Revisiting Dielectric Logging in Saudi Arabia: Recent Experiences and Applications in Development and Exploration Wells

Abstract

Dielectric logging was introduced in late 70s to mostly measure water filled porosity in the flushed zone independent of water salinity and Archie exponents m and n. Although the technology generated a lot of interest upon its introduction, it eventually disappeared over the years, mostly due to moderate accuracy of the early devices, oversimplified interpretation models and other hardware related complications. Results from extensive field testing of a new generation of dielectric wireline tools indicate that robust and reliable dielectric logging is now feasible in a wide range of environmental conditions and formations. Benchmarking of dielectric measurements against other logs and core data has shown that water-filled porosity can be measured accurately using dielectric logging tools, provided the matrix mineralogy is well defined. Consequently, the technology has gained rapid acceptance in applications involving flushed zone water saturation in environments with variable or unknown salinity, heavy oil identification, and discrimination of non-reservoir rock with high organic content. Dielectric logging is gradually replacing NMR Log-Inject-Log for residual/remaining oil saturation (ROS) measurement, especially in the situations where connate and injected water salinities can be vastly different. Due to the success in ROS applications, most of the recent testing has been focused towards carbonates drilled with water-based-mud. This technology is also being tested in shaly sands and in wells drilled with oil based mud at present. Additional work is underway to accurately characterize dielectric properties of carbonates so as to be able to perform quantitative textural analysis. In shaly sands, high resolution clay volumes and thin bed analysis are challenges that will be addressed in the future.

Integration of Dielectric Dispersion and 3D NMR Characterizes the Texture and Wettability of a Cretaceous Carbonate Reservoir

“…In recent years, multifrequency dielectric logs have been shown to provide a very accurate saturation in the invaded zone (Hizem et al 2008;Schmitt et al 2011;El Din et al 2011). Clean carbonate rocks exhibit characteristic frequency dielectric dispersion patterns which depend on their texture and wettability.…”

A Workflow to Evaluate Mineralogy, Porosity, TOC, and Hydrocarbon Volume in the Eagle Ford Shale

“…All five antennas and related electronics are mounted in an articulated pad that is extended toward the formation. The upper boundary for the real dielectric constant for kerogen, 3.3, is from Seleznev et al (2011), and the values for clay, 5-6, are from Schmitt et al (2011). The configuration of the antennas compensates for tool standoff, mud cake effects, and borehole rugosity.…”

“…The electronic and signal processing provide formation dielectric constant and formation conductivity logs, which can be used to calculate the bulk volume of water in the flushed zone. The high value of the real dielectric constant of water makes the measurements particularly sensitive to water filling the porous space; consequently, one of the natural applications of dielectric logging is the measurement of water-filled porosity in the near-wellbore region, with little or no dependence on the water salinity and Archie electric parameters, m and n (Schmitt et al 2011). An electromagnetic wave propagating through a material will be attenuated and experience a phase shift.…”

“…The configuration of the antennas compensates for tool standoff, mud cake effects, and borehole rugosity. The key equations are clearly documented in Bittar et al (2010) or Schmitt et al (2011). Both of these can be measured (Bittar et al 2010) and converted (by using a look up table) to the formation resistivity, R, and dielectric constant of the material, ε'.…”

“…The imaginary dielectric constant, ε'', can be derived from the formation resistivity, R. Table 1 provides the real and imaginary dielectric constants for several materials encountered in formation evaluation. Alternatively, salinity can be obtained from inverting the CRIM equations and then making a second interpretation with the salinity constrained around this value (Schmitt et al 2011). The high value of the real dielectric constant of water makes the measurements particularly sensitive to water filling the porous space; consequently, one of the natural applications of dielectric logging is the measurement of water-filled porosity in the near-wellbore region, with little or no dependence on the water salinity and Archie electric parameters, m and n (Schmitt et al 2011).…”