Abstract:
The invention relates to a collecting tank for multi-phase mixtures from a hydrocarbon source, having at least one inlet ( 20 ) for introducing multi-phase mixtures into the collecting tank ( 10 ), and having a plurality of outlet connectors ( 30 ), which can be connected to pumps ( 3 ) via which multi-phase mixtures are pumped, the outlet connectors ( 30 ) being assigned inwardly directed internals ( 40 ) which project upwards beyond the collecting-tank base ( 11 ) and have a first, upper opening ( 42 ) and a second, lower opening ( 41 ), wherein the flow cross section of the lower opening ( 41 ) is smaller than that of the upper opening ( 42 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a collecting container for multi-phase mixtures from a hydrocarbon source, having at least one inlet for introducing multi-phase mixtures into the collecting container, to a system comprising at least one collecting container and a plurality of multi-phase pumps connected thereto, and to a method for separating and dividing up a multi-phase mixture among a plurality of multi-phase pumps. 
     BACKGROUND 
     When extracting multi-phase mixtures, in particular of hydrocarbons, the extraction conditions fluctuate. Hydrocarbons are generally extracted in mixtures, in which different aggregate states are present. In addition to a solid phase, for example sand, liquid phases and gas phases are present. These phases are present in different proportions, wherein the composition of the multi-phase mixtures varies within a wide range so that it is impossible to predict when, and for how long, each composition of the multi-phase mixture will be extracted. Therefore, it may be that, after a relatively long period of extraction with a predominantly liquid phase fraction, a gas phase fraction is extracted for a long period, sometimes until gas phases are extracted exclusively. The moment at which the fractions of a multi-phase mixture will be extracted, as well as the duration of said extraction and the ratio of said proportions, are thus unknown, which hinders the extraction process. 
     The capital outlay when developing hydrocarbon sources is extraordinarily high. In so doing, it may be necessary to provide a plurality of delivery pumps, for example if the volumes to be conveyed cannot be transported expediently using a particular pump size, for example because the required pump sizes are not available, or because the sizes adapted to the demand are not expedient from a technical or economical point of view. 
     Young production fields only develop their maximum production after a few years, and therefore there is the problem that a relatively small pump size may be sufficient when extraction is begun, which can lead to problems over the course of further operation however when the pump size suitable at the start is no longer sufficient. There is thus the possibility of operating a plurality of pump units, which are arranged in parallel, so as to provide variability of the delivery rate in addition to a desired redundancy and fail-safe operation. From a logistical point of view, it may be expedient to establish just one pump size and to satisfy the different production demand by means of a different number of parallel multi-phase pumps or by means of a corresponding adaptation of production to the individual multi-phase pumps. 
     Redundant arrangements of multi-phase pumps reduce the risk of failure, in particular the risk of total failure. In the normal case, the use of speed-variable multi-phase pumps allows wear-reducing operation at reduced speed with a corresponding design, whilst, in the event of failure of a pump, the remaining assembly or the remaining assemblies can largely compensate for the production failure with an increased operating speed. 
     As mentioned above, when extracting hydrocarbons, the multi-phase mixtures consist of different substances in different aggregate states, for example water, possibly with sand additions, gas condensates, crude oil, natural gas or associated petroleum gas, which have specific weights, which deviate from one another. If multi-phase mixtures are to be divided up among a plurality of multi-phase pumps, there is the problem of ensuring uniform division, since the heavy substances such as liquids preferably fall into exits arranged at the bottom and preferably flow past exits arranged to the side. In the case of branchings, there is thus the problem that a uniform division of the extracted components has to be ensured so as to thus prevent an increased temperature load for pumps charged predominantly with gas fractions. 
     One possibility for achieving a uniform division of the delivery of the product flow lies in a horizontally, strictly symmetrical arrangement of the distribution points. This has the disadvantage of a high spatial requirement, high weight and associated high costs, and a 2 x  number of pumps must also always be provided so as to achieve a uniform division. The failure of a pump, arrangement of different pump types, the disconnection of individual pumps or other interruptions leads to non-uniform distributions, which may lead to overloading of individual multi-phase pumps. 
     SUMMARY 
     The object of the present invention is to ensure the most uniform and long-lasting supply possible of multi-phase pumps with a sufficient liquid volume so as to reduce the temperature load, even during long periods of gas phase extraction. 
     In accordance with the invention, this object is achieved by a collecting container having the features in the main claim, a system having the features in the second independent claim, and a method having the features of the third independent claim. Advantageous embodiments and developments of the invention are presented in the dependent claims, the description and in the figures. 
     In the case of the collecting container according to the invention for multi-phase mixtures from a hydrocarbon source, having at least one inlet for introducing multi-phase mixtures into the collecting container and a plurality of outlet connectors, which can be connected to pumps, via which multi-phase mixtures are pumped, the outlet connectors are assigned inwardly directed internals which project upwardly beyond the collecting container base and have a first, upper opening and a second, lower opening, wherein the flow cross section of the lower opening is smaller than that of the upper opening. As a result of the internals provided in the collecting container, the different properties in terms of the specific weight of the liquid phase and of the gas phase, in particular of crude petroleum and natural gas, are utilized so that a metering effect and a desired product distribution are achieved. The gas phase can flow through the upper opening relatively unhindered, whilst the liquid phase settling at the base of the collecting container is collected and conveyed through the relatively small, lower opening, only slowly, to the pumps, which transport away the multi-phase mixtures. A common inlet or a number of inlets is/are provided, so that the multi-phase mixture can flow into the collecting container. The multi-phase mixture can flow directly from the bore hole into the collecting container for example. A gravity-induced separation of the gas phase and of the liquid phase takes place in the collecting container. The liquid phase settles at the base of the collecting container, whilst the gas phase distributes above the liquid phase within the collecting container. The gas phase can be conveyed unhindered through the upper, large opening to the individual pumps, which are connected at their inlet side to the collecting container. Likewise, the liquid phase flows unhindered through the upper opening, provided the fill level within the collecting container is high enough, so as to reach the upper opening. A sump, which is filled with liquid phase and possibly solid fractions, forms beneath the upper opening. The sump is drained through the second, lower opening in the internals, which is preferably arranged at the collecting container base or just above the collecting container base. The liquid phase can thus drain from the collecting container through the lower opening and reaches the respective pump, which is connected to the outlet connector. It is thus ensured that liquid phase is discharged uniformly from the collecting container through the respective outlet connectors to the respective pumps over a long period, that is to say until the liquid sump has been emptied. As a result of the provision of the minimal required liquid volume over a long period, it is ensured that thermal stability of the pumps connected to the outlet connectors is ensured, even during the extraction exclusively of the gas phase through the inlet pipe. The compression heat, for the gas phase, generated within the pump is primarily transported away via the liquid phase supplied to the pumps. In the pumps, which are designed as screw-type pumps for example, the gaps present between the screw spindles are also lubricated and sealed. The temperature stability, tightness of the screw spindles with respect to a push-back of the extracted product and the service life of the pumps are thus increased. 
     The outlet connector or the outlet connectors is/are preferably oriented downwardly in an inclined manner or vertically upwardly. The transporting away of the liquid phase through the outlet connectors is thus facilitated. In addition, the internals can be arranged at, or in, the outlet connectors so that the lower openings in the internals can thus be assigned easily to the respective outlet connectors and therefore to the respective outlet channels and the pumps connected thereto. 
     The collecting container may preferably be designed as a collecting pipe or collecting tank, although alternative embodiments of the collecting container are possible. 
     Due to the arrangement of the internals such that the upper opening thereof is oriented vertically upwardly, it is basically ensured that only liquid phase above the level of the opening can pass through the upper, large opening. 
     So as to change the fluid flow through the lower opening, said lower opening can be assigned an adjustable throttle device or closure device, via which the flow cross section can be reduced or the opening can be closed. In principle, it is also possible for the upper opening to have a throttle device or closure device so as to block certain outlets or to influence the flow behavior in a desired manner. 
     The internals can be mounted displaceably and/or rotatably in the collecting container so as to adapt to different requirements. A displaceable mounting of the internals may lead to a reduction or increase in the liquid level; the same is true of a rotatable embodiment of the internals in the collecting container. With an inclined arrangement of the internals, the level or the cross section of the lower opening for example can be changed as a result of rotation; the same is true of a displaceable arrangement of the internals within the collecting container. 
     The internals can be designed as inserts, for example basket-like adjustable inserts, or as hollow sections, baffle plates or deflector plates so as to achieve a formation of a liquid sump in the collecting container and controlled discharge through an opening within the internals in the vicinity of the collecting container base. 
     The internals can be assigned adjustment devices, via which the free flow cross section of the upper and/or lower opening in the internals can be varied from outside the collecting container. As a result of this adjustment device, it is possible to change the parameters during operation of a delivery device, for example so as to disconnect individual pumps, supply greater volumes of liquid phase or to reduce the volume of supplied liquid phase. 
     The collecting container is preferably designed in a closed manner so as to use the internal pressure to assist the extraction process. Pressure relief valves can be arranged so as to prevent failure of the container structure in the event that a maximum pressure is exceeded. 
     Shut-off devices may be arranged on the internals, outlet connectors and/or outlet pipelines so as to shut off individual pumps, which are arranged downstream of the collecting container. These pumps can thus be serviced without difficulty. It is likewise possible to adapt the delivery rate to the desired production by shutting off individual delivery pumps. 
     Separation devices can be arranged in the collecting container and separate the gas phase from the liquid phase. These separation devices may be diverting devices, labyrinths, separators or flow obstacles. The separation device may likewise be formed by an expansion of the flow cross section so as to facilitate gravity-induced separation. Flow rates of at most 0.5 m per second are preferably achieved in the collecting container and corresponding devices for maintaining this flow rate of the multi-phase mixture can be provided, for example throttles or the like. The maximum rate can be adjusted by limiting the flow rate on the inlet side of the storage container. So as to maintain this flow rate, the collecting container is to be dimensioned so as to be accordingly large. 
     The outlet lines, which lead from the outlet connectors to the pumps, in particular multi-phase pumps, are dimensioned in such a way that relatively high flow rates of at least 3 m per second prevail, so as to prevent separation within the pipeline. 
     The system according to the invention comprising a collecting container and a plurality of multi-phase pumps connected thereto enables parallel operation with high material flows with use of standardized sizes of the connected multi-phase pumps and variability in the production. As a result of redundant pumps, which are not operated at their output limits, the availability of the system as a whole can be maximized, since, if a pump connected in parallel fails, the failure can be assumed by the other pumps. 
     In addition to the direct conveyance through the pumps connected in parallel on the outlet side, it is possible for at least one inlet multi-phase pump to be arranged on the inlet side of the collecting container, wherein a line from the collecting container to the inlet side of the inlet multi-phase pump is laid from at least one connector so as to enable recirculation of a liquid phase on the inlet side of the pump. The thermal stability of the inlet multi-phase pump can thus be increased. 
     A control device can be provided, which is coupled to sensors and adjustment devices arranged on the multi-phase pumps and adjusts the flow cross section of the lower opening on the basis of the sensor values. For example, if excessively high temperatures are determined at individual multi-phase pumps, an increased liquid proportion can be supplied to the multi-phase mixture to be conveyed by increasing the flow cross section of the lower opening so as to remove thermal energy accumulating within the multi-phase pumps from the pump system. Alternatively or simultaneously, the gas fraction can be reduced so as to reduce the volume of newly generated compression heat. 
     In accordance with the method for separating and dividing up a multi-phase mixture among a plurality of multi-phase pumps, the multi-phase mixture is conveyed into a collecting container and is separated by means of separation devices, wherein the separated liquid phase is supplied in a metered manner to individual multi-phase pumps. The collecting container may be formed as a separate collecting container, into which multi-phase mixtures are introduced directly from a source. Alternatively, the multi-phase mixture is introduced from one pump into a separate collecting container and is then pumped off via further pumps, and lastly it is possible for the collecting container to be designed as part of a multi-phase pump and for separated liquid phase to then be supplied from this collecting container to other pumps in a metered manner. It is thus possible, via transverse connections of pumps arranged in parallel, to ensure a minimal supply of liquid phase if sufficient liquid phase is collected within one or more pumps and is then conveyed in a controlled manner to other pumps, which deliver a smaller liquid fraction. The liquid fraction to be delivered can be established via sensors so that the supply of the separated liquid phase from the delivery side of the pump to the intake side of the requesting pump is regulated on the basis of sensor data, which include the temperature, the gas or liquid volumes, pressures and the like for example. 
     The multi-phase mixture can be separated in the collecting container by reducing the flow rate of the inflowing multi-phase mixture, for example by increasing the flow cross section. Gravity-induced separation of liquid phase and gas phase thus takes place. 
     Separated liquid phase can be supplied to a pump on the inlet side arranged before the collecting container in the direction of conveyance so that recirculation takes place. The volume of the supplied liquid phase can be set in accordance with sensor parameters, for example on the basis of the delivered liquid phase or on the basis of temperature values. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the invention will be explained hereinafter in greater detail on the basis of the figures, in which: 
         FIG. 1  shows an overview of an extraction facility; 
         FIG. 2  shows an illustration of a tubular collecting container; 
         FIGS. 3 to 6  show sectional views of different collecting containers; 
         FIG. 7  shows a barrel-shaped collecting container; 
         FIG. 8  shows a sectional illustration with an inclined outlet connector; 
         FIG. 9  shows a sectional illustration with a vertical outlet connector; 
         FIG. 10  shows a sectional illustration with valves; 
         FIG. 11  shows a sectional illustration with closure and metering devices; and 
         FIG. 12  shows a circuit diagram of an extraction facility. 
     
    
    
     DETAILED DESCRIPTION 
     An extraction facility for multi-phase mixtures comprising a plurality of multi-phase pumps  3  arranged in parallel is illustrated in  FIG. 1 , said pumps each being arranged on a base. The multi-phase pumps  3  have an inlet  2  and an outlet  7 . A line leads from the outlet  7  to a collecting container  15 , from which the collected mixture, which is collected by the multi-phase pumps  3 , which are generally designed as screw-type pumps, and is discharged through an outlet  17 . The inlet side  2  of the multi-phase pumps  3  is connected to outlet channels  30  of a collecting container  10 . This collecting container  10  has an inlet  20 , through which the multi-phase mixture, generally a mixture of water, sand, petroleum oil, natural gas and associated gases, passes. The inlet  20  may lead directly to a borehole, and a pump device may be arranged upstream of the inlet if necessary. Should the multi-phase mixture not require pumping due to its natural pressure, a bypass  16  is provided, which directly connects the inlet  20  to the outlet collecting container  15 . 
     Internals are arranged in the collecting container  10  and are assigned to the respective connectors with outlet channels  30 , via which a metered liquid supply to the individual pumps  3  is ensured. The collecting container  10 , also referred to as an inlet header, collects the multi-phase mixture originating from the source and distributes it uniformly among the individual multi-phase pumps  3 . In the exemplary embodiment illustrated, the inlet collecting container  10  is aligned substantially horizontally and is designed as a pipe so that gravity-induced separation of the individual components of the multi-phase mixture takes place. The heavier fractions, that is to say solids and liquid phases, are collected on the base of the collecting container  10 , whereas the lighter components collect above the liquid phase and the solid phase. 
     A collecting container  10  is shown in isolation in  FIG. 2 . The collecting container  10  is provided in the form of a tubular main body with an inlet  20 , which is designed as a 90° connector in the illustrated exemplary embodiment, and with a plurality of outlet connectors  30 , which lead to the multi-phase pumps. The collecting container  10  is constructed in a substantially modular manner and provides a tubular main body, at the ends of which screw flanges are provided. The outlet connectors  30  are arranged in the tubular body between the screw flanges, and each of said outlet connectors  30  is arranged opposite an access flange  31 , via which an insert for example can be inserted and aligned in the outlet connector  30 . The inlet  20  can either be welded or screwed to the inlet connector. The inlet  20  may be provided as a T-piece with screw flanges, so that it can be screwed between two pipe sections of the collecting body  10 . Due to the screw design, practically any number of outlet connectors  30  can be connected in parallel to one another, and therefore a correspondingly large number of pumps can be connected to the collecting container  10 . It is likewise possible to provide inlets  20  at various points, said inlets being easily screwed between two pipe sections. 
     The course of flow of the multi-phase mixture is suggested by the arrows: the upper arrow indicates the inlet of the multi-phase mixture through the inlet  20 , and the lower arrows, which are assigned to the outlet connectors  30 , indicate the fact that the divided multi-phase mixture is discharged through the outlet connector  30 . In the illustrated exemplary embodiment, the outlet connectors  30  are oriented downwardly in an inclined manner and discharge at the lowest point of the collecting container  10 , such that the entire liquid phase that has settled in the collecting container  10  can be easily transported away through the outlet connectors  30 . 
     A variant of the embodiment of the collecting container  10  is illustrated in  FIG. 3 . The inlet  20  with the 90° inlet connector is rotated through 90°. The multi-phase mixture reaches the collecting container  10  via the inlet  20 , as suggested by the arrow. Devices for influencing swirl may be provided in the inlet  20  so as to distribute the multi-phase mixture as uniformly as possible. 
     Internals  40 , which are assigned to the outlet connector  30 , are arranged within the collecting container  10 , which is designed as a succession of pipe segments. An internal  40  that is a tubular insert is inserted into the outlet connector  30 . The insert is arranged rotatably in the collecting container  10  and has a lower opening  41  and a plurality of upper openings  42 , which each extend above the level of the collecting container base  11 . The insert can be rotated via the access flange  31 . The insert is arranged replaceably within the collecting container  10  so that the geometry can be varied as a result of replacement by another insert. 
     In  FIG. 3 , a further internal  40  in the form of a baffle plate is arranged to the left beside the first outlet connector  30 . The baffle plate is fixed between two screw flanges of the pipe sections. In this case too, a lower opening  41  is provided, which has a smaller flow cross section than the upper opening  42 . The baffle plate can be installed in different positions between the two pipe sections so as to set the level of the liquid sump between the baffle plate and the inlet  20 . 
     In  FIG. 3 , a further outlet connector  30  is provided to the left beside the baffle plate and has an internal  40  that is a rotatable insert, which likewise has a lower opening  41  and a plurality of upper openings  42  with a larger diameter than the lower opening  41 . The insert  40  can be rotated externally via the outlet connector  30  so that the position and, if necessary, the diametrical cross sections of the openings  41 ,  42  can be adjusted. 
     A further baffle plate, as an internal  40 , is shown to the right beside the inlet  20  and has an upper opening  42  and a lower opening  41 , which leads to an outlet connector  30 . Due to the embodiment of the collecting container  10  according to  FIG. 3 , it is possible to store within the collecting container  10  a liquid sump, which at most reaches the height of the upper openings  42 . Depending on the dimensioning of the lower openings  41  and the volume of the collecting element  10 , it is ensured that only a small amount of liquid is removed through the outlet connectors  30  over a relatively long period, such that the pumps connecting to the outlet connectors  30 , in particular screw-type multi-phase pumps, are always provided with a minimal amount of liquid by means of the material flow. This minimal amount of liquid seals the design-induced gaps between the delivery elements in the screw-type pumps. This seal is necessary so that the pumps can convey gas, which would otherwise flow unhindered through the gaps. Furthermore, the minimal liquid flow is used as a coolant to remove the compression heat, generated during the gas conveying process, from the pump. 
     A variant of the invention is illustrated in  FIG. 4 . A vertically oriented partition plate  50  is arranged within the collecting container  10 . A swirl influencing device  21  can be provided in the inlet  20 . The vertical partition plate  50  is used for a first division of the multi-phase flow entering through the inlet  20 . A first division of the multi-phase flow is thus undertaken to the right and left of the longitudinal extension. Outlet connectors  30  are arranged at the lower end of the collecting container  10  on either side of the partition plate  50  and each lead to a pump. Compensation windows  52  are provided within the partition plate  50  so as to enable overflow. The compensation windows  52  are arranged in the lower region of the partition plate so that predominantly liquid phase is exchanged between the two chambers of the collecting container. In the sectional illustration to the right in  FIG. 4 , it can be seen that connectors protruding in an inclined manner into the respective chambers are provided as internals  40 , which have small bores  41  at their lower end, which is assigned to the collecting container base  11 , the minimal liquid flow being supplied via said bores to the respective pumps. The upper opening  42  is formed by the diameter of the connector. 
     A further variant of the invention is shown in  FIG. 5 . The internals  40  on either side of the inlet  20  provide an upper opening  42  oriented vertically upwardly and a lower bore  41  arranged in the region of the collecting container base  11 . Internals  40  that are baffle plates are arranged on either side beside the first outlet connector  30  and likewise have an upper opening  42  and a lower opening  41 . A further outlet connector  30  is arranged to the right beside the right-hand baffle plate and leads to a further pump. The baffle plate is thus assigned to the outlet connector  30  arranged to the right and allows only a metered volume of the liquid phase to pass through the lower opening  41  and reach the right-hand outlet connector  30 . 
       FIG. 6  shows a further variant of the invention, in which a plurality of outlet connectors  30  is provided. The outlet connectors  30  are oriented upwardly and are mounted rotatably on the collecting container  10 . Due to the possibility for rotation, the height of each outlet connector can be adjusted by means of an integrated thread  45  formed on the outer surface of the connector  30 . The height adjustment is suggested by the double-headed arrows. The left-hand outlet connector  30  has a 90° angle section as an internal part, and the inlet side is closed by a plate, which has a lower, small opening  41  and an upper, large opening  42 . A sump within the collecting container  10  can also be formed as a result of such an embodiment. The further the internals  40  are moved downwards, the more of the liquid phase that has settled on the collecting container base  11  can be discharged. 
     The right-hand outlet connector  31  is likewise mounted on the collecting container  10  so as to be height-adjustable via a thread  45 . A U-shaped connector is formed at the end on the side of the collecting container, and the underside of said connector has a small bore  41 , which is oriented in the direction of the collecting container base  11 . The larger opening  42  is formed by the open, upwardly directed cross section of the U-shaped pipe. 
     A further variant of the invention is illustrated in  FIG. 7 . A column  90 , which promotes separation of the liquid phase and the gas phase, is arranged after the inlet  20  comprising a device for influencing a swirl. The collecting container  10 , which is formed in a barrel-shaped manner in this instance, has, at its base  11 , five outlet connectors  30  for example, to which internals  40  in the form of curved pipes are connected. The upper opening  42  is oriented horizontally and in this case points toward the outer wall of the collecting container  10 , although a different orientation of the upper opening  42  is, of course, possible. A lower opening  41  is arranged in the internals  40  in the region of the collecting container base  11 . 
     An inclined arrangement of the outlet connector  30  as well as the basket-like internal  40  are shown in  FIG. 8 . The upper openings  42  are designed as elongate slit-like holes, and a lower opening  41  is arranged in the region of the base of the tubular collecting container  10 . Rotation can be implemented externally via an adjustment device  45  so that the orientation of the lower opening  41  can be varied. 
     A variant of the invention with an outlet connector  30  oriented vertically downwardly is shown in  FIG. 9 . The internals  40  have a vertically upwardly oriented upper opening  42  and a lower opening  41  arranged at the bottom of the tubular collecting container  10 . The internals  40  are also designed rotatably in this case so as to change the cross section of the lower opening depending on the position. In the illustrated position, the opening  41  is fully opened, wherein a rotation through 90° causes a maximum reduction of the flow cross section, until closure where necessary. 
       FIG. 10  shows a schematic illustration of a further variant of the invention, in which an adjustable throttle  62  or an adjustable valve is assigned to the internals  40  at the lower openings  41 ; the same is true for the upper opening  42 , wherein the adjustable valves or metering and closure devices  62 ,  72  are merely illustrated schematically. The metering and closure means  62 ,  72  are illustrated outside the collecting container  10  with lines in  FIG. 10 , merely for reasons of improved clarity, but in actual fact the openings  41 ,  42  with the metering or closure devices  62 ,  72  are provided in the internals  40  so that no lines are provided, but the product conveyed from the collecting container  10  instead enters the internals  40  through the openings  41 ,  42  and is transported away through the outlet connectors  30 . 
     A constructive embodiment of the metering and closure devices  60 ,  70 , which are assigned to the openings  42 ,  41 , is shown in  FIG. 11 . The metering and closure devices  60 ,  70  are externally actuatable and, depending on the position of the metering and closure devices  60 ,  70 , the respective opening  41 ,  42  can be closed in part or completely, for example so as to suppress the discharge of the product to be conveyed through the outlet connector  30 . Servicing of the downstream pump is thus facilitated. 
       FIG. 12  shows a schematic arrangement of a plurality of multi-phase pumps  3 , which are connected in parallel between two collecting containers  10 ,  15 . The first collecting container  10  has an inlet  20  and is provided with a total of four outlet connectors  30 , the internals with the openings not being illustrated in the drawing, but being provided in the collecting container  10  nevertheless. The outlet connectors  30  are adjoined by valves  6 , via which the flow rate through the lines, which are connected to the outlet connectors  30 , can be changed. It is possible to close the lines completely. After the valves  6 , the multi-phase pumps  3  are arranged, via which the multi-phase mixture is pumped from the collecting container  10 . From the pumps  3 , a line in which a further valve  4  is arranged leads to a second collecting container  15 , which can also be referred to as an outlet collecting container. The outlet collecting container  15  may also have one or more internals, which have an upper and lower opening, as described above. A return line  5  equipped with a valve  8  leads from the outlet collecting container  15  to the inlet side of the respective pump  3 , which leads to recirculation of separated liquid from the collecting container  15  to the inlet side of the respective multi-phase pump  3 . The minimal amount of liquid required for the pumps  3 , which are generally screw-type pumps, is thus provided such that a sufficient pressure can be built up and the compression heat can also be dissipated, even with large extracted quantities of gas and long-lasting extraction of the gas phase exclusively. An outlet connector  30  leads from the outlet collecting container  15  to a forwarding or further processing device.