Abstract: Methods, systems, and techniques for determining whether an acoustic event has occurred along a fluid conduit having acoustic sensors positioned therealong. The method uses a processor to, for each of the sensors, determine a predicted acoustic signal using one or more past acoustic signals measured prior to measuring a measured acoustic signal using the sensor; determine a prediction error between the measured acoustic signal and the predicted acoustic signal; from the prediction error, determine a power estimate of an acoustic source located along a longitudinal segment of the fluid conduit overlapping the sensor; and determine whether the power estimate of the acoustic source exceeds an event threshold for the sensor. When the power estimate of at least one of the acoustic sources exceeds the event threshold, the processor attributes the acoustic event to one of the sensors for which the power estimate of the acoustic source exceeds the event threshold.

Abstract: Sensor shaped to have a frequency response that has less spectral fading than a sensor with a rectangular wrapping pattern, and methods for making such sensors, are disclosed. One such method includes selecting a wrapping pattern comprising multiple layers in which a top layer has a different length than a bottom layer and where the bottom layer is adjacent a mandrel. The method further includes wrapping optical fiber around the mandrel according to the wrapping pattern.

Abstract: Methods and systems for estimating a distance between an acoustic sensor and an acoustic reflector in a conduit are disclosed. One such method includes using the acoustic sensor to measure a combined acoustic signal that comprises an originating acoustic signal propagating along the conduit and an echo signal. The echo signal is generated by the originating acoustic signal reflecting off the acoustic reflector after propagating past the acoustic sensor. A frequency domain representation of the combined acoustic signal is determined and the echo signal is identified by identifying in the frequency domain representation periodic oscillations having a peak-to-peak difference between 0.75 Hz and 1500 Hz. The distance between the acoustic sensor and the acoustic reflector is determined from the velocity of the echo signal and a time required for the echo signal to propagate between the acoustic sensor and the acoustic reflector.

Abstract: Sensor shaped to have a frequency response that has less spectral fading than a sensor with a rectangular wrapping pattern, and methods for making such sensors, are disclosed. One such method includes selecting a wrapping pattern comprising multiple layers in which a top layer has a different length than a bottom layer and where the bottom layer is adjacent a mandrel. The method further includes wrapping optical fiber around the mandrel according to the wrapping pattern.