Abstract

Hydrates formation on the production lines constitutes a severe issue affecting significantly oil & gas production plants, especially on deep and ultra-deep fields. Prevention, based on addition of chemicals to limit hydrate formation, works only under certain limited conditions and suffers for cost and environmental impact. In this work, different methods of surface modification were applied on samples with the aim to significantly decrease the adhesion of hydrates to the cold pipe wall. These surface modification methods have been designed to cope with the different physical mechanisms, which concur to favour hydrate formation and adhesion to the surface itself. Chemical modification of steel surface is very challenging due to its inherent chemical resistance. Some methods designed to cover the surface and mainly based on special functionalization with Fluorinated Phosphonic Acids (FPA) are described. These methods have been applied to treat the surface of stainless steel 316 (SS316) samples and the results that describe quantitatively the effects on the surface properties are reported. The treated samples have been tested in a specially designed pressure cell (100 bar), which allows methane hydrate formation under controlled conditions. The pressure device was equipped with a fiber optical system to check hydrate formation and a torsional balance tool to quantitatively measure the adhesion strength of hydrate on the surface of the sample. The results reported show the important effects associated to different chemical modifications of the surface and the level of influence of these modifications in terms of hydrate formation. The measurement of the strength of adhesion of hydrate molecules allowed the evaluation of the quality of the surface treatment in lowering adhesion. The results and possible applications in the industrial context are discussed and detailed.

Introduction

Hydrate formation is a major risk in Oil& Gas industrial operations. This could cause several technical issues affecting significantly the economic impact of operational projects.

Hydrates are crystalline structures formed by a lattice of water cages entrapping hydrocarbon molecules at high pressures such as in subsea operations [1-3] (Figure 1 a).

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