Kinetic effect of polymethylsilsesquioxane (PMSQ) microspheres on methane hydrate formation and agglomeration in waxy oil–water system

Hydrate blockage and wax deposition have become two major hazards for deep-sea oil gas flow assurance industry. The existing prevention methods are mainly oriented to single solid phase blockage, yet how they affect multi-solid phases is rarely known. Moreover, the interaction of hydrate and wax remains unclear. Recently, adding pour point depressants (PPDs) has been proposed to be a novel technique to efficiently improve the rheology of waxy oil and prevent hydrate formation. In this paper, a series of mono-dispersed polymethylsiloxane (PMSQ) microspheres with different average sizes (0.5, 1.0 and 2.0 μm) were successfully synthesized and studied their effects on the wax deposition of waxy oil and the formation kinetics and aggregation behavior of CH 4 hydrate in the waxy oil–water system. The wax appearance temperature (WAT) test showed that PMSQ with a smaller size was more beneficial to reduce the WAT of waxy oil. Though poor in delaying hydrate nucleation, single PMSQ inhibited the hydrate growth and aggregation well, opposite to the role of wax. A synergistic/antagonistic effect of wax with PMSQ on preventing hydrate nucleation, growth and agglomeration was produced, depending on the wax content, size and dosage of PMSQ. Microstructure measurements indicated that wax and PMSQ were unable to alter the crystal structure of sI CH 4 hydrate, but significantly influenced the distribution of CH 4 in the hydrate cages, particularly large cage. The results give a deeper understanding of the inhibition mechanism and the synergistic potential of various additives, as well as providing a theoretical support for the PPDs used in the pipelines of natural gas production and transportation.