Hydrate Plug Movement by One-Sided Depressurization

Abstract

A new model that accurately predicts hydrate plug displacement during a one-sided depressurization is presented. This model is both simple to handle and rigorous in the physical representation of the phenomenon. It was implemented as a finite volume transient simulator capable of determining the flow field coupled with the plug displacement dynamics after its detachment. It takes into consideration velocity, pressure and temperature profiles across chambers upstream and downstream the plug at each instant of time, as well as pipe deformation due to pressure variations inside the chambers. Typical cases for deep offshore production are analyzed. The influence on the plug displacement of the gas composition, the temperature variation due to the heat loss to the environment and high pressure variation is addressed. Results show that, depending on the conditions, and after performing a careful risk evaluation, it may be safe to remediate hydrate plug by one-sided depressurization in a number of typical situations in offshore production scenario.