RU173699U1 - Device for electric logging through a metal column - Google Patents

Abstract

The utility model relates to the field of geophysical research of wells and is intended to determine the electrical resistivity of rocks (resistivity) by a borehole multi-electrode probe through a metal column. Technical result: a significant increase in the speed of logging, as well as the overhaul life of a downhole measuring probe. The essence of the utility model, which includes the ground part, consisting of an on-board computer, an interface unit and an alternating current source of probe power, electrodes B and Nud, and a downhole tool with a multi-electrode probe made in the form of a group of five or more electrode assemblies arranged in series and equidistant along the axis of the well. Each node includes two or more electric inputs located in a plane perpendicular to the axis of the well, in the extreme nodes of the group of electrodes, in addition to measuring M1 and Mn, there are current electric inputs A1 and A2, which are located in depth at the level of the measuring ones and are connected to the column at points not aligned with measuring contact points. All other electrode nodes in the group are only measuring ones. All probe electrical inputs have the ability to be pushed to the column wall using an electric drive with clamping mechanisms and, using the built-in shock mechanism, penetrate the body of the column. The downhole tool electronic unit includes an electrode clamp quality control unit. The probe measurement mode is pointwise. The downhole tool is lowered to a predetermined depth in the research interval, then the electric inputs are pushed to the surface of the casing using a mechanical drive, with the help of a shock mechanism they are periodically impacted to ensure the introduction of the pointed tips of the electric inputs into the body of the string, and at the same time, the unit is turned on using the on-board computer control of the quality of the electrode clamp, with the help of which the criterion of the quality of the electrode clamp is developed, information about the resistance The contact line is transferred to the ground-based on-board computer, upon reaching high-quality contacts, the shock operation on the electrical inputs is terminated, the control unit is disconnected from the input circuits, and the measurement cycle at the point begins. All digitized information signals are appropriately processed, filtered, and based on the proposed formulas, the resistivity of rocks is simultaneously determined by three or more depth points. 2 ill.

Description

The utility model relates to the field of geophysical research of wells and is intended to determine during the measurement process simultaneously at several points of electrical resistivity of rocks located equidistant along the axis of the well surrounding a cased metal casing.

A known method of electric cased hole logging based on a bipolar symmetric probe with five electrode nodes and the device for electric cased hole logging created on the basis of this method [1].

It consists of a surface and a borehole part. The ground part consists of an on-board computer, a probe current supply generator, a telemetry interface unit (TIS), a reverse current electrode B, and a remote electrode Nsp connected by communication lines. The ground part is connected through a multicore logging cable to the downhole part, which consists of a downhole tool with a flexible multi-electrode measuring probe, where electronic blocks, mechanical blocks and electrodes are located, three of which are equidistant measuring M1, N1, M2 and two are upper and lower current A1 and A2, symmetrically located outside the measuring electrodes. All electrodes are located sequentially along the axis of the well, each electrode includes two electric inputs connected in one circuit and located in a plane perpendicular to the axis of the well. In the probe part there are also: an electrohydraulic drive, a switch for the supply current, a meter for the probe’s supply current, potential and difference meters, and a controller with a TIS telemetry modem for communication with the on-board computer. To ensure the measurement process, all these elements are interconnected by electrical and mechanical communication lines.

The study with this device is carried out at points in a predetermined interval of the well, for this the downhole tool is first lowered to the desired depth, then the electrodes are pushed to the surface of the casing with an electrohydraulic actuator until contact is reached, cycles of measurements of the necessary parameters are carried out, they are digitized and filtered, and then the corresponding mathematical formulas determine the resistivity at one point in the depth of the well, after which the nodes of the electrodes are brought into the transport position. The device is moved to the next depth point, the electric inputs are again pressed to the surface of the column to conduct research and determine the resistivity at the next depth point. When performing the operation of extending the electric inputs, they are pressed against the wall of the well by periodic mechanical action on them with a hydraulic drive, by sequential multiple supply and discharge of increasing pulse pressure. The efficiency of providing electrical contact with the column is low. The time for which the "pumping" occurs (pressing the electrodes against the wall) is 20-30 seconds, the time for "releasing" (folding the electrodes) is 1-5 seconds. Thus, the time period of the impact of the electrodes on the wall will be 21-35 seconds, which reduces the speed of logging. This is a very smooth effect on the electric inputs, which is transmitted through an elastic medium (the entire volume of the hydraulic fluid under the working pressure). Fluid pressure pulses generated by a hydraulic actuator cannot have a significant effect on the contacting process, since the amplitude of the pulse pressure cannot be high due to the small ratio of the volume of injected fluid to the entire volume of the hydraulic fluid under the working pressure. These pulses are successfully damped not only by this volume, but also by the corrugations with a low modulus of elasticity that are present in the drive. In this case, the pulse energy is distributed, according to Pascal's law, to all available electrodes simultaneously. We can say that in this device, the contact of the electric inputs with the column is under the influence of static load, which makes it difficult to cut solid deposits on the wall of the column to the base metal, time is lost for repeated attempts to ensure contacts, which reduces the speed of logging. In this case, it is possible to assess the quality of the electrode clamp only after the measurements are taken, which leads to frequent errors and additional costs for duplication of measurements.

The exceptional complexity of the device should be noted: it is large in size: (6-8 meters), weight is about 100 kg, consists of a large number of moving units and seals that require expensive qualified maintenance, since the probe works in abrasive and aggressive environments, and large currents cause electrocorrosive processes. The overhaul life of downhole tools, as a rule, does not exceed the performance of work on one or two wells. Thus, the main disadvantages of this device include a low logging speed and a small working resource. In the measurement cycle at the point, one value of the resistivity is recorded. One value of resistivity requires at least one clamping operation. Large dimensions and weight worsen the possibilities of high-quality clamping of electrodes in complicated zones and complicate transportation and maintenance.

As a prototype of the utility model, the cased-hole electric logging device [2], based on the cased-hole electric-logging method [3], was selected.

The device described in these sources consists of a surface and a borehole part. The ground part includes an electronic unit, in which there is an on-board computer, an interface unit, a power supply unit for the current electrodes of the probe, and also electrodes N _beats . and B, interconnected by communication lines. The borehole part consists of a downhole tool with a five-electrode probe of a rigid structure, where three measuring electrodes are located, sequentially and equally spaced along the axis of the well and two current electrodes installed symmetrically outside the middle of the measuring electrode. In the downhole part there are also: an electric drive, a switch for current supply of current electrodes, a meter for supply current to the probe, meters for potentials of electrodes and their differences, and a controller with a telemetry system modem for communication with a ground-based on-board computer via a wireline cable.

The probe electrodes in the implementation are device-centering assemblies in which in the plane perpendicular to the axis of the borehole there are three pointed electrical inputs located at the ends of the movable mechanical elements, which simultaneously act as a centralizer, ensuring their movement and pressing against the inner wall of the column. All electrical inputs in the unit are combined in one circuit, this is necessary to ensure redundancy in case of falling into areas with violations of the column surface.

The study with this device is also carried out at points in a predetermined interval of the well, for this the downhole tool is first lowered to the desired depth, then, with the help of the device, the electrode assemblies are pressed to the surface of the casing until contact is made, cycles of measurements of the necessary parameters are carried out, their digitization and filtering, and then the corresponding mathematical formulas determine the resistivity at one point in the depth of the well, after which the nodes of the electrodes are brought into the transport position. The device is moved to the next depth point (usually no more than 0.5 meters), the electric inputs are again pressed to the surface of the column to measure the resistivity at the next depth point. In this case, it is possible to assess the quality of the electrode clamp only after the measurements are taken, which leads to frequent errors and additional time spent on duplicating measurements. From the experience of working with a device with a five-electrode probe, the average period of time between resistivity measurements is 4-6 minutes, that is, the logging speed is about 5 meters per hour. Typical logging intervals are 100-200 meters. The disadvantage of this device is the poor efficiency of ensuring electrical contact of the electrical inputs with the string, due to the presence of a contaminated and correlated layer on the casing. This affects the quality of the materials obtained during logging. For reliable contact with the column, it is necessary to carry out work on cleaning the well, involving equipment and specialists, and this affects the increase in the price of the work and research time. Given the need for additional operations of patterning and depth binding, detailing of measurements, repetitions with poor-quality preloading of the electrodes, the average logging time is from one to two days. This is unacceptable for a long time and much slower than the study by a competing method of carbon-oxygen logging.

The procedure is tiring for the staff, it requires a lot of labor.

Overhaul life of a downhole probe usually does not exceed one or two wells. Thus, the main disadvantages of this device include the low logging speed and low working life. In the measurement cycle at the point, one value of the resistivity is recorded. At least one resistivity value requires at least one clamping operation, the probe has large dimensions in length and weight, which impairs the ability of high-quality clamping of electrodes in complicated areas and complicates transportation and maintenance. It should be noted that if you simply increase the number of electrode nodes in this device, then the probability of high-quality contact of all the electrodes at the same time decreases sharply (if some get into the perforations, on the coupling joints or in the destroyed zones), in addition, with an increase in the number of complex movable nodes, the probability of failure-free operation of the probe is reduced, failures and jamming of the mobile system are possible when exposed to abrasive particles of cement and scale scattering from the surface of the casing That increase friction and wear. Therefore, the work on the point will have to be repeated until a positive result is obtained for all values of the resistivity. The quality of the clamp is evaluated after receiving the result by the resistivity and requires a complete measurement cycle. In this regard, the effect of increasing the speed of logging may not work. The disadvantage of this device is also the inefficient use of the nodes of the current electrodes A1 and A2 - during the measurement process, they are used as current alternately and significantly increase the probe length without increasing the number of resistivity measurement points.

The proposed utility model solves the problem of increasing the logging speed to an acceptable, competitive level of 15-25 m / h using compact probes with a minimum number of electrode nodes; these are typical probes with 5 or 7 electrode nodes, verified by many years of use.

At the same time, the logging speeds increase up to 3-5 times, and the overhaul life of their structures also increases up to 3-5 times, since it is mainly determined by the number of pressing operations on the logging interval.

A further increase in speed and working resource is no longer especially important, since it will not bring a significant economic effect.

The technical result is achieved in that in a utility model for electric logging through a metal column containing a downhole tool with a multi-electrode measuring probe, consisting of a body, mechanical blocks, an electronic block, a group of electrode assemblies of five or more, mounted sequentially one after another along the axis of the tool , each node includes at least two electric inputs located in a plane perpendicular to the axis of the well, where the current electric inputs A1 are located in the extreme two nodes of the group, 2 and measuring M1, Mn, the rest of the electrical inputs in the group are only measuring, all the electrical inputs of the multi-electrode probe are able to press against the wall of the metal column of the well, creating electrical contact with it using an electric drive and clamping mechanisms, an electronic unit that includes a controller connected via special communication lines with the probe current switch, electrodes and their potential meters, electric drive through a modem and wireline cable through a telemetry line onboard computer, the ground part, consisting of an onboard computer, interface unit, the power source of the probe and Nud and B interconnected by a communication line electrodes multiconductor logging cable and connecting the downhole device with the ground part. To achieve the goal, all electrode nodes are located along the axis of the probe sequentially at equal distances. Based on the original mathematical apparatus for processing signals in the module for calculating the values of electrical resistivity of rocks, the nodes of the current electrodes are also used as measuring ones, they are performed similarly in design. In the extreme nodes of the electrodes, the measuring electric inputs are at a current level in depth and are connected to the column at points that are not aligned with the current contact points, in addition, the electronic unit is additionally equipped with an electrode clamp quality control unit electrically connected to each electric lead, and the pressure mechanisms are supplemented by shock mechanisms providing the introduction of pointed electrical inputs into the body of the column, the on-board computer is additionally equipped with a special module of programs for the operational assessment of quality and pressing the electrodes and calculating the electrical resistance of breeds values for three or more points at a depth nip with the arising when measuring the interfering factors. Thus, for a probe with five nodes, instead of one resistivity point, three are recorded, for a seven-electrode probe, five are recorded, and for any multi-element probe, 2 resistivity points will always be recorded. Using the impact mechanism on the electric inputs to introduce them into the body of the column in conjunction with the clamp quality control unit and the module for the rapid assessment of the quality of the clamp significantly reduces the time required to prepare and conduct measurements. In addition, the use of this device eliminates the costly special operations of cleaning the wall of the column. The resistivity is determined by the following formulas:

specific electrical resistance corresponding to the i-th measuring group, consisting of three adjacent measuring electrodes equidistant along the axis of the probe, is determined according to the expression:

Where:

i=1, 2, 3…;

i = 1, 2, 3 ...;

K _g is the total coefficient,

K _ƒ is the root of the equation

K _ƒ · ΔU ₂ (I _A2 ) + ΔU ₂ (I _A1 ) = 0,

U _N is the potential of the central measuring node of the group relative to the day surface,

ΔU _i (I _{A1, A2} ) - potential differences between the extreme measuring electrodes of the i-th three-electrode group when applying current through the electrodes A1, A2, respectively,

отличаются от 0 только в двух случаях:Δu (I _A1A2 ) are the potential differences between the middle and lower electrodes of the 3-electrode group, and the corrections for the geometry of the current through the pipe

differ from 0 only in two cases:

The utility model is illustrated by the drawing in figure 1, which presents a block diagram of the proposed utility model. Figure 2 explains the relative position of the nodes and blocks. According to the text in the appeals to Figure 1, the name of the drawing (Figure 1) is not given, and references to the positions of Figure 2 are given in full.

A useful model for electric logging through a metal column contains a downhole tool with a multi-electrode probe 15, where the measuring electrodes M1, M2, M3, ... Mn corresponding to positions 9, 10, 11 ... 12, and current electric inputs are placed in the body of the device 36, figure 2 A1, A2, corresponding to positions 8, 13. In the housing of the electronic unit 31, figure 2, are placed: a switch of current electrodes 6, a digital meter of electric potential 7 relative to the remote electrode 3 - Nud, a digital meter of the difference of electric potentials of electrodes 17, a modem 30 for a telemetric communication line with the terrestrial part via a logging cable 24, a digital probe current meter 28 with a shunt 29, an electrode clamp quality control unit 22, including an electrode switching device 14, a current source 18 supplied to the electrical inputs to check their contacts, analog -digital converter for measuring voltages at the electrical inputs 19, controller 20, having communication lines with all electronic devices and units, used to control, as well as collect and transmit information signals. In the housing of the electronic unit 31, FIG. 2, an electric drive 25, FIG. 2 is also installed, including an electric motor 33, FIG. 2, a gearbox 34, FIG. 2, with an output shaft of the drive 35, FIG. 2, by means of which the clamping blocks of the electric inputs are controlled 26 and blocks of percussion mechanisms 27. The block of clamping electrodes, 26, Fig.2, and the block of percussion mechanisms 27, Fig.2, are installed in the housing of the device 36, Fig.2, in each of the nodes of the electrodes 37, Fig.2. All nodes of the electrodes have an identical design and are installed in the spring-loaded lever structures 41, figure 2, ending with pointed carbide-tapped electric inputs 40, figure 2, disclosed and folded using the shaft 35, figure 2.

The block of the percussion mechanism 27, Fig. 2, is a common mechanism of the type used in household perforators and drills for drilling concrete walls, where the rotational movement of the shaft with the help of spring-loaded cams is converted into the percussion movement of the hammer. In our case, using this mechanism, the rotational movement of the shaft 35, figure 2, is converted into the shock movement of the spring-loaded hammer, which is transmitted through the levers 41, figure 2, to sharpened electrical inputs 40, figure 2, and contributes to their incision into the body of the metal casing columns 5. On day surface 4 there is an on-board computer 21, an interface unit 23 for communication via a telemetric communication line with a downhole tool, a probe power source with trapezoidal bipolar pulses, as well as electrodes B-2 and Nud-3, connected are necessary and communication lines.

A multi-electrode probe is made in the form of a group of five or more electrode assemblies sequentially and equally spaced along the axis of the well, each node of the electrical inputs 37, FIG. 2, includes two or more electrical inputs 40, FIG. 2, located in a plane perpendicular to the axis of the well. In the extreme nodes of the group of electrodes, in addition to the measuring electrical inputs M1 and Mn, Figure 2, there are current electrical inputs A1 and A2, Figure 2, which are located at the measuring level, but are connected to the column 5, Figure 2, at points not aligned with measuring contact points. All other electrode nodes in the group are purely measuring.

Utility model work.

Point-to-point measurement mode. The downhole tool is lowered to a predetermined depth in the research interval, then all the electrical inputs using the electric drive 25, Figure 2, through the output shaft 35, Figure 2, and the clamping mechanism 26, Figure 2, are pressed against the casing 5, Figure 2. Using the impact mechanism 27, FIG. 2, a periodic impact is produced on them to ensure the introduction of the pointed tips of the electric inputs 40, FIG. 2, into the body of the metal casing 5, FIG. 2, at the same time they are turned on using the ground-based on-board computer 21, through the interface unit 23, modem 30 and controller 20, an electrode clamp quality control unit 22, a small current is sequentially supplied to each electrical input using a current source 18 and a switching device 14, and the voltage across each electric device is measured the lead, the magnitude of which produces a criterion for the quality of the pressure of the electrodes, the optimal contact resistance should be no more than 0.2 Ohms, information about the contact resistance of the controller 20 through the modem 30 through the wireline cable 24 and the interface unit 23 is transmitted to the ground board computer, upon reaching high-quality contacts the operation of exposure to the electrodes is terminated, the clamp quality control unit 22 is disconnected from the electrical inputs, and the measurement cycle at the point begins. Bipolar trapezoidal pulses of electric current are supplied to current electric inputs A1 and A2, positions 8 and 13, alternately, using a power supply 1, a switch of current electrodes 6 and electrode B, 2, and at each of the current supplies, they are measured using shunt 23 and ADC 28, applied current, the potential of one of the measuring electrodes, using a digital potential meter 7 and an electrode Nud 3, as well as the first and second differences at three or more points along the depth of the well using a digital meter of potential differences of electrodes. All digitized signals are appropriately processed, filtered, and based on them, using the original module for calculating electrical resistivity in the on-board computer, according to the proposed formulas, taking into account the interfering factors that arise when measuring, due to the proximity of the current electrodes to the measuring ones, simultaneously at three or more points depths determine the resistivity of rocks. Then, the electric drives 25 are folded into the transport position and the probe is moved to the next points of the research interval.

The layout of the utility model is tested in borehole conditions. The analysis of the obtained materials shows high quality and an increase in the logging speed, the work of the utility model has shown reliability, manufacturability, and ease of maintenance. The batch of instruments for cased hole electric logging, corresponding to this utility model, is nearing completion.

1. Krivonosov R.N., Kashik A.S. Method and device for cased hole electric logging No. 2306582 dated November 21, 2005. Abstract published on August 11, 2007

2. Rykhlinsky N.I., Brodsky P.A. and others. Patent No. 3661245 dated February 19, 2008.

3. Rykhlinsky N.I., Brodsky P.A. et al. Method for electric logging of cased wells. Patent No. 2382385 dated January 26, 2009.

Claims (13)

A utility model for electric logging through a metal column containing a downhole tool with a multi-electrode measuring probe, consisting of a body, mechanical blocks, an electronic block, a group of electrode assemblies of five or more, mounted sequentially one after the other along the axis of the device, each node does not include less than two electric inputs located in a plane perpendicular to the axis of the well, and in the extreme two nodes of the group are current electric inputs A1, A2 and measuring M1, Mn, the rest The s in the group are only measuring, all the electrical inputs of the multi-electrode probe have the ability to press against the wall of the metal column of the well, creating electrical contact with it using an electric drive and clamping mechanisms, an electronic unit that includes a controller that is connected via special communication lines to the supply current switch probe, measuring potentials of electrodes and their differences, electric drive, through a modem and a wireline via a telemetric communication line with the on-board computer, and the ground hour l, consisting of an on-board computer, an interface unit, a probe power source, as well as Nud and B electrodes interconnected by communication lines, and a multicore logging cable connecting the downhole tool to the ground part, characterized in that all electrode nodes are located along the probe axis sequentially at the same distances, in the nodes of the extreme electrodes, in addition to the current ones, measuring electric inputs are additionally installed, which are located at the current level in depth and are connected to the column at points that are not compatible connected to the current contact points, in addition, the electronic unit is additionally equipped with an electrode clamp quality control unit, electrically connected to each electric input, and the pressure mechanisms are supplemented by shock mechanisms, which ensure the introduction of pointed electric inputs into the column body, the on-board computer is additionally equipped with a special module for operational quality assessment programs the pressure of the electrodes and calculating the values of the electrical resistivity of the rocks at three or more depth points on the same clamp with the volume of interfering factors when measuring according to the given formulas: specific electrical resistance corresponding to the i-th measuring group, consisting of three adjacent measuring electrodes equidistant along the axis of the probe, is determined according to the expression:

Where i = 1, 2, 3 ...; K _g is the total coefficient, To _f is the root of the equation, K _ƒ · ΔU ₂ (I _A2 ) + ΔU ₂ (I _A1 ) = 0, U _N is the potential of the central measuring node of the group relative to the day surface, ΔU _i (I _{A1, A2} ) - potential differences between the extreme measuring electrodes of the i-th three-electrode group when applying current through the electrodes A1, A2, respectively, Δu (I _{A1, A2} ) is the potential difference between the middle and lower electrodes of the 3-electrode group, and the corrections for the geometry of the current through the pipe

differ from 0 only in two cases:

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