f 3D Concentric circle survey - The art of going in circles

Exploration for hydrocarbons in the North Sea has been successful for targets below Zechstein salt since the very first few Wells were drilled in the Southern North Sea in the mid -1960's (as described by Brennand & van Hoorn, 1984). Exploration targets above the same salt layers has also been successful. However, exploration in the UK sector of the North Sea has not been as successful for targets which are immediately adjacent to Zechstein salt. It is only within the recent past that seismic acquisition and imaging techniques have advanced to the stage that more wells have been successfully drilled (Rockliffe et al, 1992) . The most critical of these techniques has been the 3D survey. This paper will describe the acquisition of a 3D survey over a salt diapir and it will explain why the concentric circle* method was chosen over the more conventional linear technique. This was the first concentric circle survey to be acquired in Europe.