Effective porosity

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

Hydrogeological Characterization of Petroleum Contaminated area in Kangwon

Abstract: Estimations of porosity and bulk density, particle size analysis of soli samples, tracer test and slug test were performed in a petroleum contaminated area of Kangwon for understanding characteristics of the aquifer. Porosities of the samples were estimated 0.158~0.257, and bulk densities were estimated as . Majority proportion of the soil samples was 0.5~1.0 mm size. In the soil texture triangle, all samples were distributed at sand area. Uniformity coefficients were estimated as 7.71~10.39, and thus all samples were poorly-sorted. In the tracer test, Darcy velocity was estimated to cm/day, effective porosity was 0.175, and longitudinal dispersivity was 0.1 m. According to the slug test, hydraulic conductivities of the test wells were estimated as cm/sec. These hydrogeologic parameters can be used for efficient remediation design of the petroleum contaminated area.

A Modified Archie Relationship - A Novel Approach to Evaluate Carbonate Reservoirs with Regard to Fracture and Isolated Vuggy Porosity for Sw=1

Abstract: Carbonate rocks hosting major proportions of the world’s hydrocarbons are characterized by intricate pore systems encompassing different pore scales, shapes and interconnections resulting both from their organic origin as well as different diagenetic processes (e.g. dolomitization, fracturing, leaching, cementation or recrystallization). Apart from interparticle pore space composed of micro-, meso- and macropores, there are also separate and connected vugs (e.g. fractures), influencing important reservoir parameters such as total and effective porosity or permeability. Therefore profound knowledge of the impact of pore types and interconnections on log data has to be acquired in order to ensure accurate evaluation with respect to porosity. Particularly regarding electrical properties and Archie’s relationship – having been established for clean rocks and connecting formation resistivity factor F and total porosity – a special modification in carbonates with regard to their complex pore systems is required. Thus a petrophysical database including resistivity and porosity data of a range of carbonate rocks with various pore types (interparticle and vuggy, both separate and connected) needs to be established. The analysis of the database leads to a modified Archie relationship taking account of the effect of separate vugs and fractures on electrical current flow. This novel modification allows a first step towards porosity partitioning in a water-saturated carbonate formation into proportions that are isolated or accessible for electrical current flow and thus also for hydraulic fluid flow - one of the most important features with regard to producibility and recovery. A set of log data from a sample well is presented to apply and test this new approach on carbonates with challenging pore space characteristics. This novel modification of Archie’s equation may prove beneficial to fields of research related to reservoir properties in complex carbonate reservoirs.

Sedimentologic and Diagenetic Controls on Aquifer Properties, Lower Cretaceous Edwards Carbonate Aquifer, Texas: Implications for Aquifer Management

Abstract: The distribution of water in the Edwards aquifer was assessed using a core and log-based study. Porosity distribution reflects both depositional fabric and subsequent diagenesis. Vertical facies stacking patterns influence the depositional porosity as well as dolomitization and diagenetic porosity modification. Subtidal facies deposited during sea-level highstands are generally undolomitized and exhibit low porosity (5 to 10 percent); platform grainstones commonly have high depositional porosity and significant solution enhancement (20- to 42-percent porosity). Dolomitized subtidal facies in tidal-flat-capped cycles have very high porosity (20 to 40 percent) because of selective dolomite dissolution in the fresh-water aquifer. Porosity in former evaporite beds is high in some areas because of dissolution and collapse, but it is low where gypsum was replaced by calcite cement. Low-energy subtidal and evaporitic units in the Maverick Basin have porosities that are generally less than 15 percent. The overlying basinal packstones and grainstones have solution-enhanced porosities of 25 to 35 percent. Mapped average porosity also shows nonstratigraphically controlled variations. Diagenesis associated with fluctuations in water chemistry near the saline/fresh-water interface may be one cause. Other complex patterns of high and low porosity are attributed to structurally and hydrologically controlled porosity enhancement and cementation. Three-dimensional mapping of porosity trends provides data for improved aquifer management. Only about 3 percent of the water stored in the aquifer during a year of average water level lies above the water table at which natural spring flow is diminished. An average specific yield of 42 percent in the unconfined aquifer is determined from total porosity, changes in the water-table elevation, and changes in estimated recharge and discharge. Average storativity of 2.6 10-4 in the confined Edwards is estimated using average porosity and barometric efficiency calculated from comparing water-level hydrographs and atmospheric-pressure changes.

Quantitative Characterization of Effective Porosity in Cement-Based Composite Materials

Abstract: The method of the second intrusion mercury in MIP was used to investigate the pore characteristics of hardened cement paste with w/c ratio 0.23, 0.35 and 0.53, respectively, in order to research the quantitative relationship between transport properties and pore characteristics in cement-based composite materials. The results show the second intrusion mercury could well determine the effective pore structure parameters, and effective porosity accounts for 25% to 50% of total porosity in cement paste. At the same time, the existence of the first and second peak in pore size distribution curves is confirmed by MIP, such as, the first peak in hardened cement paste with water to cement ratio 0.53 is very distinct, however, with the decrease of water to cement ratio, the first peak gradually disappears. The pore diameter corresponding to the first and second peak is critical pore diameter of capillary pore and gel pore, respectively.