WO2005115583A1

WO2005115583A1 - Apparatus for filtering of solids suspended in fluids

Info

Publication number: WO2005115583A1
Application number: PCT/NO2005/000166
Authority: WO
Inventors: Michael Hilditch; Knut Nyborg; Geir Inge Olsen
Original assignee: Aker Kvaerner Subsea AS
Current assignee: Aker Solutions AS
Priority date: 2004-05-27
Filing date: 2005-05-18
Publication date: 2005-12-08
Anticipated expiration: 2006-11-27
Also published as: NO20042196D0; NO20042196L

Abstract

Apparatus for filtering of solids suspended in fluids, comprising a screen (9). The screen is adapted to allow fluid to pass there through and preventing particles larger than a specific size from passing there through. The screen forms at least a part of a wall (8) defining a cavity. The screen (9) has an inner surface facing the cavity. The inner surface is substantially smooth with a plurality of openings. The cavity has a substantially uniform cross-section over the length of the screen, and the screen is at either end coupled to a channel (2, 3) having a cross-section with at least the same dimension as the cross-section of the cavity. This allows for through pigging of the screen, on order to remove solids accumulated on the inner surface of the screen.

Description

Apparatus for filtering of solids suspended in fluids

The present invention relates to an apparatus for filtering of solids suspended in fluids, comprising a screen, adapted to allow fluid to pass there through and preventing particles larger than a specific size from passing there through, the screen forming at least a part of a wall defining a cavity, the screen having an inner surface facing the cavity, the inner surface being substantially smooth with a plurality of openings.

One problem with filtering of particles is that the particles may clog the filter screen. Conventionally, filter screens are made up by a wire mesh, wherein wires with a circular cross section are placed with a small distance from each other. The distance between each wire is large enough to let the fluid or gas pass and small enough to prevent particles beyond a certain size from passing. However, there is a tendency that particles of a certain order of size become entrained in the crevices of the wire mesh. These particles in turn trap smaller particles and finally form a cake that may clog the filter. Thereby, the fluid and gas amount passing through the filter will decrease and hence the capacity of the filter will be greatly reduced.

In sand screens for preventing particles in a hydrocarbon producing well from entering the production tubing a new type of filter mesh has been introduced. The sand screen of this type is called "wedge wire" screen. It consists of wires with a wedge shaped cross section. The broader part of the wedge section is facing outward towards the walls of the well bore. The slot created between the wires is narrowest closer to the walls of the well bore and broadens towards the production tubing. Thereby, particles that pass the narrowest part of the slot will pass all the way through the screen and not clog the wire mesh. An example of this wire type of screen used as a sand screen can be found on the Internet web page http :// ww.reslink.no/products 1.ph .

This type of wedge wire screen has also been used in cartridges for filters, as shown, e.g., on the Internet web page http://www.novafiltration.com/norsk/produkter olie gass/manuellefiltre.htm. In this application of the filter type, the cartridge is placed inside a vessel and has to be removed from the vessel for cleaning. The cartridges are generally of a diameter from 50 - 100 mm.

The invention has its main object to make use of the principles of the new type of screen in the interior of a particle filter apparatus and facilitate the cleaning of the filter screen, avoiding the need for removing of the filter screen for cleaning. This is achieved by an apparatus wherein the cavity has a substantially uniform cross-section over the length of the screen and that the screen at either end is coupled to a channel having a cross- section with at least the same dimension as the cross-section of the cavity, to allow for through pigging of the screen, on order to remove solids accumulated on the inner surface of the screen.

In a preferred embodiment the openings in the screen comprises an entrance opening facing the inner cavity and an exit opening facing away from the inner cavity, the entrance opening being of a smaller dimension than the exit opening. This results in a rigid screen with a reduced risk of clogging.

In a further preferred embodiment the apparatus comprise an outer vessel or pipe with at least one inlet and at least one outlet, the vessel or pipe enclosing an inner pipe comprising the wall with the filter screen, the inner pipe passing through the outer vessel or pipe and forming two ends of the inner pipe outside of the outer vessel or pipe. This results in a convenient filtration unit that can be coupled to other pieces of equipment in a system.

Preferably, the outer pipe, the inner pipe and filter screen are elongate generally cylindrical elements. This results in an apparatus that can be manufactured easily at low cost.

In one alternative embodiment the inner pipe and filter screens are situated concentric to the outer pipe. This provides an apparatus that is easy to manufacture and gives an even distribution of the fluid within the apparatus. In another alternative embodiment the inner pipe and filter screens are situated eccentric to the outer pipe. This provides the possibility to place the inner pipe in the vessel where it is most convenient to have the outlet of the fluids from the screen.

Preferably, the filter screens are constructed of a wedge type profile, having a wedge base facing the inner cavity. This provides a smooth inner surface and a widening screen opening from the entrance to the exit.

In an alternative embodiment the outer vessel or pipe comprises means for backwashing the filter screen. This provides for an additional means for cleaning out solids.

The apparatus may be installed as a primary and or secondary solids/sand screen filter to a production well head, production well template production well manifold and/or a processing unit, or as a stand alone separator or a part of or multiple parts of another separator.

Preferably, the apparatus and/or filter screen is removable and/or re-installable or is a part of another apparatus that is removable and or re-installable.

An important advantage of the apparatus according to the present invention is that it can be cleaned by pigging and/or backwashing. This can take place in a stand alone system, sub system or inline with a flow line or pipe line, or as an integral part of any other type of processing equipment. Many of the applications were the apparatus of the invention would be used are for subsea but may be applied to topside or land based systems were solids filtering is required, especially with a pipeline or similar allowing for pigging or other types of mechanical cleaning of the filtered residue.

In a preferred embodiment the apparatus has at least one main process inlet and at least one main process outlet and may have several secondary inlets/outlets and would generally be referred to as a pressure vessel and is preferably generally orientated horizontally, although it can be oriented differently. The apparatus is formed from a pipe in pipe construction where the outer pipe acts as the main pressure retaining shell, the inner pipe, which traverses through the apparatus, acts as an inline pigging pipe and contains one or more sections for filtering solids media from fluids (liquid and/or gas) flowing from the inner pipe into the outer pipe. The apparatus may be equipped with backwashing facilities, mixing and chemical dosing, heat tracing and insulation. *

The wedge type filter screen referred to above in connection with the use as a sand screen in the well bore hole, is in the present invention inverted, so that the broader part of the cross section is facing inward towards a cavity into which the medium to be filtered is introduced. This will be explained in detail later with referring to drawings of a preferred embodiment.

The invention is intended to cover all applications for use in the processing of a hydrocarbon well stream needing protection were the well stream can carry solids that may be detrimental to the operation or clogging or residue build-up or erosion in items generally used in process systems such as e.g. rotating equipment (pumps and compressors etc), separation and separation enhancing equipment, control equipment and instrumentation.

Further the apparatus of the invention may be used to act as a primary particle filter for larger solids hence reducing the load and operation of equipment such as fine solids de- sanders and continuous production fines handling devices.

Further the apparatus of the invention may provide a secondary solids filter barrier for accidental screen failure in a production well resulting in large quantities of sand entering the system that may overload and cause failure to a process systems sand management system. The apparatus may also act as a primary solids filtering screen for wells that are not fitted with downhole well sand screens.

As a primary or secondary barrier on a production well with or without a well sand screen the apparatus can also be installed in or with the following systems/equipment:- • As part of, upstream or down stream or parallel to a well head tree's choke valve bridging spool. • As part of, upstream or down stream or parallel to a between a well head tree and associated manifold, jumper line. • As part of, upstream or down stream or parallel to a manifold system. • As part of, upstream or down stream or parallel to a manifold to pipe line end manifold jumper. • As part of, upstream or down stream or parallel to a PLEM to PLEM jumper. • As part of, upstream or down stream or parallel to a riser base piping/manifold. • As part of, upstream or down stream or parallel to a topside or land based pipe line, header or manifold.

Further, this invention relates to the use/operation of the said apparatus either as a stand- alone unit or multiples thereof and/or integrated with and/or inline with other sub sea and/or topside units/systems. The said apparatus in addition to being used inline with pipe manifolds, flow lines and pipe lines, can be integrated into a system with other processing units and or be an integral part of processing equipment e.g. gravity separators of conventional pressure vessel types to long pipe separators whether or not pigging is required.

Further the apparatus can itself be a separator or part of a separator used singularly or in multiples thereof and may be of varying lengths from short to long. Further the apparatus may be used singularly or in multiples thereof combined inline with other processing apparatus installed singularly or multiples thereof as pre, intermediate or post processing phases.

Although the apparatus would normally be installed inline with a flow line/pipe line or manifold, when used subsea it can be made removable for cleaning and or replacement or made such that the internal screen can be a removable insert, in such case the apparatus would be fitted with well known tie-in devices commonly used in the industry, methods of retrieving/reinstalling/replacing the apparatus from the seabed can be in many forms and will be readily understood by a person of skill. In the case were the apparatus is a long pipe unit, the method of vertical installation can be adopted with a so-called guide and hinge over principle were one end of the said apparatus is guided and located at one end and then lowered into its final resting place before be coupled to the system.

In shallow waters were diver intervention can be utilized the apparatus can be manually connected by bolted flanges without the use of special tie-in devices as would also be the case for the apparatus being used topside.

In the following the present invention will be explained under reference to preferred embodiments of the invention, and will refer to drawings showing these embodiments, in which:

Figures 1 a - c show the apparatus according to the invention were

Figure la shows the main body of a filter according to the principles of the present invention, figure lb shows a see-through version of figure la and lc shows a longitudinal section of figure la.

Figures 2a-d shows an example of the apparatus according to the present invention with figure 2a showing the filter in figure la in side elevation, figure 2b showing a detail of the inner filter screen, figure 2c showing the principle working of the wedge type screen and figure 2d showing the principle working of a conventional wire screen.

Figures 3a-c illustrates the principles of a method for using a cleaning pig in the filter according to figure la in three steps.

Figures 4a and b illustrate two examples of the use of the filter according to figure la shown in a system diagram.

Figures 5a-e illustrate some additional examples of the use of the apparatus according to the invention were figure 5a shows the apparatus according to the invention as a stand alone long small diameter separator/ pipe separator, figure 5b as a part of a long small diameter separator/pipe separator. Figure 5ab shows an alternative route for piping to figures 5a-b. Figures 5c-d show examples of how the apparatus may be configured for assisting in the collection of separated phases. Figure 5e shows the apparatus according to the invention installed as an integral part of a separators inlet device, which allows for pigging through the separator.

Figures 6a and 6b illustrate an example of the placement of the inner pipe of a separator according to the invention. Figure 6c is showing a detail of figures 6a-6b.

Figures 7a-f illustrate additional examples of the filter screens placement and orientation in the inner pipe of a separator according to the invention.

The invention will first be explained with reference to figures la-c, 2a-d, 3a-c and 4a-b. The apparatus, which in the illustrated examples is a filter, comprises a vessel 1, which is generally cylindrical and may be made from pipe and forms the main pressure- retaining component. The apparatus of figure la has one main process inlet 2 and one main process outlet shown in figure la-c with two process outlets 4 and 5. The outlet 3 is for pigging. The apparatus may have several primary or secondary inlets and/or outlets (e.g. for back-washing facilities, mixing, chemical dosing flushing/purging etc, not shown).

The inner pipe 8, which is extending from inlet 2 to outlet 3, and is best shown in figures lb and lc, is a through pipe designed for full bore pigging and contains a section that has a filter screen 9 (further illustrated and explained in figure 2a-c).

Under normal production feeding the processing unit outlet 3 will be isolated by a valve 10 (fig. 3 a) downstream of outlet 3, fluid flow from the production wells (typically a mixture of gas, oil and water) enters the inlet 2 and passes through the filter screen 9 into the outer volume between the outer pipe 1 and the inner pipe 8, 9. Depending on the filter screen 9 openings, solids in the production fluid are retained on the inner surface of filter screen 9. The filtered fluid is then passed through the outlets 4 and 5 that may be a single or multiples of outlets. The number of outlets will depend on the length of the filter screen 9, so as to even out the flow through the open areas path. The outlets 4, 5 may then be collected into a header pipe 6, converging into a single outlet 7 to then feed the relevant system.

As referred to above, a special feature of the said apparatus of the present invention is the use of a newer type filter screen which is today used as a sand screen in the well borehole. Here the same principle is basically used but the screen is inverted compared to the downhole use. A well bore sand screen is generally a filter media wrapped onto the outside of a perforated pipe, were the flow is from the outer area (between the production tube and the walls of the well bore) into the inner pipe (production tube), thus retaining solid particles on the outer surface of the sand screen. This sand screen can be subject to wear, failure or damage during installation, which in turn can cause extra or unexpected sand production. The conventional wire mesh, e.g., involving woven screens, have in addition a tendency to become blocked.

The newer type of sand screen that has now been accepted as being less prone to blockage is (as mentioned above) normally referred to as 'Wedge Wire'. The principle difference between a conventional wire mesh and the wedge wire will be explained referring to figures 2a-d. Figure 2a shows a partly see-through side elevation of the filter of figure la. Figure 2d shows a conventional type wire mesh screen. In this type of screen wires with a generally circular cross section is laid side by side with a predetermined distance between the wires. The distance is determining the maximum particle size that is allowed to pass through the wire screen. Particles that are large than the distance between the wires cannot pass through but may become entrained in the crevices of the wire mesh, as illustrated in figure 2d. The larger particles may then trap smaller particles, which may form a cake and eventually clog the filter.

Figures 2b and 2c illustrates the newer wedge shaped wire mesh. Also here the wires are placed with a predetermined distance there between. However, this screen has an even surface facing the fluid that is to be filtered. The openings between the wires are at their narrowest closest to the even surface and broadens away form this surface. This means that this filter screen traps larger particles onto the top face of the filter screen and allows the smaller particles to pass through the filter screen openings. As long as the particle can pass through the narrowest part of the screen, the particle will pass all the way through. There is no crevice on the substantially even surface for the particles to become entrained.

For the filter apparatus according to the present invention this principle is used but inverted compared to the downhole sand screens, that is to say that the even surface with the broadest cross section of the wedge wire is on the inner face of the pipe 8, 9, with the fluid flow from the inner to outer side of the screen, as shown in figure 2b.

The filter screen opening size for particle size filtering can vary from at least 30 microns and larger.

By designing the pipe 8 and the screen 9 with a substantially uniform cross section, the filtered particles being captured on the inner surface of the pipe shaped screen 9 can be mechanically cleaned by pigging, as will be explained in detail below.

The detailed construction and fabrication methods of producing the wedge filter screen are not explained here, as they will be readily understood by a person of skill as the actual wedge profile of the filter screen can be continuous wire, wire rings, machined rings and slotted plates, the only criteria is that the inner surface of the screen 9 is mainly flush with the inner surface of the pipe 8, to facilitate pigging, and that the filter pipe 9 is adequately reinforced to sustain the strength required for pressure loads and the mechanical cleaning forces created by pigging the system.

An example of the inner pipes solids particle retention and pigging of the inner pipe is shown in figures 3a-c. Figure 3a shows a valve 10 closed downstream of the apparatus with particle retention in the inner pipe. Figure 3b shows the valve 10 in open position and a line cleaning pig 11 entering the main through inner pipe 8 at inlet 2. Figure 3 c shows the pig 11 having passed through the filter screen area 9 together with collected particles. After pigging, the valve 10 is closed and the apparatus returns to its filtering condition.

Prior to pigging, the apparatus can be backwashed by reversing the flow through the filter screen 9 from outlets 4 and 5 to free/loosen any build-up of sediment/solids that may become caked on the inner surface of filter screen 9. The backwashing can also take the form of dedicated connections on the vessel 1 supplying washing media from the outer to inner pipe.

The system diagram in figure 4a illustrates a typical use of the apparatus according to the invention as described previously as a process solids protection device prior to the well stream entering a processing unit. The hydrocarbon production from a well 21 enters a header 22 and flows to a solids filter vessel 1 , the valve 10 and a valve 20 are closed,. The hydrocarbon stream then enter the solids filter vessel 1 and passes through the filter screen 9 and flow out, subsequent to particle entrainment, into outlets 4, 5 and 7 through a pipe 13 and into a process unit 12. In the process unit 12 the processed hydrocarbons then leave to their various routings, as water through a pipe 14 to an injection well 22, as oil in a pipe 16 downstream of the valve 10 and into a flow line 18, and as gas through a pipe 15 into a flow line 17.

The flow lines 17 and 18 are routed to and from a topside unit 23. The flow lines 17 and 18 are the main pigging lines in addition to the header 22 and the filter screen 9. As previously described, the pigging operation from the topside unit 23 is executed by closing valves 24, 25 and 26. Valves 19, 20 and 10 are opened, allowing the cleaning pig (not shown in figure 4a) from the unit 23 to round trip pig clean the whole system flow lines 17 and 18, the header 22 and the filter screen 9.

The system diagram of figure 4b illustrates a typical use of the apparatus according to the invention as a process solids protection device installed on or in a topside manifold system between incoming riser lines 17b and 18b and separator system feed line. Here the pigging line can extend from a pig launcher 100 to a pig receiver 101, or alternatively a round trip pigging route as described for figure 4a.

The apparatus according to the invention will now be explained when used as solids filter screen as a stand alone separator or integral part of a separator or similar, referring to examples in figures 5a₅ b, ab, c, d, e, 6a, b, c, 7a, b, c, d, e and f.

Figure 5a illustrates an example of the use of the apparatus according to the invention as a stand alone long small diameter separator or pipe separator were the main phase separation can take place in an inner cavity defined by an inner pipe section 34.

Production fluids are supplied through an inlet 32. Bulk gas is filtered for solids through a filter screen 35 in top of the inner pipe 34 and is then routed out through a gas outlet 37 from the outer vessel 31. Bulk water is filtered for solids through a filter screen 36 in the base of the inner pipe 34 and routed out through a water outlet 38. The remaining bulk oil is passed through the inner pipe 34 to an end outlet 33 from the separator.

Alternative, typical cross-sections of the apparatus of figure 5a are described in figures 7a-f. These will be described more in detail below. The apparatus allows for full pig cleaning of solids through the inner pipe 34 that are accumulated on the inner surface of filter screen 36, as described above. The general design of the inner pipe may be substantially as described in Norwegian patent 316428, except that the inlet and outlet arrangements are formed as a through pipe with uniform cross-section adapted for pigging.

Figure 5b illustrates an example of the use of the apparatus according to the invention, which is similar to the example of figure 5a, but is a typical end section of a long small diameter separator or pipe separator were phase separation takes place in the inner pipe section 34. Water is filtered for solids through filter the screen 36, accumulates in the outer vessel 31 and is drawn off through 38. A typical example of the use here with a pipe separator would be when applied to the apparatus described in WO 2004/016907. The apparatus allows for full pig cleaning of solids through the inner pipe 34 that are accumulated on the inner surface of filter screen 36. Figure 5ab shows an apparatus similar to figure 5a and 5b but with some variations. An isolation valve 40, which is closed during separation, is situated downstream of the apparatus at an end 33. Separated oil and/or gas is routed through a pipe 39 downstream of the valve 40. Separated water is filtered through the filter screen 36 and routed out through the water outlet 38. When pigging is to be performed, the valve 40 is opened allowing the pig to pass through the inner pipe 34.

Figures 5c and 5d illustrate variations on the function of the apparatus shown in examples 5 a, b and ab. The piping or vessels main runs 44a and 44b upstream and downstream of the apparatus may be elevated to form a sump or water lock at the position of the separator. This has the effect of raising the interface level between the two different phases, water 47 and oil/gas 48, allowing the water phase 47 to accumulate in greater volume for draw off through a water outlet 46 after being filtered through a filter screen 45. Reference is made here to WO 2004/016907 Al, were elevating the downstream pipe section of a pipe separator or remainder of a long separator allows for the lighter phase to accumulate free from most of the water phase. The apparatus according to the present invention allows for full pig cleaning of solids that are accumulated on the inner surface of the filter screen 45 through the inner pipe 44a-b.

Figure 5d illustrates a variation on the function of the apparatus shown in the example in figure 5 c, were some of the lighter phases can be drawn off the section 44a through a pipe 50 before entering the pipe section 44b. The lighter phase may also be drawn of through the pipe 50 and routed to another location other than to the pipe section 44b.

Figure 5e illustrates a further variation on the function of the apparatus were a solids filter screen 55 forms a part of an inlet 52 to a separator 51. A feed pipe 54 passes through the separator 51 with an isolation valve 59 downstream of the separator 51. Fluid entering the separator via the inlet 52 is filtered for solids through the filter screen 55 and is routed back to the end of the inner part of the separator via a pipe shroud 56 (see detail on top of figure 5e), thus allowing for the fluid to be filtered over a long surface length in the separator and then be routed back to one end for the full separators full retention time. Although it shown in figure 5e as a single pipe inlet device the apparatus may also form a part of another inlet device. The various separated phases leave the separator via outlets 57 (oil & gas) and 58 (water). Shown here is a common outlet for oil and gas, but these may also be separate.

The apparatus allows for full pig cleaning of the solids that are accumulated on the inner surface of filter screen 55, through the inner pipe 54. The apparatus according to the invention as shown in fig 5 e could be used to retain large solids allowing fines produced to pass through the filter screen 55 and follow the process streams out of the separator (or be handled by the separators sand cleaning system if installed).

Figures 6a and 6b illustrate that the placement of the inner pipe and filter screen 62 and may be either concentric or eccentric to the outer pipe/vessel 61, and/or the inner pipe/filter section 62 may vary its alignment relative to the outer pipe/vessel at one or several positions along the length of the pipe/vessel 61. Figure 6c illustrates the filter section of the inner pipe 61.

In all cases shown in figures 1 through to 7 the said apparatus may be equipped with back washing facilities by applying pressure and flow from the outer to the inner volumes reversing the normal flows direction through the filter screen. Various other utility systems may be added or used on the said apparatus e.g. mixing and chemical dosing, purging, venting, draining, heat tracing and insulation etc as would be readily understood by a person of skill. It is also conceivable to install nozzles or dedicated piping on the inside of the outer vessel to wash loose any solids that may have got through the filter and accumulated on the inside of the outer vessel.

Figures 7a to 7f show some examples of cross-sections of the apparatus according to the invention when used in phase separation, showing various filter screen area placements in the inner pipe, enabling the different phases to be filtered for solids.

Figure 7a and 7b show the inner pipe filter screen 73 placed in the upper quadrant of the inner pipe 71, allowing oil and or gas to be filtered and then being routed through the top of the outer area via an outlet 77 (figure 7a) or through the bottom of the outer area via an outlet 84 (figure 7b). In both figures 7a and 7b the heavier phase, water 74, is routed further to another area (not shown in figures 7a and 7b) The heaviest solids are accumulated in the bottom of the inner pipe 71, which is not equipped with a screen, and eventually removed by pigging the line.

Figures 7c and 7d show the inner pipe filter screen 72 placed in the bottom quadrant of the inner pipe 71, allowing water 74 to be filtered into the area 78, between the inner pipe 71 and the outer vessel 70, and then routed to an outlet 84, as shown in figure 7c, or as shown in figure 7d, to two separate outlets 80 and 81. These outlets are separated by a dividing plate 79. Alternatively, the outer volume 78 can be fully divided by two plates (one plate 79 below the inner pipe 71 and one (not shown) above the inner pipe) forming two separate outer volumes. In this case one side can be backwashed while the other side produces filtered water.

Figures 7e and 7f show some possible configurations were the phases 74 and 75 in the inner pipe are filtered through screens 72 and 73, respectively, relevant to the position of the phases in the inner pipe. The separated phases in the outer areas 76 and 78 may be segregated by plate segments 85 and routed out through their relevant outlets 77 and 84. Whichever configuration is chosen it will still allow for the inner pipe to be mechanically cleaned by pigging.

Claims

P a t e n t k r a v

1.

Apparatus for filtering of solids suspended in fluids, comprising a screen (9), adapted to allow fluid to pass there through and preventing particles larger than a specific size from passing there through, the screen forming at least a part of a wall (8) defining a cavity, the screen (9) having an inner surface facing the cavity, the inner surface being substantially smooth with a plurality of openings, characterised in that the cavity has a substantially uniform cross-section over the length of the screen and that the screen at either end is coupled to a channel having a cross-section with at least the same dimension as the cross-section of the cavity, to allow for through pigging of the screen, on order to remove solids accumulated on the inner surface of the screen.

2. Apparatus according to claim 1, character i sed in that the openings in the screen (9) comprises an entrance opening facing the inner cavity and an exit opening facing away from the inner cavity, the entrance opening being of a smaller dimension than the exit opening.

3.

Apparatus according to claim 1 or 2, characterised in comprising an outer vessel or pipe (1) with at least one inlet and at least one outlet (2, 3, 4), the vessel or pipe (1) enclosing an inner pipe (8) comprising the wall with the filter screen, The inner pipe (8) passing through the outer vessel or pipe (1) and forming two ends (2) and (3) of the inner pipe (8) outside of the outer vessel or pipe (1).

4.

Apparatus according to claims 3, characterised in that the inner pipe (8) and filter screens (9) are situated concentric to the outer pipe (1).

5.

Apparatus according to any of the preceding claims 3 or 4, characterised in that the inner pipe (8) and filter screens (9) are situated eccentric to the outer pipe

(1).

6.

Apparatus according to any ofthe preceding claims, char acteri sed in that the filter screens (9) are constructed of a wedge type profile, having a wedge base facing the inner cavity.

7.

Apparatus according to any ofthe preceding claims, characterised in that the outer vessel or pipe (1) comprises means for backwashing the filter screen (9).

8.

Apparatus according to any ofthe preceding claims, characterised in that it is installed as a primary and or secondary solids/sand screen filter to a production well head, production well template production well manifold and/or a processing unit.

9.

Apparatus according to any ofthe preceding claims, characterised in that it is a stand alone separator or a part of or multiple parts of another separator.

10. Apparatus according to any of the preceding claims, characterised in that the apparatus and/or filter screen (9) is removable and/or re-installable or is a part of another apparatus that is removable and or re-installable.