Digital Accelerometers – Expectations and Practical Achievements

Abstract

Digital accelerometers, a new generation of seismic sensors, were developed at the very end of 20th century and were intensively tested by seismic contractors and oil-and-gas companies at the dawn of 21st century. These 1C or 3C MEMS-based accelerometers integrated with electronics are to deliver a well-calibrated digital signal. Contrary to arrays of geophones, they must be recorded individually as point receivers. Since noise is only filtered during processing, the interval between point receivers must be reduced to avoid spatial aliasing of the noise and to ensure high fold. The benefits provided by digital sensors are both operational (weight, power consumption, integration with the line…) and geophysical (amplitude & phase response, vector fidelity, tilt detection). Early 2D-3C tests as well as current 3D production surveys, including those performed by the highest channel count crews (35,000+), confirm the benefits of these new sensors: immunity to pick-up noise due to full digital transmission; increase of the frequency bandwidth of the signal and of the associated vertical resolution; well-calibrated amplitudes suitable for AVO and inversion. Case histories are collected to illustrate the improved seismic imaging and reservoir characterization provided by the digital accelerometers.