Fang Fang

MSc 2015

Research topic: "3-D Analysis of Heavy-Oil Recovery by Solvents under Elevated Temperatures"

Thesis

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A technique to visualize miscible displacement in porous media using laser and the analysis of the results for different processes are presented in this thesis. After saturating the model made of different sized glass beads with oil, solvent was introduced either under dynamic (injection and production through a pair of horizontal wells) or static (diffusion of solvent into oil saturated model) conditions. The former simulates the VAPEX (vapor extraction) process dictated by viscous and gravitational forces and the latter (“diffusion experiments”) represents diffusion/gravity (and thereby convection) controlled displacement of oil by the solvent contacting the porous medium saturated with oil.

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The refractive indices of saturated and injected fluids were made the same by mixing the fluids with lower and higher indices of refraction to make the model fully transparent. Fluorescent dyes that were only visible with excitation of laser were dissolved in the solvent. A laser sheet scanned the model while synchronous pictures were taken by two high speed cameras from two sides of the model. 2-D images obtained through this process were converted to 3-D visual data and qualitative and quantitative analyses were conducted.

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An optimized injection method for the VAPEX process was determined by testing different - constant and variable- injection rates. The effect of solvent gravity and viscosity on the displacement (chamber growth) process was also analyzed through the 3-D images. Diffusion was the major factor in the transition zone at the edge of solvent chamber, as well as the solvent propagation from fracture to rock matrices.

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“Diffusion” experiments were done to analyze the sweep and smoothness of the front (diffusion) interface for different pore sizes, solvent/oil gravity and viscosity ratios, and the boundary effects. The box-counting fractal dimension of the solvent diffusion front in 3-D was applied to compare the progress of the solvent-oil interfaces (mixing process) for different conditions.

 

Vapor extraction (VAPEX) is one of the solvent applications suggested and tested for heavy-oil/bitumen recovery. Visualization of the process will be helpful to understand the physics in the process. We have designed an experiment to visualize the solvent displacement in porous media during VAPEX in 3D.  Also studied is the diffusion and imbibition process under purely static conditions using a similar set-up.

 

A 3D image of the model is obtained by sweeping the laser beam with a scanner though the cube, resulting in a small displacement between each of the thin laser sheets (setup shown in Figure 1). 3D images can be converted by integrating the images.

 

In order to view inside the model, the refractive indices of glass beads, mineral oil, and solvent were made to be the same to prevent refraction and reflection of laser at the surface of glass beads and liquids, and the interface between the oil and solvent. Kerosene was used as the solvent.  The refractive index (RI) of solvent was increased to 1.473 by adding high refractive fluid (refractive indices shown in Table 1, oleic phase, and solvent phase properties are in Table 2).

 

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Figure 1. The schematic of experiential setup used for the three-dimensional visualization.

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Diffusion Experiments

 

The glass-beads-packed model is used in the visualization experiments (Figure 2). The glass beads are packed densely and homogeneously in a 5×5×5 cm cube for the diffusion experiments. Florescent dyed solvent is contacted to the model from the bottom part filling the container with the dye (the yellow part in Figure 2).

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Figure 2. Diffusion model.

 

The fractal dimension describes the roughness of the displacement front. We used fractal dimension to measure the complexity of the solvent-oil interface. To avoid the effect of boundary, a fractal dimension is also calculated in a 3 cm x 3 cm x 5 cm cube in the center of the model.

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Publications:

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1. Fang, F. and Babadagli, T.: “Three Dimensional Visualization of Solvent Chamber Growth in Solvent Injection Processes: An Experimental Approach,” J. Petr. Sci. and Eng., vol. 142, 46-67, 2016.

2. Fang, F. and Babadagli, T.: “3-D Visualization of Diffusive and Convective Solvent Transport Processes in Oil Saturated Porous Media Using Laser Technology,” J. of Visualization, vol. 19, no. 4, 615-629, 2016.

3. Fang, F. and Babadagli, T.: “Dynamics of Diffusive and Convective Transport in Porous Media:  A Fractal Analysis of 3-D Images Obtained by Laser Technology,” Chaos, Solitons & Fractals, vol. 95, 1-13, 2016.

4. Fang, F. and Babadagli, T.: “Diffusion and Dispersion Dominated Solvent Injection Processes in Oil Saturated Porous Media: 3-D Visualization Experiments Using Laser Technology,” SPE 170649, 2014 SPE Annual Tech. Conf. and Exh., Amsterdam, The Netherlands, 27-29 Oct.

5. Fang, F. and Babadagli, T.: “Three Dimensional Visualization of Solvent Chamber Growth in Solvent Injection Processes: An Experimental Approach,” IPTC 18115, 2014 Int. Petr. Tech. Conf. (IPTC), Kuala Lumpur, Malaysia, 10-12 Dec.