Recording noise ‐ Estimating shear‐wave velocities: Feasibility of offshore ambient‐noise surface‐wave tomography (answt) on a reservoir scale

Abstract

Ambient noise recorded by broad‐band ocean‐bottom seismometers (BOBS) above an oil and gas field on 126 locations was analyzed to evaluate the feasibility of an ambient‐noise surface‐wave tomography (ANSWT). The ANSWT is a recently developed method to estimate shear‐wave velocities and structural information from low frequency ambient‐noise records without using an active seismic source. It provides a relative low spatial resolution compared to active seismic data, but may result in a better resolution than gravimetric or magnetic methods. In contrast to applications done by global seismologists, who use continuous recordings over months or years and frequencies mostly below 0.1 Hz, we show that utilizing frequencies between 0.1 and 1 Hz and several hours or a few days of recording can be fully sufficient in a marine environment. This allows for much faster data acquisitions and consequently reduced survey costs. First results show that penetrations of a few kilometers with a lateral resolution of several hundred meters can be achieved, and this despite an inconvenient acquisition geometry in our case.