Calculated Formation Resistivity for Electrical Imaging Logging in Oil-Based Mud Using Dual-Frequency Measurement: Formulation and Simple Verification

Abstract

AbstractDifferent from electrical imaging logging in water-based mud, electrical imaging logging in oil-based mud has encountered many challenges. However, a wide variety of circumstances can’t still leave oil based mud, such as deep-water reservoirs, high temperature and high pressure reservoirs, and shale reservoirs, which resulting in the recurrent replacement of electrical imaging logging in water-based mud by electrical imaging logging in oil-based mud. The toughest difficulty for electoral imaging logging in oil-based mud is the limit from the high resistance characteristic of oil-based mud on the clear formation resistivity imaging. Here, a dual frequency measurement method is introduced systematically for electrical imaging logging in oil-based mud. First, an equivalent circuit model is established based on the working principle and the principle of capacitance coupling introduced firstly. Then, a mathematical model based on the equivalent circuit model is formulized out and the parameter that can describe the change of formation resistivity is separated from the part of high-resistance oil-based mud. Finally, a numerical simulation model is established using finite element method to verified the validity of dual frequency measurement method by means of different models. The results show that the effective signal segregation between the oil-based mud and formation is realized and the formation resistivity can be described quite perfectly. This research is beneficial to the development of electrical imaging logging technology in oil-based mud.KeywordsElectrical imaging loggingOil-based mudDual frequency measurementCapacitance coupling