A distributed vibration sensor

A distributed vibration sensor 102 is positioned in a wellbore to measure fluid flow. The sensor comprises an optical fibre positioned in the wellbore. Vibration from fluid flow in the wellbore causes variations in the backscattering of the light from the optical source 150 that occurs in the optical fibre altering the output. The output of the sensor is monitored by the receiver 154 and the processing system 156 to acquire a distribution of vibration along a region of interest in the wellbore. An indication of the effectiveness of a well treatment to stimulate fluid flow in the wellbore may be provided based on the acquired vibration distribution and the process can be adjusted accordingly.