Mechanisms of hydrate blockage in oil-water dispersions based on flow loop experiments

Abstract

Hydrate formation poses a threat to the safety of petroleum transport in flow lines due to the risk of plugging. In this work, conceptual mechanisms of hydrate formation and plugging in oil–water systems are proposed, based on flow loop tests at 30%, 50% and 80% water cut (water fraction). The experiments were conducted with Kerdane oil, water (with 30 g/L of NaCl) and natural gas at 75 bar and 4 °C. The employment of several instruments, such as acoustic emission, permittivity, and flowmeter, to cite a few, allowed identifying the different flow patterns until hydrate blockage and detecting the phase that carries the hydrates. A model based on density measurement is proposed to calculate the fraction of hydrates flowing locally. It was observed that there are local accumulations of most of the hydrates in a small portion of the flowing volume, which, together with deposition, ends up leading to plugging.