SU1478179A1 - Method and apparatus for electric logging of holes - Google Patents

Abstract

The invention relates to the field of geophysical research and is intended to study the geological wellbore resistivity of electrical resistance. The aim of the invention is to increase the resolution of apparent depth resistance by eliminating screen effects caused by the enclosing horizons. The method includes exciting an electric field at a well axis with a given current strength, measuring at different predetermined potential distances and potential differences, additional excitation at the well axis with a current equal to the current strength of the first excitation, and additional measuring the potential of the electric field at the point of measuring the potential difference and measuring profiling parameters. A device for carrying out the method contains potential and gradient probes with a common single-pole current point electrode, potential and gradient probe meters, a second potential probe with a single pole current electrode and a generator, the length of the second potential probe being equal to the length of the first potential probe and its recording point is combined with the recording point of the gradient probe and the multiplying-dividing unit electrically connected to the outputs of the potential meters of all probes. 1 hp f-ly. 1 il.

Description

to supply a common single-pole point electrode A ,, measuring electrode M 3 of the first potential probe, measuring potential 4 of the first potential probe, measuring M and N electrodes 5 - M and 6 - N gradient probe, measuring 7 potential differences of measuring electrodes M and N, the second single-pole point electrode A2-8 of the second potential probe, length ,,, the second current generator 9 for supplying the second single-pole point electrode A2, the second measuring electrode of the second potential probe whose recording point is aligned with the recording point gradient probe (middle between electrodes M, N), second potential meter 11 of the second potential probe, multiplier-dividing unit 12 for multiplying the gradient probe signals and the second potential probe between them and dividing them by a potential probe signal with a common unipolar point electrode A ,, the recorder 13 of the measured profiling parameter, the wall of the well 14, along which profiling is carried out

The essence of the proposed method is as follows:

If the current source is in an environment that is symmetrical in resistance (p) relative to the horizontal plane, then, due to symmetry p, the current density on both sides of the source is the same as in a reservoir with unlimited capacity (H °°).

When the source crosses the contrast boundary, the current density distribution on the opposite sides of the source changes dramatically, which causes the characteristic shape of the gradient-probe profiling curves (screen maxima or minima). The asymmetrical shape of the gradient probes is caused by the occurrence of asymmetry p, which changes the current density distribution above and below the source. This significantly narrows the range of correctly solved inverse problems when interpreting the BKZ "

The method includes the following steps.

1. Excitation of the studied medium with a current of a given magnitude I using a single-pole source and measurement at a distance L ,, equal to 0.4-0.5 m, along the axis of the well potential of the field

and at a distance x C ,, equal to about 0.5 m; 1m; 2 m; 4 m; 8 m - potential difference floor,

2. Excitation of the studied medium by a current of a given value I of an additional single-pole source located at a distance L ,, from each registration point, the difference

Q potentials, and the measurement at these points of the potential of the field, caused by the action of an additional source.

3. The multiplier-dividing operation of the measured signals from the three receiving sensors corresponding to each probe of different length L2 and the registration of the profiling parameters pk of each probe Z.

The device works as follows.

From the current generator 2, the current of magnitude I enters the single-pole point electrode, which belongs to the potential probe A, M 1 and 3, and the gradient ent probe ArMN-l, 5 and 6.

From the second current generator 9, the current of magnitude I enters the second single-pole point electrode A-8, which belongs to the second potentiometer A2 probe A2M2 1 and 10, the measuring electrode Mg-10 of which is aligned with the registration point (middle between the electrodes M, N) gradient - probe, 5 - and 6. Signals taken from the measuring electrodes,

M2-10 and MN-5 and 6, previously

are amplified by measuring 4, 11 and 7 potentials respectively.

Using the multiplication unit 12, the signals from the outputs of the potentiometer 7 and 11 are multiplied together and are divided by the signal from the output of the potential meter. The result of a multiplier-separating operation at the output of a multiplier-division block is recorded by the registrar 130

0

five

Claims (2)

Invention Formula 1 "Method of electric logging of wells, including the excitation of the electric field of the studied section on the axis of the well by a single pole source with a given current strength, measurement of the potential and the potential difference of the electric field at different predetermined distances and the formation of profiling parameters the borehole, characterized in that, in order to increase the resolution of the apparent resistance in depth by eliminating screen effects, the potential of the electric field created by additional excitation on the borehole axis with a current equal to the first excitation current is additionally measured at the point of measuring the potential difference , and at a distance equal to the distance between the point of the first excitation and the point of measurement of the potential, and the profiling parameter pk is determined by the formula Wg to r "e UA, M, and A2M2 di we L UMN U, I Uft, M, -potential measured at a given distance of 1 c from the first source A; -potential, measured at a given distance L, from the second source A2; potential difference, measured at a given distance from the first source I - the current value of each source; K - geometric coefficient gradient probe A, MN. 2. A device for electrical well logging, containing potential and gradient probes with one single pole point electrode and current generator, as well as potential and gradient probes meters, characterized in that the device is additionally introduced into the device. a potential probe with a second current generator and a second potential meter, as well as a multiplier-dividing unit, the measuring electrode of the second potential probe being connected to the second potential meter, the second single-pole point electrode is connected to the second current generator, and all the potential-and gradient-probe meters are connected to the multiplier-dividing unit, while the length of the second potential probe is equal to the length of the first potential probe, and the recording point of the second potential probe is aligned with the recording point of the gradient probe, the gradient probe length is longer than any of the potential probes V