Effective porosity

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

Petrographical factors relating to porosity and permeability in the fell sandstone

Abstract: Samples of Fell Sandstone were taken from approximately every 3 m from the core material left at Shirlawhope Well, Longframlington, Northumberland. Most of the core remains and it extends to a depth of 94 m. Various analyses were made at each 3 m depth interval. These included a modal analysis, particular attention being given to the cement and matrix material, as well as the void space; and a petrographic analysis of grain packing. Grain size analyses were also carried out at each depth to determine the individual median size and sorting coefficients. The absolute and effective porosities were obtained for each depth interval, together with permeabilities of intact specimens. The results of the individual parameters were compared statistically by means of correlation coefficients and Student9s t tests in order to evaluate the significance of their relationships. Porosity and permeability were shown to be influenced by void percentage and grain packing. Particle size distribution, however, does not influence porosity, although it has some influence on permeability. Cement-matrix content has little influence on porosity. A highly significant relationship was found to exist between effective porosity and permeability. Both porosity and permeability decrease with increasing depth from the surface.

Physical properties of peat soils under different land use options

Abstract: Pristine peat soils are characterized by large porosity, low density and large water and organic matter contents. Drainage and management practices change peat properties by oxidation, compaction and mineral matter additions. This study examined differences in physical properties (hydraulic conductivity, water retention curve, bulk density, porosity, von Post degree of decomposition) in soil profiles of two peatland forests, a cultivated peatland, a peat extraction area and two pristine mires originally within the same peatland area. Soil hydraulic conductivity of the drained sites (median hydraulic conductivities: 3.3 × 10−5 m/s, 2.9 × 10−8 m/s and 8.5 × 10−8 m/s for the forests, the cultivated site and the peat extraction area, respectively) was predicted better by land use option than by soil physical parameters. Detailed physical measurements were accompanied by monitoring of the water levels between drains. The model ‘DRAINMOD’ was used to assess the hydrology and the rapid fluctuations seen in groundwater depths. Hydraulic conductivity values needed to match the simulation of observed depth to groundwater data were an order of magnitude greater than those determined in field measurements, suggesting that macropore flow was an important pathway at the study sites. The rapid response of depth to groundwater during rainfall events indicated a small effective porosity and this was supported by the small measured values of drainable porosity. This study highlighted the potential role of land use and macropore flow in controlling water table fluctuation and related processes in peat soils.

Relationship Between Porosity, Permeability, and Surface Areas of Sediments

Abstract: A study was made for the purpose of determining the relationship between the surface area, porosity, and permeability of sediments. A few tentative formulas are presented here which enable one to estimate the surface area from easily determined porosity, permeability, and formation resistivity factor.

Hydrodynamic Implications of Aquifer Quality Index (AQI) and Flow Zone Indicator (FZI) in groundwater abstraction: a case study of coastal hydro-lithofacies in South-eastern Nigeria

Abstract: We integrated the surface geologically constrained 1-D geoelectric attributes and laboratory analysis of water and hydrogeological cored samples collected from the wells in the coastal area to estimate the effective porosity, permeability and their relations with aquifer quality index (AQI), flow zone indicator (FZI) and normalised porosity index, the ingredients of aquifer dynamics. The cored samples were derived from the economic hydrogeological units and the water associated constants such as density, dynamic viscosity and acceleration due to gravity were utilised to obtain some of the geohydraulic quantities as required in the empirical relations employed. Our main preoccupation is to appraise the hydrodynamic properties which control the pore water abstracted into the wells. The estimated magnitudes of hydrodynamic properties enabled the estimation of two unique hydraulic units called the graded gravelly sands with little or no fines and well graded sands with little or no fines. The area seemed to be predominantly covered by well graded gravelly sand hydraulic unit as about 87% of the groundwater repositories investigated reflects this unit. A specific hydraulic unit has been found to conform to specific flow zone, which are important in groundwater study concerning freshwater-saltwater intrusion. The concept of stratigraphic boundaries in characterising the groundwater repositories do not account for the intra-formational variation of hydrodynamic properties in the study area as evidenced in certain ranges of permeabilities belonging to a unit flow zone indicator. The considered formations, which were all sandy and gravelly in nature, give permeability ranges that conform to the documented ranges in literature and this attests to the workability of the method. The results equally show that highly permeable sands/gravels have low tortuosity and low specific surface area of unit grain volume, which give rise to easy abstraction of water from the geo-pores. The relations between the measured and estimated parameters and the graphic details of hydrodynamic properties can be utilised in contaminant modelling of the hydrogeologic units. Management of coastal groundwater can easily be handled effectively in the single hydraulic unit than geologic units as groundwater flow in hydraulic units can furnish unique and reliable information rather than guessable information about the prime cause of contaminations in a given hydraulic unit. The classification of the hydrolithofacies is significant in the conservation and management of hydrogeologic units in the coastal zone of the study area, which is vulnerable to contaminations.