Nuclear Magnetic Resonance Analysis of Methane Hydrate Formation in Water-in-Oil Emulsions

Abstract

Water-in-oil emulsions are of particular interest concerning methane hydrate formation during crude oil production. The objective of this work is to understand the morphology of the hydrate/water drops in waterin-oil emulsions. Hydrogen nuclear magnetic resonance (NMR) is used to directly measure the formation of methane hydrates in water-in-oil emulsions. A 2 MHz NMR spectrometer is used to investigate the relationship between the drop size distributions of water-in-oil emulsions and methane hydrate formation. The drop size distributions of two crude oil and two model oil emulsions are measured by the pulsed-field gradient with diffusion editing technique. This technique is particularly useful because it does not assume a priori the functional form of the drop size distribution. The amount of liquid water converted to hydrate is directly measured by transverse relaxation measurements. These NMR techniques investigate the entire emulsion sample, and they provide useful information regarding the relationship between drop size distributions and methane hydrate formation in emulsified systems.

Metastable boundary conditions of water‐in‐oil emulsions in the hydrate formation region

“…The presence of surface water on the particles can facilitate the agglomeration of hydrates during dissociation. From the studies of Aichele et al11 and Boxall et al,12 it can then be found that water droplet sizes affect both hydrate formation and agglomeration.…”

“…Furthermore, most drilling fluids in deepwater offshore drilling facilities, where hydrate plugging hazards may occur because of low seabed temperatures, are in forms of water‐in‐oil emulsions 3. Hence, understanding the characteristic of hydrate formation in water‐in‐oil emulsions has drawn much attention in recent years 4–14…”

“…With in‐depth studies on hydrate formation/dissociation in water‐in‐oil emulsions, the relevant experimental techniques such as the differential scanning calorimetry (DSC),3, 5–8 X‐ray diffraction,9, 10 nuclear magnetic resonance (NMR),11 particle video microscope (PVM), focused beam reflectance measurement (FBRM),12 and dielectric spectroscopy13, 14 have been used to characterize hydrate formation in water‐in‐oil emulsions. Dalmazzone et al5 measured the dissociation of methane hydrate in water‐in‐oil emulsion systems using the DSC technique and pressure vs. temperature measurements in a constant volume cell (pressure–volume–temperature, PVT).…”

“…Therefore, the attention of hydrate researches in water‐in‐oil emulsions has been paid to other directions because the thermodynamic difference between bulk solutions and emulsions has been thought to be negligible. Aichele et al11 analyzed methane hydrate formation in water‐in‐oil emulsions through the NMR technique. They showed some quantitative information about the relationship between water droplet‐size distributions and methane hydrate formation.…”

Hydrate Formation/Dissociation in (Natural Gas + Water + Diesel Oil) Emulsion Systems

“…The experimental results showed that the metastable boundary pressures increase with decreasing water-droplet sizes, but when the system pressure exceeds the metastable boundary pressure, hydrate formation occurs and the metastable state of the emulsion collapses. Aichele et al [15] used nuclear magnetic resonance to measure the formation of methane hydrates in water-in-oil emulsions and provided useful information regarding the relationship between drop size distributions and methane hydrate formation in emulsified systems. Boxall et al [16] performed methane hydrate formation/dissociation experiments from water-in-oil emulsions with three different size distributions.…”