Heterogeneity to some extent is realized in every reservoir. Variable properties, namely fluid saturations and lithology, make it very difficult to accurately estimate the bulk dielectric response of the reservoir. This study isolates and identifies the dependencies of the bulk dielectric response to changing water content, quartz content, limestone content, oil content, and clay content.
A multitude of experiments were run where the identified parameters were systematically isolated and varied to capture both the contribution from the rock matrix and the pore space. Reservoir rock was simulated by mixing the rock matrix components with the fluids to form unconsolidated core samples. The bulk dielectric properties, both the real and imaginary components, were measured for each of the seventy five different samples using a vector network analyzer (VNA) in conjunction with a dielectric probe. Individual experiments were analyzed comparatively and the dielectric responses are presented as a function of each isolated parameter.
Understanding the general dependencies and sensitivity of the dielectric behavior of the reservoir is vital for various aspects of petroleum including electromagnetic heating and well logging. The complex and dynamic downhole environment creates coupled and mutual interactions making estimation of the bulk response very difficult. Isolation of each variable allows for the identification of the governing relationship of each parameter with the dielectric response. In this study, linearity is established for the dielectric response of all investigated parameters. The sensitivity of the complex permittivity is represented as the magnitude of change as a function of variable fluid saturation or lithology. This enables the drivers of dielectric heating to be quantified, namely the increase in complex permittivity with increasing water saturation. The established relationships allow for the estimation of the dielectric response of the reservoir as a result of heterogeneity present. Variable properties that change with position and time are accounted for by understanding the corresponding change in the complex permittivity of the reservoir.
By illuminating the complex permittivity relationship as a function of rock minerology and fluid saturations, a more holistic understanding of absorption mechanics can be achieved. The study offers the unique ability to express the intrinsic relationship experienced under the influence of reservoir properties. The presented relationships also enable the estimation of dielectric properties as a function of reservoir heterogeneity.