Importance

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Abstract

The present invention relates to an apparatus for use in geophysical surveying. Geophysical surveying typically involves stimulating an area of interest with a seismic source (204) and detecting the response in a sensor array. The application describes a fiber optic distributed sensing apparatus having a source (112) of electromagnetic radiation for repeatedly launching interrogating electromagnetic radiation into an optic fiber (104) deployed in said of area interest, a sampling detector (116) for sampling radiation back-scattered from the fiber; and a processor (108) arranged to process the back-scattered radiation to provide, for each of a plurality of longitudinal sensing portions of optic fiber, an indication of any incident acoustic signals affecting that sensing portion. The sampling detector is arranged to acquire a plurality of diversity samples for each said longitudinal sensing portion. The processor is configured process the diversity samples in diversity channels to determine a measurement signal indicative of any acoustic disturbance; correlate the measurement signal from each channel with a signal indicative of the seismic stimulus applied; and combine the correlated measurement signals to provide an overall measurement signal for the longitudinal sensing portion. The processor may apply a quality metric to the correlated data before performing the combination based on the quality metric. By correlating the individual diversity channels with the stimulus signal prior to performing the analysis of the measurement signal for a particular longitudinal section of optic fiber, the signal to noise ratio can be improved.

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First Claim