Micro X-ray fluorescence produces elemental images at μm resolution and offers insight into rock ... more Micro X-ray fluorescence produces elemental images at μm resolution and offers insight into rock properties such as mineral composition and structure. This study presents a porosity mapping method using microfluidic devices and real-rock models.
Molecular diffusion of gases in heavy oils is one of the most important physical parameter govern... more Molecular diffusion of gases in heavy oils is one of the most important physical parameter governing cold production processes such as solution gas drive or Vapex. Indeed, the way bubbles are able to grow by diffusion will have a direct impact on gas mobilization and consequently on oil recovery. Furthermore, the importance of this parameter is emphasized by the very low gas availability characterizing extra heavy oils. Surprisingly, publications of experimental data concerning gas diffusivity in heavy oils are relatively rare. Furthermore, published values can vary by different orders of magnitude. This is probably due to the fact that this kind of measurement is quite tricky. Indeed gas leakages in high pressure cells could be in the same order of magnitude than gas diffusion in oil. To study very viscous oil (extra heavy oils), corresponding to very low diffusivity, it is thus necessary to carefully analyze the obtained results. The aim of this work is to characterize experimental fickian diffusivity of methane in heavy oils using two different concepts in order to be able to validate the experimental results. In this paper we present the two different methods (thermophysics and analytical) we have settled. Experimental results clearly indicate that diffusivity in extra heavy oils is lower than usually considered for ‘conventional’ oil. From various experimental results we also propose a first mathematical model to simulate the influence of temperature on gas diffusivity.
Despite the advantageous resolution of electron tomography (ET), reconstruction of three-dimensio... more Despite the advantageous resolution of electron tomography (ET), reconstruction of three-dimensional (3D) images from multiple two-dimensional (2D) projections presents several challenges, including small signal-to-noise ratios, and a limited projection range. This study evaluates the capabilities of ET for thin sections of shale, a complex nanoporous medium. A numerical phantom with 1.24 nm pixel size is constructed based on the tomographic reconstruction of a Barnett shale. A dataset of 2D projection images is numerically generated from the 3D phantom and studied over a range of conditions. First, common reconstruction techniques are used to reconstruct the shale structure. The reconstruction uncertainty is quantified by comparing overall values of storage and transport metrics, as well as the misclassification of pore voxels compared to the phantom. We then select the most robust reconstruction technique and we vary the acquisition conditions to quantify the effect of artifacts. ...
Estimating porous media properties is a vital component of geosciences and the physics of porous ... more Estimating porous media properties is a vital component of geosciences and the physics of porous media. Until now, imaging techniques have focused on methodologies to match image-derived flows or geomechanical parameters with experimentally identified values. Less emphasis has been placed on the compromise between image processing techniques and the consequences on topological and morphological characteristics and on computed properties such as permeability. The effects of some of the most popular image processing techniques (filtering and segmentation) available in open source on 3D X-ray Microscopy (micro-XRM) images are qualitatively and quantitatively discussed. We observe the impacts of various filters such as erosion-dilation and compare the efficiency of Otsu’s method of thresholding and the machine-learning-based software Ilastik for segmentation.
Inside asphaltene aggregates in crude oils, the adsorbed hydrocarbons exist in the packed periphe... more Inside asphaltene aggregates in crude oils, the adsorbed hydrocarbons exist in the packed periphery while the occluded hydrocarbons exist inside the core of the asphaltene structures. Occluded hydrocarbons may be well protected from secondary alteration events in the reservoir due ...
In the crude oil, the other fractions such as hydrocarbons could be adsorbed and/or occluded insi... more In the crude oil, the other fractions such as hydrocarbons could be adsorbed and/or occluded inside asphaltene structures. In this work, the deuterated compound n-C 20 D 42 has been used to simulate the adsorption/occlusion characteristics of asphaltene in toluene solution. Based on the highly polydispersed structures of asphaltenes, the experimental results indicate that the adsorbed hydrocarbons could be exchanged with the outside bulk phase, whereas the occluded ones inside the core of asphaltenes could not be exchanged. These results suggest that substantial microporous units exist inside asphaltene structures, and these structural units are suitable to adsorb and occlude the other fractions in the crude oil. The carbon number of the occluded hydrocarbons could be up to C 40 , and the weight could be more than 0.5%, based on the initial asphaltene weight. The adsorption should occur at the periphery of asphaltene aggregates (the loosely packed ones), and then they are liable to be exchanged with the outside bulk phase. If the asphaltene molecule is large enough, the occlusion could occur at the asphaltene molecular level. However, this type of occlusion perhaps just occurs inside asphaltene aggregates (the close aggregating ones); if this is the case, this type of asphaltene aggregate should be considered to be the stable unit in toluene solution, and then the occluded hydrocarbons could not be exchanged with the bulk phase. Regarding the adsorption/occlusion properties of asphaltenes, the aforementioned results should be valid, even extrapolated into the crude oil reservoir system.
Being the heaviest fraction of crude oils, asphaltenes are liable to aggregate, and other molecul... more Being the heaviest fraction of crude oils, asphaltenes are liable to aggregate, and other molecules in the oils can be steadily adsorbed onto, and even occluded inside the macromolecular structures of the asphaltenes. These occluded compounds inside the asphaltenes can survive over geological time in oil reservoirs owing to effective protection by the macromolecular structures of the asphaltenes. The asphaltenes of a crude oil (ZG31) from the central Tarim Basin, NW China, were hierarchically degraded by increasing the amount of H 2 O 2 /CH 3 COOH to release the occluded compounds. Besides the common components, series of even numbered n-alk-1-enes and 3-ethylalkanes were detected among the occluded compounds. Comparison of the biomarker distributions and the compound-specific C isotopic results between the compounds from the maltenes and those from the occluded fraction, the ZG31 reservoir was suggested to have been charged multiple times, with different charges being derived from different strata of source rocks.
Some hydrocarbons occluded inside asphaltene structures can be considered to be “original oil”, a... more Some hydrocarbons occluded inside asphaltene structures can be considered to be “original oil”, and are very important especially for severely post-altered crude oil in related geochemical studies such as oil/oil, oil/source correlation. The use of oxidising reagents could properly release these occluded hydrocarbons, and make possible direct study of these compounds without interference from the segments chemically bonded to the
The spinning bubble tensiometer technique provides a handy tool to measure the potential at the a... more The spinning bubble tensiometer technique provides a handy tool to measure the potential at the air-water surface. The method is used to estimate the variation of the potential at the surface of aqueous solutions containing binary mixtures of surfactants (anionic, nonionic, and fluorocarbon anionic). The evidence on molecular interactions at the air-water surface is compared with the information deduced from the critical micelle concentration experimental data.
The zeta potentials of a single N2 bubble in near neutral aqueous solutions of 10–5 to 10–2 M NaF... more The zeta potentials of a single N2 bubble in near neutral aqueous solutions of 10–5 to 10–2 M NaF have been measured with a rotating cell zetameter. The zeta potentials in the NaF solutions are slightly more negative than those of comparable NaI concentrations. A simple interpretation of this observation is that the small size of the fluoride ion leads to its stronger adsorption at the interface, despite its smaller dielectric decrement. This would not be consistent with independent electrospray results from 100 µM solutions that bromide ion is less strongly adsorbed than iodide ion, i.e. that surface affinity increases with ion size. An alternative interpretation of the fluoride experiment is that the fluoride surface affinity is the consequence of stronger ion pairing with the NaOH that spontaneously forms at the interface.
Expanding the electrical double layer of minerals through low-salinity brine injection has been s... more Expanding the electrical double layer of minerals through low-salinity brine injection has been suggested as a possible enhanced oil recovery mechanism. To investigate this theory, we measured the ζ potential of different minerals, namely, sands from Fontainebleau, Ottawa, and Landes, a sample from a sandstone outcrop, and one crude oil. ζ-potential measurements can be used to quantify the surface charges of materials; therefore, experiments associated with this technique were performed to predict the behavior of repulsion or attraction between materials in different salinity and pH conditions. We showed that there is no significant difference between the ζ potentials of the tested materials. We did, however, observe that the different sands and sandstone have dissimilar adhesion behaviors. No correlation was found between the electrokinetic measurements performed on the minerals and their response to crude oil introduced into the system. The adhesion results obtained for the Landes and Ottawa sands were ...
Micro X-ray fluorescence produces elemental images at μm resolution and offers insight into rock ... more Micro X-ray fluorescence produces elemental images at μm resolution and offers insight into rock properties such as mineral composition and structure. This study presents a porosity mapping method using microfluidic devices and real-rock models.
Molecular diffusion of gases in heavy oils is one of the most important physical parameter govern... more Molecular diffusion of gases in heavy oils is one of the most important physical parameter governing cold production processes such as solution gas drive or Vapex. Indeed, the way bubbles are able to grow by diffusion will have a direct impact on gas mobilization and consequently on oil recovery. Furthermore, the importance of this parameter is emphasized by the very low gas availability characterizing extra heavy oils. Surprisingly, publications of experimental data concerning gas diffusivity in heavy oils are relatively rare. Furthermore, published values can vary by different orders of magnitude. This is probably due to the fact that this kind of measurement is quite tricky. Indeed gas leakages in high pressure cells could be in the same order of magnitude than gas diffusion in oil. To study very viscous oil (extra heavy oils), corresponding to very low diffusivity, it is thus necessary to carefully analyze the obtained results. The aim of this work is to characterize experimental fickian diffusivity of methane in heavy oils using two different concepts in order to be able to validate the experimental results. In this paper we present the two different methods (thermophysics and analytical) we have settled. Experimental results clearly indicate that diffusivity in extra heavy oils is lower than usually considered for ‘conventional’ oil. From various experimental results we also propose a first mathematical model to simulate the influence of temperature on gas diffusivity.
Despite the advantageous resolution of electron tomography (ET), reconstruction of three-dimensio... more Despite the advantageous resolution of electron tomography (ET), reconstruction of three-dimensional (3D) images from multiple two-dimensional (2D) projections presents several challenges, including small signal-to-noise ratios, and a limited projection range. This study evaluates the capabilities of ET for thin sections of shale, a complex nanoporous medium. A numerical phantom with 1.24 nm pixel size is constructed based on the tomographic reconstruction of a Barnett shale. A dataset of 2D projection images is numerically generated from the 3D phantom and studied over a range of conditions. First, common reconstruction techniques are used to reconstruct the shale structure. The reconstruction uncertainty is quantified by comparing overall values of storage and transport metrics, as well as the misclassification of pore voxels compared to the phantom. We then select the most robust reconstruction technique and we vary the acquisition conditions to quantify the effect of artifacts. ...
Estimating porous media properties is a vital component of geosciences and the physics of porous ... more Estimating porous media properties is a vital component of geosciences and the physics of porous media. Until now, imaging techniques have focused on methodologies to match image-derived flows or geomechanical parameters with experimentally identified values. Less emphasis has been placed on the compromise between image processing techniques and the consequences on topological and morphological characteristics and on computed properties such as permeability. The effects of some of the most popular image processing techniques (filtering and segmentation) available in open source on 3D X-ray Microscopy (micro-XRM) images are qualitatively and quantitatively discussed. We observe the impacts of various filters such as erosion-dilation and compare the efficiency of Otsu’s method of thresholding and the machine-learning-based software Ilastik for segmentation.
Inside asphaltene aggregates in crude oils, the adsorbed hydrocarbons exist in the packed periphe... more Inside asphaltene aggregates in crude oils, the adsorbed hydrocarbons exist in the packed periphery while the occluded hydrocarbons exist inside the core of the asphaltene structures. Occluded hydrocarbons may be well protected from secondary alteration events in the reservoir due ...
In the crude oil, the other fractions such as hydrocarbons could be adsorbed and/or occluded insi... more In the crude oil, the other fractions such as hydrocarbons could be adsorbed and/or occluded inside asphaltene structures. In this work, the deuterated compound n-C 20 D 42 has been used to simulate the adsorption/occlusion characteristics of asphaltene in toluene solution. Based on the highly polydispersed structures of asphaltenes, the experimental results indicate that the adsorbed hydrocarbons could be exchanged with the outside bulk phase, whereas the occluded ones inside the core of asphaltenes could not be exchanged. These results suggest that substantial microporous units exist inside asphaltene structures, and these structural units are suitable to adsorb and occlude the other fractions in the crude oil. The carbon number of the occluded hydrocarbons could be up to C 40 , and the weight could be more than 0.5%, based on the initial asphaltene weight. The adsorption should occur at the periphery of asphaltene aggregates (the loosely packed ones), and then they are liable to be exchanged with the outside bulk phase. If the asphaltene molecule is large enough, the occlusion could occur at the asphaltene molecular level. However, this type of occlusion perhaps just occurs inside asphaltene aggregates (the close aggregating ones); if this is the case, this type of asphaltene aggregate should be considered to be the stable unit in toluene solution, and then the occluded hydrocarbons could not be exchanged with the bulk phase. Regarding the adsorption/occlusion properties of asphaltenes, the aforementioned results should be valid, even extrapolated into the crude oil reservoir system.
Being the heaviest fraction of crude oils, asphaltenes are liable to aggregate, and other molecul... more Being the heaviest fraction of crude oils, asphaltenes are liable to aggregate, and other molecules in the oils can be steadily adsorbed onto, and even occluded inside the macromolecular structures of the asphaltenes. These occluded compounds inside the asphaltenes can survive over geological time in oil reservoirs owing to effective protection by the macromolecular structures of the asphaltenes. The asphaltenes of a crude oil (ZG31) from the central Tarim Basin, NW China, were hierarchically degraded by increasing the amount of H 2 O 2 /CH 3 COOH to release the occluded compounds. Besides the common components, series of even numbered n-alk-1-enes and 3-ethylalkanes were detected among the occluded compounds. Comparison of the biomarker distributions and the compound-specific C isotopic results between the compounds from the maltenes and those from the occluded fraction, the ZG31 reservoir was suggested to have been charged multiple times, with different charges being derived from different strata of source rocks.
Some hydrocarbons occluded inside asphaltene structures can be considered to be “original oil”, a... more Some hydrocarbons occluded inside asphaltene structures can be considered to be “original oil”, and are very important especially for severely post-altered crude oil in related geochemical studies such as oil/oil, oil/source correlation. The use of oxidising reagents could properly release these occluded hydrocarbons, and make possible direct study of these compounds without interference from the segments chemically bonded to the
The spinning bubble tensiometer technique provides a handy tool to measure the potential at the a... more The spinning bubble tensiometer technique provides a handy tool to measure the potential at the air-water surface. The method is used to estimate the variation of the potential at the surface of aqueous solutions containing binary mixtures of surfactants (anionic, nonionic, and fluorocarbon anionic). The evidence on molecular interactions at the air-water surface is compared with the information deduced from the critical micelle concentration experimental data.
The zeta potentials of a single N2 bubble in near neutral aqueous solutions of 10–5 to 10–2 M NaF... more The zeta potentials of a single N2 bubble in near neutral aqueous solutions of 10–5 to 10–2 M NaF have been measured with a rotating cell zetameter. The zeta potentials in the NaF solutions are slightly more negative than those of comparable NaI concentrations. A simple interpretation of this observation is that the small size of the fluoride ion leads to its stronger adsorption at the interface, despite its smaller dielectric decrement. This would not be consistent with independent electrospray results from 100 µM solutions that bromide ion is less strongly adsorbed than iodide ion, i.e. that surface affinity increases with ion size. An alternative interpretation of the fluoride experiment is that the fluoride surface affinity is the consequence of stronger ion pairing with the NaOH that spontaneously forms at the interface.
Expanding the electrical double layer of minerals through low-salinity brine injection has been s... more Expanding the electrical double layer of minerals through low-salinity brine injection has been suggested as a possible enhanced oil recovery mechanism. To investigate this theory, we measured the ζ potential of different minerals, namely, sands from Fontainebleau, Ottawa, and Landes, a sample from a sandstone outcrop, and one crude oil. ζ-potential measurements can be used to quantify the surface charges of materials; therefore, experiments associated with this technique were performed to predict the behavior of repulsion or attraction between materials in different salinity and pH conditions. We showed that there is no significant difference between the ζ potentials of the tested materials. We did, however, observe that the different sands and sandstone have dissimilar adhesion behaviors. No correlation was found between the electrokinetic measurements performed on the minerals and their response to crude oil introduced into the system. The adhesion results obtained for the Landes and Ottawa sands were ...
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