EP0989306A1 - Compression-pumping system with alternate operation of the compression section and its related process - Google Patents

Abstract

The system giving a set pressure to a mostly liquid or mostly gaseous fluid comprises a compression-pumping section (3) operating alternately, a pumping section (2) supplying energy to a mostly liquid fluid and a phase separator (5) with means (CL) of detecting the level of the liquid-gas interface. The compression is switched to liquid compression for a mostly liquid fluid and vice versa. At least one compression-pumping section (3) operates alternately, with a liquid inlet pipe (9), a gas inlet pipe (8), a gas outlet pipe (12) and a liquid outlet pipe (10). At least one pumping section (2) supplies energy to a mostly liquid fluid with an inlet pipe (7) and an outlet pipe (11). There is at least one device (5) for separating the phases, connected to an inlet pipe (6) for the multiphase fluid and to the liquid outlet pipe (10) from the compression-pumping section. The device has at least one gas outlet (8) and at least one liquid outlet (9) and has means (CL) allowing the level of the liquid-gas interface to be detected. The system also includes means (Vgi, Vli) of controlling the flow of liquid or gas phases through the different pipes, and means of control (15) to change the compression to a liquid compression mode for liquid and vice versa. The system includes at least one recycling line (12a) for returning a gaseous fraction from the compression-pumping section to the separator and/or a recycling line (11a) returning a liquid fraction from the pumping section to the separator. The separator is associated with a helical pipe (20) for separating liquid droplets from gas and a series of discs mounted on a rotating axle (4) which extends through the separator. Process using the above system.

Description

The present invention relates to an alternating compression-pumping system of a multiphase fluid having a composition which may vary over time. The composition can successively present a large quantity of gas, established over a long period of use, but also a low rate of gas over a period of time which can cause engorgement of a separator arranged upstream of the part of the system having the function to communicate energy to the fluid.

The system according to the invention finds its application in particular in the field of oil production.

Although the term "two-phase pumping" is commonly used to refer to a supply of energy to a fluid composed of a liquid phase and a gaseous phase, we will use in the description given below, the term “compression” better suited to designate a transfer of energy to a compressible two-phase fluid, in particular when it is characterized by a high gas / liquid volume ratio (GLR under real temperature and pressure) high.

• un ensemble de machines monophasiques (composé au minimum d'une pompe et d'un compresseur) précédées d'un système de séparation. Ce mode de production conduit à des installations de compression encombrantes et coûteuses,
• l'utilisation d'impulseurs radiaux pour comprimer directement un mélange gaz-liquide. Ces impulseurs sont limités à des taux de gaz généralement inférieurs à 20%. Cette limite peut être repoussée à environ 30 % en utilisant des impulseurs radio-axiaux et au-delà avec des impulseurs axiaux,
• les machines volumétriques (alternatives, à vis, à membranes) qui permettent d'obtenir un bon rendement de compression pour un mélange diphasique. En revanche, elles sont très mal adaptées aux grands débits volumiques qui caractérisent les applications à fort taux de gaz,
• les dispositifs rotodynamiques avec impulseurs hélico-axiaux, tels que ceux décrits dans le brevet du demandeur FR 2.665.224, ces derniers sont particulièrement bien adaptés à la compression d'un mélange diphasique présentant un grand débit volumique. En revanche, la faible hauteur manométrique produite par chaque impulseur ne permet pas d'obtenir des taux de compression très élevés lorsque le GLR est supérieur à 20. Par ailleurs, le rendement de ces impulseurs est inférieur au rendement des machines monophasiques et tend à décroítre lorsque la pression d'entrée diminue,
• des dispositifs qui utilisent des séparateurs dynamiques en amont d'un compresseur de gaz sec, tels que le compresseur de fluide gazeux associé à un séparateur gaz-liquide qui est décrit dans la demande de brevet WO 87/03 051.

Various devices, some examples of which are given below, make it possible to compress a two-phase fluid composed of a gas and a liquid, and possibly of solid particles:

• a set of single-phase machines (composed at least of a pump and a compressor) preceded by a separation system. This production method leads to bulky and costly compression installations,
• the use of radial impellers to directly compress a gas-liquid mixture. These impellers are limited to gas rates generally less than 20%. This limit can be increased to around 30% by using radio-axial impellers and beyond with axial impellers,
• volumetric machines (alternative, screw, membrane) which allow to obtain a good compression efficiency for a two-phase mixture. On the other hand, they are very ill-suited to the high volume flow rates which characterize applications with a high rate of gas,
• rotodynamic devices with helical-axial impellers, such as those described in the applicant's patent FR 2,665,224, the latter are particularly well suited to the compression of a two-phase mixture having a high volume flow rate. On the other hand, the low headroom produced by each impeller does not allow very high compression ratios to be obtained when the GLR is greater than 20. Furthermore, the efficiency of these impellers is lower than the efficiency of single-phase machines and tends to decrease when the inlet pressure decreases,
• devices which use dynamic separators upstream of a dry gas compressor, such as the gaseous fluid compressor associated with a gas-liquid separator which is described in patent application WO 87/03 051.

The present invention relates to a compression system which comprises at least a compression section, capable of accepting gas or liquid, and communicating a energy value to each of these fluids.

The compression system includes means for performing the switching of this compression section from gas mode to liquid mode and Conversely.

The present invention relates to an alternating compression-pumping system, making it possible to communicate energy to a multiphase fluid having a composition variable over time, for example a variation in the amount of gas phase and the amount of liquid phase.

• au moins une section de compression-pompage à fonctionnement alterné, adaptée à communiquer une valeur de pression à un fluide essentiellement liquide ou à un fluide essentiellement gazeux, la section de compression-pompage comportant au moins un conduit d'introduction d'une phase essentiellement liquide, au moins un conduit d'introduction d'une phase essentiellement gazeuse, au moins un conduit d'évacuation d'un gaz ayant acquis une certaine énergie après passage dans le système, et au moins un conduit d'évacuation de liquide ayant acquis une certaine énergie par passage dans la section de compression-pompage,
• au moins une section de pompage choisie pour communiquer de l'énergie à un fluide essentiellement liquide, la section de pompage comportant au moins un conduit d'introduction d'une phase essentiellement liquide et au moins un conduit d'évacuation de la phase liquide pompée,
• au moins un dispositif de séparation des différentes phases constituant le fluide polyphasique, le dispositif de séparation étant relié à un conduit d'introduction du fluide polyphasique, et au conduit d'évacuation de liquide provenant de la section de compression-pompage alternée, le dispositif comportant au moins un conduit d'évacuation de la phase gazeuse et au moins un conduit d'évacuation de la phase liquide,
• le dispositif de séparation est pourvu de moyens (C_L) permettant de détecter le niveau de l'interface gaz-liquide, du fluide introduit dans le dispositif de séparation,
• des moyens (Vgi, Vli) permettant de contrôler le débit des phases liquides ou gaz au niveau des différents conduits,
• des moyens de contrôle-commande permettant de faire varier l'état des moyens de contrôle de débit de manière à faire passer la section de compression d'un mode de fonctionnement adapté au gaz à un mode de fonctionnement pour le liquide et réciproquement.

It is characterized in that it comprises in combination at least the following elements:

• at least one alternating-operation compression-pumping section, adapted to communicate a pressure value to an essentially liquid fluid or to an essentially gaseous fluid, the compression-pumping section comprising at least one conduit for introducing an essentially phase liquid, at least one conduit for introducing an essentially gaseous phase, at least one conduit for discharging a gas having acquired a certain energy after passing through the system, and at least one conduit for discharging liquid having acquired a certain energy per passage in the compression-pumping section,
• at least one pumping section chosen to communicate energy to an essentially liquid fluid, the pumping section comprising at least one conduit for introducing an essentially liquid phase and at least one conduit for discharging the pumped liquid phase ,
• at least one device for separating the different phases constituting the multiphase fluid, the separation device being connected to a pipe for introducing the multiphase fluid, and to the pipe for discharging liquid from the alternating compression-pumping section, the device comprising at least one pipe for discharging the gaseous phase and at least one pipe for discharging the liquid phase,
• the separation device is provided with means (C _L ) for detecting the level of the gas-liquid interface, of the fluid introduced into the separation device,
• means (Vgi, Vli) for controlling the flow rate of the liquid or gas phases in the various conduits,
• control-command means making it possible to vary the state of the flow-control means so as to switch the compression section from an operating mode suitable for gas to an operating mode for liquid and vice versa.

The compression system can include at least one recycling conduit for a at least fraction of essentially gaseous fluid from the compression-pumping section to the separation device.

The system includes, for example, a recycling conduit of at least a fraction of the essentially liquid fluid from the pumping section to the separation device.

• un conduit hélicoïdal destiné à effectuer la séparation des gouttelettes de liquide de la phase gazeuse,
• une série de disques montés sur l'arbre de rotation, l'arbre de rotation se prolongeant dans le séparateur.

The separation device can be associated with at least one of the following elements:

• a helical duct intended to separate the liquid droplets from the gas phase,
• a series of discs mounted on the rotation shaft, the rotation shaft extending into the separator.

According to one embodiment, the compression section comprises for example at minus one stage allowing separation of the gas phase and the liquid phase in the form of droplets.

The present invention also relates to a method for communicating the energy at each of the phases of a multiphase fluid, the fluid comprising at least one liquid phase and at least one gaseous phase, the amount of the essentially liquid phase and the quantity of the essentially gaseous phase can vary over time, the phase gas being sent to a compression-pumping section and the liquid phase being sent to a pumping section or to a compression-pumping section in alternating operation, the sections being part of a compression-pumping system.

a) on sépare le fluide polyphasique en une phase essentiellement gazeuse et une phase essentiellement liquide,

b) on détermine le niveau L de liquide ou de l'interface liquide-gaz dans le dispositif de séparation,

c) on compare le niveau L à une valeur seuil L₀,
   si L est supérieure à L₀, on agit sur un ensemble de moyens de contrôle de débit des phases liquide et gaz de manière à faire passer la section de compression-pompage à fonctionnement alterné du système de compression-pompage alterné d'un mode de fonctionnement P₁ pour un fluide essentiellement gazeux à un mode de fonctionnement P₂ pour un fluide essentiellement liquide,
   en fermant pratiquement entièrement le moyen de contrôle Vg3, ouvrant pratiquement entièrement le moyen de contrôle Vl3 de façon à diriger le liquide vers la section de compression et en ouvrant le moyen de contrôle Vl4,

d) on contrôle le niveau de L en permanence,
   dès que le niveau de L devient inférieur à un niveau de seuil L₂, on agit sur les moyens de contrôle de débit pour faire passer la section de compression du mode P₂ au mode P₁,

en ouvrant pratiquement entièrement le moyen de contrôle Vg3, en fermant pratiquement entièrement le moyen de contrôle Vl3 de façon à diriger le gaz vers la section de compression et en fermant le moyen de contrôle Vl4.It is characterized in that it comprises at least the following stages:

a) the multiphase fluid is separated into an essentially gaseous phase and an essentially liquid phase,

b) the level L of liquid or of the liquid-gas interface in the separation device is determined,

c) the level L is compared with a threshold value L ₀ ,
if L is greater than L ₀ , action is taken on a set of means for controlling the flow of the liquid and gas phases so as to switch the alternating compression-pumping section of the alternating compression-pumping system from a mode of operating P ₁ for an essentially gaseous fluid in an operating mode P ₂ for an essentially liquid fluid,
by closing the control means Vg3 almost entirely, opening the control means Vl3 almost entirely so as to direct the liquid towards the compression section and by opening the control means Vl4,

d) the level of L is constantly monitored,
as soon as the level of L becomes lower than a threshold level L ₂ , action is taken on the flow control means to switch the compression section from mode P ₂ to mode P ₁ ,

by opening the control means Vg3 almost entirely, by closing the control means Vl3 almost entirely so as to direct the gas towards the compression section and by closing the control means Vl4.

When switching from mode P ₁ to mode P ₂ , the initial speed of rotation N _P1 can be varied towards a speed of rotation N _P2 , the speed of rotation N _P2 being chosen such that the value of the discharge pressure of the compression section obtained during the passage of a gaseous fluid is substantially identical to the discharge pressure value when the section is traversed by a liquid fluid and conversely vary the speed of rotation when changing from the mode P ₂ to the mode P ₁ .

The step of separating the droplets of liquid from the gaseous phase is continued. the interior of a compression stage arranged at the level of the compression-pumping section alternated.

According to an embodiment of the method, when the value of L is less than L ₁ , for example a majority of the liquid fraction from the pumping section is recycled to the separation step a).

According to another embodiment, at least a fraction of the gas phase from the compression section to the separation device so as to maintain a minimum flow of fluid in the compression section. The stage of separation is for example carried out in a separation device.

The system and the method according to the invention are used for example to transfer a certain energy in the liquid phase and in the gas phase of a petroleum effluent. They can also be used to transfer some energy to the liquid phase and to the gas phase of a wet gas, such as a condensate gas or an associated gas.

The invention relates more generally to a compression-pumping system alternating to communicate energy to one or more fluids, said fluids can be liquid or gaseous.

• au moins une section de compression à fonctionnement alterné, adaptée à communiquer une valeur de pression à un fluide essentiellement liquide ou à un fluide essentiellement gazeux, la section de compression comportant au moins un conduit d'introduction d'un fluide essentiellement liquide, au moins un conduit d'introduction d'un fluide essentiellement gazeux, au moins un conduit d'évacuation d'un fluide ayant acquis une certaine valeur d'énergie par passage dans la section de compression et au moins un conduit d'évacuation d'un fluide essentiellement liquide,
• des moyens permettant de déterminer la nature du fluide arrivant dans le système, les moyens étant disposés en amont du système,
• des moyens permettant de contrôler le débit du liquide ou du gaz,
• des moyens de contrôle-commande permettant de faire varier l'état des moyens de contrôle de débit de manière à faire passer la section de compression d'un mode de fonctionnement adapté au gaz à un mode de fonctionnement pour le liquide et réciproquement.

It is characterized in that it comprises in combination at least the following elements:

• at least one alternating operation compression section, adapted to communicate a pressure value to an essentially liquid fluid or to an essentially gaseous fluid, the compression section comprising at least one conduit for introducing an essentially liquid fluid, at least a conduit for introducing a substantially gaseous fluid, at least one conduit for discharging a fluid having acquired a certain energy value by passing through the compression section and at least one conduit for discharging a fluid essentially liquid,
• means making it possible to determine the nature of the fluid arriving in the system, the means being arranged upstream of the system,
• means making it possible to control the flow of liquid or gas,
• control-command means making it possible to vary the state of the flow-control means so as to switch the compression section from an operating mode suitable for gas to an operating mode for liquid and vice versa.

The invention also relates to an associated method for communicating energy to a fluid which can be either essentially liquid or essentially gaseous.

a) on détermine la nature du fluide auquel on doit communiquer de l'énergie,

b) on envoie le fluide quelque soit sa nature à une section de compression-pompage alternée,

c) on adapte lors de l'étape b) la section de compression-pompage alternée à la compression du fluide lorsque ce dernier est essentiellement gazeux ou au pompage du fluide lorsque ce dernier est essentiellement liquide.

It is characterized in that it comprises at least the following stages:

a) the nature of the fluid to which energy must be communicated is determined,

b) the fluid is sent, whatever its nature, to an alternating compression-pumping section,

c) adapting during step b) the alternating compression-pumping section to the compression of the fluid when the latter is essentially gaseous or to the pumping of the fluid when the latter is essentially liquid.

During the process, the speed of rotation of the cross section is adjusted, for example compression-pumping with alternating operation.

• réduire le nombre de machines, comparé à des machines monophasiques et polyphasiques rotodynamiques, et de réduire l'encombrement et le poids comparé à des machines volumétriques,
• diminuer la consommation de puissance comparativement à des machines polyphasiques rotodynamiques.

The use of the system according to the invention has the following advantages in particular:

• reduce the number of machines, compared to single-phase and multi-phase rotodynamic machines, and reduce the size and weight compared to volumetric machines,
• reduce power consumption compared to multi-phase rotodynamic machines.

• la figure 1 schématise un exemple de système de compression diphasique selon l'invention ainsi que son mode de fonctionnement,
• la figure 2 schématise un exemple de séquence d'ouverture et de fermeture de vannes en fonction de l'évolution du niveau de liquide dans le séparateur,
• la figure 3 représente les performances hydrauliques d'une série d'impulseurs adaptée à la compression d'un gaz et un moyen permettant de limiter leur désadaptation à une phase incompressible,
• les figures 4A et 4B représentent une variante du système de compression décrit à la figure 1,
• la figure 5 schématise un mode de réalisation plus général pour le système de compression-pompage.

Other advantages and characteristics of the device according to the invention will be better understood on reading the description below of a nonlimiting example with reference to the appended figures:

• FIG. 1 shows schematically an example of a two-phase compression system according to the invention as well as its operating mode,
• FIG. 2 shows schematically an example of the sequence of opening and closing of valves as a function of the evolution of the level of liquid in the separator,
• FIG. 3 represents the hydraulic performance of a series of impellers adapted to the compression of a gas and a means making it possible to limit their mismatch to an incompressible phase,
• FIGS. 4A and 4B represent a variant of the compression system described in FIG. 1,
• Figure 5 shows schematically a more general embodiment for the compression-pumping system.

FIG. 1 represents an exemplary embodiment for the compression-pumping system comprising the features of the invention, given by way of illustration and in no way limiting, to better understand the operating principle.

This system makes it possible to raise the pressure of a multiphase fluid and in particular the pressure for each of the constituent phases.

The expression "gas phase" is used to designate a fluid essentially gaseous or a gas resulting from the separation of the multiphase fluid, and the expression “liquid phase” an essentially liquid fluid or a liquid.

The alternating compression-pumping system is for example integrated in the same enclosure or casing 1. It comprises at least one pumping section 2 adapted to a fluid essentially liquid and at least one compression section 3 whose characteristics techniques are adapted to an essentially gaseous fluid but which can also function for an essentially liquid fluid. The compression section is designated under the expression "alternating pumping section" for reasons of simplification.

Each of the compression 3 or pumping 2 sections comprises several stages composed of impellers followed by rectifiers. These impellers and rectifiers are chosen among those usually used in the fields of pumping and compression of fluids comprising several phases or of monophasic fluids.

The compression section 3 may include one or more inlet stages which will be adapted to finalize the separation of the multiphase fluid according to methods classics used by the skilled person. This embodiment is advantageous when the gas has liquid droplets even if they are weak quantities.

The impellers of the compression section 3 and the pumping section 2 are by example attached to the same rotation shaft 4. These two sections 2, 3 are separated by sealing means 19 (FIG. 4A) making it possible to avoid the migration of the phases between the sections.

Without departing from the scope of the invention, these sections can also be presented by example in the form of separate and distinct sections integral with the same tree of rotation.

It further comprises a separation device 5 integrated for example in the casing 1. According to other alternative embodiments, the separator can be integral with or separate from the casing.

• au moins un conduit 6 d'arrivée du fluide polyphasique à comprimer (auquel on va communiquer une certaine valeur d'énergie),
• au moins un conduit 7 de transfert de la phase essentiellement liquide, reliant le séparateur 5 et la section 2 de pompage (la liaison étant effectuée par exemple au niveau du premier étage d'entrée de la section de pompage),
• au moins un conduit 8 d'extraction de la phase essentiellement gazeuse, disposé de préférence dans la partie supérieure du séparateur 5, et qui est relié par exemple à l'entrée de la section 3 de compression. Le conduit 8 est équipé par exemple d'une vanne Vg3 fonctionnant en tout ou rien, qui est située le plus proche possible de l'entrée de l'étage d'entrée de la section de compression,
• au moins un conduit 9 d'extraction de la phase essentiellement liquide, disposé au niveau du séparateur 5 de préférence dans sa partie inférieure, et qui est relié à l'entrée de la section 3 de compression. Ce conduit 9 est équipé d'une vanne Vl3 fonctionnant en tout ou rien, située le plus proche possible de l'entrée de la section de compression,
• les conduits 8 et 9 peuvent déboucher au niveau d'un même étage d'entrée de la section de compression, par exemple dans une même volute (non représentée sur la figure pour des raisons de simplification mais connue de l'Homme du métier),
• au moins un conduit 10 d'extraction de la phase essentiellement liquide qui a acquis une certaine énergie en passant à travers la section de compression-pompage à fonctionnement alternée, le conduit 10 peut être équipé d'une vanne Vl4,
• un conduit 11 d'évacuation de la phase essentiellement liquide ayant acquis de l'énergie à travers la section de pompage 2, disposé en sortie de la section de pompage 2 ;

The casing 1 and the separator 5 are provided with several conduits for the introduction, extraction or transfer of the essentially two-phase (gas-liquid) or essentially single-phase (gas or liquid) phases, for example:

• at least one inlet pipe 6 for the multiphase fluid to be compressed (to which a certain energy value will be communicated),
• at least one duct 7 for transferring the essentially liquid phase, connecting the separator 5 and the pumping section 2 (the connection being made for example at the level of the first inlet stage of the pumping section),
• at least one conduit 8 for extracting the essentially gaseous phase, preferably arranged in the upper part of the separator 5, and which is connected for example to the inlet of the compression section 3. The duct 8 is equipped for example with a Vg3 valve operating in all or nothing mode, which is located as close as possible to the inlet of the inlet stage of the compression section,
• at least one conduit 9 for extracting the essentially liquid phase, disposed at the level of the separator 5 preferably in its lower part, and which is connected to the inlet of the compression section 3. This conduit 9 is equipped with a Vl3 valve operating in all or nothing, located as close as possible to the inlet of the compression section,
• the conduits 8 and 9 can open out at the same inlet stage of the compression section, for example in the same volute (not shown in the figure for reasons of simplification but known to those skilled in the art),
• at least one conduit 10 for extracting the essentially liquid phase which has acquired a certain energy by passing through the compression-pumping section with alternating operation, the conduit 10 can be equipped with a valve Vl4,
• a conduit 11 for discharging the essentially liquid phase having acquired energy through the pumping section 2, disposed at the outlet of the pumping section 2;

The conduit 11 can be divided into two conduits 11a, 11b.

The duct 11a is equipped with a control valve Vl1 and makes it possible to recycle a at least fraction of the essentially liquid phase to the separator 5. This fraction of liquid may, without departing from the scope of the invention, come from an external source of liquid connected to conduit 11a.

• un conduit 12 d'évacuation de la phase essentiellement gazeuse disposé à la sortie de la section de compression 3.

The conduit 11b is provided for example with a regulating valve Vl2 making it possible to transfer a quantity of liquid to another place. A device 14 for measuring the flow rate can optionally be fitted to the duct 11:

• a duct 12 for discharging the essentially gaseous phase disposed at the outlet of the compression section 3.

The duct 12 is provided for example with a flow measurement device 13.

This duct is divided for example into two ducts 12a, 12b.

The conduit 12a is provided with a control valve Vg1 which allows the recycling of a fraction of the compressed gas to the supply line so as to reintroduce it into the separator. This recycling circuit acts as a protection circuit for the section of compression.

The conduit 12b comprises for example a valve Vg2 which allows the gas to be evacuated.

The protection circuit (12a, Vg1) makes it possible to maintain a minimum flow so as to protect the system against highly destructive flow fluctuations at reduced flow. One of the ways of implementing it is given in the following description.

The recycling system (11a, Vl1) allows to maintain a minimum flow of liquid so as to protect the alternating compression-pumping system against vibrations generated at reduced flow.

The conduits 11b and 12b can be combined into a single conduit 16 to evacuate the fluid to a place of destination or a place of treatment.

The separator 5 and the various aforementioned conduits are optionally equipped with means making it possible to determine the pressure and the temperature, such as sensors C _P , C _T , not shown for reasons of simplification of the figure.

The alternating compression-pumping system also includes means for determine the speed N of rotation of the shaft 4 supporting the impellers of the sections of compression and pumping.

The separator 5 is equipped with means for example one or more sensors C _L to determine the level of the liquid-gas interface. Advantageously, this or these sensors are capable of monitoring the evolution of the level of liquid inside the separator.

All the measuring devices are connected to a control-command system 15 who is able to memorize the different information, process it and send signals allowing to act on the different valves equipping the system according to a method an example of which is given below.

The control-command system 15 is thus capable of controlling the various operations given as a nonlimiting and illustrative example below.

• une valeur moyenne de GLR, désignée GLRmo, qui se réfère à une très longue durée de production, par exemple de l'ordre du mois. Cette valeur, ainsi que la valeur du débit volumique total sont utilisées pour dimensionner les vannes et les impulseurs associés aux sections de compression et de pompage,
• selon un mode de mise en oeuvre de l'invention, deux valeurs pour la vitesse de rotation N_P1 et N_P2. Ces deux valeurs correspondent respectivement aux vitesses de fonctionnement « normales ou adaptées ou optimisées » lorsque la section de compression est traversée par un fluide essentiellement gazeux et lorsque la section de compression est traversée par un fluide essentiellement liquide,
• par exemple cinq valeurs de niveaux seuils dans le séparateur références L₀, L₁, L₂, L₃ et L₄. L'évolution du niveau de liquide dans le séparateur est « surveillé » par le capteur de niveau C_L précité,
• le niveau seuil L₃ qui est un niveau de régulation autour duquel on cherchera de préférence à rester, pour éviter des basculements trop fréquents pour les sections de compression et de pompage,
• des modes de fonctionnement :

Le mode P₁ : la section dite de compression est traversée ou sur le point d'être traversée par un gaz,
Le mode P₂ : la section dite de compression est traversée ou sur le point d'être traversée par un liquide.
Le basculement du mode P₁ vers le mode P₂ s'effectue lorsque le niveau de liquide dans le séparateur devient supérieur à L₀. Le basculement du mode P₂ vers le mode P₁ s'effectue lorsque le niveau de liquide dans le séparateur devient inférieur à L₂ Le basculement entre les modes de fonctionnement entraíne un changement des états dans lesquels se trouvent les vannes.
Le changement d'état pour les différentes vannes peut être le suivant, le niveau L est le niveau de l'interface variable et surveillé par le capteur C_L de niveau à l'intérieur du séparateur:To describe the steps of the method implemented using this system, the following parameters are defined:

• an average value of GLR, designated GLRmo, which refers to a very long production time, for example of the order of a month. This value, as well as the value of the total volume flow is used to size the valves and impellers associated with the compression and pumping sections,
• according to an embodiment of the invention, two values for the speed of rotation N _P1 and N _P2 . These two values correspond respectively to the "normal or adapted or optimized" operating speeds when the compression section is crossed by an essentially gaseous fluid and when the compression section is crossed by an essentially liquid fluid,
• for example five threshold level values in the separator references L ₀ , L ₁ , L ₂ , L ₃ and L ₄ . The evolution of the liquid level in the separator is "monitored" by the aforementioned level sensor C _L ,
• the threshold level L ₃ which is a regulation level around which it will preferably be sought to remain, to avoid too frequent tilting for the compression and pumping sections,
• operating modes:

Mode P ₁ : the so-called compression section is crossed or about to be crossed by a gas,
P ₂ mode : the so-called compression section is crossed or about to be crossed by a liquid.
The changeover from mode P ₁ to mode P ₂ takes place when the liquid level in the separator becomes greater than L ₀ . The switch from P ₂ mode to P ₁ mode takes place when the liquid level in the separator becomes lower than L ₂ The switch between the operating modes causes a change in the states in which the valves are located.
The change of state for the different valves can be as follows, the level L is the level of the variable interface and monitored by the level C sensor _L inside the separator:

In order to make the various stages understood, we initially position ourselves at a time when the liquid-gas interface of the fluid introduced by the conduit 6 is located around the level L ₃ .

Operation in P ₁ mode and switch to P ₂ mode

• la vanne Vg2 de sortie de gaz est entièrement ouverte et la vanne Vg1 de recyclage de gaz est entièrement fermée,
• la vanne Vl1 de recyclage de liquide est partiellement ouverte. La vanne Vl2 de sortie de liquide est partiellement fermée, le degré de fermeture augmentant avec la valeur de GLRmo de façon à se prémunir contre une arrivée soudaine et relativement importante de liquide (par rapport au cas de fonctionnement normal). Ainsi pour une valeur de GLRmo, par exemple de l'ordre de 10, il ne sera pas nécessaire de sur - dimensionner la vanne Vl2 alors que pour une valeur supérieure (respectivement très supérieure), il conviendra de légèrement (respectivement largement) sur - dimensionner l'ouverture maximale de cette vanne par rapport à la production normale de liquide,
• les vannes Vg3 et Vl3 de sortie de gaz et de liquide sont respectivement entièrement ouverte et fermée,
• la vanne Vl4 d'extraction de liquide est entièrement fermée.

For the reference level L ₃ taken as the starting point, the positions or states of opening and closing of the various valves are as follows:

• the gas outlet valve Vg2 is fully open and the gas recycling valve Vg1 is fully closed,
• the Vl1 liquid recycling valve is partially open. The liquid outlet valve Vl2 is partially closed, the degree of closing increasing with the value of GLRmo so as to protect against a sudden and relatively large arrival of liquid (compared to the case of normal operation). Thus for a value of GLRmo, for example of the order of 10, it will not be necessary to over-size the valve Vl2 whereas for a higher value (respectively very higher), it will be necessary to slightly (respectively largely) on - dimension the maximum opening of this valve in relation to normal liquid production,
• the valves Vg3 and Vl3 for the gas and liquid outlet are respectively fully open and closed,
• the liquid extraction valve Vl4 is fully closed.

The system remains in this state as long as the liquid-gas interface does not move away from the threshold value L ₃ , this is controlled for example using the level sensor C _L. The fluid sent to the compression section is an essentially gaseous fluid.

In the case where the composition of the fluid coming from the conduit 6 varies in such a way that the quantity of liquid will cause a clogging of the separator, the control-command system 15 will act on the different valves to tilt the compression-pumping section from an operating mode for the gas to an operating mode for the liquid, and therefore passing an essentially liquid fluid through the compression section. This corresponds to the transition from operating mode P ₁ to operating mode P ₂ which can be carried out taking account of one or more intermediate reference levels, for example in the example given below by way of illustration and in no way limitative two intermediate levels L ₂ L ₁ , and therefore intermediate changes in the state of the valves.

When the level L becomes higher than L ₃ , the control-command system 15 acts so that the valve Vl1 gradually closes and the valve Vl2 gradually opens. Their openings are subjected to a PID or other type of regulation mode, known to those skilled in the art. When the level L becomes lower than L ₃ , the reverse logic applies.

The evolution of the state of the valves can be followed on diagrams 2A and 2B of the figure 2.

en abscisse on a représenté l'évolution du niveau de l'interface dans le séparateur et

en ordonnée on a représenté :

courbe I : la vitesse de rotation, sur l'échelle des ordonnées l'indice 0 correspond à une vitesse de rotation nulle, et l'indice 100 à une vitesse de rotation nominale,

courbe II, le niveau de liquide dans le séparateur (0 :niveau L4; 100 : niveau L0), et

courbes (III)gi et (III)li le degré d'ouverture des vannes pour le gaz (indice gi) et pour le liquide (indice li) sur l'échelle, 0 correspond à la fermeture des vannes, et 100 à l'ouverture des vannes.

Figure 2 shows schematically an example of opening and closing sequence of valves Vl1, Vl2, Vg1, Vg2, Vg3, Vl3 and Vl4 according to the evolution of the liquid level in the separator, for a tilting sequence comprising the change from operating mode P ₁ to mode P ₂ and vice versa from mode P ₂ to mode P ₁ . The diagrams are given in two diagrams 2A, and 2B representing the state of the valves Vl1, Vl2, Vg1, Vg2 and Vg3, Vl3 and Vl4,; whose evolution is represented by the curves (III) gi and (III) li, the indices i corresponding to the number of the valves, and the letters g and I to the gas and liquid phases.

on the abscissa we have represented the evolution of the level of the interface in the separator and

on the ordinate we have represented:

curve I: the speed of rotation, on the ordinate scale the index 0 corresponds to a zero speed of rotation, and the index 100 to a nominal speed of rotation,

curve II, the liquid level in the separator (0: level L4; 100: level L0), and

curves (III) gi and (III) li the degree of opening of the valves for the gas (index gi) and for the liquid (index li) on the scale, 0 corresponds to the closing of the valves, and 100 to the opening of the valves.

The references MP1, MP2 and PS correspond to operation in mode P ₁ , P ₂ or in mode P ₁ stabilized around the level L ₃ .

Lorsque le niveau L devient supérieur à L₂, le système de contrôle - commande agit pour fermer au moins partiellement la vanne Vg2, ouvrir partiellement la vanne Vg1, fermer entièrement la vanne Vl1 et ouvrir entièrement la vanne Vl2 ( cf. diagramme 2A figure 2). La fermeture de la vanne peut être réalisée en suivant une loi sensiblement linéaire.

Le niveau L de l'interface liquide-gaz continuant à monter à l'intérieur du séparateur, dès qu'il devient supérieur à L₁, le système 15 de contrôle - commande agit pour fermer entièrement la vanne Vg2 de façon à se prémunir d'une entrée de la phase liquide dans la section de compression, et pour ouvrir la vanne Vg1 afin de maintenir un débit de gaz supérieur au débit minimum dans la section de compression permettant d'assurer un bon fonctionnement de la section de compression.

The evolution of the state of the valves for implementing the process can be as follows:

When the level L becomes higher than L ₂ , the control-command system acts to at least partially close the valve Vg2, partially open the valve Vg1, completely close the valve Vl1 and fully open the valve Vl2 (see diagram 2A in figure 2 ). The valve can be closed by following a substantially linear law.

As the level L of the liquid-gas interface continues to rise inside the separator, as soon as it becomes greater than L ₁ , the control-command system acts to completely close the valve Vg2 so as to protect against an entry of the liquid phase into the compression section, and to open the valve Vg1 in order to maintain a gas flow rate greater than the minimum flow rate in the compression section making it possible to ensure correct operation of the compression section.

In addition, the rotation speed can be reduced according to a substantially linear law.

During the two stages which have just been described, the control-command system, acting on the valves, has positioned the latter in intermediate states (or preliminary states) in the state in which they will have to be put for the passage from the operating mode of P ₁ to the operating mode P ₂ .

This last passage is triggered when the level L becomes greater than L ₀ . The control-command system 15 acts to decrease the speed of rotation to the speed of rotation N _P2 and completely close the valve Vg3, fully open the valve Vl3 so as to direct the liquid towards the compression section and open the valve Vl4 (reference> L0 (t1) in diagram 2B in Figure 2). The switching of the operating mode being completed, the compression-pumping system 15 will open the valve Vg2 so as to evacuate the liquid through the compression section, and close the valve Vg1 entirely. (reference> L0 (t2) on diagram 2B in figure 2)

The opening of the valve Vl4 makes it possible to limit the mismatching of the stages of compression during an operation with a very little compressible phase (phase essentially liquid) as shown in Figure 3.

In P ₁ mode, the inlet liquid flow rate may be insufficient to maintain the liquid level at L ₃ . When the level L becomes lower than L ₄ , the control-command system 15 acts so that the valve Vl2 closes completely, so as to prevent entry of the gas phase into the liquid section and to increase the opening. of valve Vl1, so as to allow operation at a flow rate greater than the minimum flow rate below which the vibrations appear. This operating mode is maintained while the liquid level is below L ₄ . When the liquid level becomes higher than L ₃ , the valve Vl2 resumes the opening corresponding to a normal operating case and the opening of the valve Vl1 is adjusted so as to regulate the liquid level around L ₃ .

Switching from P ₁ mode to P ₂ mode and operating for a period of time in P2 mode

In operating mode P ₂ , the so-called compression section is crossed by an essentially liquid phase, therefore having a high density. The compression ratio can then be very high and even too high compared to the mechanical strength of the impellers, the casing and the installations usually used and located downstream of the casing. Advantageously, the speed of rotation Np ₂ is chosen so that the discharge pressure is approximately equal to that obtained in mode P ₁ , taking into account the densities of each phase, and so that N _P2 <N _P1 .

The valve positions and the speed of rotation are maintained in the state which followed the changeover as long as the level remains higher than L ₂ so as to avoid too frequent mode changes, in the case for example of changes from P ₁ to P ₂ and from P ₂ to P ₁ triggered by the same level of liquid.

Switching from P ₂ mode to P ₁ mode

When the level L becomes lower than L ₂ , the control-command system gradually switches the operating mode of the compression system from mode P ₂ to mode P ₁ .

The first phase of the changeover (diagram 2B in Figure 2 <L2 (t3)) consists of fully open the valve Vg3, partially open the valve Vg1 and close the valves Vl3 and Vl4 so as to direct the gaseous fluid contained in the separator towards the section of compression.

This operation completed, (diagram 28 of FIG. 2 <L2 (t4)) the control-command system acts to open the valve Vg2 (practically entirely, L3 (t5)) so as to allow the evacuation of the gas when the pressure at the outlet of the compression section reaches a pressure greater than the pressure measured downstream of the junction Js, put the valve Vl2 in an open position substantially identical to the position corresponding to the normal operation previously defined and open the valve Vl1 so as to maintain the liquid level around L ₃ . At L3 (t5) we observe the start of the closing of valve Vg1.

After a time of the order of a few minutes, the control-command system acts to close the valve Vg1 entirely (diagram 2A in FIG. 2 L3 (t6)) and to reset the value of the rotation speed to a corresponding value substantially at the value Np1 (mode P ₁ ). However, the opening of the valve Vg1 is maintained in a state such that the gas flow is greater than the flow corresponding to the minimum authorized flow (anti-pumping protection). This flow rate value is specified in relation to the characteristics of the compression section.

FIG. 3 represents, in a flow coefficient diagram (on the abscissa), pressure coefficient (on the ordinate), the evolution of operating points of the section of compression-pumping with alternating operation, when the compression-pumping system is equipped with means making it possible to adapt at least one series of compression stages to the pumping a liquid, knowing that these compression stages were initially chosen by compared to an essentially gaseous fluid. These means are for example in the example given one or more extraction pipes fitted with valves to control the passage of fluids.

Les points Ai correspondent au point de fonctionnement pour une phase compressible,

les points Ci à l'évolution sur les courbes de fonctionnement du point de fonctionnement pour le pompage d'un liquide avec une étape d'extraction,

les points Bi à l'évolution du point de fonctionnement pour le pompage d'un liquide lorsqu'il n'y a pas d'étape d'extraction.

The curves Ei, represent the operating curves of the compression-pumping system, i being the number of the compression stage

The points Ai correspond to the operating point for a compressible phase,

the points Ci in the evolution on the operating curves of the operating point for pumping a liquid with an extraction step,

the Bi points at the evolution of the operating point for pumping a liquid when there is no extraction step.

The term “adaptation” of a stage means in the context of the present invention, the operation of a stage at a rate corresponding to the point of best efficiency, point which is known to the specialist in compression machines. Flow and pressure coefficients of a stage are dimensionless quantities which are respectively proportional to the flow rate of the stage and at the head, two known parameters of the same specialist.

In the example given with reference to this FIG. 3, the compression section is made up of four stages: references E ₁ to E ₄ .

When the compression section operates with an essentially gaseous fluid, the adaptation of the stages is represented by the points A ₁ to A ₄ , the volume flow rates decreasing from the first to the last stage, taking into account the compressibility of the gas.

When the compression section operates with liquid, without making any technical changes compared to the characteristics chosen for the gas, the operation of the first stage at point B ₁ results in the operation of the following stages respectively at points B ₂ , B ₃ and B ₄ . If a stage is sometimes well suited, stage E ₂ (point B ₂ ), the stages situated upstream and downstream of this stage are generally very ill-adapted. Thus the stages E ₁ and E ₃ will give very poor yields and will generate overheating as well as flow fluctuations. As for stage E ₄ , (represented by point B ₄ ), it will reduce the energy supplied to the fluid (compression ratio less than 1) by stages E ₁ to E ₃ .

It is possible to adapt a series of stages (initially adapted to the compression of a gas) pumping a liquid by extracting part of the liquid downstream from one or more stages, the extracted flow being returned to the separator 5.

For this, the compression system according to the invention comprises at least one conduit extraction 10 disposed between two stages of compression and a valve Vl4. The fraction of fluid extracted from the compression section can be sent to the separator 5 or else towards a point external to the compression-pumping system according to the invention.

Thus in Figure 3 there is shown, the case where an extraction is performed downstream of the second stage E ₂ , in order to obtain an operation according to points C ₁ to C ₄ , neighbors of the optimum operating point. By increasing the number of extractions it is possible to perfect the adaptation of the compression section when it must operate with a liquid fluid.
Thus by carrying out three extractions, downstream of the stages E ₁ to E ₃ , it will be possible to operate, with a liquid, the stages on the points A ₁ to A ₄ .

The flow rate of extracted liquid is determined by appropriate sizing of the duct extraction 10 (length and diameter) or by the introduction of an energy dissipating organ known to those skilled in the art (restriction, orifice, type valve or anything) in this conduit.

FIG. 4A represents an alternative embodiment comprising means allowing optimize the fluid separation step.

This variant comprises a static separator 5 having a reduced volume compared the dimensions of the separators conventionally used upstream of the machines monophasic.

The separator alone performs a rough separation of the phases by simple action of Earth's gravity. An improvement in phase separation can be achieved by putting in rotation the essentially gaseous and liquid phases in the separator 5.

The rotation can for example be obtained by arranging the aspirations of the conduits (7, 8, 9) tangentially to the wall of the separator 5 and substantially perpendicular to the axis of symmetry of the separator (at the center of symmetry of the separator) (not shown in FIG. 4A) as described in the applicant's patent application FR 98/00933. The suction lines 7 and 9 are arranged below level L ₄ while the suction line 8 is disposed above level L ₀ .

A fine separation of the droplets contained in the gas phase can be obtained by performing a dynamic separation or a static separation:

Dynamic separation can be achieved by an arrangement of several elements such as those depicted in Figure 4A

• by having rotating discs Dg in the upper part of the separator tank 5, for example above the level L ₀

In this example, the rotation shaft 4 common to the pumping section 2 and to the compression section 3 enters the static separator 5 of FIG. 4A and serves as support for disc series.

The rotation of the discs causes the gas phase to rotate inside the separator. Under the effect of the centrifugal forces thus generated, the heavier droplets become offset towards the internal wall of the separator.

The diameter of the shaft 4 or of a part of this shaft supporting the Dg disks is dimensioned according to the torque to be transmitted and the required rigidity. The tree could be consisting of several elements, the coupling being done by gear, flexible coupling, magnetic or whatever.

Dg discs are for example arranged so as to avoid the operation of discs at the oil-gas interface and the formation of emulsion.

The diameter of these discs and the distance between the discs in the same series can be determined according to the degree of separation desired upstream of the sections of pumping and compression. For example, we will determine these parameters according to limit diameters for droplets. These parameters can be calculated using a code three-dimensional calculation available to those skilled in the art.

Static separation can be achieved:

• using an ascending helical duct (Figure 4B), having a small radius of curvature of the propeller, upstream of the conduit 8, as detailed in the patent application cited above.

In this figure, a duct 20 of helical shape is arranged around the duct 7 allowing the passage of the liquid phase towards the pumping section and which is arranged substantially at the level of the central axis of the separator. The gas containing the droplets of liquid enters through inlet 21. During its movement in the helical pipe, the droplets are deposited along the wall of the pipe by the action of a centrifugal force. The pipe being ascending in this embodiment which is in no way limiting, the liquid deposited falls back into the separator through the gas inlet 22 while the gas leaves at point 23 (inlet 8). The characteristics of the helical tube (diameter of the tube, radius of the propeller and slope of the propeller) are dimensioned so as to allow the liquid deposited by entrance 22.

The sealing device 19, shown in FIG. 4A, makes it possible to avoid migration phases between the compression and pumping sections. An example of a device is detailed in the aforementioned patent application FR-98 / 00.933, including technical teaching relating to this sealing means is incorporated by reference.

The reliability of the level measurement in the separator being essential for the protection of rotating elements, level measurement can be carried out for example using of three sensors operating according to the principle of majority logic (when a sensor provides information different from the other two, the information from the first is discarded in favor of the other two).

In mode P1, lines 12a and 11a can also be used so as to avoid the operation of the compression section and the pumping section in the reduced flow rate which can lead to rapid damage to the compression section (anti-pumping) and the generation of pressure and vibration fluctuations with regard to the pumping section.

In order to anticipate the arrival of a liquid cap or a large volume of liquid and ensure better protection of multiphase production equipment, a liquid rate and displacement speed measurement system can be installed in upstream of the equipment, so as to anticipate actions on the valves as well as on the speed regulation.

Fuzzy logic regulation taking into account a large number of parameters (for example, the level of liquid in the separator flask, the degree of opening of the assembly valves, the rate of liquid and its speed of movement upstream of the system compression - pumping) can be implemented to allow better optimization of production compared to conventional regulation while ensuring better protection of equipment.

The operating principles of majority logic, fuzzy logic, protection against a minimum flow, of a measurement of rate and speed of liquid in a conduct are known to those skilled in the art.

The two-phase compression device may be preceded by a device 18 (Figure 1) liquid plug retarder in order to limit the risk of liquid engorgement of the separator balloon and therefore limit the number of switches from one mode to one other.

This device is for example arranged upstream of the junction of the conduits 6 and 12a. he works on the principle of an increase in pressure drops for the same speed when the liquid level increases and from an accentuation of this effect to a short distance from the input of the two-phase compression device. The device could be consisting of a diameter restriction, an orifice, a valve or any other member can cause a pressure drop.

In detail, the retarder will react with the two-phase compression system rotodynamics as follows: for a given rotation speed and a pressure of given backflow, to an increase in the rate of liquid at the inlet of the two-phase compression will correspond to an increase in pressure losses, a decrease suction pressure and increased compression ratio. With a machine rotodynamics, at a given speed, an increase in the compression ratio results in a decrease in the volume flow rate at the inlet and consequently a decrease in flow speed in the retarder 18.

Cas 1 - Conditions à l'entrée du dispositif diphasique (pour GLR = 1000) : pression = 2,5 MPa abs, débit volumique total = 12000 m³/hr et diamètre de la conduite = 16 pouces. GLR d'entrée 1000 60 17 8 5 < 5 Perte de charge 0.035 0.06 0.11 0.18 0.26 >0. 26 Débit gaz seul 12000 11400 10800 9400 7000 0 Débit gaz + liquide 12000 11600 11400 10600 8400 0

Cas 2 - Conditions à l'entrée du dispositif diphasique (pour GLR = 1000) : pression = 1 MPa abs, débit volumique total = 12000 m³/hr et diamètre de la conduite = 16 pouces. GLR d'entrée 1000 29 17 11 <11 Perte de charge (1) 0.014 0.059 0.091 0.129 >0. 129 Débit gaz seul (2) 12000 10300 8600 7000 0 (3) Débit gaz + liquide (2) 12000 10600 9100 7600 0 (3)

This effect is illustrated in the tables below in two distinct operating cases and with the following hypotheses: constant rotation speed and delivery pressure.

Case 1 - Conditions at the input of the two-phase device (for GLR = 1000): pressure = 2.5 MPa abs, total volume flow = 12000 m ³ / hr and pipe diameter = 16 inches. Input GLR 1000 60 17 8 5 <5 Pressure loss 0.035 0.06 0.11 0.18 0.26 > 0. 26 Gas flow only 12000 11400 10800 9400 7000 0 Gas + liquid flow 12000 11600 11400 10600 8400 0

Case 2 - Conditions at the input of the two-phase device (for GLR = 1000): pressure = 1 MPa abs, total volume flow = 12000 m ³ / hr and diameter of the pipe = 16 inches. Input GLR 1000 29 17 11 <11 Pressure loss (1) 0.014 0.059 0.091 0.129 > 0. 129 Gas flow only (2) 12000 10300 8600 7000 0 (3) Gas + liquid flow (2) 12000 10600 9100 7600 0 (3)

In actual operation, a decrease in gas production results gradually a decrease in the network pressure in the vicinity of the discharge of the compressor allowing greater absorption of gas flow resulting in less slower production than that indicated by the above tables.

In the case where the speed of rotation is controlled by the discharge pressure, a decrease in this pressure leads to an increase in the speed of rotation and a local acceleration of the flow in the vicinity of the compressor hence a lesser slowdown in production than that indicated by the tables above.
However whatever the network dynamics and the choice of compressor speed regulation mode, the retarder located upstream of the compressor allows in all cases an increase in pressure losses and therefore a decrease in the input volume flow when the GLR decreases.

FIG. 5 schematically represents a compression-pumping system alternating suitable for example for all areas of application where one must communicate energy to several fluids, one of which is essentially liquid and the other essentially gaseous.

In this case, the alternating compression-pumping system includes a section of compression 50 with alternating gas-liquid operation, having one of the characteristics described in the compression-pumping section described in Figure 1.

Two inlet pipes (51, 52) for example a pipe for the introduction of the fluid liquid and a conduit for the introduction of gas.

Means making it possible to determine upstream the nature of the fluid which arrives in the compression system, arranged for example on the inlet conduits.

A fluid outlet conduit 53 having acquired energy.

An evacuation duct 54 for an essentially liquid fluid, the majority of the liquid being evacuated after having acquired energy through conduit 53 and the rest passes through the conduit 54 so as to allow the adaptation of the compression section to the passage of the liquid.

Control means substantially identical to the reference means 15 and described above. These means take into account in particular the result of the determination of the fluid arriving to control the operating tilting of the compression-pumping section in P1 mode or in P2 mode.

Means such as valves 55, 56, 57 and 58 disposed respectively on the conduits 51, 52, 53 and 54. These valves ensure the passage or not of the fluid essentially liquid or essentially gaseous fluid to the operating compression section alternating or from the alternating compression section.

Claims (15)

Alternating compression-pumping system (1) for communicating energy to a multiphase fluid having a composition that varies over time, such as the quantity of gas phase and the quantity of liquid phase, comprising in combination the following elements: at least one alternating operation compression-pumping section (3), adapted to communicate a pressure value to an essentially liquid fluid or to an essentially gaseous fluid, said compression-pumping section (3) comprising at least one conduit (9 ) of introducing an essentially liquid phase, at least one conduit (8) of an essentially gaseous phase, at least one discharge conduit (12) of a gas having acquired a certain energy after passage through the system, and at least one liquid discharge conduit (10) having acquired a certain energy by passing through the compression-pumping section, at least one pumping section (2) chosen to communicate energy to an essentially liquid fluid, said pumping section comprising at least one conduit (7) for introducing an essentially liquid phase and at least one conduit evacuation (11) of the pumped liquid phase, at least one device (5) for separating the different phases constituting the multiphase fluid, said device (5) for separation being connected to an inlet pipe (6) for the multiphase fluid, and to the pipe (10) for discharging liquid coming from the alternating compression-pumping section, said device (5) comprising at least one duct (8) for discharging the gas phase and at least one duct (9) for discharging the liquid phase, said separation device (5) is provided with means (C _L ) making it possible to detect the level of the gas-liquid interface, of the fluid introduced into the separation device (5), means (Vgi, Vli) making it possible to control the flow rate of the liquid or gas phases at the level of the various conduits (9, 10, 11a, 11b, 12a, 12b), control-command means (15) making it possible to vary the state of said flow control means so as to change the compression section from an operating mode adapted to gas to an operating mode for liquid and vice versa . Compression system according to claim 1 characterized in that it comprises at least a pipe (12a) for recycling at least a fraction of the essentially gaseous fluid originating from the compression-pumping section (3) to the separation device (5). Compression system according to claim 1 characterized in that it comprises at least a pipe (11a) for recycling at least a fraction of the essentially liquid fluid originating from the pumping section (2) to the separation device (5). Compression system according to one of Claims 1 to 3, characterized in that the separation device (5) is associated with at least one of the following elements: a helical duct (20) intended to separate the liquid droplets from the gas phase, a series of discs mounted on said rotation shaft (4), said rotation shaft extending into said separator (5). System according to one of Claims 1 to 3, characterized in that the cross-section of compression includes at least one stage enabling phase separation to be obtained gas and liquid phase in the form of droplets. Method for communicating energy to each of the phases of a multiphase fluid comprising at least one liquid phase and at least one gaseous phase, the quantity of the essentially liquid phase and the quantity of the essentially gaseous phase possibly varying over time , said gaseous phase being sent to an alternating pumping compression section and said liquid phase being sent to a pumping section or to said alternating pumping section, the sections being part of a compression system alternating pumping,
characterized in that it comprises at least the following stages: a) separating said multiphase fluid into an essentially gaseous phase and an essentially liquid phase, b) the level L of liquid or of the liquid-gas interface in a separation device (5) is determined, c) the level L is compared with a threshold value L ₀ ,
if L is greater than L ₀ , action is taken on a set of means (Vgi, Vli) for controlling the flow of the liquid and gas phases so as to pass the section (3) of compression-pumping with alternating operation of said compression system alternating pumping from an operating mode P ₁ for an essentially gaseous fluid to an operating mode P ₂ for an essentially liquid fluid,
by closing the control means (Vg3) almost entirely, opening the control means (Vl3) almost entirely so as to direct the liquid towards the compression section and by opening the control means (Vl4) d) the level of L is constantly monitored,
as soon as the level of L becomes lower than a threshold level L ₂ , action is taken on the flow control means to switch the compression section from mode P ₂ to mode P ₁ ,
by opening the control means (Vg3) almost entirely, by closing the control means (Vl3) almost entirely so as to direct the gas towards the compression section and by closing the control means (Vl4). A method according to claim 6 characterized in that one varies during the transition from mode P ₁ to mode P ₂ , the initial speed of rotation N _P1 towards a speed of rotation N _P2 , said speed of rotation N _P2 being chosen from so that the value of the discharge pressure of the compression section obtained during the passage of a gaseous fluid is substantially identical to the value of discharge pressure when the section is traversed by a liquid fluid and vice versa the speed is varied rotation when switching from P ₂ mode to P ₁ mode. Method according to one of claims 6 or 7 characterized in that one continues to separate the liquid droplets of the gas phase inside a compression stage arranged at the alternating compression-pumping section. A method according to claim 6 characterized in that if the value of L is less than L ₄ , a majority of the liquid fraction from the pumping section is recycled to step a) of separation. Method according to claim 6 characterized in that at least a fraction is recycled from the gas phase from the compression section to the separation device so as to maintain a minimum flow rate of fluid in said compression section. Use of the system according to one of claims 1 to 5 and of the method according to one of claims 6 to 10 for transferring certain energy to the liquid phase and to the phase gas from an oil effluent. Use of the system according to one of claims 1 to 5 and of the method according to one of claims 6 to 10 for transferring certain energy to the liquid phase and to the phase gaseous of a wet gas, such as a condensate gas, or an associated gas. Alternating compression-pumping system (1) for communicating energy to a fluid, said fluid possibly being liquid or gaseous, comprising in combination at least the following elements: at least one alternating operation compression-pumping section (50) adapted to communicate a pressure value to an essentially liquid fluid or to an essentially gaseous fluid, said compression-pumping section (50) comprising at least one conduit (51 ) for introducing an essentially liquid fluid at least one conduit (52) for introducing an essentially gaseous fluid, at least one conduit (53) for discharging a fluid having acquired a certain energy value by passage through said compression section and at least one duct (54) for discharging an essentially liquid fluid, means making it possible to determine the nature of said fluid arriving in said system, said means being arranged upstream of said system, means (54, 55, 56, 57) for controlling the flow of liquid or gas, control-command means (15) making it possible to vary the state of said flow control means so as to change the compression section from an operating mode adapted to gas to an operating mode for liquid and vice versa . Method for communicating energy to a fluid which can be either essentially liquid or essentially gaseous, characterized in that it comprises at least the following steps: a) the nature of the fluid to which energy must be communicated is determined, b) said fluid, whatever its nature, is sent to an alternating operation compression-pumping section (50), c) adapting during step b) said compression-pumping section with alternating operation to the compression of the fluid when the latter is essentially gaseous or to the pumping of the fluid when the latter is essentially liquid. Method according to claim 14, characterized in that the speed of rotation is adapted of the alternating compression-pumping section.

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