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Electrical double layer expansion impact on the oilquartz adhesion for high and low salinity brines Marfa Nazarova, Patrick Bouriat, and Patrice Creux Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b03954 • Publication Date (Web): 30 May 2018 Downloaded from http://pubs.acs.org on May 31, 2018

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Electrical double layer expansion impact on the oilquartz adhesion for high and low salinity brines ‡

‡

‡

Marfa Nazarova † , Patrick Bouriat † , Patrice Creux † *

†

: CNRS/TOTAL/UNIV PAU & PAYS ADOUR, LABORATOIRE DES FLUIDES

COMPLEXES ET LEURS RESERVOIRS-IPRA, UMR5150, 64000, PAU, FRANCE.

: TOTAL Exploration and Production, CSTJF, Avenue de Larribau, 64000 Pau, France

low salinity brine, wettability, disjoining pressure, wettability, wetting, electrokinetics, oil – water – mineral interactions, Iso Electric Points, Zeta potential, porous media, surface charge, Electrical Double Layer, quartz, salts, electrolytes, roughness, hydration forces, DLVO.

ACS Paragon Plus Environment

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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 zeta potential of different minerals, namely sands from Fontainebleau, Ottawa and the Landes, a sample from a sandstone outcrop, and one crude oil. Zeta-potential measurements can be used to quantify the surface charges of materials, so experiments associated to 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 zeta 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 perfectly in line with what expected from zeta potential measurements, but the Fontainebleau sand and sandstone exhibited different behaviors. For the tested minerals we showed zeta potential changes may not be the only responsible of a low salinity brine effect concerning a system oil/brine/rock systematically characterized in coreflood with an observed additional recovery.


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INTRODUCTION A number of industrial processes are concerned by fluid flows in porous media as well as in natural rocks – oil & gas, hydrology, geothermal, carbon dioxide or methane underground storage for example – and in synthetic ones – catalysis, separators, microfluidics, etc. The behavior of liquid in porous media is conditioned by the physical chemistry of the fluid and by the interactions with the solid substrate. Among the numerous intermolecular forces that influence fluid distribution in natural pore structures, electric double layer forces are the central focus of many public and industrial research teams all over the world. Its interest stems from a possible link between electrical double layer forces and the “smart water”

1

effect observed in

labs or fields to increase oil production. Designing water composition is an Enhanced Oil Recovery (EOR) technique. Smart Water is a specifically designed water formulation, whose ionic composition and salinity are adapted to the targeted reservoir in order to change the oil/rock interaction and enhance oil recovery. This technique was brought to light by Tang and Morrow1, who observed incremental oil recovery from a sandstone after injection of low-salinity water. In the wake of this remarkable observation, a number of scientists attempted to understand this result through a series of experiments. After injecting low-salinity brine (LSB) in secondary or tertiary recovery modes, some authors reported incremental oil recovery in lab

2–5

or field

conditions 6. The most disconcerting observation made by many authors concerning this recovery technique is that its exact physical origin is still under debate. Several authors considered that these effects were caused by expansion of the electrical double layer when


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dilution occurs. Many other hypotheses including fine particle mobilization

1-7

, electrochemical

reactivity 8,,9 or wettability alteration 10,11 have also been put forward. Recently, Nasralla et al.

12

proposed double layer expansion (in low-salinity brine conditions)

as one of the mechanisms explaining additional oil recovery through LSB injection. The authors conducted experiments measuring zeta potential at rock-brine and oil-brine interfaces. They noted that the oil/brine interfaces were highly negatively charged with low-salinity brine, an observation that is not in contradiction with the commonly accepted phenomenon of surface screening by electrolytes at high salinity 13. Interaction of silica particles immersed in brines has already been investigated by Hartley et al. 14

using atomic force microscopy (AFM) to measure forces as a function of separation distance.

Their results showed very good agreement between experimental measurements taken using electrokinetic methods and the direct measurement obtained by AFM at low ionic strength. A high ionic strength of more than 0.1 M introduces complex steric mechanisms that give rise to a progressive divergence between the AFM and electrokinetic measurements. Moreover, Valtiner et al.

15,16

built a semi-empirical model of the force measurement profiles for rough and smooth

surfaces on solid substrates based on the extended DLVO theory (Derjaguin-Landau-VerweyOverbeek). The Valtiner’s model is consistent with AFM experiments, and shows how steric and hydration forces play a part in the repulsion interactions between rough and smooth surfaces. The pore-level scenario proposed by Radke et al.

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describes the crucial role of thin wetting

film layers between the non-wetting phases, usually oil and minerals in the case of oil-wet or mixed-wet reservoirs. These thin films are formed by molecular interaction forces, thereby it requires adding a new parameter, disjoining pressure, to the classical Young-Laplace equation. The disjoining pressure term, which is generally calculated from DLVO theory permits to


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express a complete net force balance of the intersurface forces acting on both sides of the wetting film. The stability of the film should depend essentially on three main forces: van der Waals interactions, electrostatic forces between double layers and hydration forces. The current work investigated the effect of a low-salinity brine on the electrical double layer in an oil-brine-mineral system previously referenced as sensitive to the effect of Low-Salinity Brine injection

18,19

. The hypothesis of electrical double layer expansion was previously tested as a

function of pH and salinity for the rock-brine-crude oil system used and reported by Cissokho et al. 18,19 and for systems obtained by flotation-like experiments by Bondino et al. 20.

EXPERIMENTAL SECTION

In the current work, global interactions between oil, mineral and brine were studied using inhouse zeta-potential measurement techniques developed by Bouriat21 and Creux22,23. The experiments used zeta-potential measurements to investigate interactions between oil-brine and rock-brine pairs. To ensure ionic exchange in the solution, all the elements of each system (oilbrine and rock-brine) were brought into contact to equilibrate the system before the measurements were performed.

Fluid phases A synthetic high-salinity brine with TDS = 50 g/L (Total Dissolved Salts) was prepared with 90 wt% of NaCl and 10 wt% of CaCl2. A brine with diluted salinity is obtained by diluting to 0.1% volume of initial high-salinity brine, therefore 0.05 g/l of TDS. The NaCl and CaCl2 used


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are manufactured by Sigma Aldrich® and have a purity grade of more than 99.9%. Water was purified by the conventional Elga Purelab® system to produce a resistivity of 18.2 MΩ.cm. The crude oil was provided by TOTAL and used as received. It is characterized by a cinematic viscosity of 5.82 cP at 40°C and a density of 830.7 kg/m3. The natural surfactants in the oil are characterized by the Total Acid Number (TAN) and the Total Base Number (TBN), which were 0.17 and 0.95 mg KOH/g respectively. The group compositions (saturated hydrocarbons, aromatic hydrocarbons, resins, and asphaltenes (SARA) analysis) of the crude oil sample were determined using an Iatroscan thin-layer chromatography-flame ionization detection system (TLC-FID). When the standard extraction process had been performed, the crude oil exhibited fractions of 58.2 wt% of saturated compounds, 31.4 wt% of aromatic compounds and 10.4 wt% of polar compounds and 2.3 wt% of asphaltenes.

Minerals The minerals used for this study are sands and sandstones. The Fontainebleau sand was provided by VWR, the Ottawa sand by Fischer Scientific, and the Landes sand and Dausse sandstone (referenced as DU3) by TOTAL. The results of the chemical analyses of the samples are shown in Table 1. The sandstone was used as received.

Methods For the single-drop measurements, we developed an in-house spinning cell for measuring electrophoresis. It was made with a special uncharged coating to prevent electro-osmotic flow when voltage is applied. As in the case of a spinning drop tensiometer, the centrifugal gravity effect keeps the drop suspended on the rotation axis and the mobility of the dispersed particle is


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measured by applying voltage. Zeta potential is measured via the mobility of the drop. The complete set-up is described by Graciaa et al. 24. Note, the presented curve, in this work has been drawn from 10 oil droplets in solution with 20 measurements per oil droplet to be able to represent a standard deviation. The range error is less than +/- 3 mV. For the zeta potential of the brine-mineral pair, a simple experimental set-up by direct weighing

21

was used to measure the electro-osmotic flow through a porous media. Unlike

current measurements, this technique uses potential measurements to determine electrokinetic mobility even when surface conduction is significant. This set-up is validated for flow equations in porous media of packs of fiber grains of random shape and size. The electrokinetic mobility measured is consistent with results those deduced from electrophoresis measurements and reference materials 13,21. Each reference of rock sample is measured twice with different samples to measure a representative zeta potential curve. The standard deviation has been represented for the range of zeta potential measurements and was determined from at least 20 measurements per points. The range error for the whole measurements is less of +/- 3 mV. The methods and set-ups developed in our laboratory to measure the zeta potential of both the oil-brine and brine-rock pairs are very easy and swift. The technical advantage of the electroosmotic device over electrophoresis is that the material does not need to be crushed so finely. Sandstones may contain some mineral inclusions such pyrite which do not appear at the pore surface and are therefore not in contact with the fluids in the reservoir. Crushing the material may disrupt mineral distribution and bring these inclusions to the surface, producing erroneous measurement results. Pyrite, when in contact with brine, may release multivalent iron ions that have a considerable impact on the zeta potential 13. Observation by the micro-CT DU3 sandstone (Figure 1) clearly reveals presence of very highly attenuating material inclusions (brightest


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elements, in this case pyrite). But, in a so small amount that any macroscopic inclusions are in possible contact with the brine.

Samples preparation The samples were unconsolidated (sands) except for the DU3 sandstone, which is highly permeable (about 0.8 D) and porous (17% in its consolidated state and 39% when broken; porosity is measured using the weighing method), and very weakly cemented. It was manually crushed without any mechanical assistance; to avoid destroying the grains and thus having mineral inclusions appear at the surface when inserted into the electro-osmometer. The crude oil contains indigenous surfactants. The effect of these surfactants, ionic ones in particular, on zeta potential is considered as non-negligible. The procedure used takes into account the exchanges between the oily and mineral phases that are stimulated by brine pH and salinity. The minerals were equilibrated for 12 hours at a volume ratio of 1 for the mineral to 10 for the brine, with a specific pH and salinity for each measurement. The solution pH was adjusted to some initial pHi by the appropriate amount of HCl or NaOH with an error on the measurements lower than 0.1. Five volumes of crude oil were added and the solution was stirred with a magnetic stirrer and heated at 60°C for 24 hours to favor crude oil partitioning and surfactant migration. The stirrer permits to collide oil and grains and therefore favoring large droplets adhesion on a short time. The samples were cooled down to 20°C and maintained at this temperature during one day without any stirring. Aspect of the obtained mixtures depends on the solid substrate nature and pH. In general, most of the oil volume was trapped at the bottom of the bottle by the solid particles after decantation when the stirrer was stopped. The released oil volume was negligible


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during the first hour. Then large oil droplets were detached from mineral surface due to gravity forces, but depending on pH and solid substrate nature, some solids coagulated or not to the rising oil droplets. Adhesion tests are performed for several pH (figure 2). Results are presented in the Table 2. A letter N is attributed for non-adhesion between oil and rock particles, A for particles adhering to oil and A/N for coexistence of the two systems. The oily supernatant was removed from the system with a syringe and the resulting brine and sand solution was centrifuged at 4,000 rpm (rotation per minute) for 2 minutes to get rid of small oil droplets. The final pH of the brine is noted. The oil droplet from the centrifugation was measured using the spinning zeta-meter in the brine previously equilibrated with the rock and the oil. It was maintained at the center of the capillary by spinning the tube at 800 rpm during the measurement with the equilibrated brine and the measurements were performed at 20°C. Once the oily phase was completely removed from the sample, the minerals and brines were collected to proceed to brine – rock zeta potential measurements with the electro osmometer. Note the whole experimental measurements where performed at 20°C, only the equilibration phase was done at elevated temperature (60°C).

RESULTS

Minerals For DU3, influence on the zeta potential of the presence of oil during equilibration is shown in Figure 3. The zeta potential of the DU3 sample equilibrated in presence of crude oil has a greater magnitude than that relative to DU3 equilibrated without oil phase. The oil presence during equilibration step contributes to enhance the electronegativity of the surface. The


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electronegativity increase is caused by the partitioning of endogenous surfactants transferred in the aqueous phase. The isoelectric points (IEP) for the DU3 samples converge around 2, indicating that no specific adsorption of charged molecules originating from the oil phase occurs at this pH. At higher pH the sandstone that contacted oil molecules exhibits a higher zeta potential in magnitude. This indicates that these molecules which present an acidic character may be naphthenic acids. In order to account for those organic compounds on surface properties of minerals, experiments presented below are all conducted with brines and particles that have contacted the oil. The low-salinity effect studied in Enhanced Oil Recovery processes corresponds, for example, to the diluted synthetic brine of 1 mM while a concentration of e.g. 1M reproduces those of the brines commonly found in natural reservoirs and geological systems such as sea water and formation water. It is then interesting to measure the evolution of zeta potential, at constant pH, as a function of equilibrating brine NaCl concentration between those two limiting concentrations. This was done for all the four rock samples at an initial pH pHi=7 with NaCl molar concentrations ranging from 1 mM up to 1 M. Results are shown in Figure 4. The decrease of zeta potential with NaCl salinity is similar in term of amplitude than the one described by many authors13 on quartz. For salinity above 1 M, zeta potential vanished to zero whatever the rock sample and solution composition (containing both NaCl (95%) and CaCl2 (5%) or NaCl only). A such reduced zeta potential in the range of high concentrations (>0.1 M) have been reported many times and is a normal diffuse layer, which characteristic length, the Debye length becomes smaller as the salt concentration augments and becomes just 1 nm thick at 0.1 M and 0.3 nm at 1 M 13.


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The pHi-pHf curves of the three sands and DU3 show similar behaviors, with very low ionic exchanges throughout the equilibrium phase (Figure 5 left). Figure 5 (right) shows the zeta potentials of the minerals as a function of pH. The curves, grossly follow the standard ones obtained for pure quartz

25,26

; the weak differences are due to

the surface charge densities linked to the potential presence of impurities at the surface. The magnitude of the zeta potential in the experimental pH range lies up to -30 mV to -50 mV. These high zeta potentials are in line with bibliographic data on quartz grains 25,26. The Ottawa sand has the highest purity grade. Its zeta-potential curve has a very classical shape, with a sigmoidal pH dependence characterized by an isoelectric point at around pH=2 and a half adsorption point at around pH=5.5 (figure 6). The electrical double layer of the Ottawa sand is very similar to the Fontainebleau one. Landes sample exhibits an iso-electric point slightly above those found for the other sands and DU3.

Oil In the case of the crude oil, the experimental evidence of a negative zeta potential even in weakly acidic solutions tallies with the results of previous works undertaken on pristine oils in terms of magnitude (about -50mV for neutral pH) 27. An isoelectric point at a pH of 2-3 indicates that hydroxide or anionic indigenous surfactants rather than protons tend to accumulate at the crude oil-brine interface. The zeta potential for a pH value greater than 5, corresponding to the pH range used in the petrophysical experiments, is strongly negative and exceeds -50 mV (Figure 6). The isoelectric point measured is below pH 3, which is strongly acidic. The origin of spontaneous surface charging will not be discussed in this work, and indeed little is known about it. Crude oil is a much more complex system and has not been studied as much as


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pristine oils or gas bubbles. We will simply point out that apparent acidic chemical groups are dominant despite the presence of cationic surfactants or macromolecules in the crude oil therefore potential endogenous surfactants able to be stimulated by pH changes.

DISCUSSION It is often reported that divalent ions in brines play an important role in oil-rock-brine interactions for “smart-water” phenomenon

1,6

. We compared the zeta-potentials of the same

sample DU3 in two aqueous solutions at 1 mM: the first solution is a pure NaCl solution and the second one is a NaCl (95 wt%) and CaCl2 (5 wt%) solution (Figure 7). Figure 7 shows that the electronegativity of the surface is increased in presence of the divalent ions. This result is rather disconcerting since CaCl2 is known to damp zeta potentials of electronegative surfaces. Then electroosmotic measurements were verified by running additional electrophoretic tests using Malvern’s commercial zeta-meter for dispersed particles and by measuring the zeta potential of the supernatant (Figure 9). Complimentary interfacial tension experiences between brines and a gas bubble were performed with the two low salinity brines containing only NaCl or NaCl and CaCl2 mixture. With the NaCl brine the measured interfacial tension was 61 mN/m instead of 72 mN/m demonstrating the presence of surfactants issues from the oil. The second interfacial tension measured with 5% CaCl2 brine was 53 mN/m clearly showing a more important transfer of endogenous surfactants in the aqueous phase or a facilitation of the surfactant adsorption by charge screening of the adsorbed species. The enhancement of the partitioning of endogenous surfactants with calcium ion presence is quite similar than results obtained by Moradi & al. 28.


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Increase of the surface electronegativity, observed in presence of a small amount of CaCl2 may be attributed to (1) the ability of this salt to favor endogenous surfactant extraction, as was shown previously by the interfacial tension measurements and (2) the fact that zeta potential of DU3 is higher in magnitude (see Figure 3) in presence of endogenous surfactants. Moreover this surfactant adsorption is quite important since it overcomes the damping effect due to Ca2+ adsorption. The scheme 1 details ions, surfactants and water distributions and the resulting generated electrical potentials as a function of the distance from the interface. Indeed, zeta potential (ς) is the electrical potential at the slipping plane located at the outer Helmholtz plane (O.H.P.). The electrical potential ψβ of inner Helmholtz plane (I.H.P.) is larger in magnitude than the surface potential ψ0 due to the presence of anionic surfactants. Specific 2+

adsorption of Ca

in the inner Helmholtz plane may damp the net balance of the apparent

negative electrical charge. Compared to the DU3 sandstone, the sands clearly exhibit similar electrokinetic fingerprinting behaviors. However, adhesion tests, based on a flotation-like protocol

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give different results.

The experiments highlighted that the oil adhered to the Fontainebleau sand over a wide range of pH whereas no adhesion occurred at a pH of more than 3 in the case of the Landes and Ottawa sands. The zeta potentials are similar and the ionic exchanges are low for the three systems, so the electrical double layer expansion is similar for the three experiments and only one sand mineral adheres to the oil. Considering the used minerals, DU3 sandstone includes many other minerals but all the sands contain mainly quartz and the electrokinetic behavior of all these minerals is also the same. Other forces in play at the interface need to be taken into account. Using a surface force apparatus, Israelachvili et al.16 produced experimental evidence of the hydration forces that


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impact one of the two main non-DLVO forces. Hydration force is a very short-range repulsive force, which is complex to take into account and is therefore overlooked most of the time. They showed that in concentrated aqueous solutions with multivalent ions, particles remained noncoagulated, even at the isoelectric point, due to the hydration forces. N.B. Hunter 13 observed that silica particles do not coagulate even at high electrolyte concentrations, when the double layer is expected to collapse. Borghi & al. have exhibited a quite important shift of the Iso Electric Point with the roughness changes of the TiO2 measured via Atomic Force Microscopy29. Considering oil adhesion on minerals means achieving the primary minimum of net forces balanced at the oil-mineral interface30, yet the energy map in the vicinity of the interface may be drastically modified by crevices and roughness15. Mineral roughness is known to affect the Van der Waals forces and the electrical properties, as shown by Valtiner et al.

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. The distribution of

spatial forces is more diffuse in the case of a rough material and reduces the magnitude of the interfacial forces. The combined effects of the non-DLVO forces and surface roughness may be taken into account in future works in order to characterize the reversibility of rock’s oil-wet to water-wet properties when brine is diluted 15,29. The zeta potential measurements performed here show the coulombic forces and the electrical double layer structures may not be the only cause to explain adhesion tests performed between minerals, crude oil and brines and more subtle mechanisms seem to occur. In term of operational concepts, many low salinity brine core-flood experiments have reported some results and exhibited inconsistencies of proposed concepts of mechanisms. More sophisticated experiments such X-ray Micro CT imaging is commonly used to identify the mechanisms but their analysis is complicated by the multiplication of phenomena: capillary and disjoining pressures, wettability alterations, etc…

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. Since 1997 and the paper of Tang & Morrow

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no clear explanation


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succeeded to convince the international community concerning the cause(s) of low salinity brine effect.

CONCLUSIONS Electrical interactions representative of a rock-brine-oil system were quantified, and we showed that the zeta potentials of all the samples studied are very close. These results appeared to be de-correlated to the adhesion experiments considering the similarities in the electrical double layers of the tested minerals. In the case of the Landes and Ottawa sands, the zeta-potential curves obtained are in agreement with the results of the coagulation tests, with adhesion occurring at around the isoelectric point. But for the Fontainebleau sand and DU3 sandstone samples, coagulation over the entire pH and salinity ranges was observed. Presence of Ca2+ seems to contribute more than Na+ to the electronegativity of the material. This behavior, in apparent contradiction with conventional results takes its origin by the fact that electronegativity is enhanced by the presence of crude endogenous surfactants partitioning (mainly naphthenic acids) which are more extracted from crude oil when Ca2+ is present in brine. Considering these results, we are unable, based on electrokinetics methods, at present to explain the variability of the results presented in scientific papers concerning the Smart Water Injection Method. The work described here shows that the low-salinity brine effect cannot be explained only by double layer expansion, and that new solutions other than those ordinary used today are required to characterize wettability and wettability changes in reservoir formations. It seems reasonable to infer that the net force balance resulting from the interfacial forces should be expressed more precisely than we can find in the published papers and especially


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short-range forces. It also appears reasonable to take into account surface roughness, which is now known to impact magnitude of interfacial forces governing the mechanics of thin films and adhesion 15,16. The mechanisms around the overlapping of electrical double layer and more globally the physics of films is quite dependent of the distance of approach therefore in porous media of the capillary pressure. To track such mechanisms, real systems should be employed and not analog experiments leading to non-representative situations.


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Figure 1. Inclusion on image of the crushed sandstone obtained by X-ray micro-CT at 0.96 µm of resolution.


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Figure 2. Left: Aspect of sand sample during equilibration with brine under stirring. Center right: oil drop rising after a while. Top and down Right: Aspect of an oil drop when sand adhesion occurs.


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Figure 3. Zeta potential of the DU3 sandstone in contact with brine after equilibration in presence (green) or absence (blue) of oil.


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Figure 4. Zeta potential of the various studied sands as a function of NaCl concentration in brine after equilibration (with oil) at pHi = 7 (green triangle: Landes sand; blue diamond: Fontainebleau sand; red square: Ottawa sand; orange disc: DU3).


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Figure 5. Left Final pH versus initial pH for 1mM NaCl brine. Right Zeta potentials as a function of final pH of the various studied sands. In all experiments 1mM NaCl brines were used and stirred in presence of oil.


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Figure 6. Zeta potential of Ac oil droplet immersed in 1 mM of aqueous solutions in function of pH.


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pH 1

3

5

7

9

11

20

0 Zeta potential (mV)

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-20

-40

-60

-80

Figure 7. Zeta potential of DU3 immersed in aqueous solutions at 1 mM of NaCl brine (blue diamond), 0.95 mM NaCl and 0.05 mM CaCl2 measured with electro-osmometer (red square). The green diamond corresponds to the zeta potential of recovered supernatants measured by electrophoresis.


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Scheme. 1 (Left) Schematic sketch of Grahame-Stern model of electrical double layer representing ions, surfactants (red) and water dipole distributions and its incidence on the electrical potentials and ς potential (right).


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Energy & Fuels

Table 1. Size and Mineralogy of rock samples (wt %)

Mineral composition Rock sample

Mean diameter (μm) Quartz Clays Feldspar Pyrite

Landes Sand

480

99.11

0

0

0

Ottawa sand

880

99.90

0

0

0

Fontainebleau Sand

260

99.91

0

0

0

DU3

300

86.1

3.1

10.6

0.2


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Table 2. Adhesion of sands to oil droplets for several pH in low salinity (NaCl + CaCl2) (A: for adhesion, N for coagulated).

Rock sample

pH 2 pH 3 pH 4 pH 5 pH 6 pH 7 pH 8

DU3

A

A

A

A

A

A

A

Ottawa sand

A

N

N

N

N

N

N

Fontainebleau sand A

A

A

A

A

A

A

Landes sand

A/N

N

N

N

N

N

A

AUTHOR INFORMATION * PR Patrice Creux, LFCR, University of Pau, UMR 5150 UPPA-CNRS-TOTAL, Avenue de l’université, BP 1155, 64013 Pau cedex, France. Email : [email protected]


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Phone : +33 (0)559407681 Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally. (match statement to author names with a symbol) ACKNOWLEDGMENT The authors would like to thanks TOTAL R&D corporate and ANRT, which have supported this work and TOTAL E&P to have allowed publication. We also acknowledge Pr F. Marias from University of Pau for the access to the pyrolyser.


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Electrical double layer expansion impact on the oil ... - ACS Publications

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