Klaus Cozzolino

A new look at multiphase invasion with applications to borehole resistivity interpretation

Abstract In well log interpretation, it is frequently necessary to correct logs for invasion. Invasion occurs in permeable formations when there is a radial differential pressure (RDP) between the borehole and formation. Other factors on which invasion depend include saturation, mobility, pressure (RDP) and capillary pressure, permeability and viscosity of fluids, and temperature transient effects associated with the mud filtrate injected into the formation. Thus, simulation of realistic invasion is not an easy task. This work reviews the famous Buckley–Leverett mathematical model in cylindrical coordinates appropriate for borehole geometries. The model predicts multiphase invasion in porous media when gravity, capillary pressure, and mud cake can be neglected. One application is to correct logging while drilling (LWD) and wireline resistivity logs for time-dependent invasion and formation temperature effects. This is important, for example, when there are possible large differences in formation and mud temperature. Modeling studies show these effects can be large enough to noticeably influence resistivity logs. However, after correction, difference in LWD and wireline logs arising from the time-dependent heat process are explained. Thus, the method, when coupled to a time-dependent heat flow model, and a response function formulation of resistivity, yields new insight into the influence of thermal and electrical transients in log interpretation.

Level analysis of a digital TV signal using the tool moving average

With the implantation of digital TV system in Brazil since from 2007, several research groups have been created to study the performance of digital TV signal in several areas in the country. This study, in the north region, due their peculiarities (forests, rivers, buildings, etc..), is a very relevant component. In this work a study was carried the signal level with distance using a statistical method, moving average, and the Pearsons correlation factor. The results compared with the experimental results showed good agreement. The average error was 3.88 dB and standard deviation 3.90 dB.

Application of Parabolic Equation and Hata-Davidson propagation models for digital TV coverage prediction

In this paper the formalism of Parabolic Equations for narrow angles, a statistical method, the Moving Average and a empirical model, the Hata-Davidson, were used for to study on the quality of digital TV signal in the UHF band, and were compared with the measured in an heterogeneous environment, because it has areas with large buildings mixed with Amazonian vegetation. The implicit finite difference scheme of the Crank-Nicolson type was applied in order to get the solution of the Parabolic Equation. The propagation was considered in 15° in the direction paraxial. The results showed that the formalism of Parabolic Equations can be used to study the quality of digital TV signal. The average error was 1.62 dB and standard deviation 4.13 dB.

Propagation path loss in mixed-path environment using narrow angle and wide-angle Parabolic equations

A model to predict the propagation path loss through the urban foliated semi-confined environment using parabolic equations (PE) is proposed. For this case the propagation in 15° to the paraxial direction and the implicit finite differences scheme of the Crank-Nicolson type is used. To wide-angle relative to the paraxial direction propagation (up to 90°), it used mixed Fourier transform and considers the impedance boundary conditions. A campaign of measurements taken in three mixed-path environment was carried out to validate the model. The frequency used was 900 MHz to Benfica and Marituba, and 1.8 GHz for Barcarena. Numerical examples demonstrate the computational efficiency of the proposed method.

A model for radio propagation loss prediction in buildings using wide-angle parabolic equations

This paper propose a model to calculate the path loss propagation in an indoor environment using parabolic equations. To solve the parabolic equation a mixed Fourier transform was used. The impedance boundary conditions, wide-angle relative to paraxial direction of propagation and complex refractive index for the medium were considered. A campaign of measurements was carried out in two environments in 900 MHz and 2.4 GHz frequencies. Simulations with the proposed model showed good agreement with the experimental data and with model of UWB Propagation Channels.