SU798671A1 - Electromagnetic well logging method - Google Patents

Description

(54) METHOD OF ELECTROMAGNETIC WAGGING WELLS FIG. 1 shows the measuring PROBE} in FIG. 2 is the calculated dependence on the resistivity of the wellbore relative to the measurement error p in the presence of a well cavity. The measuring probe contains a receiver 1 of an electromagnetic field, an emitter 2 of this floor, located between receiver 1 and receiver 3, an emitter 4, remote from the receivers in one direction (r and T | are the radii of the well and cavity). If we accept the propagation paths of electromagnetic waves, from the emitters to the receivers, such as they are schematically shown by arrows in FIG. 1, the proposed method is described as follows. Emitters 1 and 2 excite waves of electromagnetic fields in the borehole and its surrounding rocks, which in each part of the path from the emitters to the receivers receive a phase shift V, which all the way from the radiator 4 to receivers 1 and 3 is equal to: H-CH 4- Ф 4-and 4-and Ч-1-ЧАЬ ЧЬс Check Vm,% -Э 4 4 cd Phase shift on the way from emit l 2 to receivers 1 and 3: Cha-. The phase difference in the receiving emitter 4 and measured by the method is: At the nominal diameter. The presence of a cavity introduces a phase shift, the values are: 44cd-U1.m From this it follows:, The value of d M. registering a known method. The phase difference in the receiver 2 is: a 1lEc "lcd- iefe- 2km at the nominal diameter of the well lcd ikrn V c -lzeic, If the radiator 2 is in the same between the receivers, then: Vo-. The presence of a well cavern introduces an additional phase shift in the peak of the radiator 2 floor: Vd-ikm-- a. At the same time, the difference measured by the proposed difference is: f., - A, 4. If the measurements are made without the important influence of the diameter of the borehole: LP, 0, and QH If the frequency of the emitters is equal or insignificant or not significant, the difference is Consequently, the difference between the LFV – DF is less susceptible to the influence of the electrical parameters of the well of a variable-diameter well. For clarification, Fig. 2 shows the calculated dependence of the relative measurement error on the resistivity of the well solution in the presence of a well cavity g 0.15 m at Tg 0.1 m and §, 80. Parameters of the rock surrounding the well are p 20 ohm; g 20. Curve 1. A, curve The probe contains two receiving coils spaced 0.4 m apart, the generating coil (radiating) coil in the middle between receiving coils, and generating, remote from receiving coils by 0.6 m. The frequency of the electromagnetic field is f 4 3 MHz Under these conditions, the measurement error is suggested using the method-i is much lower than the measurement error known.

Claims (3)

1. Chernov to G. Ya. And M skovskiy about. M. Radio Wave Research in hydrogeology and engineering geology, M., Nedra, 1973, p. 116, 120. 2. Antonov D. N. and Kaufman A. A. 0 Dielectric inductive logging. Novosibirsk, Science, 1971, p. 6-15. 3.-USSR author's certificate  206735, cl. G 01 V 3/18, 1953 (prototype). fl, 7i 2468 Fkg7