Marine seismic triple source case studies from the Asia–Pacific region

Abstract

There has been a rapid uptake on the idea of using multiple sources in marine seismic data acquisition because of the additional flexibility the technique offers in survey design based not only on geophysical quality, but also for health, safety and environment (HSE) and efficiency. This paper examines three case studies conducted in Australia and Indonesia covering aspects of the advantages.

An important consideration in survey design is efficiency, and multisource designs improve this by allowing wider spreads to be towed, so more data is acquired per vessel pass. In turn, HSE exposure is decreased by reducing survey times and by reducing the amount of in-sea equipment.

The Trepang Survey carried out for Ophir Energy offshore West Papua was designed for efficiency, but the HSE aspect came to the fore when large amounts of floating debris (several hundred tree trunks) were found in the path of the survey vessel. By reducing the acquisition time, the risk the timber posed was minimised.

The Cygnus survey in the Vulcan sub-basin is an example of where the multisource technique increased quality by improving the cross-line resolution and increasing fold without decreasing efficiency.

Bianchi and Hockey were two surveys in the same area and, because the surveys were small, they were inefficient to acquire because much of the time was spent on line changes. The operator Quadrant used the fact that a triple-source design would allow for symmetrical bins to be acquired and joined the two small surveys together: effectively two sets of line change times were turned into acquisition time.