EA011048B1 - Device for hydrohydraulic treatment of formation - Google Patents

Abstract

The invention relates to the gas-and-oil producing industry, in particular, to high-voltage electrohydraulic devices for a stimulation of a wellbottom zone, for a formation of cracks in it, and for an increase of oil-and-gas recovery.Attainable technical result: increase of reliability, simplification of control, extension of the energy range and the technological enhancement of the device.Essence of invention: the proposed device comprises a tubular metal case 1 with a head 2 to attach a logging cable on one end and electric discharge chamber 3 on the other end, a step-up transformer 4, a high-voltage rectifier 5, a controlled switching unit 6 and a block of series-connected pulsed capacitors 7 located inside the case. The primary winding of the step-up transformer 4 is attached to the contacts of the head 2, one lead of the secondary winding of the transformer is attached to the high-voltage rectifier 5 and the other lead is attached to the case 1. Switching unit 6 is installed on the side of high-voltage rectifier 5 and is switched between the first lead of the block of capacitors 7 and case 1; the second lead of the block of capacitors 7 is attached to anode 9 of the discharge chamber directly and to case 1 through a resistor or a group of resistors 8. Cathode 11 of the discharge chamber is attached to case 1 through reflector 12 and ribs 13.

Description

FIELD OF THE INVENTION

The invention relates to the oil and gas industry, in particular to high-voltage electro-hydraulic devices for influencing the bottom-hole zone of a well and cleaning it from asphalt-resinous and paraffin deposits.

State of the art

A device is known for electro-hydraulic treatment of a formation and enhancement of its oil recovery (see US patent No. 4345650, NKl. 166-249, IPC E21 B 43/256, 1982), comprising a tubular metal housing with a cable adapter at one end and a rotary discharge head at the other end, and located in the tubular housing, a step-up transformer, a high-voltage rectifier, a capacitor bank and a controllable switch, while the charge and discharge control means are connected to the capacitor bank and a ground power source via a car the cable, the secondary winding of the transformer is connected to the rectification circuit, the output of the rectifier is connected to the potential output of the capacitor bank, the potential output of the capacitor battery is connected via a managed switch to the anode of the discharge head.

A capacitor bank includes a large number (approximately 1000) of parallel connected capacitors of high energy intensity (each, for example, with an operating voltage of 3 kV and a capacity of 100 μF). The switch is a standard ignitron. Ignitron ignition is carried out from a separate injector battery of 30 kV capacitors. The step-up transformer consists of a Sh-shaped core and primary and secondary windings. The discharge head consists of two electrodes with an adjustable gap. The discharge head is equipped with a rotary mechanism and a reflector for the concentration and direction of acoustic energy towards the producing well. All of the above components of the probe are located in the same compartment and are separated from each other by metal partitions.

The disadvantages of this device are the low (3 kV) operating voltage of the capacitor bank, which complicates the conditions for the formation of an electric discharge in the well fluid and requires the use of an additional injection (30 kV) capacitor bank;

low (less than 10%) electro-acoustic discharge efficiency, which requires the creation of cracks and cleaning the bottom-hole zone of the well from deposits of very large discharge current and energy consumption of the device (analogue energy consumption is approximately 450 kJ);

the inability to use the device in horizontal oil wells, due to the unstable position of the mercury cathode in the ignitron;

the difficulty of controlling an ignitron due to the need to lay a high-voltage ignition bus through a capacitor bank.

The closest in technical essence to the claimed invention is a device for electro-hydraulic treatment of the formation (see A.S. USSR No. 1058343, IPC E 21 B 43/26, authors P.P. Malyushevsky, ON N. Sizonenko and others, declare 06.06.81, publ. 07.10.91 B.I. No. 37), containing a power metal housing, with a transformer-rectifier unit, a pulse capacitor unit, a two-electrode switch, and a two-electrode discharge chamber.

The power enclosure is suspended on a cable cable (armored geophysical cable). The block of pulse capacitors consists of several series-connected high-voltage capacitors. The discharge chamber is made in communication with the well fluid.

One of the conclusions of the block of pulse capacitors is connected to the high-voltage output of the rectifier, the second terminal of the block of pulse capacitors is connected to the anode of the switch. The cathode of the switch, in turn, is connected to the anode, the rod electrode of the discharge chamber. The flat cathode of the discharge chamber is mounted on a metal base connected through stiffeners to the power housing.

The device also includes a gas pressurization system with elastic shells, tubes and an electromagnetic valve, which serve to limit the zone of action of the shock wave during an electric discharge.

After applying voltage via a cable, increasing and converting it in a rectifier transformer, charging a block of pulse capacitors and activating a switch between the electrodes of the discharge chamber, an electric discharge occurs. The resulting shock wave and high-speed hydraulic flow are concentrated between the elastic shells and destroy salt and paraffin deposits on the walls of the well. The disadvantages of the prototype are the often observed destruction of elastic shells when lowering the device into the well, due to friction of the shells on the wall of the well, as well as from the action of repeatedly repeated electrical discharges and shock effects when working in the well;

narrow energy range of the discharge and the shock wave, due to the presence of an uncontrolled switch (its fixed threshold);

low reliability, due to the possibility of the passage of the inverse surges of the discharge current of the capacitors (with the oscillatory nature of the discharge) through a high-voltage rectifier.

- 1 011048

SUMMARY OF THE INVENTION

The objective of the invention is to provide a device for electro-hydraulic treatment of the formation, adapted to work in all types of well fluids and chemicals and having a wide range of energy effects on the bottom-hole zone of the formation.

The technical result of the invention is to increase reliability and expand the scope of the device, namely:

a) the device is easily controlled from the surface of the earth;

b) during an electric discharge, the charging circuit of the device is bypassed and is not exposed to overvoltage and interference;

c) the operating voltage of the device and the energy release in the discharge channel are widely regulated and provides a different technological mode for cleaning the bottom-hole formation zone from asphalt-tar, salt and paraffin deposits;

d) an electric discharge and a shock wave are formed in any type of well fluid.

The specified technical result is achieved in the device for electro-hydraulic treatment of the formation, containing a tubular metal housing, at one end of which there is a head for connecting a geophysical cable, and at the other end is an electric discharge chamber, the cathode of which is connected to the housing, inside which there is a step-up transformer, a high-voltage rectifier , a block of series-connected pulse capacitors and a switch, while the conclusions of the primary winding of a step-up transformer connected to the contacts of the head, the secondary winding of the step-up transformer is connected by one output to the high-voltage rectifier, and the other output is connected to the housing, the output of the high-voltage rectifier is connected to the first output of the pulse capacitor unit, characterized in that one output of the switch is connected to the output of the high-voltage rectifier, and the other output switch - to the housing, the second output of the block of pulse capacitors is connected directly to the anode of the electric discharge chamber, at least one more is introduced a resistor, the first output of which is connected to the housing, and the second to the second output of the block of pulse capacitors.

In addition, the switch may be a three-electrode controlled arrester; high voltage rectifier diodes can be turned on so that the capacitor bank is charged with negative polarity voltage.

Switching on the switch between the output of the high-voltage rectifier (the first output of the block of pulse capacitors) and the housing of the device provides:

elimination of overvoltages at the output of the high-voltage rectifier during the reverse inrush currents of the capacitor block (during the oscillatory discharge mode), since the switch with a small direct resistance shunts the output of the rectifier;

simplified management and increased reliability of the device, since the launch (ignition) wire of the managed switch does not need to be pulled through the battery of high-voltage capacitors and insulated with almost double operating voltage, as in the analogue.

The implementation of the switch is three-electrode, i.e. controllable makes it possible to adjust over a wide range of the operating voltage of the pulsed capacitor block and the energy release in the discharge channel and, accordingly, the degree of impact on the bottom-hole zone of the reservoir without lifting the device to the surface. This is not in the prototype.

The connection of the second output of the block of pulse capacitors to the anode of the electric discharge chamber directly contributes to:

acceleration and improvement of the conditions for the formation of an electric discharge in non-watered oil (non-conductive) borehole fluids due to the flow of the charging current through the borehole fluid located between the anode and cathode of the electric discharge chamber;

reduction (by 20-30%) of energy losses at the pre-breakdown stage of electric discharge formation in flooded and mineralized (conductive) well fluids.

Connecting the second output of the block of pulse capacitors to the metal casing through a resistor or a group of resistors provides damping of high-frequency spurious oscillations and eliminates overvoltages on the insulation of pulse capacitors and the anode of the electric discharge chamber, and with small losses of energy on the resistors;

reduction and stabilization of the charge time of the block of pulse capacitors with a predominantly oil (non-conductive) composition of the well fluid.

Turning on the diodes of the high-voltage rectifier in the opposite direction provides a charge of the pulse capacitor block with negative polarity voltage, which, when the switch is turned on and discharged through resistors, is inverted to a positive voltage pulse at the anode of the electric discharge chamber, which is most optimal for the breakdown of flooded oils always present in production wells or industrial water which is often pumped into injection wells.

The drawing shows the inventive device for electro-hydraulic treatment of the reservoir (its

- 2 011048 longitudinal section).

Information confirming the possibility of carrying out the invention

The inventive device for electro-hydraulic treatment of the formation contains a tubular metal housing 1 with a head 2 for attaching a geophysical cable at one end and an electric discharge chamber 3 at the other end. Inside the metal case 1 there is a step-up transformer 4, a high-voltage rectifier 5, a switch 6, a block of high-voltage pulse capacitors 7 and a resistor or group of resistors 8.

The head 2 for connecting to the well-logging cable is three-pin (by two contacts - two wires of the cable, the primary winding of the step-up transformer 4 is supplied with voltage, by the third contact - the third wire of the cable - the command to turn on the switch).

The electric discharge chamber 3 has a central anode - a rod 9, an insulator - a fairing 10 and a cathode 11, installed with a gap of 20-30 mm relative to the anode 9 and connected through a conical reflector 12 and metal ribs 13 with the housing 1.

The secondary winding of the step-up transformer 4 is connected by one output to the high-voltage rectifier 5, and by the other output to the housing 1, the output of the high-voltage rectifier 5 is connected to the first output of the block of pulse capacitors 7.

The diodes of the high-voltage rectifier 5 are connected in the opposite direction and provide a charge of the pulse capacitor block with a voltage of negative polarity.

The block of pulse capacitors 7 is a group of six to seven series-connected high-voltage capacitors, each, for example, with an operating voltage of about 5 kV. The total operating voltage of the pulse capacitor unit is 30-35 kV, respectively.

The first output of the block of capacitors 7 is connected to the output of the high-voltage rectifier 5 and to the switch 6, the second output of the block of capacitors 7 is connected directly to the central electrode by the anode 9 of the electric discharge chamber and through resistors 8 to the housing 1. The resistance value of resistors 6 is 100-200 MΩ.

Switch 6 is connected to the output of the high-voltage rectifier 5 by one of the terminals and to the housing 1 by the other. Switch 6 is an uncontrolled gas-filled spark gap with a fixed operating voltage or a controlled three-electrode, for example, a vacuum spark gap with wide operating voltage ranges, for example, from 20 to 40 kV and switched energy, for example from 2 to 8 kJ.

The claimed device operates as follows. First, the device is lowered using a geophysical cable into the well to a predetermined depth (perforation interval). Then, an alternating supply voltage with an amplitude of 400-500 V and a frequency of 400-1000 Hz is supplied to it from the side of the cable elevator. In transformer 4, the supply voltage rises, for example, by 30 times, in rectifier 5, the voltage doubles and converts to a high constant voltage, which is characterized by a large amplitude of 30-35 kV and negative polarity. The block of pulse capacitors 7 is slowly charged with the indicated voltage. The charge current flows along the circuit: the secondary winding of the transformer 4, the rectifier 5, the block of pulse capacitors 7, the resistors 8 and the housing 1 and does not exceed 0.3-0.5 A at the peak. The voltage drop across the resistors 8 during the charge is small, respectively, and between the anode 9 and the cathode 11 of the electric discharge chamber, the voltage is also practically absent. After 3-5 s, the charge ends and the voltage across the capacitors 7 and the switch 6 reaches a predetermined level, for example, 30-35 kV. The gap of the gas-filled switch 6 is pierced and the voltage of the capacitors 7 is applied completely to the resistors 8 and to the gap between the anode 9 and the cathode 11 of the electric discharge chamber filled with the borehole fluid. This voltage now has a reverse positive polarity (convenient for the breakdown of flooded oils and industrial water), a large amplitude and a large discharge time constant. In the gap between the anode 9 and the cathode 11 of the chamber, a strong and inhomogeneous electric field is formed, leaders grow in the borehole fluid and after 5-10 μs a breakdown of the borehole fluid between the anode and cathode of the chamber occurs. Two parallel current branches are formed: one high-resistance - through resistors 8 and the second low-resistance - through the discharge channel in the liquid between the anode 9 and the cathode 11 of the chamber. Accordingly, the discharge current and the energy of the block of capacitors 7 are switched from the high-resistance resistive circuit to the low-resistance channel of the discharge in the liquid between the anode 9 and the cathode 11 of the chamber, while the amplitude of the current in the discharge channel increases sharply, the borehole fluid heats up and evaporates intensively, and the shock moves away from the discharge channel wave and high-speed hydroflow, which have a strong mechanical effect on the perforations in the casing and surrounding rocks. When the electro-hydraulic shock discharges are repeated and the device moves along the perforation interval, the perforations in the casing are cleaned from ASPO, and a network of new cracks is created in the bottomhole zone of the well and the old cracks are washed out. As a result, the flow rate of the oil well or the injectivity of the injection well increases.

Thus, the proposed device has the following advantages in comparison with the prototype:

simpler design, high reliability and controllability;

- 3 011048 the ability to control energy release in the channel of the discharge and the shock wave without lifting the device from the well;

favorable conditions for the formation of an electric discharge and shock wave in any type of well fluid.

Claims (4)

1. Device for electro-hydraulic treatment of the formation, containing a tubular metal housing, at one end of which there is a head for attaching a geophysical cable, at the other end is an electric discharge chamber, the cathode of which is connected to the housing, and a step-up transformer, a high-voltage rectifier, a block of series connected pulse capacitors and a switch, while the conclusions of the primary winding of the step-up transformer are connected to the contacts of the head, the secondary winding is increased the transformer is connected by one output to the input of the high-voltage rectifier, and the other output is connected to the housing, the output of the high-voltage rectifier is connected to the first output of the pulse capacitor unit, characterized in that one output of the switch is connected to the housing, and the other output of the switch is connected to the output of the high-voltage rectifier, the second the output of the block of pulse capacitors is connected directly to the anode of the electric discharge chamber, at least one resistor is introduced, the first output of which is connected to case, and the other with the second output of the block of pulse capacitors. 2. The device according to claim 1, characterized in that the switch is made in the form of a controlled three-electrode spark gap. 3. The device according to claim 2, characterized in that the switch is made in the form of a vacuum spark gap. 4. The device according to claim 1, characterized in that the diodes of the high-voltage rectifier are connected in the opposite direction and provide the charge of the block of pulse capacitors with a voltage of negative polarity.