Edo Boek | University of Cambridge (original) (raw)
Papers by Edo Boek
Physical Review E, 2016
We present a coupled transport and dissolution model for use in pore-scale modelling of reactive ... more We present a coupled transport and dissolution model for use in pore-scale modelling of reactive transport in complex media such as carbon-storage injection operations. We couple a lattice Boltzmann model for flow calculation with a finite volume method for solving chemical transport equations. The computational grid is allowed to change as mineral surfaces are dissolved according to first order reaction kinetics. We show how the popular first-order convection scheme is affected by severe numerical diffusion when grid Peclet numbers exceed unity, and confirm that this can be overcome relatively easily by using a second order method in conjunction with a flux limiter function. A novel rescaling method is used to counteract errors in surface area exposed by the Cartesian grid and avoid the use of more complex embedded surface methods when surface reaction kinetics are incorporated. Finally, we compute dissolution in an image of a real porous limestone rock sample injected with HCl for different Peclet numbers and obtain dissolution patterns in concordance with theory and experimental observation. A low injection flow rate was shown to lead to erosion of the pore-space concentrated at the face of the rock, whereas a high flow rate leads to wormhole formation.
Filling the Gaps – from Microscopic Pore Structures to Transport Properties in Shales, 2000
Transport properties in shales were investigated using experimental and computersimulation method... more Transport properties in shales were investigated using experimental and computersimulation methods. First, an experimental method based on a transient pressuredecay technique was further developed and used instead of classical Darcy core-flood methods. This has allowed measurement of the permeability of tight shale samples on much shorter time scales than by conventional methods. Second, molecular dynamics (MD) computer simulations were used to measure the diffusion coefficients of water and cations in a model clay sample. Measurements of the self-diffusion coefficient showed that the values increased with increasing water content. The results for Na-, Li-, and K-smectites are in satisfactory agreement with experimental and with other simulation results in the literature indicating that the clay interlayer space is an important route of transport for ions and water. The results also lend credibility to the correctness of the diffusion coefficients obtained from the current MD simulations.
We describe the ongoing development of lattice-Boltzmann (LB) computer simulation codes to study ... more We describe the ongoing development of lattice-Boltzmann (LB) computer simulation codes to study flow in porous media at the pore scale. LB simulations have evolved over the past decade and are now used as a tool to calculate both single-and multi-phase flow properties directly at the pore scale using X-ray Micro Tomography (XMT) pore space images. We will review the development of our codes to study flow in two-dimensional micro-models, viscous fingering, chemical reactions, hydrodynamic dispersion and non-Newtonian flow. In three dimensions, we have developed our codes to calculate the flow in XMT images of the pore space, for both single-and multi-phase flow, resulting in predictions of the permeability. Very recently, we have extended the multi-phase flow model to include surfactants for reduction of the interfacial tension and wettability alteration.
J Am Chem Soc 117 12608 12617, Dec 20, 1995
... Abstract: Monte Carlo molecular modeling simulations have been performed to investigate some ... more ... Abstract: Monte Carlo molecular modeling simulations have been performed to investigate some of the microscopic mechanisms underlying smectite clay swelling. ... 1983, 31, (13) Skipper, NT; Soper, AK; McConnell, JDC J. Chem. Phys. ...
Energy Fuels, 2011
ABSTRACT In this paper, we present preliminary calculations of the potential of mean force (PMF) ... more ABSTRACT In this paper, we present preliminary calculations of the potential of mean force (PMF) from molecular dynamics simulations of asphaltene molecules on a calcite surface. We calculate, for the first time, the PMF between an asphaltene molecule and the calcite surface directly by a constraint force method. The asphaltene molecule is obtained in a systematic way consistent with experimental information, using the quantitative molecular representation approach. The calcite surface has been defined as the {10.4} face, which is representative of the experimentally dominant crystal face. First, we calculate the time-averaged values of the constraint force as a function of the z distance between the asphaltene molecule and the calcite surface. We observe that, at a separation of 3 Å, the value of the force is positive, which corresponds to a repulsive interaction. At 3.5 Å, a minimum in the force is observed, corresponding to an attractive interaction. At longer distances, the average constraint force goes to zero, according to expectations. Then, we calculate the integral of the time-averaged constraint force as a function of the distance between the asphaltene molecule and the calcite surface. The difference between the minimum energy and the energy at large separations gives an estimate of the free energy of adsorption. In this case, the value of the free energy is of the order of 110 kJ/mol. This is a reasonable value for simulations in vacuo corresponding to an effective solvent.
The Journal of Physical Chemistry, 1994
Energy Fuels, Mar 3, 2008
The aggregation and deposition of colloidal asphaltene in reservoir rock is a significant problem... more The aggregation and deposition of colloidal asphaltene in reservoir rock is a significant problem in the oil industry. To obtain a fundamental understanding of this phenomenon, we have studied the deposition and aggregation of colloidal asphaltene in capillary flow by experiment and simulation. For the simulation, we have used the Stochastic Rotation Dynamics (SRD) method, in which the solvent hydrodynamics emerges from the collisions between the solvent particles, while the Brownian motion 2 emerges naturally from the interactions between the colloidal asphaltene particles and the solvent. The asphaltene colloids interact through a screened Coulomb potential. We vary the well depth ε and the flow rate v to obtain Pe flow >> 1 (hydrodynamic interactions dominate) and Re << 1 (Stokes flow). In the simulations, we impose a pressure drop over the capillary length, and measure the corresponding solvent flow rate. We observe that the transient solvent flow rate decreases when the asphaltene particles become more "sticky". For a well depth ε = 2 k B T, a monolayer deposits of on the capillary wall. With increasing well depth, the capillary becomes totally blocked. The clogging is transient for ε = 5 k B T, but appears to be permanent for ε = 10 -20 k B T. We compare our simulation results with flow experiments in glass capillaries, where we use extracted asphaltenes in toluene, reprecipitated with n-heptane. In the experiments, the dynamics of asphaltene precipitation and deposition were monitored in a slot capillary using optical microscopy under flow conditions similar to those used in the simulation. Maintaining a constant flow rate of 5 µL min -1 , we found that the pressure drop across the capillary first increased slowly, followed by a sharp increase, corresponding to a complete local blockage of the capillary.
Qatar Foundation Annual Research Conference, Nov 13, 2014
Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Mar 1, 1997
The rheological properties of colloidal suspensions of spheres, rods, and disks have been studied... more The rheological properties of colloidal suspensions of spheres, rods, and disks have been studied using a mesoscopic simulation technique, known as dissipative particle dynamics (DPD). In DPD, a suspension is modeled as a system of large colloidal particles in a liquid of interacting point particles. For the calculation of hydrodynamic interactions, this method is computationally more efficient than conventional techniques using a continuum model for the solvent. Applying a steady-shear rate to the particulate suspensions, we have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol % suspension of spheres displays characteristic shear-thinning behavior as a function of increasing shear rate. The values for the high- and low-shear viscosity are in good agreement with experimental data. For higher particulate densities good results are obtained for the high-shear viscosity, although the viscosity at low-shear rates shows a dependence on the size of the suspended spheres that we attribute to finite size effects. Dilute suspensions of rods and disks show intrinsic viscosities which are in excellent agreement with theoretical predictions. For concentrated suspensions of both rods and disks, the viscosity increases with the third power of the volume fraction. We find the same scaling behavior as predicted by Doi and Edwards [M. Doi and S. F. Edwards, The Theory of Polymer Dynamics (Oxford University Press, New York, 1986)] for rod suspensions in the semidilute regime. The DPD simulation technique emerges as a useful tool for studying the rheology of particulate suspensions.
Physical Review E Statistical Nonlinear and Soft Matter Physics, Oct 1, 2004
We study the influence of shear flow on the formation of rings in a generic reversible polymer (F... more We study the influence of shear flow on the formation of rings in a generic reversible polymer (FENE-C) model, representative for wormlike micelles. Under equilibrium conditions, rings are dominating in dilute solutions, while linear chains are dominating in strongly overlapping and concentrated solutions. We find that shear flow induces a net shift of micellar mass from linear chains to rings. At the same time, the average aggregation size of linear chains is decreasing, while the average aggregation size of rings is increasing. We hypothesize that the increased abundance and size of rings are caused by a decreased entropy gain associated with ring opening under shear flow. Linear chains and rings are elongated in the flow direction and contracted in the gradient direction. This leaves an essentially two-dimensional free volume, which two newly created chain ends can explore after being disconnected. We study the ratio of ring and linear chain distribution functions to substantiate this hypothesis. Finally, we study the rheology and discuss how the observed increase of ring abundance can provide a positive feedback between strain and ring connectivity. Such a positive feedback can contribute to shear thickening behavior, observed in micellar solutions near the overlap concentration.
Advances in Water Resources
ABSTRACT
The Journal of Physical Chemistry, 1994
ABSTRACT
We present a LB study of the flow of single-phase non-Newtonian fluids, using a power law relatio... more We present a LB study of the flow of single-phase non-Newtonian fluids, using a power law relationship between the effective viscosity and the local shear rate. Channel flow experiments were carried out to measure the velocity profiles. The simulation results are found to be in good agreement with theory. We also report simulations of the flow of non-Newtonian fluids in a 2-D porous medium.
Gas clathrate hydrates are crystalline inclusion compounds in which a water host lattice encages ... more Gas clathrate hydrates are crystalline inclusion compounds in which a water host lattice encages small guest atoms or molecules. They are environmentally important as a potential means for CO 2 capture and also in terms of the vast oceanic reserves of methane hydrate, which represent both a potential source of fuel for the future and a potential threat in the event of methane escape to the atmosphere. They are important in the oil and gas industry because they form in and clog pipelines during oil and gas recovery. Modelling the phase equilibria of hydrate systems is, in some respects, a solved problem; accurate calculation of the hydrate locus for many simple and mixture gas hydrates has been possible for decades. At the core of many modelling techniques is the statistical-thermodynamic treatment of van der Waals and Platteuw [1], first published almost 50 years ago and generalised to mixtures by Parrish and Prausnitz [2] in the 1970s. However, an important constituent part of the ...
In this paper, we investigate pore scale models for the storage of CO2 in subterranean rock forma... more In this paper, we investigate pore scale models for the storage of CO2 in subterranean rock formations. Various mechanisms for storage and trapping have been proposed, including structural, solution, mineralisation and the immobilisation of CO2 by capillary trapping. Currently, the capillary trapping mechanism seems to be a suitable option, as it is a fast way to render the injected supercritical CO2 immobile. In addition, this trapping mechanism does not rely entirely upon the cap rock maintaining its integrity on geologic time scales. One important parameter for the success of capillary trapping is the residual saturation after CO2 injection in the formation. The saturation is determined by the wetting properties of the rock formation. Often, and particularly in carbonate reservoirs, the rock may be wetting to CO2, especially when injected under supercritical conditions. In this case, the mechanism of entry of CO2 into the pores of the rock matrix is determined by spontaneous imbi...
SPE Annual Technical Conference and Exhibition, 2013
ABSTRACT Not finding what you're looking for? Some of the OnePetro partner societies have... more ABSTRACT Not finding what you're looking for? Some of the OnePetro partner societies have developed subject- specific wikis that may help. PetroWiki PetroWiki was created from the seven volume Petroleum Engineering Handbook (PEH) published by the Society of Petroleum Engineers (SPE). The SEG Wiki The SEG Wiki is a useful collection of information for working geophysicists, educators, and students in the field of geophysics. The initial content has been derived from : Robert E. Sheriff's Encyclopedic Dictionary of Applied Geophysics, fourth edition.
Qatar Foundation Annual Research Forum Proceedings, 2012
Energy & Fuels, 2015
ABSTRACT The viscosity of heavy crude oils strongly affects their producibility and recovery from... more ABSTRACT The viscosity of heavy crude oils strongly affects their producibility and recovery from oil reservoirs. Thus, the viscosity of heavy crude oils with dissolved gases at different shear rates is valuable knowledge for heavy crude oil exploitation. However, most publications only present viscosity measurements at one specific shear rate, and only a few papers in the literature have reported the rheological measurements over a range of shear rates. In this study, viscosity measurements of CO2-saturated heavy crude oils were performed as a function of the shear rate, at a temperature of 25 °C and pressures up to 220 bar. The experimental apparatus is a unique circulation system, which is able to measure the viscosity of CO2-saturated mixtures. A novel high-pressure rheometer with a flow-through Couette geometry was developed to measure the viscosity at a range of shear rates. The experimental results show that the addition of CO2 to heavy crude oil at the given temperature and pressures reduces the viscosity significantly, but the pressure dependence of the mixture viscosity changes at the phase transition of the CO2-rich phase. A modified Arrhenius equation, accounting for the effect of CO2 composition on viscosity, is applied to correlate the viscosity data.
Lecture Notes in Computer Science, 2003
An experimental study of gemini surfactants with different types of spacer has been reported in a... more An experimental study of gemini surfactants with different types of spacer has been reported in a number of papers [1,2,3]. So-called gemini or bis-surfactants are formed by two novel surface active molecules connected via a flexible or rigid linkage between the hydrophilic head ...
Physical Review E, 2016
We present a coupled transport and dissolution model for use in pore-scale modelling of reactive ... more We present a coupled transport and dissolution model for use in pore-scale modelling of reactive transport in complex media such as carbon-storage injection operations. We couple a lattice Boltzmann model for flow calculation with a finite volume method for solving chemical transport equations. The computational grid is allowed to change as mineral surfaces are dissolved according to first order reaction kinetics. We show how the popular first-order convection scheme is affected by severe numerical diffusion when grid Peclet numbers exceed unity, and confirm that this can be overcome relatively easily by using a second order method in conjunction with a flux limiter function. A novel rescaling method is used to counteract errors in surface area exposed by the Cartesian grid and avoid the use of more complex embedded surface methods when surface reaction kinetics are incorporated. Finally, we compute dissolution in an image of a real porous limestone rock sample injected with HCl for different Peclet numbers and obtain dissolution patterns in concordance with theory and experimental observation. A low injection flow rate was shown to lead to erosion of the pore-space concentrated at the face of the rock, whereas a high flow rate leads to wormhole formation.
Filling the Gaps – from Microscopic Pore Structures to Transport Properties in Shales, 2000
Transport properties in shales were investigated using experimental and computersimulation method... more Transport properties in shales were investigated using experimental and computersimulation methods. First, an experimental method based on a transient pressuredecay technique was further developed and used instead of classical Darcy core-flood methods. This has allowed measurement of the permeability of tight shale samples on much shorter time scales than by conventional methods. Second, molecular dynamics (MD) computer simulations were used to measure the diffusion coefficients of water and cations in a model clay sample. Measurements of the self-diffusion coefficient showed that the values increased with increasing water content. The results for Na-, Li-, and K-smectites are in satisfactory agreement with experimental and with other simulation results in the literature indicating that the clay interlayer space is an important route of transport for ions and water. The results also lend credibility to the correctness of the diffusion coefficients obtained from the current MD simulations.
We describe the ongoing development of lattice-Boltzmann (LB) computer simulation codes to study ... more We describe the ongoing development of lattice-Boltzmann (LB) computer simulation codes to study flow in porous media at the pore scale. LB simulations have evolved over the past decade and are now used as a tool to calculate both single-and multi-phase flow properties directly at the pore scale using X-ray Micro Tomography (XMT) pore space images. We will review the development of our codes to study flow in two-dimensional micro-models, viscous fingering, chemical reactions, hydrodynamic dispersion and non-Newtonian flow. In three dimensions, we have developed our codes to calculate the flow in XMT images of the pore space, for both single-and multi-phase flow, resulting in predictions of the permeability. Very recently, we have extended the multi-phase flow model to include surfactants for reduction of the interfacial tension and wettability alteration.
J Am Chem Soc 117 12608 12617, Dec 20, 1995
... Abstract: Monte Carlo molecular modeling simulations have been performed to investigate some ... more ... Abstract: Monte Carlo molecular modeling simulations have been performed to investigate some of the microscopic mechanisms underlying smectite clay swelling. ... 1983, 31, (13) Skipper, NT; Soper, AK; McConnell, JDC J. Chem. Phys. ...
Energy Fuels, 2011
ABSTRACT In this paper, we present preliminary calculations of the potential of mean force (PMF) ... more ABSTRACT In this paper, we present preliminary calculations of the potential of mean force (PMF) from molecular dynamics simulations of asphaltene molecules on a calcite surface. We calculate, for the first time, the PMF between an asphaltene molecule and the calcite surface directly by a constraint force method. The asphaltene molecule is obtained in a systematic way consistent with experimental information, using the quantitative molecular representation approach. The calcite surface has been defined as the {10.4} face, which is representative of the experimentally dominant crystal face. First, we calculate the time-averaged values of the constraint force as a function of the z distance between the asphaltene molecule and the calcite surface. We observe that, at a separation of 3 Å, the value of the force is positive, which corresponds to a repulsive interaction. At 3.5 Å, a minimum in the force is observed, corresponding to an attractive interaction. At longer distances, the average constraint force goes to zero, according to expectations. Then, we calculate the integral of the time-averaged constraint force as a function of the distance between the asphaltene molecule and the calcite surface. The difference between the minimum energy and the energy at large separations gives an estimate of the free energy of adsorption. In this case, the value of the free energy is of the order of 110 kJ/mol. This is a reasonable value for simulations in vacuo corresponding to an effective solvent.
The Journal of Physical Chemistry, 1994
Energy Fuels, Mar 3, 2008
The aggregation and deposition of colloidal asphaltene in reservoir rock is a significant problem... more The aggregation and deposition of colloidal asphaltene in reservoir rock is a significant problem in the oil industry. To obtain a fundamental understanding of this phenomenon, we have studied the deposition and aggregation of colloidal asphaltene in capillary flow by experiment and simulation. For the simulation, we have used the Stochastic Rotation Dynamics (SRD) method, in which the solvent hydrodynamics emerges from the collisions between the solvent particles, while the Brownian motion 2 emerges naturally from the interactions between the colloidal asphaltene particles and the solvent. The asphaltene colloids interact through a screened Coulomb potential. We vary the well depth ε and the flow rate v to obtain Pe flow >> 1 (hydrodynamic interactions dominate) and Re << 1 (Stokes flow). In the simulations, we impose a pressure drop over the capillary length, and measure the corresponding solvent flow rate. We observe that the transient solvent flow rate decreases when the asphaltene particles become more "sticky". For a well depth ε = 2 k B T, a monolayer deposits of on the capillary wall. With increasing well depth, the capillary becomes totally blocked. The clogging is transient for ε = 5 k B T, but appears to be permanent for ε = 10 -20 k B T. We compare our simulation results with flow experiments in glass capillaries, where we use extracted asphaltenes in toluene, reprecipitated with n-heptane. In the experiments, the dynamics of asphaltene precipitation and deposition were monitored in a slot capillary using optical microscopy under flow conditions similar to those used in the simulation. Maintaining a constant flow rate of 5 µL min -1 , we found that the pressure drop across the capillary first increased slowly, followed by a sharp increase, corresponding to a complete local blockage of the capillary.
Qatar Foundation Annual Research Conference, Nov 13, 2014
Physical Review E Statistical Physics Plasmas Fluids and Related Interdisciplinary Topics, Mar 1, 1997
The rheological properties of colloidal suspensions of spheres, rods, and disks have been studied... more The rheological properties of colloidal suspensions of spheres, rods, and disks have been studied using a mesoscopic simulation technique, known as dissipative particle dynamics (DPD). In DPD, a suspension is modeled as a system of large colloidal particles in a liquid of interacting point particles. For the calculation of hydrodynamic interactions, this method is computationally more efficient than conventional techniques using a continuum model for the solvent. Applying a steady-shear rate to the particulate suspensions, we have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol % suspension of spheres displays characteristic shear-thinning behavior as a function of increasing shear rate. The values for the high- and low-shear viscosity are in good agreement with experimental data. For higher particulate densities good results are obtained for the high-shear viscosity, although the viscosity at low-shear rates shows a dependence on the size of the suspended spheres that we attribute to finite size effects. Dilute suspensions of rods and disks show intrinsic viscosities which are in excellent agreement with theoretical predictions. For concentrated suspensions of both rods and disks, the viscosity increases with the third power of the volume fraction. We find the same scaling behavior as predicted by Doi and Edwards [M. Doi and S. F. Edwards, The Theory of Polymer Dynamics (Oxford University Press, New York, 1986)] for rod suspensions in the semidilute regime. The DPD simulation technique emerges as a useful tool for studying the rheology of particulate suspensions.
Physical Review E Statistical Nonlinear and Soft Matter Physics, Oct 1, 2004
We study the influence of shear flow on the formation of rings in a generic reversible polymer (F... more We study the influence of shear flow on the formation of rings in a generic reversible polymer (FENE-C) model, representative for wormlike micelles. Under equilibrium conditions, rings are dominating in dilute solutions, while linear chains are dominating in strongly overlapping and concentrated solutions. We find that shear flow induces a net shift of micellar mass from linear chains to rings. At the same time, the average aggregation size of linear chains is decreasing, while the average aggregation size of rings is increasing. We hypothesize that the increased abundance and size of rings are caused by a decreased entropy gain associated with ring opening under shear flow. Linear chains and rings are elongated in the flow direction and contracted in the gradient direction. This leaves an essentially two-dimensional free volume, which two newly created chain ends can explore after being disconnected. We study the ratio of ring and linear chain distribution functions to substantiate this hypothesis. Finally, we study the rheology and discuss how the observed increase of ring abundance can provide a positive feedback between strain and ring connectivity. Such a positive feedback can contribute to shear thickening behavior, observed in micellar solutions near the overlap concentration.
Advances in Water Resources
ABSTRACT
The Journal of Physical Chemistry, 1994
ABSTRACT
We present a LB study of the flow of single-phase non-Newtonian fluids, using a power law relatio... more We present a LB study of the flow of single-phase non-Newtonian fluids, using a power law relationship between the effective viscosity and the local shear rate. Channel flow experiments were carried out to measure the velocity profiles. The simulation results are found to be in good agreement with theory. We also report simulations of the flow of non-Newtonian fluids in a 2-D porous medium.
Gas clathrate hydrates are crystalline inclusion compounds in which a water host lattice encages ... more Gas clathrate hydrates are crystalline inclusion compounds in which a water host lattice encages small guest atoms or molecules. They are environmentally important as a potential means for CO 2 capture and also in terms of the vast oceanic reserves of methane hydrate, which represent both a potential source of fuel for the future and a potential threat in the event of methane escape to the atmosphere. They are important in the oil and gas industry because they form in and clog pipelines during oil and gas recovery. Modelling the phase equilibria of hydrate systems is, in some respects, a solved problem; accurate calculation of the hydrate locus for many simple and mixture gas hydrates has been possible for decades. At the core of many modelling techniques is the statistical-thermodynamic treatment of van der Waals and Platteuw [1], first published almost 50 years ago and generalised to mixtures by Parrish and Prausnitz [2] in the 1970s. However, an important constituent part of the ...
In this paper, we investigate pore scale models for the storage of CO2 in subterranean rock forma... more In this paper, we investigate pore scale models for the storage of CO2 in subterranean rock formations. Various mechanisms for storage and trapping have been proposed, including structural, solution, mineralisation and the immobilisation of CO2 by capillary trapping. Currently, the capillary trapping mechanism seems to be a suitable option, as it is a fast way to render the injected supercritical CO2 immobile. In addition, this trapping mechanism does not rely entirely upon the cap rock maintaining its integrity on geologic time scales. One important parameter for the success of capillary trapping is the residual saturation after CO2 injection in the formation. The saturation is determined by the wetting properties of the rock formation. Often, and particularly in carbonate reservoirs, the rock may be wetting to CO2, especially when injected under supercritical conditions. In this case, the mechanism of entry of CO2 into the pores of the rock matrix is determined by spontaneous imbi...
SPE Annual Technical Conference and Exhibition, 2013
ABSTRACT Not finding what you're looking for? Some of the OnePetro partner societies have... more ABSTRACT Not finding what you're looking for? Some of the OnePetro partner societies have developed subject- specific wikis that may help. PetroWiki PetroWiki was created from the seven volume Petroleum Engineering Handbook (PEH) published by the Society of Petroleum Engineers (SPE). The SEG Wiki The SEG Wiki is a useful collection of information for working geophysicists, educators, and students in the field of geophysics. The initial content has been derived from : Robert E. Sheriff's Encyclopedic Dictionary of Applied Geophysics, fourth edition.
Qatar Foundation Annual Research Forum Proceedings, 2012
Energy & Fuels, 2015
ABSTRACT The viscosity of heavy crude oils strongly affects their producibility and recovery from... more ABSTRACT The viscosity of heavy crude oils strongly affects their producibility and recovery from oil reservoirs. Thus, the viscosity of heavy crude oils with dissolved gases at different shear rates is valuable knowledge for heavy crude oil exploitation. However, most publications only present viscosity measurements at one specific shear rate, and only a few papers in the literature have reported the rheological measurements over a range of shear rates. In this study, viscosity measurements of CO2-saturated heavy crude oils were performed as a function of the shear rate, at a temperature of 25 °C and pressures up to 220 bar. The experimental apparatus is a unique circulation system, which is able to measure the viscosity of CO2-saturated mixtures. A novel high-pressure rheometer with a flow-through Couette geometry was developed to measure the viscosity at a range of shear rates. The experimental results show that the addition of CO2 to heavy crude oil at the given temperature and pressures reduces the viscosity significantly, but the pressure dependence of the mixture viscosity changes at the phase transition of the CO2-rich phase. A modified Arrhenius equation, accounting for the effect of CO2 composition on viscosity, is applied to correlate the viscosity data.
Lecture Notes in Computer Science, 2003
An experimental study of gemini surfactants with different types of spacer has been reported in a... more An experimental study of gemini surfactants with different types of spacer has been reported in a number of papers [1,2,3]. So-called gemini or bis-surfactants are formed by two novel surface active molecules connected via a flexible or rigid linkage between the hydrophilic head ...