Microfluidics application for monitoring hydrate phase transition in flow throats and evaluation of its saturation measurement

Abstract

Natural gas hydrate is an unstable clathrate that can transform from solid to gas and liquid, making it difficult to precisely predict the heat and mass transfer in the pores. In this research, a microfluidics technology is introduced to directly monitor the hydrate phase transition processes in different sized throats. A new method for the calculation of hydrate saturation, named geometric measurement, is proposed with the assistance of magnified images, and this method is compared with two traditional methods to verify their applicability by discussing their related error sources. After analysis, the derivation calculation method is believed to have a wider scope of implementation but a larger error due to its numerous assumptions of an ideal state. At the beginning of the experiments, the saturations obtained by geometric measurement are believed to be larger than the actual values due to internal incompletely formation. As the void spaces were gradually eliminated, the geometric measurement results became more accurate. In contrast, the saturations obtained by fluid displacement were initially believed to be accurate, and became larger than the actual values with increasing hydrate growth due to the blockage of the flow throat. The relative errors of the different methods were calculated by selecting the results of fluid displacement before 60% hydrate saturation and the geometric measurement results of the remaining range as the reference standard. The comparison indicated that the accuracies of the geometric measurement and the fluid displacement were similar to and higher than those of the derivation calculation, respectively. In addition, the effects of the error sources were found to be weakened with increasing hydrate saturation and throat inner width.