Shagapov V.Sh., Galiakbarova E.V., Khakimova Z.R.
To the theory of determining the location of hydrate deposits in gas pipelines
by acoustic sounding. Multiphase Systems. 14 (2019) 3. 157–164 (in Russian).
To the theory of determining the location of
hydrate deposits in gas pipelines by acoustic sounding
∗Mavlutov Institute of Mechanics, UFRC RAS, Ufa
∗∗Ufa State Petroleum Technological University, Ufa
Evolution of pressure perturbations propagating in pipeline filled with
gas-and-drop medium representing “wet”
methane at temperature below dew point and having damaged section, in form of extended narrowing of channel
due to hydrate plug, is investigated. Hydrate formation is due to the presence of water (or its vapours) and gas,
the components of which dissolve in water under certain conditions form a solid phase. Hydrate deposits help to
reduce the cross-country capacity of gas pipelines and therefore their detection is a pressing task. It is proposed to
solve the problem using acoustic methods. For this purpose mathematical model of propagation of acoustic waves
in long-wave range in gas-and-droplet medium is considered. The horizontal pipeline appears semi-pointed, the
solution is sought in the form of a harmonic wave. Wave is one-dimensional, having small amplitude of oscillations.
Based on dispersion equations, dependence of phase velocity and attenuation coefficient on frequency of acoustic
wave disturbance and on volume content of suspended phase (water droplets) are built. In the high frequency region,
the attenuation coefficient increases with the volume content. The formulas for reflection and passage coefficients
are derived taking into account pipeline narrowing due to hydrate deposits. The results of numerical calculations
illustrating the dynamics of pulse signals depending on the thickness of the gas hydrate on the inner wall of the
pipeline are presented. Calculations are based on forward and backward Fourier transformations and the use of
software. It is established that the greater the hydrate deposit on the wall in thickness, the greater the amplitude of
the returned reflected signal.
Problem: Analytical and numerical research of distribution of acoustic signals in the gas pipeline with the damaged area, in the form of hydrate deposit on the wall.
Methods: Acoustic methods and methods of the equations of mathematical physics were applied at the decision.
In a study was determined:
- At propagation of acoustic signal in pipeline with damaged section its attenuation is determined by composition of gas-and-drop mixture.
- The size of a hydrate deposit on the wall of the pipeline influences dynamics of acoustic signals.
- The transmission coefficient and the reflection coefficient depend of the size of the damaged are of the pipeline.
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