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A rock-physics study and AVO modeling study have been completed to assist in the interpretation of seismic amplitude and AVO anomalies in the Shipwreck Trough of the offshore Otway Basin of southeastern Australia. Elastic log data, core data (both full and sidewall), and associated thin-section analysis of composition and texture were available on several wells, and these data are important in calibrating proposed rock-physics models that suggest that incorporating cement is critical to understanding anomalies in seismic and measured log data. Lithoprobability volumes based on conventional interpretation paradigms, such as low VP/VS values indicating gas presence, that do not incorporate an understanding of rock physics lead to biased interpretations. Ratios in particular can be misleading because there is ambiguity about whether an anomalous ratio is driven by the numerator or denominator. As a classic gas indicator, low VP/VS values are interpreted to be driven by a decrease in VP associated with gas replacing brine in a rock. Using Lamé impedance terms λρ and μρ, however, provides an alternative interpretation template that does not use ratios and can improve insight into rock properties. As in this recent case study, using lambda-mu-rho (LMR) can be an important tool when shear velocity has increased relative to compressional velocity, irrespective of any pore-fluid change. In the reservoir rocks of the Shipwreck Trough, low VP/VS in both gas-saturated and brine-filled sandstone is caused by quartz cement. This presents a substantial challenge to the use of a standard rock-physics template. In LMR space, however, low VP/VS data points clearly are characterized by high shear rigidity — an important point to recognize and incorporate into AVO interpretation workflows.

Coalbed methane (CBM), or coal-seam gas (CSG), is being developed on a basinwide scale primarily as feedstock for three new liquefied natural-gas (LNG) facilities on the east coast of Australia. A recent 3D seismic survey acquired specifically for CSG in the Surat and Bowen basins shows that although structural detail of the reservoir is a valuable tool, deriving other information for reservoir characterization from thinly bedded coals requires a thorough investigation of the effects of high-reflectivity thin beds. Although work continues to progress, the results so far suggest that 3D seismic surveys can provide information for improved reservoir characterization.

A land 3D seismic survey was carried out in the Surat and Bowen Basins with the specific objective of imaging Coal Seam Gas reservoirs. Use of nodal acquisition technology allowed the survey to be ...

SUMMARY A rock physics study and AVO modelling study has been completed to assist in the interpretation of seismic amplitude and AVO anomalies in the Shipwreck Trough of the offshore Otway Basin of southeastern Australia. Elastic log data, core data (both full and sidewall) and associated thin section analysis of composition and texture were available on a number of wells; and these data are important in calibrating proposed rock physics models

This case-study demonstrates seismic processing in the presence of Horizontal Transverse Isotropic (HTI) velocity anisotropy encountered in a low-fold land 3D survey in New Zealand. The HTI velocity anisotropy was unexpected, being suspected only after the initial poor stack response compared to vintage 2D sections in the area, and the sparse 3D design made it difficult to identify. The paper shows how anisotropy was singled out from other possible causes, such as geometry errors. We discuss the key steps of the processing flow incorporated to deal with the HTI anisotropy to attain a high quality final processed volume. In particular we show data examples after the application of azimuthally dependant NMO velocities, along with pre-stack HTI migration. Examples are shown which demonstrate the preservation of the HTI anisotropy before and after 5D trace interpolation. Maps and vertical profiles of 3D attributes are used to demonstrate the magnitude and direction of the HTI velocity field, which varies 5% to 10% between the fast and slow horizontal directions. These observations coincide with the local stress state deduced from borehole break-out studies. We conclude that the fast velocity direction corresponds to the present maximum horizontal stress direction. Finally the paper summarises the implications for processing wide azimuth 3D data in this area and suggests improvements for future 3D survey design. This paper was originally published in the Proceedings of the 23rd International Geophysical Conference and Exhibition, which was held from 11–14 August 2013 in Melbourne, Australia.

The Speculant 3D Transition Zone (3DTZ) Seismic Survey was acquired by Origin Energy in the Otway Basin, approximately 30km east of Warrnambool, Victoria during November and December 2010. The objective of the survey was to fill a data gap between an existing Marine 3D Seismic Survey (3DMSS) and Land 3DSS, with the target located offshore in the shallow waters of the coastal zone. Although the survey covered a small surface area, the coastal location combined with the economic and environmental significance of the region dictated numerous exclusion zones. To achieve coverage of the target under these exclusion zones, the survey was designed to simultaneously use two independent recording systems; a cable free system on land and an Ocean Bottom Cable (OBC) system offshore, two different sources (GI air gun offshore and Vibroseis on land) and three different receiver types. The final survey design was an orthogonal geometry with a high density of marine shots and a high density of land receivers, with large holes due to access restrictions. The field data were a collection of six different source - receiver combinations, each with unique noise characteristics and statics, covering separate but overlapping CMP?s. Combining these disparate data sets was the key challenge of the processing. The lessons learnt during planning, acquisition and processing are shared in this paper along with examples of the effect that survey design, field conditions and equipment use and limitations can have on field records and processed data.

Peroxisome proliferator-activated receptor γ (PPARγ) agonists have been shown to have anti-proliferative, anti-angiogenic, and proapoptotic effects, leading to interest in their use as cancer therapeutics. Pioglitazone, a U.S. Food and Drug Administration-approved type II diabetes medication and PPARγ agonist, may have a role in adjuvant head-and-neck squamous cell carcinoma treatment or prevention. Therefore, the purpose of this study was: 1) to treat oral cavity cancer cells with the PPARγ activator, pioglitazone, to analyze gene expression changes; and 2) to compare those changes with our preexisting genomic data for development of hypothesis-driven additional basic and clinical studies.Prospective in vitro.We utilized microarray technology, as well as OCPlus (Bioconductor open source software) and Ingenuity Pathway Analysis (Qiagen, Redwood City, CA), to analyze differential gene expression in tumor and pioglitazone-treated tumor cells on a genome-wide level to demonstrate the feasibility of such an approach and determine appropriate sample size for future investigations.We found that approximately 35 samples are required to adequately power future studies. We next discovered that pioglitazone significantly affects Inducible T-Cell Costimulator (iCOS)-Ligand for the T-cell-specific cell surface receptor ICOS (iCOSL) and type II diabetes mellitus pathways as a putative anti-cancer mechanism.Genome-wide analysis is possible for the exploration of differential pathway modulation and rapid hypothesis generation. Both inflammation and type II diabetes pathways were significantly altered and therefore might provide unique hypothesis-driven pharmacodynamic parameters for future in vitro or in vivo studies utilizing thiazolidinediones. These techniques could be applied to microarray or other high throughput data from a variety of hypothesis-generating research scenarios in otolaryngology (e.g., middle ear proteomics, sinus microbiome studies).NA. Laryngoscope, 127:E124-E131, 2017.

The Trefoil prospect is a low relief structural closure in the Bass Basin defined by a vintage 2D seismic grid. For such features, geological uncertainty can be reduced when a number of geophysical tools applied to a seismic data set all independently support a single model of the subsurface. This is particularly relevant for 2D data where the benefit of continuous structural and amplitude coverage of 3D data is not available. Geophysical techniques used to mature this prospect for drilling included pre-stack depth migration (PSDM), horizon-based stacking velocity analysis (HSVA), amplitude versus offset (AVO) analysis/modelling, and frequency attenuation mapping. The application of these methods improved the understanding of the structure compared with previous work based on the same vintage 2D seismic dataset. These analyses consistently support the geological model that Trefoil is a low relief, four-way dip closed anticline, containing several gas columns that may be filled to spill. It is shown that AVO anomalies at prospective levels closely match the final depth closure, as does a frequency attenuation anomaly. The convergence of this information from different methods has reduced the perceived risk to the point where the prospect is viewed as economically viable and is planned for drilling in 3Q 2004.

Elastic synthetic seismograms for a dynamite and Vibroseis source are used to assist the selection of source type for a 3D seismic survey in the Surat Basin. The models are based on well logs and provide key information on seismic source characteristics, which are supported by seismic field data from the study area. The main targets are Permian sands interbedded with laterally extensive coal measures. Survey parameters such as source type, maximum and minimum source-receiver (S/R) offset, and seismic bandwidth are critical in detecting these sands especially if techniques such as AVO are to be used in subsequent data interpretation. The methodology for determining the detectability of the modelled gas sand for each type of source is to subtract the seismogram for a shale model from the seismogram produced when the modelled target sand is present. These difference seismograms computed in t-p space show that with ground roll suppressed the sands can produce more than a 20% change in the modelled seismograms. This figure improves with increasing p value (or equivalent target offset) but is limited by interference from shear waves especially for a Vibroseis source. RMS amplitude attributes (within a window) are used to quantify this change. In the study area it is shown that when compared to a buried (25m) dynamite source, Vibroseis sources produce significantly larger amounts of ground roll on the near traces (offsets 1.4km). Furthermore, because the very strong near-normal incidence reflections from coal measures decay rapidly with offset, target sand detectability tends to increase significantly for larger offsets for both source types. For dynamite sources, detectability is relatively high for source-receiver offsets greater than about 1km, out to at least 2km. Some deficiencies of the Vibroseis source may be reduced by careful noise filtering, however the lower sample density for most 3D surveys (compared to 2D) means that such filtering techniques may be less effective. The study highlights the benefits of seismic source modelling to assist survey design.

A comparison of recently acquired seismic data in the Bowen Basin has highlighted inherent differences in signal content between dynamite and Vibroseis sources. This work was undertaken to assist selection of the source for proposed 2D and 3D seismic surveys in the Bowen Basin where recent drilling successes have revived interest in the hydrocarbon potential of the Permian sequence. Although comparisons between dynamite and Vibroseis sources have been made previously, the topic remains relevant because of developments in acquisition technology, the use of seismic source modelling and the area-dependency of seismic data quality. The motivation for acquisition of further 2D and 3D seismic data in the Surat-Bowen Basin are petroleum discoveries in the Permian Tinowon Sandstone along the western flank of the Taroom Trough at Myall Creek, Churchie, Overston and Waggamba. Variable reservoir quality and extent make identification of Tinowon sands difficult and good quality, high resolution data are essential for exploration and development mapping of the prospective reservoir units. For this study, a pair of overlapping 2D seismic lines was selected, one recorded with a Vibroseis source in 1996 and the other with dynamite in 2000. Care was taken to select two modern lines with acquisition parameters that would minimise the attenuation of frequencies in the higher end of the signal spectrum, thus providing input data sets that would result in a valid Vibroseis-dynamite comparison. Data processing was closely monitored to determine the effects of specific algorithms on signal content. Dynamite proved to have the greatest resolution in the Tinowon zone of interest, that is, around 1400 ms. Indeed, inspection of the signal spectra and particularly the bandpass filter panels on raw field records clearly showed that dynamite data contained higher frequencies and exhibited increased resolution relative to the Vibroseis data in the study area. Bandpass filtering is an effective means of evaluating seismic source characteristics. Predictably, results showed that resolution of the dynamite and Vibroseis data converged with depth due to the natural frequency filter effect of the earth. Synthetic data produced from wavelets matching the Vibroseis and dynamite data demonstrated that the improved resolution expected from the dynamite source would improve imaging of the Permian section. Based on the results of this trial and other modelling, Origin Energy selected a dynamite source for their Myall Creek 3D survey. Mosaic Oil selected dynamite for both their 2003 2D and their 2004 3D seismic survey.

A new technique of amplitude versus azimuth (AVAZ) seismic inversion in horizontally transverse isotropic (HTI) media is presented. AVAZ is an effective method of characterising anisotropic variation within individual reflectors as well as characterising fractures. The compressional wave reflectivity equation in HTI media has been reformulated into a parabolic form that allows for fast and efficient inversion. The isotropic component of the azimuthal reflectivity has been separated precisely from the anisotropic component and the anisotropic component has been decoupled exactly into its constituent elliptic and anelliptic components. The exact isotropic, elliptic and anelliptic amplitude versus offset (AVO) gradient equations in HTI media are presented herein and the amount of error associated with previous approximations is also defined under the assumption of weak anisotropy. A method of calculating Thomsen’s weak anisotropy parameters using these AVO gradient terms is then outlined. Compared with the elliptic method, there is reduced error incorporated in the new AVAZ method and the error relationships of this method are compared with the Fourier method. Data from an open file 3D wide azimuth seismic survey in the Surat Basin were inverted to demonstrate the effectiveness of the techniques which are presented herein. Seismic amplitudes from six azimuthal stacks were extracted over two horizons and inverted around a well where full-wave sonic and density logs were acquired. For both horizons, the error between the inverted anisotropy parameters from seismic and the inverted anisotropy parameters from wire line logs were found to be less than 5% for both horizons.

This case study compares three methods of deriving velocity information from seismic data for the purposes of depth conversion. Horizon stacking velocity analysis (HSVA) and Interval velocity analysis (IVA) have been used to derive average and interval velocity data over the Yolla structure in the Bass Basin, approximately 120km north of Tasmania. The resultant velocity maps are compared with those derived from (more commonly used) vertical function stacking velocities generated during processing. As HSVA and IVA are both horizon-based approaches to velocity picking, lateral velocity trends can be more readily identified and interpreted to be consistent with the geological structure, than regular stacking velocities. A velocity gradient between the 2 wells in the survey area, is known to exist from check-shot data. This gradient is shown to be more accurately determined from the horizon velocity analysis than from the stacking velocity vertical functions. This supports the conclusion that HSVA and IVA (in this case, and perhaps in general), are a more accurate source of velocity control for depth conversion than more routinely used regular stacking velocities. In this example, the relative accuracy of HSVA and IVA velocities is shown to be within 10m/s of check-shot data, compared to several tens of m/s for velocity derived from stacking velocity vertical functions.

Petroleum exploration of the Robe Trough (RT) region of South Australia (Figure 1) has been conducted sporadically and with no commercial success since the first well, Robe 1, was drilled in 1915. Until recently, the onshore area has been regarded as having little prospectivity with exploration concentrated on the edge of the trough. However, as a consequence of recent efforts, the onshore RT is viewed with significantly higher prospectivity, particularly the central region, and underwent a key test with the drilling of the Nunga Mia 1 well in late 1996.

Reflection tomography and interval velocity analysis (IVA) is applied to a 2D seismic line in the Surat Basin -an area where the primary goal is achieving reliable depth conversion of low relief structures, in the presence of near surface velocity anomalies and subtle lateral velocity gradients. The technique, using commercially available velocity analysis and Pre-Stack-Depth-Migration (PSDM) software, represents a potential solution to problems which have challenged previous workers. We demonstrate reflection tomography can resolve shallow velocity anomalies by using as input the moveout errors of deeper horizons from an initial pass of PSDM. Significantly, reflection energy from the near-surface layer is not required to resolve its velocity. When the shallow velocity model is determined, the interval velocity analysis of subsequent layers becomes stable and a more refined velocity model may be constructed. Several iterations of PSDM and reflection tomography are generally required before running a final pass of PSDM. The example seismic line contains three wells which are used to judge the quality of the final depth migration. The results demonstrate that it is possible to extract accurate lateral velocity information inherent in high fold CMP gathers from land data containing shallow velocity anomalies or residual static errors. A lateral velocity gradient causing an apparent pull up of 26 metres between Wells B and C is successfully resolved. The example demonstrates the predicted formation tops of Well C would have been accurate to around +/? 5m if reflection tomography and interval velocity analysis had been applied in place of a regional velocity function derived from nearby well data.

A rock physics study has been completed to assist in the interpretation of seismic amplitude and AVO anomalies in the Shipwreck Trough of the offshore Otway Basin of southeastern Australia. Elastic log data were available from a number of wells in addition to core (both full and sidewall) and associated thin section analyses of composition and texture. The core data are critical in calibrating proposed rock physics models that suggest incorporating cement is critical to understanding anomalies in seismic inversion volumes and measured log data.

Summary A case study is presented which applies interval velocity analysis and reflection tomography to real 2D land seismic data in an area where the primary problem is optimizing the depth conversion of low relief time structures in the presence of subtle lateral velocity gradients. The technique utilizes commercially available velocity analysis and Pre Stack Depth Migration (PSDM) software. The example demonstrates that reflection tomography can resolve shallow velocity anomalies that can not be resolved by either stacking velocity analysis or interval velocity analysis. In the case presented here velocity problems were resolved by using as input for tomography the moveout errors of deeper horizons obtained from an initial pass of PSDM. Once the shallow velocity model was resolved, the interval velocity analysis of subsequent layers became stable and a more refined velocity model was constructed. After a number of iterations of PSDM and reflection tomography, a final 2D velocity model was derived. The chosen seismic line contains three wells which were used to judge the quality of the final depth migration. The structural framework of the Surat Basin is controlled by the configuration of the underlying Bowen Basin which underwent a period of significant compression, uplift and erosion during the Late Triassic. Subsequent periods of reactivation during the Late Jurassic, Late Cretaceous and, ultimately, the Tertiary have accentuated pre-existing structures. Traps are typically low relief anticlines, often associated with Triassic faulting, with structural dips of 0 to 10 degrees. Seismic imaging of the major reflectors is generally good to excellent, however subtle lateral velocity gradients introduce time-depth discrepancies that have led to the drilling of time highs which are not valid depth closures. Presumably also, depth closures exist in these basins that have no expression in time. During field development velocity gradients commonly cause problems for depth prediction especially when addressing attic reserves. The primary cause of the time-depth discrepancy appears to be two-fold: • A thick weathered layer introduces shallow lateral velocity gradients that are at best imperfectly estimated by datum static calculations (usually refraction statics tied to uphole surveys). • Subtle velocity gradients within deeper layers generally go undetected because they are masked by the shallow anomalies which perturb the deeper stacking velocities. Caxton 1(Well C), located on the southern extension of the greater Kincora structure, was drilled in 1995. The objective of the well was to test a fluvial channel directly below marker H4 on the seismic section. The well was located on a time high that was mapped on an old line. Depth conversion of the target horizon (H4) was effected by using an average velocity profile derived from nearby wells. In the absence of any anomalous average velocity trends, the resultant depth high was coincident with the time high and a fault-independent anticlinal closure of approximately 19 metres relief was mapped. Caxton 1 intersected the target 22.7 metres low to prognosis, but addressed significant reserves of stratigraphically trapped gas outside conventional closure. The result at Caxton 1 pointed to the likely existence of statics problems and/or a significant velocity variations. Horizon Stacking Velocity Analyses (HSVAs) were computed for horizons H-1 to H-4. These analyses exhibited oscillatory profiles which became more pronounced in successive layers. This is a common feature of stacking velocity profiles in the Surat Basin and the Eromanga Basin of central Australia. It is the reason why stacking velocities are not normally used for depth conversion; they vary much more widely than the well control demonstrates.

The Speculant 3D Transition Zone (TZ) Seismic Survey was acquired by Origin Energy in the Otway Basin, about 30 km east of Warrnambool, Victoria, during November and December 2010. The objective of the survey was to fill a data gap between existing marine and land 3D seismic surveys. Although the survey covered a small surface area, it included part of the Bay of Islands Coastal Park, dairy farms, southern rock lobster fishing grounds and the migration route for the Southern Right Whale. Numerous exclusion zones were required to address a variety of stakeholder concerns, avoid environmentally sensitive areas, combat a physical landscape dominated by 60 m sea cliffs and the large Southern Ocean surf. These access restrictions required the innovative use of modern seismic technology to enable a survey that could simultaneously record onshore and offshore without a physical connection between recording systems. On land a GSR cable-free recording system was used for the first time in Australia, eliminating the need for any line preparation or vegetation clearing. Offshore an ocean bottom cable system was used. The survey employed smaller sources than traditionally used in the region. A 900 in3 generator–injector airgun array was used offshore while a single Vibroseis unit was used on land. This paper shares the lessons learnt during the planning, approval and acquisition of the Speculant Seismic Survey with the steps taken to reduce the operation’s footprint while maintaining data quality.

The Halladale and Black Watch fields are adjacent fault-dependent gas accumulations at the Turonian Waarre Formation level situated in the eastern Otway Basin, about 4–5 km from shore in VIC/RL2(v). The two fields were first identified in 2002 when anomalous seismic amplitudes were observed on the tail-ends of several 90s-vintage 2D lines that extended into what was then vacant acreage. After being awarded the block as VIC/P37(v) Origin Energy Limited and its joint venture (JV) partner, Woodside Energy Limited, acquired a 211 km2 full-fold 3D seismic survey over the anomalous amplitudes in late 2003. Subsequent analysis of the seismic volume revealed two tilted fault blocks with strong amplitude variation with offset (AVO) anomalies in the Waarre A and Waarre C units that conformed to structure and appeared to shut off at the same depth. A similar AVO anomaly was also observed in the overlying Santonian Nullawarre Formation, raising the possibility that Halladale and/or Black Watch had leaked or were leaking. In early 2005, the VIC/P37(v) JV drilled two exploration wells targetting the key Waarre C reservoir on the eastern flank of Halladale and eastern crest of Black Watch. Both wells encountered live gas columns in the Waarre C but no GWCs were observed on logs and wireline pressure data indicated the two fields were not in pressure communication. A third well was then drilled down-dip of the Waarre C AVO shut off on the Halladale fault block to obtain a water gradient from the Waarre C. This well proved invaluable in determining the height of the gas columns in the Waarre C at both fields as it showed the gas-water contacts (GWCs) at Halladale (1,760 mSS) and Black Watch (1,770 mSS) were shallow to their respective AVO shut offs by about 20 m and 10 m respectively. Subsequent analysis of shear wave sonic data from the third well indicated there is a 17 m residual gas column at the base of the Halladale Field. This suggests Halladale either leaked slightly at some time in the past or is still leaking. A similar scenario may also occur at Black Watch. Given the close proximity of the two fields to the coast, development scenarios from onshore are now being considered.