Browsing by Subject "Friction reduction"
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Item Evaluation of friction reducers for use in recycle fracturing flowback and produced water(2014-05) Kuzmyak, Nicholas John; Katz, Lynn Ellen; Oort, Eric vanThe continued expansion of hydraulic fracturing activity in North America -- especially in slickwater operations -- has given rise to concerns regarding water quantity and quality. On one hand, operators in arid areas must compete with other users to obtain enough fresh water to perform fracturing operations, while in other areas the flowback water after a treatment must be either expensively treated or disposed of in injection wells, which are in very limited supply in regions such as the Marcellus Shale. Reuse of these highly saline waters can help to alleviate both of these problems. However, water that contains concentrated and difficult-to-remove salt ions -- especially divalent cations -- cannot be used with typical polyacrylamide friction reducers, due to these additives' dramatically decreased effectiveness in such fluids. Otherwise, reuse would be an attractive option and, in fact, this practice is widespread in multiple US shale plays with the recent advent of salt-tolerant polyacrylamides. This research attempts to quantify the effect of high salt concentrations on the effectiveness of friction reducers through construction of a flow loop apparatus that allows for observation of turbulent drag reduction. The polymers tested were chosen from industry standards (inverse oil-emulsion salt-tolerant anionic polyacrylamide), novel polyacrylamides (highly salt-tolerant polyacrylamide dispersed in concentrated brine), and an overlooked yet potentially highly effective polymer (i.e. polyethylene oxides, PEOs). PEOs, in particular, have been known as highly efficient friction reducers in brines for over 50 years, but are not used in the fracturing industry for various reasons. These three additives were tested at concentrations of 0.1% in solutions of sodium chloride, calcium chloride, and a multisolute brine of both salts. The experiments show that the typical salt-tolerant polyacrylamide is indeed negatively affected by the divalent calcium ions, while the novel polyacrylamide is a strong performer (up to 60% friction reduction) in even the strongest brines. Interestingly, the PEOs consistently produced about 45% friction reduction (based on the base fluid pipe friction pressure drop), and did so at low concentrations (<0.1%) for a range of molecular weights. The major conclusion of this research is that even highly concentrated brine can be recycled with minimal treatment if either the novel polyacrylamide or PEOs are used, opening the door for potential use of other atypical brine sources in hydraulic fracturing operations. The PEOs are especially interesting because, though overlooked, they are economical, readily available, and salt-tolerant. Future experiments will be run on a larger flow loop to potentially optimize PEO characteristics and further demonstrate their viability as an alternative to polyacrylamides.Item Impact of salt-tolerant friction reducers on shale stability and fracture conductivity(2014-08) Mimouni, Arielle Simone; Katz, Lynn Ellen; Oort, Eric van; Sharma, Mukul M.One of the main challenges of hydraulic fracturing is the reuse of flowback waters. While it alleviates the disposal and treatment costs of these concentrated brines, it also limits the environmental impacts of the fracking industry by reducing the amounts of fresh water necessary to produce gas. This research aims at optimizing this process by assessing the impacts of salt-tolerant friction reducers on shale stability and fracture conductivity. Polyacrylamide and polyethylene oxide based friction reducers were assessed over a wide range of NaCl and CaCl₂ concentrations, using a hot rolling oven and fracture conductivity experiments. The commonly used polyacrylamide based DR3046 was found to be a good shale stabilizer but did not efficiently reduce friction in the presence of divalent salts. While high molecular weight polyethylene oxides showed a high friction reduction in all brines, and reduced shale cuttings dispersion in the presence of salts, they did not maintain fracture conductivity. The newly developed Dispersion Polymer Friction Reducer (DPFR) showed the best and most consistent results for all salt concentrations, in terms of friction reduction, shale stabilization efficiency, and ability to maintain the highest fracture conductivity.Item Pressure and thermal effects on superhydrophobic friction reduction in a microchannel flow(2013-08) Kim, Tae Jin, active 21st century.; Hidrovo, Carlos H.As the fluidic devices are miniaturized to improve portability, the friction of the microchannel becomes intrinsically high and a high pumping power will be required to drive the fluid. Since the pumping power delivered by portable devices is limited, one method to reduce this is to render the surface to become slippery. This can be achieved by roughening up the microchannel wall and form a bed of air pockets between the roughness elements, which is known as the superhydrophobic Cassie-Baxter state. While the study on superhydrophobic microchannels are focused mainly in maximizing the friction reduction effects and maintaining the stability of the air pockets, less attention has been given to characterizing the microchannel friction under a metastable state, where partial flooding of the micro-textures may be present, and under heated conditions, where the air pockets are trapped between the micro-textures. In order to quantify the frictional characteristics, microchannels with micron-sized trenches on the side walls were fabricated and tested under varying inlet pressures and heating conditions. By measuring the hydrodynamic resistance and comparing with numerical simulations, results suggest that (1) the air-water interface behaves close to a no-slip boundary condition, (2) friction becomes insensitive to the wetting degree once the micro-trenches become highly wetting, (3) the fully wetted micro-trench may be beneficial over the de-wetted ones in order to achieve friction reduction effects and (4) heating the micro-trenches to induce a highly de-wetting state may actually be detrimental to the microchannel flow due the excessive growth of the air layer. As part of the future work to characterize heat transfer in superhydrophobic microchannels, a rectangular microchannel with microheaters embedded close to the side walls was fabricated and the corresponding heat transfer rates were measured through dual fluorescence thermometry. Results suggested that significant heat is lost through the environment despite the high thermal resistance of the microchannel material. An extra insulation is suggested prior to characterizing the convective heat transfer coefficients in the superhydrophobic microchannel flow.