Effect of Brine on Hydrate Antiagglomeration

Abstract

Natural gas production poses a risk of flow-line hydrate blockage from coproduced water and hydrate-forming species. Our previous studies have focused on gaining further understanding of hydrate antiagglomerants through systematic experimentation as well as testing of a new biosurfactant. Despite great potential, work on hydrate antiagglomeration is still very limited. This work centers on the effect of NaCl and MgCl2 in mixtures of two vastly different antiagglomerants. We use a model oil, water, and tetrahydrofuran as hydrate-forming species. Results show that both salts—added in sufficient quantities—may result in the agglomeration of hydrates. Our results reveal a nonmonotonic agglomeration behavior at low salt and/or large surfactant concentrations. Specifically, dissolved MgCl2 results in agglomeration more than the dissolved NaCl. Our measurements also show that the quaternary ammonium salt—i.e., quat—is more sensitive to dissolved salt than the nonionic rhamnolipid biosurfactant. In this work we show that the rhamnolipid biosurfactant is effective to a low concentration of 0.05 wt %, yet quat has effectiveness down to 0.01 wt %. The biosurfactant—with less toxicity and higher biodegradability—is an attractive alternative to chemical surfactants in antiagglomeration. Results on the model systems show the promise for testing in real fluid systems and field testing of the ideas.