Dielectric Dispersion: A New Wireline Petrophysical Measurement

Abstract

Dielectric measurements and interpretation, introduced with great promise in the 1980s, have not found widespread use owing to measurement limitations, moderate accuracy, and insufficient quality control. This paper presents a new-generation dielectric tool that overcomes these limitations and brings extra information for more accurate petrophysical formation-evaluation. One of the revolutionary advances offered by this tool is the continuous measurement of dielectric dispersion (variation of formation dielectric properties as a function of the frequency) at 1-in vertical resolution. The tool uses multi-spacings antenna arrays operating at multiple frequencies in the MHz to GHz range. Moreover, transmitter and receiver antennas have colocated longitudinal and transverse polarizations. The wealth of recorded data will allow interpreters to both adapt the answer product to the reservoir fluids and geology, and also to provide acquisition quality-controls and error estimates on the results. Carbonate and heavy oil reservoirs are becoming more and more important. In these two environments, the new tool provides unique answers to better characterize these reservoirs. This tool also addresses traditional dielectric formation-evaluation in fresh water and thinly laminated sands. Answer products offered by this new tool can be classified in three categories.Pore-fluid analysis from the muti-spacings high frequency measurementsHydrocarbon residual saturation and invaded zone water salinityInvasion profile: hydrocarbon saturation profile in heavy oil reservoirMatrix analysis from dielectric dispersionCarbonates: textural information (Archie m cementation factor)Shaly sands: high resolution clay volume and anisotropyGeological structure analysis from the muti-polarizations and high resolutionThin beds analysisStructural anisotropy measurement in very thin bedsGeological features extractionCarbonate classification This paper reviews the dielectric dispersion physics, then describes the tool's architecture, measurements, and data processing chain. Field test examples illustrate the enhanced interpretation potential of dielectric dispersion measurements from this tool. Introduction to dielectric dispersion physics The permittivity quantifies the sensitivity of a medium to an electric field excitation. Three main physical phenomena contribute to the permittivity: the displacement of the electronic cloud of atoms, the coherent orientation on pre-existing microscopic electric dipoles and the polarization effect at the interfaces. These phenomena are illustrated in Figure 1.

Reservoir monitoring using borehole radars to improve oil recovery: Suggestions from 3D electromagnetic and fluid modeling

“…In addition, an indirect but cheap approach for formation permittivity acquirement is to use a socalled dielectric dispersion logging tool. This kind of wireline EM logging uses multispacing, multifrequency, and cross-polarization antenna arrays to measure attenuation and phase shift of EM wave in different radial depths (Hizem et al, 2008). Successful field tests have been reported that the tool can simultaneously inverse the permittivity and conductivity of the virgin formation (Mosse et al, 2009).…”

Experimental Characterization of Dielectric Properties in Fluid Saturated Artificial Shales

“…However, dielectric logging at frequencies of 1 GHz and above remains challenging in field measurements due to decreased depth of electric field penetration. On the contrary, currently available commercial dielectric tools operate at multiple spot frequencies [5] to facilitate a determination of water content and CEC: dielectric response at frequencies below 50 MHz is more affected by the surface effects described above [6]. At lower frequencies, clay content, geometry and spatial orientations of mineral rock constituents, and the salinity of pore fluid also affect the measured dielectric permittivity [7,8].…”

A dielectric logging tool with insulated collar for formation fluid detection around borehole

“…The dielectric scanner was developed to quantify complex permittivity at different frequencies (Hizem et al, 2008). Transmitters and receivers are mounted on a pad in contact with the borehole and raw measurement of attenuation and phase shift are obtained at four frequency points between 20 MHz to 1 GHz.…”