Effect of the Angular Response of a Fiber-Optic Cable on DAS VSP Recordings in Lateral Wells

The angular response of a fiber-optic cable to incident seismic energy when used with distributed acoustic sensing is well known, but it is difficult to understand its effect on survey design without additional visualization and quantification. We present a simulation demonstrating the effect of the angular amplitude response for lateral wells on both P and S waves. We find that the vertical portion of a moderately deep well has an excellent response to reflection events and a good response for direct waves, which is dependent on the source offset. The horizontal portion of the well has a much weaker response for P waves and an encouraging response for S waves. For a shallow SAGD-type geometry, the diversity of incident angles yields an excellent amplitude response for both the direct and reflected energy for channels that are not directly under the source. This study makes the case for a pre-survey modeling of the effect of the fiber-optic cable amplitude response in order to assist the choice of acquisition parameters.