RU2631099C2 - Device for electrical logging through metal column - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is meant for determination of specific electrical resistivity of rock formation (SER) by downhole multipole sonde through a metal column. This device for logging includes superstructure and downhole device with multipole sonde designed as a group of five and more bundles of electrodes arranged in sequence and equispaced along the well axis. Each bundle includes two and more power points arranged in plain perpendicular to well axis. In end bundles of electrodes groups (except for measuring M1 and Mn) there arranged are current power points S1 and A2. All the other bundles of electrodes groups are only measuring ones. All the power points of the sonde have possibility to press to column wall using electric actuator with pressure mechanisms and to penetrate to the stem using built-in impact mechanism. Electronic unit of downhole instrument includes electrodes pressure quality control unit. Sonde measuring mode is point-to-point one.

EFFECT: increase in logging speed.

2 dwg

Description

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

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 arranged sequentially along the axis of the well, each electrode includes three 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 given interval of the well, for this, the downhole tool is first lowered to the desired depth, then the electrodes drive the electrode assemblies to the surface of the casing until contact is made, carry out measurement cycles of the necessary parameters, digitize and filter them, and then use the appropriate the mathematical formulas determine the resistivity at one point in the depth of the well, after which the nodes of the electric leads 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 invention, 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-element probe of a rigid design, where three measuring electrodes are located, sequentially and equidistant along the axis of the well, and two current electrodes installed outside them symmetrically with respect to the middle 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, and 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 corroded 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.

The overhaul life of a downhole probe usually does not exceed 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. 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 moving nodes the probability of failure-free operation of the probe is reduced, failures and jamming of the movable system are possible when exposed to abrasive particles of cement and scale falling off the surface of the casing s 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 invention 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 by the fact that in the device 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 device, each node includes at least two electric inputs located in a plane perpendicular to the axis of the well, where in the extreme two nodes of the group are current electric inputs A1, A2 and and measuring M1, Mn, the remaining 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 communication lines with a probe supply current switch, measuring potentials of electrodes and their differences, an electric drive, through a modem and a wireline via a telemetric communication line - with an on-board computer computer, and the ground part, consisting of an on-board computer, an interface unit, a probe power source, and also Nud and B electrodes, interconnected by communication lines and a multicore logging cable connecting the downhole tool to achieve the target, all electrode nodes are located along the probe axis in series equal distances. Based on the original mathematical apparatus for processing signals in the program for calculating the values of 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 input, and the pressure mechanisms are supplemented by shock mechanisms that ensure the introduction of pointed electrical inputs into the body of the column, the on-board computer is additionally equipped with a program for the rapid assessment of the quality of the electric clamp s and calculating the depth of the electrical resistance of breeds values for three or more points on a given nip arising when measuring the interfering factors. Thus, for a probe with five nodes, three are recorded instead of one resistivity point, five for a seven-electrode probe, and two more resistivity points will always be recorded for any multi-element probe. 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

K _g - the general coefficient determined empirically during calibration of the device,

Ω _z is the electrical resistance of the well section, determined by the formula

K _f is the root of the equation

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

- разности потенциалов между крайними измерительными электродами i-й трехэлектродной группы при подаче тока через электроды A1, A2 соответственно,

- potential differences between the extreme measuring electrodes of the i-th three-electrode group when current is supplied through the electrodes A1, A2, respectively,

- разности потенциалов между средними и нижними электродами трехэлектродной группы, а поправки на геометрию тока по трубе

отличаются от 0 только в двух случаях:

- potential differences between the middle and lower electrodes of the three-electrode group, and corrections for the geometry of the current through the pipe

differ from 0 only in two cases:

The invention is illustrated by the drawing in FIG. 1, which shows a block diagram of the proposed device; FIG. 2 illustrates the relative position of nodes and blocks.

A device for electric logging through a metal column contains a downhole tool with a multi-electrode probe 15, where in the device body 36, FIG. 2, measuring electrodes M1, M2, M3, ..., Mn are located corresponding to positions 9, 10, 11 ... 12, and current electric inputs A1, A2. corresponding to positions 8, 13. In the housing of the electronic unit 31, FIG. 2, a current electrode switch 6 is placed, a digital electric potential meter 7 relative to the remote electrode 3 is Nud, a digital electric potential difference meter of electrodes 17, a modem 30 for a telemetric communication line with the ground part, through a wireline 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 for checking their contacts, an analog-to-digital converter for measuring voltage measurement on the electrical inputs 19, the 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 also has an electric drive 25, FIG. 2, including an electric motor 33, FIG. 2, gear 34, FIG. 2, with the output shaft of the drive 35, FIG. 2, by means of which the clamping blocks of the electric inputs 26 and the blocks of the shock mechanisms 27 are controlled. The clamping block of the 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 electrode assemblies 37, FIG. 2. All electrode assemblies have an identical design and are installed in spring-loaded lever structures 41, FIG. 2, ending with pointed carbide electrodes 40, FIG. 2, opened and collapsible by means of the shaft 35, FIG. 2.

The block of the impact mechanism 27, FIG. 2 is a common mechanism of the type used in household rotary hammers and drills for drilling concrete walls, where the rotational movement of the shaft with the help of spring-loaded cams is converted into the impact movement of the hammer. In our case, using this mechanism, the rotational movement of the shaft 35, FIG. 2 is converted into the shock movement of a spring-loaded hammer, which is transmitted through levers 41, FIG. 2 to sharpened electric inputs 40, FIG. 2 and facilitates their insertion into the body of the metal casing 5. On the 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 by the necessary lines of communication.

The multi-electrode probe is made in the form of a group of five or more electrode assemblies located sequentially and equidistant along the well axis, 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. At the extreme nodes of the group of electrodes, in addition to the measuring electric inputs M1 and Mn, FIG. 2, there are current electric inputs A1 and A2, FIG. 2, which are located at the measuring level, but are connected to the column 5, FIG. 2 at points not aligned with the measuring contact points. All other electrode nodes in the group are purely measuring.

Device operation

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, FIG. 2, by means of the output shaft 35, FIG. 2 and the clamping mechanism 26, FIG. 2 are pressed against the casing 5, FIG. 2. Using the percussion mechanism 27, FIG. 2 produce periodic impact on them to ensure the introduction of the pointed tips of the electrical inputs 40, FIG. 2 into the body of the metal casing 5, FIG. 2, simultaneously turn on using the ground-based on-board computer 21, through the interface unit 23, the modem 30 and the controller 20, the 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 each electrical input, the value 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 Ohm, information about the contact resistance of the controller 20 through modem 3 0 through the logging cable 24 and the interface unit 23 is transferred to the ground-based on-board computer, when the quality contacts are reached, the operation of the action on the electrodes is terminated, the quality control unit of the clamp 22 is disconnected from the input circuits and the measurement cycle begins at the point. 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, it is measured using shunt 23 and ADC 28, supplied 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 well depth using a digital electrode potential meter. All digitized signals are appropriately processed, filtered, and based on them, using the original module for calculating the 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 depth points 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 device is tested in downhole conditions. An analysis of the materials obtained shows high quality and an increase in logging speed, the operation of the device has shown reliability, manufacturability, and ease of maintenance. The batch of instruments for cased hole electric logging corresponding to this device is nearing completion.

Literature

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 cased hole logging. Patent No. 2382385 dated January 26, 2009

Claims (14)

Device for electric logging through a metal column. comprising 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 includes at least two electrical inputs located in a plane perpendicular to the axis of the well, and in the outermost two nodes groups are the current electrical inputs A1, A2, the remaining electrodes 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 probe power supply current switch, electrodes and their difference potential meters, an electric drive, through a modem and a wireline cable through a telemetric communication line - with an on-board computer, and the ground part, consisting of an on-board computer, an interface unit, a probe power supply, as well as Nud and B electrodes connected by communication lines and a multicore well cable connecting the downhole tool, characterized in that all the electrode nodes are located along the axis of the probe sequentially at equal distances, in the nodes of the extreme electrodes, in addition to the current ones, measuring electric inputs are additionally installed, which are located at a current level in depth and are connected to the column at points, not combined with 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 pressing mechanisms are supplemented by shock mechanisms that ensure the introduction of pointed electric inputs into the body of the column, the on-board computer is additionally equipped with a program for the operational assessment of the quality of the electrode clamps and calculation of the electrical resistivity of the rocks from three or more depth points on one clip, taking into account the interfering factors when measuring using the above 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

K _g is the general geometric coefficient, determined using a grid mathematical model; Ω _z is the electrical resistance of the well section between the extreme measuring electrodes of the probe; K _f is the root of the equation, equal to K _f * 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 (I _{A1, A2} ) are the potential differences between the middle and lower electrodes of the three-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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