WO2001017672A1

WO2001017672A1 - Apparatus including ultrasonic transducers for minimising the size of particles carried in a fluid medium

Info

Publication number: WO2001017672A1
Application number: PCT/GB2000/003163
Authority: WO
Inventors: Jeffrey Charles Edwards; Andrew Richards
Original assignee: Expro North Sea Limited
Priority date: 1999-09-07
Filing date: 2000-08-16
Publication date: 2001-03-15
Also published as: GB9920983D0; AU6584700A

Abstract

An improved ultrasonic processor is described for use in the offshore environment to minimise the size of drill cuttings. The processor comprises an outer transducer chamber which encloses an ultrasonic generating unit located between a top and bottom cap. The generating unit has internal and external cylindrical casings which form an annular cavity which is connected to both the inlet and outlet. A helical steel ribbon is located in the cavity and forms a path longer than its direct length from the inlet to the outlet for a fluid carrying drill cuttings. A plurality of sets of ultrasonic transducers are disposed around the processor may extend the length of the processor. The transducers are actuatable to generate acoustic energy in the cavity. The helical path increases the residence exposure time of the fluid with cuttings travelling through the processor, thus allowing the break up and de-agglomeration of the drill cuttings. Embodiments of the invention are described.

Description

APPARATUS INCLUDING ULTRASONIC TRANSDUCERS FOR MINIMISING THE SIZE OF PARΗCLES CARRIED IN A FLUID MEDIUM

This invention relates to the break up of particles. More particularly, this invention relates to an ultrasonic processor for minimising the size of drill cuttings for subsequent re-mjection into a formation or for other disposal .

In the oil industry it is known that ultrasonic waves are effective m reducing the particle size of drill cuttings carried by a fluid medium through a conduit which has an array of ultrasonic transducers disposed around its periphery and over its length for irradiating the fluid medium and cuttings. Reduction m particle s ze is required prior to disposal, for environmental reasons and for facilitating re- infection of the drill cuttings back into a porous formation. Drill cuttings are reduced m size by intense ultrasonic energy created by acoustic waves travelling through the fluid carrying the cuttings providing significant destructive forces on the particles. These destructive forces act upon the drill cuttings causing rapid size reduction by, for example, cavitation within the fluid. Following size reduction of the particles, the particles are separated from tne fluid dispersion and disposed of. As disposal, especially cuttings re-miection, is facilitated by small particles, it s highly desirable to minimise the size of drill cuttings m order to remove bound oil and minimise particle size.

However, problems exist with such existing ultrasonic processors. For example, existing ultrasonic processors do not consistently reduce the particle sizes to a level acceptable for disposal and they work better with certain types of cuttings In an attempt to overcome this problem, a number of these existing ultrasonic processors are used m series but th s requires a more expensive arrangement without providing much improvement n particle size reduction.

It is an object of at least one aspect of the present invention to obviate/mitigate one or more of the a orementioned disadvantages.

According to a first aspect of the present invention, there is provided apparatus for receiving a plurality of ultrasonic transducers to provide an ultrasonic processor for minimising the size of particles carried in a fluid medium, said apparatus comprising: a hollow chamber having at least one inlet and at least one outlet; and a member disposed within the chamber between the inlet and the outlet and forming a path length for the fluid medium between the inlet and the outlet longer than the direct distance between the inlet and the outlet .

Preferably, the hollow chamber and the member are generally cylindrical and define an annular cavity, and convoluted path means are disposed in said annular cavity for providing said path length. Alternatively, the hollow chamber and the member are non- cylindrical . Furthermore, the cavity between the hollow chamber and member varies in cross- section over the length of the member .

Preferably, the convoluted path is a flat ribbon arranged in a generally helical path between the outer surface of the member and the inner surface of the hollow chamber.

Advantageously, the ribbon is wound in a helical path from one end of the member to the other.

Advantageously, the helical wrap has a pitch which is uniform. Alternatively, the helical wrap has a pitch which is non-uniform.

Preferably, the ribbon has a plurality of small through holes . It is preferred that the small holes are of about 5mm in diameter. Alternatively, the small holes may have a plurality of diameters ranging from 2mm to 10mm.

Preferably, the member is a cylinder extending from one end of the chamber to the other. Preferably, the member is centrally mounted in the hollow chamber. Preferably, the hollow chamber is generally cylindrical shape.

Preferably, the ribbon is dimensioned and proportioned so that when disposed around the inner cylinder, the outer surface of the ribbon abuts the inner surface of the hollow chamber to seal against the passage of fluid between the edge of the ribbon and the inner surface. The ribbon is helically welded to the member. Alternatively, the ribbon may be fastened to the member by any other suitable fastening means, including brazing and screw fasteners .

In a further embodiment, the helical ribbon is formed by drilling a core from the top to the bottom through a large coil spring to create a spring bore, and then disposing the cylindrical member within the bore of the stretched spring. The helical ribbon has a pitch which is alterable by stretching or compressing the drilled spring. Conveniently, the cylindrical member is coupled to a drive means and is rotatable by said drive means about the longitudinal cylinder axis .

Conveniently, there is provided a plurality of ultrasonic transducers located longitudinally on the outer surface of the hollow chamber for transmitting high frequency sound. Alternatively, the transducers may be located within the cylindrical member. It is preferred that the ultrasonic emitters emit waves of a frequency range 40 -80kHz. In a preferred embodiment, the hollow chamber and cylindrical member are substantially vertical .

Preferably, the inlet is at the top of the hollow chamber and the outlet is at the bottom of the hollow chamber . Preferably, the hollow chamber, member and ultrasonic transducers are enclosed in a transducer protective chamber. It is further preferred that the member is about a lm long stainless steel tube of 8cms diameter and the hollow chamber has a length of about lm and a diameter of about 13cms. Preferably, the width of the helical ribbon wrap is about 2 5cms.

Preferably, the apparatus is used for minimising the size of drill cuttings.

According to a second aspect of the present invention, there is provided apparatus for use m minimising the size of particles carried in a fluid medium comprising. a hollow chamber having at least one inlet and at least one outlet, a member disposed within the chamber between the inlet and the outlet and forming a path length for the fluid medium between the inlet and the outlet longer than the direct distance between the inlet and the outlet, and a plurality of ultrasonic transducers disposed between the inlet and the outlet for irradiating particles carried in said fluid medium m same chamber with ultrasonic energy

Preferably, the hollow chamber and the member are generally cylindrical and define an annular cavity, and convoluted path means are disposed m said annular cavity for providing said path length Alternatively, the hollow chamber and the member are non- cylindrical and define an annular cavity, said convoluted path means are disposed m said annular cavity for providing said path length Furthermore, the cavity between the hollow chamber and member varies m cross -section over the length of the member

According to a third aspect of the present invention, there is provided a method for minimising the size of particles carried m a fluid medium passing through a hollow chamber having an inlet and an outlet, the method comprising the steps of irradiating the fluid medium and particles with ultrasonic radiation as the particles pass from the inlet to the outlet,- and guiding the fluid and particles to move between the inlet and outlet in a path longer than the direct path length between the inlet and the outlet so that the exposure time of the particles to ultrasonic radiation is increase .

Preferably, the method includes the step of guiding the fluid and drill cuttings to move in a helical path within an annulus .

Preferably also, the method includes the step of allowing some particles to bypass the helical path.

Preferably, the method includes the step of rotating the helical path. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view through an ultrasonic processor according to a first embodiment of the inven ion;

Fig. 2 is a top plan sectional view of the ultrasonic processor of Fig. 1 ;

Fig. 3 is a sectional view similar to that shown in Fig. 1 of an ultrasonic processor according to a second embodiment of the present invention, and

Fig. 4 is a top plan view of the ultrasonic processor of Fig. 3.

Figs . 5a to 5d are diagrammatic side views of an ultrasonic processor in accordance with a third, fourth, fifth and sixth embodiment of the present invention.

Referring to Figs. 1 and 2 of the drawings, there is illustrated an vertically oriented ultrasonic processor, generally indicated by numeral 10, which comprises a cylindrical transducer protective chamber 12 having a top cap 14 and a bottom cap 16 which receives a fluid inlet 18 and a fluid outlet 20 respectively. Disposed within chamber 12 is an ultrasonic generating unit, generally indicated by reference numeral 22, which extends between caps 14,16. The ultrasonic generating unit 22 has a tubular housing 24 and an inner cylindrical member 26 which defines an annular cavity 28 therebetween. A helical steel ribbon 30 is welded to the member 26 at a constant pitch. The inlet 18 and outlet 20 are in fluid communication with the annular cavity 28. As best seen in Fig. 2, five sets of piezoelectric crystal ultrasonic transducers 32 are disposed peripherally and longitudinally on the exterior of the tubular house 24. The transducers 32 are electrically connected in series and are powered by a generator and are controlled by a system control panel (not shown in the interest of clarity) . In the preferred arrangement shown, the processing unit is about lm long with a diameter of about 15cms. The inlet 14 and outlet 16 each have a diameter of about 5cms and the annular thickness is about 2.5cms.

In use, a fluid carrying drill cuttings forming a slurry is pumped into the inlet 18 and via gravity and the force of a pump (not shown) the slurry fills the annular cavity 28 and is guided along a helical path by the ribbon 30. The slurry enters the region opposite ultrasonic transducers 32 which are energised to resonate and emit ultrasonic waves up to 80kHz which are focussed so that the ultrasonic energy field is maximised in the annular cavity 28. The energy acts on the fluid and particles carried by the fluid and causes cavitation by the shear force applied to the particles. The fluid acts as the transfer medium for the drill cutting particles. As the ultrasonic waves enter the fluid they generate small bubbles that enlarge and then implode creating tremendous heat as localised "hot-spots" which rapidly dissipate while the surrounding areas remain close to ambient temperature. The imploding bubbles also generate high friction and collision forces which complement the size reduction process. The stress levels along with increased momentum imparted to drill cuttings results in the break up and de-agglomeration of solid components such as drill cuttings carried in the liquid medium. After the ultrasonic treatment, the particles are reduced in size to about 50 microns when exiting through the fluid outlet 20. A pump or valve may also be situation at the fluid outlet 20 to help the extraction of the fluid and control the flowrate. Referring now to the alternative embodiment of Figs.

3 and 4, this is similar m structure to the first embodiment and like numerals denote like parts with the suffix 'a' added. The principal differences are the smaller pitch of the nelical steel ribbon 30a and the transducer protective chamber 12a is attached to the ends of the ultrasonic processing unit 22a. There is also a flange 40 below inlet 18a to securely hold the cylinder liner 118. In this case the ultrasonic processor 22a is about 1.5m longer and the diameter is about 15cms. The inlet 18a and outlet 20a have a diameter of about 5c s and the annular thickness is about 2.5cms.

In use, the operation of the ultrasonic processor 20a is substantially identical to the operation of the processor of the first embodiment. Various modifications may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, the helical ribbon does not need to be wound in a constant pitch. A non-uniform pitch may be used or a uniform or non-uniform zigzag or wavelike pattern may be used. The ribbon may also be formed into a shape other than flat, such as a U or V channel cross -section or it may have short intermittent baffles extending from the ribbon surface to slow the flowrate and increase the exposure time. The helical ribbon may be attached by any suitable means, such as welding or by adhesmg the helical ribbon to the cylindrical member. The tubular housing may be made of any suitable material which couples ultrasonic energy from the transducers into the annular cavity, but the ribbon may be made of an alloy, plastic or any other suitable material. The ribbon may also have small through holes 40 (shown in broken outline in Fig. 1) .

The holes 40 may be of uniform diameter of about 5mm or, alternatively, a plurality of diameters ranging from 2mm to 10mm.

The helical ribbon may be formed by drilling a large compression spring centrally from the top to the bottom and the spring then stretched over a suitably sized cylindrical former to a desired pitch. By reducing the pitch of the helical ribbon the fluid can be made to flow slower, thereby increasing the exposure time to the transducers .

The ultrasonic processing unit may also be rotated clockwise or anti-clockwise during operation at a suitable speed to increase the residence time of the particles and increase shear forces within the slurry to assist particle break-up.

The transducers may be disposed within the cylindrical member instead of around the tubular housing or m combination with transducers around the housing. It will be understood there may also be a plurality of fluid inlets and fluid outlets. The transducers may be selected from other types which provide an ultrasonic signal, for example magnetostriction devices.

Figs . 5a to 5d show alternative embodiments where like numerals denote like parts with the two embodiments shown m Figs. 1 to 4. All of the previously mentioned modifications are also applicable here. Figs. 5a and 5b show two alternative embodiments where the central member 26b, 26c and housing 24b, 24c are conical. Figs. 5c to 5d show embodiments where the central member 26d, 26e is cylindrical and the housing 24d, 24e is conical. In Fig. 5c the cavity 28d converges from the inlet to the outlet and m Fig 5d the cavity 28e diverges from the inlet to the out let .

The principal advantage is that the apparatus and method according to the present invention provides is that the slurry with the particles to be reduced in size spends a longer residence time before the ultrasonic transducers, thereby subjecting the particles to more ultrasonic energy resulting in a more efficient and effective break-up of the entrained particles from the same energy input. The design uses commonly available materials and can be implemented as a new build structure or can be retrofitted to existing ultrasonic processors. The structure and method of the invention provides a more effective particle break-up with a higher proportion of smaller particles than the prior art leading to more consistent results and facilitating the disposal of such particles .

Claims

1. Apparatus for receiving a plurality of ultrasonic transducers to provide an ultrasonic processor for minimising the size of particles carried in a fluid medium, said apparatus comprising.- a hollow chamber having at least one inlet and at least one outlet; and a member disposed within the chamber between the inlet and the outlet and forming a path length for the fluid medium between the inlet and the outlet longer than the direct distance between the inlet and the outlet.

2. Apparatus as claimed in claim 1 wherein the hollow chamber and the member are generally cylindrical and define an annular cavity, and convoluted path means are disposed in said annular cavity for providing said path length.

3. Apparatus as claimed in claim 1 wherein the hollow chamber and the member are non- cylindrical .

4. Apparatus as claimed in claim 2 or claim 3 wherein the cavity between the hollow chamber and member varies in cross-section over the length of the member.

5. Apparatus as claimed in any preceding claim wherein the convoluted path is a flat ribbon arranged in a generally helical path between the outer surface of the member and the inner surface of the hollow chamber.

6. Apparatus as claimed in claim 5 wherein the ribbon is wound in a helical path from one end of the member to the other.

7. Apparatus as claimed in claim 6 wherein the helical wrap has a pitch which is uniform.

8. Apparatus as claimed in claim 6 wherein the helical wrap has a pitch which is non-uniform.

9. Apparatus as claimed in any one of claims 5 to 8 wherein the ribbon has a plurality of small through holes .

10. Apparatus as claimed in any preceding claim wherein the member is a cylinder extending from one end of the chamber to the other.

11. Apparatus as claimed m any preceding claim wherein the member is centrally mounted m a generally cylindrical hollow chamber.

12. Apparatus as claimed m any one of claims 5 to 11 wherein the ribbon is dimensioned and proportioned so that when disposed around the inner cylinder, the outer surface of the ribbon abuts the inner surface of the hollow chamber to seal against the passage of fluid between the edge of the ribbon and the inner surface.

13. Apparatus as claimed in claim 12 wherein the ribbon is helically welded to the member.

14. Apparatus as claimed m claim 12 wherein the ribbon is fastened to the member by any other suitable fastening means, including brazing and screw fasteners.

15. Apparatus as claimed in any one of claims 5 to 12 wherein the helical ribbon is formed by drilling a core from the top to the bottom through a large coil spring to create a spring bore, and then disposing the cylindrical member within the bore of the stretched spring.

16. Apparatus as claimed in claim 15 wherein helical ribbon has a pitch which is alterable by stretching or compressing the drilled spring.

17 Apparatus as claimed m any one of claims 2 to 16 wherein the cylindrical member is coupled to a drive means and is rotatable by sa d drive means about the longitudinal cylinder axis.

18. Apparatus as claimed m any preceding claim wherein a plurality of ultrasonic transducers is located longitudinally on the outer surface of the hollow chamber for transmitting high frequency sound.

19 Apparatus as claimed m any one of claims 1 to 17 where the transducers may be located within the cylindrical member

20. Apparatus as described m any one of claims 2 to 19 wherein the hollow chamber and cylindrical member are substantially vertical.

21. Apparatus as described in any one of the preceding claims wherein the inlet is at the top of the hollow chamber and the outlet is at the bottom of the hollow chamber.

22. Apparatus as described in any one of claims 18 to 20 wherein the hollow chamber, member and ultrasonic transducers are enclosed in a transducer protective chamber.

23. Apparatus as described in any of the preceding claims wherein the apparatus is used for minimising the size of drill cuttings .

24. Apparatus for use in minimising the size of particles carried in a fluid medium comprising-. a hollow chamber having at least one inlet and at least one outlet; a member disposed within the chamber between the inlet and the outlet and forming a path length for the fluid medium between the inlet and the outlet longer than the direct distance between the inlet and the outlet; and a plurality of ultrasonic transducers disposed between the inlet and the outlet for irradiating particles carried in said fluid medium in same chamber with ultrasonic energy.

25. Apparatus as claimed in claim 24 wherein the hollow chamber and the member are generally cylindrical and define an annular cavity, and convoluted path means are disposed in said annular cavity for providing said path length .

26. Apparatus as claimed in claim 24 wherein the hollow chamber and the member are non-cylindrical and define an annular cavity, said convoluted path means are disposed in said annular cavity for providing said path length.

27. Apparatus as claimed in claim 25 or claim 26 wherein the cavity between the hollow chamber and member varies in cross-section over the length of the member.

28. A method for minimising the size of particles carried in a fluid medium passing through a hollow chamber having an inlet and an outlet, the method comprising the steps of : irradiating the fluid medium and particles with ultrasonic radiation as the particles pass from the inlet to the outlet; and guiding the fluid and particles to move between the inlet and outlet in a path longer than the direct path length between the inlet and the outlet so that the exposure time of the particles to ultrasonic radiation is increased.

29. A method as claimed in claim 28 wherein the method includes the step of guiding the fluid and drill cuttings to move in a helical path within an annulus .

30. A method as claimed in claim 28 or 29 wherein the method includes the step of allowing some particles to bypass the helical path.

31. A method as claimed in any one of claims 28, 29 or 30 wherein the method includes the step of rotating the helical path.