Acoustic Reflectometry for Blockage Detection in Pipeline

Flow assurance is an important aspect of offshore, particularly deepwater pipeline design and operation, since one of the critical issues is the eventual initiation and growth of hydrate or paraffin blockages under certain conditions. Ideally, operators would benefit from online information regarding position and extent of an eventual blockage in a pipeline. The aim of this work is to apply acoustic technology to design and make a prototype that can be used in a pipe to efficiently identify and measure blockages. The technique uses a short duration sound pulse that is injected into the pipe. When the acoustic pulse encounters an impedance discontinuity, a portion is reflected back towards the acoustic source and microphones or hydrophones. Analysis of the measured signal reflections can provide valuable data related to location and size of the blockages. An experimental setup with a pipe of 4″ internal diameter and length of 100 m was constructed, and different excitation signals for the impulsive response function measurements were conducted. Microphones and hydrophones measurements were recorded using a fit-for-purpose data acquisition system with sampling rates of up to 1kS/s per channel. The tests were performed in air and water using different sizes of blockages and in different positions in the pipe. In parallel, finite element analyses were performed using the commercial software Abaqus to simulate the same conditions. The experiments were numerically reproduced with good correlation proving the potential of the technique.