We measured the water pore diffusion coefficient of a sample from the Toarcian formation at the Tournemire Underground Research Laboratory at 4 temperatures (10, 30, 50 and 70 °C), corresponding to the range of temperatures expected during the thermal phase of a high level nuclear waste storage.Using a fast NMR based technique, diffusion coefficients could be obtained in about 20 h for each temperature with high accuracy. Effective diffusion coefficients at 20 °C (2.7 × 10−11 m2/s) agree with existing data on similar claystones and tracer measurements on similar samples. Using an Arrhenius model an activation energy of 22.9 kJ/mol is found in the temperature range 30–70 °C, a value larger than those found by other authors in other claystones (17 to 21 kJ/mol). From NMR T2 relaxation time data, the activation energy of surface diffusion is evaluated at 9.6 kJ/mol. When considering all data points in the range 10–70 °C, we propose a power law model already used for bulk water to represent the observed non-Arrhenius behavior. The model allows estimating a tortuosity value of 4.1 for the sample considered around 100 °C. We attribute the low diffusion coefficient observed at low temperatures to a balance between surface and volume diffusion, where surface diffusion becomes more dominant at lower temperatures.

The pore size distribution is often an important parameter for transport processes in porous media. Cryoporometry experiments can provide such data in the meso and macropore size up to 1 μm providing the sample temperature is finely controlled. We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05 °C and impose temperature ramps down to 0.002 °C/min, necessary to characterize the largest pore sizes. The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here. For porous materials made of paramagnetic minerals such as lithium-iron phosphate (LiFePO4, LFP) or nickel-manganese-cobalt oxides (NMC) and saturated with octamethylcyclotetrasiloxane (OMCTS), the T2 relaxation times are very short such as protons from the liquid and frozen phases cannot be separated. Hence the usual cryoporometry experiment cannot be performed. Instead, we propose to use the T1 contrast to separate these phases. The method is studied in detail along with some temperature effects linked with the T1 variation of the bulk frozen OMCTS. We show an example on two cathode materials part of industrial battery product.

The pore size distribution is often an important parameter for transport processes in porous media. Cryoporometry experiments can provide such data in the meso and macropore size up to 1 μm providing the sample temperature is finely controlled. We use a Peltier based system inserted directly into the NMR probe to control the temperature within 0.05 °C and impose temperature ramps down to 0.002 °C/min, necessary to characterize the largest pore sizes. The pore size information in the macropore range cannot be obtained from gas adsorption techniques while mercury injection is questionable for the material considered here. For porous materials made of paramagnetic minerals such as lithium-iron phosphate (LiFePO4, LFP) or nickel-manganese-cobalt oxides (NMC) and saturated with octamethylcyclotetrasiloxane (OMCTS), the T 2 relaxation times are very short such as protons from the liquid and frozen phases cannot be separated. Hence the usual cryoporometry experiment cannot be performed. Instead, we propose to use the T 1 contrast to separate these phases. The method is studied in detail along with some temperature effects linked with the T 1 variation of the bulk frozen OMCTS. We show an example on two cathode materials part of industrial battery product.

Mitigation of global warming & climate change requires a limitation of anthropogenic CO2 content in the atmosphere. One solution to control CO2 increase is geo-sequestration (CGS) into depleted reservoirs. However, the storage resources of a reservoir are heavily linked to the associated wells injectivity, mainly in the near wellbore region. The formation of CO2 hydrates due to CO2 injection, and the associated thermodynamic phenomena, may greatly alter the petrophysical properties of these injection zones. The adiabatic depletion leads to a large temperature decrease which, associated with local "cold" conditions, can bring the system into the CO2 hydrates stability zone in the near wellbore area. If those conditions are encountered, a severe reduction, or even loss, of injectivity can be anticipated. CO2 hydrate can plug partially, or totally, the pore bodies and/or pore throats. Today, only few results are available regarding CO2 hydrates formation in these peculiar depleted near wellbore conditions. Loss of injectivity due to the hydrate formation risk is addressed in this experimental integrated study; hydrates formation in porous media in static conditions is performed using low field NMR, where hydrate formation in porous media in dynamic conditions is performed by the CAL-XTM experimental set-up. The first porous rock chosen was a high permeability sandstone. In static conditions, after setting the system to a targeted water saturation (ranging between 10 and 50 %), experiments were conducted in an in-house highpressure NMR set-up. Taking advantage of the huge relaxation contrast between protons, part of water molecules and hydrates, the average water content can be measured continuously during hydrate formation and dissociation as well as water profiles along the sample. The capability of the Peltier cooled NMR system to accurately control the temperature, allows a good determination of the thermodynamic stability limits. The influence of the water saturation is presented and discussed. The effect of hydrate formation on the permeability of porous rock is also studied. For this purpose, a series of high-throughput X-Ray monitored coreflood experiments are conducted using state-of-the-art equipment (CALXTM). Experiments are performed under a constant flow rate of CO2 at different initial water saturations. During CO2 injection, water saturation, as well as hydrate formation/dissociation, are monitored by time-resolved X-Ray radiography. The measurement of the pressure drop across the core sample during hydrate formation is used to evaluate the extent of the permeability change. It is observed that the higher the initial saturation, the greater the alteration of the permeability. This study also investigates partially the "memory effect"; cycles of hydrate formation, followed by dissociation were performed both on CAL-XTM and NMR set-ups. The produced "memory effect" translates into an accelerated hydrate's nucleation, i.e. a faster onset of hydrates re-formation, and a higher water to hydrate conversion. The produced experimental data intend to validate and parametrize the hydrates models in reservoir modelling software.

Our objective is to characterize the potential hydrate formation during CO2 injection in a depleted gas reservoir for which both the pressure and temperature can be low and within the hydrate stability zone; such hydrate formation may impact the gas injectivity. For this purpose, we developed a new NMR setup in which the temperature is particularly well controlled using a Peltier-based system inserted into the NMR probe. This setup allows us to impose slow temperature ramps (down to 0.1 degrees C/h), useful for observing quasi-static hydrate dissociation at a given pressure and thus measuring thermodynamic hydrate equilibrium points (T eq and P eq). The NMR measurements enable the continuous determination of the liquid water fraction within the porous media studied as well as the liquid content vertical profile. The samples are small cylinders of diameter 5 mm and maximum length 20 mm. The hydrate formation is detected by a decrease in the liquid water fraction. In a quartz sand pack at a constant pressure of 31 bar, the hydrate formation was studied by varying the temperature between 7 and -10 degrees C. The residual liquid volume fraction after hydrate formation was 0.05%. We estimated that a temperature increase rate no larger than 1 degrees C/h is necessary to properly determine the hydrate equilibrium temperature (T eq). In the large pores of the Bentheimer sandstone also studied, the largest temperature T eq of the hydrate stability zone at 21 bar is not significantly different from the one measured in the bulk phase from the literature.

The greater Paris area has some 12 million inhabitants and 48 heating network production units that exploit the heat capacity of a 1.5 km deep aquifer, the Bathonian limestone. This is one of the most productive aquifers in the world for district heating, with an annual output of about 1.7 TWh of energy. The current challenge for Paris is to triple the number of heating networks using geothermal energy so as to reduce dependence on fossil fuels (40% in 2020 in France). As no detailed geothermal reservoir model is available, drilling involves geological risk. A recent well, drilled at Grigny (20 km south of Paris), turned out to be a failure in transmissibility because the bed of permeable limestones it tapped into was very thin (meter-scale). The main aim of this study is to create a digital database and a 3D geological model of this aquifer to minimize geological risks and optimize the location of future geothermal operations around Paris. By compiling data from 168 wells, a high-resolution 3D geological model of 360 km3 size is constructed (about 40 km x 50 km x 0.2 km), made up of 12.2 million cells and displaying sedimentary facies, sequence stratigraphy, porosity (phi) and permeability (k). About 20% of the oolitic and bioclastic facies are of good reservoir quality (phi > 13% and k > 350 mD), especially in two targeted, highquality reservoir sequences. These facies of interest probably correspond to giant dunes and a shoal/barrier prograding from east to west. In these facies, permeable zones are generally 4 m thick and form patches of 1600 m x 1100 m, on average, elongated perpendicular to the depositional slope. 2D and 3D maps of temperature, salinity, porosity, transmissivity, and permeability allow us to understand the areas of interest for geothermal exploration, as demonstrated around Grigny. This model helps us to apprehend better the heterogeneous character of the reservoir for geothermal prospection and to reduce the risk of future doublets during well implantation. Detailed local models may be extracted to anticipate better the implantation of new doublets in areas with already densely spaced existing wells.

It is widely acknowledged that CO2, a greenhouse gas, is largely responsible for climatic changes that can lead to warming or cooling in various places. This disturbs natural processes, creating instability and fragility of natural and social ecosystems. To combat climate change, without compromising technology advancements and maintaining production costs at acceptable levels, carbon capture and storage (CCS) technologies can be deployed to advance a non-disruptive energy transition. Capturing CO2 from industrial processes such as thermoelectric power stations, refineries, and cement factories and storing it in geological mediums is becoming a mature technology. Part of the Mesohellenic Basin, situated in Greek territory, is proposed as a potential area for CO2 storage in saline aquifers. This follows work previously done in the StrategyCCUS project, funded by the EU. The current investigation includes geomechanical and petrophysical methods to characterise sedimentary formations for their potential to hold CO2 underground. The work is progressing under the Pilot Strategy, funded by the EU.

Injectivity decline problems are often encountered during geothermal water reinjection into the subsurface despite massive surface filtration. The reinjected water carrying only nano-sized particles at relatively low concentrations causes severe permeability impairment due to pore clogging by the transported particles. To provide a better understanding to injectivity decline problems, this study investigates the impact of clay minerals transport and deposition on formation damage of sandstone reservoirs. To identify the clays potentially responsible for clogging, a mineral characterization of natural samples, collected from a Triassic reservoir located in the Paris Basin (France), was realized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). The obtained results show that in this type of sedimentary environments, illite particles are the most abundant clay species that are more likely to be detached from the rock structure and migrate within the geothermal fluid. Illite particles were then used in core-flooding experiments to mimic their reinjection in sandstones under different physico-chemical conditions. The obtained flow curves were further explained by aggregation experiments carried out using the dynamic light scattering (DLS) technique. The results show a clogging-favored tendency promoted mainly by the increase of ionic strength and particle concentration and the decrease of flow rate.

Background: It is widely acknowledged that carbon dioxide (CO 2), a greenhouse gas, is largely responsible for climatic changes that can lead to warming or cooling in various places. This disturbs natural processes, creating instability and fragility of natural and social ecosystems. To combat climate change, without compromising technology advancements and maintaining production costs at acceptable levels, carbon capture and storage (CCS) technologies can be deployed to advance a non-disruptive energy transition. Capturing CO 2 from industrial processes such as thermoelectric power stations, refineries, and cement factories and storing it in geological mediums is becoming a mature technology. Part of the Mesohellenic Basin, situated in Greek territory, is proposed as a potential area for CO 2 storage in saline aquifers. This follows work previously done in the StrategyCCUS project, funded by the EU. The work is progressing under the Pilot Strategy, funded by the EU. Methods: The current investigation includes geomechanical and petrophysical methods to characterise sedimentary formations for their potential to hold CO 2 underground. Results: Samples were found to have both low porosity and permeability while the corresponding uniaxial strength for the Tsotyli formation was 22 MPa, for Eptechori 35 MPa and Pentalofo 74 MPa. Conclusions: The samples investigated indicate the potential to act as cap-rocks due to low porosity and permeability, but fluid pressure within the rock should remain within specified limits; otherwise, the rock may easily fracture and result in CO 2 leakage or/and deform to allow the flow of CO 2. Further investigation is needed to identify reservoir rocks as well more sampling to allow for statistically significant results.

The blockage induced by solid particles transport and deposition is one of the main causes of injectivity decline in geothermal sandstone reservoirs during reinjection. This paper investigates clay-induced clogging mechanisms to provide a better understanding to formation damage problems encountered in geothermal fields. In-depth NMR measurements were carried out during core-flooding experiments where illite clay particles (120 nm) were injected in sand-packed columns. SEM imaging was performed to compare the porous space before and after damage and study the morphology and distribution of the deposited particles in the sand column. Pressure drop measurements and NMR T2 relaxation time distributions revealed that clogging occurs in two stages: surface deposition and pore bridging. This was further confirmed by SEM images showing that pore-blocking illite ribbons were formed in the porous space.

We propose NMR relaxation techniques to evaluate diffusional exchange between the different porosity compartments of heterogeneous catalyst extrudates in addition to NMR diffusion measurements. The two systems considered are close to industrial products and contain a wide distribution of pore sizes spanning from microporosity (2 types of zeolites CBV400 and CBV720), mesoporosity induced by the alumina binder, and macroporosity introduced during the shaping procedure. The question is to determine in which system the meso and macroporosity provide the best access to microporosity. Beside standard techniques, we measured the pore size distribution using NMR cryoporometry in the range 2 nm up to 1 mu m, and the amount of microporosity below 2 nm from relaxation data at-29 degrees C. These measurements provide reference values independently of the connectivity or the hierarchical organization of the pore network. Long range diffusion was measured using methane and cyclohexane to evaluate the effect of macropores. When saturated with squalane, the diffusive exchange between micro and mesoporosity was evaluated using two techniques: (i) the comparison of the apparent mesoporosity fraction in the T2 distribution to the true value measured by cryoporometry, (ii) the measurement of exchange times using T2-exchange-T2 experiments. These two approaches give coherent results. The diffusive coupling was also observed with 2-propanol saturated extrudates, for which the surface residence time tau S was evaluated from the interpretation of the 3 relaxation times T2, T1 and T1 rho; for the 2 samples tau S differ by 2 orders of magnitude due to the very different Si/Al ratio of the 2 zeolites used in the extrudates. All these methods lead to the conclusion that the presence of mesoporosity in zeolite crystals is beneficial to the diffusive transport with the surrounding porosity only when molecule/zeolite interactions are not predominant.

Background: It is widely acknowledged that carbon dioxide (CO2), a greenhouse gas, is largely responsible for climatic changes that can lead to warming or cooling in various places. This disturbs natural processes, creating instability and fragility of natural and social ecosystems. To combat climate change, without compromising technology advancements and maintaining production costs at acceptable levels, carbon capture and storage (CCS) technologies can be deployed to advance a non-disruptive energy transition. Capturing CO2 from industrial processes such as thermoelectric power stations, refineries, and cement factories and storing it in geological mediums is becoming a mature technology. Part of the Mesohellenic Basin, situated in Greek territory, is proposed as a potential area for CO2 storage in saline aquifers. This follows work previously done in the StrategyCCUS project, funded by the EU. The work is progressing under the Pilot Strategy, funded by the EU. Methods: The current investigation includes geomechanical and petrophysical methods to characterise sedimentary formations for their potential to hold CO2 underground. Results: Samples were found to have both low porosity and permeability while the corresponding uniaxial strength for the Tsotyli formation was 22 MPa, for Eptechori 35 MPa and Pentalofo 74 MPa. Conclusions: The samples investigated indicate the potential to act as rock caps due to low porosity and permeability, but fluid pressure within the rock should remain within specified limits; otherwise, the rock may easily fracture and result in CO2 leakage or/and deform to allow the flow of CO2. Further investigation is needed to identify reservoir rocks as well more sampling to allow for statistically significant results.

If they are to be economically and technically sustainable, geothermal projects require the production of hot fluid at high flow rates over a 30-year thermal lifetime. The combined use of multiple logging tools in making pet-rophysical assessments of reservoir quality helps to optimize drilling in areas of high geothermal potential. The present paper focuses on four geothermal wells intercepting Middle Jurassic (Dogger) carbonate rocks of the Paris Basin where for the first time Nuclear Magnetic Resonance (NMR) log data have been successfully used to investigate reservoir porosity-permeability heterogeneities. A total of ten facies have been identified from recovered cuttings and cores and grouped into four facies associations along a schematic carbonate ramp profile. From the wells studied, four reservoir units exhibiting porosities exceeding 15% and permeabilities of up to 1 Darcy (D) were traced in the Calcaires de Comblanchien, the Oolithe Blanche and the Calcaires marneux a` Phola-domyes formations. The well's sub-horizontal trajectory and well-logs correlations between two wells, made it possible a priori to identify porous and permeable layers extending over at least 500 m and up to 2000 m within the Bathonian reservoir, providing useful pointers for further 3D reservoir geomodeling. Permeabilities derived from well testing proved to be overestimated when compared with NMR-derived permeabilities, illustrating the upscaling problem that is invariably a challenge in carbonate systems. NMR can be combined with production logging tool (PLT), that provides data on the distribution and thickness of productive layers, to give indications for example about continuous permeability record along the geothermal wells or about the proportion of micro and macroporosities in rocks. Based on the geological classification derived from examination of cores and cuttings, four rock-types (including mean T2 pore-size distributions) have been identified and attributed to a given sedimentary facies and depositional environment by extending a clustering method to NMR log distributions from wells.

A wireline NMR (Nuclear Magnetic Resonance) logging tool has recently been deployed in the Dogger geothermal aquifer of the Paris Basin to provide a continuous permeability estimation throughout the reservoir. The complex pore structure of heterogeneous carbonate systems means that careful consideration must be given to standard permeability prediction. A laboratory study was performed on cores from a geothermal well at Bobigny, north of Paris. Petrographic and petrophysical analyses of thin sections, water permeability and lab-oratory NMR relaxation time T2 were conducted on 72 samples. A classification was established using four main facies and the impact of microporosity and micritization on flow properties was investigated. The range of permeability is wide [0.05-1000 mD] and the evaluation addresses different relationships between permeability and a combination of porosity and T2 distributions. Since the latter distributions can provide an estimation of the pore size distributions and in particular the fraction of microporosity within the total porosity, several possi-bilities arise for better constraining the permeability relationship. For one facies, permeability is nearly inde-pendent of porosity over a porosity range of [0.12-0.22], illustrating the well-known difficulty of predicting permeability in carbonate lithologies. The best permeability prediction is obtained when considering only macroporosity instead of total porosity in a classical power law.

Sub-surface clay samples are difficult to characterize using conventional methods so non-invasive Nuclear Magnetic Resonance (NMR) techniques were used to evaluate in a preserved state the pore structure, porosity, water mobility, and affinity of various clay systems. Within the CLAYWAT project launched by the NEA Clay Club, some of the most advanced NMR techniques were applied to samples from 11 clay-rich sedimentary formations (Boom Clay, Yper Clay (both Belgium); Callovo-Oxfordian shale, Upper Toarcian (both France); Opalinus Clay from two sites (Switzerland); Queenston Fm., Georgian Bay Fm., Blue Mountain Fm. (all Canada); Boda Clay (Hungary); and Wakkanai Fm. and Koetoi Fm. (Japan)). The degree of induration within this suite of samples varies substantially, resulting in a wide porosity range of 0.02–0.6. The key finding is the determination of pore-size distribution by NMR cryoporometry in the range of 2 nm–1 μm with the native fluid present in the pore space for most samples. The water volume in pore sizes of <2 nm could also be measured, thus providing a full description of the porosity system. A specific preparation by sample milling was applied to the preserved original cores minimizing disturbances to the samples in terms of water loss. The water content measured by NMR relaxation was comparable to values obtained by drying at 105°C. In general, the narrow T2 distributions indicate that water was diffusing throughout the pore network during the magnetization lifetime, implying that T2 distributions cannot be considered as proxies for the pore-size distributions. For the set of samples considered, the T1/T2 varied between 1.7 and 4.6, implying variable surface affinity. Finally, for most samples, a pore-shape factor of ~2.4, intermediate between a sheet (1) and a cylinder (4), was deduced.

With around 50 heating networks today operating, the aera around Paris is the European region which concentrates the most heating network production units in terms of deep geothermal energy. In France, the energy-climate strategy plans to produce 6.4TWh in 2023, compared to 1.5TWh produced in 2016. Despite an exceptional geothermal potential, the current average development rate of 70MWh/year will not allow this objective to be achieved, it would be necessary to reach a rate of 6 to 10 times higher. The optimization of the use of deep geothermal energy is a major challenge for France, and in Ile-de-France, which has a population of nearly 12 million inhabitants. This project aims to reconstruct and simulate heat flows in the Paris Basin using an innovative methodology (1) to characterize, predict and model the properties of reservoirs (facies, porosity, permeability) and (2) simulate future circulations and predict the performance at a given location (sedimentary basin) on its geothermal potential. This study focuses on a high density area of well infrastructures around Cachan, (8 doublets, 1 triplet in 56 km2). A new sub-horizontal doublet concept has been recently (2017) drilled at Cachan to enhance heat exchange in medium to low permeability formations. Nuclear Magnetic Resonance (NMR T2) logs have been recorded in the sub-horizontal well (GCAH2) providing information on pore size distribution and permeability. We integrated all logging data (gamma ray, density, resistivity, sonic, NRM T2) of the 19 wells in the area and 120 thin section observations from cuttings to derive a combined electrofacies-sedimentary facies description. A total of 10 facies is grouped into 5 facies associations coded in all the 19 wells according to depths and 10 3rd order stratigraphic sequences are recognized. The cell size of the 3D grid was set to 50 m x 50 m for the XY dimensions. The Z-size depends on the thickness of the sub-zones, averaging 5 m. The resulting 3D grid is composed of a total of nearly 8.105cells. After upscaled, facies and stratigraphic surfaces are used to create a reliable model using the “Truncated Gaussian With Trends” algorithm. The petrophysical distribution “Gaussian Random Function Simulation” is used to populate the entire grid with properties, included 2000 NMR data, considering each facies independently. The best reservoir is mainly located in the shoal deposits oolitic grainstones with average porosity of 12.5% and permeability of 100 mD. Finally, hydrodynamic and thermal simulations have been performed using Pumaflow to give information on the potential risk of interference between the doublets in the area and advices are given in the well trajectory to optimize the connectivity and the lifetime of the system. NMR data, especially permeability, allow to greater improve the simulations, defining time probabilities of thermal breakthrough in an area of high density wells.

In a previous project, a silicate based sealant was developed and applied to the case of a clayey sandstone formation with the objectives of plugging the surroundings of a well typically within a radius of 1 m. Here, we report experiments conducted at the Mont Terri Underground Research Laboratory (MT-URL) focusing on the mitigation of pressure leakages associated with CO2 containment in near wellbore injection well systems. This work was performed under the auspices of the CO2 Capture Project (CCP), a three-company collaboration comprising Chevron, BP and Petrobras. The CCP effort is directed to develop more cost effective and efficient processes for CO2 concentration, capture and sequestration applied to the energy, refining, chemical and power generation industries in order to reduce greenhouse gas emissions. The experimental set-up installed at the underground test site mimics an injection well with the objectives of testing various sealants able to contain losses associated with delaminations that may occur at various well boundaries such as cement to casing and cement to caprock. Cement and caprock may also be micro-fractured. The tested sealant takes advantage of the properties of alkaline silicate solutions forming a gel after addition of an acid in appropriate strength and quantity. With a viscosity close to water, it can easily be injected in a liquid state and does not need to be activated after injection. The gelation time can be adjusted and is mostly sensitive to temperature. We tested two formulations of the sealant in a 1 m interval of the well system. The sealing capacity is evaluated by comparing flowrates at constant imposed pressure before and after injection of the sealant. Typically, a decrease by a factor of 10 of these flowrates is an indication of a good sealing performance. The first formulation proved to be efficient only for a limited time smaller than 1 month. The second improved formulation proved to be efficient for a period larger than one month.

The main motivation of this work is to determine quantitatively the pore occupancy of water and oil in some source rocks. The pore occupancy might be imposed by differences in chemical composition, wettability behavior and sorption of fluids in organic and inorganic porosities and will dramatically affect the hydrocarbons flow through the porous medium. We address this issue using NMR cryoporometry in two phase situations complemented by other NMR measurements. Using oil-wet samples originating from the Vaca Muerta formation, oil saturation as large as 70% were obtained by simply immersing fully water saturated samples into decane. At 100% water saturation, the measured pore size distributions indicate two main peaks around 2 and 80 nm. After immersion into oil, the pores occupied by water in the presence of decane are mostly around 2 nm and less. The pore sizes occupied by decane in the presence of water can then be deduced by subtracting the distributions obtained at 100% water saturation and after spontaneous drainage. Oil is mainly located in pores around 80 nm. These measurements are confirmed by high resolution SEM images showing the presence of porosity in the organic matter (sponge-like structure). Most of the oil can be associated with the porous organic matter network. These observations are complemented by the determination of the porosity below 2 nm and the water connectivity. From D2O diffusion experiments at 100% water saturation, we observed that about 19% of the total porosity is non-exchangeable with D2O. From the measurements of the liquid signal at -29 degrees C, we observed that on average 58% of the total porosity is located in pores smaller than 2 nm.

The mechanism behind the $^1$H NMR frequency dependence of $T_1$ and the viscosity dependence of $T_2$ for polydisperse polymers and bitumen remains elusive. We elucidate the matter through NMR relaxation measurements of polydisperse polymers over an extended range of frequencies ($f_0 = 0.01 \leftrightarrow$ 400 MHz) and viscosities ($\eta = 385 \leftrightarrow 102,000$ cP) using $T_{1}$ and $T_2$ in static fields, $T_{1}$ field-cycling relaxometry, and $T_{1\rho}$ in the rotating frame. We account for the anomalous behavior of the log-mean relaxation times $T_{1LM} \propto f_0$ and $T_{2LM} \propto (\eta/T)^{-1/2}$ with a phenomenological model of $^1$H-$^1$H dipole-dipole relaxation which includes a distribution in molecular correlation times and internal motions of the non-rigid polymer branches. We show that the model also accounts for the anomalous $T_{1LM}$ and $T_{2LM}$ in previously reported bitumen measurements. We find that molecular dynamics (MD) simulations of the $T_{1} \propto f_0$ dispersion and $T_2$ of similar polymers simulated over a range of viscosities ($\eta = 1 \leftrightarrow 1,000$ cP) are in good agreement with measurements and the model. The $T_{1} \propto f_0$ dispersion at high viscosities agrees with previously reported MD simulations of heptane confined in a polymer matrix, which suggests a common NMR relaxation mechanism between viscous polydisperse fluids and fluids under confinement, without the need to invoke paramagnetism.

Applied to Enhanced Oil Recovery, microemulsions are valuable systems for extracting the crude oil trapped by capillary forces in the porous reservoir rocks. The performances of the injected formulations are often assessed by quantifying oil composition in model systems that contain relatively high amount of surfactant/co-surfactant. Recently, the question of representativity of such systems was raised because kinetics aspects and complexity of crude were neglected in model systems and are likely to impact the process efficiency. The current quantification techniques limit the characterization of representative model systems as they are destructive, time consuming and not often applicable to dark or opaque systems. In the original aim to provide a quantitative kinetic study of such microemulsions, we propose a high resolution T1-weighted imaging technique to have access to 1D-composition profiles of co-surfactant, oil and brine in Winsor I, Winsor III and Winsor II microemulsions. The analysis is carried out on model systems at equilibrium for proof of concept. Results are correlated with X-Ray Micro-CT experiments to provide better interpretations and assess the method accuracy. We provide conditions of validity of the developed NMR method and discuss its potential limitations. To a larger extent, the method could be of interest to other applications that use similar systems.