SU1343004A1 - Device for measuring untwisting of geophysical cable in well - Google Patents

Abstract

This invention relates to a well logging technique. The purpose of the invention is to improve the accuracy of measuring cable unwinding by providing a fixed reference system of cable rotation angle. The device includes a housing 1 rigidly connected to the cable. Inside the housing there is a reference unit, made in the form of a freely rotating eccentric frame with a permanent magnet 3. A housing I is rigidly connected and interacts with the reference node a group of contacts in the form of reed switches 6. The housing 1 is rigidly connected to the cable head 7, so it can be rotated relative to the magnet 3. When one of the reed switches 6 is in the zone of the magnet 3, its contacts are closed and on the surface there will be a signal that the cable starts to turn. Upon further twisting of the cable, the next reed switch closes 6. The presence of two signals indicates the rotation of the cable by a certain angle determined by the distance between the two reed switches 6. 2 I.P. § (Л to со 4 :: 00 о о J V

Description

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The invention relates to a technique of well logging and is intended to determine the unwinding of a geophysical cable in determining its length.

The purpose of the invention is to improve the accuracy of measuring cable unwinding by providing a fixed reference angle of the cable.

Figure 1 shows the device, a general view; figure 2 is the same cross section.

The device includes a housing 1 and a cover 2 connected to the housing with a thread. Inside the housing there is a rotation reference unit, made in the form of a freely rotating eccentric frame (not shown) with a permanent magnet 3. The free rotation of the frame relative to the housing 1 is provided by mounting its rest 4 in the bearings 5. On the outer surface of the housing 1 there are longitudinal grooves a, b which a group of contacts, made in the form of reed switches 6, are rigidly fixed. To register the closure of reed switches 6 under the action of a permanent magnet 3, a two-wire power supply circuit (not shown) is used. The installation site of the device can be a cable head 7, rigidly connected to the geophysical cable 8. The device is fixed in the cable head 7 by a nut 9. In this case, one of the supply cores is the device case 1, electrically connected through the cable head to the armor. cable 8 and the other conductor is one of the conductive wires 10 of the cable. The remaining wires of the cable are passed through the holes 6 of the axles 4, are dispersed onto the plug connector I1 and are used to power the circuit of the downhole tool (not shown). The connector 11 is fixed in the pump with a nut 12.

We consider the device operation by the example of studying an inclined well, since it is in an inclined well due to the effect of additional tensile forces caused by the friction of the cable and the device on the borehole walls, an additional opening of the cable occurs, leading to a change in its length.

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Being in a well, eccentric on a frame with a permanent magnet 3 occupies a stable position in the plane of curvature of the well. The effect of tension on the cable 8 due to the imbalance of the armor is unwound (or twisted B, depending on whether the device is lowered or raised, associated with an increase or decrease in the weight of the cable lowered into the well). Because of the cable head 7. the device case 1 is rigidly connected to the head, then it will rotate relative to the eccentrically located magnet 3. At that moment, when one of the reed switches 6 is at the lower point (see Fig. 2), i.e. in the area of the field of the magnet 3, its contacts are closed and on the surface a signal is transmitted in the form of a current pulse when the cable starts to turn. With further unwinding of the cable due to rotation of the housing 1, the contacts of the next reed switch, which occupies the lower position, close. The filing of two signals indicates the rotation of the cable at a certain angle determined by the angular distance between two adjacent reed switches. Since the cable is unwound (lengthening) when the cable is lowered, and twisting during lifting, it is sufficient to count on the surface the number of pulses during lifting (or lowering) that uniquely determine the intensity of cable rotation in the well.

Thus, the accuracy of the rotation of the cable in the well is increased, achieved by creating an independent in the space of the reference system 45 of the angle of rotation of the cable, the function of which is performed by an eccentric frame with a permanent magnet freely rotating relative to the housing 3.

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Claims (1)

Invention Formula A device for measuring the unwinding of a geophysical cable in a well, comprising a housing rigidly connected to the cable, a turning reference unit located in the housing, and a group of contacts rigidly connected to the housing and interacting with the reference node, distinguishing 1343004 In order to increase the reference point made in the form of freedom to measure the unwinding of the cable-rotating eccentric frame with the provision of a fixed permanent magnet, and the cortex group of the reference system of the angle of rotation of the cable, in the form of reed switches. Figg