Effective porosity

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

Quantitative Discrimination of Effective Porosity Using Digital Image Analysis - Implications for Porosity-Permeability Transforms

Abstract: Five relevant digital image analysis parameters for fluid flow are obtained from 2-D image analysis of carbonate rocks: 2-D image porosity, amount of pores, pore shape, total perimeter per area and dominant pore size range. Micro-porosity leads to low permeable, highly porous rocks. 2-D image porosity represents the macro-porosity because the resolution subtracts the small pores from the porosity. Compared to the total porosity, it improves the prediction of permeability by an order of magnitude in the high porosity range. Pore shape factor γ reduces the uncertainty in permeability prediction to 2 orders of magnitude. Pore shape factor analysis is restricted to samples with more than 4000 pores/cm. CT scans of plugs reveals that the pore shape factor γ is a relatively constant measure of the pore shape (+/0.2) throughout the sample plug. The larger the average pore size, the higher the velocity at a given porosity. The average pore size can be quantified by the upper limit of the dominant pore size range.

Modelo conceitual hidroestratigráfico do sistema aquífero costeiro no litoral norte do Estado do Rio Grande do Sul

Abstract: The expansion of the knowledge of the groundwater resources is of great importance to the decision making processes with regard to management policies. The present work offers substantial contributions to the hydro-stratigraphic characterization of the Coastal Aquifer System on the north coast of the State of Rio Grande do Sul - Brazil. Aquifer geometry was determined by 38 survey profiles done by the Geological Survey of Brazil. The characterization of the different hydro-stratigraphic units was carried out through the analysis and review of geological and constructive profiles of 107 water wells and another 15 geophysical logs containing gamma, resistivity and sonic profiles. Four different hydro-stratigraphic units related to Cenozoic deposits were identified. Each of these units was defined in terms of its granulometric composition, effective porosity and total dissolved solids content of the respective groundwater. Hydro-stratigraphic units 01 and 03 showedhigh values of effective porosity and low salinity as opposed to units 02 and 04 with visibly lower values of effective porosity and higher salinities. The presence of hydro-stratigraphic heterogeneities identified here represents the fundamental scientific contribution of this work.

A petrographic coded correlation between interface conductivity and other pore space properties

Abstract: Electrical conductivity is an important property in geoscience and petroleum engineering. It gives not only information about the porosity and water saturation, but also about interfacial conductivity and about specific internal surface of the pore space. Archie’s equation correlates the electrical resistivity of a water-saturated rock sample and the resistivity of the pore water. A more detailed investigation with brine of different salinities results in the observation of interface conductivity, which is correlated to a specific internal surface. Measurements with increasing salinity of the brine were carried out on different samples: sandstone, carbonate and magmatic rocks. Additionally, permeability and effective porosity were determined. The resulting true formation factor and interfacial conductivity were then correlated with porosity and permeability. Analysis of data allows the application of the interface term as a measure of specific internal surface. For the interpretation of results, the simple capillary model a semi-empirical equation is used and delivers permeability as function of porosity, formation factor and interface conductivity. Determined permeability out of the calculations is compared with measured permeability. The developed equation which is dependent on the porosity, interface conductivity, formation factor and covers additionally the lithology influence can be used for a permeability calculation with a reasonable fit.

A Novel Relative Permeability Model for Gas and Water Flow in Hydrate-Bearing Sediments With Laboratory and Field-Scale Application.

Abstract: In a producing gas hydrate reservoir the effective porosity available for fluid flow constantly changes with dissociation of gas hydrate. Therefore, accurate prediction of relative permeability using legacy models (e.g. Brooks-Corey (B-C), van Genuchten, etc.) that were developed for conventional oil and gas reservoirs would require empirical parameters to be calibrated at various Sh over its range of variation, but such calibrations are precluded because of lack of experimental relative permeability data. This study proposes a new relative permeability model for gas hydrate-bearing media that is a function of maximum capillary pressure, capillary entry pressure, pore size distribution index, residual saturations, hydrate saturation, and four other constants. The three novel features of the proposed model are: (i) requires fitting its six empirical parameters only once using experimental data from any single Sh, and the same set of empirical parameters predict relative permeability at all Sh, (ii) includes the effect of capillarity, and (iii) includes the effect of pore-size distribution. From practical standpoint, the model can be used to simulate multiphase flow in gas hydrate-bearing sediments where the proposed relative permeability can account for the evolving hydrate saturation. The proposed model is implemented in a numerical simulator and the wall time required to perform simulations using the proposed model is shown to be similar to the time it takes to run same simulations with the B-C model. The proposed model is a step forward towards achieving the goal of physically accurate modeling of multiphase flow for gas hydrate-bearing sediments that accounts for the effect of gas hydrate saturation change on relative permeability.

Porosity Estimation From Seismic Data At Dickman Field, Kansas For Carbon Sequestration

Abstract: We present results from seismic inversion study of a 3D pre-stack seismic data volume collected over a carbonate brine reservoir in the Dickman Field, Kansas. This reservoir is a candidate for CO2 storage and therefore, the purpose of this study is to use seismic data to quantitatively estimate some reservoir parameters (porosity, permeability) of this formation. Our analyses include extensive pre-stack velocity analysis, pre-stack inversion and mapping of inversion results to porosity. Seismic inversion results together with several other attributes derived from seismic data were used in a multi-attribute linear regression to estimate an effective porosity volume. The porosity is one of the most crucial parameters in assessing different possible scenarios for injecting CO2 within this reservoir. Our results will be incorporated in a reservoir simulator to investigate different ‘what if’ time-lapse scenarios.