METHOD FOR MEASURING SELF-CALIBRATION ULTRASONIC WAVE OF BOREHOLF FLUID ACOUSTIC CHARACTERISTIC AT SITE

摘要

PROBLEM TO BE SOLVED: To provide a method and a tool for measuring a practical fluid characteristic by a downhole when a well is excavated. SOLUTION: Acoustic impedance of an excavation fluid (210) is found by using reflection from a metal disk (220), and density of the excavation fluid (210) is found on the basis thereof. Since reverberation characteristics of a sound wave depend on a sound wave form to some degree, first reflection (260) from the metal disk (220) is used for calibrating measurement. The method includes (1) generating an acoustic signal in a borehole fluid, (2) receiving reflection of the acoustic signal from the fluid, and (3) analyzing the reverberation parts (271-276) of the acoustic signal to determine the characteristics. The analysis of the reverberation part includes acquiring a logical reverberation signal and relating the reverberation signal measured for determining borehole fluid characteristic with the logical reverberation signal.