Effective porosity

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

The Nature and Classification of Carbonate Porosity

Abstract: The porosity of carbonates as compared to sandstones is vastly more complex with simple intergrain porosity dominates sandstones while carbonates commonly exhibit complex secondary pore systems that may evolve during burial. Initial porosity of carbonates is much greater than that seen in sandstones due to common intragranular porosity. Fractures, both natural and induced, are much more important in carbonates. Diagenesis is a major factor in the development of ultimate pore systems in carbonates. The geologically based Choquette–Pray carbonate porosity classification is the most commonly used scheme. Their 15 different pore types are based on fabric selectivity. A major feature of the classification is its recognition of the potential of porosity evolution through time and burial. Three porosity development zones are recognized: eogenetic, dealing with surface processes; mesogenetic, dealing with burial processes; and telogenetic, exhumed rocks dealing again with surface processes. This classification is best used during exploration, while other engineering-based classifications such as the one developed by Lucia should be used in reservoir characterization and as input for reservoir modeling. Examples of all 15 pore types are given.

An Improved Empirical Approach for Prediction of Formation Water Saturation and Free Water Level for Uni-modal Pore Systems

Abstract: Minimizing the uncertainty associated with the prediction of formation water saturation can be achieved through the integration of formation evaluation (log analysis), capillary pressure data, and pressure gradient information. To reduce the uncertainty, it is often necessary to determine porosity, permeability and water saturation using integrated methods. The magnitude of uncertainty reduction associated with predicted petrophysical parameters is a function of the inherent quality of the various data acquisition devices. Thus, reduced uncertainty in hydrocarbon pore volume can often be achieved by combining explicit probabilistic formation evaluation and a quantitative capillary pressure model. An empirical quantitative capillary pressure-water saturation model has been developed that relates the capillary pressure and height above the free water level, FWL to the wetting phase saturation. This relationship generalizes the correlation for all existing rock types that exhibit uni-modal pore geometries. The model constants are expressed as continuous functions of the interval speed that is defined as the square root of core measured permeability divided by porosity (√k/Φ) data. The water saturation is calculated continuously as a function of the height above the FWL using the log predicted permeability-porosity ratios. In the absence of a clear fluid contact, the new model provides an excellent tool for describing the fluid contacts by iterating on saturation. The FWL is adjusted until a good agreement exists between a base water saturation and the predicted water saturation from the empirical capillary pressure relationship. This paper describes the new saturation model and its application for a siliclastic layered reservoir. The model parameters are tuned based on a statistically significant number of measured high-pressure mercury injection capillary pressure curves. Furthermore, the model parameters are calibrated to data from a key well. The results of the model are then used to predict formation water saturation in neighboring wells.

Evaluation of in situ leaching processes: dual-porosity model

Abstract: A dual-porosity model is developed to study processes of in situ leaching. The model involves two overlaying continua at the macroscopic level: a permeable fracture system that determines the flow field of leach solution and a relatively impermeable matrix system that determines the leaching kinetics. The most obvious advantage of the model is that parameters it requires are minimal and easily available in practice. These parameters include the in situ hydraulic conductivity, longitudinal and transverse dispersivities, the lumped rate constant, and an empirical rock mass classification index, RQD (Rock Quality Designation). The simulation of in situ leaching processes is linked to RQD through the effective porosity of fractured media. The incorporation of RQD enables the simulation of in situ leaching processes to be carried out for a whole spectrum of ore deposits. When RQD approaches 0, it represents that the ore deposit may be a porous medium with a high effective porosity. This may reduce the double-porosity model to a single porosity model. When RQD approaches 100, it represents that the ore deposit may be considered as impermeable and unleachable. These values bound the possible ranges in behavior of the system. Based on the double-porosity model, the relation between particle size and leachability is developed, and the effects of double porosities on the concentration of a dissolved mineral are investigated. It is demonstrated through model results that the recovery rate of a valuable mineral is mainly determined by the effective porosity of the fracture pore system, the porosity of the rock matrix system, and their ratios in addition to the concentration of reagent and the ore grade.

The method of monitoring the behavior of carbon dioxide in the saline aquifer

Abstract: PURPOSE: A method of monitoring a behavior of carbon dioxide in saline aquifer using ocean electrical probing is provided to calculate an input variable needed for numerical analysis by measuring the electrical resistivity of a rock acquired for sample and pore ware CONSTITUTION: The sandstones sample is collected from the ocean floor(S10) The effective porosity of the collected sample is calculated(S20) The electrical resistivity of the collected sample is measured(S30) The electrical resistivity of the pore water with different concentration is measured(S40) An input variable for numerical analysis is obtained(S50) The strata model is set(S60) The numerical analysis using the input variable is implemented(S70)

A Retardation Factor Considering Solute Transfer Between Mobile and Immobile Water in Porous Media

Abstract: In advective-dispersive simulations of aquifers, retardation factors using linear adsorption isotherms are commonly employed to represent the adsorption-desorption process for solutes in soil. In particular, the retardation factors that use entire pore space (total porosity) or effective pore space (effective porosity) are widely used. Although another retardation factor that describes solute transfer between mobile and immobile water in porous media has been developed, characteristics of the model have not been examined extensively. This retardation factor retains the ease of use and characteristics of the first two models; for example, its breakthrough curve is similar to those generated by models that employ total porosity for aquifers in which groundwater flow is fast and solute transport by advection and mechanical dispersion is predominant, as well as models that employ effective porosity for aquifers in which groundwater flow is slow, solute transport by molecular diffusion is predominant, and a large amount of adsorption-desorption occurs. It is therefore expected that when performing advective-dispersive simulations of aquifers with complex structures (e.g., aquifers in which sand and clay layers alternate), the reproducibility of the simulation results will be improved by using the retardation factor of this latter model, which considers solute transfer between mobile and immobile water.