JPS625167A - Non-polarizable electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to non-polarizable electrodes particularly useful in induced polarization measuring instruments. Furthermore, the electrode is useful in any electrical measurement circuit where a non-polarizable electrode is required.

In induced polarization measurement, a plurality of electrodes and a plurality of detectors are inserted into a poling hole, and the induced polarization of a portion surrounded by the poling hole is measured.

In particular, a current electrode is used to pass an alternating current through the formation, and a plurality of voltage electrodes are used to measure the in-phase and out-of-phase voltages generated in the formation. Such an induced polarization measuring device is described in US Pat. No. 4,359,687.

Since the induced polarization response in underground formations is very weak, extremely high precision is required for induced polarization measurements. In particular, electrical polarization of the voltage electrodes causes significant errors in the rough measurements obtained by induced polarization meters.

In the prior art, it has been proposed to use lead electrodes to measure signals in induced polarization meters.

For example, “Complex F” by 5nytier et al.
ormationResistivity-The F
Orgotten Half of the Re5i
stivity Log", 5PWLA 18th
Annual Logging Symposium,
An article dated June 5-8, 1977 describes the use of lead electrodes in induced polarization meters. However, lead electrodes are polarized, resulting in significant errors in induced polarization measurements. The lower the measurement frequency, the greater the polarization. Moreover, lead electrodes can have large asymmetric potentials depending on the drilling mud with which they come into contact, and thus
It is not possible to use a direct coupled amplifier with an induced polarization meter as described in No. 87.

The present invention provides a non-polarizable electrode for an induced polarization measuring device that can be used in a poling hole at high temperature and high pressure, thereby solving the above problems.

The electrode of the present invention consists of a closed container having a wall formed of a porous material, and an electrode that is made of a metal that produces chlorine salts that are only slightly soluble in water, and that is chlorinated to form chlorine salts on the surface. an electrode member mounted within the container and having at least one portion extending outside the container; a sealing means mounted to seal the electrode portion extending outside the container; and a sealing means mounted to seal the electrode portion extending outside the container. A saturated solution of potassium chloride and a chlorine salt of the metal forming the electrode fills the interior of the electrode, and is chlorinated to form a silver chloride film, which is immersed in the saturated silver chloride solution.

The non-polarizable electrode is preferably mounted in a flexible electrode container, one end of which is closed with a porous frit-type member. The vessel is filled with KCj) and AoCρ saturated electrolytes such that the electrodes respond to the potential developed in the poling hole fluid. A small amount of solid KCN and AQC1+ is placed in the vessel to ensure saturation at any temperature. The other end of the container may be formed by the male part of an electrical connector, the female part of which is mounted on the meter. Thereby, the electrode can be easily attached to the measuring device, and can be removed and stored after the measurement is completed.

By shaping the flexible electrode container with a porous frit, the salt solution inside the container can be made equal pressure with the poling hole fluid. Additionally, the frit prevents the ingress of contaminants in the poling hole fluid that could be harmful to the silver/silver chloride electrode. In addition, the container and frit are
KCj and AC] also helps maintain C1+ saturation around the electrodes. Yet another advantage is that the electrode is not in the direct current path in the poling hole, which may further reduce the possibility of electrode polarization.

The advantage of the non-polarizable electrodes of the present invention is that they have extremely low asymmetric potentials, which can reduce amplifier coupling in induced polarization meters and also provide compatibility between electrodes. . Therefore, any of these electrodes can be attached to any coupler on the meter.

Other advantages of the non-polarizable electrodes of the present invention include that they are stable, sensitive and reproducible. The electrodes are extremely durable and can operate under high temperatures and pressures such as those found in polling hole environments. It is also inexpensive and easy to manufacture. It can be used for any purpose, for example, because of its small size, the electrode can be easily mounted on a pad or in a suitable recess formed on the outside of the measuring probe.

The present invention will be more easily understood from the following description of preferred embodiments and the accompanying drawings.

FIG. 1 shows an electrode enclosed in a container 10. As shown in FIG.

The container 10 may be constructed of any material as long as it is electrically insulating and has sufficient flexibility, but a preferred material is V[5PEL (trademark, DuPon
Chemical Company, (Wilmington, Plowea). VESPEL
are preferred due to their durability, high temperature stability, machinability and surface tack which allows for strong epoxy bonding.

The left end of the container is closed with a porous frit member 11 which is seated on a shoulder 12 machined onto the inner diameter of the container 10. The porous frit member 11 may be any inert porous member, but for example, Coor
Preferably, it is formed from porous porcelain, such as manufactured by Porcelain Co., (Golden, Colorado). Preferably, the porous frit member 11 is secured to the container shoulder 12 with a suitable adhesive, such as epoxy, applied circumferentially.

The porous frit member 11 is selected such that the fluid can move only slowly within the frit while having good electrical continuity. For example, a C00rS unglazed porcelain plate P-1/2B-C having a porosity of 40% and a transmittance of about 1 mm Darcy satisfies this requirement.

In operation in a poling hole, the poling hole fluid pressure exerts pressure on the vessel 10, which is compressed and this pressure increases KCf! in the vessel. +AQCj solution is sufficiently transferred. This rapid equilibration of fluid pressure through the frit results in substantially no flow of poling hole fluid into the vessel. Although ionic diffusion through the frit still occurs, a sufficiently hermetic frit is used such that the total diffusion passage while the meter is in the poling hole is negligible. This reduces the possibility that the AG-AQ (Jl) electrode will be poisoned by contaminants in the drilling mud, such as sulfide ions.

Electrode 20 is formed from a solid iron of silver and has a spherical end. Silver rods are 99.990% pure and are commercially available from manufacturers such as Engelhard HetalS (New Chassis). The outer surface of the electrode must be polished to prevent voids from forming in the silver chloride coating when sintered at 900° C. for 24 hours after chlorination. The electrode 20 is located in the central hole 23
having a male portion 30 of the electrical connector enclosed therein. Preferably, the electrode 20 is crimped to the central lead 33. Alternatively, the central lead 33 may be soldered into the central hole 23.

Central lead 33 connects electrical connector 30 which can take various shapes.
is part of. A preferred electrical coupler is the Eyston
The product name EHLON (
This is a high-voltage connector manufactured by (Trademark). These connectors are coated with a hard insulating material that can withstand high i and high voltages, and are widely used in measuring instruments. The connector has a threaded portion 32 and an extension portion 31, and is screwed into a female threaded portion machined into the container 10. In particular, the silver electrode 20 extends through an opening 21 in the wall of the container and an O-ring 22 provided to seal the electrode within the container. O-ring 22 is compressed by extension 31 as the connector is screwed into the container.

A threaded section within the container 10 allows the container to be unscrewed from the connector and fresh electrolyte solution filled into the container. The connector 30 also integrally includes a flexible ring 34, which is further coupled to the wall of the induced polarization meter.
It mates with the female ON connector (not shown) to form a pressure tight seal.

The silver electrode is chlorinated before being placed in the container. In particular, the electrodes are placed in a glass dish filled with a reagent grade 0.1H potassium chloride coating solution. Preferably, a platinum screen is placed in the center of the dish as a cathode, and a plurality of silver electrodes are placed around it at equal intervals. The film forming current is about 5 mA per 1 Cd of electrode surface area. Therefore, the diameter is 0.3α, the length is 2.5
To manufacture six cIm electrodes, the coating current is approximately 61 A per electrode, or a total of 3611 IA. If a magnetic stirrer is provided at the bottom of the film forming section, more uniform film formation can be obtained. Alternatively, an ultrasonic bath may be used.

As film formation progresses and gas bubbles appear on the electrode surface, the current is gradually lowered and the glass dish is agitated to remove any air bubbles that stick to the surface. Chlorination is terminated when the resistance per electrode, measured between cathode and anode, begins to increase substantially. In the six electrode case described herein, termination occurs when the resistance per electrode exceeds approximately 850 ohms. The resistance per electrode is determined by measuring the supply current and voltage and dividing the current per electrode by the total voltage.

Other methods for preparing silver chloride surfaces are also possible, such as thermal methods based on the decomposition of AQO and AqC1103 pastes in a furnace, electrolytic formation of AQCI on eyes thermally deposited on a platinum substrate. There is a thermal/electrolytic method that performs this, or a similar method, the silver chloride precipitation method. These methods are l Ve
“Reference elc” by S. and Jan.Z.
trodes”, Academic Press
.

New York (1961).

After the chlorination operation, the electrodes were electrically shorted together and diluted KCI! 'Store in solution for at least 15 hours to age harden. If the electrodes are to be stored for a long period of time, they are stored in separate containers in a dark place in a solution saturated with KCj and AoC1+. Shorting the electrodes together and storing them for long periods of time reduces the asymmetric potential. The asymmetric potential of these electrodes is typically 100 μV or less.

Container 10 is filled with a solution saturated with KCI and AQ (4). By using potassium chloride solution, the junction potential during drilling mud junction can be minimized. This is because the transport numbers of both potassium and chlorine are approximately equal to 0.5. The use of a saturated KCj solution eliminates the need for accurate concentration measurements in the hole. Additionally, the high electrical conductivity of the saturated KC4+ solution enhances the electrical contact to the poling hole fluid. Another advantage of using a saturated KCR solution is that it can minimize poisoning of the electrode by sulfide, bromide or other ions in the poling pores. This is because the large amount of potassium and chloride ions in the KCj) solution inhibits the adsorption of contaminant ions onto the silver surface.

Solution container 10 is also saturated with respect to AQCI, preventing dissolution of the AgCl coating in saturated KCl. Furthermore, a saturated AoCi) solution provides a constant activity of the silver chloride in solution and thus a constant reference potential at a given temperature.

By storing the electrode in the same solution used in measurements in the polling hole, the properties of the electrode are preserved constant. This is highly desirable since fewer adjustments are required when changing electrodes.

The electrodes are typically mounted in recesses formed in the outer surface of the meter.

In another embodiment, the silver/silver chloride solution can be used without the VESPE L container, although the possibility of poisoning the electrodes by polling hole contaminants is increased.

Other types of reversible electrodes of the second type are also included within the scope of the invention, such as zinc/zinc chloride,
Cadmium/cadmium chloride, thallium/thallium chloride, etc. All of these electrodes are not as stable as silver/silver chloride and are more soluble under many conditions, which limits their use. Similarly, silver halides other than silver chloride can be used, but silver/silver chloride is preferred because there are many chloride ions in the polling hole mud.

In still other embodiments, KCl) and AqCρ
The saturated solution can also be replaced by a suitable gel, such as eg agar-agar, saturated with KCl and AaCj. By using a gel, fluid and ion exchange with the polling hole mud can be further reduced.

Agar-agar gel mixture is prepared by mixing 3x agar-agar powder into KCj and AaCj) saturated salt solution. Heat the solution to dissolve the agar-agar, mix gently, and cool to form a gel.

In yet another embodiment, the silver electrode of FIG. 1 can be an electrode made of sintered porous silver. Although it requires an extra step in manufacturing, this embodiment provides a much larger surface area and protects the coating by having most of the silver chloride coating in the internal porous space. Sintered porous silver is produced by compressing fine silver particles and sintering them in a reducing gas atmosphere. The sintered porous silver is then chlorinated as described herein.

Another practical tIA embodiment uses a cylindrical silver rond electrode as a disc-shaped electrode, which is used, for example, in a pad-type induced polarization measuring device. The thin profile design of the electrode allows multiple electrodes to be attached to the pad, which can be pressed against the walls of the polling hole.

Yet another embodiment replaces the silver chloride rod of FIG. 1 with a coiled silver chloride wire.

This coiled silver wire can also be used in pad-type meters where the electrodes are arranged in concentric rings.

Those skilled in the art will be able to create various variations and modifications of the apparatus and methods described herein without departing from the inventive concept. It is therefore to be clearly understood that the apparatus depicted in the accompanying drawings and the foregoing description are for illustrative purposes only and are not intended to limit the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one example of the electrode of the present invention.

Claims (11)

[Claims] (1) An electrode member consisting of a closed container having a portion formed of a porous material on the wall and a metal that produces chlorine salt that is only slightly soluble in water, and that forms chlorine salt on the surface when chlorinated. , the electrode member mounted within the container and having at least one portion extending outside the container; a sealing means mounted to seal the electrode portion extending outside the container; and filling the inside of the container. , a non-polarizable electrode consisting of a saturated solution of potassium chloride and a chloride salt of the metal forming said electrode. (2) The non-polarizable electrode according to claim 1, wherein the metal is silver. (3) The non-polarizable electrode according to claim 1, wherein the container is cylindrical and one end wall of the cylindrical container is formed of a porous material. (4) The non-polarizable electrode according to claim 3, wherein the electrode member has a solid rod shape. (5) The non-polarizable electrode according to claim 3, wherein the electrode member is a sintered porous silver rod. (6) The electrode according to claim 1, wherein the container is filled with a saturated solution of KCl and AgCl. (7) The non-polarizable electrode according to claim 1, wherein the metal is selected from cadmium, zinc and thallium. (8) The electrode according to claim 1, wherein the electrode member is a solid cylindrical member. (9) The electrode according to claim 8, wherein the sealing means is an O-ring seal surrounding the electrode member. (10) An electrode further comprising a pressure-resistant and fluid-proof electrical connector installed in the container and electrically connected to one end of the electrode member, wherein the electrode member has a central hole, and the electrical connector 10. The electrode of claim 9, wherein the electrode has a pin-shaped central electrode, the pin-shaped electrode being electrically and mechanically fixed in the hole of the electrode. (11) The electrode according to claim 1, wherein the electrode is mounted on an induced polarization measuring device.