Revisiting Dielectric Logging in Saudi Arabia: Recent Experiences and Applications in Development and Exploration Wells
- Denis P. Schmitt (Saudi Aramco) | Ahmed Al-Harbi (Saudi Aramco) | Pablo Saldungaray (Schlumberger) | Ridvan Akkurt (Schlumberger) | Tianhua Zhang (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE/DGS Saudi Arabia Section Technical Symposium and Exhibition, 15-18 May, Al-Khobar, Saudi Arabia
- Publication Date
- Document Type
- Conference Paper
- 2011. Society of Petroleum Engineers
- 1.6.9 Coring, Fishing, 1.6 Drilling Operations, 5.6.1 Open hole/cased hole log analysis, 4.2 Pipelines, Flowlines and Risers, 5.2.1 Phase Behavior and PVT Measurements, 4.3.4 Scale, 4.1.2 Separation and Treating, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 4.1.5 Processing Equipment, 1.10 Drilling Equipment, 5.3.4 Reduction of Residual Oil Saturation, 1.11 Drilling Fluids and Materials, 5.1 Reservoir Characterisation, 1.2.3 Rock properties, 5.8.5 Oil Sand, Oil Shale, Bitumen, 5.5.11 Formation Testing (e.g., Wireline, LWD), 5.8.7 Carbonate Reservoir, 5.2 Reservoir Fluid Dynamics
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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.
Electromagnetic wave propagation in a porous medium is controlled by its conductivity and dielectric permittivity. The water has a large dielectric permittivity, much higher than other fluids or minerals found in reservoir rocks. This contrast makes the dielectric measurements particularly sensitive to the water filling the porous space. One of the natural applications of dielectric logging is therefore 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).
Dielectric logging tools were first introduced in the late 1970s (e.g., Calvert et al., 1977). Although the technology generated a lot of interest upon its introduction (including in Saudi Aramco, e.g. Freeman and Henry, 1983), it gradually disappeared over the years, mostly due to moderate accuracy of the early devices, sensitivity to borehole rugosity, oversimplified interpretation models (especially in carbonates), and other hardware related complications.
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