RU2390802C1 - Borehole implosive source of seismic vibrations - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: disclosed here borehole source of seismic pulses consists of case, of cable electric input, of motor-reducer, of force exciter in form of chamber with openings in case, and of differential piston with reciprocating plunger. Also an internal cavity of the case, wherein a packed plunger enters, is filled with oil and closed with a shank end on top, while in an internal partition of the piston there are made draining axial apertures; a reciprocating slider is mounted on the shank end and the case; the said slider is made in form of a double-step bushing. The cavity formed with a slider, the shank end and the case is filled with oil and connected with the internal cavity of the case via radial apertures in the shank end; a head is rigidly fixed to the slider on top; on external surface of the head there is made a chute wherein rollers secured in a rotary case roll. The head is conjugated with a core along a movable spline connection; the core is rigidly attached to the shaft of a motor-reducer with a key. In the lower section the chamber is connected with a receiver via a coupling; a spring loaded gate is installed in the coupling; in its lowermost position the gate closes axial apertures in the coupling connecting the chamber and the receiver. Also a draining opening is made in the connecting coupling.

EFFECT: facilitating maximal power of seismic pulse with automatic closing of aperture and during preparation to successive start; also simplification of design of source and its control.

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Description

The essence of the invention.

Usage: to excite seismic waves from wells.

The source contains a cable electric input, a starting mechanism, a drive gear motor, a working chamber and a receiver under atmospheric pressure. The chamber in the upper part has a series of radial windows that are overlapped by a differential piston with the possibility of reciprocating motion. The camera and receiver are connected by a clutch in which a spring-loaded shutter is installed, with the possibility of closing the holes connecting the camera and receiver. The trigger is made in the form of a hydraulic suspension, in which the pressure created by the weight of the source holds the plunger of the differential piston in the position in which the windows are closed. Also, the trigger mechanism has a rotatable housing, rigidly connected to the housing of the motor gearbox and with the cargo cable, and a core rigidly mounted on the gearbox shaft. A hydraulic suspension head is mounted on the core via a movable spline connection. Inside the rotary housing, rollers are installed, which roll along the gutter made in the head of the hydraulic suspension. The shape of the gutter provides a half turn of the head lift to the desired height of the source and then its free fall to the same height relative to the rotary housing.

Technical result: achieving maximum seismic pulse power during the automatic process of closing windows and preparing for the next launch while simplifying the design of the source and its control.

Description of the invention.

The present invention relates to devices for exciting seismic waves from wells.

Known downhole source, patent of the Russian Federation No. 2166779 dated 05/10/2001 (Patent classes: G01V 1/135, G01V 1/52), selected for the prototype, comprising a housing, a cable electrical input, a controlled wedge clamp, a drive motor and a power exciter, which is made in in the form of a camera with windows in the housing that overlap by means of an annular shutter and is equipped with a reciprocating piston, the piston displacement drive being made as a lead screw connected through a gearbox and a controllable coupling to the motor shaft; the housing is located in the lower part of the chamber, and the shutter, preloaded by a spring, is fixed by a latch mating with the anchor of the trigger electromagnet, and a gas cavity is placed above the piston from the side opposite to the working chamber. This is a very complex mechanical device that uses an electric motor, a gearbox, a controlled two-position clutch, an electromagnetic way of turning the source on. To work with such a source, you must have a complex control unit. Such a unit has a high cost and is difficult to maintain.

The objective of the invention is to achieve maximum power of the seismic pulse while simplifying the design of the source and its control.

A positive result is achieved by the fact that the inlet windows located in the upper part of the chamber are blocked by a differential reciprocating piston, and the piston is driven by a hydraulic suspension, the pressure of which is created by the weight of the emitter; the camera in the lower part is connected to the receiver by means of a sleeve, inside of which a shutter spring-loaded with a reciprocating movement is installed with the possibility of blocking the holes connecting the camera and the receiver, which are under atmospheric pressure; the hydraulic suspension, filled with oil, is made in the form of a piston-shank covering the cavity, which includes the power plunger of the differential piston, and a sealed slider rigidly fixed to the rotary housing of the trigger mechanism and freely moving along the piston-shank and the housing; the trigger mechanism has a rotary housing rigidly connected to the motor gear housing and a cargo cable and a core rigidly mounted on a key on the gear shaft; the head of the hydraulic suspension slider is mounted on the core via a movable splined joint; rollers are mounted inside the housing of the rotary device, which roll along the groove made in the head of the slider of the hydraulic suspension, and the shape of the groove provides half the turn of the head to raise the source to the required height and then fall freely to the same height relative to the rotary body.

The high hydrostatic pressure present in the well at great depths, due to its difference with the atmospheric pressure in the chamber and receiver, creates a force on the differential piston, which moves the piston to the upper position at which the windows are open. The pressure inside the hydraulic suspension created by the weight of the source creates a force in the opposite direction on the plunger and on the differential piston and is greater in magnitude than the force from the gyrostatic pressure. While the weight of the emitter is perceived by the hydraulic suspension, the differential piston blocks the entrance windows in the chamber. At the moment when the source freely falls along the vertical trough of the head of the slider, the differential piston opens the chamber windows, and the borehole fluid rushes into the chamber with high speed, creating a force on the piston, the magnitude of which exceeds the force from the pressure in the oil cavity, since it is created fluid pressure over the entire area of the piston (with the windows closed, this force was created on the area of the plunger and the difference in the area of the skirts of the differential piston). This force will keep the differential piston in its highest position until the shock pressure of the fluid that has encountered the shutter, having rolled several times from the shutter to the windows and back, does not completely disappear. The speed of the shock wave C _shock will be determined by the elasticity of the pipe and fluid. The stiffer the pipe and fluid, the higher the speed.

I.E. Zhukovsky obtained a formula for calculating the magnitude of the velocity of propagation of a shock wave in a dead end pipeline.

where E _W and E are the elastic moduli of the liquid and pipe walls, respectively;

d is the pipe diameter;

t is the wall thickness of the pipe;

ρ is the density of the liquid.

The speed of propagation of a shock wave in a real chamber C _shock = 1 / [ρ / Е _ж + ρd / (tE)] ^0.5 = 423.4 m / s

where E _W = 2.06 · 10 ⁸ Pa, d = 0.1397 m, t = 0.0092 m, E = 2.1 · 10 ¹⁰ Pa, ρ = 1000 kg / m ³ .

v = φ [(R _bore -R _to )] 2 / ρ] ^0.5 = 0.8 [(30-0.1)] · 10 ⁶ · 2 · / 1000] ^0.5 = 196 m / s - fluid velocity when filling the chamber at a depth of 3000 m (P _well = 30 MPa).

The magnitude of the shock pressure for a given depth and this particular chamber will be

P _shock = vρС _shock = 196 · 1000 · 423.4 = 83000000 Pa = 83 MPa.

For example, the filling time of this 20 l chamber will be

t _cam = V / (v · F) = 0.02 / (196 · 0.01155) = 0.0088 s,

where V = 0.02 m ³ is the volume of the working chamber, F = 0.01155 m ² is the area of the inlet windows equal to the area of the internal cross section of the chamber with an inner diameter of 121 mm.

The opening time of the windows will be t _ok = (2N _ok / w) ^0.5 = (2 · 0.08 · / 500) ^0.5 = 0.018 s, where N _ok = 0.08 m is the piston mileage, w = N / m = 6000/12 = 500 m / s ² - piston acceleration with mass m = 12 kg and force N = 6000 H.

The pressure equalization time in the chamber with the borehole pressure takes about 4 strokes of the shock wave from the gate to the windows and back, and then will be t _yd = 8L / C _yadap = 8 · 1.6 / 423.4 = 0.003 s, where L = 1, 6 m - the height of the chamber is 20 l.

The free fall time of the device will be t = (2H / g) ^0.5 = (2 · 0.12 / 9.81) ^0.5 = 0.16 s at H = 0.12 m - the height of the vertical groove.

The process of filling the chamber and the time of radiation of the shock wave fits freely during the free fall of the source. Even with the intentional use of additional hydraulic resistances in the hydraulic suspension to reduce the speeds of the moving parts, the open position of the windows will be ensured by the process of high-speed filling of the chamber. The windows will begin to close only after filling the chamber and equalizing the pressure inside it with the borehole pressure. As soon as the source flies through the groove height or the pressure in the chamber is equal to the pressure in the well, its weight will create pressure in the hydraulic suspension, which will shift the differential piston down and close the windows. The pressure in the chamber and receiver will be equalized through the drainage hole in the coupling, the spring will lift the shutter and open the main holes in the coupling, through which fluid from the chamber will flow into the receiver. The emitter is ready for the next start. To start the emitter, you only need to apply voltage to the gear motor. Opening windows and all other processes for preparing it for the next launch occur automatically. This device is many times simpler in its design and in managing the start-up and preparation for the next start-up in comparison with the known analogues.

A hydraulic shock wave in the device is emitted by the camera during the free fall of the device, that is, its power pulses (for the internal diameter of the chamber 120 mm at a depth of 3000 m - this is about 55 tons) do not affect the load-carrying cable. Therefore, its strength characteristics should provide only the weight of the device. This design provides the same high signal characteristics without additional devices, without additional hardening of the cargo cable or nodes fixing the source in the well in comparison with the known analogues.

The drawing shows a cross section of a borehole source. The borehole source of seismic pulses contains a housing 1, an electric input 2, further mated with a load-carrying cable. The cylindrical chamber 3 has in the upper part of the window 4 facing the well and hermetically sealed by a differential piston 5 with a plunger 6. The cylindrical chamber 3 is connected by a pipe 7 and a sleeve 8 to the receiver pipe 9, which is closed by a cover 10 from the bottom. In the sleeve 8, the camera is installed on the camera side a shutter 11 held by the spring 12 in a position where the openings 13 are open; also, a drainage hole 14 is made in the coupling. The internal cavity of the housing 1 is closed from above by the shank 15 with radial holes 16 connecting the cavity 17 with the cavity formed by the housing 1, the slider 18 and the shank 15; the mating surfaces of the slider 18, the shank 15 and the housing 1 are hermetically sealed; the cavity 17 and the cavity formed by the housing 1, the slider 18 and the shank 15 are filled with oil. The head 19 is rigidly attached to the slider 18 from above, which is coupled to the core 20 via a movable splined connection. which roll along the groove 24, made on the outer surface of the head 19. The shape of the groove at half the turn of the core 20 provides a slow vertical movement of the head 19 upward relative to the rotary Pusa 22 and then freefall tip 19 together with the lower part of the source down the vertical groove 26.

In the initial state, as shown in the drawing, the internal cavities of the chamber and receiver are free of well fluid and are at atmospheric pressure, windows 4 are hermetically closed. The piston 5 with the plunger 6 by the combined action of hydrostatic pressure and oil pressure in the cavity 17 is pressed against the inner shoulder of the cylindrical chamber 3, formed by the transition of a larger groove into a smaller groove. The source hangs on a load-carrying cable, its weight is perceived by pressure in the oil cavity 17, the pressure is created by the annular area along the inner diameters of the movable tight joints of the slider 18, the shank 15 and the housing 1. This pressure creates a downward force on the plunger 6. It is more than the force from hydrostatic pressure along the annular area along the inner diameters of the movable tight joints of the piston 5 and the cylindrical chamber 3. The shutter 11 is raised by the spring 12 above the openings 13, and the internal cavities of the chamber and the receiver are interconnected. The rollers 23 are in the position before rolling them into the groove 26, when the head 19 together with the source is maximally raised by mutual rotation of the head 19 and the rotary housing 22 by the gear motor 21, to which voltage is applied. With further mutual rotation of the head 19 and the rotary housing 22, the rollers 23 will fall into the vertical grooves 26, and the head with the source will begin to fall down freely. The geared motor will automatically turn off with a sensor that senses the loss of weight in the load-carrying cable. The oil pressure in the cavity 17, created earlier by the weight of the device, will disappear, and the piston 5 will begin to move upward under the action of hydrostatic forces, opening the windows 4. The more windows 4 open, the greater the force will push the piston 5 upward. This force is an order of magnitude greater than the force from the pressure in the oil cavity, since it is created by the pressure of the liquid over the entire area of the piston (with closed windows, this force was created on the area of the plunger and the difference in the area of the skirts of the differential piston). The upward movement of the piston 5 will stop when it abuts against the upper bottom of the housing 1. The fluid from the well under hydrostatic pressure will rush through the windows into the chamber, while accelerating. When a column of liquid flying in the chamber hits the shutter and stops with it, the kinetic energy of the column of flying liquid will be converted into pressure energy, which will travel through the walls of the chamber and along the liquid in the opposite direction, emitting seismic waves into the borehole space. Fluctuations in the walls of the chamber will gradually calm down, and the pressure in the chamber will equal the borehole pressure. At this time, the head 19 will hang on the rollers 23 in its lowermost position, and the weight of the source will create pressure in the cavity 17, which will move the plunger 6 together with the piston 5 downward, displacing the liquid through the open windows 4, and when the windows are closed, through the drainage holes 14 and 27. As soon as the windows are completely closed and the pressure in the internal cavities is equalized through the drainage holes 14 and 27, the spring 12 will lift the shutter 11 and open the holes 13, through which the liquid from the chamber flows under its own weight and air rises. The source is ready for the next start-up, for the production of which it is only necessary to supply power to the gear motor.

Claims (1)

A downhole source of seismic pulses comprising a housing, a cable electric inlet, a geared motor, a power exciter in the form of a chamber with windows in the housing, characterized in that the windows located in the upper part of the chamber are overlapped by a differential piston with a reciprocating plunger, the inner cavity of the housing , where the sealed plunger enters, is filled with oil and closed with a shank on top, and axial drainage holes are made in the piston’s inner bore that connect the cavity above the piston with the cavity under Orshny; a slider mounted on the shank and body with the possibility of reciprocating movement, made in the form of a two-stage sleeve, a large diameter hole of which is sealed by the outer diameter of the shank, and a smaller diameter hole is sealed by the upper cylindrical part of the body; the cavity formed by the slider, the shank and the housing is filled with oil and connected to the internal cavity of the housing through radial holes in the shank; the head is rigidly attached to the slider from above, on the outer surface of which a groove is made, on which the rollers are mounted, mounted in the rotary body, and the shape of the groove at half the turn of the head ensures a slow vertical movement of the head upward relative to the rotary body and then the head falls free together with the bottom of the source down a vertical groove; the head on the movable spline connection is paired with a core, which is rigidly mounted on the key on the shaft of the gear motor; the gear motor is rigidly fixed to the rotary housing, to which the load-carrying cable is attached, the camera in the lower part is connected to the receiver through the coupling, and a spring-loaded shutter is installed in the coupling with the ability to block axial holes in the coupling connecting the camera and receiver in its extreme lower position, also a drainage hole is made in the coupling.