Experimental Study on Hydrate Plugging in Natural Gas Gathering and Transportation Pipelines

Abstract

During the development of natural gas, from the wellhead of the gas well to the treatment station, the natural gas is not dehydrated or separated, so it could easily form hydrate in the low temperature season, resulting in hydrate blockage of the pipeline, leading to serious economic losses and even casualties. Therefore, it is of great practical significance to study the tendency of hydrate plugging in natural gas gathering and transportation pipelines. In this paper, a set of indoor experimental apparatus was built to simulate a natural gas gathering and transportation pipeline. By using this experimental apparatus, CO₂ gas was used to replace natural gas to carry out experiments, and the influence of different water content, flow rate, choke and production conditions on the hydrate blockage in the natural gas gathering and transportation pipeline was explored. The experimental results show that when water and CO₂ are injected into the experiment apparatus at the same time, the plugging is expected to occur within 30 min to 1 h, resulting in the increasing pressure drop; slug flow and hydrate plugging are more likely to occur in the experimental pipeline when the water content is larger. When there is choke in the pipeline, blockage is prone to occur at the main choke or diameter reduction. When a blockage occurs somewhere in the pipeline, its high-pressure side is in the temperature and pressure region of hydrate generation, which may develop into a multi-position blockage. When the pressure is maintained in the pipeline and there is free water, when left for 6 h or more, it could form a multi-point blockage, and the blockage location is not limited to the choke position.