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The Joint Development Zone (JDZ) and adjacent areas cruise is part of a program beingundertaken by AGSO, to determine the structural architecture of the northwestern margin ofAustralia and the influence of structuring on the location, migration and trapping ofhydrocarbons in the region. The major objectives of the cruise are: 1) to determine the regional structural framework of the eastern Timor Sea region by examiningthe boundaries between the major structural elements along a series of transects; 2) to provide modern regional seismic tie lines through key wells in the region to facilitateprovince-wide correlations; 3) to determine the deep crustal structure of the Sahul Syncline, Sahul Platform, Timor Troughand Malita Graben; 4) to examine the effects of the deep crustal structure and their various phases of reactivationon the stnitural development of the region. To meet these objectives it is proposed that the R V Rig Seismic collect approximately 2600km of deep crustal (16 sec record length) multichannel seismic and other geophysical data along13 lines in and around the JDZ. The proposed lines tie major wells in the region. Wherepossible the lines are orthogonal to the principal trends in the region. Some strike lines areincluded to assist the regional ties between wells and existing data sets.

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The primary objective of AGSO Survey 116 was the acquisition of high-quality deepseismic data and other geophysical data over the Indonesian - Australian JointDevelopment Zone (JDZ) and adjacent areas of the Timor Sea. The cruise was partof a program being undertaken by AGSO, to determine the structural architecture ofthe north western margin of Australia and the influence of structuring on the location,migration and trapping of hydrocarbons in the region. The survey vessel R.V. Rig Seismic left Darwin on 22 January 1993 but returned toport on 30 January due to equipment problems and poor weather conditions. Theship again departed Darwin on 3 February and began seismic acquisition on 5February. The survey was completed on 7 March and finished in Darwin on 8 March. During the survey, 16 seismic lines were completed for a total of 3595 km at anaverage of 119 km per day. All of the proposed Timor Sea Tie lines were completed,however lines across Zone of Cooperation C of the JDZ and the Timor Trough inIndonesian waters were not collected because an agreement between AGSO andIndonesian authorities had not been finalised. In addition to the proposed program,the survey included 5 lines of the Malita Graben program, totalling 1028 km. TheseN-S lines were shot when marginal weather conditions prevented seismic acquisitionin an E-W direction. The Timor Sea Tie lines were tied to 17 exploration wells. Acquisition within the Joint Development Zone was undertaken on behalf of NOPEC,who have been authorised by the Joint Development Authority to research this area.All seismic lines were collected to specifications agreed upon by NOPEC and AGSO. The seismic data were recorded from a 4800 m streamer, configured with 192 x 25 mactive groups. The record length was 16 seconds, and the sample interval 2 ms.The seismic source consisted of dual sleeve gun arrays with a capacity of 50 litres.Navigation for the survey was provided by differential Global Positioning System(dGPS), using shore reference stations Darwin and Broome. The seismic acquisition system was inoperable during the first week at sea duringwhich time weather conditions also prevented acquisition. After repairs to thesystem, both the seismic and non-seismic acquisition systems ran without majorproblems. Navigational data were of good quality, with differential GPS beingavailable at least 95% of the survey time.

Legacy product - no abstract available

During the period 1991-94 the Australian Geological Survey Organisation (AGSO) participated ina co-operative study of the early development of the Otway Basin as part of a National Geoscience Mapping Accord project. The other partners in the project were the Geological Survey of Victoria(GSV), the Department of Mines and Energy, South Australia (MESA), and the Victorian Institute of Earth and Planetary Sciences (V1EPS) at Monash and La Trobe Universities. As part of the project, four subsurface horizons were mapped at 1:250000 scale across the onshore parts of thebasin using exploration industry and AGSO seismic data. This is the first time such mapping has been undertaken on a basin-wide scale in the Otway Basin. MESA undertook mapping in the SouthAustralian sector of the basin, GSV in the central (western Victorian) part of the basin, and AGSO and V1EPS in the eastern part of the basin. This Record accompanies a folio of nine 1:250000 scale maps compiled by AGSO and V1EPS from the onshore eastern part of the basin centred on the Port Campbell Embayment, Colac Trough andOtway Ranges. Four of these maps are presented as two-way times (milliseconds) to four mega-sequence boundaries together with interpreted structural information. The four mega-sequenceboundaries are, 1) - base Wangerrip Group, 2) - top Eumeralla Formation, 3) - top Crayfish Group, and 4) - top Palaeozoic basement. Also included in this Record are four associated isoehron and seismic line information maps at 1:250 000 scale and geophysical maps (gravity and magnetic data)at 1:250 000 and 1:1000 000 scales. The maps are designed to improve the general uderstanding of subsurface basin geometry as a guide to possible hydrocarbon resources both onshore andoffshore.

In mid-1991, the Bureau of Mineral Resources (BMR; now the Australian Geological Survey Organisation, AGSO) commenced a program of deep-seismic acquisition on the southern North West Shelf with the intention of providing a regional framework data set for explorersin this highly prospective segment of Australia's continental margin. In particular, the program aims to: *Determine the broad regional structural framework of the southern North West Shelf by examining the boundaries between the major structural elements; *Determine the deep crustal structure of the region; *Assess the control of deep structure on the development of the major hydrocarbon fields and plays, and in particular the structural and depositional effects resulting fromreactivation of these structures; and *Acquire a set of high-quality seismic tie lines linking the deeper exploration wells throughout the region, to allow regional seismic correlations. To address these aims, a multi-cruise program was devised during which deep-seismic data are being recorded. The first survey, SNOWS-1 (for Southern North West Shelf; AGSOSurvey 101; Stagg, Brassil, & others,1991) was concentrated in the Barrow and Dampier Sub-basins and inner Exmouth Plateau. 1654 km of good-quality seismic data tied to 20 exploration wells were recorded and processed; these data frequently show basin structuredown to a depth of at least 10 s two-way time (TWT). The second survey, SNOWS-2 (AGSO Survey 110; Stagg & Survey 110 Shipboard Party, 1992), acquired more than 2800km of high-quality deep seismic data along 13 lines in the Beagle, Dampier, and Barrow Sub-basins, and over the full width of the Exmouth Plateau in mid-1992. These lines were tied to21 exploration wells, of which 3 were also tied during SNOWS-I, and again show reflections down to 12 s TWT. In the second half of 1993, the Marine Geosciences and Petroleum Geology Program (MGPG) at AGSO will continue this program with the third survey in the area, to be knownas SNOWS-3. The survey will be concentrated in the offshore Canning Basin, and will tie in with the SNOWS-2 survey to the southwest in the Beagle Sub-basin, and the 1993 Browse Basin survey to the northeast. The survey will tie the principal exploration wells in the regionand is expected to acquire at least 3000 km of data along long regional lines; the program allows for up to 3500 km of data to be recorded. As part of the MGPG program of acquiringdeep crustal transects across the margin adjacent to the North West Shelf, the opportunity will be taken to record at least one margin transect from near the coast out to Ocean DrillingProgram Site 765 on the southeast Argo Abyssal Plain. Recording parameters for the survey will include a 4800 m streamer, configured with 192 x25 m active groups; the record length will be 16 seconds, and the sample interval 2 msec. The seismic source will be provided by tuned airgun arrays of total capacity 49 litres, firedevery 50 metres to give 48-fold CDP coverage. These parameters are the same as were used on the SNOWS-1 and SNOWS-2 surveys. Navigation for the survey will be provided by differential Global Positioning System (DGPS),using shore reference stations in Western Australia. Full differential coverage should beachieved for the entire survey and it is estimated that positional accuracy should be betterthan +/- 10 metres.