RU2244946C1 - Well acoustic emitter - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: device has set of coaxially placed piezoceramic converters, connected to each other through mounting parts and fixed together by centering rod, pressurizing elastic cover with two end lids, filled with electro-isolating liquid. Each piezoceramic converter has shape of correct straight polyhedral prism, sides of which are made in form of piezoceramic plates. Connection of piezoceramic plates to mounting part is made with possible realization by piezoceramic plates of resilient transverse oscillations. Inner volumes of piezoceramic converters and volume, formed by their outer surface and elastic cover, have hydrodynamic connection.

EFFECT: higher efficiency.

3 cl, 8 dwg

Description

The invention relates to devices for acoustic impact on reservoirs, including for the intensification of oil, water and other fluids from wells.

Currently, acoustic effects on productive formations from wells are performed in the frequency range from units of hertz to tens of kilohertz. In this case, the lower frequency range up to one kilohertz and the upper one, starting from ten kilohertz and above, have been practically mastered. For exposure in the lower frequency range, a number of instruments are known, mainly hydrodynamic, which create a pressure amplitude of up to 2 MPa and give a positive effect of increasing the flow rate of the well (V.P. Dyblenko, R.N. Kamalov, R.Ya. Sharifullin, I .A. Tufanov "Increasing productivity and resuscitation of wells", M. Nedra, 2000, pp. 197-198). The disadvantage of hydrodynamic emitters is that at higher frequencies their development is very difficult due to the physical principles of their work. In addition, the service life of such emitters does not exceed several hundred hours.

Known effective piezoceramic emitter, using the principle of resonant oscillations in piezoceramic rings and rods, operating at frequencies of more than 10 kilohertz (RU No. 2047280, 1994). Compared with hydrodynamic emitters, it develops less pressure on its surface.

In addition, a major advantage of piezoceramic emitters compared to hydrodynamic ones is their high reliability (more than 95%) and a long resource of active work (more than 2000 hours).

However, using the well-known constructive solution for operating at frequencies of 1-10 kHz is inefficient, since the resonant diameter of the cylindrical emitter will be more than 150 mm, which exceeds the overall dimensions of the well, and the resonant length of one core module is more than 200 mm, which does not provide continuous irradiation with the thickness of the reservoir. When operating at frequencies below the resonance of piezoceramic rings and rods, their mechanical resistance increases significantly. At the same time, acoustic power and efficiency are reduced several times.

The closest in technical essence to the proposed technical solution is a downhole acoustic emitter in the form of piezoceramic rings dialed into a column, connected electrically in parallel. The rings are mounted on special dividing bushes strung on a central metal rod, which is the frame of the emitter. At the ends, the emitter is closed with metal covers. The piezoceramic ring itself is glued from prismatic piezoelectric elements, on the side faces of which electrodes are deposited by burning silver, while the piezoelectric elements are pre-polarized in the direction perpendicular to the faces with the electrodes. The piezoelectric elements in the ring are electrically connected in parallel, i.e. in all piezoelectric elements, the polarization vector is parallel to the direction of the applied electric field. As a result, under the action of an alternating electric voltage supplied to the electrodes of the piezoelectric elements, the rings make pulsating oscillations. For sealing from the external environment, the side surface of the emitter is closed with a rubber cover hermetically fastened to the end caps. The internal volume is filled with insulating fluid. The outer surface of the cover is protected from mechanical damage by a perforated metal casing. The emitter itself is mechanically connected to other functional blocks that form a whole downhole acoustic radiation instrument, which is connected to the ground power and control equipment through a geophysical load-bearing electric cable (Utility Model of the Russian Federation No. 762, 1994).

The main disadvantage of the known emitter is its low efficiency when operating in the medium frequency range of 1-10 kHz. This is because the existing well diameters do not allow the use of cylindrical emitters at their resonant frequencies, since the resonant size of the emitter is larger than the well size. The operation of the emitter out of resonance is ineffective.

The problem to which the invention is directed is to create a borehole acoustic emitter that effectively operates in the medium frequency range (1-10 kHz), i.e. having a frequency of mechanical resonance in this frequency range.

The technical result is to reduce the resonant frequency of the downhole acoustic emitter without increasing its size and ensuring its high efficiency.

The technical result is achieved due to the fact that the downhole acoustic emitter contains a set of coaxially arranged piezoceramic transducers, interconnected through mounting parts and fastened by a centering rod, a sealing elastic casing with two end caps, filled with an insulating fluid. Each piezoceramic transducer has the shape of a regular straight multifaceted prism, the edges of which are made in the form of piezoceramic plates. The connection of the piezoceramic plates with the mounting parts is made with the possibility of the implementation of the piezoceramic plates of elastic transverse vibrations. The internal volumes of piezoelectric transducers and the volume formed by their outer surface and elastic casing have a hydrodynamic connection.

In a preferred embodiment, the connection of the piezoceramic plates with the mounting parts is made according to the dovetail type.

Piezoceramic plates are arranged in height from prismatic piezoceramic elements of rectangular cross section.

By varying the length of the piezoelectric ceramic plates and their thickness, it is possible to achieve the required frequency of mechanical resonance, since the length and width of the plate are related for the following relationship, which is supported on two opposite edges of the plate (Reference "Strength, Stability, Oscillations", edited by I. A. Birger and I .G. Ponovko, t. 3, M., 1968):

where ƒ _p is the resonant frequency of the plate - Hz;

with _PL - the speed of longitudinal waves in the plate - m / s;

h _PL - plate thickness - m;

_пл - длина пластины (расстояние между опертыми краями) - м.

_pl - the length of the plate (the distance between the supported edges) - m.

This technical result is unattainable for cylindrical and rod transducers, since for the former, the resonant frequency is determined by their diameter, and for the latter, by the length.

The invention is illustrated graphic materials, where:

figure 1 schematically shows the design of a borehole acoustic emitter,

Figure 2 is a section along BB-1 Figure 1,

Figure 3 - design of the sealing plate,

Figure 4 - design of the mounting part,

Figure 5 is a section along bb In Figure 4,

6 is an example of a piezoceramic plate made of piezoceramic prisms,

Fig.7 is a side view of Fig.6,

Fig - piezoelectric prism.

In General, the acoustic downhole emitter is the following design (Figure 1). The downhole acoustic emitter includes piezoceramic transducers 1, each of which is a regular straight tetrahedral prism. The edges of the prism are made in the form of rectangular piezoceramic plates 2. The short edges of the plates 2 are inserted into the grooves of the mounting parts 3 located between the transducers 1, and at the extreme transducers the edges of the plates facing the ends of the emitter are inserted into the grooves of the mounting parts 3 aligned with the end caps 4 and 5. Installation parts 3 at the ends of the downhole acoustic transducer can be made and not combined with the end caps. In grooves, the edges of all piezoceramic plates 2 are fixed with glue. Installation parts 3 and covers 4 and 5 are made in the form of metal disks. The mounting parts 3 and the disk 4 have central holes through which the centering rod 6 passes. The parts 3 are fixed on the rod 6. The design of the mounting part 3 with the central and additional holes for the passage of wires and grooves 7 for fixing the piezoceramic plates is shown in Figs. 4-5 .

Piezoceramic plates 2 are installed so that between their inner vertical ribs there are gaps of ~ 2 mm. In these gaps, sealing plates 8 of polymer material are tightly inserted. A series of channels 9 in the plates 8 provides a hydrodynamic connection between the internal volume of the piezoceramic transducers 1 formed by the piezoceramic plates 2 and the external volume formed by the outer surface of the piezoceramic plates 2 and the sealing elastic casing 10.

The whole structure is tightened with a nut screwed on the centering rod 6 from the outside of the end cover 4. The nut is installed with a lock against self-unscrewing.

Elastic soundproof casing 10 is made of rubber or other polymeric material. The casing forms a cylindrical surface, the edges of the casing are hermetically connected to the side surfaces of the end caps 4 and 5 using glue and power bandages.

Electrical installation is as follows. All conclusions from the piezoceramic plates in each piezoceramic transducer 1 are connected electrically in parallel. Wires from each transducer 1 exit through holes in the mounting parts. The converters 1 are interconnected either in parallel or in parallel-series depending on the desired impedance of the emitter.

Piezoceramic plates performing bending vibrations during operation of the emitter can structurally be performed by various known methods. One of them is described below.

The piezoceramic plate 2 (Fig.6, 7) is glued from individual piezoceramic prisms 11 of rectangular cross section (Fig.8). The electrically conductive faces of adjacent prisms perpendicular to the radiating surface of the plate are glued to each other through conductive metal thin electrode plates. Curly metal prisms 12 are glued to the end piezoelectric elements of the plate, having a neck and a dovetail mount on the final side faces. Correspondingly, the grooves 7 in the mounting parts 3 have the corresponding shape. To ensure the mechanical strength of the piezoceramic plate during vibrations, it is pulled together with force along the plate alongside the plaits 13 of high-strength, usually polymeric threads, impregnated with a binder. The bundles 13 are located on the plate surfaces and pass through the grooves in the terminal metal prisms 12. Excitation of the bending vibrations of the plate is achieved by the fact that the conductive surfaces 14 of the piezoceramic prisms 11 (Fig. 8), previously polarized perpendicular to these surfaces, are separated by an insulating groove 15 along the length of the piezoceramic prism 11 (plate width 2), and the polarization vectors on each of the halves of the piezoceramic prism thus formed are mutually opposite in directions. All electrodes in the plate are electrically connected in parallel, and the plate thus has two leads.

The operation of a downhole acoustic emitter is as follows: a downhole acoustic emitter as part of a downhole tool is lowered into an oil well at the level of a reservoir on a KG-3 type geophysical cable. A probe signal is supplied from a ground generator through two cable cores through a cable lug to the input of the emitter. The electric voltage through the conductive metal plates glued between the piezoceramic prisms 11 falls on their electrically conductive faces. The direction of the polarization vectors along the thickness of the piezoelectric ceramic prism is chosen so that the outer part of the prism 11 (to the middle of its thickness) expands due to the piezoelectric effect, and the inner one contracts. As a result, the piezoelectric prisms 11 and, in general, all the plates 2 are bent, for example, to the outside. When the voltage sign changes, everything will happen the other way around. Since the edges of the plate are fixed motionless in the grooves of the mounting parts 3 (or covers 4 and 5), due to the described design of the end metal prisms of the plate, bending vibrations will approach, approaching in shape to the vibrations of the articulated supports. All plates in the emitter are switched in phase, so all plates are bent to one side, for example, to the external. When the voltage phase changes, the deflection will occur in the inner direction - towards the center of the emitter. On the whole, the oscillations that arise in the borehole space filled with fluid will be close to those generated by the emitter, drawn from coaxially located pulsating rings.

The frequency of the harmonic supply voltage is selected close to the frequency of the mechanical resonance of the piezoceramic plates.

The acoustic impact in the frequency range of 1-10 kHz on the productive oil reservoir allows you to excite noticeable fluctuations in it at a distance of several tens of meters from the well, while the acoustic impact at high frequencies does not penetrate more than 1 meter from the well. This circumstance allows you to get an additional productive effect when working in the mid-frequency range.

Claims (3)

1. A downhole acoustic emitter comprising a set of coaxially arranged piezoceramic transducers interconnected through mounting parts and fastened by a centering rod, a sealing elastic casing with two end caps, filled with an electrically insulating fluid, each piezoceramic transducer has the shape of a regular straight polyhedral prism, the edges of which are made in the form of piezoceramic plates, and the connection of piezoceramic plates with installation parts but with possibility of piezoceramic plates transverse elastic oscillations, with internal volumes of piezoceramic converters and the volume formed by their outer surface and the elastic casing are hydrodynamic bond. 2. The downhole acoustic emitter according to claim 1, characterized in that the connection of the piezoceramic plates with the mounting parts is made according to the dovetail type. 3. The downhole acoustic emitter according to claims 1 and 2, characterized in that the piezoceramic plates are mounted in height from prismatic piezoceramic elements of rectangular cross section.

Images