Some Results and Conclusions from Recent Reconnaissance 3-D Seismic Offshore New Zealand

Three dimensional (3-D) seismic surveys became commercially available in the late 1970s and their usefulness and value in field development, particularly offshore, has become widely accepted (Horvarth, 1985; Brown, 1986).

The disadvantage of 3-D surveying is that about ten times as much seismic is needed as is normally acquired in ‘conventional’ 2-D surveys.

In the last few years the concept of reconnaissance or exploration 3-D (Recon 3-D), using a wider line spacing to keep acquisition costs to a minimum, has been proposed as an exploration tool (Einarsson et at., 1987; Rasidi, 1987).

TCPL, as operator for three offshore prospecting licences in the Taranaki Basin (Fig. 1), has recently carried out three Recon 3-D surveys, each addressing a different set of problems and objectives. This paper discusses three topics: the background to each survey, the study carried out to decide on the critical parameter of line spacing, and the preliminary results.

Recon 3-D can be justified if it significantly reduces the risk involved in a drilling venture, and the cost is much less than the cost of a well.