CA2074247A1

CA2074247A1 - Cleaning device

Info

Publication number: CA2074247A1
Application number: CA 2074247
Authority: CA
Inventors: David H. Saunders; Thomas W. Grove
Original assignee: Individual
Current assignee: BHR Group Ltd
Priority date: 1990-01-19
Filing date: 1991-01-21
Publication date: 1991-07-20
Also published as: FI923294A0; EP0511296A1; WO1991011270A1; AU7213991A; FI923294A; GB9001249D0

Abstract

ABSTRACT OF THE DISCLOSURE

A conduit (3) Can be cleaned by directing jets (10-14, 25) of abrasive mixture from a pressurized supply at its internal wall from a plurality of nozzles (7, 13, 16) which have no tangential component about the conduit axis. Nozzles preferably includes two types, one type (7) which is inclined in one direction to the axis and another type (13) which is inclined in the opposite direction to the axis. When the conduit (3) has an open end, the nozzles (7) directed away from that end are preferably closer to the end than those (13) directed towards it. The density of abrasive mixture supplied by the different types of nozzles is arranged to be different by swirling the mixture and supplying different types of nozzles from different radii in the swirl output chamber (6).

Description

207~2~7 CLEANING DEYI OE

Hard deposits build up on the internal surfaces of process pipework in a munber of industries as diverse as brewing, power generation and oil production. It is a particular problem in oil production where S deposits such as barium sulphate are formed within the production tubing of producing oil wells ~t. and immediately above the reservoir depth. These deposits reduoe the flow area of the tubir~g, thereby reducing oil flow to the surface. These depDsits are very hard. If a mechanical cutter/reamer is used to remove them, damage is frequently 10 caused to the steel pipe itself. m e alternative solution at present is to extract the entire length of production tubing to the surface, and to replace it with a new pipe. Because of the depth of some wells this is a laborious and expensive procedure.

The present invention is designed to assist the removal of hard 15 deposits from a steel pipe without damaging the pipe itself. Flushing flow may be provided to transport the removed deposit to the surface if any fluids beir~ transported by the pipe are not sufficient to do this themselves. Tests have shown that high velocity jets of water will cut through barium sulphate deposits. However to achieve a satisfactory 20 performance pressures of the order of 150 million pascals or higher are required, which is not practical to generate~ in a deep oil well.
Further testing has shown that the addition of low concentrations of solid particles to the flow can dramatically enharce the performance of the jets. This enables the descaling operation to be carried out at 25 much lower pressure, typically at 20 million pascals or less. The invention is therefore suitable for operation in conjunction with conventional oilfield pumping, pipework and other equipment.

According to one aspect of the invention there is provided a head for forming jets ~ithin a condlut of abrasive mixture from a pressurised -: .. ~ .~:: : :

207~2 '17 -- 1~ --supply, the head being formed with a re.servoir for receiving themuxture and a plurality of nozzles which have no tangential component about the conduit axis, the nozzles ccnprising different types, including one type which is inclined in one direction relative to the S axis, and another type which is inclined in the c~osite direction relative to the axis, toth typ~s being fed from mixture in said reservoir.

In another aspect of the invention there is provided a method of cleaning the internal wall of a c~nduit c ~ prisin~ directing jets of 10 abrasive nixture from a reservoir at the internal wall, the jets having no tangential component about the conduit axis, the jets comprising different types, including one type which is Lnclined in one ~irection relative to the axis, and another type which is inclined in the c~x~site direction relative to the axis, both types being fed from 15 mixture in said reservoir.

The two types of jets or nozzles enable cl~aning action to be directed at different angles so that one type may achieve cleaning action if the other type dbes not. On the other hand, the two types are fed with abrasive mixture from a single reservoir so that a simple form of 20 construction can be used.

2 ~ 7 Examples of the invention will r~ow be described with reference to the accompanyir~ drawings in which:-. .
FiO~e 1 is an overall view of a descaling syste~;

Figure 2 is an axial section through the jetting head of 5 Figure l;

FiO~e 3 is a radial section throu~h the head of FiO~ure 1;and Figure 4 shows the jet pattern which can be achieved by the head of Figure 1.

10 An abrasive moxture, comprising carrier fluid and abrasive particles is formed and pressuri~ed in a pumping system 21 such as is described in our Patent Publications GB-A-2162778, EP-A-258424 and EP-A-276219 is fed through a coiled tubing unit 20 to a pipe 2 which is fed down the axis of the pipe 3 to be descaled. The abrasi~e mixture is applied to l5the bore of the pipe 3 from a special jetting head 1 on the lower end of the pipe 2 which pipe passes through a spacin~ block 22 for keeping the pipe 2 cen~ral within the bore of the pipe 3, although the symmetry of the spray from the head 1 to be described below may be sufficient to effect the centralising action, rendering the block 22 redundant.

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2~2~7 W O 91/11~70 PCT/~Bg1/OOa88 The sl~lrry (abrasive muxture) floh enters the jetting head 1 from the supply pipe 2 at one end throt~h a s~irlir~ vane ; (see Figure 2) which imparts rotation to the floh. This causes separation of the constitutents of the flow, with the denser solid particles being 5 concentrated in outer parts of swirl cham~er 6. A ring of six nozzles 7 is set into the outer wall 8 of swirl chamber 6. The nozzles 7 are fan-jet rozzles (i.e., the jet is elongated tangentially) ~hich spread the jets of concentrated sll~ry 10 as ~t flat sheet 11 with an included angle of spread of 120 degrees to ~)rovide a complete ring of coverage 10 of the production t~ir~ 3 and the deposit 4. In Figure 4 only the flat sheet jets from alternate nozzles in the ring are shohn in full.
The jetting head 1 is steadily lowered or raised on the pipework system 20. In this way the jets 10 are traversed along the tubir~ 3 and the impact of the solid particles in the sltlrry jets 10 on the deposit 4 15 cause it to be removed from the ~all of tllbing ~. The nozzles 7 are slightly inclined dGwnwardly, so that the jets 10 tend to bite behind the scale as the head 1 moves progressively down the tl~ing 3.

The central portion of swirl chamber 6 is extended at a s~aller internal diameter 1~ and supplies another array of nozzles 13. Because 20 the solid particles move to the outer portion of the chamber 10, the flow enterir~ the extended portion of s~irl chamber 6 contains very feh solid particles. Ihe jets 2; produced b~ the noz les 13 are also fan-shaped. These nozzles 13 are slightly inclined tlpwardly and provide a flllshir~ flow to carry the solid particles from the slurry 2~ jets 10 and the deposit which the~ have removed from the wall of tubing 3 back to the sl~face. The fan shape of the jets ensltres a flushing flow arol~nd the fllll circt~ference of the tl~ing ~. It will be seen that the jets fr~m the nozzles 7 and 13 are directed tohards each other. The jets fr~ nozzle 7 directe~ ctway froD the end at which the 30 supply pipe 2 enters the jetting head 1 are closer to that end then the nozzles 13 from which the jets are directed to~ards that end. In an oilfield application, the tt~ing is vertical and the abrasive mixtl~e supply comes from and the fltlshed seale is directed back to the upper . , .

: -' - , 2~7~2-~7 W O 91/11270 P~r/GB91/0~88 open end of the tubing.

.~n additional particle carrying nozzle 16 is fitted into the base of the jetting head 1. A conduit 1~ supplies solid particle laden slurry to noz~le lS frc~ the supply pipe 2 upstream of swirl~ng ~ane 5 so that S although it is of small diameter it has not been stripped of particles by the swirl action. Nozzle 16 prc~uces a generally axially directed jet 14 in a spreading conical form. The solid particles in jet 14 impact with any of the deposit 4 ~hich extends in towards the centre of the tubing 3 causing it to be removed and opening up a passagehay 10 through ~hich jetting head 1 can advance along the tubing 3. -The pipework system 20 as shown in Figure 1 is a coiled tubing unit.Alternatively the pipework system might be in the form of pipe lengths ~ich are joined together to extend the length of the system, as for drilling pipe. Both types of pipework system are commonly used in 15 oilfield applications. Other pipework systems might be used~
especially where the invention is used to descale pipes in industries other than the oil industry.

As shown in Figure 3, the nozzles 7 and 13 are equally spaced around the jetting head 1. This provides a balance of the reaction foroes of ~Q the jets 10 and 2; and is the preferred arrangement where no rotational motion of the jetting head 1 is provided as in Figures 1, 2 ard 3.
Since ncne of the nozzles is directed tangentially, the reaction of the jets provides no rotational drive.

Rotational motion can be provided either from the surface or by a 2j downhole motor (not shown). Where rotational motion is provided the centralisin~ ~lide 22 absorbs the reaction force generated by the jets.
In this mode of operation a simple mechanical scraper can form part of the centralising guide and will remove any small segments of the deposit which are weakened but not removed by the direct action of the 30 jets.

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2~7~2-~7 In Figure 4 a single ring of six solid particle carrying nozzles produces fan-shaped flat sheet jets 11, each ~ith an included angle of 120 degrees. The numbcr of nozzles 7 and the ar~le of the fan sheet 11 are selected based on the mini~um bore of the tubing 3 to be descaled S to provide full coverage of the tubing 3. The rir~ of nozzles could be replaced by a single nozzle producing a hollow cone shaped jet or by multiple rings of nozzles or by multiple hollcw cone shaped jets to r~nove the deposit in progressive steps. The jets with an axially downward direction are useful for separatirlg the deposit fro~ the walls 10 of the pipe 3 whereas the jets with an axially upward direction are useful for flushing the removed deposit up towards the surface and this action may be assisted by any fluids being transported upwards by the pipe at the same time. Where more than one ring of noz~les is used different angles can be used to alter the pattern of attack on the 15 deposit. Where only one ring of nozzles is used individual nozzles can be set at different angles to achieve the same effect. In a similar manner the ring of flushing flow nozzles 13 can include nozzles producing different shapes of jet and also be replaced by more than one ring of nozzles or by a single nozzle for example one producing a cone 20 shaped jet. This also applies to the single forward facing particle carrying jet nozzle 16. This can be replaced by a nozzle producing a different shape of jet or by a m~mber of nozzles.

Although flushir~ flow no7zles 13 are shown in Figures 1, 2 and 3 the flushing flow is not required for all descaling operations. For 25 example they are not necessary when there is a high production flo~ in the tubing 3. In a si~ilar manner the single forward facing nozzle 16 is not necessary where it is known that the thickness of deposit is not too great. This can particularly be the case where the jetting head 1 is used to carry out regular maintenanse as opposed to remedial 30 operations.

2~

The use of an abrasive mixture is better than the use of fluids alone. The solid particles impact with the brittle deposit, causing it to crack and break off in discrete 5 pieces from the action of carrier fluid of the jet being forced into cracks formed by the impact of the particles.
The size of the dislodged pi~sces of deposit is controlled by setting of the jetting parameters, such as pres~ure, flow, particle size and other particle properties, and particularly by the concentration of particles in the flow. The solid particles do not need to be of any particular shape to achieve the effect on the brittle deposit, and therefore rounded particles can be used, which will ensure that the underlying pipe is not damaged by the action of the jet. Because of the nature of the solid particles, the effect on the pipe will be confined to a beneficial shot-peening action.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN Exclusive PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A head for forming jets within a conduit of abrasive mixture from a pressurised supply, the head being formed with a reservoir for receiving the mixture and a plurality of nozzles which have no tangential component about the conduit axis, the nozzles comprising different types, including one type which is inclined in one direction relative to the axis, and another type which is inclined in the opposite direction relative to the axis, both types being fed from mixture in said reservoir.

2. A head as claimed in Claim 1 wherein means are provided within the head to supply abrasive mixture of different density to the said different types of nozzle from said reservoir.

3. A head as claimed in Claim 2 wherein the head is adapted for connection to the pressurised supply at one end and said means includes a swirl device feeding said reservoir, the type of nozzle inclined away from said one end being fed with mixture from the outer portion of said reservoir and the other type of nozzle being fed with mixture from the inner portion of said reservoir.

4. A head as claimed in any one of Claims 1 to 3 wherein a nozzle of one type is axially spaced from a nozzle of another type such that abrasive mixture ejected from them are directed towards each other.

5. A head as claimed in any one of the preceding Claims comprising a further nozzle directed axially.

6. A head as claimed in Claim 5 when dependent on Claim 3 comprising a conduit for feeding abrasive mixture upstream of said swirl device to to said further nozzle.

7. A head as claimed in any one of the preceding Claims wherein a said nozzle is adapted to produce a jet which is shaped as a fan extending in the tangential direction.

8. A method of cleaning the internal wall of a conduit comprising directing jets of abrasive mixture from a reservoir at the internal wall, the jets having no tangential component about the conduit axis, the jets comprising different types, including one type which is inclined in one direction relative to the axis, and another type which is inclined in the opposite direction relative to the axis, both types being fed from mixture in said reservoir.