Aminzadeh-goharrizi, Behdad (University of Texas At Austin) | Huh, Chun (University of Texas At Austin) | Bryant, Steven Lawrence (University of Texas At Austin) | DiCarlo, David A. (The University of Texas at Austin) | Roberts, Matthew
Surface-treated nanoparticles have been shown to stabilize CO2-in-water foam by adhering to the surface of CO2 bubbles and preventing their coalescence. However, to bring the nanoparticles from the bulk phase to CO2/water interface requires an input of mechanical energy. Co-injection of CO2 and an aqueous dispersion of nanoparticles at high rates is known to provide sufficient energy. However, this co-injection is less favorable because of the operational constraint, i.e., injectivity reduction. Here, we show that beneficial effect of nanoparticles, manifested as improved sweep efficiency, occurs even at low shear rates in a drainage displacement.
We inject high-pressure liquid CO2 into sandstone cores initially saturated with brine containing suspended nanoparticles and compare the results with the case with no nanoparticle addition. The water saturation distribution was measured using CT scanning techniques. The results show that the nanoparticles increase sweep efficiency and reduce the gravity override compared to displacements without nanoparticles. The new mechanism described here provides a promising alternative for mobility control in CO2 floods.
A novel method of delivering thermal energy efficiently for flow assurance and for improved heavy oil production/transport is described. The method, an improved form of magnetic induction heating, uses superparamagnetic nanoparticles that generate heat locally when exposed to a high frequency magnetic field oscillation, via a process known as Neel relaxation. This concept is currently used in biomedicine to locally heat and burn cancerous tissues.
Dependence of the rate of heat generation by commercially available, single-domain Fe3O4 nanoparticles of ~10 nm size, on the magnetic field strength and frequency was quantified. Experiments were conducted for nanoparticles dispersed in water, in hydrocarbon liquid, and embedded in a thin, solid film dubbed "nanopaint". For a stationary fluid heat generation increases linearly with loading of nanoparticles. The rate of heat transfer from the nanopaint to a flowing fluid was up to three times greater than the heat transfer rate to a static fluid.
Heating of nanopaint with external magnetic field application has immediate potential impact on oil and gas sector, because such coating could be applied to inner surfaces of pipelines and production facilities. A nanoparticle dispersion could also be injected into the reservoir zone or gravel pack near the production well, so that a thin, adsorbed layer of nanoparticles is created on pore walls. With localized inductive heating of those surfaces, hydrate formation or wax deposition could be prevented; and heavy oil production/transport could be improved by creating a "slippage layer" on rock pore walls and inner surfaces of transport pipes.
Aminzadeh-goharrizi, Behdad (U. of Texas at Austin) | DiCarlo, David A. (The University of Texas at Austin) | Hyun Chung, Doo (U Of Texas At Austin) | Roberts, Matthew (U. of Texas at Austin) | Bryant, Steven Lawrence | Huh, Chun
Injecting nanoparticles into the subsurface can have a potential impact on altering both oil recovery and/or CO2 sequestration. In this work we conduct core floods in which a CO2-analogue fluid (n-octane) displaces brine with and without dispersed nanoparticles. We find that the floods with nanoparticles cause
a greater pressure drop, and a change in flow pattern compared to the floods without. Emulsion formation is inferred by measuring the saturation distribution and pressure drop along the core. The results suggest that nanoparticle stabilized emulsion is formed during a drainage process (at low shear rate condition) which acts to reduce the mobility of the injected fluid.
We also perform imbibition experiments, where the nanoparticle dispersion in brine displaces noctane. Here we observe little difference in the flow pattern and pressure drop as a function of nanoparticle concentration. There is an observed accumulation of nanoparticles at the imbibition front,
which suggests that nanoparticles may be used as a tracer of the displacement front.
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.
Worthen, Andrew (U. of Texas at Austin) | Bagaria, Hitesh (University Of Texas At Austin) | Chen, Yunshen (U Of Texas At Austin) | Bryant, Steven Lawrence (U Of Texas At Austin) | Huh, Chun (U. of Texas at Austin) | Johnston, Keith P. (U Of Texas At Austin)
Viscous C/W foams were generated without the use of polymers or surfactants by shearing CO2 and an aqueous phase containing partially hydrophobic silica nanoparticles in a beadpack filled with 180µm glass beads. Silica particles with 50% SiOH coverage were chosen because they have a hydrophilicity that falls between the 42% SiOH optimum foaming ability for A/W foams (Binks and Horozov 2005) and the 67% SiOH which gave maximum O/W emulsion stability (Binks and Lumsdon 2000). These 50% SiOH silica nanoparticles were found to be interfacially active for CO2-water systems, and stabilized the desired curvature of C/W foams. When the HCB of the nanoparticles is tuned to give contact angles less than 90°, the particles reside primarily in the water phase and C/W foams can be formed. Formation of C/W emulsions stabilized solely with nanoparticles is desirable because it does not require solvation of surfactant tails or polymer chains by CO2. Interfacially active nanoparticles can adsorb at the CO2 water interface without the need for solvation in CO2.
Properly designed nanoparticles generated foams that were more stable than foams generated with polymer-coated nanoparticles or with the nonionic surfactant Tergitol™ 15-S-20 alone. Macroscopic observations showed foams generated solely with 50% SiOH nanoparticles stayed bright white and opaque over 23 hours, while foams generated with PEG-coated silica particles or with surfactant alone resolved nearly completely. Foams generated solely with Tergitol™ 15-S-20 were unstable because surfactant molecules dynamically enter and leave the interface and thus do not provide long-term stabilization. Foams generated with PEG-coated silica particles, though initially very viscous, showed poor long-term stability because of the small particle size and poor solvation of PEG chains in CO2. The larger 50% SiOH nanoparticles strongly adsorbed at the CO2-water interface and provided a barrier around the CO2 bubbles, resulting in very stable foams.
Kulawardana, Erandimala Udamini (U. of Texas at Austin) | Koh, Heesong (U. of Texas at Austin) | Kim, Do Hoon (U Of Texas At Austin) | Liyanage, Pathma Jithendra (U. of Texas at Austin) | Upamali, Karasinghe (U. of Texas at Austin) | Huh, Chun (U. of Texas at Austin) | Weerasooriya, Upali (U. of Texas at Austin) | Pope, Gary Arnold
New polymers that are stable in harsh environments (high salinity/hardness and high temperature) are in high demand because of the need for chemical EOR in oil reservoirs with these conditions. Commonly used partially hydrolyzed polyacrylamides (HPAM) have been successfully used in the field for decades, but they hydrolyze at high temperature and eventually precipitate in the presence of high concentrations of divalent cations. This paper mainly focuses on rheology and transport behavior of scleroglucan (non-ionic polysaccharide) and N-vinylpyrrolidone (NVP)-polyacrylamide (AM) co-polymer. The rigid, rod-like, triple helical structure of scleroglucan imparts exceptional stability and its non-ionic functionality makes it insensitivity to salinity and hardness. By a different mechanism, NVP in modified HPAM protects the polymer's amide group against thermal hydrolysis, i.e., by sterically hindering the amide group. This allows maintaining high viscosity even in high salinity brines at high temperature. Both scleroglucan and NVP co- or ter-polymers show good filterability and transport properties in sandstone and carbonate cores at high temperature and in brine with high salinity and hardness. Therefore, both polymers are promising candidates for polymer flooding, surfactant-polymer flooding and alkali-surfactant-polymer flooding in hard brine at high temperature, but must be evaluated under specific reservoir conditions.
Introduction and Background
A wide variety of polymers have been evaluated for their possible EOR application under high temperature and high salinity conditions (Askinsat, 1980). Incorporating monomer groups that are much resistant to hydrolysis, 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), poly-vinylpyrrolidones (PVP), or N-vinylpyrrolidones (NVP), (Doe et al., 1987; Levitt and Pope, 2008; Vermolen et. al., 2011) significantly increased their tolerance to divalent ions and improved their resistance to precipitation. On the other hand, polysaccharides such as xanthan gum, scleroglucan, carboxymethylcellulose, and guar gum, have also been extensively investigated for EOR. These biopolymers are less sensitive towards high salinities, temperatures, and mechanical degradation due to their semi-rigid molecular structure (Kohler and Chauveteau, 1981). However, combinations of high temperature, high salinity and high divalent ion concentrations limit the performance of many of these polymers (Davison and Mentzor, 1982).
According to Davison and Mentzer (1982), polyacrylamides, cellulose-based polymers and guar gum showed limited thermal stability and poor sea water viscosification. PVP was a poor viscosifier when considering its molecular weight. Xanthan gum showed better performance but the content cell debris affected its thermal stability, filterability, and adsorption (Davison and Mentzor, 1982; Doe et. al., 1987). Also the upper limit of xanthan gum usefulness was identified as less than 70 oC (Ryles, 1983; Ash, et. al., 1983).