icon0 @y holding downthe BM@ drag a line that follows the first arri%al of the direct wa%e0 hecorresponding %elocity will *e displayed at the *ottom of the screen

Foom icon(radient

icon

Which channel isnearest to the ship?

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Near-+race PlotWhen we are collecting data we want to see it as Duickly as possi*le oneway of doing this is *y displaying a near7trace plot0 his is simply a displayof the channel nearest to the ship for each shot0 his will gi%e us the firstglimpse of what we are looking at in terms of geology0 (o *ack to the list ofprocesses and click on 91 Near race Plot0 /6ecute the flow0

)eafloor

@asement

(ra*en*ounding faults

Multiple

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Near-+race Plot(o *ack to the flow 91 ! Near race Plot and uncomment Automatic (ainControl *y clicking on it with the right7hand mouse *utton "$M@#0 his willadd gain to the section enhancing the deeper reflectors

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Power Sectrum(o *ack the list of flows0 Click on the flow 95 ! Power )pectrum and

e6ecute it0 his flow is setup to show the freDuency content of e%ery +9th shot0 We use a plot like this to determine characteriEe the range offreDuencies in data and possi*ly identify noise

<reDuency content *ychannel

<reDuency range

Phase

)hot gather

Click on

the arrowto go tothe ne6tshot

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4ilteringWe can use a *andpass filter to remo%e freDuencies *elow and a*o%e a

certain range0 We are now going to test some filter parameters using theprocess 92 7 <ilter

he filter defined inParameter est will remo%e allfreDuencies *elow G E and

a*o%e 39 E0 All freDuencies*etween +9 and H9 E will *ekept0 A ramp is applied tointermediate %alues

he num*er ,,,,, ne6t to

filter %alues indicates that theactual filter %alue comes fromthe Parameter est process

/6ecute the flow

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4iltering<or each shot a filtered and unfiltered "Control copy # %ersion of the data is

displayed0 Ad%ance to the ne6t shot *y clicking on the arrow0•Foom in to look at the data in detail•ry some different filters

1 i NM.

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1emoving NM.he reason for ha%ing so many "12 in this case# traces in a CMP is so that wecan stack "sum# the traces for a gi%en CMP0

•Noise cancels out•$eal signal "geology# is amplified•)ignal to noise ratio increase

•<irst we must remo%e Normal Mo%eout "NM=# the difference in tra%eltime that is the result of %arying ray path lengths

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i l m

a E ? + , 3 ,

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0

2

2

0

2 t V

xt t T

x ≈−=∆

T t

xV

∆

=

02

1emoving NM. in Practice

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1emoving NM. in Practice 3elocity Analysis

< r o m I i

l m a E ? + , 3 ,

(o *ack to the flows list in ProMAXand select 94 ! .elocity Analysis click on /6ecute

Nowadays %elocity analysis iscarried out using sem*lanceplots these show how wellthe data stacks "i0e0 areflector is coherent acrossa stack after NM= isapplied# for a gi%en two7waytra%el time and %elocity

CMP )em*lanceplot

NM= has *eenremo%ed

correctly andthe reflector isnow coherent

3 l i A l i

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3elocity Analysis

)em*lance plot CMP

Click on the Eoom iconand Eoom into thisarea

:ynamic stack

3 l it A l i

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3elocity AnalysisClick onthe pickicon topick%elocity-time pointon thesem*lanceplot

Click on(ather ApplyNM= tosee NM=applied as

you pick

NM=

Add%elocity-timepoints to thesem*lance plot

such that theNM= is remo%edfor the maorreflectors0

•Foom in and out

as necessary

•:o not pick themultiple

•)a%e your picks

St 'i

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Stac'ing(o *ack to the list of flows0•Click on 9G ! )tack

•his flow uses your %elocity picks and other that were picked earlier tostack the data•he traces in each CMP are summed to form one trace

$emo%es someresidual noiseand spikes

Applies a*andpass filterto the data

Applies the NM=

correction usingthe picked%elocities

race mutes toremo%e stretchedtraces and attenuatemultiple

races in eachCMP are stacked

/6ecute the flow this will take some timeJ00

3i St '

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3iew Stac'(o *ack to the list of flows0•Click on 9H ! .iew )tack •/6ecute the flow•Iou will see that the image is now much *etter than our original neartrace plot•Iou can start to see stratigraphy•owe%er the are lots of diffractions and reflectors are not in theircorrect su*surface location we need to migrate

Mi ti

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Migration'n an un7migrated time section reflectors do not represent the truesu*surface geometry0•)ee e6amples *elowJ

< r o m > e a r e y

e t a l 0 ? 1 9 9 1

)eafloor

ime section

ime section

(eologicalCross7section

:ippingreflectors

@ow7tie effect

"A#

"@#

"C#

"A# a syncline on the seafloor isimaged as a K*ow7time section

"@# he addition of diffractions fromthe end of reflectors results in a %erycomple6 time section

"@# A dipping reflector is shallower in

a time section

Mi ti

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Migration(o *ack to the list of flows0•Click on 93 ! Migration

&sing a %elocity model that wasmade earlier we will migrate thedata

here are a num*er of ways ofmigrating the data all aremathematically %ery comple6J0

/6ecute the flow0 his will take some time

When it has finished running Click on 9, ! .iew Migration and e6ecutethe flow

3i Mi ti

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3iew Migration

•Most diffractions ha%e gone•(eology is now gar more e%ident

•$emaining pro*lems; smilesL frowns•)olution; impro%e %elocity modelL more ad%ance processing

•Why is this still not eDui%alent to a geological cross7section?

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