NO316108B1 - Devices and methods for downhole separation - Google Patents

Description

The present invention relates to a device for separating well fluids according to the preamble to claim 1 and method for the same according to the preamble to claim 16

When producing hydrocarbons from underground wells, water will be produced in addition to the hydrocarbons. The water usually has a higher density than the hydrocarbons and therefore tends to collect in the lower part of the borehole, and a layered flow pattern will form. Water will also as a result of gravity, flow at a lower rate than the hydrocarbons in inclined wells In some sections of the well, it may even flow downward

Most wells will see an increase in water production late in their production period. Older fields therefore typically produce more water than hydrocarbons. Consequently, one of the industry's biggest challenges is handling these enormous amounts of produced water

A particularly challenging aspect of this problem is the fact that most of these older wells cannot bear the costs of new drilling or a full well overhaul. Affordable modifications would therefore be the ideal solution. Most of these wells have many horizontal sections, with the result that downhole horizontal separation based on natural fall cannot be carried out A separation system that can be used in an awiks well would therefore be of great interest

There are two important prior art methods for downhole separation

• the cyclone-based system, which has been known for quite some time, has so far been a limited commercial success due to questionable operational reliability, and • separator systems based on natural fall, where low-flow systems, dual-action pumping systems (DUAL Action Pumping System (DÅPS)) that handle less than 200 m<3>/d, has been tried with mixed results, while high-throughput systems have not yet found any commercial use. to Schlumberger, described in GB 2 326 895, in addition to a variant of this associated ABB, described in Norwegian patent application 2000 0900

The basic concept behind the downhole separation system described in WO 98/41304 is to regulate the flow rate of formation fluid in a horizontal section of the well to such a level that stratification is achieved. The separated oil is allowed to flow freely to the surface, provided there is sufficient bottomhole pressure (otherwise gas lift or other artificial lifting methods are used) A fire pump is used to inject the released water into a suitable area

The downhole separation systems based on natural fall according to GB 2 326 895 and NO 2000 0900 are suitable for inclined boreholes The system according to GB 2 326 895 is similar to that in WO 98/41304, with the exception that two outlet pipes are proposed, where one takes the oil and the other the secreted water A sensor placed near the outlet openings will be used to regulate the flow rate Compared to WO 98/41304 it is claimed that this system works at slopes of 0 - 50 degrees The system according to NO 2000 0900 is also claimed to work in inclined wells where the heavy fluid component (water) may be separated from the incoming fluid through openings in a pipe and in a second channel formed between the outside of this pipe and the well bottom

Such systems will require layered flow patterns in the separation chamber to work Oil, which is lighter than water, will flow upwards in the top layer and reach the oil outlet Water will flow at a lower speed or flow in a counter-current direction inside the separation chamber (depending on the angle and the total amount of flow through) and is captured by the water outlet or the drainage openings. The highest permissible flow rate between oil and water is a critical parameter when it comes to determining the total capacity of such a system. When this flow rate exceeds a certain maximum value, the fluids will be mixed again by the interface, and the separation will break down

However, the advantage lies in the ability to operate in an inclined borehole

During the spring/summer of 2001, the present applicant carried out investigations with the aim of establishing a new downhole separation device which could, for example, be suitable for the modification of old wet wells

The following criteria were laid down as a basis for a possible downhole separation system for the modification of such old wet wells

1 No requirement for a new voucher

2 Must fit into standard foundation pipe dimensions 7" and 9%'*

3 Must work in inclined wells

4 If possible, avoid rotating equipment (pump, compressor) in the well

5 Separated phases (hydrocarbons and water) are led to the surface, alternatively water is led to an underground low-pressure formation without the use of a pump

6 Minimal monitoring and regulation down in the well (for simplicity)

7 Separated phases are clean enough to be passed through the 1- and 2-phase separators on the surface

8 Works with all water fractions

9 Accepts high flow rates (typically over 2000 m<3>/day)

There is currently no downhole separation technology that meets these criteria. Cyclone-based, downhole separation technology will not meet criteria no. 7 and 8. Systems based on natural fall and small flow-through volume will not meet criteria no. 5 and 9. Downhole horizontal separation (high flow-through volume) will not meet criterion No. 3 Rotary separators under development will not meet criterion No. 4 Fall-based systems for inclined holes will not meet criterion No. 9 (see below)

Consequently, there is a need to fill these gaps in the technology, as feedback from the market indicates that there is a great need for this type of installation

Based on this, it was decided to carry out a technical evaluation of the Counter-current Separation (CS) principle (similar to that described in GB 2 326 895 and NO 2000 0900), which depends on an inclined borehole to work The system is based on separation through natural fall, but differs from WO 98/41304 in that water is directed in the opposite direction to the oil. Gravity will cause the water to collect at the bottom of the well, where an outlet pipe or pump is arranged to deposit this to the surface or in an injection zone. Compared to WO 98/41304, there will be a significant shear rate between the oil and water phases. Experiments have shown that this will be a limiting factor for the total capacity of such a system

The tests showed that to be effective, the flow rate in the borehole would have to be reduced to around 10 - 20% of the outlet suction from a normal high-thickness reduction well. Consequently, the separators according to GB 2 326 895 and NO 2000 0900 will only be useful for wells with lower flow rates

In order to overcome this limitation, the present invention prescribes that the well stream inlet comprises an upper well stream inlet and a lower well stream inlet, where said upper well stream inlet is located at a higher mv than said lower well stream inlet

In this way, the pre-separation of the well fluids that naturally takes place in the well is utilized, before the fluids flow into the separation chamber. The hydrocarbon-rich part of the well fluid flows into the higher opening and the water-rich part of the well fluid flows into the lower opening

The invention as stated in the following claim 1 will provide one or more of the following advantages

• Increased overall throughput capacity

• The different cells can be set mn to handle different water fractions (water cut - WC), as the upper cells will probably handle lower water fractions than the

lower units

• Increased overall efficiency, since the upper cells will receive more clean oil and less water, while the lower cells have more clean water and less oil to remove • Can be combined with regulation in the inflow zone to get a better emptying of the reservoir

• Each cell can be adapted for different flow pressures along the borehole

One particularly interesting advantage of such a system is being able to use the control valves in each separation cell to control the inflow zone. This will require that each section of the well that is to be emptied must be isolated from the others by means of gaskets. The main advantage of such a system is that a combination of both balanced and optimal reservoir emptying and improved separator function is achieved

To get an indication of the possibilities associated with CS cells, a simple experiment was set up

A pipe with a length of 7.9 meters and a diameter of 100 mm was designed with an inlet device in the middle section Collecting pipes for oil and water were included in the main pipe The pipe could be tilted to different angles A mixture of oil and water was fed into the middle section Separation and counterflow would take place as described above The oil/water system consisted of Exxol D80 (a non-aromatized kerosene) and fresh water

The following parameter was varied during the experiment

Separation experiments were carried out at angles of between 4 and 47 degrees. The flow-through quantities were increased until no separation could occur at

due to emulsion formation as a result of the dissolution of the interface between

oil and water

The water fraction varied from 27 to 79%

The following observations were made

• High flow rates gave rise to several emulsions

• The separation efficiency was least at the mversion point (approx. 50% WC)

• A jump in the interface level was detected at surface velocities between 0.015 and 0.02 m/s • Addition of emulsion breaker gave an increase in the maximum gj eimorn flow rate that could be achieved before separation ceased

The experiment showed that

• A higher separation capacity could be achieved for streams where oil was the base phase (low WC), compared to streams where hot was the base phase

(high WC)

• The total separation capacity appeared to be fairly constant for WC above the mversion point (in the low WC region)

• The separation capacity increased with increasing slope, up to approx. 36 degrees

• Regulation of the interface between oil and water was more difficult at high angles • The separation capacity was increased through the use of an emulsion breaker (approximately twice the speed at 7 degrees) • A maximum total flow rate (oil + water) was calculated for a 9 <5>/g " foundation pipe separator (ID 222 mm) on the basis of the separation test

The following conclusions can be drawn from these experiments

• Separation can be achieved within a wide range of angles, but angles greater than 5-10 degrees and less than 35 -40 degrees appear to be the most favorable for

countercurrent separation

• The separation efficiency appears to be 50% lower above the mversion point (in the high WC area) than below • The total separation capacity is too low to use a stand-alone unit in a well with a high flow rate

• Active spring regulation is necessary in order to achieve good product quality

• The effect of better separation under well conditions can be illustrated through the 100% increase in efficiency at 7 degrees and the use of an emulsion breaker

According to the invention, a method is also provided in which a separator is placed in a hydrocarbon-producing zone in a well, the zone is blocked off and connected to the separator through an upper well stream inlet Lap and a lower well stream inlet, where the upper well stream inlet is located at a higher mv than the lower

well flow inlet This will also utilize the pre-separation that naturally takes place in a well

By placing separators in several zones in the well and blocking the zones from each other, you can increase the total amount of flow from the well and still achieve good separation. You can also adapt the separators to the relevant conditions for each zone

Although the present invention is mainly aimed at separators and methods for separation in an inclined well, at least some embodiments of the invention can also be used for horizontal wells

The invention will be described below in more detail in an embodiment of the invention, with reference to the accompanying drawings, where

Figure 1 shows a section through a borehole with a separator according to

the invention,

Figures 2a - 2d show the lower part of the separator in Figure 1,

Figure 2a shows the lower part in the same cross-section as in Figure 1,

Figure 2b shows a cross-section along G - G in Figure 2a,

Figure 2c shows the lower part of the separator in a longitudinal cross-section

of the longitudinal section in figure 2a, along B - B in figure 2d,

Figure 2d shows a cross-section along C - C in Figure 2a,

Figures 3a - 3d show the upper part of the separator in Figure 1,

Figure 3a shows the upper part in the same cross-section as in Figure 1,

Figure 3b shows a cross-section along F - F in Figure 3a,

Figure 3c shows the upper part of the separator in a longitudinal section across

the longitudinal section on figure 3a, along B - B on figure 3d,

Figure 3d shows a cross-section along H — H in Figure 2a,

Figures 4a - 4d show the middle part of the separator in Figure 1,

Figure 4a shows the middle section in the same projection as in Figure 1;

Figure 4b shows a cross-section along D-D in Figure 4a,

Figure 4c shows a longitudinal section along B-B in Figure 4d,

Figure 4d shows a cross-section along E - E in Figure 4a,

Figure 5a shows a detailed drawing of the left side of Figure 2c, and

Figure 5b shows a cross-section along C - C in Figure 5b

Below, the term hydrocarbons is used for the desired fluid from the formation. This includes at least oil, but may also include a smaller amount of gas or condensate

Figure 1 schematically shows an embodiment of a separator cell according to the present invention for countercurrent separation in an inclined borehole. The well is drilled through a hydrocarbon-bearing layer (production zone 1). As shown in Figure 1, and as is the case in many situations, a casing pipe 2 delimits the well from production zone 1 Perforations are made through the casing wall (not shown) to allow reservoir fluids to flow into the well Above and below production zone 1, gaskets 3,4 are placed Gaskets 3,4 isolate the part of the well that passes through production zone l and can be placed elsewhere than what is shown in figure 1 Several perforation slots are typically made along the foundation pipe 2 between gaskets 3 and 4 The inflow amount will therefore be distributed over this section Other parts of the perforated foundation pipe can be insulated with gaskets in a similar way

In cases where the separator is located in an open, unlined well section, gaskets can insulate against the rock surface in the open hole. In some cases, a sand screen can be installed to prevent solids from being carried along with the incoming flow. However, the further description will only cover choose the first option, since the functional description will be the same

Since the liquid flow is distributed over a long section outside the separator, the amount of liquid flow per unit length is small, and there will be a pre-separation of the fluids under the influence of gravity. The lightest fluid, more specifically the hydrocarbon fluid, will move upwards and collect in the upper part of the space between the separation chamber and the drainage pipe 2 and in the area towards the seal 4 The heavier fraction, i.e. the water, will move downwards and collect in the lower part of the space between the separation chamber and the drainage pipe 2 and in the area towards the seal 3

The separator has a first inlet opening 131, an upper wall 9 and a second inlet opening 141, a lower wall 10. The adjustment of the inlet openings 13 and 14 and an upper 13 and a lower 14 opening is important in order to take advantage of the pre-separation of well fluids that takes place in the space between the bottom pipe 2 and the separator Hydrocarbon-rich fluid will tend to accumulate in the upper part of the sealed zone between the seals 3 and 4, and water-rich fluid will tend to accumulate in the lower part of this zone The hydrocarbon-rich fluid fluid will thus flow through the upper flow opening 13, and the water-rich fluid will flow in through the lower flow opening 14. The separator has a lower end wall 15 and an upper end wall 16 which together with the upper wall 9 and the lower wall 10 enclose the separation chamber 17

In the embodiment shown in Figure 1, an outlet pipe 7 is arranged near the upper wall 9 and the upper end wall 16. The purpose of the outlet pipe 7 is to lead the hydrocarbons out of the separator. Similarly, an outlet pipe 8 is arranged near the lower wall 10 and the lower end wall 15 The purpose of the outlet pipe 8 is to lead the water out of the separator The hydrocarbon outlet pipe 7 is arranged near the separator's upper wall 9 to capture the hydrocarbons that accumulate near this wall The water outlet pipe 8 is arranged near the separator's lower wall 10 to capture the water that accumulates near this wall

The two outlet pipes 7,8 are preferably designed to capture hydrocarbons and water, respectively, along a length of the pipe which is provided with openings U and 12, respectively. The openings 11 and 12 preferably have an opening area which decreases towards the upper end wall 16 and the lower, respectively end wall 15, so that hydrocarbons and water respectively are extracted in smaller and smaller amounts along the length of the outlet pipes 7,8 to enable coalescence of the smaller droplets in the area towards the end walls 15 and 16. The outlet pipes preferably have a design that is described in detail in the Norwegian patent application no. 2000 1954 (corresponds to PCT/NO01/00156) from the present applicant

The separation of the hydrocarbons and the water will be governed by gravity and the viscous forces in the fluid Final coalescence of dispersed oil droplets will take place in the water column above the lower end wall 15 Correspondingly, the dispersed water droplets will coalesce and sink in the oil column near the upper end wall 16

The separator can be divided (although not necessarily physically) into three parts

A lower part 18 which comprises the lower end wall 15, the water outlet pipe 8 and the parts of the upper wall 9 and the lower wall 10 which are closest to it

lower end wall 15,

an upper part 19 comprising the upper end wall 16, the hydrocarbon outlet pipe 7 and the parts of the upper wall 9 and the lower wall 10 which are closest to it

upper end wall 16,

and a middle part 20 which comprises the inlet openings 13,14 and the parts of the upper

and lower wall 9,10 which is located close to the inlet openings 13,14

The separator will now bra described in more detail with reference to figures 2a - 2d, 3a

- 3d and 4a—4d

Figures 2a - 2d show the lower part 18 of the separator In figure 2a, the lower part 18 is shown in the same cross-section as in figure 1 This shows the parts of the upper wall 9 and the lower wall 10 which are located closest to the lower end wall 15, containing the water outlet pipe 8 The water outlet pipe 8 is connected to a water flow pipe 21 through a control valve 36 and a transition pipe 22 which puts the water outlet pipe 81 in fluid connection with the water flow pipe 21 The heat flow pipe 21 extends through the length of the separator, as shown in, for example, Figure 1

Figure 2b shows a cross section along G - G in Figure 2a This cross section shows the water flow pipe 21 and the water outlet pipe 8, in addition to a hydrocarbon flow pipe 23 which also extends through the length of the separator parallel to the water flow pipe 21

As can also be seen in Figure 2b, the upper wall 9 and the lower wall 10 together form a seam The upper wall 9 goes down to the water flow pipe 21 and the hydrocarbon flow pipe 23, and the lower wall 10 goes up to the two pipes 21 and 23 In practice the upper and lower walls 9 and 10 are made completely in tubular form

Figure 2d shows a cross-section along C - C in Figure 2a and shows the water flow pipe 21 and the hydrocarbon flow pipe 23 placed in the separator chamber 17

Figure 2c shows a longitudinal section of the lower part 18 of the separator, across the longitudinal section in Figure 2a, along B - B in Figure 2d Here both the water flow pipe 21 and the hydrocarbon flow pipe 23 are visible A part of the water outlet pipe 8 and the transition pipe 22 are also visible between 21 and 23

As can be seen in figures 2a and 2c, the water flow pipe 21 is connected to a connection chamber 24 which is located behind the end wall of the separator 15. The hydrocarbon flow pipe 23 is connected to a pipe bend 25 which passes through the obstruction chamber 24. The end of the pipe bend 25 which is farthest from the hydrocarbon flow pipe 23 is located in the middle of the pre-bend chamber 24 The connection chamber 24 and the pipe bend 25 are designed for connecting a connection chamber 24' and a pipe bend 25<*> in a second separator located below the lower part 18

The upper part 19 is described with reference to figures 3a - d The upper part 19 is similar to the lower part 18, with the exception that it is oriented so that the hydrocarbon outlet pipe 7 is located near the upper wall 9, while the water outlet pipe is located near the lower wall 101 the lower part 18 Figure 3a shows the upper part 191 in the same cross-section as in Figure 1 This shows the parts of the upper wall 9 and the lower wall 10 which are located closest to the upper end wall 16, containing the hydrocarbon outlet pipe 7 The hydrocarbon outlet pipe 7 is connected to the hydrocarbon flow pipe 23 through a control valve 37 and a transition pipe 26 which connects the hydrocarbon outlet pipe 7 with the hydrocarbon flow pipe 23. The hydrocarbon flow pipe 23 extends through the length of the separator, as explained earlier. Figure 3b shows a cross section along F - F in Figure 3a. This cross section shows the water flow pipe 21, the hydrocarbon flow pipe 23 and the hydrocarbon outlet pipe. 7 Figure 3d shows a cross-section along H - H in Figure 2a , and shows the flow pipe 21, the hydrocarbon inlet pipe 23 and the hydrocarbon outlet pipe 7, in addition to the transition pipe 26, located in the separator chamber 17 Figure 3c shows a longitudinal section through the upper part 19 of the separator across the longitudinal section in Figure 3a, along B - B in Figure 3d Here both the water flow pipe 21 and the hydrocarbon flow pipe 23 are visible The hydrocarbon outlet pipe 7, control valve 37 and transition pipe 26 are also visible, and partially cover pipes 21 and 23

As can be seen in Figures 3a and 3c, the water flow pipe 21 is connected to a compression chamber 27 which is located behind the separator's upper end wall 16. The hydrocarousel discharge pipe 23 is connected to a pipe bend 28 that passes through the compression chamber 27. The end of the pipe bend 28 furthest from the upper end wall 16 is located in the middle of the connection chamber 27 The connection chamber 27 and the pipe bend 28 are thought to be connected to a connection chamber 27' and a pipe bend 28' in a second separator located above the upper part 19, in a similar way as described for the connection chamber for the lower part

With reference to figures 4a - 4d, a description of the middle part 20 will be given

Figure 4a shows the middle part in the same projection as in Figure 1. The inlet openings 13 and 14 from the well space to the separator chamber 17 are shown near the inlet openings 13 and

14, guide plates 29,30,31 and 32 have been placed. These are intended to prevent the incoming well flow from disturbing the fluids that are already inside the separator, in order to prevent re-mixing of the already partially separated phases

Figure 4b shows a cross section along D - D in figure 4a The openings 13 and 14, the guide plates 30 and 32 and the water and hydrocarbon flow pipes 21 and 23 are shown Figure 4d shows a cross section along E - E in figure 4a Here also are the guide plates 30 and 32 and the water and hydrocarbon spray inlet pipes 21 and 23 shown Figure 4c shows a longitudinal section along B - B in Figure 4d Water and

The hydiokaiboristor intake tubes 21 and 23 are shown. In addition, opening 14 and the guide plates 31 and 32 are shown. As can be seen in Figure 4c, the guide plates 31 and 321 are in reality one plate in which an opening corresponding to opening 14 is designed. The inlet arrangement is very simple. During experiments it proved to be very important to include the guide plates to protect the counterflow separated flow from the incoming fluid The inlet openings 13 and 14 can however have different shapes and also consist of several separate openings in the same area

As shown in Figure 4a, a first level gauge 33 is placed below the inlet openings 13, 14 to measure the highest level of the water phase, and a second level gauge 34 is placed above the inlet openings 13, 14 to measure the lowest level of the hydrocarbon phase. If the highest level of the water phase exceeds the first level gauge 33, the withdrawal of water through the water outlet pipe 8 (shown in figure 1) will have to be increased, and/or the withdrawal of hydrocarbons through the hydrocarbon outlet pipe 7 (shown in figure 1) will have to be reduced If, on the other hand, the lowest level of the hydrocarbon phase falls below the second level gauge 34, the withdrawal of hydrocarbons through the hydrocarbon outlet pipe will have to be increased and/or the withdrawal of water through the water outlet pipe will have to be reduced

Regulation of the flow rate is preferably done using the adjustable valves 36,37 at the two outlets, on the basis of the interface level for oil and water in the middle part of the separator chamber. Distributing the flow rate between the individual separators is preferably done by adjusting the discharge flow from each separator so that the handles a certain proportion of the total flow rate

The connection between two separators according to the present invention will now bh described with reference to figures Sa and 5b

As can be seen in Figure 5 a, which actually shows the same as the left side of Figure 2c, the water flow pipe 211 is the right separator and the hot flow pipe 21' in the left separator is connected to connection chambers 24 and 24' respectively. The connection chambers have the same inner and outer diameter as the separators, and is in reality an integral part of the respective separator walls 9,10 The two connecting chambers 24 and 24' are connected to each other by means of an external sleeve 35 with right and left threads that engage with corresponding threads on the outside of the walls 9,10,9', 10' The connecting chambers 24 and 24' are thus pulled together by turning the sleeve 35. A wedge device (not shown) will ensure that the two separator units are oriented rotationally correctly when matching the hydrocarbon flow pipe 231 the right separator and the hydrocarbon flow pipe 23' in the the left separator is connected to pipe bends 25 and 25<*>, respectively. The opposite ends of pipe bends 25 and 25<*> are located in the middle of the compression chamber 24, 24', as shown in the cross-section in Figure 5b along C-C. The pipe bend 25 extends a small distance m in the compression chamber 24', so that the pipe bends 25 and 25' overlap each other. -/female purchase

Any number of separators according to the present invention can be connected to each other as shown. Thus, the separators can separate well fluids from different zones of the well. The hot flow tubes and hydrocarbon termination tubes will run continuously through the interconnected separators, which will contribute to the flow of the phases by supplying fluid through transition pipes 22 and 26, respectively. In this way, any number of separators can be physically connected one after the other, at the same time that they are operationally connected in parallel

The separator housing is a closed chamber The inlets are located at the top and bottom along a vertical bend This orientation enables pre-separated hydrocarbons to flow into the separator chamber through the upper inlet opening 13 and pre-separated water to flow into the separator chamber through the lower inlet opening 14 The separator must be equipped with an on entermg device to ensure that the hydrocarbon inlet is at the top and the water inlet at the bottom

In order to be able to use a separator according to the invention in a horizontal part of the well, the inlet opening could be placed at one end of the separator and the outlet openings at the opposite end of the separator. The device would involve a co-flow arrangement of the phases, as opposed to a counter-flow arrangement

To make the separator practical to install and ensure easy handling on the drill deck, the construction is preferably characterized by the following

• Each separator cell (CS cell) is made in a standard size and design (so that the total capacity will be the sum of the units) • Engineered to fit the most common of standard funding pipe diameters • The maximum length must be kept within the maximum dimensions that are practical to handle (12 - 14 m) • Connection types must be used which ensure that the CS cells are connected together with the same rotation unit, preferably tip union at each separator section,

rotational orientation of each section using a wedge device

• A device for orienting the unit in the borehole in such a way that the oil inlet appears at the top and the water inlet at the bottom, preferably packing with wedge and CS cell with onentnngshse

Robust and simple construction according to common standards for drilling equipment One-wire system for data transmission for monitoring and control Chain connection of valves and sensors using connecting cables from one unit to the next

Claims (17)

1 Device for downhole separation of well fluids, comprising a separator housing with walls (9,10,15,16) which between them delimit a separator chamber (17), a water outlet (8) and a hydrocarbon outlet (7) from said separator chamber (17), a well flow inlet (13,14) to the chamber (17), which is connected with a small space in the borehole outside the separator housing, characterized in that the well flow passage includes an upper well stream inlet (13) and a lower well stream inlet (14), where the upper well stream inlet (13) is located at a higher level than the lower well stream inlet (14) 2 Device as specified in claim 1, characterized in that the separator is a counterflow separator 3 Device as stated in any one of the preceding claims, characterized in that the well stream flow (13,14) is located a good distance from the water outlet (8) and the hydrocarbon outlet (7) 4 Device as stated in any one of the preceding claims, characterized in that the separator is located in an inclined part of the borehole, that the walls of the separator housing comprise a lower end wall (15) and an upper end wall (16), and an upper wall (9 ) and a lower wall (10), the upper wall (9) and the lower wall (10) extending between the lower end wall (15) and the upper end wall (16), where the water outlet (8) is located near the lower wall (10) and the hydrocarbon outlet (7) are located close to the upper wall (9) 5 Device as stated in claim 4, characterized in that the water outlet (8) is located near the lower end wall (15) (at the end facing downwards from the separator chamber (17)) and the hydrocarbon outlet (7) is located near the upper end wall (16) (at the end facing upwards from the separator chamber (17)) 6 Device as specified in claim 4 or 5, characterized in that an upper well flow inlet (13) is designed in the upper wall (9) and a lower well flow inlet (14) is designed in the lower wall (10) 7 Device as set forth in any of the preceding claims, characterized in that the flow of fluid includes guide plates (29, 30, 31, 32) to prevent the flow of well fluids flowing into the separator chamber (17) from disturbing the fluids already inside the separator chamber (17) 8 Device as stated in any of the preceding claims, characterized in that it further comprises at least one level gauge (33,34) near the well pipe run (13,14), a first level gauge (33) on a first side of the well pipe run (13, 14) and a second level gauge (34) on a second side of the well flow channel (13,14), the second side being at a higher level than the first side 9 Device as stated in any one of the preceding claims, characterized in that the separator housing is provided with a first seal (3) which is located on a first side of the bram flow inlet (13,14), and a second seal (4) which is located itself on another side of the well flow passage (13,14), where the seals (3, 4) block off a zone of the cavity in the area around the separator housing, the zone being in connection with the separator chamber (17) through the wellbore flow passage (13,14) 10 Device as stated in any one of the preceding claims, characterized in that the water outlet (8) and the hydrocarbon outlet (7) comprise a series of outlet openings (11,12) distributed along a length of the separator chamber (17) and dimensioned so that they receive a decreasing amount per unit length towards the downstream end 11 Device as stated in any one of the preceding claims, characterized in that a water flow line (21) and a hydrocarbon flow line (23) extend through the separator chamber (17), where the water outlet (8) is connected to the water flow line (21) ) and the hydrocarbon outlet (7) is connected to the hydrocarbon flow line (23) 12 Device as stated in claim 11, characterized in that the water flow conduit (21) is a pipe 13 Device as stated in claim 11, characterized in that the hydrocarbon flow line (23) is a pipe 14 Device as specified in one of claims 11-13, characterized in that the water flow line (21) and the hydrocarbon flow line (23), at least at one of the ends, end in a connecting part, the connecting part being adapted for connection to a connecting part in further a separator device mng 15 Device as set forth in claim 14, characterized in that the connection part comprises a connection chamber (24,24'), one of the vanrod flow line (21) or the hydrocaibon flow line (23) being in connection with the connection chamber (24,24'), and a pipe part (25 ,25'), where the other of the water flow line (21) or the hydrocarbon flow line (23) is connected to the pipe part (25,25') 16 Method for downhole separation of well fluids, characterized in that a separator is placed in a hydrocarbon-producing zone in a well, the zone is blocked off and connected to the separator through an upper well stream inlet (13) and a lower well stream inlet (14), where the upper well stream inlet ( 13) is located at a higher level than the lower well flow inlet (14) 17 Method as stated in claim 16, characterized in that the separators are placed in several zones, the zones are blocked off from each other, and the respective zones are connected to a respective one of the separators