NUMERICAL ANALYSIS OF MICRO-ANISOTROPY OF ELECTRICAL RESISTIVITY IN SEDIMENTARY ROCK SAMPLES DURING CLAY-BASED DRILLING FLUID FILTRATION
M.I. Epov1, S.I. Markov1,2, E.I. Shtanko1, D.V. Dobrolyubova1,2
1Trofimuk Institute of Petroleum-Gas Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
2Novosibirsk State Technical University, Novosibirsk, Russia
Keywords: Electrical conductivity, anisotropy, digital core, numerical simulation
Abstract
When drilling wells, drilling fluid, which contains solid dispersed phase, penetrates into the surrounding rocks. Depending on the size ratio of clay particles (cuttings) and pores, a zone of colmatization can form, which leads to significant changes in the transport and electrical characteristics of the downhole space. The latter are especially important for reliable interpretation of logging data, since a directional change in the pore space structure can cause anisotropy of physical properties of the rock. The process of colmatization is irreversible and almost irreproducible in laboratory conditions. Its study is based on numerical experiments aimed at analyzing physical characteristics of digital analogues of sedimentary rock samples (sandstones). The paper focuses on calculating effective specific conductivity tensor of sedimentary rock samples at different volume saturation of the pore space with clay-based drilling mud, formation water and oil. We demonstrate the effect of the volume content of these phases on the anisotropy in specific electrical conductivity using digital analogues of two sandstone samples constructed based on nondestructive visualization of their internal structure.
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