International Journal of Electrical Power & Energy Systems, 2021
We research effects on the electricity market of countries surrounding the North Sea after a prop... more We research effects on the electricity market of countries surrounding the North Sea after a proposed offshore wind park in the Dogger Bank area of the North Sea has been constructed. Interconnection and generation distribution are analysed separately. The supply price of electricity for each country is calculated by a linear regression analysis to simulate the supply price for higher or lower supply. The model uses the coupling of one supply with one receiver country. Linear modelling of the electricity market combines the results for each objective to find a final state for the market. Using the historic market and weather data for 2016, the results from interconnection show an average generated value of 0.275 [M€/hour] and 82.1 [GW] of average energy flow through the hub. The results of this interconnection between the countries bring between − 26% and +11% change on average electricity prices. For hub generation added in, we found an average generated value of 0.573 [M€/hour] and an average price drop of 5% for each country for an average wind power generation of 6.3 [GW] at the hub. The results show that interconnecting the similarly sized electricity markets i.e. Great Britain and Germany & the Netherlands and Denmark, where one has a higher renewable share, would bring the most price stabilization between the two as well as generate the most financial return.
Journal of Petroleum Exploration and Production Technology, 2018
A novel natural cellulose material ("biofibre") suspension in water has potential both for enhanc... more A novel natural cellulose material ("biofibre") suspension in water has potential both for enhanced oil recovery and proppant placement during fracturing in tight reservoirs. We analyse the different carrying mechanisms of biofibre against those of a cross-linked guar benchmark. Three viscosity determination methods have been applied that are relevant to the different applications. Non-Newtonian, shear-thinning effects with viscoelastic enhancement have been observed. These results are compared to the viscosity in a falling ball rheometer as well as in pressure-driven flow through capillaries and conduits. The results indicate that viscosity can be tuned to automatically adjust to the desired flow conditions in the reservoir to provide optimal behaviour for each application. Keywords Fractures • Reservoirs • Fibre suspensions List of symbols A Surface area d Diameter ball D Diameter capillary K Permeability L Length N Crowding number n Flow behaviour index P Pressure Q Flow rate RF Resistance factor u Velocity t Terminal velocity Greek α Comparative parameteṙ Shear ratē Average shear rate Λ Mass fraction ω Fibre coarseness Characteristic fluid timė Angular frequency Volume fraction Viscosity Subscripts 0 Zero shear b Shear rate Cc Couette cell f Biofibre fl Fluid fb Falling ball fci Flow consistency index M Mass t Terminal Paper for submission to J. Petrol. Explor. Prod. Tech.
Journal of Petroleum Science and Engineering, 2018
Fluid loss through natural fractures in oil reservoirs can be overcome using flow induced viscoel... more Fluid loss through natural fractures in oil reservoirs can be overcome using flow induced viscoelastic surfactant (FIVES) solutions. Single phase tests show higher flow resistance in fractures compared to matrix. This reduces the fluid lost through the fracture. During decane displacement, the amount of fluid lost through the fracture is lowered due to this increased local flow resistance. Improved recovery is obtained and the pore volume injected at breakthrough is reduced from 2.5 PV to ca. 1.0 PV. These results translate to a prolonged economic lifespan of a fractured heterogeneous reservoir and a significant reduction in post-processing costs.
In-service degradation of a pipe section is monitored in real time with torsional guided waves wh... more In-service degradation of a pipe section is monitored in real time with torsional guided waves which can resolve 5% damage to the internal wall. We use a single permanently installed source–receiver pair as opposed to the current state-of-the-art sensor rings. There is no baseline subtraction requirement as a single reflection coefficient is derived by internal referencing of the time trace. Even with continuously operating pump vibration, there is enough acoustic signal for confident damage localization. Since pipelines wear out gradually in industrial installations, the acoustic footprint is similar to that previously determined in periodically damaged pipes. The reflective method can thus be applied successfully to monitor structural health in industrial pipelines during operation as opposed to the current state-of-the-art guided wave inspection approaches using near-weld reflection techniques along with disassembled and re-assembled sensor rings.
Journal of Unconventional Oil and Gas Resources, 2016
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
The location and extent of damage in a pipe can be remotely determined from weld and internal dam... more The location and extent of damage in a pipe can be remotely determined from weld and internal damage reflections using a single acoustic emitter/sensor pair. The use of normalised reflections yields single numbers enabling long distance data collection techniques such as wireless hopping. The attenuation is twice as high for opposite inner and outer fluids (whether air and water, or water and air) as compared to identical inner and outer fluids. The absolute recorded signals in the water-filled pipe are attenuated by a factor two compared to the empty pipe. The axial length of detection is reduced by a half. The reduction of >90% in sensors and the longer axial detection (>10× current state-of-theart-technology) means that permanent fixed sensor pairs for whole pipelines are on the horizon of possibility. The greatest advantage is envisioned in submersed pipelines.
Axial pipeline defects are detectable from torsional guided wave reflections through 90 deg elbow... more Axial pipeline defects are detectable from torsional guided wave reflections through 90 deg elbows. This paper demonstrates that detection of localized damage in carbon steel pipes with a so-called standard long and very long radius elbow is possible using a single permanently installed source–receiver pair. We use dispersion imaging to determine why this is not possible in a short radius elbow pipe. Although the remote damage is detected in a standard short radius bend pipe, there is not enough signal to detect localized damage. Since pipeline bends are normally of at least standard long radius, the acoustical behavior is similar to that previously determined in straight pipes. The reflective method can thus be applied fruitfully to monitor structural health beyond industrial pipeline bends.
Journal of Petroleum Exploration and Production Technology, 2016
Viscoelastic solutions are notoriously sensitive to temperature and ionic strength. In order to b... more Viscoelastic solutions are notoriously sensitive to temperature and ionic strength. In order to be applicable for use in oil reservoirs, they need to be resilient to higher temperatures as well as to saline content. We define the essential characteristics required. Refractory properties obtained under Couette testing do not necessarily provide the same performance under pressure-driven flow. Nonetheless, it is possible to formulate solutions which clearly indicate that subsurface application is practicable. We show examples where salinity enables significantly enhanced viscoelasticity above ambient temperatures. Keywords Viscoelastic surfactants (VES) Á Shear-induced structures (SIS) Á Water floods Á Oil recovery Á Porous media Á Channel flow Á Temperature resistance Á Salinity resilience Abbreviations RF Retardation factor SIS Shear-induced structure SRF Size selective retardation factor VCR Viscosity contrast ratio VES Viscoelastic surfactant VR Velocity retardation List of symbols L Fracture length p Pressure Q Fluid flow RF Resistance factor T Temperature u Darcy velocity W Parameter of the fracture width (i.e. smallest wall to wall distance) Greek symbols _ c Shear rate j Permeability l Shear viscosity from rheometer Subscripts a Additive app Apparent bf Base fluid c Critical m Maximum l Large s Small w Wall 0 Zero shear & Boaz van der Plas
Journal of Petroleum Exploration and Production Technology, 2017
We determine the chemical changes associated with viscosity reduction when heavy oil is cracked i... more We determine the chemical changes associated with viscosity reduction when heavy oil is cracked in subcritical water. The viscosity reduction has a temperature threshold for onset of 290°C-this suggests an enhanced acid cracking regime associated with the maximisation of water dissociation at these conditions aided by the already increased solubility. The mean molecular weight is reduced by nearly 50%. Oxygen and sulphur are reduced by about half of this-either by expelled gas effluent (H 2 S) or by conversion into mono-aromatic base sulphur-containing structures. The amount of lower branched paraffins is increased.
Journal of Petroleum Science and Engineering, 2016
A subclass of viscoelastic surfactant fluids are investigated as flow-dependent proppant carrying... more A subclass of viscoelastic surfactant fluids are investigated as flow-dependent proppant carrying fluids. Shear-induced structure networks have the potential to eliminate the need for cross linkers and viscosity breakers associated with traditional fluids because they shear-thicken and shear-thin depending on the fluid pump rates in the fracture. Particle tracking velocimetry is used to visualize proppant settling velocity inside a fracture flow cell. We show that settling velocities in high shear flows are reduced by a factor 20 compared to settling in low shear ones and fluids at rest. Couette cell and oscillatory rheometry are used to investigate the induced viscoelasticity. The critical shear rate required for fluid thickening and the succeeding viscosity contrast ratio determine the extra proppant carrying capacity.
Torsional wave dispersion and attenuation in an open empty welded pipe are determined from a mult... more Torsional wave dispersion and attenuation in an open empty welded pipe are determined from a multi-receiver position reflection experiment. The fundamental torsional wave is dominantly reflected at the free end and the converted non-axisymmetric flexural modes are naturally attenuated. The resulting phase velocity contours are in agreement with theoretical predictions. The transmission losses are quantified and compared to those reflective elements associated with end and weld reflection. At any reflective node, the incident wave is split between back and forward preserved mode scattering (''reflec tion/transmission"), conversion to other modes plus energy lost by absorption. The ratios for each element are quantified.
Viscoelastic surfactant solutions increase oil recovery by selectively modifying the viscosity of... more Viscoelastic surfactant solutions increase oil recovery by selectively modifying the viscosity of the injected displacing fluid in different zones of the reservoir. We demonstrate that flow 3 resistance in high permeability zones is increased whereas no significant change in viscosity 4 occurs in low permeability zones. This greatly reduces injected fluid losses via the high 5 permeability route. In two phase flow in sandstones, recovery increases by about 25%. Efficiency 6 also increases by a factor of 3 as shown by the large reduction in injected volume at 7 breakthrough. Consequently less fluid is lost through high permeability thief zones. Recovery is 8 increased in carbonates as well but the efficiency is depleted due to apparent changes in wetting. 9 The reduction in injected fluid before breakthrough has the potential to prolong the economical 10 lifespan of water wet reservoirs.
Abstract Fluids displaying flow induced viscoelasticity are tested for proppant placement and flo... more Abstract Fluids displaying flow induced viscoelasticity are tested for proppant placement and flow back. The viscosity is self-regulating and obviates the need for viscosifiers and breakers. The flow induced viscoelasticity degrades at higher flow rates enabling good injectivity. Particle tracking velocimetry is performed to study the influence of flow rate on the particle settling under different flow regimes. These tests show that above a critical flow rate particles are maintained in suspension and settle with a constant velocity giving the fluid an apparent viscosity up to 200 mPa s compared to a zero-shear viscosity of 2 mPa s. During flowback in porous proppant packs the fluid has a low flow resistance with a viscosity comparable to its zero-sheared state. Pack permeability is retained after flowback of the fluid thereby resulting in optimum fracture clean-up.
Olefins are highly nonlinear octane blenders so that standard GC analyses are poor predictors of ... more Olefins are highly nonlinear octane blenders so that standard GC analyses are poor predictors of blend quality. Engine rating is the only way of measuring olefin octane number nonlinearity. It is thus not possible to rapidly assess the quality of the product obtained from an olefin-producing process-stream. An analysis of the kinetics of olefin combustion in terms of mechanisms for depleting active radicals identifies hydrogen abstraction from an allylic carbon as a factor that increases resistance to knock. We can use NMR to find the allylic hydrogen fraction in a sample, and we show that this correlates with mixtures of olefins obtained during processing of the typical gaseous products of a cat-cracked stream. This simple application of NMR has the advantages of quantitatively probing octane number on a sound chemical criterion, as well as the fact that it is fast and requires only small amounts of sample so that process optimization for olefin quality on a small-scale microflow reactor can easily be carried out.
Multi-mode dispersion imaging shows that pure dispersion-free torsional waves are reflected at a ... more Multi-mode dispersion imaging shows that pure dispersion-free torsional waves are reflected at a pipe end and flexural wave modes are suppressed. This effect can be used to locate and assess internal damage. The end reflection coefficient of this single propagating mode decreases with increasing wear. The pipe damage is located from the travel time of the torsional wave component reflected from the damage point.
Journal of Petroleum Exploration and Production Technology, 2015
The use of viscoelastic sweep improvers to overcome injected fluid diversion is assessed at the l... more The use of viscoelastic sweep improvers to overcome injected fluid diversion is assessed at the low pressure gradients associated with secondary oil production. The flow evolves from Newtonian to non-Newtonian behavior with increasing pressure gradient. Additive concentration determines this transition and controls the effectiveness of selective retardation. This is demonstrated in an experimental simulation of parallel flow in two core samples of different permeabilities. Even at pressure gradients lower than 1.0 bar/m channeling can effectively be reduced and early water breakthrough delayed. This has the potential to greatly increase ultimate oil recovery. Keywords Enhanced oil recovery Á Viscoelastic surfactants Á Channeling List of symbols L Length core (m) n Layer number DP Pressure drop (Pa) R Flow rate ratio u Darcy velocity (m/s) Dx Length porous media (m) x Position flow front (m) c Shear rate (1/s) g Sweep efficiency j Permeability (m 2) K Resistance factor l Viscosity (Pa s) Subscripts 0 Base fluid app Macroscopic/apparent b Breakthrough layer c Critical f Flow rate hi High permeability lo Low permeability n Layer n & Joris van Santvoort
International Journal of Electrical Power & Energy Systems, 2021
We research effects on the electricity market of countries surrounding the North Sea after a prop... more We research effects on the electricity market of countries surrounding the North Sea after a proposed offshore wind park in the Dogger Bank area of the North Sea has been constructed. Interconnection and generation distribution are analysed separately. The supply price of electricity for each country is calculated by a linear regression analysis to simulate the supply price for higher or lower supply. The model uses the coupling of one supply with one receiver country. Linear modelling of the electricity market combines the results for each objective to find a final state for the market. Using the historic market and weather data for 2016, the results from interconnection show an average generated value of 0.275 [M€/hour] and 82.1 [GW] of average energy flow through the hub. The results of this interconnection between the countries bring between − 26% and +11% change on average electricity prices. For hub generation added in, we found an average generated value of 0.573 [M€/hour] and an average price drop of 5% for each country for an average wind power generation of 6.3 [GW] at the hub. The results show that interconnecting the similarly sized electricity markets i.e. Great Britain and Germany & the Netherlands and Denmark, where one has a higher renewable share, would bring the most price stabilization between the two as well as generate the most financial return.
Journal of Petroleum Exploration and Production Technology, 2018
A novel natural cellulose material ("biofibre") suspension in water has potential both for enhanc... more A novel natural cellulose material ("biofibre") suspension in water has potential both for enhanced oil recovery and proppant placement during fracturing in tight reservoirs. We analyse the different carrying mechanisms of biofibre against those of a cross-linked guar benchmark. Three viscosity determination methods have been applied that are relevant to the different applications. Non-Newtonian, shear-thinning effects with viscoelastic enhancement have been observed. These results are compared to the viscosity in a falling ball rheometer as well as in pressure-driven flow through capillaries and conduits. The results indicate that viscosity can be tuned to automatically adjust to the desired flow conditions in the reservoir to provide optimal behaviour for each application. Keywords Fractures • Reservoirs • Fibre suspensions List of symbols A Surface area d Diameter ball D Diameter capillary K Permeability L Length N Crowding number n Flow behaviour index P Pressure Q Flow rate RF Resistance factor u Velocity t Terminal velocity Greek α Comparative parameteṙ Shear ratē Average shear rate Λ Mass fraction ω Fibre coarseness Characteristic fluid timė Angular frequency Volume fraction Viscosity Subscripts 0 Zero shear b Shear rate Cc Couette cell f Biofibre fl Fluid fb Falling ball fci Flow consistency index M Mass t Terminal Paper for submission to J. Petrol. Explor. Prod. Tech.
Journal of Petroleum Science and Engineering, 2018
Fluid loss through natural fractures in oil reservoirs can be overcome using flow induced viscoel... more Fluid loss through natural fractures in oil reservoirs can be overcome using flow induced viscoelastic surfactant (FIVES) solutions. Single phase tests show higher flow resistance in fractures compared to matrix. This reduces the fluid lost through the fracture. During decane displacement, the amount of fluid lost through the fracture is lowered due to this increased local flow resistance. Improved recovery is obtained and the pore volume injected at breakthrough is reduced from 2.5 PV to ca. 1.0 PV. These results translate to a prolonged economic lifespan of a fractured heterogeneous reservoir and a significant reduction in post-processing costs.
In-service degradation of a pipe section is monitored in real time with torsional guided waves wh... more In-service degradation of a pipe section is monitored in real time with torsional guided waves which can resolve 5% damage to the internal wall. We use a single permanently installed source–receiver pair as opposed to the current state-of-the-art sensor rings. There is no baseline subtraction requirement as a single reflection coefficient is derived by internal referencing of the time trace. Even with continuously operating pump vibration, there is enough acoustic signal for confident damage localization. Since pipelines wear out gradually in industrial installations, the acoustic footprint is similar to that previously determined in periodically damaged pipes. The reflective method can thus be applied successfully to monitor structural health in industrial pipelines during operation as opposed to the current state-of-the-art guided wave inspection approaches using near-weld reflection techniques along with disassembled and re-assembled sensor rings.
Journal of Unconventional Oil and Gas Resources, 2016
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
The location and extent of damage in a pipe can be remotely determined from weld and internal dam... more The location and extent of damage in a pipe can be remotely determined from weld and internal damage reflections using a single acoustic emitter/sensor pair. The use of normalised reflections yields single numbers enabling long distance data collection techniques such as wireless hopping. The attenuation is twice as high for opposite inner and outer fluids (whether air and water, or water and air) as compared to identical inner and outer fluids. The absolute recorded signals in the water-filled pipe are attenuated by a factor two compared to the empty pipe. The axial length of detection is reduced by a half. The reduction of >90% in sensors and the longer axial detection (>10× current state-of-theart-technology) means that permanent fixed sensor pairs for whole pipelines are on the horizon of possibility. The greatest advantage is envisioned in submersed pipelines.
Axial pipeline defects are detectable from torsional guided wave reflections through 90 deg elbow... more Axial pipeline defects are detectable from torsional guided wave reflections through 90 deg elbows. This paper demonstrates that detection of localized damage in carbon steel pipes with a so-called standard long and very long radius elbow is possible using a single permanently installed source–receiver pair. We use dispersion imaging to determine why this is not possible in a short radius elbow pipe. Although the remote damage is detected in a standard short radius bend pipe, there is not enough signal to detect localized damage. Since pipeline bends are normally of at least standard long radius, the acoustical behavior is similar to that previously determined in straight pipes. The reflective method can thus be applied fruitfully to monitor structural health beyond industrial pipeline bends.
Journal of Petroleum Exploration and Production Technology, 2016
Viscoelastic solutions are notoriously sensitive to temperature and ionic strength. In order to b... more Viscoelastic solutions are notoriously sensitive to temperature and ionic strength. In order to be applicable for use in oil reservoirs, they need to be resilient to higher temperatures as well as to saline content. We define the essential characteristics required. Refractory properties obtained under Couette testing do not necessarily provide the same performance under pressure-driven flow. Nonetheless, it is possible to formulate solutions which clearly indicate that subsurface application is practicable. We show examples where salinity enables significantly enhanced viscoelasticity above ambient temperatures. Keywords Viscoelastic surfactants (VES) Á Shear-induced structures (SIS) Á Water floods Á Oil recovery Á Porous media Á Channel flow Á Temperature resistance Á Salinity resilience Abbreviations RF Retardation factor SIS Shear-induced structure SRF Size selective retardation factor VCR Viscosity contrast ratio VES Viscoelastic surfactant VR Velocity retardation List of symbols L Fracture length p Pressure Q Fluid flow RF Resistance factor T Temperature u Darcy velocity W Parameter of the fracture width (i.e. smallest wall to wall distance) Greek symbols _ c Shear rate j Permeability l Shear viscosity from rheometer Subscripts a Additive app Apparent bf Base fluid c Critical m Maximum l Large s Small w Wall 0 Zero shear & Boaz van der Plas
Journal of Petroleum Exploration and Production Technology, 2017
We determine the chemical changes associated with viscosity reduction when heavy oil is cracked i... more We determine the chemical changes associated with viscosity reduction when heavy oil is cracked in subcritical water. The viscosity reduction has a temperature threshold for onset of 290°C-this suggests an enhanced acid cracking regime associated with the maximisation of water dissociation at these conditions aided by the already increased solubility. The mean molecular weight is reduced by nearly 50%. Oxygen and sulphur are reduced by about half of this-either by expelled gas effluent (H 2 S) or by conversion into mono-aromatic base sulphur-containing structures. The amount of lower branched paraffins is increased.
Journal of Petroleum Science and Engineering, 2016
A subclass of viscoelastic surfactant fluids are investigated as flow-dependent proppant carrying... more A subclass of viscoelastic surfactant fluids are investigated as flow-dependent proppant carrying fluids. Shear-induced structure networks have the potential to eliminate the need for cross linkers and viscosity breakers associated with traditional fluids because they shear-thicken and shear-thin depending on the fluid pump rates in the fracture. Particle tracking velocimetry is used to visualize proppant settling velocity inside a fracture flow cell. We show that settling velocities in high shear flows are reduced by a factor 20 compared to settling in low shear ones and fluids at rest. Couette cell and oscillatory rheometry are used to investigate the induced viscoelasticity. The critical shear rate required for fluid thickening and the succeeding viscosity contrast ratio determine the extra proppant carrying capacity.
Torsional wave dispersion and attenuation in an open empty welded pipe are determined from a mult... more Torsional wave dispersion and attenuation in an open empty welded pipe are determined from a multi-receiver position reflection experiment. The fundamental torsional wave is dominantly reflected at the free end and the converted non-axisymmetric flexural modes are naturally attenuated. The resulting phase velocity contours are in agreement with theoretical predictions. The transmission losses are quantified and compared to those reflective elements associated with end and weld reflection. At any reflective node, the incident wave is split between back and forward preserved mode scattering (''reflec tion/transmission"), conversion to other modes plus energy lost by absorption. The ratios for each element are quantified.
Viscoelastic surfactant solutions increase oil recovery by selectively modifying the viscosity of... more Viscoelastic surfactant solutions increase oil recovery by selectively modifying the viscosity of the injected displacing fluid in different zones of the reservoir. We demonstrate that flow 3 resistance in high permeability zones is increased whereas no significant change in viscosity 4 occurs in low permeability zones. This greatly reduces injected fluid losses via the high 5 permeability route. In two phase flow in sandstones, recovery increases by about 25%. Efficiency 6 also increases by a factor of 3 as shown by the large reduction in injected volume at 7 breakthrough. Consequently less fluid is lost through high permeability thief zones. Recovery is 8 increased in carbonates as well but the efficiency is depleted due to apparent changes in wetting. 9 The reduction in injected fluid before breakthrough has the potential to prolong the economical 10 lifespan of water wet reservoirs.
Abstract Fluids displaying flow induced viscoelasticity are tested for proppant placement and flo... more Abstract Fluids displaying flow induced viscoelasticity are tested for proppant placement and flow back. The viscosity is self-regulating and obviates the need for viscosifiers and breakers. The flow induced viscoelasticity degrades at higher flow rates enabling good injectivity. Particle tracking velocimetry is performed to study the influence of flow rate on the particle settling under different flow regimes. These tests show that above a critical flow rate particles are maintained in suspension and settle with a constant velocity giving the fluid an apparent viscosity up to 200 mPa s compared to a zero-shear viscosity of 2 mPa s. During flowback in porous proppant packs the fluid has a low flow resistance with a viscosity comparable to its zero-sheared state. Pack permeability is retained after flowback of the fluid thereby resulting in optimum fracture clean-up.
Olefins are highly nonlinear octane blenders so that standard GC analyses are poor predictors of ... more Olefins are highly nonlinear octane blenders so that standard GC analyses are poor predictors of blend quality. Engine rating is the only way of measuring olefin octane number nonlinearity. It is thus not possible to rapidly assess the quality of the product obtained from an olefin-producing process-stream. An analysis of the kinetics of olefin combustion in terms of mechanisms for depleting active radicals identifies hydrogen abstraction from an allylic carbon as a factor that increases resistance to knock. We can use NMR to find the allylic hydrogen fraction in a sample, and we show that this correlates with mixtures of olefins obtained during processing of the typical gaseous products of a cat-cracked stream. This simple application of NMR has the advantages of quantitatively probing octane number on a sound chemical criterion, as well as the fact that it is fast and requires only small amounts of sample so that process optimization for olefin quality on a small-scale microflow reactor can easily be carried out.
Multi-mode dispersion imaging shows that pure dispersion-free torsional waves are reflected at a ... more Multi-mode dispersion imaging shows that pure dispersion-free torsional waves are reflected at a pipe end and flexural wave modes are suppressed. This effect can be used to locate and assess internal damage. The end reflection coefficient of this single propagating mode decreases with increasing wear. The pipe damage is located from the travel time of the torsional wave component reflected from the damage point.
Journal of Petroleum Exploration and Production Technology, 2015
The use of viscoelastic sweep improvers to overcome injected fluid diversion is assessed at the l... more The use of viscoelastic sweep improvers to overcome injected fluid diversion is assessed at the low pressure gradients associated with secondary oil production. The flow evolves from Newtonian to non-Newtonian behavior with increasing pressure gradient. Additive concentration determines this transition and controls the effectiveness of selective retardation. This is demonstrated in an experimental simulation of parallel flow in two core samples of different permeabilities. Even at pressure gradients lower than 1.0 bar/m channeling can effectively be reduced and early water breakthrough delayed. This has the potential to greatly increase ultimate oil recovery. Keywords Enhanced oil recovery Á Viscoelastic surfactants Á Channeling List of symbols L Length core (m) n Layer number DP Pressure drop (Pa) R Flow rate ratio u Darcy velocity (m/s) Dx Length porous media (m) x Position flow front (m) c Shear rate (1/s) g Sweep efficiency j Permeability (m 2) K Resistance factor l Viscosity (Pa s) Subscripts 0 Base fluid app Macroscopic/apparent b Breakthrough layer c Critical f Flow rate hi High permeability lo Low permeability n Layer n & Joris van Santvoort
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