Numerical study on the diffusion process of pinhole leakage of natural gas from underground pipelines to the soil

Abstract

World widely, most natural gas pipelines are directly buried underground. Unfortunately, leakages often occur to the natural gas pipelines because of corrosion, external interference, construction defects, etc. As a result of the gas diffusion and accumulation in the soil or adjacent underground space, the potential explosion risk threatens people's lives and properties in case of a fire. Detailed clarification of the diffusion behavior of leaked natural gas from an underground pipe to the soil is essential to shorten the duration of detecting and locating the leak point. In this work, a numerical method is proposed to investigate the pinhole leakage diffusion characteristics of natural gas in the soil. The variations of the gas concentrations under different leak conditions, as well as the effects of the pinhole size, pinhole location, pipe pressure and soil property on the gas diffusion process, are simulated in detail. The simulation results indicate that the risk radius gradually increase with a declining growth rate. The gas concentration along the pipe length shows Gaussian distribution. Leakage with larger pinhole size and higher pipeline pressure leads to a larger amount of leaked gas, consequently resulting in a larger risk area. While, the pinhole location only influences the gas concentration distribution in the vicinity of the leak point. Moreover, the particle diameter and porosity of the soil directly determine the gas concentration distribution in the diffusion.