Generation of Nanoparticle-Stabilized Emulsions in Fractures
- Matthew Roberts (The University of Texas at Austin) | Behdad Aminzadeh (U. of Texas at Austin) | David A. DiCarlo (U. of Texas at Austin) | Steven Lawrence Bryant (U Of Texas At Austin) | Chun Huh (U. of Texas at Austin)
- Document ID
- Society of Petroleum Engineers
- SPE Improved Oil Recovery Symposium, 14-18 April, Tulsa, Oklahoma, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 2.5.2 Fracturing Materials (Fluids, Proppant), 1.6.9 Coring, Fishing, 1.11 Drilling Fluids and Materials, 4.1.5 Processing Equipment, 3 Production and Well Operations, 1.14 Casing and Cementing, 2 Well Completion, 4.1.2 Separation and Treating
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We investigated the ability of a dispersion of specially surface-treated nanoparticles to stabilize an oil/water emulsion of prescribed internal structure created by flow within a fracture. We hypothesize that for a set of conditions (nanoparticle concentration, salinity, aqueous to organic phase ratio) a critical shear rate exists. That is, for flow rates that exceed this critical shear rate, an emulsion can be created.
Flow experiments were conducted within fractured cylinders of Boise sandstone and of Class H cement. The Boise sandstone core (D = 1 in and L = 12 in) was cut down its length and propped open to a specific aperture with beads. The fracture was saturated with dodecane which was displaced with nanoparticle dispersion, and vice versa while pressure drop across the fracture was recorded. Class H cement cylinders (D = 1 in and L = 3 in) were allowed to set, then failed in tension to create a rough-walled fracture along their length. These fractured cement cylinders were then sealed and encased in epoxy to isolate the fractures. CT scans of the encased fractures were used to determine the aperture width, which is utilized when calculating the shear rate inside of the fracture maintained during an experiment. A dispersion of surface-modified silica nanoparticles and decane were co-injected into both the Boise sandstone and cement fractures and the pressure drop was measured across the fractures at a variety of shear rates. The effluent of each experiment was collected in sample tubes.
Observation of the effluent and pressure drop data both support our hypothesis of emulsion generation being possible once a critical shear rate has been reached. Alteration of the injected phase ratio and increased residence time of the two phases inside of a fracture both affect the amount of emulsification occurring within the fractures. Increasing the residence time of both phases within a fracture allows for more opportunities for emulsification to occur, resulting in a greater amount of emulsion to be generated. Injection of high or low volumetric ratios of nanoparticle dispersion to organic phase results in little amounts of emulsion generation; however, between the nanoparticle dispersion to organic phase ratios of 0.25:1 and 2:1 significant amounts of emulsion are generated once a critical shear rate has been reached.
The ability of surface-modified nanoparticles to stabilize oil-in-water or water-in-oil emulsions offers a variety of oilfield application possibilities, e.g., as mobility control and conformance control agents, and as constituents for drilling mud or well completions cement. Much work has been done in generating, characterizing, and developing applications of, the nanoparticle-stabilized oil-water emulsions that are known generally to have robust stability (see e.g., Binks et al., 2008), but
the use of nanoparticle-stabilized emulsions is a fairly new area of interest for oil industry (Zhang et al., 2010). In view of their long-term stability and ability to create very low mobility, such emulsions could be very useful in blocking the fractures often encountered in subsurface formations or those accidentally created in casing cement, especially if the emulsion can be generated spontaneously in situ in the fracture. With such potential applications in mind, we investigated the conditions under which surface-modified nanoparticle-stabilized oil-water emulsions can be generated inside of a rough-walled fracture.
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