58th Annual Report on Research 2013 Under Sponsorship of the ACS Petroleum Research Fund

The main objective of this project is to understand hydrate formation behaviors at hydrate-forming gas/oil-water interfaces by injecting nano-particles into the interfaces. In the first year, we carried out two studies: 1) adhesion behavior between hydrate particles and free water and 2) hydrate formation behaviors at oil-hydrate-water interfaces in the presence of nano-particles.

We have firstly understood the effects of water volume on the interfacial dynamics between cyclopentane (CP) hydrate and water droplet in a CP/n-decane oil mixture. The adhesion force between CP hydrate and various water droplets was determined by using the z-directional microbalance. Through repetition of precise measurements over several cycles from contact to detachment, we observed abnormal wetting behaviors in the capillary bridge during the retraction process when the water drop volume is larger than 100 µL. With the increase in water droplet volumes, the contact force between CP hydrate and water also increases up to 300 µL but above this volume, there is a dramatic reduction of increasing rate in the contact forces. It was also observed with surfactant solution drops.  

Secondly, we have investigated and quantified hydrate formation at oil-hydrate-water interfaces in the presence of nano-particles and understand hydrate inhibition in the vicinity of interfaces. We employed hydrophobic silica nanoparticles at an interface of aqueous and hydrate-forming oil phases and analyzed the inhibition of hydrate crystal growth. A high-pressure micro-differential scanning calorimeter was used to quantitatively evaluate the hydrate inhibition performance. The total amount of hydrates formed from aqueous water phase decreases as the nano-particle concentration increases from 0 to 2.0wt.%. At a dosage level of 1.0 wt.% of silica nanoparticles injected into the water – oil interface significantly retarded hydrate formation. It was reflected in the shrinkage of the size and shape of the conical hydrate crystals while 500 - 1000 micron hollow conical hydrate crystals were vividly observed without using any hydrophobic nanoparticles. Hydrate growth was completely hindered with a hydrophobic nanoparticle concentration of 2.0 wt.% and the conical shape of hydrate crystal does not appear at all. The experimental results can provide insights into hydrate inhibition in oil and gas delivery lines possibly with hydrophobic nano-particle nanoparticles. Based on this finding, we will extend our study into hydrate formation with high-pressure hydrate formers as well as hydrophobic silica nano-particles.