Average Relative Permeability Research Articles

A note on dynamic rock typing and TEM-function for grouping, averaging and assigning relative permeability data to reservoir simulation models

For years, rock typing based on two-phase flow characteristics was mainly founded on grouping primary drainage capillary pressure curves, while rock classification based on relative permeability measurements and its practical applications were overlooked. Recently, a dynamic rock typing approach was proposed by defining a True Effective Mobility tool (TEM-function) to convert relative permeability data to fluid flow indicators. This technical note sheds further light on the concept of dynamic rock typing and TEM-function. Moreover, in previous studies the fact that how identified petrophysical dynamic rock types (PDRTs) and their corresponding average relative permeability tables should be assigned to simulation grid cells was not addressed. We accordingly investigate whether a general property can be found to assign average relative permeability data to grid cells. For this purpose, we apply TEM-function to identify PDRTs and present average relative permeability tables using gas-oil relative permeability experiments on a subset of carbonate samples. We also analyze the PDRTs in a counter-part water-oil system and investigate their relationship with gas-oil PDRTs. Results show that the recent dynamic rock typing approach incorporates forward and inverse processes that are physically meaningful and consistent with laboratory analysis and reservoir simulation processes. The strong dependency of TEM-function on the ratio of permeability to porosity enables us to introduce a general property to assign average relative permeability data to grid cells. Furthermore, while PDRTs in the gas-oil systems were almost identical, PDRTs in the water-oil system were dissimilar and different from the gas-oil counterpart. This confirms that each saturation function needs its specific rock typing scheme.

New technique of True Effective Mobility (TEM-Function) in dynamic rock typing: Reduction of uncertainties in relative permeability data for reservoir simulation

Performance predictions made by reservoir simulators are highly dependent on experimentally-determined relative permeability data assigned to simulation grid cells. There is often no apparent relationship between this type of data and a quantifiable property of cells, meaning that samples within a group of neighboring relative permeability curves do not have similar values of a common characterization property. On the other hand, it is easier to correlate primary drainage capillary pressure data to cell properties and create a petrophysical static rock type (PSRT) from a group of similar capillary pressure data. The common approach is to average the relative permeability data corresponding to each PSRT and input that into a simulator. In practice, relative permeability curves corresponding to a given PSRT would exhibit a significant scatter, especially in carbonate formations. This will cause the resulting average relative permeability data to be highly uncertain and poorly representative of true dynamic behavior of the cells.In this study, a new technique is proposed to reduce uncertainties associated with classical methods of assigning relative permeability data to grid cells of a simulation model. The idea is based on a robust and universal criterion for characterization of dynamic characteristics of rocks from laboratory-derived flow data to define a petrophysical dynamic rock type (PDRT). A PDRT is defined as a collection of rocks with similar True Effective Mobility (TEM) behavior. A TEM-function for analysis of relative permeability is defined as a product of relative mobility by the square of a mean pore radius, and is analogous to the well-known J-function for scaling capillary pressure curves. For a given PDRT, a special weighted average of corresponding relative permeability data, or average TEM data should be used as input to a simulator. In the latter case, the simulator should have the capability to back-calculate cells’ quasi-relative permeabilities using the inputted average TEM data. Moreover, we show that factors such as wettability and pore-scale heterogeneity can cause phase-dependent dynamic characteristics (i.e., different dynamics with respect to each fluid phase). Hence, different dynamic rock typing schemes should be applied to the flow of each fluid in system. A structured methodology is presented to identify PDRTs using TEM-function and prepare input parameters to simulators by analyzing relative permeabilities using the universal criterion developed in this work. Ultimately, special core analysis data from the Asmari Formation, a carbonate reservoir from one of the Iranian Fields, is used to verify and demonstrate the applicability of the presented technique.

A flood susceptibility model at the national scale based on multicriteria analysis

River flooding is a specific worldwide type of flooding responsible for considerable human and material losses. An extensive knowledge about flood conditioning factors and a diverse set of methodologies for flood susceptibility evaluations are available, although there is still field for improvement regarding methodologies for small-scale flood susceptibility assessment, particularly relevant in data-scarce contexts.This research applied to mainland Portugal, introduces a multicriteria methodology to assess flood susceptibility at national scale considering three flood-conditioning factors: flow accumulation, average slope angle and average relative permeability. These three factors resume other factors usually considered in literature, related to morphology and potential runoff. This work includes data from the flood conditioning factors considering the cumulative role of the entire contributive area and not only the on-site characteristics. The weight of each factor was assigned based on expert opinion and validated using available flood damages databases with >150 years of records.From the several tested flood susceptibility models, the one that best fits the historical records was chosen, which corresponds also to a more valued role of flow accumulation factor. Results provide an accurate differentiation of transboundary, regional and local rivers. The scores of stream flood susceptibility were later transformed to a single value per each of the 278 municipalities of mainland Portugal. Representing the natural susceptibility to river flooding, these results can be cross-analyzed with structural mitigation measures, spatial planning instruments, exposure and vulnerability data along the respective floodplains, in order to identify water streams that require a more detailed and concerned future intervention and an exhaustive susceptibility study at the local scale.

An advanced analytical solution for pressure build-up during CO2 injection into infinite saline aquifers: The role of compressibility

Abstract Existing analytical or approximate solutions that are appropriate for describing the migration mechanics of CO2 and the evolution of fluid pressure in reservoirs do not consider the high compressibility of CO2, which reduces their calculation accuracy and application value. Therefore, this work first derives a new governing equation that represents the movement of complex fluids in reservoirs, based on the equation of continuity and the generalized Darcy's law. A more rigorous definition of the coefficient of compressibility of fluid is then presented, and a power function model (PFM) that characterizes the relationship between the physical properties of CO2 and the pressure is derived. Meanwhile, to avoid the difficulty of determining the saturation of fluids, a method that directly assumes the average relative permeability of each fluid phase in different fluid domains is proposed, based on the theory of gradual change. An advanced analytical solution is obtained that includes both the partial miscibility and the compressibility of CO2 and brine in evaluating the evolution of fluid pressure by integrating within different regions. Finally, two typical sample analyses are used to verify the reliability, improved nature and universality of this new analytical solution. Based on the physical characteristics and the results calculated for the examples, this work elaborates the concept and basis of partitioning for use in further work.

Performance Evaluation of Fe-Based Nanocrystalline Cores With High and Low Residual Flux

Fe-based nanocrystalline (FE-N) cores are widely used in pulsed-power and power electronic systems. In this paper, FE-N cores with high and low residual flux were tested and compared under single impulses. The loss density and permeability of the two FE-N types are evaluated in the usable flux swing range of ~0.0-1.4 T, and a range of magnetization rates of ~1.0 μs-6.0 T/μs. When the loss density and average relative permeability are evaluated for magnetization from initial point to positive saturation based on the initial magnetization curves, the FE-N with low residual flux has lower loss density and larger average relative permeability than the one with high residual flux under low magnetization rates. The loss density and average relative permeability of the two FE-N types are almost the same values under high magnetization rates. The application of the measured results in magnetic switch design and performance analysis is presented. The presented results of the two FE-N cores can be aided in the practical magnetic designs of magnetic switches, pulse transformers, and inductors, but not restricted to those.

Study on a Magnetic Switch for Pulsed Power Conditioning System

In order to protect the key elements (e.g., Xe flashlamps) from being damaged by the trigger impulse in pulsed power conditioning system (PPCS), a magnetic switch is used for isolating the high-voltage nanosecond impulse. The magnetic switch in PPCS is working along with the initial magnetization curve. The working principle and performance of the magnetic switch in PPCS is presented. Fe-based nanocrystalline is adopted as the material of magnetic core. According to the specific application, the dynamic characteristics of Fe-based nanocrystalline under nanosecond impulses were obtained experimentally. As the magnetization rate increases, the average relative permeability decreases due to magnetic viscosity and eddy current. The measured parameters of unsaturated inductance, saturated inductance, and saturation time are in agreement with the calculation ones. Finally, the experimental results of the magnetic switch in PPCS are presented.

Quantitative Prediction Model for the Water–Oil Relative Permeability Curve and Its Application in Reservoir Numerical Simulation. Part 1: Modeling

The water–oil relative permeability curve has a great effect on the rules of water cut increase and production variation. It is one of the most important data in reservoir development. With regard to a reservoir with a high degree of heterogeneity, the flow properties are various in different positions of the reservoir. Therefore, neither a single average relative permeability curve for the whole reservoir nor different curves for different sedimentary facies can precisely describe the reservoir flow characteristics, which will cause great difficulties for the remaining oil prediction and potential tapping. Therefore, it is of great importance to build a prediction model for the water–oil relative permeability curve, which can provide a calculation theory of the relative permeability curve for reservoir simulation using different relative permeability curves in different grid cells. The existing prediction models for the relative permeability curve have established the correlations between petrophysical p...

Directional Permeability Dependence in Electroplated Permalloy Layers

Flux guides made of soft magnetic thin-film material are an important component of micro actuators based on electromagnetic transducer principles. One essential property of soft magnetic films is the relative permeability µr. To achieve a low magnetic resistance (reluctance), a high relative permeability µr is required. While the permeability in patterned flux guides located in the wafer plane typically can be determined rather easily (it typically is similar to the permeability of non-patterned films) the permeability in patterns with a flux perpendicular to the wafer plane quite often is unknown. However, for the magnetic behavior of the whole thin-film core it is of utmost importance. Flux guides often feature a thickness of some ten micrometers, but lateral dimensions of hundreds of micrometers or even some millimeters and therefore are subject to demagnetization effects. Therefore, any permeability measurement on patterned magnetic films has to take the influence of the flux guide geometry into account. This paper describes an approach to determine the real average relative permeability µr along the main axes, i.e. parallel and perpendicular to the wafer surface, by using special multiple probes, subjecting the probes to a Vibrating Sample Magnetometer (VSM) test to determine the apparent relative permeability µr,app of a probe, and calculating the real relative permeability µr,real by taking the demagnetization factor into account.

Effect of pasture or wheat cropping on the permeability of a weakly weathered soil to sodic solutions

Abstract Laboratory estimates of permeability of soil from a rotation trial to solutions of varying sodium adsorption ratio (NaAR) and electrolyte concentration (EC) were made. Soil samples from under 2 years of wheat or 2 years of pasture, as well as a subsoil sample were used. At high EC (5 meq./litre), an increase in NaAR from 0 to 44 resulted in a 25% decrease in relative permeability but there was no significant difference between the soils at each NaAR. At low EC (≃ 0 meq./litre), an increase in NaAR resulted in an average relative permeability decrease of 70%. Significant differences occurred in permeability between wheat and pasture soils at NaAR of7.4 and 16.7. These results were related to the role of organic matter on structural stability at moderate Na002B; levels.