Fluid salinity, clay content, and permeability of rocks determined through complex resistivity partition fraction decomposition

Abstract

The types of physical mechanisms that generate induced electric polarization (IP) in rocks are here identified and their respective relaxation times are provided. Thus, the complex resistivity function associated with Dias’ model that describes the IP phenomenon is decomposed into partition fractions of an inverse third-degree polynomial in [Formula: see text]. Twelve rock samples’ data from the literature were used for this investigation. Using this procedure, two basic relaxations appear in the frequency range 1 mHz–1 MHz, where the phenomenon occurs. The first relaxation is associated with polarization caused by ionic diffusion proximal to the disseminated particle-electrolytic solution interfaces, which dominates in the low-frequency interval (approximately 1 mHz–100 Hz). The second process is capacitive-inductive polarization relaxation caused by an interaction between the electric double-layer capacitance and polarization-free pore resistances inside the polarization unit cell, which dominates in the high-frequency interval (approximately 10 kHz–1 MHz). At intermediate frequencies, these two processes combine to yield a transitional type of relaxation that dominates in the intermediate frequency interval (approximately 100 Hz–10 kHz). Our results, obtained using a given set of experimental data, provide a new method for determining the water salinity and clay content in the rock matrix without metallic particles. The rock permeability was also well determined by introducing Dias’ model parameter relationships and substituting the double-layer thickness for the grain size radius in a previously proposed formula.

Determinação de parâmetros de reservatório através do efeito de polarização induzida observado em medidas elétricas espectrais de laboratório

“…A polarização elétrica induzida (ou efeito IP) corresponde a um fenômeno de polarização de interface nas rochas, sendo a polarização por partículas de argilominerais disseminadas nos poros dessas rochas (polarização de membrana) a mais frequente em reservatórios de hidrocarbonetos. Com isso, é crescente o interesse da indústria de exploração e produção de petróleo em pesquisas que correlacionem as informações obtidas do efeito de IP com propriedades de rochas de reservatório, visando auxiliar na caracterização de zonas produtoras (Dias, 2000;Tong et al, 2006;Revil & Florsch, 2010;Revil et al, 2012;Barreto & Dias, 2014).…”

“…Em Barreto & Dias (2014), foi apresentado um esclarecimento significativo sobre os máximos de fase do espectro de resistividade elétrica. Neste trabalho, houve a demonstração de que o primeiro máximo de fase, às frequências mais baixas, está relacionado ao processo de difusão de cátions em solução, próximo à interface argilomineral-eletrólito dentro de uma estrutura elétrica denominada dupla camada elétrica de Helmholtz.…”

Development of a new equivalent circuit model for spectral induced polarization data analysis of ore samples

“…In order to evaluate the suitability of the models, the relaxation characteristics between compact layer and diffuse layer were evaluated. Compact layer relaxation is known to be induced at frequencies higher 1 MHz, while the diffuse layer can be relaxed at low frequencies below 100 Hz (Barreto and Dias 2014). In addition, in the EDL model suggested by Bockris et al (1963), the compact layer is thinner than diffuse layer (Fig.…”

“…3c, CPE1 represents the compact layer response, while CPE2 corresponds to the diffuse layer response. CPE1 should be ignored when calculating SIP parameters such as chargeability and relaxation time because the compact layer is influenced by the response at higher frequencies (10 kHz-1 MHz) (Barreto and Dias 2014), which are outside the frequency band. By ignoring CPE1 in the model, the chargeability suggested by Pelton et al (1978) can be calculated by Eq.…”

Multi‐frequency electromagnetic method for inductive measurement of ground induced polarization and resistivity

“…This fact is particularly relevant because the presence of IP always generates positive values for , and the value can be greater than 0.13 for many laboratory measurements. For example, the samples in Barreto and Dias () have positive of 10 −4 to 0.78 (for phase 0.1–900 mrad). Consequently, based on the two‐layer modelling, we can conclude that (a) notably strong positive values of always imply the presence of the IP effect in the surveyed terrain.…”