Seismic Surveys

The first step is a seismic survey where sound waves are used to develop an image of subsurface strata and structures — features where hydrocarbons could accumulate and be retained (see figure below). The sound waves are typically generated by airguns with reflections from the underlying rocks recorded by hydrophones towed behind the survey vessel. These reflections are analysed by computer to allow 3D visualisation of the subsurface geology. The possible sources of environmental effects from seismic survey are illustrated in the figure below. Of these, the prime concern is generally regarded as the short and longer term effects of noise on whales, dolphins and other marine mammals.