Evolution of acoustic pulses in damaged underground pipelines

The research is of increasing relevance due to the need for recommendations on improving the existing methods for rapid detection of pipeline damage at the early stages of hydrocarbon liquid flow into the ground through the damaged areas. To detect possible pipeline damage that occurs during the transportation of hydrocarbon liquids, a technique of pressure pulse probing in the liquid filling the channel is proposed. A theoretical model of propagation of finite-duration pulses through an underground pipeline with corrosion-rusted damages in the short-wave approximation is developed. Integro-differential equations that take into account the manifestation of viscosity in a liquid in the boundary layer near the inner surface of the pipeline wall are obtained. Dispersion expressions for the distribution of the pulse signal within the corroded area are induced, and the reflection and transmission coefficients are determined based on the boundary conditions for the damage. The dynamics of pulses in the pipeline is studied using the fast Fourier transform. The features of pulse signal dispersion in the area of corrosion depending on the channel radius, soil filtration characteristics, and the amount of damage to the channel wall are revealed. The theoretical calculations show that the “echo” of the signal from the damage is weak, and the modulus of the coefficient of signal reflection from the border of the damaged area is no more than 10% of the scanning pulse signal. Therefore, in order to catch the “echo” of the signal at the early stages of the liquid flow through the corroded section of the pipeline, sufficiently accurate devices are needed to generate a scanning signal of a given duration and amplitude, as well as highly sensitive sensors – signal analyzers. The theoretical results of the research serve as a basis of the patent for the invention.