Fiber-Optic 4C Seabed Cable for 4-D Permanent Reservoir Monitoring

J. Brett Bunn, S. Rune Tenghamn, and Steven J. Maas*
PGS, USA
*[email protected]

We present an optical system that utilizes passive optical telemetry and sensors to replace traditional seismic acquisition hardware that uses conventional sensors and in-sea electronic modules. The optical system eliminates the costly electronics and problems associated with them, providing a more reliable, less expensive, safer system to operate. We then will describe the system construction and compare data quality between the fiber optic and conventional systems. The optical system utilizes Dense Wavelength Division Multiplexing (DWDM) to optically power the sensors; optical interferometers are used to construct sensors. An optoelectronic/acquisition cabinet provides laser source to the optical sensors. The source passes through an interferometer, where outside stresses cause a phase shift in the light passing through the interferometer. The phase information is extracted back in the cabinet to output a signal equivalent to the input stress. Field test of an optical cable was conducted 2006 using a conventional reference cable. The cables were deployed parallel to each other in the Gulf of Mexico. Advances in fiber optic technology provide a system for 4-D reservoir monitoring. A successful demonstration in the Gulf of Mexico shows the optical system meets the requirements permanent reservoir monitoring. Advances in a 3-axis optical accelerometer, have turned this system into a practical tool for 4C permanent reservoir monitoring. We have demonstrated the systems capabilities in deepwater with high channel count over many kilometers while maintaining high dynamic range, low crosstalk and low distortion. The optical system is an excellent fit for and a preferred solution for permanent reservoir monitoring systems.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain