Oilfield operations such as drilling, reservoir management, and production require the injection and/or production of complex fluids to improve the extraction of crude oils. Some of these complex fluids such as drilling muds, fracking fluids, foams, emulsions, surfactants, and polymers, fall under the classification of colloidal suspensions which is one substance of microscopically dispersed insoluble particles suspended throughout another substance. These colloidal suspensions show complex rheological properties that are dependent on the suspension properties, flow conditions, and flow conduit dimensions. Rheology of colloidal suspensions is a complex subject that is still being investigated. The focus of this study is on heavy oil-in-water emulsions. Heavy oil and bitumen resources account for approximately 70% of the remaining oil discovered to date in the world. Heavy crude oils are costly to produce, transport, and refine compared to light crude oils due to the high viscosity of heavy crude oils. To improve the economic viability of producing heavy oils, especially in a time with low crude oil prices, operational expenses must be reduced. One of the main areas to improve is the cost associated with transporting produced heavy oils from production wells to refineries. Currently, heavy oils are diluted with low viscosity diluents such as condensates and light crude oils to lower the mixture viscosity below 350 cSt before heavy oils can be transported through pipelines. The diluted mixtures require up to 50% (vol.) diluents to lower the heavy oil viscosity. High demand and low supply of condensates and constrained pipeline capacities have resulted in pipeline transportation costs of up to 22/bblofdilutedheavyoilfromCanadatorefineriesintheU.S.Analternativemethodoftransportingheavyoilsistotransportheavyoilsinanemulsifiedform,heavyoilβinβwateremulsions,whichcanshowordersofmagnitudelowerviscositiescomparedtotheviscosityofheavyoils.Inthisstudy,asimple,oneβstepmethodofpreparingheavyoilβinβwateremulsionswasdeveloped.Thephysicalpropertiesofheavyoilβinβwateremulsionsarecontrolledandmodifiedbyoptimizingthechemicalformulationusedtoprepareemulsions.Stableheavyoilβinβwateremulsionscanbepreparedwithchemicalformulationsthataretailoredtothetypeofheavyoilsandavailablewatersourceswhichcanrangefromfreshwatertosoftenedseawater.Therheologyofheavyoilβinβwateremulsionshasbeencharacterizedwitharotationalviscometer.Heavyoilβinβwateremulsions,especiallyconcentratedemulsions,showedcomplexrheologicalpropertiessuchasshearthinningbehavior,twoβstepyieldstresses,twoβstepwallslips,andrheopexy.Arheologicalequationandawallslipequationhavebeendevelopedtomodeltherheologyofheavyoilβinβwateremulsionsoverarangeofshearratesandflowconduitdimensions.Heavyoilβinβwateremulsionscharacterizedwithcapillarytubeviscometersshoweddrasticallydifferentviscositymeasurementscomparedtotheviscositymeasurementsobtainedwitharotationalviscometer.Thisisimportantbecausetheflowofemulsionsinpipelinesaresimilartotheflowofemulsionsincapillarytubeviscometers,notrotationalviscometers.ThelowerviscositiesmeasuredwithcapillarytubeviscometersareattributedtooildropletmigrationawayfromthetubewallsduetotheshearheterogeneityobservedinPoiseuille(tube)flow.Ascalingequationwasproposedtorelatetheviscositymeasurementsofemulsionswitharotationviscometertotheviscositymeasurementsofemulsionswithcapillarytubeviscometers.Therheologicalmeasurementsofheavyoilβinβwateremulsionsareusedtoestimatetheflowofemulsionsincrudeoilpipelineswithvariousradii.Viscositymeasurementsofoptimizedheavyoilβinβwateremulsionswitharotationalviscometershowedthatheavyoilβinβwateremulsionswithupto751-3/bbl of emulsion. Heavy oil-in-water emulsions also showed drag reduction properties which can significantly increase the maximum flow capacity of crude oil pipelines. Transporting heavy oils as concentrated heavy oil-in-water emulsions appeared to be a competitive if not a better method of lowering heavy oil viscosity compared to the diluent method in terms of cost and flow performance in pipelines.Petroleum and Geosystems Engineerin
The purpose of this research was
to create very polydisperse concentrated
heavy oil-in-water emulsions by optimizing the co-solvents, surfactants,
alkali, and electrolytes in the chemical formulation, with respect
to the droplet size distribution. Novel co-solvents that have shown
superior performance in chemical formulations used for enhanced oil
recovery have been tested. Droplet size distributions that resulted
in a lower emulsion viscosity were determined to have a higher mean
droplet diameter (<i>d</i><sub>32</sub>) and a bimodal droplet
size distribution with a diameter ratio (<i>d</i><sub>32,L</sub>/<i>d</i><sub>32,S</sub>) of > 6 and a volume fraction
(Ο<sub>S</sub>/(Ο<sub>L</sub> + Ο<sub>S</sub>))
of 0.2β0.3, where Ο is the volume fraction of the dispersed
phase and the subscripts L and S correspond to the larger and smaller
peaks in the bimodal distribution. We report the effects of various
chemical formulations on the droplet size distribution of heavy oil-in-water
emulsions with a particular emphasis on <i>d</i><sub>32</sub> and, for the first time, the maximum packing fraction (Ο<sub>m</sub>) of oil droplets. A novel one-step preparation procedure
is proposed to prepare concentrated multimodal oil-in-water emulsions
with a new chemical formulation approach. We were able to formulate
stable oil-in-water emulsions with Ο<sub>m</sub> values as high
as 0.95, which is βΌ0.30 higher than the theoretical Ο<sub>m</sub> value for random close packed monodisperse spheres (0.64).
We observed the optimal particle size distribution of concentrated
heavy oil-in-water emulsions prepared with co-solvents for maximum
packing at βΌ75% of the Na<sup>+</sup> concentration necessary
to reach the oil-in-water to water-in-oil inversion point for anionic
surfactants. An important application of this study is the transport
of heavy oils in pipelines