WO2008024035A2

WO2008024035A2 - Device for acoustic action on paraffin deposits in oil-well tubing (owt) in oil wells

Info

Publication number: WO2008024035A2
Application number: PCT/RU2007/000461
Authority: WO
Inventors: Dmitry Pavlovich Frolov
Original assignee: 'arter Technology Limited'
Priority date: 2006-08-25
Filing date: 2007-08-24
Publication date: 2008-02-28
Also published as: WO2008024035A3

Abstract

The device relates to oil production and can be used to intensify oil recovery by using acoustic action to destroy paraffin, asphaltic tar and hydrate glacial formed in the oil wells. The device can be useful in the oil wells equipped both will bottom-hole pumps (BHP) and electric pumps. The device is designed as a module structurally combined with the string of oil- well tubing being made integral with it. The sound emitting device is installed in the string at a definite depth in the zone of presumed paraffin and other deposits. If it is required to treat a long OWT portion or several spaced apart portions, several sound emitting devices can be installed that are excited electrically with the sound frequency voltage. The technical result of the claimed invention is the convenient in operation design that ensures intensification of the acoustic effect on the OWT walls and the oil-bearing fluid inside the OWT in any area of the oil-well tubing string. The technical result is achieved because the device has an acoustic radiator of the assembled type consisting of a piezoceramic cylinder mechanically linked to the end surfaces of the active and passive overlay pieces, two connecting pipes and a protecting body, the active overlay piece being made with cylindrical internally threaded from both ends hollow coupling made according to the GOST for OWT couplings, connecting externally threaded from both ends pipes made according to the GOST for OWT pipes, the length of each connecting pipe being selected equal to the whole number of half- waves of longitudinal vibrations in the pipe material at the working frequency of the radiator, one threaded coupling linking mechanically the connecting pipes to the active overlay piece, the other threaded coupling linking mechanically to the couplings of the oil-well tubing string.

Description

DEVICE FOR ACOUSTIC ACTION ON PARAFFIN DEPOSITS IN OIL-WELL

TUBING (OWT) IN OIL WELLS

The device relates to oil production and can be used to intensify oil recovery by using acoustic action to destroy paraffin, asphaltic tar and hydrate glacial formed in the oil wells. The device can be useful in the oil wells equipped both will bottom-hole pumps (BHP) and electric pumps.

The device is designed as a module structurally combined with the string of oil- well tubing being made integral with it. The sound emitting device is installed in the string at a definite depth in the zone of presumed paraffin and other deposits. If it is required to treat a long OWT portion or several spaced apart portions, several sound emitting devices can be installed that are excited electrically with the sound frequency voltage.

There are various device affecting the oil bearing fluid in the OWT mechanically during oil production; they are patents RU 217137, RU 100571, RU 93019124, RU 2148151, RU 2137908. The devices and methods they describe have different designs and principles of application.

The method proposed in patents RU 2100571 and RU 2106480 implies placement of a source of mechanical vibration on the OWT without specifying the principles of the design. Another embodiment of the device is proposed in patent RU 2106480 that is capable to excite radial and radial-bending resonance vibrations in the OWT. As a matter of principle, these proposals do not cause objections, but their practical implementation is ambiguous and is not discussed.

The design proposed in patents RU 2148151, RU 2137908 has the technical essence and achievable result to the claimed invention. Both the devices are intended to operate in oil wells equipped with the BHP and cannot be used in oil wells equipped with electrical pumps. The ultrasonic radiator of acoustic vibrations is suspended on the rod of a subsurface pump above the wellhead, acoustic vibrations in patent RU 2148151 are excited at an angle 0° - 60° to the rod axis apparently to achieve several different modes of vibrations. The patent mentions longitudinal and transverse vibrations, though there can be torsional vibrations too. Patent RU 2137908 proposes also an acoustic radiator attached to the end of the stem or to its lateral surface. This patent presents in detail the design of mechanical units carrying the radiator.

Both these designs have two main substantial disadvantages: They can be used only in the oil wells with BHP.

Acoustic vibrations propagate along the rod from the top attenuating as the rod descends deeper. Their effect on paraffin and other deposits seems very week or ineffective in deep oil wells.

To eliminate these shortcomings the acoustic radiator should be mounted oh the OWT and as close as possible to the area of deposits to be destroyed. Low frequencies and resonance phenomena of both the radiator and the relevant structural elements are needed to 10 intensify the vibrations

The technical result of the claimed invention is the convenient in operation design that ensures intensification of the acoustic effect on the OWT walls and the oil-bearing fluid inside the OWT in any area of the oil-well tubing string.

The technical result is achieved because the device has the acoustic radiator of the

15 assembled type consisting of a piezoceramic or magnetostriction cylinder with its end attached to the active metallic overlay piece internally threaded from both ends, two connecting pipes having standard threading from both ends to connect the active overlay piece with the couplings of the OWT string of the used diameter through which the acoustic energy is delivered from the active overlay piece to the OWT string, a metallic cylindrical passive

20 overlay piece that is connected mechanically to the second end of the acoustic transducers and acoustically insulated from the connecting pipe, a protective body

The connecting pipes are coupled to the oil-well tubing arranged from both sides of the radiator making up an integral string. Pieces of OWT pipes with the diameter of the used string are preferably to use as connecting pipes. This design of the radiator maintains

25 the strength of the OWT string. A standard coupling with standard threading is preferably used as the active piece.

The proposed device has the following resonating elements: An assembled acoustic radiator

Connecting pipes mechanically linked with the active radiator overlay piece or a

30 standard coupling. The length of each pipe is selected proceeding from the condition that it is equal to the whole number of half-waves of longitudinal vibrations at the working frequency of the radiator, it is due to the fact that different cross sections of the coupling and OWT pipes (their impedances differ) away from the points of connection of the couplings with the pipes cause reflection of the waves, hence the vibrations induced by the radiator in the OWT and the arriving wave reflected by the coupling should be synchronized, i.e. the radiator should be matched to the medium of propagation of acoustic vibrations.

The Figures disclose the principle of the invention.

Fig. 1 is a schematic presentation of the proposed device. The device includes an acoustic radiator of the assembled type comprising of active piezoceramic or magnetostriction cylinder 1 , active overlay piece and connecting coupling 2, passive cylindrical overlay piece3, protective body 4 and two connecting OWT pipes 5 and 6, attached to the coupling from each side.

Power supply cable 7 is connected through passive overlay piece to active piezoceramic or magnetostriction cylinder with air-tight connector 8. Rings 9 and 10 ensure mechanical isolation from the connecting pipe. If it is necessary to reduce the working frequency of the radiator the passive cylindrical overlay piece can be replaced with a quarter-wave sleeve or connected to the side opposite to the active cylinder.

A low resonance frequency of the radiator I achieved by a considerable weight of the overlay pieces. The lower is the frequency the smaller is the attenuation acoustic waves in the pipes and the higher is the amplitude of vibratory displacements. Hence the zone of action on paraffins and other deposits is expanded.

Figures from 10 to 14 in Fig. 1 designate the parts from the bottom and the top of the oil-well tubing string connected with the acoustic radiator.

Because the acoustic radiator is integral with the OWT string, when the zone of paraffin deposition is long or there are several such zone, several radiators are mounted on the oil-well tubing string at a selected interval one from another and electrical outputs are connected parallel.

The device operates in the following manner. When assembling the string, the lower end of device 5 on the surface is secured with an OWT tightening wrench with coupling 1 1 t o the OWT string lowered into borehole 15. The power cable is connected to the radiator and it is lowered into the borehole. Coupling 12 is secured to the free end of second connecting pipe 6 radiators and it is connected to next OWT pipe 13. Then the entire OWT pipe string is gradually added and lowered into the borehole. Positioning of the radiating device in the oil-well tubing string is determined based on the location of most intensive paraffin and other depositions. The exciting voltage of resonance frequency is supplied to the radiator via the cable. Acoustic vibrations appear in the OWT pipes and oil-containing fluid affecting paraffin and other deposits. .

Claims

1. A device for affecting acoustically paraffin deposits on the oil-well tubing walls in producing including an acoustic radiator of the assembled type comprising a piezoceramic cylinder mechanically connected to the end surfaces of active and passive metallic overlay pieces, two connecting pipes and protective body different in that the said active overlay piece being made as a cylindrical hollow coupling according to the GOST for OWT couplings internally threaded from both ends, the said connecting pipes being externally threaded according to the GOST for OWT pipes, the length of each said connecting pipe being selected equal to the whole number of half- waves of longitudinal vibrations in the pipe material at the working frequency of the radiator , and the connecting pipes being mechanically linked with the threaded coupling to the active overlay piece and with other threaded coupling being mechanically linked to the oil-well tubing pipe string, and the passive overlay piece being acoustically isolated from the connecting pipe.

2. The device according to claim 1 distinct by that that in order to intensify the acoustic vibrations the said passive overlay piece being mechanically linked to the follow quarter-wave metallic cylinder.