Evaluating Diffusivity of Toluene in Heavy Oil Using Nuclear Magnetic Resonance Imaging

Abstract

Solvent-based processes have shown technical advantages over thermal techniques for recovery of heavy oil and bitumen. The success of these processes relies on accurate computation of molecular diffusion coefficient which determines how fast a solvent penetrates into oil. Concentration profile measurements of solvent in oil are used for the determination of the molecular diffusion coefficient. Although numerous experimental techniques have been proposed, the accurate estimation of this parameter is still a topic of debate in the literature. In this work, 1-D nuclear magnetic resonance imaging (MRI) is employed to obtain diffusivity data for a toluene–heavy oil system. Diffusion of toluene in heavy oil was monitored for 20 days at a controlled temperature of 35 °C and ambient pressure. Over time, toluene diffusion into oil leads to changes in spatial distribution of T 1 and T 2 that affect the received signal. This serves as the basis of the solvent and heavy oil concentration estimation. Consequently, concentration profiles were established by converting the MRI signals to concentration values. This conversion was achieved by creating samples with known concentrations of heavy oil–toluene and measuring their response in the same environment and parameter settings. A concentration-dependent diffusion coefficient was obtained from concentration profiles. The results show that relaxation based 1D MRI is an accurate and robust tool to obtain diffusivity data in complex fluids such as heavy oil.

One-pot neutron imaging of surface phenomena, swelling and diffusion during methane absorption in ethanol and n-decane under high pressure

“…The method, which is based on the neutron imaging of a cell containing a deuterated liquid upon its pressurization with a gas containing protium in its molecule, proved the ability to provide information on the methane diffusion into liquid, its swelling and capillarity from the single experiment in one pot. Hence, our new method enabled to collectively observe quantities, which could otherwise be studied only using multiple single-purpose methods, such as those for the visualization and measurement of diffusion in liquids [10,11,18,21,22,32,33,[35][36][37][38][39]41], measurement of capillarity [16][17][18][24][25][26][27][28][29][30][31] and liquid density [7,8,23]. Our method provided values of methane diffusivity and partial molar volume, liquid density of the solution, surface tension and its pressure derivative and contact angle at titanium under harsh conditions, while the observed quantities showed good agreement with the literature data where literature data or methods for their prediction are available [6-8, 10, 11, 13, 14, 16, 25, 26, 53, 54, 74, 81].…”

“…Recently, several advanced methods allowing for the observation of mass transport in bulk bodies have been reported. These methods involve the detection based on i) Raman spectroscopy, which was used to characterize diffusion in liquids and liquids at pressures near atmospheric [32,33] and the distribution of methane in methane hydrate at pressures up to 140 bar [34], ii) dynamic light scattering, which was used for the studies of diffusion of gases in liquids at pressures up to 34 bar [35], iii) Nuclear Magnetic Resonance (NMR), which was used for the studies on diffusion in liquids at pressures close to atmospheric [36][37][38], propane diffusion in liquids at pressures up to 10 bar [39] or methane distribution in methane hydrate at pressures up to 250 bar [40], iv) X-ray tomography, which was used for the studies on diffusion in liquids at pressures near atmospheric [38,41] and methane hydrate formation at pressures up to 62 bar [42], and, most recently, v) neutron imaging, which was used for the observation of ammonium absorption in solids at pressures near atmospheric [43].…”

Determining Diffusivity, Solubility, and Swelling in Gaseous Solvent–Heavy Oil Systems

“…Nuclear Magnetic Resonance (NMR) technology has been utilized in the oil and gas industry for core analysis, fluid characterization, and logging applications via relaxation measurements. 18 NMR imaging or MRI expands the realm of NMR by providing the spatial variability considerations (more details in ref 19). These spatiotemporal data are useful to establish the concentration profiles which can be employed for computation of concentration-dependent diffusivity.…”

Estimation of Gas Absorption and Diffusion Coefficients for Dissolved Gases in Liquids

“…Such information can be collected using a nondestructive method that involves application of CT, 47−53 NMR, 54 or MRI. 55 To implement this method, a cylindrical aluminum cylinder with the inner diameter of 5.07 cm was used as a test reservoir. Approximately half of this cylinder was filled with the liquid Peace River bitumen (ρ ≈ 1010 kg/m 3 , μ ≈ 55000 mPa•s), and then the selected gas was pumped above the liquid zone.…”

“…To provide the estimation of the diffusion of dissolved gases into liquids the volume concentration information has to be collected. Such information can be collected using a nondestructive method that involves application of CT, − NMR, or MRI . To implement this method, a cylindrical aluminum cylinder with the inner diameter of 5.07 cm was used as a test reservoir.…”