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BMR RECORD 1991/81

ARAFURA SEA - SEISMIC RECONNAISSANCE WITH GEOCHEMISTRY

SURVEY^94

(PROJECT 121.24)

POST CRUISE REPORT

by

P.NAPIER, A.MOORE and J.BRADSHAW

III I 118 1!1 1 I

@Commonwealth of Australia, 1991

This work is copyright. Apart from any fair dealing for thepurposes of study, research, criticism or review, aspermitted under the Copyright Act, no part may be reproducedby any process without written permission.Inquiries should be directed to the Principal InformationOfficer, Bureau of Mineral Resources, Geology andGeophysics, GPO Box 378, Canberra, ACT, 2601.

ISSN 0811-062XISBN 0 642 16959 4

CONTENTS

INTRODUCTION

GEOLOGICAL SETTING

BRIEF EXPLORATION HISTORY

CRUISE OBJECTIVES

CRUISE DIARY

DIRECT HYDROCARBON DETECTION (DHD)

PRELIMINARY RESULTS

REFERENCES

ILLUSTRATIONS

APPENDICES

1. LINE INFORMATIONa) DETAILED LINE SUMMARY - LINE LISTSb) NAVIGATION WAY POINTSC) SONOBUOY LOGS

2. GEOPHYSICAL EQUIPMENT3. ACQUISITION PARAMETERS4. SCIENCE PERSONNEL

ILLUSTRATIONS

FIGURE 1^

SURVEY LOCATION MAP SHOWING THE OUTLINE OF THEGOULBURN GRABEN AND THE SEISMIC LINES OF SURVEY94

FIGURE 2^STRUCTURAL ELEMENTS MAP OF THE ARAFURA SEAOVERLAIN BY SEISMIC LINES OF SURVEY 94

FIGURE 3^SEISMIC SECTION - SHOWING A PORTION OF LINE 4

FIGURE 4^LINE DRAWING - SHOWING MAJOR STRUCTURAL FEATURESLINE 4

INTRODUCTION

Large areas of the Arafura Sea in Australian waters are virtuallyunknown geologically, with seismic coverage being limited towidely separated traverses, some of which have poor sub-seabedpenetration.It was proposed (Moore et al, 1990) that the Rig Seismic be usedfor one month in early 1990 to carry out reconnaissance of theeastern Arafura Basin. The aims were to investigate thearchitecture of the graben in the central and western ends of thebasin,and to complete the framework of essential reconnaisssancein the sparsely explored and little known eastern portion of thebasin and to sample the seawater for traces of thermogenichydrocarbons, one of the indicators of the generation ofhydrocarbons in sub-seafloor sediments.

The Arafura Basin (Figure 1) is the most extensive of the basinsunderlying the shallow Arafura Sea, and contains sediments ofCambrian to Permo-Triassic age. The west-northwest-trendingGoulburn Graben (new name, see Bradshaw, Nicholl and Bradshaw,1990) within it contains up to 10 kilometres of Palaeozoicsediments. A short exploration phase from 1981 to 1986 led topartial delineation of the basin sediments and structure, whichhas been recently reviewed (Petroconsultants, 1989).The eight exploration wells in the basin (Figure 2) have all beensited on structural targets along the Goulburn Graben (Figure 3),and most of the modern seismic coverage is within it. Themajority of the Cambrian and Permo-Triassic sequences remainuntested and extensive areas of the basin outside the graben arevirtually unexplored.In a current study (Bradshaw, Nicholl and Bradshaw, 1990),extensive redating of the Cambrian to Devonian sequences andanalysis of the regional geology has highlighted several newconcepts. These have implications for the understanding of basinarchitecture and the tectonic history of Northern Australia, andfor petroleum exploration in the area and beyond. Importantfeatures that have been recognised include, late tectonics in theGoulburn Graben and variations in style along its length, LowerPalaeozoic stratigraphic intervals that are of equivalent age tothe oil source rocks in the Amadeus and Canning basins, thecontinuance of the lower Palaeozoic north of the graben to theAustralian/Indonesian border, the existence of the lowerPalaeozoic sequence to the northeast of the Wessel Islands, andthe prevalence of relatively low geothermal gradients, thusraising the petroleum potential of the older sequences.

The cruise has pursued these insights with seismictraverses both across and along the Goulburn Graben to acquiredata on its deeper structure; with tie lines from the grabennorthward toward the Australian/Indonesian border; with inf illseismic in the eastern part of the basin; with a seismic tie nearto Lower Palaeozoic outcrop; and with the acquisition of seismicrefraction, magnetic, gravity and dissolved hydrocarbon gas data.

GEOLOGICAL SETTING

The Arafura Basin is a broad platform sequence situated on thenorthern margin of Australia mostly beneath the shallow waters ofthe Arafura Sea. Structurally it consists of a northern and asouthern platform separated by a major graben. The Cambrian toPermo-Triassic Arafura Basin sequence is unconformably overlainby the mid-Jurassic to Recent Money Shoal Basin sequence and isunderlain by Proterozoic sediments of the McArthur Basin (Figure4). In the Goulburn Graben (formerly called Arafura Graben orMoney Shoal Graben or Pre-Mesozoic Graben) there is a Palaeozoicsequence over 10 km in thickness, whilst on the northern andsouthern platform there are respectively at least 5 and 3 km ofthose sediments preserved.

BRIEF EXPLORATION HISTORY

The existence of a large Palaeozoic basin to the north ofAustralia was suspected for many years from the outcroppingCambrian sequence on Elcho Island (Wade, 1924; Plumb, 1965; Plumbet al., 1976) and aeromagnetic surveys (Balke & Burt, 1976). Oilexploration began in the early 1920s with the drilling of severalshallow holes (<100 m) on Elcho Island in response to bitumenoccurrences (Plumb, 1965). Offshore, Shell drilled Money Shoal 1in 1971, which primarily tested a Mesozoic sequence. Tests of thePalaeozoic sequence of the Arafura Basin occurred between 1983and 1986 with the drilling of Tasman 1, Torres 1, Arafura 1,Kulka 1 and Goulburn 1. All of these wells were sited offshore inthe southern part of the basin along the Goulburn Graben. Therewere oil shows in most wells, and four source rock intervals wereintersected. Arafura 1 was the most encouraging, encountering oilshows over a gross interval of 425 m in the Devonian andOrdovician and recording total organic carbon (TOC) values of upto 8.65% in the Middle Cambrian.

Seismic surveys of regional significance and with good subsurfacepenetration include:Wessel Marine Seismic Survey 1972, shot by Western Geophysicalfor Beaver Exploration, Line identification - WM and W.M81A Seismic Survey 1981, by GSI for Esso, Line identification -M81.Arafura Sea S81 Survey 1981, by GSI for Sion Resources, Lineidentification - S81 AM81 Survey 1981, by GSI for Mincorp, Lineidentification - AM81.DS81 Survey 1981, by Western Geophysical for Diamond Shamrock,Line identification DS-81.DS84 Survey 1984, by Western Geophysical forLine identification DS-84.

Among the more recent seismic surveys in the area are -HA88A Seismic Survey by Halliburton for BHP, Line identificationHA88A,PSLA ID 88/43HA88B Seismic Survey by Halliburton for BHP, Line identificationHA88B,PSLA ID 89/1HA89A and HA89B, 1989, by Halliburton for BHP, Lineidentification HA89A and HA89B,

Diamond Shamrock,

CRUISE OBJECTIVES

The objectives of the cruise were :-*to investigate the nature of the Goulburn Graben by acquiringdeep information about the dip and relationship of thecontrolling faults*to tie the seismic succession in or around the graben to theoutcrop of Cambrian-age rocks on Elcho Island*to investigate the eastward extent of the Goulburn graben*to fill gaps in the seismic coverage of the eastern part ofthe Arafura Basin and to tie it to seismic traverses east ofthe Wessel Rise.*to investigate seismic refraction velocities of sediments, as

an aid to prediction of the age of seismic sequences.*to test the practicability of acquiring near-bottom water

samples for geochemical analysis simultaneously with seismic,bycontinuous sampling about 10 metres from the sea floor*to contribute new data on hydrocarbon occurrence by seekinganomalous concentrations of light hydrocarbons using DirectHydrocarbon Detection (DHD).

CRUISE DIARYINTRODUCTION

The R.V.RIG SEISMIC departed Port Darwin at 1600 Hrs.Saturday, 24th February to commence a 30 day scientific cruise toinvestigate the nature and extent of the sedimentary basinsunderlying the Arafura Sea.

As stated in the pre-cruise report (Moore et al, 1990) theplan was to build on and extend the knowledge gained through oilexploration primarily since the early 1970's.As can be seen fromthe list of objectives, most of the cruise period was to be spentextending the present seismic coverage,both in depth and lateralextent.

Also the cruise was, to the best of our knowledge a worldfirst, in that we successfully collected continuous seafloorwater samples and carried out geochemical analyses,simultaneously with our seismic coverage. The ability to conducta geochemical survey in this way has a number of obviousscientific and cost advantages over running independent surveys,not the least of which is the ability to plan immediate inf illlines in areas where seismic and geochemical anomalies are co-incident. As a result of the operational success of this cruiseusing this technique it should be possible to routinely carry outthis combined type of survey,in any appropriate area in thefuture, using the equipment and facilities available on board theR/V RIG SEISMIC.

In addition to the above techniques, continuous underwaymagnetics and gravity data were recorded and 9 sonobuoys deployedto gather seismic refraction velocities.

OPERATIONAL MODIFICATIONS TO THE ORIGINAL CRUISE PLANIn general all equipment operated to a satisfactory level to

achieve the objectives of the survey, except that some seismiclines (noteably lines K & E, and the eastern half of line J andthe northern half of line D ) had to be deleted from the programbecause of equipment downtime and adverse weather. Some lineswhich were planned in the far northeastern area of the originalseismic grid were abandoned because of long transit times andlines 14,15 & 16 were added to those indicated in the pre-cruisereport, in order to improve our understanding of the easternextension of the Goulburn Graben, and complete an integrated dataset of this area within the time left available to complete thecruise.

DETAILS OF DATA ACQUIREDSeismic, magnetics and gravity were recorded on all lines

shown in the accompanying map, however geochemical sampling wasnot carried out on Line 14 and the northern portion of Line 3

ABBREVIATED DAILY LOG

FEBRUARY 24th Departed Port Darwin for survey area.FEBRUARY 25th Tested DHD equipment and checkedcontinuity,balanced and reconfigured previous 2400m cable.

FEBRUARY 26th Successfully calibrated DHD equipment, added1200m cable to 2400m cable and tested entire 3600m.FEBRUARY 27th^Problems encountered with starboardtowleader, removed and checked. Noisy channels traced.FEBRUARY 28th Attempted first line start, system and tapedrive problems required 2 loops to correct problems.Continual system crashes. May come back and reshoot later.MARCH 1st Completed Line 1 Transit to Line 2 . Replacedbad depth controller on Bird 18 using Zodiac. Gun buoysdetached and had to be retrieved. Commenced Line 2MARCH 2nd. Series of short computer crashes, 2 compressorswith stripped clutches. Completed Line 2.MARCH 3rd Compressors repaired, guns repaired. Refractorvelocity 5600 m/s @ 1.2 secs. TWT . Therefore decided to startshooting Line 3 with single (1600 Cu inch ) array. Guncontroller problems necessitated loop.MARCH 4th^Dual array and 12 second recording begun asapproaching Noorthern fault on edge of Goulburn Graben.Completed Line 3. Transit to Line 4.MARCH 5th Attempted to start Line 4. Repeated GunController problems resulted in no production while probleminvestigated.MARCH 6th 2 active sections replaced, shark bites. Guncontroller back together. Restarted Line 4.MARCH 7th^More Gun Controller problems. Meeting heldand Canberra informed of problems. More work onGun Controller. Restarted Line 4.MARCH 8th^Record length 11 sec. dual array. Loop inmiddle of line tape drive hung. Record lengthreduced to 10 sec @ s.p. 4970. Completed Line 4.MARCH 9th Began Line 5 experiencing strong currents andhigh winds. Acquisition suspended, guns retrievedwith difficulty, 1 buoy lost.MARCH 10th Storm continues, no production. Guns beingrepaired . Heading West back towards start of line 5.MARCH 11th Weather still poor. Cable deployed however.Steaming back to commence shooting 26 naut. miles from S.O.L.MARCH 12th Continued shooting Line 5. High velocityrefractor very shallow. Strong currents against us.Commenced Line 6. High velocity refractor @ 0.46 TWT.Deployed sonobuoy.MARCH 13th^Computer crash, did loop. Cable rising, dataquality deteriorating. Very hard sea floor - audible.Crossed Northern fault of Goulburn Graben.MARCH 14th Completed Line 6. began Line 7 with 8 secrecords. Changed to 12 seconds @ 22 naut. milesfrom S.O.L. Deployed sonobuoy.MARCH 15th cable came to surface just prior to GOULBURN -1Increased speed, reduced record length to 11 sec.Bad navigation satellites, missed well, thereforedid a loop. Japanese fishing vessel crossedastern, dived cable and no damage. Completed line 7Transit to line 8, deployed sonobuoy.MARCH 16th^Began line 8 , had a series of system crashesdid a loop. Deployed sonobuoy 4 naut. miles west

of TORRES-1. Completed line 8. Turned onto line 1AMARCH 17th^Completed line 1A. Turned off to start line 9Had a number system crashes. Sonobuoy deployed.MARCH 18th Compressor stripped another clutch. Completedline 9. Began line 10. Bulk carrier passed astern.Changing water bottom conditions, louder bang.Began line 11.MARCH^19th Completed line 11. Started line 12, 8 secrecords. Sonobuoy deployed, 3000 m/s and 6000 m/srefractors. Completed line 12. Tugger winch cable snapped onretrieval of guns. No injuries All compressors repaired.MARCH 20th Started line 13. Initially 96 ch,48 fold,8 sec. recs, changed to 72 ch, 72 fold, 5 sec. recs @78.23.20MARCH 21st. Completed line 13. Weather had deteriorated.Because of limited time had to abandon lines around WesselIslands and the link to the West.MARCH 22nd^Lost 1/2 of today because of bad weather.The ship has been heading west to complete thegrid at the Eastern edge of the Goulburn Graben. Commencedline 14 in 25 knot winds. Single array 96 ch, 96 fold, 5sec. recs. Sonobuoy deployed.MARCH^23rd^Completed line 14. Commenced line 15.Single array, 72 ch., 72 fold, 5 sec records. System crash -lost 18 shots. Completed line 15. Began line 16MARCH 24th^Completed line 16. Cable retrieved, headedback to Port Darwin.MARCH 25th^Transit to Port Darwin.MARCH 26th^Berthed Darwin 0800 hrs

DIRECT HYDROCARBON DETECTION (DHD)

Direct Hydrocarbon Detection is designed to contribute data onhydrocarbons generated from source rocks, by searching forhydrocarbon vents and seeps from the underlying sediments toseawater. Hydrocarbon vents and seeps produce anomalousconcentrations of light hydrocarbons in seawater with molecularcompositions that are distinctively different from 'background'of biogenically produced hydrocarbons. Furthermore, the molecularcompositions of thermogenic hydrocarbon vents and seeps may beused to infer the 'source' of that seep, i.e., liquids,condensate or dry gas.The method used on the RV 'Rig Seismic' can be summarised asfollows (refer to Figure 6).Seawater is continuously delivered, via a submersible towed pump(the 'fish') into the geochemical laboratory aboard the ship. Aship speed of up to six knots is possible in depthscharacteristic of the continental shelves, but when geochemistryis used simultaneously with seismic reflection profiling aboardRig Seismic the speed is limited by seismic requirements to fourto five knots.The water is continuously degassed in a vacuum chamber and theresulting headspace gas is injected into three gas chromatographswhich sequentially sample the flowing gas stream and measure avariety of light hydrocarbons. Total hydrocarbons are measuredevery thirty seconds. Light hydrocarbons, methane through butaneare measured every two minutes and intermediate hydrocarbons, C5through C8 are measured every 8 minutes.Fish altitude from bottom, depth of the fish in the water,hydrographic data (temperature and salinity) and continuousnavigation are recorded on the hydrocarbon data acquisitioncomputer. All data are recorded and displayed continuously sothat anomalies in the water column can be quickly and easilyrecognised and additional measurements can be made whenappropriate.Samples for isotopic measurements may be taken on the ship whenseeps are detected. These samples are stored for subsequentanalyses in the shore laboratory.The sensitivity of the method is high, allowing detection of 10parts per billion in the stripped headspace sample, correspondingto 200 nanolitres of THC per litre of seawater.At 4 knots, the measurement of THC is made at distances over theseafloor of about 70 m; for methane to butane at distances ofabout 350 m and pentane to octane at about 1400 m.

REFERENCES

BALRE, B., BURT, D., 1976 - Arafura Sea Area. In LESLIE, R.B.,EVANS, H.J., KNIGHT, C.I., (Eds.), Economic Geology of Australiaand Papua New Guinea, 3. Petroleum. Australian Institute ofMining and Metallurgy, Monograph Series 7, 209 - 212.

BRADSHAW,J., NICOLL,R.S.,BRADSHAW,M.T., 1990 - The Cambrian toPermo-Triassic Arafura Basin, Northern Australia. APEAJOURNAL, 30.

MOORE,A., BRADSHAW / J., NAPIER I P., MEGGIE,D. 1990 - Arafura Sea -Seismic Reconnaissance with Geochemistry (Project 121.24) -Research Cruise Proposal. BMR Record 1990/09

PETROCONSULTANTS AUSTRALIA Pty Ltd, 1989 - Arafura Basin.Northern Territory Geological Survey Petroleum Basin Study.

PLUMB, R.A., 1965 - Wessel Islands/Truant Island, N.T. 1:250,000Geological Series. Bureau of Mineral Resources, Australia, Explanatory Notes SC/53-15.

PLUMB, ILA., SHERGOLD, J.H., STEFANSRI, M.Z., 1976 - Significanceof Middle Cambrian trilobites from Elcho Island, NorthernTerritory. Bureau of Mineral Resources, Australia Journal ofAustralian Geology and Geophysics 1(1), 51 -55.

WADE, A., 1924 - Petroleum prospects, Kimberley District ofWestern Australia and Northern Territory. Parliament of theCommonwealth of Australia Report 142.

12/0A/9-2

-0- Dry hole• Oil show

{1> Minor oil indication

G Dead oil

- Fault

Normal fault

^ BMR 1990 multichannel seismic and direct-hydrocarbon-detection lines

^ Limit of structural element (in places faulted)

Goulburn Graben

FIGURE 1^SURVEY LOCATION MAP SHOWING THE OUTLINE OF THE

GOULBURN GRABEN AND THE SEISMIC LINES OF SURVEY94

Proterozoic/Palaeozoictilted fault blocks

Southern boundaryof Arafura Basin— possible detachment

Northern bounding faultof Goulburn Graben

FIGURE 4 LINE DRAWING - SHOWING MAJOR STRUCTURAL FEATURESLINE 4

I II

ARAFURA SEA SURVEY 94^LINELIST

Line: 94/01^ Date: February- March 1990

Start Time: 94.058.1902^Stop Time: 94.059.1714

First SP: 100^ Last SP: 2155

Number of shots: 2055^Approx Line length (km): 75

First Field Tape: 94/001^Last Field Tape: 94/019

Number of Field Tapes: 19^Direction of Shooting: SE

Max recording delay: 0 ms

Near Offset: 184 M^ Far Offset: 3790 M

Group interval: 37.5 M^Cable Active Length: 3600 M

Cable Depth: 10 M^ Source depth: 10 M

Source Energy: 2 x 10 gun arrays, 1800 psi

Number Channels: 96^ Recording Fold: 48

Sample Period: 2 ms^ Record Length: 12 and 8 Sec

Amplifier Gains: 128^Filter Settings: 8 Hz low128 Hz high

Shot Interval: 18.2 or 14.6 Sec^Shot Distance: 37.5 M

Field Tape Density: 6250 bpi^Field Tape Format: SEG-Y (GCR)


Line: 94/01A^ Date: February- March 1990





Number of Field Tapes: 6^Shooting Direction: North West


Near Offset: 189^ Far Offset: 3790










Line: 94/02

Start Time: 94.060.0846

First SP: 100

Number of shots: 4246

First Field Tape: 94/020

Number of Field Tapes: 45


Near Offset: 184

Group interval: 37.5 M

Cable Depth: 10 M

Date: February- March 1990

Stop Time: 94.061.0454

Last SP: 4346

Approx Line length (km): 170

Last Field Tape: 94/064

Shooting Direction: North

Far Offset: 3790

Cable Active Length: 3600 M

Source depth: 10 M







1







Number of Field Tapes: 60^Shooting Direction: South

















Number of Field Tapes: 11^Shooting Direction: North












Line: 94/4A

Start Time: 94.065.1248

First SP: 100





Near Offset: 197 M


Cable Depth: 10 M


Stop Time: 94.067.1020

Last SP: 6260



Shooting Direction: North

Far Offset: 3822 M


Source depth: 10 M




Amplifier Gains: 64^

Filter Settings: 8 Hz low128 Hz high









Number of Field Tapes: 57^Shooting Direction: East








Amplifier Gains: 64^ Filter Settings: 8 Hz low128 Hz high









Number of Field Tapes: 68^Shooting Direction: South








Amplifier Gains: 64^ Filter Settings: 8 Hz low128 Hz high















Number Channels: 96

Sample Period: 2 ms

Amplifier Gains: 64

Shot Interval: 18.2 Sec

Field Tape Density: 6250 bpi

Recording Fold: 48

Record Length: 12 and 8 Sec


Shot Distance: 37.5 M

Field Tape Format: SEG-Y (OCR)















Amplifier Gains: 64 and 128^Filter Settings: 8 Hz low128 Hz high









Number of Field Tapes: 18^Shooting Direction: South East
























Sample Period: 2 ms^ Record Length: 10 Sec


Shot Interval: 16.2 Sec^Shot Distance: 37.5 M














Number Channels: 72

Sample Period: 2 ms

Amplifier Gains: 128



Recording Fold: 72

Record Length: 5 Sec



Field Tape Format: SEG-Y (GCR)


Line: 94/14

Start Time: 94.81.0417

First SP:600

Number of shots:4683




Near Offset: 193m


Cable Depth: 10 M


Stop Time: 94.81.1619

Last SP:5283

Approx Line length (km):88


Shooting Direction: West

Far Offset: 2853m


Source depth: 10 M




Amplifier Gains: 128,128^Filter Settings: 8 Hz low128 Hz high



1


Line: 94/16

Start Time: 94.82.1026

First SP: 5421





Near Offset: 193 M


Cable Depth: 12 M


Stop Time: 94.82.1849

Last SP: 8781



Shooting Direction:West

Far Offset:2853 M


Source depth: 12 M

Source Energy: 1 x 10 gun arrays, 1600 cu.in . 1800 psi

Number Channels: 72

Sample Period: 2 ms

Amplifier Gains: 128,128



Recording Fold: 72





APPENDIX 1

CO-ORDINATES OF SEISMIC LINES - WAY POINTS

LATITUDES (SOUTHERN HEMISPHERE IS NEGATIVE)AND LONGITUDES^(EASTERN^HEMISPHERE IS POSITIVE)in degrees minutes and seconds.

1 1 -095530 13227302 -100342 1323245 KULKA-1 well3 -101612 1324025

2 1 -102538 13304542 -085550 1332900

3 1 -090201 13345162 -102811 1332342 TORRES-1 well3 -105334 1331805

4 1 -104710 13233042 -101612 1324025 MONEY SHOAL-1 well (7 km to east)3 -085727 1330208

5 1 -085856 13259002 -092912 1342500

6 1 -091324 13416162 -095655 13405243 -102703 1340326 ARAFURA-1 well4 -111511 1335120

7 1 -113351 13405312 -104448 1341749 GOULBURN-1 well3 -101701 1342522

8 1 -102703 1340327 ARAFURA-1 well2 -102811 1332342 TORRES-1 well3 -101612 1324026

9 1 -100400 13229232 -100342 1323245 KULKA-1 well3 -100321 13244444 -100730 13309455 -101742 13350196 -101942 1335748

10 1 -102703 1340326 ARAFURA-1 well2 -104448 1341749 GOULBURN-1 well

11 1 -104448 1341749 GOULBURN - 1 well2 -105420 1345500

12 1 -105420 13455002 -113912 1353906 Near Elcho Island

13 1 -115243 13523122 -112638 13554353 -104030 1364018

1

14 1 -104651 13538512 -104800 13504133 -104419 1345115

15 1 -102734 13455192 -105258 1345115

16 1 -104437 13451302 -103616 1342000

2

SONOBUOY LOG

Sonobuoy No.: 94/02^ Seismic Line:94/07

Sonobuoy Model: REF-TEK-2^Receiver Model: Yaesu

Sonobuoy channel: 20^ Seismic Channel: 97

Hydrophone Depth: 60ft.(18.3m)^Duration (Hrs):

Filter : 6 Hz Low - 128 Hz High^Recording Delay: 0 ms

Launched off STB side^ Weather/Sea Conditions: 2

Start Time (GMT): 94.073.0850^Start Water Depth: 45 M

Start Lat: 110 12.855'S^Start Long: 134 ° 10.063'E

Finish Time (GMT): 94.^ Finish Water Depth:^M

Finish Lat/Long:^ Finish Shot No.:

Total Time:^ Total Distance (Km):

Approx Ship Speed: 5 knot^Start Field Tape No:94/335

Stop Field Tape No:94/

Observations: ^

Direct Wave I Wide-angle Reflections I Refractions1

Yes^

1

No

Remarks: Near southern margin of Arafura Basin

SONOBUOY LOG



Sonobuoy channel:^ Seismic Channel: 97





Start Lat: 10 ° 26.978'S^Start Long: 134 ° 05.9'E





Stop Field Tape No:94/

Remarks: 4.5 km West of Arafura-1 well. Ship and source moved off to theWest.

SONOBUOY LOG







Start Time (GMT): 94.075.0252^Start Water Depth: 113M

Start Lat: 10. 026.908'S^Start Long: 133 °19.061'E





Stop Field Tape No:94/404

Remarks: 8.8 km WNW of Torres-1 well

SONOBUOY LOG






Launched off Port side^ Weather/Sea Conditions: 6


Start Lat: 10 °45.475'S^Start Long: 135°36.588'E






Remarks: Farthest east. North of the Graben. Ship and source moved off tothe West. Sea conditions marginal.

APPENDIX 2: List of Geophysical Equipment

Seismic System

Streamer: 3600m Teledyne hydrophone analogue streamer configuredas 96 x 37.5m groups.- 30 hydrophones per 37.5m group- 5V/bar sensitivity- -15 microvolts noise; maximum ambient at 5 knots- 6 Syntron RCL-3 individually adressed cable levellers

Source Array:- 52.4/73.4 litre (3200/4480 cubic inch), 28-elementtuned Texas Instruments air-gun array; 20 elements(3200 cubic inch) equally divided into two stringsin use at any one time.

- Teledyne gun signature phones, gun depth sensors,and I/O SS-8 shot sensors

- 4 x Price A-300 compressors, each rated at 300scfm@ 2000 psi

Recording - BMR designed and built seismic acquisition systembased on Hewlett-Packard minicomputers

- 96 channel digitally controlled preamp/filters- bit accuracy

12 bit floating point with 4 bit dynamicaccuracy15 bit integer card

- 6250 bpi Telex tape drives- data read after write in demultiplexed SEG-Y format- 2 or 4 msec sampling with 96 channels- streamer noise, leakage, and individual group QC- source array timing QC- recording oscillator and 4 seismic monitor QC

Sonobuoys - Ref-Tek-2, deploying one hydrophone to 18.2m depth

Bathymetric System

- Raytheon deep-sea echo-sounder; 2 kW output at 12 kHz- 11^sub-bottom profiler; 2 kW^11^3.5kHz

Gravity Meter

- Bodenseewerk Geosystem KSS - 31 marine gravity meter

Magnetometer

- Geometrics G801/803 proton precession magnetometer

Navigation Systems

GPS System - Magnavox T-Set GPS navigator

Prime Transit System- Magnavox MX1107RS dual channel satellite receiver- Magnavox MX610D dual-axis sonar doppler speed log- Sperry gyro-compass

Secondary Transit System- Magnavox MX1142 single channel satellite receiver- Raytheon DSN450 dual-axis sonar doppler speed log- Robertson gyrocompass

Data Acquisition System

- data acquisition system built around Hewlett-Packard2117 F-Series minicomputer, with tape drives, discdrives, 12" and 36" plotters, line printers andinteractive terminals

Source

Shot Spacing

Shooting Interval

Cable Length

APPENDIX 3

ACQUISITION PARAMETERS

2x1600 cubic inch air-gun arrays1x1600^"^11^It^(lines 13-16)

37.5m (lines 1 - 12)18.75m (lines 13 - 16)

18.2 seconds at 4 knots

^

14.6^"^Ig^5^11

^

9.1^"^" 4^"^(lines 14 - 16)

3600m active; 4200m to tail buoy2660m active (lines 13-16)

37.5m

96 (lines 1 - 12)72 (lines 13 - 16)

approx. 200m

approx. 3800m (lines 1 - 12)2853 (lines 13 - 16)

10 - 12m

48 (lines 1 - 12)72 (lines 13 - 16)

12,10,8 seconds5 seconds (lines 13 - 16)

2 milliseconds

8 Hz Low cut; 128 Hz High cut

Pre-amplifiers 128 Hz. IFP used on all lines

Group Interval

No. of Channels

Near Offset

Far Offset

Cable Depth

Recording Fold

Record Length

Sample Rate

Filter Settings

Amplifier Gain

Field Tape Density 6250 bpi

Tape Format^

SEG Y

APPENDIX 4: Science Personnel

P.NapierA.MooreG. HealE.ChudykG.BernardelP.VujovicJ. KossatzT.McNamaraH. ReynoldsA. WarnesD. HoldwayG. BurrenH. HudsonG. BickfordC. TindallG. SparksmanP. AttenboroughB. DickinsonC. GreenD. SewterC. Dyke

Co-chief scientistCo-chief scientistSystems supervisorSystems specialistSystems specialistScience technicianScience technicianScience technicianScience technicianScience technicianElectronics technicianElectronics technicianElectronics technicianGeology supervisorGeology technicianGeology technicianGeology technicianMechanical technicianMechanical technicianMechanical technicianMechanical technician

SONOBUOY LOG






Launched off Port side^ Weather/Sea Conditions: 3


Start Lat: 10 °05.373'S^Start Long: 132 °56.887'E

Finish Time (GMT): 94.76.1207^Finish Water Depth: 71M

Finish Lat/Long:12 °12.9'S^Finish Shot No.:133°32.0 1 E

Total Time: 8hr37min^ Total Distance (Km): 67

Approx Ship Speed: 4.1 knot^

Start Field Tape No:94/449


Remarks: Probe no.5 went bad after 30 minutes, and no.6 waslaunched to replace it. Probe 6 is located on the upthrown sideof the northern bounding fault of the Goulburn Graben, near thefault, and just to the north of it. The ship and source moved offto the East, parallel to the fault.

SONOBUOY LOG








Start Lat:^ Start Long:

Finish Time (GMT): 94.78.020015^Finish Water Depth: 37 M

Finish Lat/Long:^ No. of shots: 1322


Approx Ship Speed: 4.7 knot^Start Field Tape No:94/525


Remarks: Probe no.7 failed. Probe 8 was launched to replace it.Probe 8 is located near latitude 11 °S, longitude 135 °E. The shipand source moved off to the southeast, toward the outcrop ofCambrian rocks on Elcho Island.







Number of Field Tapes: 51^Shooting Direction: West






Number Channels: 96

Sample Period: 2 ms

Amplifier Gains: 128



Recording Fold: 48

Record Length: 12 and 8 Sec




SONOBUOY LOG



Sonobuoy channel: 10^ Seismic Channel: 97



Launched off PORT/--side^Weather/Sea Conditions: 3


Start Lat: 09 ° 13.87'S^Start long: 134 ° 16.218'E

Finish Time (GMT): 94.071.1800^Finish Water Depth: 90 M



Approx Ship Speed: 4.6 knot^Start Field Tape No:94/260


Observations:^Direct Wave 1 Wide-angle Reflections 1 Refractions

i^ 1Yes^

1^ 1--

No

Remarks: Near Indonesian border. Furthest North probe





Number of shots: 2853^Approx Line length (km): 53.5


Number of Field Tapes: 14^Shooting Direction:North


Near Offset: 193 M^

Far Offset:2853 M

Group interval: 37.5 M^


Cable Depth: 12 M^

Source depth: 12 M

Source Energy: 1 x 10 gun arrays, 1600 cu.in . 1800 psi

Number Channels: 72

Sample Period: 2 ms

Amplifier Gains: 128,128



Recording Fold: 72











Number of Field Tapes: 28^Shooting Direction: South East


Near Offset: 189 M^ Far Offset: 3790




Number Channels: 96

Sample Period: 2 ms

Amplifier Gains: 64



Recording Fold: 48





M ECO 8 AAUA SEA SEISMIC ECOAISSACE WI GEOCEMISY SUEY … · 2020. 6. 16. · hl rv n th h nbr f bv...

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Transcript of M ECO 8 AAUA SEA SEISMIC ECOAISSACE WI GEOCEMISY SUEY … · 2020. 6. 16. · hl rv n th h nbr f bv...