The detecting characteristics of resistivity log tool through casing
过套管电阻率测井仪器的径向探测特性

In order to study the radial detecting characteristics of resistivity log tool through casing,this paper gives the geometric factor which can image the radial change of stratal medium.The geometric factor of resistivity log tool has been calculated by the transmission line equation for resistivity logging through casing.Aimed at the CHFR tool of Schlumberger Corporation and the зKOC-31-7 tool of Russia we have given the response curves of the geometric factor,and found that two kinds of tools all have large radial detecting radius for the low invasion profile(invasion of low resistance fluid),but the radial detecting radii of tools decrease with the increase of invasion fluid resistance(high invasion profile).This research provides the theoretic foundation for the logging interpretation and the analysis of radial detecting characteristics of tools.