Technical Paper: Dielectric Dispersion Measurements in California Heavy Oil Reservoirs

Society: SPWLA
Paper Number: 2010fe
Presentation Date: 2010


Dielectric measurements have been used over the past thirty years in a variety of reservoirs to determine flushed zone water-filled porosity in formations with fresh or unknown water salinity. This measurement is particularly useful in heavy oil reservoirs because little invasion occurs, making oil saturations of the uninvaded and invaded zones approximately equal. A new dielectric measurement provides dielectric permittivity and conductivity at multiple depths of investigation as a result of multiple frequencies, receiver spacings, and polarizations.

This next-generation dielectric measurement is collected over a large range of operating frequencies using an array of antennas with two separate orientations. A total of nine measurements of attenuation and phase shift are made at four different frequencies, allowing for a true measure of dielectric dispersion. Inversion of these measurements computes a simple water-filled porosity, as was done with older generation dielectric tools based on a single permittivity measurement. By measuring permittivity and conductivity at different frequencies, antenna spacings, and orientations it is possible to construct a water-filled porosity invasion profile.

Inverting all the measurements makes it possible to solve for salinity, invasion depth, and other environmental parameters that led to unpredictable results with previous-generation single-frequency tools. Further processing will make it possible to solve for textural parameters such as saturation and cementation exponents or cation exchange capacity.

Formation evaluation in the oil fields of California has always been challenging. Probably the biggest challenge faced by log analysts years ago was the difficulty of distinguishing oil from fresh formation water. This was further complicated by the inability to distinguish producible oil from oil that was not movable. Recovery factors were often 20% or less, which led to many attempts at enhanced oil recovery, of which steam floods have proved to be the most successful. This paper discusses the application of this new dielectric dispersion measurement in mature heavy oil reservoirs and features examples from California.

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