PGS Access Westralia

New insights into the Westralian Superbasin of the Australian North West Shelf geological province.

In 2015, PGS began a large, multi-disciplinary 2D geoscience project with the aim of offering new insights into the Westralian Superbasin of the Australian North West Shelf geological province. The project has employed an integrated approach encompassing a reprocessing initiative, regional 2D seismic interpretation, utilization of gravity and magnetics, and quantitative seismic interpretation to achieve the goal of providing a new regionally consistent framework across the variable velocity regime of the North West Shelf.

Seismic acquisition took place offshore Australia between 2007 and 2010, and was comprised of both PGS GeoStreamer dual-sensor towed streamer acquisition and conventionally acquired long offset data. The PGS Access Westralia study includes a reprocessing initiative on a representative subset of lines spanning 11,776 km and provides a new PreSDM structural framework and Access study (Figure 1). The latest processing techniques including bandwidth optimization, advanced multiple suppression and pre-stack depth migration have been utilized with particular focus on deep structural imaging.

Figure 1: Location map of Access Westralia, with details of open acreage and 2016 proposed acreage release blocks. Location map of Access Westralia, with details of open acreage and 2016 proposed acreage release blocks.

Improved zero phasing and bandwidth optimization of the conventional seismic data has provided a broader range of frequencies across the amplitude spectrum resulting in a superior seismic image.  This in turn makes the Access study ideally suited for both initial geological interpretation and subsequent quantitative interpretation.  A strong focus on well-tie has been maintained, and critical wells with acoustic logs are incorporated in the reprocessing for calibration.

During the seismic data acquisition, PGS also acquired gravity and magnetic data.  This has enabled the Westralia Access study to benefit from a regional geological interpretation of 2D seismic that was completed in conjunction with a gravity and magnetic interpretation project. This has allowed an immediate insight into the nature of the deeper structures that underpin the region, which may otherwise have been inconclusive (Figure 2).

Figure 2: Africa Access exampleFigure 2: Africa Access example

PGS Access is a unique, stand-alone product that delivers multi-basin exploration data with a geoscience interpretation in an easy to use desktop application. The exploration dataset consists of a workstation-ready grid of regional long-offset seismic lines. The seismic lines will have an interpretation of key regional horizons, and be tied to key wells. A rock physics study will be carried out on selected wells, in order to de-risk play fairways and give new insights into the prospectivity and potential of the North West Shelf. The dataset and interpretation are both hosted and delivered within a desktop application which allows analysis as well as exports to other industry software packages.

By using a multi-disciplinary reservoir approach, clients can use PGS Access Westralia to screen multiple basins, delineate regional plays and understand the context of fields and discoveries in Australia’s North West Shelf offshore margins. PGS Access Westralia is designed to offer new insights for new entrants into Australia as well as existing explorers in time for the 2016 Offshore Petroleum Exploration Acreage Release. The PGS Access Westralia project demonstrates the value of this integrated study for extracting maximum information, which will lead to better decision-making as to where to best invest time and resources along the margin and to increase the likelihood of exploration success.