Effective porosity

About: Effective porosity is a research topic. Over the lifetime, 1199 publications have been published within this topic receiving 26511 citations.

Validated Leverett Approach for Multiphase Flow in PEFC Diffusion Media I. Hydrophobicity Effect

Abstract: This work is the second part of a series of papers to describe the multiphase transport mechanism in thin-film polymer electrolyte fuel cell ! PEFC" diffusion media ! DM" . The present work is devoted to delineating the effects of compression. Direct measurements of drainage capillary pressure-saturation curves for SGL series carbon paper DM tailored with a range of mixed wettability were performed at room temperature under various compressions ! 0, 0.6, and 1.4 MPa" typically encountered in a fuel cell assembly. Based on these benchmark data, an appropriate form of the Leverett approach, including a Leverett-type empirical function that incorporates the effect of compression and the mixed wettability characteristics of the tested DM samples, was developed. The presented approach can determine the capillary pressure as a function of hydrophobic additive content, liquid saturation, compression, and uncompressed porosity of the DM. Compression leads to an increase in capillary pressure, effectively caused by the corresponding reduction in effective porosity. Any increase in hydrophobicity amplifies the compression effect, yielding a higher capillary pressure for the same saturation level. Furthermore, the fraction of connected hydrophilic pores is observed to be reduced with an increase in compression, leading to a favorable reduction in water storage capacity of the fuel cell DM.

High-Porosity Cenozoic Carbonate Rocks of South Florida: Progressive Loss of Porosity with Depth

Abstract: Porosity measurements by borehole gravity meter in subsurface Cenozoic carbonates of south Florida reveal an extremely porous mass of limestone and dolomite which is transitional in total pore volume between typical porosity values for modern carbonate sediments and ancient carbonate rocks. A persistent decrease of porosity with depth, similar to that of chalks of the Gulf Coast, occurs in these rocks. We make no attempt to differentiate depositional or diagenetic facies which produce scatter in the porosity-depth relationship; the dominant data trends thus are functions of carbonate rocks in general rather than of particular carbonate facies. Carbonate strata with less than 20% porosity are absent from the rocks studied here. Aquifers and aquicludes cannot be distinguished on the basis of porosity. Although aquifers are characterized by great permeability and well-developed vuggy and even cavernous porosity in some intervals, they are not exceptionally porous when compared to other Tertiary carbonate rocks in south Florida. Permeability in these strata is governed more by the spacial distribution of pore space and matrix than by the total volume of porosity present. Dolomite is as porous as, or slightly less porous than, limestones in these rocks. This observation places limits on any model proposed for dolomitization and suggests that dolomitization does not take place by a simple ion-for-ion replacement of magnesium for calcium. Dolomitization may be selective for less porous limestone, or it may involve the incorporation of significant amounts of carbonate as well as magnesium into the rock. The great volume of pore space in these rocks serves to highlight the inefficiency of early diagenesis in reducing carbonate porosity and to emphasize the importance of later porosity reduction which occurs during the burial or late near-surface history of limestones and dolomites.

A water absorption test for concrete

Abstract: Synopsis The durability of concrete near an exposed surface is largely determined by the rate at which harmful agents can penetrate into the concrete. This paper presents a simple analysis of the penetration of' water into unsaturated concrete and describes a method by which the material constant that determines the rate of penetration, the sportively, can be measured, together with the effective porosity. The sorptivity is found to depend on the permeability and porosity of the concrete and the strength of capillary forces. The experimental results conform well to the predictions of the analysis and significant variations in sorptivity have been observed for concrete containing cement replacement materials and subject to different curing regimes.

Incorporating capillary pressure, pore throat aperture radii, height above free-water table, and Winland r35 values on Pickett plots

Abstract: Methods are presented for incorporating capillary pressure, pore throat aperture radii, height above the free-water table, and Winland r 35 values on Pickett plots. The techniques involve the use of log-log plots of effective porosity vs. resistivity combined with empirical equations for calculating capillary pressure written as a function of permeability, porosity, and water saturation. I show that a crossplot of porosity vs. true resistivity (in some cases apparent resistivity or true resistivity affected by a shale group) should result in a straight line for intervals with constant capillary pressure and constant pore throat aperture radii. Key advantages of the proposed methods are (1) the capillary pressure at any point on the Pickett plot is consistent with porosity, permeability, and water saturation at that particular point; (2) the value of R w does not have to be known in advance, provided that the reservoir contains some water-bearing intervals; and (3) core data are not essential, although it is strongly recommended to have cores to properly calibrate the equations presented in this article. If capillary pressures from cores are available, it is possible to estimate the value of R w even if there are not water-bearing intervals in the reservoir. Pore throat aperture radii ( r 35) values computed using the empirically derived Winland equation compare reasonably well with pore throat aperture radii ( r p35) calculated from techniques presented in this article. This is significant because the data sets used to establish these empirical equations come from different areas, different reservoirs, and different lithologies and were evaluated independently at different times. A mathematical relationship is developed between Winland r 35 values and the pore throat aperture r p35 presented in this article. The methods are illustrated using two case histories. The first one is a Gulf Coast high-porosity sand-shale sequence. The second is a limestone oil reservoir from the Lansing Kansas City formation. The integration of permeability, capillary pressures, pore-size classes, and geometry of the pores on a log-log graph of porosity vs. resistivity makes the Pickett plot one of the most formidable formation evaluation tools yet devised. Roberto Aguilera is president of Servipetrol Ltd. in Calgary, Canada. He has an undergraduate degree in petroleum engineering from the Universidad de America in Bogota, Colombia, and a master's degree and Ph.D. in petroleum engineering from the Colorado School of Mines. He was an AAPG instructor on the subject of naturally fractured reservoirs from 1984 through 1996. He received the Outstanding Service Award from the Petroleum Society of the Canadian Institute of Mining, Metallurgy and Petroleum Engineers (CIM) in 1994. He is a Distinguished Author of the Journal of Canadian Petroleum Technology (1993 and 1999) and a Society of Petroleum Engineers Distinguished Lecturer on the topic "Naturally Fractured Reservoirs" for the 2000-2001 season. He has developed various methods that have been published in leading journals of the oil industry. He has authored and been a contributor to various books, including Naturally Fractured Reservoirs (PennWell, 1980 and 1995), The Technology of Artificial Lift Methods (PennWell, 1984), Horizontal Wells (Gulf Publishing, 1991), and Determination of Oil and Gas Reserves (Petroleum Society of CIM Monograph 1, 1994).