Legacy product - no abstract available

Legacy product - no abstract available

Seismic Test Survey conducted by the Bureau of Mineral Resources, Geology andGeophysics (BMR) (now Australian Geological Survey Organisation (AGSO)) during the early part of 1989. The objective of the survey was to test the suitability of the seismicreflection technique for proposed regional deep reflection seismic lines in the Gunnedah Basin and Cobar Basin. The major emphasis of the test survey was to assess the feasibility of acquiring shallow and deep seismic reflections in order to examine various geologicalmodels of bounding faults and basin structure. The survey acquired data from five sites in the Gunnedah Basin and three sites inthe Cobar Basin. The quality of data in the deeper part of the sections, i.e. 6-15 seconds (TWT), varied from very good to excellent. Seismic reflections in the sedimentary part ofthe succession were, in general, very poor, but some surprisingly good seismic reflectionevents were obtained below the Pilliga Sandstone in the Gunnedah Basin. The test survey indicated that the deep seismic reflection technique in theGunnedah Basin and Cobar Basin would provide data that would be of assistance in developing new geological models, and an understanding of fault geometries and basinstructure, and would assist the exploration for mineral and petroleum resources in the future.

The Bureau of Mineral Resources, Geology & Geophysics (BMR) (now Australian Geological Survey Organisation (AGSO)), Department of Primary Industries & Energy, Australian Government, conducted the Bowen Basin Seismic Survey during July to October 1989. The major aim of the seismic survey was to record deep seismic reflection data across the northern part of the Bowen Basin, to test geological (extensional) models for the formation of the Bowen Basin. The locations of the seismic lines were determined in consultation with exploration companies and the Department of Resources Industries (now Dept. of Minerals & Energy),Queensland State Government. The requirement that the seismic lines be targeted andconstrained to follow a proposed geological corridor was a controlling factor in thepositioning of the seismic lines. The deep seismic reflection survey by the BMR recorded 254 km of 8-fold CDPseismic data, along three seismic lines. Line BMR89.B01, 157 km in length, crossed major features including the Comet Ridge, Bowen Basin, Duaringa Basin and Gogango OverfoldedZone. Line BMR89.B02 was recorded as an easterly extension of Line BMR89.B01, positioned further north due to ease of access. Line BMR89.B03 was positioned to providea north-south line crossing inferred transfer faults of the geological corridor followed by LineBMR89.B01. One expanding spread consisting of 9 shots was recorded on Line BMR89.B01centred at SP 2025 with maximum offsets of 25.6 km. Gravity observations were made at 480 m intervals on all seismic lines.

Resources, Geology & Geophysics (now Australian Geological Survey Organisation (AGSO))conducted a seismic reflection, seismic crustal refraction and gravity survey in southeastern Queensland from August to November 1986. The primary objective of the survey was to complete seismic reflection coverage in the Dalby-Toowoomba area between Traverse 14 and Traverse 16 recorded during the BMR S.E. Queensland seismic survey in 1984. Secondary objectives, subject to survey progressincluded recording additional seismic reflection data east of Traverse 16 (1984) over the Beenleigh Block south of Brisbane, and a 100 km of seismic reflection data south of Mitchellover a deep crustal seismic reflection feature delinated on Traverse 14 (1984) centred at SP4030. Overall the survey objectives would allow the completion of a continuous deepcrustal seismic reflection profile of 1110 km length across southern Queensland, the basis of a lithospheric transect study in the southern region of Queensland. The survey obtained a total of 181 km of 6-16 fold CMP seismic reflection data in theBeenleigh, Darling Downs and Mitchell areas, using the Sercel SN368 seismic acquisition system. Both the primary and secondary objectives were achieved, although equipmentfailures were a major problem in causing decreased production rates. Gravity observations were made at 360m intervals along all traverses. The record presents operational information on the seismic reflection survey and preliminary sections of seismic traverses.

This format description is designed to assist users of AGSO digital seismic data. In general the standard descriptions have been adhered to as specified by Barry et. al. (Recommended Standardsfor Digital Tape Formats, Geophysics, vol 40, No 2 (April 1975) pp 344-352). Trace header mnemonics for many of the entries are as per used by CogniSeis in their DISCO software package, others have been defined by AGSO. Variations to the standard trace header descriptions (bytes 1-180) are as follows. TRACED has expanded codes which are applicable to unstacked data eg. reformatted field data. Static corrections and delays are defined to account for the field acquisition system. In addition to the standard entries a number of optional entries are also used. Some of these arecreated by DISCO and others relate to AGSO data acquisition and processing. The most importantof these are SHOT or SPN. Please note that for AGSO data released prior to 1993, a pseudo shot point number was used (SPN) as opposed to processing shot number (SHOT). The SPN was an assigned number generated from the stack data set and usually started at 100. This number has no direct relationship to the original field shot number (FFID) or processing shot number (SHOT) and may be considered to be a re-sequenced CDP. Therefore the first SPN on a line may not occur at fall fold but the first live stack trace. To relate this vintage data to original field data either 141-11) if present, must be used or time values from the headers must be used. Its use was historical and primarily for the purposes of producing shot point maps which could be related to a section. Its use has been discontinued from 01993 and replaced by SHOT which in most cases will be identical to FFID. Exceptions occur when the line has been merged for acquisition or processing reasons and SHOT numbers have been re-sequenced to obtain a continuous numbering sequence. The convention used for the SHOT annotation position is the mid-point of the source and the firstactive channel. Therefore the ship antenna position, which is Rig Seismic's firing navigation referencepoint, is corrected to relate to this point for all final navigation data. Field data polarity is maintained throughout the processing sequence. The convention for AGSOdata is that a compression wave is plotted as negative. Some data sets may include bathymetry and geophysical data such as magnetics and gravity. These are also corrected to the mid-point location.

The Australian Geological Survey Organisation (AGSO) (formerly the Bureau of Mineral Resources, Geology and Geophysics (BMR)) conducted a deep reflection seismicprofiling survey in the onshore portion of the Otway Basin in the southeastern part of South Australia and southwestern part of Victoria, from February to June 1992. The seismic surveyformed part of a National Geoscience Mapping Accord (NGMA) project to study the early development of the Otway Basin. The objective of the seismic survey was to acquire new deep reflection seismic data (20 seconds two way travel time) using explosive seismic energy sources to improve on the knowledge of early sedimentary sequences in the Otway Basin, especially at depths greaterthan 3 km (ie. deeper than 2 seconds on a seismic section). Explosive seismic energy sources were used in an attempt to provide a stronger seismic energy source than the seismic vibratorsources currently used in the region by seismic contractors. Eight seismic lines with a total survey line length of 474 km were planned for the seismic survey, specifically positioned totarget the survey objectives. Positioning of the seismic lines was achieved through consultation with NGMA partners, industry and universities. The seismic survey obtained 461 km of 5 to 10 fold CMP deep reflection seismic dataalong seven of the proposed seismic lines over a 15 week acquisition period. Line 8 was deleted from the program due to Line 2 being extended in length and budgetary constraints.In addition to the seismic survey, gravity observations were made by the Geological Survey of Victoria and AGSO at 300 m intervals along all seismic lines. All seismic lines were alsoflown by the AGSO geophysical aircraft to record aeromagnetic and radiometric data at a flight height of 100 m AGL.

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.

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. This program is part of a wider program that is acquiring a regional grid of deep-seismic data along the length of the North West Shelf. In particular, the program aims to: *Determine the broad regional structural framework of the southern North West Shelf byexamining 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 fieldsand plays, and in particular the structural and depositional effects resulting from reactivation 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 h_Torth Eest Shelf; AGSO Survey 101) 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 recordedand processed; these data frequently show basin structure down to a depth of at least 10 s two-way time (TWT). The second survey, SNOWS-2 (AGSO Survey 110), acquired morethan 2800 km 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 lineswere tied to 21 exploration wells, of which 3 were also tied during SNOWS-I, and again show reflections down to 12 s TWT. The third survey in the program, SNOWS-3 (AGSO Survey 120), took place in July-August 1993, and acquired a total of 4052.5 km of high-quality deep-seismic data along 14 lines, tiedto 6 exploration wells (of which 2 were also tied on SNOWS-2) and Ocean Drilling Program Site 765 in the offshore Canning Basin, northeast extremity of the Carnarvon Basin, andO^Argo Abyssal Plain. SNOWS-3 ties in with the SNOWS-2 survey to the southwest and withthe Browse Basin deep-seismic survey (AGSO Survey 119, acquired in June, 1993) to the northeast. The seismic data were recorded from a 4800 m streamer, configured with 192 x 25 m active groups. The record length was 16 seconds and the sample interval 2 msec. The seismicsource consisted of tuned airgun arrays with a total volume of 49 litres (3000 cu in). Shots were fired every 50 m at an average ship speed of 5 knots, providing 48-fold coverage.Streamer noise levels were low, with the average noise levels on acceptable channels generally being less than 1.5 rnicrobars. Navigation for the survey was provided by two differential Global Positioning Systems (DGPS), using shore reference stations in Dampier and Broome, adjacent to the survey area.Full differential coverage was achieved for all but a few minutes of the survey. Positionalaccuracy is estimated to be probably better than +I- 10 metres. The offshore Canning Basin is a complex amalgam of a WNW-ESE trending EarlyPalaeozoic intra-cratonic basin overlain by a NE-SW trending Late Palaeozoic to Mesozoicpassive margin basin (the Westralian Super-basin)

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