CN101819282A - Electrode for measuring formation resistivity - Google Patents

Abstract

The embodiment of the invention relates to an electrode for measuring formation resistivity, which belongs to the technical field of seismic exploration. The electrode comprises a main electrode, supervising electrodes and shielding electrodes, wherein the main electrode consists of one circular electrode and a plurality of azimuth electrodes; the plurality of azimuth electrodes are continuously arranged along the circumference of the circular electrode; and one pair of supervising electrodes for detecting whether the main electrode and the shielding electrodes on the two sides are equipotential or not is arranged on each of two axial sides of the circular electrode. The structure of the electrode shows that no supervising electrode is arranged in the main electrode of the embodiment, namely no complicated monitoring circuits, so the electrode for measuring the formation resistivity avoids interference efficiently in work. The electrode has no complicated monitoring circuits in the main electrode, effectively avoids interference in work, has a simple structure and accurate resistivity measured practically and is favaroable for popularization and use.

Description

An electrode for measuring formation resistivity

technical field

Embodiments of the present invention relate to the technical field of formation exploration, and in particular to an electrode for measuring formation resistivity.

Background technique

In the field of formation exploration, it is inevitable to measure the formation resistivity, and the accuracy of the measurement of the resistivity directly affects the oil and gas judgment of the measured formation. In the prior art, an electrode system is usually used as an electrode for measuring formation resistivity, which includes a main electrode, a monitoring electrode and a shielding electrode, so this electrode can realize three-dimensional resistivity measurement, that is, not only the resistance of the well wall can be realized It can also realize radial resistivity imaging.

However, since the monitoring electrodes are arranged around the azimuth electrode on the main electrode in the electrodes for measuring the formation resistivity in the prior art, the monitoring circuit in the main electrode is complicated, and the electrodes are easily disturbed when the electrodes are working. The actual measured The resistivity is not accurate, which is not conducive to the popularization and utilization of this electrode system product.

Contents of the invention

The purpose of the embodiments of the present invention is to provide an electrode for measuring the resistivity of the formation. There is no complicated monitoring circuit in the main electrode of the electrode, it is not easy to be disturbed during work, the structure is simple, and the actual measured resistivity is accurate, which is beneficial to Universal use.

In order to achieve the above object, an embodiment of the present invention provides an electrode for measuring the resistivity of the formation, the electrode includes a main electrode, a supervisory electrode and a shielding electrode, and it is characterized in that the main electrode consists of a ring electrode and several Composed of azimuth electrodes, the several azimuth electrodes are arranged continuously along the circumferential direction of the ring electrode, and a pair is provided on both axial sides of the ring electrode to detect whether the main electrode and the shield electrodes on both sides are Equipotential supervisory electrodes. It can be seen from this that there is no monitoring electrode in the main electrode described in this embodiment, that is, there is no complicated monitoring circuit, so it is not easily disturbed during operation.

In order to make the azimuth electrodes equipotential, the wires connected to each of the several azimuth electrodes are connected together in parallel.

In this embodiment, in order to enable the monitoring electrodes to better monitor whether the main electrode and the shielding electrodes on both sides are at the same potential, each pair of monitoring electrodes is arranged between the main electrode and the shielding electrodes.

In this embodiment, in order to effectively control the potentials of the main electrode and the shielding electrodes on both sides to be equal, the electrode for measuring the resistivity of the formation layer described in this embodiment further includes a control unit, and the control unit is used for when the monitoring electrode detects When it is detected that the potentials of the main electrode and the shielding electrodes on both sides are not equal, the potentials of the main electrode and the shielding electrodes on both sides are controlled to be equal.

As an example to obtain an ideal detection depth, in this embodiment, there are 6 shielding electrodes on both sides of the main electrode, which are equidistantly arranged in the radial direction of the main electrode.

In order to adapt to formations of different depths and ensure the detection depth in different formations, the present embodiment provides electrode systems with three lengths. When the length of the electrode used to measure the resistivity of the formation is 9.76 meters, the main electrode height The height of each supervisory electrode is 0.02 meters, the height of each shielding electrode is 0.5 meters, the distance between the main electrode and the supervisory electrode closest to the main electrode is 0.18 meters, and the distance between two supervisory electrodes is 0.08 meters. The distance between the shielding electrode closest to the main electrode and the supervisory electrode farthest from the main electrode is 0.22 meters, and the distance between each shielding electrode is 0.3 meters.

When the length of the electrode used to measure the resistivity of the formation is 7.76 meters, the height of the main electrode is 0.12 meters, the height of each supervisory electrode is 0.02 meters, and the height of each shielding electrode is 0.3 meters, the distance between the main electrode and the The nearest monitoring electrode spacing of the main electrode is 0.18 meters, the spacing between two monitoring electrodes is 0.08 meters, the distance between the nearest shielding electrode from the main electrode and the farthest monitoring electrode distance from the main electrode is 0.22 meters, and the distance between each shielding electrode is 0.22 meters. 0.3 meters.

When the length of the electrode used to measure the resistivity of the formation is 5.76 meters, the height of the main electrode is 0.12 meters, the height of each supervisory electrode is 0.02 meters, and the height of each shielding electrode is 0.2 meters, the distance between the main electrode and the The nearest monitoring electrode spacing of the main electrode is 0.18 meters, the spacing between two monitoring electrodes is 0.08 meters, the distance between the nearest shielding electrode from the main electrode and the farthest monitoring electrode distance from the main electrode is 0.22 meters, and the distance between each shielding electrode is 0.22 meters. 0.2 meters.

In order to detect formation resistivity at different orientation angles, there are 12 azimuth electrodes in this embodiment.

The electrode for measuring the resistivity of the formation described in this embodiment is not only less likely to be disturbed during operation, but also has a simple structure, and the actual measured resistivity is accurate, which is conducive to popularization and utilization.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is a schematic plan view of electrode distribution on an electrode for measuring formation resistivity provided by an embodiment of the present invention.

FIG. 2 is a detection characteristic diagram of the first type corresponding to the six detection levels of the electrode system in this embodiment.

FIG. 3 is a second detection characteristic diagram corresponding to six detection levels of the electrode system in this embodiment.

FIG. 4 is a second detection characteristic diagram corresponding to six detection levels of the electrode system in this embodiment.

Fig. 5 is a graph showing the detection of low-resistance formations by the direction electrode under six detection levels in this embodiment.

FIG. 6 is a schematic diagram of a resistivity change state corresponding to an azimuth electrode in this embodiment.

Fig. 7 is a graph showing the relationship between the detection depth and the resistivity change in this embodiment.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some of the embodiments of the present invention, but not all of them. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but not as a limitation to the present invention. Based on the embodiments of the present invention, all those skilled in the art can obtain without creative work Other embodiments all belong to the protection scope of the present invention.

The embodiment of the present invention provides an electrode for measuring the resistivity of the earth formation. The electrode is composed of a main electrode, a shielding electrode, and a supervisory electrode located between the main electrode and the shielding electrode. The two sides of the main electrode are symmetrically arranged, which can increase the detection depth.

The electrode provided in this embodiment for measuring the resistivity of the formation is a rod-shaped structure as a whole, as shown in FIG. 1 , which is a schematic plan view of electrode distribution on an electrode for measuring the resistivity of the formation provided by the embodiment of the present invention. It can be seen from Figure 1 that the main electrode 1 is located in the middle of the entire electrode. The main electrode 1 is composed of a ring electrode 11 and several azimuth electrodes 12. The ring electrode 11 is fixed in the middle of the rod-shaped medium, and the several azimuth electrodes 12 are continuously arranged in a circle along the circumferential direction of the ring electrode 11, so that the main electrode 1 can detect the resistivity of the formation medium at different azimuth angles through the azimuth electrode 12, and the difference from the prior art is that between these azimuth electrodes 12 There is no supervisory electrode to control each azimuth electrode to achieve equipotentiality. Several azimuth electrodes are only connected in parallel to each other to achieve equipotentiality. This avoids the use of complex monitoring circuits inside the entire electrode, such as 12 azimuth electrodes. 12 is continuously arranged in a circle along the circumferential direction of the ring electrode 11, so that the main electrode 1 can correspond to formations with different orientation angles from the radial direction through the 12 azimuth electrodes. When the main electrode 1 is energized, it can transfer current to the formation. The wires connected to each of the 12 azimuth electrodes are connected in parallel to make the 12 azimuth electrodes equipotential. In order to enable the main electrode 1 to transmit current to the formation more effectively, shielding electrodes 3 are also provided on both sides of the main electrode 1 in this embodiment to prevent the current from the main electrode 1 from spreading outward. Specifically, in the axial direction of the annular electrode 11 Several shielding electrodes 3 with the same polarity as the main electrode 1 are arranged on both sides. When the shielding electrodes and the main electrode 1 are at the same potential, the currents on the shielding electrodes 3 and the main electrode 1 repel each other, so that the current on the main electrode 1 The current is more concentrated to the formation. In order to detect whether the main electrode 1 and the shielding electrodes 2 on both sides are at the same potential, a pair of supervisory electrodes 2 are respectively arranged between the shielding electrodes on each side and the main electrode 1, one of each pair of supervisory electrodes is closest to the main electrode 1, and the other is the closest to the main electrode 1. One is the closest to the shielding electrode, so that the supervisory electrode 2 can detect whether the main electrode 1 and the shielding electrode 3 have the same potential through the electrode closest to the main electrode 1 and the shielding electrode 3 .

When the supervisory electrode 2 detects that the potentials on the main electrode 1 and the shielding electrode 3 are not equal, the control unit (not shown in Figure 1) in the electrode used to measure the resistivity of the formation layer controls the main electrode and the shielding electrodes on both sides. The potentials are equal. For example, when the monitoring electrode detects that the potential on the main electrode 1 is lower than the potential on the shielding electrode 3, the control unit adjusts the current on the main electrode 1 according to the detection result of the monitoring electrode to make it the same as the potential on the shielding electrode. The specific adjustment method can be realized by controlling components such as amplifiers, and those skilled in the art can completely adjust the potential on the electrodes through their general technical knowledge, so this embodiment will not repeat them here.

In this embodiment, there are 6 shielding electrodes on each side, which are equidistantly arranged in the radial direction of the main electrode. In this way, there can be 6 levels of repulsion to the current on the main electrode 1, so that there are 6 detection depths, and the more shielding electrodes involved, the stronger the repulsion effect on the current on the main electrode 1, so that the main electrode 1 transmits to the formation. The stronger the current is, the better the detection depth can be achieved, and the shielding electrode that does not participate in the shielding is used as the return electrode. Through the above narration, it can be seen that the electrode for measuring the resistivity of the formation described in this embodiment can not only detect the resistivity in the radial depth direction of the formation in the form of an electrode array (that is, the electrode array composed of the main electrode, the supervisory electrode and the shielding electrode), Moreover, the azimuth electrode on the main electrode can also be used to detect the resistivity on the strata with different orientation angles, so that the depth of the stratum detected by the electrode array is basically the same as the depth of the stratum detected by the azimuth electrode. According to different shielding levels, the electrodes described in this embodiment can measure 78 different resistivity values in total (6 different shielding levels, each shielding level can measure a main electrode resistivity and 12 azimuth electrode resistivity ), and the resistivity can be obtained according to the following formula.

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; k</span>}\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}$

为第i个监督电极的电位；In the formula,

is the potential of the i-th supervisory electrode;

I _j is the measured electrode current supplied

k is an instrument constant.

In order to adapt to formations with different depths and ensure the detection depth in different formations, this embodiment provides three kinds of lengths of electrode systems, namely electrodes for measuring formation resistivity. The total length of this electrode system is 9.76 meters. Wherein the height of the main electrode is 0.12 meters, the height of each monitoring electrode is 0.02 meters, the height of each shielding electrode is 0.5 meters, the distance between the main electrode and the monitoring electrode nearest to the main electrode is 0.18 meters, and the two monitoring electrodes The spacing is 0.08 meters, the spacing between the shielding electrode closest to the main electrode and the supervisory electrode farthest from the main electrode is 0.22 meters, and the spacing between each shielding electrode is 0.3 meters. Fig. 2 is the detection characteristic diagram corresponding to the 6 detection levels of the first type of the electrode system in this embodiment. In the first shielding level where only a pair of shielding electrodes repel the main electrode, the detection depth of the entire electrode is the shallowest, about 0.5 meters ; The detection depth of the entire electrode is the deepest in the sixth shielding level in which 6 pairs of shielding electrodes all repel the main electrode, which is about 1.5 meters.

When the length of the electrode used to measure the resistivity of the formation is 7.76 meters, the height of the main electrode is 0.12 meters, the height of each monitoring electrode is 0.02 meters, and the height of each shielding electrode is 0.3 meters. The nearest monitoring electrode spacing of the main electrode is 0.18 meters, the spacing between two monitoring electrodes is 0.08 meters, the distance between the nearest shielding electrode from the main electrode and the farthest monitoring electrode distance from the main electrode is 0.22 meters, and the distance between each shielding electrode is 0.3 meters. Fig. 3 is the detection characteristic graph of the second type corresponding to the 6 detection levels of the electrode system in this embodiment. In the first shielding level where only a pair of shielding electrodes repel the main electrode, the detection depth of the entire electrode is the shallowest, about 0.5 meters ; The detection depth of the whole electrode is the deepest in the sixth shielding level in which the 6 pairs of shielding electrodes all repel the main electrode, which is about 1.375 meters.

When the length of the electrode used to measure the resistivity of the formation is 5.76 meters, the height of the main electrode is 0.12 meters, the height of each supervisory electrode is 0.02 meters, and the height of each shielding electrode is 0.2 meters. The nearest monitoring electrode spacing of the main electrode is 0.18 meters, the spacing between two monitoring electrodes is 0.08 meters, the distance between the nearest shielding electrode from the main electrode and the farthest monitoring electrode distance from the main electrode is 0.22 meters, and the distance between each shielding electrode is 0.2 meters. Fig. 4 is the detection characteristic diagram of the third type of the present embodiment corresponding to the six detection levels of the electrode system. In the first shielding level where only one pair of shielding electrodes repels the main electrode, the detection depth of the entire electrode is the shallowest, about 0.5 meters ; The detection depth of the whole electrode is the deepest in the sixth shielding level in which 6 pairs of shielding electrodes all repel the main electrode, which is about 1.25 meters.

As shown in FIG. 5 , FIG. 5 is a graph of low-resistivity formation detected by the direction electrode under six detection levels in this embodiment. In Figure 5, the circumferential scale is the azimuth coordinate, and the radial coordinate indicates the resistivity. The number in the legend is the serial number of the direction electrode, for example, Rab NO.=1 means the electrode in the first direction. It can be clearly seen from Figure 3 that in each curve A section of the upper curve with a small curvature indicates that the plot at this azimuth is low-resistance. Since the azimuth corresponds to the azimuth electrode, when the low-resistance plot appears in which azimuth, the data detected by the azimuth electrode corresponding to the azimuth will be There will be changes.

In order to further illustrate that the azimuth electrode in this embodiment has better detection characteristics, as shown in Figure 6, Figure 6 is a schematic diagram of the resistivity change state corresponding to the azimuth electrode in this embodiment. When the bedrock resistivity is 100 ohmm, the resistivity of the block corresponding to the electrode at the sixth azimuth decreases gradually, and the change of the curve is more obvious. As shown in Figure 7, Figure 7 is a diagram of the relationship between detection depth and resistivity change. It can also be clearly seen from Figure 7 that for a surrounding rock with a resistivity of 100 ohm meters, a target layer thickness of 2 meters, and a resistivity of 100 ohms Midan tested a three-layer dielectric stratum in a low-resistivity block with a resistivity of 0.1 ohm-meter on the No. 6 azimuth electrode. The magnitude of the resistivity measured by the 6-direction electrode is the largest.

To sum up, the electrode used for measuring formation resistivity described in this embodiment is not only simple in structure, but also the actual measured resistivity is accurate, and it can effectively detect the radial depth of the formation and the formation corresponding to different orientation angles. There are no monitoring electrodes and corresponding complex circuits in the main electrode, so it is not easy to be disturbed during work. According to actual needs, the length of the entire electrode can be set to 9.76 meters, 7.76 meters or 5.76 meters, so that it can adapt to various ground conditions. , which is conducive to the popularization and utilization of this electrode system product.

Of course, the specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Within the protection scope of the invention, any modifications, equivalent replacements, improvements, etc. made within the logic and principle of the present invention shall be included in the protection scope of the present invention.

Claims (9)

1. electrode that is used for measuring formation resistivity, described electrode comprises central electrode, monitor electrode and guarded electrode, it is characterized in that, described central electrode is made up of a ring electrode and several azimuthal electrodes, described several azimuthal electrodes circumferentially continuously arrange along described ring electrode, and the axial both sides of described ring electrode are provided with a pair of whether equipotential monitor electrode of described central electrode and both sides guarded electrode that is used to detect.

2. electrode according to claim 1 is characterized in that, the lead that described several azimuthal electrodes connect separately is connected in parallel, so that described several azimuthal electrodes equipotentials.

3. electrode according to claim 1 and 2 is characterized in that, every pair of monitor electrode all is arranged between central electrode and the guarded electrode.

4. electrode according to claim 1 and 2, it is characterized in that, the described electrode that is used for measuring formation resistivity also comprises control module, described control module is used for detecting described central electrode and, controlling central electrode and equate with the current potential of both sides guarded electrode when unequal with the current potential of both sides guarded electrode when described monitor electrode detects.

5. electrode according to claim 4 is characterized in that, the guarded electrode of every side is 6, arranges radially going up equidistantly of described central electrode.

6. electrode according to claim 5, it is characterized in that, the described electrode length that is used for measuring formation resistivity is 9.76 meters, wherein said central electrode height is 0.12 meter, each monitor electrode height is 0.02 meter, each guarded electrode height is 0.5 meter, the nearest monitor electrode spacing of described central electrode and the described central electrode of distance is 0.18 meter, two monitor electrode spacings are 0.08 meter, nearest guarded electrode of the described central electrode of distance and the described central electrode of distance monitor electrode spacing farthest are 0.22 meter, and spacing is 0.3 meter between each guarded electrode.

7. electrode according to claim 5, it is characterized in that, the described electrode length that is used for measuring formation resistivity is 7.76 meters, wherein said central electrode height is 0.12 meter, each monitor electrode height is 0.02 meter, each guarded electrode height is 0.3 meter, the nearest monitor electrode spacing of described central electrode and the described central electrode of distance is 0.18 meter, two monitor electrode spacings are 0.08 meter, nearest guarded electrode of the described central electrode of distance and the described central electrode of distance monitor electrode spacing farthest are 0.22 meter, and spacing is 0.3 meter between each guarded electrode.

8. electrode according to claim 5, it is characterized in that, the described electrode length that is used for measuring formation resistivity is 5.76 meters, wherein said central electrode height is 0.12 meter, each monitor electrode height is 0.02 meter, each guarded electrode height is 0.2 meter, the nearest monitor electrode spacing of described central electrode and the described central electrode of distance is 0.18 meter, two monitor electrode spacings are 0.08 meter, nearest guarded electrode of the described central electrode of distance and the described central electrode of distance monitor electrode spacing farthest are 0.22 meter, and spacing is 0.2 meter between each guarded electrode.

9. electrode according to claim 4 is characterized in that, described azimuthal electrodes is 12.

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