RU2690711C1 - Cased well electrical logging device - Google Patents

Abstract

FIELD: geophysics.SUBSTANCE: invention relates to well geophysical survey and is intended for determination of specific electrical resistance of rocks through cased wells. Summary: cased well electrical logging device consists of electronic unit, centering devices, probe containing clamping devices, electrodes arranged in series along well axis. Current electrodes are arranged on centering devices. Measuring electrodes are installed with the possibility of elastic clamping to internal walls of the cased well by means of electrically insulated levers and clamping devices. Measuring electrodes are equipped with sealed drives with output shafts and electric contacts at output shafts and are made in the form of cutting or abrasive tools. Drives are installed in electrically insulated levers.EFFECT: increased speed of logging due to considerable reduction of time for introduction of electrodes into column body, increased reliability and repairability due to simplified design, which works in aggressive well environment.3 cl, 3 dwg

Description

1. Field of technology

The invention relates to the geophysical studies of the well and is intended to determine the electrical resistivity of the seams of rocks surrounding the cased metal well.

2. Prior art

A device for “electrical logging of a cased well” is known (RU 2 306 582, 21/11/2005, IPC G01V 3/20 (2006.01)) equipped with a multielectrode probe and measures the current through the electrodes and the potential of the electric field. Measurement is performed with repeated clamping of the measuring electrodes of the probe under the influence of a pulse-increasing hydraulic pressure necessary to ensure contact of the measuring electrodes with the column.

The main drawback of the device is the use of hydraulic systems of the measurement actuator and the use of a pulsed static junction of the electrode using a liquid transmission medium. This causes the heterogeneity of the clamping of the electrodes, as the distribution of the area of junction of each individual electrode, and the integral heterogeneity of indicators of junction between the electrodes.

The device consists of a five-electrode probe, made in the form of three measuring electrodes serially and equally remotely along the axis of the well and installed outside the measuring symmetrically with respect to the average measuring electrode of the two current, ground-based current source for alternatingly supplying electric current to the current electrodes and measuring the potential of the electric field hydraulic actuator connected through actuators with retractable lever self-folding centralizers on which ryh electrodes arranged in the form of tungsten carbide spikes with spring-loaded cylindrical guides. The electrodes are made in the form of a tapered tip, introduced into the casing. The device has a special safety unit, which is triggered by a cable, designed to fold the electrodes when the hydraulic drive fails, when the electrodes are pressed against the casing string.

The disadvantage of this device is the complexity of the design of actuators, low reliability of the safety device in case of drive failure.

The actuator is a complex telescopic system into which pressure is supplied from the hydraulic drive.

The operation of the device consists of the steps of extending the electrodes, pressing them against the borehole wall, periodically mechanically acting on the electrodes by a hydraulic drive by sequential multiple feed and dumping of increasing pulse pressure.

The reliability of ensuring electrical contact with the column with this method is low. The time during which the electrodes are pressed against the column wall is tens of seconds, which reduces the logging speed. This is a very smooth effect on the electrodes, fluid pressure pulses generated by an electromagnet are strongly quenched in a large volume of hydraulic drive hydraulic fluid, as well as polymer hoses and corrugations with a low modulus of elasticity present in the drive. At the same time, the pulse energy is distributed to all the available electrodes simultaneously, all this makes it difficult to cut solid deposits on the column wall to the base metal, time is lost in repeated attempts to provide contacts, which also reduces the logging speed. Practical use of devices with the claimed telescopic system in the well showed their low reliability due to the wedging and leakage of the telescopic seals, which is associated with an aggressive downhole environment, with the presence of fine solid particles of corrosion products of the column, cement, salt deposits, etc. in the fluid

As a result, the probability of leaving the instrument in the well is high. A device is known for electrical logging through a metal column (RU 2 489 73407, 11.2011, IPC G01V 3/20 (2006.01) EV 47/125 (2012.01), containing a multi-electrode downhole probe, a drive design having an output shaft that drives the centering mechanism. The measurement is carried out with a contact (clamp) under the impact of the electrical leads-electrodes against the wall of the casing with the incision of electrical leads into the wall of the casing.

The main drawback of the device is low reliability and, as a result, low accuracy of the results of mechanical measuring systems.

This device is a drive design having an output shaft that drives the screw pairs. During the direct rotation, the screw pairs elastically press the electrodes against the wall of the casing string, and a shock effect produces a periodic effect on the levers rigidly connected with the electrodes. When this occurs, the plunging of the electrodes into the wall of the casing, the impact occurs at the exit from the screw interaction of the screw and nut, pressed by the force spring. During the reverse rotation of the shaft, the screw interaction is restored in screw pairs, the electrodes return to the initial position, and then the screw ridges again come out of the screw interaction, but from the other ends. This achieves automatic positioning of the electrodes in the extreme positions. The disadvantages of the device are: low reliability, which is due to the complexity of the mechanical design and the rapid wear of the surfaces of the parts when working in an aggressive environment with the inclusion of abrasive particles. This leads to failures, small turnaround time and difficulty in preventive maintenance. The device requires special expensive coatings, it takes a long time for the operation of reliable introduction of electrodes into the body of the column. It is practically impossible to implement structures in small diameters (less than 55 mm) due to its considerable complexity. The lack of design also needs to be attributed to the fact that it is not universal, it requires interchangeable lever elements with protective assemblies when operating in wells with internal diameters of more than 170 mm.

A device for electrical logging of a cased well is known (RU 2610340, 09.09.2014, IPC G01V 3/20), consisting of a ground-based current source, a geophysical cable, a housing, a power drive, a probe containing electronic components and electrodes of a borehole part of a multielectrode probe with pointed inserts, which have the ability to nestle on the wall of the metal column of the well, the actuator of the electrode, having the ability to make reciprocating movement of the electrode across the axis of the well.

The disadvantage is a high measurement error with a rather complex structural scheme of the device.

It is also known a device for electrical logging of cased wells (RU No. 2361245,19.02.2008, the IPC G01V 3/22),

The device consists of surface and borehole parts.

The ground part (day surface) includes an electronic unit in which the on-board computer is located, a peripheral unit, a probe power supply, as well as _Nd and B electrodes connected by communication lines. The downhole part consists of a downhole tool with a five-electrode probe of rigid construction, where the measuring electrodes are located, are installed sequentially and equidistant along the axis of the well and two current electrodes, installed outside of them, symmetrically relative to the average measuring electrode. In the borehole part there is also an electric drive, a probe supply current switch, a probe supply current meter, electrode potential meters and their differences, and a controller with a modem of a telesystem for communicating with a ground-borne computer via a logging cable.

The electrodes are mounted on a drop-down lever centralizers with upper and lower levers, one ends of which are pivotally connected to common axes and connected to the drive through actuators, the drive is equipped with a rotating shaft having sections with helical surfaces whose number is equal to the number of actuators. Electrodes located on the common axes of the centralizer arms are made in the form of carbide identical rollers freely rotating on common axes, the peripheral parts of the rollers are made in the form of sharply sharpened edges or teeth, the second ends of the upper arms are connected to the housing. Each actuator is a screw hub associated with the screw part of the shaft, bounded by two shoulders, between which there is a ring, which is elastically pressed by springs to the upper collar, with the ring pivotally connected to the second ends of the lower arms of the centralizers. The drive of the device has limit switches with a special mechanism for automatic switching off in the end positions.

The disadvantage of this device is low reliability, it includes a large number of moving and rubbing components, which, when operating in an aggressive downhole environment with abrasive inclusions, leads to failures and requires frequent maintenance and repair.

The disadvantage of this device is the low efficiency of ensuring the electrical contact of the electrodes with the wall of the column, as a smooth preload of the electrodes by the actuator springs does not ensure reliable forcing of the corrosion layer, as well as salt and cement deposits on the wall of the column before diffusion with the metal. For reliable contact with the column before logging, it is necessary to carry out special work on cleaning the well, and this leads to a significant increase in the cost of work and an increase in the time for research. The device also has the disadvantage due to the presence in the design of a movable electrical contact between the rotating rollers of the electrodes and the input circuits of the potential meters. Since the moving contact is in a liquid medium, essentially in an electrolyte, the electrochemical potential that changes over time between the surface of the roller and its axis is a serious hindrance and in most cases does not allow for qualitative research.

The design is complex and practically unrealizable in small dimensions (outer diameter less than 55 mm), for operation in wells of small diameter.

3. The invention

3.1. Setting a technical problem.

The aim of the present invention is to provide reliable, fast contact of the electrodes with the surface of the column, simplify the design, speed up the assembly and debugging process, increase reliability and maintainability compared with the prototype, as well as the possibility of implementing the design in small diameters.

3.2. The result of solving a technical problem.

The device uses an electrode made in the form of a rotating contact element (disk, drill), the contact of which provides a tight junction of the electrode to a clean metal surface and the reduction of parasitic electrochemical potentials.

3.3. Features

In contrast to the known solution, the measuring electrodes of the device are equipped with hermetic drives with output shafts including electrical contacts, the drives being mounted on insulated levers, and the measuring electrodes are connected to the output shafts transmitting rotation to the electrodes.

An electrical logging device in which the measuring electrodes can be made in the form of rotating disks or cutting conductive tools.

Execution can ensure the rotation of the electrode discs across the axis of the well.

The output shafts are connected to the measuring electrodes by a flexible coupling, and the axis of rotation of the electrodes is rotated by an angle relative to the axis of the well.

In the device, the clamping devices are drums equipped with free-wheeling mechanisms, springs and flexible rods, the drums being coaxial with the output shafts of the drives, connected to them through the free-wheeling mechanisms and electrically insulated from them, the springs with the free ends resiliently supported by insulated levers, and thrusts are connected on one side with the drums, and on the other side are connected to the probe.

3.3. List of drawings

FIG. 1 shows a schematic representation of the proposed cased-hole electrical logging device; in fig. 2 shows a fragment of a probe with a drive and a pressure device of a measuring electrode, made in the form of a gear; in fig. 3 shows a fragment of the probe with a drive and a clamping device of a measuring electrode, made in the form of a drill, where

1 - electronic unit of the underground part of the device, 2 - centering devices, 3 - probe body, 4 - electrically insulated levers, 5 - pressure device springs, 6 - flexible pressure arms, 7 - registration and control unit, 8 - on-board computer, 8a - current source, 9 - drive of electrode in lever 4, 10 - driver of drive motor 9 with communication modem, 11 - connector of electrical contacts for connection of driver 10 with electronic unit 1, 12 - electric motor with encoder, 13 - gearbox, 14 - output shaft, 15 - contact on the output shaft, 16 - Hall sensor associated with a modem connection zi, 17 - axis, 18 - drums of clamping devices coaxial with output shaft 14 and with flexible duct 6, 19 - Shaft coupling key 14 with free-running mechanism 22 and toothed wheel 23, 20 - reverse current electrode "B", 21 - screw mounting the free end of the thrust 6 in the housing 3 of the probe, 22 — mechanisms for the free motion of the drums, 23 — a disk in the form of a gear wheel or wheel with an abrasive coating, functionally being a current electrode (Mn), 24 — a bar connecting the shaft 14 with the free wheel mechanism 22, 25 - fixing nut. 26 - flexible cable connecting shaft 14 with a gear wheel 23 (electrode Mn), 27 - mounting screw on the body 3 of the flexible cable, 28 - mounting bracket on the body 3 of the flexible cable, 29 - magnet, 30 - additional body, 31 - screw, 32 - bearing, 33 - flexible shaft, 34 - drill (in a collet device for fastening a cutting or abrasive tool);

A1 and A2 - current electrodes; M1, M2, M3, ... Mn, - measuring electrodes; In (20) - reverse current electrode; Ok - electrode beats

The electronic unit 1 contains: a potential meter of the electric field of one of the measuring electrodes of the probe, a meter of potential differences of neighboring measuring electrodes, an electronic device for a telemetric system for transmitting data from the outputs of the meters and receiving control commands from the day surface.

4. Description of the device

To achieve this goal, in a device that includes an electronic unit, centering devices, a probe containing pressure devices, electrodes are successively located along the axis of the well, with current electrodes A1 and A2 located on centering devices, and equidistant spaced measuring electrodes (M) are installed with the possibility of elastic clamping to the inner walls of the cased hole by means of electrically insulated levers and pressure devices, a ground-based current source for supplying electrical Into current electrodes, including through a reverse current electrode B, an electric field potential meter of one of the measuring electrodes relative to a remote electrode Nud, an electric field potential difference meter between adjacent measuring electrodes, a probe supply current meter, an on-board computer with a recording and control unit for control processes during logging and computation based on the obtained data on the electrical resistivity of the rocks, the measuring electrodes are equipped with metichnymi drives the output shaft and the electrical contacts on the shafts, which are in the air, thus avoiding the appearance of large electrochemical potential is a hindrance. The actuators are installed in insulated levers, and the measuring electrodes are connected to output shafts that transmit the rotation to the electrodes.

The measuring electrodes can be made in the form of tips of cutters, wheels, gears, drills, etc. rotation which provides rapid destruction of deposits on the borehole wall.

The clamping devices can be made in the form of drums, which are equipped with free-wheeling mechanisms and flexible rods, the drums being coaxial with the output shafts of the drives and connected to them via the free-wheeling mechanisms and electrically isolated from them, the springs with their free ends resiliently supported by insulated levers, and flexible thrust connected on the one hand with the drums, and on the other hand - with the probe body.

The device consists of a ground part includes: a registration and control unit, an on-board computer, a current source, electrodes B and Nde., A connecting cable. The underground part of the device contains: an electronic unit 1, centering devices 2; a probe comprising a housing 3, current electrodes A1 and A2, measuring electrodes M1, M2, M3, ... Mn, electrically insulated levers 4; The clamping devices consist of springs 5, flexible rods 6, drums 18 with free-wheeling mechanisms 22 (see figure 2).

The current electrodes A1, A2 are located on the centering device 2.

The electronic unit 1 contains: a potential meter of the electric field of one of the measuring electrodes of the probe, a meter of potential differences of neighboring measuring electrodes, an electronic device for a telemetric system for transmitting data from the outputs of the meters and receiving control commands from the day surface. A current switch through which the current circuits of the electrodes A1 and A2 are switched.

The actuator 9 is placed in the lever 4, protected from the environment by a sealed enclosure, and contains: a motor driver with a communication modem 10, a connector 11 for electrical contacts of communication with an electronic unit 1, an electric motor 12 with an encoder, a gearbox 13, the output shaft 14 on which pin 15 is located , the Hall sensor 16 associated with the modem. The position of the actuator relative to the housing 3 of the probe is monitored by the Hall sensor 16. The actuator 9 can be rotated along with the lever 4 on the axis 17. Coaxially with the shaft 14, a drum 18 is installed with a flexible rod 6 wound around it. The free end of the thrust 6 is fixed to the screw 21 installed in the housing probe 3. The drum 18 is made the same as the lever 4 is made of durable insulating material, and is connected to the shaft 14 through a free wheeling mechanism 22. A gear wheel 23, which is the current electrode Mn, is connected to the shaft. A key 24 connects the shaft 14 with a free wheeling mechanism 22 and a gear wheel 23, which are fixed by a nut 25.

The disk in the form of a toothed wheel or wheel with an abrasive coating 23 (electrode Mn) is connected to the shaft 14 by flexible cable 26. The lever 4 is constantly pressed by the free end of the spring 5, the other end is fixed to the body 3 by the screw 27 and the bar 28. The force of the spring 5 is compensated by the tension of the flexible thrust 6. The free wheel mechanism 22 is engaged with the drum 18 and does not allow it to rotate.

On the surface there is an on-board computer, a power supply of current electrodes, a recording and control unit connected with a reverse current electrode B, an electrode Nud., And through a logging cable with a downhole probe of the device.

The device works as follows.

The contact of the measuring electrodes M1, M2, M3, ... Mn with the borehole wall is achieved as follows. Consider the duty cycle for the example of one electrode.

After the borehole probe is installed in the well at a predetermined interval, on command from the onboard computer via the electronic unit 1 (Fig. 1), the drive 9 is turned on. Shaft 14 begins to rotate together with the gear wheel 23, the free wheeling mechanism 22 comes out of engagement with the drum 18, flexible traction 6 begins to unwind. Under the influence of the spring 5 on the lever 4, the gear wheel 23 together with the lever 4 rotates around the axis 17 and begins to cut through the corrosion layer, to penetrate into the metal of the wall of the column. The pressing force and the geometry of the electrodes 23 in the device is calculated so as not to damage the column. In order to neutralize the reactive torque to the probe, the electrodes are rotated in pairs in different directions. After the drive is stopped and the electronics monitor the quality of the electrode clamp, the measurement mode begins. The measurement mode is performed using two cycles,

In the first measurement cycle (calibration), the current from the probe power supply is applied between the first A1 and the second A2 current electrodes. In this case, the current is measured, as well as all the necessary potentials on the measuring electrodes and the transfer of their values to the on-board computer.

In the second cycle (measuring), the current from the power source is supplied to one of the current electrodes A1 or A2 relative to electrode B. The current values and all the necessary potentials of the measuring electrodes M1, M2, M3, ... Mn are transmitted to the on-board computer. Then, based on the measured values of the currents, the potential of one of the electrodes relative to Nud. and the potential difference between the measuring electrodes in two cycles, the on-board computer calculates the values of electrical resistivity. After that, the on-board computer sends the command to fold the clamping devices into the transport position.

Consider the operation of folding in the transport position of the measuring electrodes on the example of one electrode (Fig. 2). The shaft 14 begins to rotate in the opposite direction as compared with the cutting-in mode of the electrodes, the free-wheeling mechanism 18 engages with the drum 22. Flexible thrust 6 begins to be wound on the drum 22. The lever 4 together with the drive 9 and the electrode 23 rotate around the axis 17 and return to the original the position that is monitored by the actuation of the Hall sensor 16 when it is combined with the magnet 29 (see also figure 1), mounted in the body of the probe 3. After that, the drive is turned off, the free-running mechanism 22 fixes the drum 18 from turning, devices o ready to move to the next measurement point.

To reduce the total reactive moment on the probe, in order to increase the stability of the device, to reduce the likelihood of contact loss during the operation of introducing electrodes, a variant of the design shown in figure 3 is proposed. Instead of electrode disks, electrode 34 is put in the form of a drill. The design has a housing 30, which is rigidly attached to the housing of the actuator 9 by means of a thread and a screw 31. The drill 34 is mounted on the support 32. Rotation to the drill 34 is transmitted from the shaft 14 through a flexible shaft 33, which is a continuation of the shaft 14. This design allows the use of drills with a small diameter, which reduces energy costs and reactive torque during cutting. Since the plane of rotation of the drill 34 is rotated along the axis of the well, the reactive total moment arising from the rotation of the measuring electrodes in this plane will be easily balanced due to the considerable length of the device and the small diameter of the drill.

5. An example of a specific implementation

As the bench tests of the model of the clamping unit showed, when the electrode rotates at a speed of 2-4 revolutions per second and a spring pressure of 1-2 kg, the metal surface is covered with corrosion and the 7 mm layer of cement is inserted into a reliable contact in 3-4 seconds, which is much faster than happens in known devices.

The design of the device with a high degree of unification, which simplifies its assembly and debugging. It does not require high power engines, it does not use high forces and torques, which leads to rapid wear of parts in the prototype device, there are few moving elements rubbing in an abrasive environment. Since the power elements of the device, such as a gear motor, a spring, are low-power and small-sized, there are no particular problems to realize a device in diameters less than 55 mm. The development of working drawings of the device with an outer diameter of Φ 54 mm has now been completed. The radius of the disclosure of these clamping devices allows you to work without interchangeable elements in wells with internal diameters from the minimum, limited to the probe's own diameter, up to 220 mm.

Claims (3)

1. An electric logging tool for cased wells, consisting of an electronic unit, centering devices, a probe containing pressure devices, electrodes sequentially arranged along the axis of the well, with current electrodes A1 and A2 located on centering devices, and equidistant measuring electrodes (M) are installed with the possibility of elastic clamping to the inner walls of the cased well by means of electrically insulated levers and clamping devices, ground-based current source for and electric current to current electrodes including through a reverse current electrode B, an electric field potential meter of one of the measuring electrodes relative to a remote electrode Nud, an electric field potential difference meter between adjacent measuring electrodes, a probe supply current meter, an on-board computer with a recording and control unit for controlling the processes during logging and calculation based on the obtained data on the electrical resistivity of rocks, different t m, that the measuring electrodes (M) are equipped with hermetic drives with output shafts (14) and electrical contacts (15) on the output shafts and are made in the form of cutting or abrasive tools (23), with the drives installed in electrically insulated levers (4), and the measuring the electrodes (M) are connected to the output shafts of hermetic drives, which transmit the electrodes rotation. 2. The device for electrical logging of cased wells under item 1, characterized in that the axis of rotation of the electrodes are rotated at an angle relative to the axis of the well, and the output shafts are connected to the measuring electrodes by a flexible coupling. 3. The device for electrical logging of cased wells according to claim 1, characterized in that the clamping devices are drums equipped with free-wheeling mechanisms, springs and flexible rods, the drums being coaxial with the output shafts of the drives, connected to them via free-wheeling mechanisms and electrically isolated from the springs with their free ends rested elastically on the insulated levers, and the flexible rods are connected on one side to the drums, and on the other hand are connected to the probe body.

Images