Method and Sensor Design of Resistivity and Dielectric Constant Measurement for Oil-based Drilling Fluid in the Downhole Environment
Oil-based drilling liquid is applied to an increasingly wide extent in the oil drilling,and borehole electrical imaging tools suitable for oil-base drilling liquid are also widely applied.Resistivity and dielectric constant of the drilling liquid are key factors that affect the meas-uring of the borehole electrical imaging tools,so it is needed to compensate the measured imaging data.A method is introduced to measure resistivity and dielectric constant of the oil-based drilling liquid in the down-hole in real time,and the sensor is designed based on the meth-od.A coaxial cylindrical capacitor consisting of an emission electrode,a receiving electrode and the oil-based drilling liquid in the annular between the two electrodes is developed,through which the quantitative relation between dielectric constant of the oil-based drilling liquid and capacitance of the capacitor,as well as that between resistivity of the oil-based drilling liquid and equivalent resistance of the capacitor is derived,so the resistivity and dielectric constant can be defined.This technology provides theoretical basis and technological support for compensating the influence of the oil-based drilling liquid on the measurement of the electrical imaging tools.
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