Effective porosity

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

Using particle density of a container medium to determine accuracy of bulk density and total porosity determinations

Abstract: The total porosity of a container medium is often inaccurate when determined from a water release curve because the use of the total porosity value and bulk density in the equation, Total porosity = (1 ‐ bulk density/particle density) x 100, gives an unrealistic value for particle density. The inaccuracy seems to be caused by incomplete saturation of the medium sample at zero suction. Total porosity should be calculated using bulk density and particle density, rather than equating total porosity with the zero suction value on the water release curve. The zero suction value is a measure of effective porosity since it does not take into account trapped air in the medium.

Relationship of Sandstone Diagenesis and Relatively High Porosity Areas in Nantun and Tongbomiao Formation:A Case from the Southern of Wuerxun Depression in Hailaer Basin

Abstract: The types of sandstone from Nantun and Tongbomiao Formation of Wuerxun depression in Hailaer basin are mainly debris-feldspar sandstone,sightly feldspar sandstone and feldspar-debris sandstone.The diageneses include compaction,cementation,metasomatism and dissolution,etc.With depth increasing,the porosity and permeability decrease.There are four relatively high porosity arears in about 1 500 m,1 850-2 050 m,2 300 m and 2 600-2 800 m.The reasons of relatively high porosity areas appearance are the preservation of primary porosity and the development of secondary porosity.The weakness of compaction and cementation,existence of clay coating and microcrystalline quartz are favor to the preservation of primary porosity;in the processing of thermal evolution of organic content and the conversion of clays,secondary porosity forming occurs.

Effects of Temperature and Water Pressure on the Material Properties of Granite & Limestone from Gagok Mine

Abstract: This study focuses on having a temperature and water pressure effects on the change of material properties of rocks. Granite and limestone specimens from Gagok Mine were thermally treated with predetermined temperatures of 200, 300, 400, 500, 600 and 700℃ (excepting 700℃ for limestone) to estimate the reduction of material properties of rocks caused by heat. Specific gravity, effective porosity, elastic wave velocity, uniaxial compressive strength, Young’s modulus and Poisson's ratio for pre-heated specimens were measured. With increasing temperature, material properties of both rock specimens change sequentially. Significant changes of specific gravity, effective porosity and elastic wave porosity occur above 400℃ for granite and 300℃ for limestone. Changes of uniaxial compressive strength, Young’s modulus and Poisson’s ratio seem to be similar to those of physical properties. GSI of 500, 600 and 700℃ specimens inferred by using uniaxial compressive strength and Young's modulus of preheated granite specimens is found to be 81, 66 and 58 each. In case of pre-heated limestone specimens of 400, 500 and 600℃, the corresponding GSI is 76, 71 and 65 each. 500, 600 and 700℃ granite specimens and 400, 500 and 600℃ limestone specimens were pressurized to 7.5 MPa and their effective porosity, elastic wave velocity, uniaxial compressive strength and Young’s modulus were measured. The average value of material properties (mentioned above) of 500, 600 and 700℃ granite specimens under water pressure compared with material properties of non-pressurized pre-heated specimens exhibits the reduction of 7.6, 11.3 and 14.9%, respectively. In case of 400, 500 and 600℃ limestone specimens under water pressure, the average value of material properties decreases by 8.2, 13.8 and 21.9%, respectively.

A procedure for delineation of bedrock fracture zones under glacial drift formations in ohio

Abstract: In any aquifer the porosity can be either primary or secondary or a combination of the two, referred to as dual porosity. Primary porosity is the diffused, inter-granular porosity inherent to the rock, generated at the time of lithogenesis. Secondary porosity is the porosity created by post-genetic processes, e.g. fracturing or dissolution of the rock. Rates of groundwater production from bedrock sandstone units are commonly directly related to the presence and extent of secondary porosity. Bedrock fracturing can be product of tectonic stress or, in recently glaciated areas, unloading from the retreat of glaciers. The goals of our study were to test the hypothesis that the values of hydraulic conductivity, computed from the data stored in water well archives for single-home water wells penetrating bedrock sandstone formations may delineate mappable areas of high hydraulic conductivity, thus showing the distribution of fracture zones. We analyzed ninety-one well logs of private single-home water wells drilled through the glacial sediments into the sandstone bedrock formations in Geauga and Portage Counties of Northeastern Ohio. Aquifer thickness in each water well was determined from the lithological profiles, while the specific capacity data from production tests were used to estimate the values of the coefficient of transmissivity for each well. Combination of the two parameters yielded mappable values of hydraulic conductivity. The resulting values of hydraulic conductivity were characterized by a distinctly binary distribution, with low values apparently corresponding to massive un-fractured zones and high values corresponding to fractured zones with dual porosity. Once contoured on a map, these zones appeared clearly, with a transition between the areas of high and low hydraulic conductivity, i.e. high and low potential for groundwater production, respectively.

The lower limits of physical properties for deep clastic reservoirs in north Songliao basin and its relationship with microscopic features

Abstract: Based on the research on lithology,physical properties, pore structure,and pore microscopic features of sandstone and conglomerate reservoirs with different productivity,the porosity permeability versus productivity charts for sandstone and conglomerate have been established with the consideration of gas testing results.According to the research,the lower limits of effective porosity and permeability for reservoirs where oil can be accumulated and produced are determined.The lower limit of porosity for sandstone is 4.1%5.5%,and that of permeability is 0.06×10-3μm2.The lower limit of porosity for conglomerate is only 2.7%,and that of permeability is 0.05×10-3μm2,because the single conglomerate layer is thick,the microfractures are vegetal and the expulsion pressure is low.Further study indicates that the difference of the main pore type,capillary pressure curve characteristics,diagenetic features and the dominant factors for reservoirs between the gas pay and dry formation results in the gas-bearing difference of reservoirs.Due to the great difference of microscopic features,such as pore type and expulsion pressure,between sandstone and conglomerate,the lower limits of physical properties vary greatly.