STRESS SENSITIVITY OF MERCURY INJECTION MEASUREMENTS

Many petrophysical properties (e.g. permeability, electrical resistivity etc.) of tight rocks are very stress sensitive. However, most mercury injection measurements are made using an instrument that does not apply a confining pressure to the samples. Here we further explore the implications of the use and analysis of data from mercury injection porosimetry or mercury capillary pressure measurements (MICP). Two particular aspects will be discussed. First, the effective stress acting on samples analysed using standard MICP instruments (i.e. Micromeritics Autopore system) is described. Second, results are presented from a new mercury injection porosimeter that is capable of injecting mercury at up to 60,000 psi into 1.5 or 1 in core plugs while keeping a constant net stress up to 15,000 psi. This new instrument allows monitoring of the electrical conductivity across the core during the test so that an accurate threshold pressure can be determined. Although no external confining pressure is applied (unconfined) when using the standard MICP instrument, this doesn’t mean that the measurements can be considered as unstressed. Instead, the sample is under isostatic compression by the mercury until it enters the pore space of the sample. As an approximation, the stress that the mercury places on the sample is equal to its threshold pressure. Thus, the permeability calculated from standard MICP data is equivalent to that measured at its threshold pressure. Not all the samples have the same stress dependency thus comparing measured permeabilities at a single stress with values calculated from standard MICP data, corresponding at different threshold pressures, can lead to erroneous correlations. Therefore, the estimation of permeabilities from standard MICP data can be flawed and uncertain unless the stress effect is included. Results obtained from the new mercury injection system, porosimeter under net stress, are radically different from those obtained from standard MICP instruments such as the Autopore IV. In particular, the measurements at reservoir conditions produce threshold pressures that are three times higher and pore throat sizes that are 1/3rd of those measured by the standard MICP instrument. The results clearly indicate that calculating capillary height functions, sealing capacity, etc. from the standard instrument can lead to large errors that can have significant impact on subsurface characterization

Social factors, diet and breast cancer in a northern Italian population.

The relation of breast cancer to social and dietary variables was evaluated in a case-control study of 368 women with breast cancer admitted to the General Hospital of Pordenone (a town in the eastern side of Northern Italy) and 373 age-matched controls. Occupation was related to the risk of breast cancer, housewives and non-manual workers (teachers and other professionals, clerical workers, etc.) showing relative risks of 1.7 and 2.4 respectively when compared to women occupied in agriculture. The role of education was apparently less important, and not statistically significant. The risk was higher in women who were obese, the trend of increasing risk with increasing body mass index being confined to post-menopausal women. When indicators of dietary fat intake were analysed, a significantly increased risk was found with more frequent consumption of milk and dairy products but the risk estimates were only slightly above unity with reference to meat consumption. Women who drank alcoholic beverages showed a relative risk of 2.5 compared to women who had never drunk, when allowance was made for all identified potential confounding factors. The association between alcohol and breast cancer was not explained by the other dietary variables considered, and the risk estimates were higher for women who drank more wine, or more than one type of alcoholic beverage. Thus, the findings of the present study give evidence in favour of the hypothesis that alcohol consumption is related to the risk of breast cancer

Gold nanoparticles radio-sensitize and reduce cell survival in lewis lung carcinoma

It has been suggested that particle size plays an important role in determining the genotoxicity of gold nanoparticles (GNPs). The purpose of this study was to compare the potential radio-sensitization effects of two different sized GNPs (3.9 and 37.4 nm) fabricated and examined in vitro in Lewis lung carcinoma (LLC) as a model of non-small cell lung cancer through use of comet and clonogenic assays. After treatment with 2Gy X-ray irradiation, both particle sizes demonstrated increased DNA damage when compared to treatment with particles only and radiation alone. This radio-sensitization was further translated into a reduction in cell survival demonstrated by clonogenicity. This work indicates that GNPs of both sizes induce DNA damage in LLC cells at the tested concentrations, whereas the 37.4 nm particle size treatment group demonstrated greater significance in vitro. The presented data aids in the evaluation of the radiobiological response of Lewis lung carcinoma cells treated with gold nanoparticles

Nonadditivity of critical Casimir forces

In soft condensed matter physics, effective interactions often emerge due to the spatial confinement of fluctuating fields. For instance, microscopic particles dissolved in a binary liquid mixture are subject to critical Casimir forces whenever their surfaces confine the thermal fluctuations of the order parameter of the solvent close to its critical demixing point. These forces are theoretically predicted to be nonadditive on the scale set by the bulk correlation length of the fluctuations. Here we provide direct experimental evidence of this fact by reporting the measurement of the associated many-body forces. We consider three colloidal particles in optical traps and observe that the critical Casimir force exerted on one of them by the other two differs from the sum of the forces they exert separately. This three-body effect depends sensitively on the distance from the critical point and on the chemical functionalisation of the colloid surfaces

One-Dimensional Modelling of Polymer Flood Performance. Analytical and Graphical Solutions Modélisation de l'efficacité du déplacement unidimensionnel par injection de polymères. Solutions analytiques et graphiques

A graphical method for simulating linear polymer flooding is proposed. The method is based upon the analytical solution of Darcy's law and continuity equation which describe the two-phase, one-dimensional, incompressible flow of oil and polymer solution through the reservoir rock. Continuous polymer injection and polymer slug injection are considered. Several physical mechanisms determining microscopic displacement efficiency are taken into account: resistance factor, residual resistance factor, retention composed by adsorption and mechanical entrapment, and inaccessible pore volume. Other properties are not considered: mixing and dispersion, shear and thermal degradation. This analytical-graphical model closely reproduces linear laboratory oil displacement experiments. Consequently, it can be used by the Field Engineer to rapidly estimate the additional oil recoverable by a linear polymer flood. On propose dans cet article une méthode graphique de simulation de l'injection de polymères dans le cas unidimensionnel. Cette méthode est basée sur la solution analytique de la loi de Darcy et de l'équation de continuité qui décrivent l'écoulement diphasique incompressible unidimen-sionnel d'huile et d'une solution de polymères à travers la roche réservoir. On examine l'injection continue et l'injection de bouchons de polymères. On prend en compte plusieurs mécanismes physiques qui déterminent l'efficacité du déplacement microscopique : facteur de ré-sistance, facteur de résistance résiduel, rétention due à l'adsorption et au piégeage mécanique et, enfin, volume des pores inacessibles. On ne tient pas compte des autres propriétés : mélange et dispersion, dégradation mécanique et thermique. Ce modèle analytique et graphique reproduit très directement les expériences de laboratoire de déplacement d'huile en milieu unidimensionnel. II peut donc être utilisé par l'ingénieur de chantier pour une estimation rapide de l'huile récupérable supplémentaire par l'injection linéaire de polymères

One-Dimensional Modelling of Polymer Flood Performance. Analytical and Graphical Solutions

A graphical method for simulating linear polymer flooding is proposed. The method is based upon the analytical solution of Darcy's law and continuity equation which describe the two-phase, one-dimensional, incompressible flow of oil and polymer solution through the reservoir rock. Continuous polymer injection and polymer slug injection are considered. Several physical mechanisms determining microscopic displacement efficiency are taken into account: resistance factor, residual resistance factor, retention composed by adsorption and mechanical entrapment, and inaccessible pore volume. Other properties are not considered: mixing and dispersion, shear and thermal degradation. This analytical-graphical model closely reproduces linear laboratory oil displacement experiments. Consequently, it can be used by the Field Engineer to rapidly estimate the additional oil recoverable by a linear polymer flood

Análisis de las soluciones numéricas de la ecuación de convección - dispersión - adsorción

La ecuación diferencial parcial no lineal que describe el flujo bicomponente miscible a través de medios porosos, con dispersión y adsorción del tipo Langmuir, se resuelve numéricamente. Se aplican cuatro métodos diferentes: explícito, Barakat-Clark, Crank- Nicolson y ecuaciones diferenciales ordinarias. Se estima el error de truncación de los distintos métodos. Se obtienen las condiciones de estabilidad de los mismos para el caso de adsorción lineal y se infieren las condiciones de estabilidad para la ecuación no lineal. A efectos de comparar los cuatro métodos, se siguen dos caminos. Primero, se define un error global que evalúa las diferencias entre cada una de las soluciones numéricas y la solución analítica que representa el caso de adsorción lineal. Utilizando este error se comparan las soluciones numéricas entre sí. Además se estudia la influencia de los parámetros de la ecuación diferencial y de los incrementos espaciales y temporales de la discretización en las soluciones obtenidas. En especial, se discute el método Barakat-Clark. Segundo, para la ecuación con adsorción no lineal, las cuatro soluciones numéricas se comparan contra resultados experimentales, por medio de un error que evalúa las diferencias entre cada solución y los datos experimentales.Peer Reviewe