DEVICE FOR MEASURING SPECIFIC ELECTRICAL RESISTIVITY OF ROCKS

Claims

1. A device for measuring the specific electrical resistance of rocks, comprising an elongated conductive housing, first and second generating toroidal coils, a measuring electrode electrically insulated from the housing, a means for measuring the electrode current, an electronic unit, the generating coils are located respectively in the first and second positions on the housing at a base distance from each other, the electrode is located between the first and second generating coils, the coils are connected to the electronic unit in antiphase in such a way that the currents from the electromotive forces of the generating coils are directed opposite to each other and flow from the surface of the middle part of the housing between the coils, including the surface of the electrode, through the rocks, closing on the ends of the conductive housing, the current measuring means electrically connects the measuring electrode to the housing and allows the current of the electrode to be measured, the output of the current measuring means is connected to the electronic unit, characterized in that,that at least one additional electrode is located in the same cross-section as the measuring electrode, and all the electrodes are located in cutouts of the electrically conductive housing as axisymmetric segments and are made as sealed elongated covers of a large area, extended along the housing, electrically separated from the housing by insulators, each of the additional electrodes is equipped with a current measuring means, these current measuring means electrically connect the additional electrodes to the housing and make it possible to measure the currents of the additional electrodes, the outputs of these current measuring means are connected to an electronic unit that sums the currents of the measuring and additional electrodes and, based on the total current, determines the specific electrical resistance of the rocks.

2. The device according to paragraph 1, characterized in that at least one of the electrodes contains at least one electrode in the form of a button, which is electrically isolated both from the housing and from the adjacent electrode, and each of these electrodes in the form of a button is equipped with a current measuring device, which electrically connects the button electrode to the housing, the output of the current measuring device is connected to an electronic unit, which, based on the measured current of the button electrode, makes it possible to determine the specific electrical resistance of the rocks opposite this electrode, and when the housing rotates, the electronic unit will record an image of the borehole walls.

3. The device according to paragraph 2, characterized in that the current measuring means is made in the form of a low-resistance electrical connector having electrical contact on one side with an electrode, on the other side with an electrically conductive housing, with a toroidal coil placed on the connector, in such a way that the signal from the coil is proportional to the current flowing through the electrode.

4. The device according to paragraph 3, characterized in that the electrically conductive body is made in the form of a metal pipe with the ability to pass drilling fluid into an opening inside the pipe.