SU441543A1 - Micro-logging device - Google Patents

Description

one

 The invention relates to devices for geophysical surveys of wells, in particular for electrical well logging.

A device for micro-logging of wells is known, which contains an insulating shoe with concentrically located central needle, measuring and screen electrodes, a generator circuit and a metering circuit with self-compensation. Various modifications of such devices are used in the micro-logging of the near zone or in measuring the resistance of the flushed zone in the case of a small depth of penetration of the drilling fluid into the formations.

The purpose of the invention is to provide the possibility of simultaneous measurement of the parameters of the penetration zone at two radii of investigation.

The goal is achieved by the fact that in the proposed device the screen electrode is made of two insulated on a shoe, concentrically arranged parts that are interconnected via resistance and connected to the input of the measuring circuit.

The drawing schematically shows the proposed device in two projections (according to the principle of operation, similar to the two-electrode side logging microprobe /).

The proposed device contains a measuring shoe I, pressed against the borehole wall using a clamping device, and remote electrodes 2 - and 3. On the front surface of the shoe are a central rectangular electrode 4, electrode 5 and two shield Hfcjx electrodes 6 and 7 interconnected through each other. low resistance R. The electrodes cover the entire front surface of the shoe and are separated from each other only by small insulating gaps. A clamping device can be used as an electrode 2, and the electrode 3 serves as a bronzer Electrodes o and 7 form a microinstallation of the near-field logging with a screen electrode consisting of two parts. A conventional circuit is used to work with this IV equipment: the central electrode 4 is powered by the generator 8 with a stabilized current J0v and a current Uz is passed through the screen electrode from the compensator 9s auto-compensator by varying the current to zero (with an acceptable error; the voltage between the electrodes 4 and 5. The measured value proportional to the apparent resistance is the potential of electrode 5. The field of the second microinstallation is created by the same electrodes as the first one, but only electrodes 6 and Due to the fact that the potentials of these electrodes are almost equal to each other (R is very small) and to the potential of electrode 4, the current distribution in the medium from these I electrodes is about the same as from the edge region of a solid electrode occupying the entire surface of the shoe. electrode 6 and the transition from it to the apparent resistance, get almost the same result as with a three-electrode equal potential probe, the screen electrodes of which are electrodes 4 and 7, and the main electrode is a frame electr o 6, The resulting installation is similar in its properties to a two-electrode probe of the side microkartage with a small area of the screen electrode. 1 {the actual resistance for the second microlobe is l // and ,, U – R / y – K –– K and –– the potential of the electrode 7; Y - current through the electrode., 6; The potential potential difference across the resistance R I is the coefficient of the compactness. The combined microprobe can be made in the form of a rectangular or diamond-shaped shoe with round, oval, or rectangular electrodes. The size of the ashmak is chosen based on the irreducible radius of the study: irina is somewhat smaller, and length 2-2.5 times the required size. The dimensions of the electrodes 4 and 6 are chosen so as to ensure the greatest depth of investigation with the first installation and 2 to 3 times smaller - the second. This condition is satisfied if the area of the electrode 4 is 20-30 times smaller, and cyiwm of the areas of the electrodes 4.5 and 6 is S-3 times smaller than the area of the whole shoe. In wells 200-3001 in diameter, a rectangular shoe having dimensions of 240 x 120 mm and a surface curvature of 100 ivnvi can be used, on the front side of which there is a rectangular electrode 4 with a size of 120x40 bar and three frame electrodes 5.6 and 7 beams IO-I5MM . At these sizes, the micro-installation of the side microkartage has approximately a half of the radius of the study and a greater sensitivity to the mudcake than: micro extraction of the near-field logging. According to the results of measurements by both mainframes, permeable rocks are distinguished in the well section (according to the difference in readings of the first and second microinstallations) and the specific resistance of the washed out zone of rocks is determined with high accuracy. The complex instrumentation for measuring the microprobe discussed above (together with the microcorner meter) can be built on the basis of telemetric measurement systems used in logging equipment for single-core or multi-conductor cables, which have four measuring channels and contain blocks for dividing one signal by another. In particular, for this purpose, the frequency-modulated telemetric system of complex heat-resistant ABCT equipment for electrical and side logging can be used. SUMMARY OF THE INVENTION A device for the micro-logging of wells (.containing an isolation shoe with concentric central, measuring and screen electrodes, generator

a circuit and a metering circuit with an autocompensator, characterized in that, in order to simultaneously change the parameters of the penetration zone at two radii of investigation, the screen

the electrode is made of two isolated on a shoe concentrically arranged parts, which are connected between themselves through resistance and connected to the input of the measuring circuit.

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