Monitoring gas hydrate formation with magnetic resonance imaging in a metallic core holder

Abstract

Methane hydrate deposits world-wide are promising sources of natural gas. Magnetic Resonance Imaging (MRI) has proven useful in previous studies of hydrate formation. In the present work, methane hydrate formation in a water saturated sand pack was investigated employing an MRI-compatible metallic core holder at low magnetic field with a suite of advanced MRI methods developed at the UNB MRI Centre. The new MRI methods are intended to permit observation and quantification of residual fluids in the pore space as hydrate forms. Hydrate formation occurred in the water-saturated sand at 1500 psi and 4 °C. The core holder has a maximum working pressure of 4000 psi between -28 and 80 °C. The heat-exchange jacket enclosing the core holder enabled very precise control of the sample temperature. A pure phase encode MRI technique, SPRITE, and a bulk T1-T2 MR method provided high quality measurements of pore fluid saturation. Rapid 1D SPRITE MRI measurements time resolved the disappearance of pore water and hence the growth of hydrate in the sand pack. 3D π-EPI images confirmed that the residual water was inhomogeneously distributed along the sand pack. Bulk T1-T2 measurements discriminated residual water from the pore gas during the hydrate formation. A recently published local T1-T2 method helped discriminate bulk gas from the residual fluids in the sample. Hydrate formation commenced within two hours of gas supply. Hydrate formed throughout the sand pack, but maximum hydrate was observed at the interface between the gas pressure head and the sand pack. This irregular pattern of hydrate formation became more uniform over 24 hours. The rate of hydrate formation was greatest in the first two hours of reaction. An SE-SPI T2 map showed the T2 distribution changed considerably in space and time as hydrate formation continued. Changes in the T2 distribution are interpreted as pore level changes in residual water content and environment.

Experimental Study on Mechanical Properties of Hydrate-Bearing Sand: The Influence of Sand-Water Mixing Methods

“…Therefore, water content will be detected precisely and displayed directly in the saturation profile by proton NMR. The DHK SPRITE method was employed to measure the one-dimensional profiles [30], as shown in Figure 4. Water content obtained at different positions of samples are presented in Figure 4.…”

Fractal Analysis on Methane Hydrate Formation in Porous Media

“…The changes of liquid in the pores during the hydrate phase transition can be monitored by MRI technology, which can more intuitively observe the hydrate formation process. Shakerian et al [6] used MRI technology to study the formation process of gas hydrate in metal core holders and studied the formation rate of hydrate through the change of T 1 and T 2 relaxation time. Zhang et al [7] visualized the change of water saturation during the phase transition of methane hydrate through low-field nuclear magnetic resonance experiments and found that the spatial distribution of gas-water-hydrate during the phase transition of hydrate was not uniform over time.…”

Monitoring Methane Hydrate Formation And Reformation In A Partially Saturated Sand Pack

“…Therefore, it is of great significance to study the characteristics of MH formation and reformation. At the same time, there are many studies shown that MRI technique is a powerful analytical tool for noninvasive multidimensional quantitative analysis of flow and transport in porous media, such as the hydrate [3,4]. It provides a lot of technical support on fluid characteristics and hydrate research in recent years [5].…”