Environmental and operational challenges of a seismic survey on and around the Muiron Islands, Western Australia

Abstract

In early 1990, the EP 342 and TP/9 joint venture conducted a seismic survey on and around the Muiron Islands in the Carnarvon Basin. Its objective was to infill the gap in existing marine seismic data coverage resulting from the presence of the islands, which are believed to overlie a prospective trend. Work on the Muiron Islands was done in conjunction with a shallow-water marine seismic survey conducted over the remainder of the permit areas. Because the Muiron Islands are a nature reserve and a significant nesting site for Wedge-tailed Shearwaters and turtles, environmental assessment of the project was required. Approval to conduct the survey was subject to stringent conditions, including: the avoidance of Shearwater nesting areas, prohibition of the use of vehicles and the clearing of vegetation, prohibition of camping on the islands, and a requirement to use environmental consultants to monitor the survey. A fully portable operation was conducted on the islands. A recording spread was laid across the islands and extended into the surrounding waters to record shots fired both onshore in drilled or augered shotholes and offshore from the seismic vessel. On the more protected eastern side of the islands a bay cable transition zone spread was extended from the islands to provide a tie with the marine data. However the exposed western side generally proved too rough for the bay cable operation, and a shallow-draft seismic vessel was used in 'rollout mode' to obtain a tie between the onshore and offshore data. The geophysical objectives of the survey were achieved with negligible impact on the environment. There was no known mortality to wildlife and only minor and impermanent disturbance to vegetation.