Non-connected Pores Research Articles

Microstructural characteristics of the Whitby Mudstone Formation (UK)

When trying to improve gas productivity from unconventional sources a first aim is to understand gas storage and gas flow potential through the rock by investigating the microstructure, mineralogy and matrix porosity of unfractured shale. The porosity and mineralogy of the Mulgrave Shale member of the Whitby Mudstone Formation (UK) were characterized using a combination of microscopy, X-ray diffraction and gas adsorption methods on samples collected from outcrops. The Whitby Mudstone is an analogue for the Dutch Posidonia Shale which is a possible unconventional source for gas. The Mulgrave shale member of the Whitby Mudstone Formation can microstructurally be subdivided into a fossil rich (>15%) upper half and a sub-mm mineralogically laminated lower half. All clasts are embedded within a fine-grained matrix (all grains < 2 μm) implying that any possible flow of gas will depend on the porosity and the pore network present within this matrix. The visible SEM porosity (pore diameter > 100 nm) is in the order of 0.5–2.5% and shows a non-connected pore network in 2D. Gas adsorption (N2, Ar, He) porosity (pore diameters down to 2 nm) has been measured to be 0.3–7%. Overall more than 40% of the visible porosity is present within the matrix. Comparing the Whitby Mudstone Formation to other (producing) gas shales shows that the rock plots in the low porosity and high clay mineral content range, which could imply that Whitby Mudstone shales could be less favourable to mechanical fracturing than other gas shales. Estimated permeability indicates values in the micro-to nano-darcy range.

Effect of functional chemical admixtures on the performance of cement asphalt mortar used in ballastless track

Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement asphalt mortar (CA mortar), i e, compressive strength, frost resistance, permeability, fatigue resistance, pore structure and microstructure. In particular, two types of chemical admixtures were tested, i e, defoamer (tributyl phosphate (TBP)) and polycarboxylate superplasticizer (PS). The results indicate that the addition of TBP and PS eliminates big bubbles and promotes small non-connected pores forming in matrix. Besides, an optimum dosage of TBP and PS may be determined with respect to the frost resistance, permeability and fatigue resistance of CA mortar. Further elaborative discussions are presented as well as experimental evidences from mercury intrusion porosimetry, scanning electron microscopy and energy dispersive spectroscopy.

Proportioning and characterization of Portland cement-based ultra-lightweight foam concretes

Due to desirable thermal insulation properties, superior fire-resistant and higher durability, ultra-lightweight foam concretes are recommended to achieve energy efficiency in buildings. Generally, aluminate cement, sulphoaluminate cement and other quick hardening cementitious materials are used to control the stability of air-voids in foam concretes. These special cementitious materials are relatively expensive and not universally available, retarding the application and popularization of foam concretes. In the present study, the proportioning and properties of Portland cement-based ultra-lightweight foam concrete were investigated. The results show that ultra-lightweight foam concretes with apparent density of 100–300kg/m3 can be prepared using Portland cement, fly ash, hydrogen peroxide and chemical admixtures. Collapse and air-voids escape can be avoided by adding thickening agent and foam stabilizing emulsion into foam concretes. Most of pores in ultra-lightweight foam concretes were non-connected pores with size of 2.0–4.0mm, resulting in a lower thermal conductivity, desirable compressive and tensile strengths.

Adsorption in alumina pores open at one and at both ends.

We have studied adsorption in regular, self-ordered alumina pores open at both ends or only at one end. The straight, non-connected pores have diameters ranging from 22 to 83 nm, with a relative dispersion below 1% in the pore size. Adsorption isotherms measured in open pores with a torsional microbalance show pronounced hysteresis loops characterized by nearly vertical and parallel adsorption and desorption branches. Blocking one end of the pores with glue has a strong influence on adsorption, as expected from classical macroscopic arguments. However, the experimental measurements show an unexpectedly rich phenomenology dependent on the pore size. For large pores (Dp ≥ 67 nm), the isotherms for closed end pores present much narrower hysteresis loops whose adsorption and desorption boundaries envelop the desorption branches of the isotherms for the corresponding open pores of the same size. The loop for small closed end pores (Dp = 22 nm) is slightly wider than that for open pores while the adsorption branches coincide. For large pores, in contrast, the desorption branches of pores with the same Dp overlap regardless of the pore opening. These observations are in agreement with our grand canonical Monte Carlo (GCMC) simulations for a cylindrical pore model with constrictions, suggesting that the alumina pores could be modeled using a constricted pore model whose adsorption isotherm depends on the ratio of the constriction size to the pore size (Dc/Dp).

Comparison of pore space features by thin sections and X-ray microtomography

Microtomographic (µCT) and thin section (TS) images were analyzed and compared regarding porosity and its distribution along the samples. The results show that µCT, although limited by its resolution, shows relevant information about the distribution of porosity and quantification of connected and non-connected pores. TS have no limitations concerning resolution, but are limited by the experimental data and can only give information about connected pores. These two methods have their own advantages but when paired together they are able to make for a more complete analysis.

From outcrop to 3D modelling: a case study of a dolomitized carbonate reservoir, Zagros Mountains, Iran

ABSTRACT Outcrop data derived from fieldwork, remote sensing satellite and LiDAR-derived 3D models were used to build an integrated dual porosity-permeability static reservoir model which captured stratigraphic, diagenetic and structural heterogeneities. The study focuses upon the Mishrif-Mauddud/Sarvak interval, one of the most prolific reservoir units in the Middle East. The study area is exceptionally well exposed in deep gorges which cut transversally across anticlines of the Simply Folded Belt of the Zagros Mountains. The outcrops reveal volumetrically significant dolomitization of the latest Albian to Turonian carbonates of the Lower and Upper Sarvak formations. Three different dolomite bodies, which are spatially connected and genetically linked to the same fluid flow event, were recognized and mapped: (1) a thick dolomite body replacing the Lower Sarvak and forming a massive dolomite core; (2) horizontally extensive stratabound dolomite bodies (sheets), emanating laterally from the massive dolomite; and (3) vertically elongated dolomite pipes, rooted in the massive dolomite and typically replacing slope facies of the Upper Sarvak Formation. The widespread development of tight, non-planar dolomite textures (a typical feature of high temperature dolomitization) drastically reduces the reservoir potential of the dolomitized geobody in the study area. In particular, this is present in the massive dolomitized body. Vuggy porosity seems to increase porosity only locally and to a limited extent, developing a non-connected pore network. The dominant porous dolomite textures are more abundant in the peripheral part of the geobody (dolomite sheets), where they are strongly controlled by precursor facies and diagenesis. Three main dolomite pore types were identified (intercrystalline, interparticle and mouldic), linked to the depositional environment of the precursor limestone. These pore types were used for petrophysical modelling. The approach adopted in this study allowed the distribution of rock properties in the dolomitized geobody to mimic the main depositional facies architecture. The study area is characterized by a simple fracture network. Two main fracture sets and two major sets of conjugate normal faults were recognized in the field and mapped on 3D virtual outcrop data. Non-stratabound fracture density varied according to stratigraphic unit and/or dolomite body type (pipes/massive/sheets), showing a general increase from precursor limestone to dolomite. Fracture density also varied according to distance from faults (fault damage zone). This was particularly true in the limestone. The data also showed a prominent increase in fracture height from limestone to dolomite bodies, indicating that the dolomitized geobodies are likely sites for high production and early water breakthrough.

Flow Study in a Double Porosity Medium Containing Ellipsoidal Occluded Macro-voids

This paper presents an analytical study of permeability evolution in a dual length-scale porous medium: at the smallest or microscopic scale, connected inter-layer and inter-particular voids are present within the clay matrix, while at the upper or mesoscopic scale, non-connected inter-aggregate pores are present. By assuming ellipsoidal shapes for the macro-voids and low concentrations in macro-voids, analytical expressions are derived for the effective permeability tensor at the macroscopic scale, based on the analysis of fluid flow at pore level. The permeability tensor is obtained solely from the study of fluid flow in the clay matrix performed in Part I, without the need of solving Stokes’ equations in the inter-aggregate void space. The analytical permeability depends on the macro-porosity and the eccentricity ratio, and its evolution with both parameters is investigated over the range of validity of the analytical solution, that is, for porosity values lower than 10% and eccentricity ratios allowing non-connectedness of the macro-voids. Comparisons are also made with existing correlations between permeability and porosity. The analytical expressions obtained are applied to permeability predictions in pure bentonite clay, saturated and mechanically compacted under high pressures, and soaked by pollutant solutions.

Osteoblast response to plasma-spray porous Ti6Al4V coating on substrates of identical alloy

We have evaluated the in-vitro biocompatibility of Ti6Al4V alloy coated by plasma spraying with an identical alloy. These surfaces are widely used in cementless prosthetic components, although osteoblasts behavior on this treated alloy has not been evaluated to date. Cross sectional examination revealed a thick and rough coating of identical composition without sign of delamination. Within the coating, small discontinuities and nonconnected pores were observed. Osteoblast response was evaluated by assessing cell adhesion, proliferation, and differentiation of primary cultures of human osteoblastic cells. Compared to the polished alloy, osteoblast adhesion measured as cell attachment and actin network reorganization was delayed on the plasma-sprayed surface. Cell proliferation and viability were also impaired on the rough surface. Several informative markers of osteoblastic differentiation such as procollagen I peptide, alkaline phosphatase, osteocalcin, osteoprotegerin, and mineralized nodule formation were evaluated and indicated that the plasma-sprayed alloy favored a more differentiated phenotype than polished alloy. Taken together, our in vitro results indicate that successful osseointegration of plasma spraying of Ti6Al4V with an identical alloy is mediated by modulation of osteoblastic differentiation and mineralization.

Pore Size Distribution of Porous Glasses: A Test of the Independent Pore Model

Using the Kierlik and Rosinberg fundamental measure theory, we test the density functional theory method for determination of pore size distributions from adsorption data for porous glasses. The glasses chosen for study are model glasses prepared by a quench molecular dynamics method that mimics the experimental synthesis process and are completely characterized at the molecular level. The density functional method involves two approximations: (a) the glasses can be regarded as made up of a distribution of nonconnected pores of simple geometry, which we refer to as the independent pore model, and (b) the adsorption isotherms for these nonconnected pores can be described by the density functional theory. Using simulated adsorption isotherm data for the glasses and adsorption isotherms for the pores of simple geometry calculated by the density functional theory, a regularization method is used to determine the pore size distribution from the adsorption data. These calculated pore size distributions, as well as the adsorption isotherms for the materials, are compared with the exact geometric pore size distributions for the material and with the simulated isotherms. Both slit-shaped and cylindrical pores are used in the density functional theory method. It is found that a unique geometry is not able to accurately describe the whole adsorption isotherm. The use of slit-shaped pores gives overall better results, although the low-pressure regime is more accurate when cylindrical pores are used; reasons for this are discussed. The pore size distributions from the density functional theory are in reasonable agreement with the geometrical ones, giving the same shape and mean pore width and similar porosities in the four materials. Since it is known that the density functional theory gives excellent results for the adsorption isotherms (approximation b above), this comparison tests the independent pore model directly.

Effects of drying on Amazonian ferralsols and podzols. Determination of water desorption curves from mercury porosimetry

We established pedotransfer functions to define the water desorption curve from MIP, organic carbon content, and bulk density (table I and II). These functions can be used for soils with the following characteristics, thus for most tropical soils: - negligible fine clay (< 0.2 [nu]m) content, in order to enable the extrapolation of nanopore volume from MIP, without needing nitrogen desorption [Bruand and Prost, 1987]; - soils mainly composed of kaolinite and quartz. The organic carbon content has little influence on the humic podzol studied here, so the equations established here are pertinent for other podzols. These pedotransfer functions give information on the structure of these soils : - residual and micro- porosities modify between MIP and water desorption, according to the organic carbon content and the texture of clay (given by the average textural pore size), with the same law for all soils; - mesoporosity changes according to two different types of structure : (1) clay microaggregates for clayey soils, (2) sandy fabric for podzol, loose at depth due to eluviation of parent clay, consolidated near the surface by pedoturbation; - total porosity follows, with an attenuation, the changes in the MO-linked porosity and in the porosity linked to soil structuring particles, that is the residual porosity for clayey soils, and the mesoporosity for podzols; - macroporosity, in reality as in the equations, compensates for the difference. This method could be tested on soils with other granulometry, mineralogy, or higher OM content. This work was supported by IRD and the PEGI and PROSE programs, we thank Max Sarrazin for his technical collaboration and the reviewers for their critical reading.