GB2525509A

GB2525509A - Conversion method

Info

Publication number: GB2525509A
Application number: GB1507106.1A
Authority: GB
Inventors: Klaas Visser; Lee Campbell; Christopher Vaughn Venske; Erwin Visser; David Macwilliam; Kevan Stokes
Original assignee: HUNTING ENERGY SERVICES UK Ltd
Current assignee: HUNTING ENERGY SERVICES UK Ltd
Priority date: 2014-04-25
Filing date: 2015-04-27
Publication date: 2015-10-28
Also published as: GB201507106D0; WO2015162439A1; GB201407292D0

Abstract

A cyclone sand filter apparatus and method of conversion thereof from a sand filter, comprising a method of converting a sand filter comprising a vessel 1 and a filter element 4 mounted within the vessel to a cyclone filter 7 comprising the steps of removing an end cap 5 of the sand filter vessel, removing the filter element 4, replacing the cap with a housing 6 comprising a cyclone unit 7 and connecting the housing to the vessel 1.

Description

CONVERSION METHOD

The present invention relates to a method of converting one type of apparatus into another, and more particularly to converting one type of filtration apparatus into a different type of filtration apparatus, and more specificafly to converting a sand filter into a cyclone filter particularly for use in the processing of hydrocarbon fluid streams containing particulate materials, and particularly for separating out solids formed of particulate material, such as for example, sand, from the hydrocarbon fluid stream.

In the processing of hydrocarbons, fluids are recovered from a reservoir which may be located many hundreds or even thousands of feet below the ground or under the sea bed. The recovered fluids may contain solid particles which can seep into the fluid stream from the formation surrounding the reservoir. The solid particles typically consist of both formation fines which may not be part of the mechanical framework of the formation surrounding the reservoir, and load bearing solids which result from rock failure caused through stress from drilling and production and naturally existing each stresses and these solid materials are typically termed as "sand". Sand production is one of the major challenges facing the hydrocarbons industry in completing and producing oil and gas wells.

A build up of the sand in the formation or gravel pack around a well can lead to plugging of the perforations in the formation from which the hydrocarbons are produced and it is generally easier to deal with sand in the produced fluids at the surface than to face this issue at the boundary of the formation.

The production of sand causes wear to surface and subsurface well equipment such as valves, screens, pipes etc. and can which can lead to failure of the equipment as well as reducing the oil well productivity. Sand production also leads to additional processing costs in removing the sand contamination from the fluids.

In order to remove sand from the produced fluids one option is to pass the produced fluids through a sand filter. On an offshore production vessel or platform, the sand filter will typically be located close to the outlet of the production well in order to limit the length of pipe through which the produced sand flows and to limit the equipment through which it passes before it is removed form the produced fluids. In its simplest form, and as shown in Figure 1 a sand filter may be a vessel 1 with an inlet 2 and an outlet 3 and a screen 4 or membrane mounted between the inlet and outlet of the vessel to trap particles of sand whilst allowing the flow of the production fluids through the membrane from the inlet to the outlet The vessel is typically a vertical container with a cap 5 on the top of the container and an inlet 2 in the cap which allows fluids to be fed into the vessel. The fluid stream passes through the vessel and through the membrane in the vessel. The size of the apertures in the membrane may be selected depending upon local characteristics of the rock formation from which the fluid is recovered.

Filtered fluids exit the vessel from the outlet 3 in the lower part of the vessel, which may be below the membrane or on the other side of the membrane from the inlet whilst the sand is trapped within or on the membrane.

The use of such a sand filter provides a means for removing at least a portion of the sand particles from the fluid flow before the produced fluids are directed through the various processing stages.

Whilst a sand filter can be useful in some situations, the production of sand can vary over the lifetime of the well and when the level of the produced sand increases, a more efficient filtration method may be required.

Typically when changing from one type of filtration unit to another, the original filtration equipment is removed as a unit and a new system is installed. This leads to operators having to choose the filtration equipment carefully at the beginning of an operation without clearly knowing how the requirements for the filtration equipment will change over the lifetime of the production from the well.

The present invention aims to provide a conversion method which will allow the operator to choose between different types of filtration equipment and quickly and simply convert one type of the filtration apparition into another whilst maintaining the majority of their equipment in place thus increasing filtering efficiency for a relatively low costs compared to purchasing a new system and also provide a faster turnaround time which reduces the down time of the production operation.

The present invention also aims to provide a conversion method which allows the operator to select the most appropriate filtration apparatus for the level of sand being produced from a well and to quickly and efficiently react to changes in the sand production levels.

It is a further object of the present invention to provide a system which can be quickly and easily fitted to existing sand filters in situ to improve the efficiency of the filter without unduly interrupting the production of fluids from the reservoir, thereby leading to time and cost efficiencies.

According to one aspect of the present invention there is provided a method of converting a gravity sand filter to a cyclone filter comprising the steps of removing the end cap of the sand filter vessel, removing the filter element, replacing the cap with a housing comprising a cyclone unit and connecting the housing to the vessel.

The cyclone unit can be mounted onto an existing sand filter which increases the efficiency of the existing equipment in a cost efficient and time efficient manner, thus turning an existing sand filter into a multi-stage filtration unit Preferably the method further comprises the steps of connecting the flowline from a reservoir or well to an inlet of the cyclone housing.

Preferably the cyclone housing is sealed to the vessel of the sand filter.

Advantageously the cyclone unit is mounted such that a conical body of the cyclone unit extends into the upper portion of the vessel of the sand filter.

Advantageously the method further comprises mounting a flow conditioner between the inlet of the upper housing and the conical body.

I'he flow conditioner comprises a plurality of vanes which extend around a tubular member within the cyclone body.

The flow conditioner functions to encourage the spiral flow of fluid entering the cyclone and to create a vortex within the conical body such that centrifugal flow of the fluids within the cyclone unit thus encourages heavier particles of sand and other particulates to move outwardly within the cydone unit to contact the inner walls of the conical body and move downwards under gravity within the conical body from where they will be ejected out of the lower end of the conical body into the housing and fall into the lower body where they will be collected whilst the lighter fluids will swirl within the conical body and be drawn up into the tubular member and through the cap of the cyclone housing through an outlet spool connected th the housing.

Thus the present invention provides a simple, fast and effective method of converting an existing sand filter into a cyclone filter unit which facilitates more efficient and effective separation of sand particles and other heavy particulates from the fluid which flows into the apparatus.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a part sectional view of a known sand filter; Figure 2 is a part sectional view of a sand filter converted into a cyclone filter according to one aspect of the present invention, Figure 3 is a perspective view of a flow conditioner of the cyclone filter of Figure 2; Figure 4 is a part section view of a tubular member of the cyclone filter of Figure 2; Figure 5 is a part sectional view of a preferred form of flow conditioner mounted within the cyclone as part of the conversion process, and Figure 6 is a schematic view of an alternative tubular member according to a second embodiment of the invention.

Turning now to the figures there is described a method of converting a sand filter to a cyclone filtration unit.

Figure 1 is a schematic part cross-sectional view of a known sand filtration device.

The filtration device comprises a lower tubular hollow vessel 1 which defines a filtration chamber in which a filter membrane 4 is mounted.

Figure 2 shows a schematic part cross-sectional view of the sand filter of Figure 1 following conversion to a cyclone filter according to the method of the present invention.

The cap 5 of the sand filter is removed and the inlet and outlets 2 and 3 of the vessel are capped off An upper housing 6 containing the cyclone unit 7 is then mounted on the upper end of the vessel 1. The housing 6 is a substantially hollow tubular member as shown in Figure 2 and is open at one end.

The upper end of the vessel 1 and the lower end of the housing 6 may have corresponding radial flanges 8 which abut in order to mount the housing in position upon the vessel. Seal means (not shown) may be provided between the flanges.

Alternatively other means of connecting the vessel and housing together may be contemplated such as cooperating screw threads on each of the vessel and housing which allow the end of vessel to be screwed into the end of the housing.

In the embodiment shown, a collar 9 is mounted around the flanges to secure the housing on the vessel. The collar is a split collar with a nut connecting the two halves of the collar together around the flanges thus preventing the flanges from coming apart and separating the vessel from the housing.

The housing has an inlet 10 and an outlet 11. The inlet is provided through the side wall of the housing and is connected to the flow of produced fluids which are at well pressure. This can be done merely by connecting the same inlet spool which was previously connected to the inlet 2 of the sand filter, to the inlet 10 of the housing.

The outlet of the housing is provided at the upper end of the housing. A pipe or flowline is connected to the outlet of the housing and takes fluids from the cyclone filter on to further processing equipment. Thus the pipework connecting the outlet of the housing to the further processing equipment replaces the pipework connecting the outlet 3 of the vessel of the sand filter to the same further processing equipment.

A cap 12 is mounted on the upper end of the housing. The cap is substantially annular with an external thread provided on the lower outer surface of the cap.

This cooperates with a corresponding thread on the inner surface of the upper end of the housing and allows the cap to be securely fitted onto the housing. The outlet 11 of the upper is defined through the annulus of the cap.

A hollow tubular member 13 is mounted within the housing connected at the upper end to the outlet of the housing. The outer surface of the tubular member is spaced from the inner surface of the housing such that an annulus 14 is formed between the inner surface of the housing and the outer surface of the tubular member as will be described further below. The inlet 10 of the housing opens into the annulus and the interior of the tubular member is in fluid communication with the outlet 11 of the housing.

A cyclone device 7 is connected to the lower end of the housing 6 such that the lower end of the tubular member 13 opens into the cyclone device. The cyclone device comprises a substantially frustoconical body 15 which extends from a point adjacent to the lower end of the tubular member and into the upper end of the vessel 1. The frustoconical body reduces in diameter as it passes into the upper portion of the vessel.

A flow conditioner 16 is mounted on the outer surface of the tubular member 13 at a position close to but slightly above the lower end of the tubular member. The flow conditioner comprises a plurality of fins or blades 17 which each extend partially around the outer surface of the tubular member. As each fin extends circumferentially around the tubular member it also extends longitudinally along the tubular member such that the ends of each fin are off-set longitudinally along the tubular member.

In the embodiment shown, 3 fins are provided and the ends of each fin overlap circumferentially with the ends of the adjacent fin. Further or fewer fins may be provided and the length of the fins will be selected to maintain the circumferential offset as noted above.

The fins are preferably machined into the side of the tubular member. In some embodiments the tubular member is initially machined from a block of material and the fins are defined during the machining process. This ensures the integral strength of the fins and provides for greater stability of the tubular member.

Alternatively the fins may be welded or otherwise attached to the outer surface of the tubular member.

In a preferred embodiment, the flow conditioner is moulded as a single piece component. The flow conditioner comprises a housing 160 formed of an outer cylindrical wall 161 and an inner cylindrical wall 162, concentric with the outer wall. The fins 170 of the flow conditioner extend between the outer and inner walls of the housing. As described above, each of the fins extends partially around the flow conditioner with the ends of one fin overlapping with the ends of the adjacent fin(s). Also, as described above, each fin extends longitudinally along the housing as it extends between outer and inner walls.

The flow diverter is formed of a highly wear resistant alloy and may in some embodiments be formed of a nickel alloy such as Ni hard 4. In one embodiment the alloy may comprise 3% C, 9% Cr, 5% Ni and 2% Si.

The inner proflle of the tubular member is shown in Figure 4. Where the flow diverter is formed on the outer surface of the tubular member, the inner diameter of the tubular member increases toward the lower end [in use) of the tubular member such that a flared throat 18 is formed in the tubular member between the flow conditioner and the lower end of the tubular member.

In the alternative embodiment described above where the flow conditioner is formed of a moulded one piece body, the tubular member may be provided in two sections 130, 131, with the first section having a constant inner diameter and the second section including the flared throat 18. Preferably the second section has a shorter ength than the first. The lower end of the first section has an internal thread 132 which cooperates with an external thread [not shown) on the upper end of the second section such that the second section can be threaded onto the lower end of the first section.

In this embodiment the flow conditioner is mounted on the lower end of the first section of the tubular member 130 and the upper end of the second section 131 of the tubular member passes through the internal wall of the housing as it is threaded onto the lower end of the tubular member. The inner wall of the housing of the flow conditioner has a diameter that is smaller than the outer diameter of the upper end of the second section of the tubular member, but greater than the outer diameter of the lower end of the section such that by threading the first and second sections of the tubular member together, the flow conditioner is firmly mounted around the outer surface of the tubular member.

Means are provided for preventing relative rotation of the flow conditioner and the tubular member. Preferably the flow conditioner has a key or lug 170 which is preferably integrally formed with the inner wall 162. This lug is shown in Figure 5 as depending from the lower edge of the inner wall. A cooperating recess is formed in the outer surface of the second section 131 of the tubular member. When the lug is inserted into the recess, the flow conditioner is prevented from rotating with respect to the tubular member.

A flow line from the production well containing produced fluids and sand is connected to the inlet 10 of the housing and a further flowline is connected to the outlet 11 of the housing to take filtered fluids on to further processing equipment 1 0 Produced fluids flow through the flowline and enter the housing 6 through the inlet into the annulus 14 between the upper housing and the inner tubular member. The fluids flow around the annulus and are forced over the fins 17 of the flow conditioner where a vortex is induced in the fluids. As the fluids are pushed down through the annulus, over the flow conditioner they then enter into the upper part of the frustoconical body and, the reducing diameter of the body causes the flow of the fluids to increase and the rotation of the fluids throws heavier particles within the fluids to the outer edge of the frustoconical body while the lighter fluids stay within the centre of the body. This causes the heavier particles to fall from the frustoconical body into the sand filter vessel below while the lighter fluids are drawn up into the tubular member 13 and pass through the tubular member and out through the outlet of the cyclone body into the flowline and on to additional processing equipment.

The produced sand falls with any remaining fluids into the sand filter from where it can be recovered in one of a number of known methods.

The present invention provides for a simple, quick and effective method of converting a known sand filter into a cyclone filter unit which can provide increased efficiently, can handle liquid as well as gasses and allows for an improved range of sand particle sizes beyond that which can be recovered using a standard sand filtration unit.

The taper angle of the frustoconical body can be selected to control the characteristics of the cyclone filter. Alternatively or additionally, the pitch angle of the fins of the flow conditioner may be selected or modified in order to maximise the centrifugal flow of the fluids and thus maximise the separation of heavier sand particles from the fluid flow within the cyclone body. Alternatively or additionally the length of the tubular body may be selected to control and change the characteristics of the cyclone filter.

It is generally simpler to flush out the vessel of the converted filtration unit following the method of the present invention which will deliver further efficiencies and savings over the known sand filtration units.

Furthermore, sand filters typically require a level or near level platform upon which to operate efficiently. Therefore the present invention provides a further advantage in that a less efficient sand filter or a sand filter that looses efficiency over its life time can be converted into a cyclone filter without replacement of the complete equipment which provides for greater choice whilst reducing the downtime, cost and disruption to the operator.

Additionally where the conversion method is carried out with a flow conditioner as described in figure 5, any erosion which is detected in the flow conditioner can be addressed by simply removing the second section of the tubular member from the first and releasing the flow conditioner. A replacement flow conditioner can therefore be quickly and simply installed on the tubular member during operations if required without the need to disassemble the cyclone or provide a replacement tubular member. This provides significant advantages of time and cost savings for the operator and replacement flow conditioners can be stored locally for use without taking up significant storage space which is likely to be of a premium, particularly offshore.

Claims

CLAIMS1. A method of converting a sand filter comprising a vessel and a filter element mounted within the vessel to a cyclone filter comprising the steps of removing an end cap of the sand filter vessel, removing the filter element, replacing the cap with a housing comprising a cyclone unit and connecting the housing to the vessel.
2. A method according to c'aim 1, wherein the method further comprises an initial step of disconnecting flow lines from an inlet and an outlet of the sand filter prior to removal of the end cap of the vessel.
3. A method according to claim 2, where in the method further comprises the step of reconnecting the flow lines to an inlet and an outlet of the housing after the housing is connected to the vessel.
4. A method according to any one of the preceding claims, wherein the cyclone housing is sealed to the vessel of the sand filter.
S. A method according to any of the preceding claims, wherein the cyclone unit is mounted such that a conical body of the cyclone unit extends into an upper portion of the vessel of the sand filter.
6. A method according to any of the preceding claims further comprising inducing a centrifugal flow of fluids within the cyclone unit to encourage heavier particles in the fluids to move to the outer surface of the cyclone unit.
7. A method according to claim 6, wherein the heavier particles in the fluids are ejected from the cydone unit into the vessel.
8. A method according to claim 7, further comprising withdrawing the fluid flow following removal of the heavier particles from an outlet of the vessel.
9. A method according to any of claims 6-8 wherein the flow of fluids entering the cyclone unit is conditioned by passing the fluids over a plurality of blades mounted between the in1e ofthe housing and the cydone unit
10. A method of converting a sand filter comprising a vessel and a filter element mounted within the vessel to a cyclone filter substantially as hereinbefore described.
11. A cyclone filter converted from a sand filter in accordance with the method of any of the preceding claims.
12. A cyclone filter according to claim 11, comprising an upper tubular body and a lower conical body.
13. A cyclone filter according to claim 12, wherein a housing is replaceably mounted around the upper tubular body, said housing comprising one or more blades.
14. A cyclone filter according to claim 13 wherein the housing further comprises inner and outer tubular walls and the one or more blades extend between the inner and outer tubular walls.
15. A cyclone filter substantially as hereinbefore described.