Numerical simulation and correction of electric logging under the condition of oil-based mud invasion

Abstract

When high-resistivity oil-based mud infiltrates a permeable formation, the resistivity obtained from logging measurements will increase over time, which affects the accuracy of logging interpretation. The invasion of oil-based mud is affected mainly by the formation's physical properties, pressure difference and invasion time. To improve accuracy of interpretation, it is necessary to correct the resistivity of the formation. In this article, we analyzed the effects of formation physical properties, pressure difference on oil-based mud invasion by a numerical simulation method. And then we simulated the radial distribution of formation resistivity when the oil-based mud invaded the water layer, gas–water layer, and gas layer. Finally, by inverting the true resistivity of the formation, we developed a resistivity correction chart to correct the formation resistivity.