Pore Network Characterization Research Articles

Development and Application of an Advanced Percolation Model for Pore Network Characterization by Physical Adsorption.

Physical adsorption is one of the most widely used techniques to characterize porous materials because it is reliable and able to assess micro- and mesopores within one approach. Challenges and open questions persist in characterizing disordered and hierarchically structured porous materials. This study introduces a pore network model aimed at enhancing the textural characterization of nanoporous materials. The model, based on percolation theory on a finite-sized Bethe lattice, includes all mechanisms known to contribute to adsorption hysteresis in mesoporous pore networks. The model accounts for delayed and initiated condensation during adsorption as well as equilibrium evaporation, pore blocking, and cavitation during desorption. Coupled with dedicated nonlocal-density functional theory kernels, the proposed method provides a unified framework for modeling the entire experimental adsorption-desorption isotherm, including desorption hysteresis scans. The applicability of the method is demonstrated on a selected set of nanoporous silica materials exhibiting distinct types of hysteresis loops (types H1, H2a, H1/H2a, and H5), including ordered mesoporous silica networks (KIT-6 and SBA-15/MCM-41 hybrid silica with plugged pores) and disordered mesoporous silica networks (hierarchical meso-macroporous monolith and porous Vycor glass). For all materials, a good correlation is found between calculated and experimental primary isotherms as well as desorption scans. The model allows us to determine key pore network characteristics such as pore connectivity and pore size distributions as well as a parameter correlated with the impact of pore network disorder on the adsorption behavior. The versatility and enriched textural insights provided by the proposed novel network model allow for a comprehensive characterization previously inaccessible and hence will contribute to further advancement in the textural characterization of novel nanoporous materials. It has the potential to provide important guidance for the design and selection of porous materials for optimizing various applications, including separation processes such as chromatography, heterogeneous catalysis and gas and energy storage.

An improved convolutional architecture for quantitative characterization of pore networks in fine-grained rocks using FIB-SEM

Focused ion beam scanning electron microscope (FIB-SEM) is one of the most advanced imaging techniques for analyzing and understanding complex pore networks in shale and other fine-grained formations. However, FIB-SEM imaging tends to be time-consuming and labor-intensive and can result in biased interpretations associated with pore analysis. Recently, U-Net or its variants for image segmentation have been applied to capture microscopic pores at higher resolutions. The ‘traditional’ encoder-decoder-based approaches tend to detect very fine-scale microscopic pores poorly. This study presents an improved convolutional architecture for automatically analyzing pore structures in shale reservoirs using FIB-SEM. It does so by applying an overcomplete convolutional architecture, KiU-Net, to capture very fine-scale microscopic pores by accurately defining their edges in the input FIB-SEM images. The KiU-Net learns low and high-level features by making the model more sensitive to fine-scale microscopic pores in the input images. The purpose of this study is to demonstrate KiU-Net's capabilities by analyzing different shale formations with varying characteristics. The results indicate that KiU-Net is more accurate and efficient than other methods in predicting nanopores in the Longmaxi, Niutitang, Qingshankou, Qianjiang, and Yanchang Formations (China), Bakken shale (Canada), and coal reservoirs (China). Furthermore, KiU-Net demonstrated the advantage of requiring fewer parameters and achieving super convergence compared to the Attention U-Net technique. KiU-Net addresses the challenges of the Edge-Threshold Automatic Processing (ETAP) methods by capturing very fine-scale microscopic pores with accurate edges. This study further enhances the accuracy and efficiency of pore analysis in shales, thereby offering an improved method for understanding shale reservoir quality with the potential to improve petroleum recovery from such formations.

Redoxtrons – An experimental system to study redox processes within the capillary fringe

AbstractSpatiotemporal characterisation of the soil redox status within the capillary fringe (CF) is a challenging task. Air‐filled porosities (ε), oxygen concentration (O2) and soil redox potential (EH) are interrelated soil variables within active biogeochemical domains such as the CF. We investigated the impact of water table (WT) rise and drainage in an undisturbed topsoil and subsoil sample taken from a Calcaric Gleysol for a period of 46 days. We merged 1D (EH and matric potential) and 2D (O2) systems to monitor at high spatiotemporal resolution redox dynamics within self‐constructed redoxtron housings and complemented the data set by a 3D pore network characterization using X‐ray microtomography (X‐ray μCT). Depletion of O2 was faster in the organic matter‐ and clay‐rich aggregated topsoil and the CF extended >10 cm above the artificial WT. The homogeneous and less‐aggregated subsoil extended only 4 cm above the WT as indicated by ε–O2–EH data during saturation. After drainage, 2D O2 imaging revealed a fast aeration towards the lower depths of the topsoil, which agrees with the connected ε derived by X‐ray μCT (εCT_conn) of 14.9% of the total porosity. However, small‐scaled anoxic domains with O2 saturation <5% were apparent even after lowering the WT (down to 0.25 cm2 in size) for 23 days. These domains remained a nucleus for reducing soil conditions (EH < −100 mV), which made it challenging to characterise the soil redox status in the CF. In contrast, the subsoil aeration reached O2 saturation after 8 days for the complete soil volume. Values of εCT_conn around zero in the subsoil highlighted that soil aeration was independent of this parameter suggesting that other variables such as microbial activity must be considered when predicting the soil redox status from ε alone. The use of redoxtrons in combination with localised redox‐measurements and image based pore space analysis resulted in a better 2D/3D characterisation of the pore system and related O2 transport properties. This allowed us to analyse the distribution and activity of microbiological niches highly associated with the spatiotemporal variable redox dynamics in soil environments.Highlights The time needed to turn from reducing to oxidising (period where all platinum electrodes feature EH > 300 mV) condition differ for two samples with contrasting soil structure. The subsoil with presumably low O2 consumption rates aerated considerably faster than the topsoil and exclusively by O2 diffusion through medium‐ and fine‐sized pores. To derive the soil redox status based upon the triplet ε–O2–EH is challenging at present in heterogeneous soil domains and larger soil volumes than 250 cm3. Undisturbed soil sampling along with 2D/3D redox measurement systems (e.g., redoxtrons) improve our understanding of redox dynamics within the capillary fringe.

New approach of mercury intrusion porosimetry to evaluate the microstructure of cement-bases matrixes: Application on slag cement mortars

In this work, the experimental technique “Mercury Intrusion Porosimetry MIP”, a characterization technique commonly used with success, is presented (sample preparation, experimental procedure, results). Usually the results of the said technique are mainly used for the microstructure characterization of cement-based matrixes. In order to better define the pore network characterization, a particular procedure has been tried: for each test, a double mercury intrusion is performed, allowing the measurement of the pore distribution of the total network and the reversible one. This allows a better distinction between the total network porosity and the closed porosity of the irreversible network. This technique was applied to standard cement-based mortars without and with 50% blast furnace slag. Thus, the microstructure evolution was followed after 28 and 360 days of maturation in wet cure by the proposed technique as well as by an exploration with SEM electron microscope. A careful analysis of the results showed the effectiveness of the tested approach in terms of understanding the matrix microstructure (pore size and accessibility). Moreover, the results have well demonstrated the expected positive effect of the slag on the densification of the mortar microstructure in the long term.

Three-dimensional pore network characterization of reconstructed extracellular matrix.

The extracellular matrix (ECM) has a fiber network that provides physical scaffolds to cells and plays important roles by regulating cellular functions. Some previous works characterized the mechanical and geometrical properties of the ECM fiber network using reconstituted collagen-I. However, the characterization of the porous structure of reconstituted collagen-I has been limited to the pore diameter measurement, and pore network extraction has not been applied to reconstituted collagen-I despite the importance of pore interconnectivity. Here, we aim to show the importance of characterizing the pore network of reconstituted collagen-I by comparing the pore networks of structures that have different fiber alignments. We show that the fiber alignment significantly changes the pore throat area but not the pore diameter. Also, we demonstrate that larger pore throats are directed in the direction of the fiber alignment, which may help in understanding the enhanced cell migration when fibers are aligned.

Towards Functionally Graded Sand Molds for Metal Casting: Engineering Thermo-mechanical Properties Using 3D Sand Printing

Growing applications of additive manufacturing (AM) have now been adopted for metal castings via indirect hybrid AM, i.e., 3D sand printing (3DSP). A comprehensive study on the thermo-physical properties of 3DSP molds based on 3DSP processing conditions and their effects on materials and mechanical properties of resulting aluminum castings is presented. The effect of furan binder content (i.e., 1–3%) on as-printed 3DSP molds is evaluated to determine changes in dimensional accuracy, density (helium pycnometry), actual binder content (loss on ignition) and mechanical strength (three-point bending and tensile testing) and thermal properties (transient plane source technique and casting runs). Pore network characterization via mercury intrusion porosimetry does not reveal any significant differences in the morphology of pore structures due to varying binder concentrations. However, bulk permeability is reduced with increasing binder content. Thermal analysis shows a reduction in conductivity and heat capacity due to binder degradation. Findings from this study will enable the optimum selection of binder content for functional grading of 3DSP molds/cores for adequate degassing and mechanical strength, which is ready for adoption by both foundries and 3DSP service providers.

Microstructural investigation of different nanopore types in marine-continental transitional shales: Examples from the Longtan formation in Southern Sichuan Basin, south China

Variations in pore types, the complexity of pore structures, and strong heterogeneity complicate the thorough characterization of pore networks in marine–continental shales. In this study, a novel 2D image processing method was proposed, expounded, and verified to clarify the geometrical morphologies, formation mechanisms, the size distributions, proportions and the fractal characteristics of different types of pores in marine–continental shales. Six types of pores (inter-particle, intra-particle, organic matter (OM), inter-crystalline, dissolved pores, and micro-fractures) were classified and morphologically characterized. The different types of shale pores had distinct relatively restricted morphologies, formation mechanisms, and size ranges. Nano- and micron-sized pores were controlled by OM pores and micro-fractures, with the size ranging of 6–80 nm and 200–350 nm and 6–10 μm, respectively. Furthermore, the fractal dimension characteristics were investigated on the basis of the 2D binary images, and the results were verified by the fractal findings obtained from the N2 adsorption data. These fracture dimension results demonstrated that the Longtan shale pore structures had strong complexity and heterogeneity, which was strongly and positively controlled by micro-fractures, inter-crystalline and OM pores. In addition, the total organic carbon content strongly and positively influences the development and anisotropy of the nanoscopic pores, which were dominated by OM pores; while the clay minerals content has a minor effect on the total pore development and heterogeneity of shales but a significant effect on the dissolved pore development of shales, whereas brittle minerals inhibit total pore development and heterogeneity of shales but contribute greatly to the development of the inter-crystalline pores.

Three-dimensional pore network characterization of loess and paleosol stratigraphy from South Jingyang Plateau, China

The deformation and failure of a loess slope are closely related to the loess collapsibility and permeability, which are primarily controlled by the pore geometrical structure. This is a microstructural investigation of loess and paleosol from Jingyang on the South Loess Plateau in China using X-ray micro-computed tomography to explore the three-dimensional pore structure by quantitative pore network parameters. The three soil types (L1, L2 and S2) exhibit complex pore structures and obvious anisotropy, as reflected by dense networks, wide pore size ranges and different pore throat radii and frequencies at different dip angles. From L1 to L2 to S2, the structure tends to become more compact, the pore size tends to decrease, and the connectivity tends to weaken; these differences chiefly depend on the particle composition. In soil with low clay content, the clay particles mainly act as connectors of silt and sand particles or adhere to their peripheries. With high clay content, the clay particles also combine with silt particles to form bulky aggregates, generating some large inter-aggregate pores and numerous fine intra-aggregate pores. Pore structure, which provides space for water movement, has a profound influence on the mechanical behavior of soil, and the relationship between permeability and pore structure is discussed. The results demonstrate the positive role that the pore (> 13 μm) proportion, pore connectivity and pore throat radius play in permeability. Both the pore throat radius and the permeability coefficient are greater in the vertical direction than in the horizontal direction, implying a large pore throat has a greater effect on water migration than that of multiple small pore throats.

Mineral Alteration and Fracture Influence on the Elastic Properties of Volcaniclastic Rocks

AbstractIn geothermal environments, the physical properties of rocks, such as porosity and alteration, are highly variable and control the reservoir's elastic and hydraulic properties. Elastic wave velocity in volcaniclastic rocks and their relation to fractures, pore shapes, and mineral alteration is mostly unknown. We measure ultrasonic P and S wave speeds on volcanic rocks from the Ngatamariki Geothermal Reservoir, New Zealand. Data clustering of wave speed versus porosity and density allow us to classify lithotypes of variable propylitic and phyllic mineral alteration. Wave speeds increase first due to porosity reduction as a result of mineral alteration and welding and, second, due to the high elasticity of alteration minerals (epidote, chlorite, and carbonates). We model the rock porosity as composed of equant pores and oblate‐spheroidal microfractures following an elastic effective medium model. For our samples, microfracture porosities range from 4% in the volcaniclastic tuffs to less than 1% in the ignimbrites, which we validate with pycnometer porosity data under effective pressure. We quantify that within one geological volcaniclastic formation, wave speeds vary up to 47% due to rock alteration and welding, while the effect of microfractures and changes in effective stress on wave speeds is secondary (up to 11%) but not negligible. From the experimental and numerical results we show that equant pores remain open at reservoir conditions (2,000 m) and can retain considerable porosity (10%). Our analysis has implications for microfracture and pore network characterization in geothermal reservoirs, in particular, in vapor‐dominated systems where matrix porosity and permeability play a role.

Effect of Internal Magnetic-Field Gradients on Nuclear-Magnetic-Resonance Measurements and Nuclear-Magnetic-Resonance-Based Pore-Network Characterization

Summary Nuclear-magnetic-resonance (NMR) measurements have been extensively used for determining porosity, pore-size distribution, and fluid saturation in porous media. However, internal gradients of the magnetic field generated by the presence of paramagnetic or diamagnetic centers such as shale or clay particles can significantly affect NMR response. Consequently, the resulting interpretation for pore-size distribution and porosity is also affected. In this paper, we quantify the effect of internal magnetic-field gradients and spatial distribution of matrix components such as clay minerals on NMR response using pore-scale NMR numerical simulations. We also quantify the influence of the aforementioned parameters on the NMR-based evaluation of porous media. We used the finite-volume method to numerically solve the Bloch (1946) equations and simulated magnetization decay in porous media. We cross validated the reliability of numerical simulations using analytical solutions given for spherical pores in different diffusion regimes. The model was then used for simulation of NMR response in the pore-scale images of sandstone and carbonate rocks. We used Larmor frequency of 2 MHz, external magnetic-field gradient of 0.10 T/m, and half-echo spacing time of 0.5 ms for simulating NMR response in pore-scale images of sandstones and carbonates. We then developed synthetic cases using actual rock images covering a wide range of spatial distribution of clay minerals (i.e., paramagnetic centers) to quantify the sensitivity of NMR decay to internal magnetic-field gradients. We quantified the sensitivity of NMR response for distribution of clays as thin laminae in the rock and as thin layers on the surface of the grains. The results showed that at low concentration (0.3 to 0.7%) of dispersed clay, there is a negligible effect of internal magnetic-field gradients on magnetization decay. At higher concentration of dispersed clay (5.1 to 7.3%), we observed a significant effect of internal magnetic-field gradients on magnetization decay. The presence of shale minerals can cause 53% variation in the location of the transverse-relaxation-time constant (T2) and up to 67% relative error in the assessment of dominant pore sizes. Shale laminations containing clay were found to produce an effect of up to 31.8% on T2 relaxation-time constant, which could cause a relative error of 50.0% in estimates of dominant pore size in the rock. The outcomes of this paper demonstrated the effect of heterogeneous rock mineralogy on NMR response. The effect of internal magnetic-field gradients generated by shale and clay on NMR becomes relevant when shale and clay particles are close to the pore fluid and their magnetic field starts to affect the distribution of magnetic field in the pore space. The results reveal the importance of characterizing the distribution of shale and clay minerals before interpreting NMR response and can potentially improve conventional techniques of pore-network characterization (pore-size distribution and pore volume) in the presence of clay minerals where internal magnetic-field gradients are not negligible.

Review of Steady-State Two-Phase Flow in Porous Media: Independent Variables, Universal Energy Efficiency Map, Critical Flow Conditions, Effective Characterization of Flow and Pore Network

In many applications of two-phase flow in porous media, a wetting phase is used to displace through a network of pore conduits as much as possible of a non-wetting phase, residing in situ. The energy efficiency of this physical process may be assessed by the ratio of the flow rate of the non-wetting phase over the total mechanical power externally provided and irreversibly dissipated within the process. Fractional flow analysis, extensive simulations implementing the DeProF mechanistic model, as well as a recent retrospective examination of laboratory studies have revealed universal systematic trends of the energy efficiency in terms of the actual independent variables of the process, namely the capillary number, Ca, and the flow rate ratio, r. These trends can be cast into an energy efficiency map over the (Ca, r) domain of independent variables. The map is universal for all types of non-wetting/wetting phase porous medium systems. It demarcates the efficiency of steady-state two-phase flow processes in terms of pertinent system parameters. The map can be used as a tool for designing more efficient processes, as well as for the normative characterization of two-phase flows, as to the predominance of capillary or viscous effects. This concept is based on the existence of a unique locus of critical flow conditions, for which the energy efficiency takes locally maximum values. The locus shape depends on the physicochemical characteristics of the non-wetting phase/wetting phase/porous medium system, and it shows a significant mutation as the externally imposed flow conditions change the type of flow, from capillary- to viscosity-dominated. The locus can be approached by an S-type functional form in terms of the capillary number and the system properties (viscosity ratio, wettability, pore network geometry, etc.), suggesting that formative criteria can be derived for flow characterization in any system. A new, extended definition of the capillary number is also proposed that effectively takes into account the critical properties of all the system constituents. When loci of critical flow conditions pertaining to processes with different viscosity ratio in the same pore network, are expressed in terms of this true-to-mechanism capillary number, they collapse into a unique locus. In this context, a new methodology for the effective characterization of pore networks is proposed.

Wettability characterization of pore networks of gas diffusion layers in proton exchange membrane fuel cells

Both the structure of the pores in a Gas diffusion layer (GDL), and the interactive characteristics between water and the carbon fibers which compose the GDL are very important in understanding transport phenomena in Proton exchange membrane fuel cell (PEMFC), especially water transport, distribution and management. Wettability of pore network as well as its structure is the major factor which determines the relation between water or air saturation and capillary pressure of the micro-scale pore network. In this study, the impregnation characteristics of TGPH-120 with 30 wt.% of PTFE as a function of time were investigated at different temperature to determine the effect of water condensation in the pore network. In succession, using the Method of standard porosimetry (MSP), various porometric characteristics are suggested. The proportion of saturated pore volume with water to the total pore volume is represented for the GDL impregnated at different temperatures. The contact angle of water on the hydrophilic pores whose size is in charge of a majority of the pore volume was estimated from 35° to 53°. The relation of capillary pressure with saturation was also measured for each condition. The air saturation increased slower with increasing capillary pressure when water was used as the working liquid than when octane was used because of the mixed wettability of the pore networks in the GDL.

Optimization of pore-network characterization of a compacted clay material by TEM and FIB/SEM imaging

In clay-rich sedimentary rocks, the pore network is considered to play a key role in controlling transport properties. The pore size distribution (PSD) of clay-rich rocks, the geometrical features of the pore network, and the clay content are parameters governing the diffusion process through clay formations. In the last few years, research has contributed to improving understanding of some clay-rich rock pore networks by using microscopic imaging techniques (FIB-nt, BIB, X-ray tomography, etc.). These techniques image the mesostructure scale organization of clay materials, but the studies have highlighted several limitations for full pore distribution characterization in terms of geometry and connectivity. Here we demonstrate that we can characterize a clay material's pore network supported by FIB-nt and TEM techniques reliably, to provide useful input data for assessing a future modeling task. The material studied was a compacted clay material mainly composed of illite, a non-swelling mineral. Illite was chosen in order to represent an analog system mimicking the clay matrix of natural clay-rocks. With this compacted clay plug we were able to work on homogeneous systems with controlled porosity, facilitating comparison between different methods. All the techniques used in this work, whether bulk or microscopic, show that all results converge to a similar and full PSD. This project's main improvement was to demonstrate how to improve the usual resolution limitations and data handling of FIB-nt techniques in order to recognize a fully connected pore network.

An Integrated Method for Upscaling Pore-Network Characterization and Permeability Estimation: Example from the Mississippian Barnett Shale

Although pore-network characterization of shale rock systems is being actively investigated, a detailed understanding of the pore network at the nanometer-to-millimeter scale has not been completed. This is because of the technical limitations of collecting and integrating data at the wide spectrum of scales necessary to understand the pore network. Permeability for a micrometer-scale volume can be estimated based on pore-scale modeling for the focused ion beam/scanning electron microscope (FIB/SEM) milled 3D pore network; however, it is not clear how representative this permeability is for larger volumes. In this study, an integrated method employing FIB/SEM, helium ion microscopy, and synchrotron X-ray micro-computed tomography (micro-CT) was developed and applied to a Barnett Shale sample for pore and organic-matter distribution network characterization and upscaling. Organic-matter particle network characterization using synchrotron micro-CT scanning is the key step that bridges the gap between nanometer-scale and macroscopic observations. A conceptual model and an empirical equation were developed for permeability estimation based on FIB/SEM and micro-CT image analysis and mercury intrusion data. Upscaled permeability estimation was produced based on the empirical equation and parameters from the image and mercury intrusion analysis. The resulting permeability values of 2–22 and 0.6–3 nD for parallel and perpendicular to bedding planes, respectively, are comparable to laboratory measurements of the same sample. The proposed technique provides a method for more basic understanding of the pore network and pore-permeability relationship for organic-rich shale samples, and can serve as a basis for further upscaling to core and formation scale.

Dehydration Effect on the Pore Size, Porosity, and Fractal Parameters of Shale Rocks: Ultrasmall-Angle X-ray Scattering Study

The characterization of pore networks is extremely important in understanding transport and storage phenomena in unconventional gas and oil reservoir rocks. An ultrasmall-angle X-ray scattering (USAXS) measurement has been performed on Silurian black shales from the Baltic Basin, Poland, from a wide range of depths along a burial diagenetic sequence. This study provides insight into the nature of the pore structure, including the pore size distribution, total porosity, and fractal dimensions of the rocks. Samples were measured in both their air-dried state, equilibrated at ∼50% relative humidity, and prior to dehydration by drying at 200 °C to make a comprehensive comparison of the pore structure changes induced by dehydration. Two trends were observed: porosity values decreased with depth as expected from the models of porosity evolution with burial and increased upon sample dehydration. The USAXS-measured porosity values show very good correspondence with the measurements by immersion porosity methods. ...

Micro- and nano-X-ray computed-tomography: A step forward in the characterization of the pore network of a leached cement paste

Pore structure of leached cement pastes (w/c=0.5) was studied for the first time from micro-scale down to the nano-scale by combining micro- and nano-X-ray computed tomography (micro- & nano-CT). This allowed assessing the 3D heterogeneity of the pore network along the cement profile (from the core to the altered layer) of almost the entire range of cement pore size, i.e. from capillary to gel pores. We successfully quantified an increase of porosity in the altered layer at both resolutions. Porosity is increasing from 1.8 to 6.1% and from 18 to 58% at the micro-(voxel=1.81μm) and nano-scale (voxel=63.5nm) respectively. The combination of both CT allowed to circumvent weaknesses inherent of both investigation scales. In addition the connectivity and the channel size of the pore network were also evaluated to obtain a complete 3D pore network characterization at both scales.

X-ray microtomography: A porosity-based thresholding method to improve soil pore network characterization?

X-ray microtomography, through quantification of soil structure at the microscale, could greatly facilitate the current understanding of soil hydrodynamic behaviour. However, binarisation method and processing choices are subjective and can have a strong impact on results and conclusions. In this study, we test a new method based on the porosity detectable by X-ray microtomography, while validation is achieved through comparison of soil microtomogram information with soil physical measurements. These measurements consist of water retention and unsaturated hydraulic conductivity using two different soil populations with only structural differences. To assess the porosity-based method performances, we compare it to four other methods, namely the global method of Otsu and three recent soil-dedicated local methods. The robustness of the porosity-based method is also tested in regard to different pre-processing procedures. In this paper we demonstrate that soil segmentation through a porosity-based method is an interesting issue. Indeed, it is less demanding in terms of time and computational requirements than its alternatives, and combines robustness and performances broadly comparable with the recent local methods.

NMR Facies Definition for Permo-Triassic Kangan/Dalan Carbonate Formation by Use of Core/Log and Pore-Scale Measurements

Summary An integrated and quantitative approach is taken here to the Permo-Triassic Kangan/Dalan carbonate formation. We apply pore-network characterization to the problem of the classification of these complex carbonate gas-reservoir rocks. We start with the useful and convenient nuclear-magnetic-resonance (NMR) data on 28 samples to define NMR facies (NMRF). The NMRF grouping is performed with both the relaxivity constant (ρ2) and the specific-surface-volume (Sgv) data. Seven NMRF have been defined with a combination of core/log NMR data, petrographic image analysis, and mercury-injection examinations for two wells. The advantage of evaluation of the pore spaces rather than grain properties is to discover trends that are not apparent when one uses a conventional sedimentological facies definition. Lithology-independent NMRF exhibit properties that are associated with pore geometry. This should have special importance for the formation evaluation of carbonates.

Nanometer to micrometer scale characterization of pore networks in fine-grained rocks using electron microscopy and small angle neutron scattering

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.