Field test of a permanent in-well fiber-optic seismic system

A deviated borehole was drilled and completed to test systems for deployment of permanent in-well three-component fiber-optic seismic sensors. Two systems were developed and tested for deployment of these sensors. The first system involved using a passive mandrel device to enable coupling of the sensors simply using the weight of the tubing. The second system involved use of an active mandrel that incorporates a spring-loaded pad device to isolate the sensor from the tubing vibration. In addition, reference wireline vertical-seismic-profile data were acquired both in the empty cased borehole and through the tubing at the same location as the fiber optic sensor. Analysis of the data showed that best results were obtained using the active design. Tubing-related resonances were noted on data acquired using the passive design, whereas the active design did a good job of discriminating among these undesirable signals.