f Efficient optical architectures for seismic reservoir monitoring

Fibre-optic seismic sensor systems are gaining increased interest in the context of field-wide permanent seismic reservoir monitoring. This interest stems from the expectation of improved reliability and lower through life cost compared to electronic component systems. Meeting these expectations for high channel count (>10 000 channels) is critically dependent on the optical architecture employed since this dictates requirements on total fibre and optical component count. A particularly attractive optical architecture using Time and Dense Wavelength Division Multiplexing is described. Examples of the implementation of this architecture in a field test of a 4C seismic optical sensor array are presented. A system noise floor below -140dB g/rt Hz, maximum signal level of greater than 0.9g in the seismic band and sensor to sensor cross talk better than -70dB were achieved confirming the viability of this approach for optical seismic sensing.