Estimativa da porosidade de hidrato de tetrahidrofurano por meio da avaliação de parâmetros ultrassônicos

Abstract

For the flow assurance area in the oil and natural gas industry the formation of hydrates can be considered a problem. Hydrates are crystalline structures composed of water and gas molecules, which form under specific conditions of temperature and pressure. The occurrence of hydrates can obstruct pipelines, causing economic, environmental and operational risks. In this sense, there are numerical models of hydrate growth simulation, where porosity is an important factor in modeling, besides representing significant information regarding its rate of dissociation. To date, there is no knowledge of the existence of a method for estimating this parameter, which is neither invasive nor intrusive. In this work ultrasound transducers are used, precisely because they do not present such disadvantages. This study uses ultrasound for the estimation of porosity of hydrates. Tetrahydrofuran (THF) is used as the hydrate-forming compound because it resembles methane hydrate found in the industry, with the advantage of forming at ambient pressure. The evaluation of four parameters that can be obtained from the ultrasound wave was carried out for porosity estimation: peak amplitude of the echo; echo envelope attenuation coefficient; signal energy and frequency spectrum magnitude. Initially the study used porous reference samples, obtained by 3D printing, to understand the behavior of the parameters used. Thereafter, experiments were performed with THF hydrate in two different situations: static formation and formation by agitation. The results obtained demonstrate a significant correlation and sensitivity between the ultrasound parameters and the porosity content, suggesting to be a promising methodology to estimate the porosity of the hydrate. In addition, agitation has been found to influence the porosity of the hydrate.