[0001] The present invention relates to a method and system for boosting the supply of production
fluid from a hydrocarbon wellbore or borehole.
[0002] When a reservoir of production fluid, such as oil, has a low natural pressure and/or
the fluid has a relatively high density, there is a need to boost the pressure of
the fluid at or near the reservoir surface in order to achieve satisfactory production
rates over the life of the reservoir.
[0003] One technique is to install a mechanical pump at a "downhole" location. Such pumps
are typically electrically driven by a supply of high voltage electricity provided
from an associated host facility which may be tens of kilometres away. The provision
of a high voltage power supply for the pump motors is expensive. Furthermore, the
pump is installed in a hostile environment which is hot and corrosive and relatively
inaccessible. Pump maintenance, which is almost inevitably required, necessitates
shutting the well in, thus interrupting production and possibly leading to restarting
problems.
[0004] Another newer but existing technique is to install a hydraulically driven mechanical
pump at a downhole location. Such pumps are typically driven by a supply of pressurised
water, the supply of which is costly. Accessibility and maintenance problems apply
as discussed above.
[0005] A different technique is to use a jet pump which is installed at a downhole location.
Such a pump is supplied with pressurised jetting water from the host facility which
is mixed with the production fluid by the jet pump. The resulting mixture is then
conveyed back to the host facility. Additional costs arise from:
(a) the provision of a relatively large diameter high pressure pipe to supply the
required quantity of pressurised jetting water to the wellbore;
(b) the requirement for a production pipe which is large enough to accommodate the
jetting water in addition to the production fluid; and
(c) separation of the jetting fluid from the production fluid at the host facility.
[0006] US-A-4 718 486 discloses a portable jet pump system mounted on a truck. The truck
is parked next to a well and a jet pump is lowered down the well. Water is pumped
from the system to the jet pump which entrains it with production fluid and the resulting
mixture is conveyed to a separator in the system where gas is separated from the mixture.
The resulting separated liquid is conveyed to a separation tank where oil is separated
from water and the water is recirculated to the jet pump for entraining with the production
fluid.
[0007] US-A-4 790 376 discloses a system having a jet pump installed in a well. Water is
pumped from a storage tank at the surface into the jet pump which entrains it with
production fluid and the resulting mixture is conveyed to a gas-liquid separator at
the surface where gas is separated from the mixture. The resulting separated liquid
is conveyed to an oil-water separator where oil is separated from water and the water
is conveyed to the storage tank. From there the water can be recirculated to the jet
pump.
[0008] US-A-5 570 744 discloses a surface flowline separator system having a baffle-type
separator which receives production fluid from a well. The separator separates the
production fluid into gas and liquid and the separated gas is conveyed to a gas lift
well to entrain with the production fluid in the well to make the production fluid
lighter so that it can reach the surface.
[0009] An object of the invention is to provide a method and system which overcome at least
some of the above-mentioned disadvantages of the prior art.
[0010] Thus, according to the invention there is provided a method of boosting production
from a subsea wellbore having a downhole jet pump and a remote host facility, the
method comprising the steps of:
(a) providing a separation facility located on a seabed and substantially closer to
the wellbore than the host facility;
(b) providing means to deliver jetting fluid under pressure to the jet pump;
(c) entraining wellbore production fluid with the flow of the jetting fluid in the
jet pump and conveying the resulting mixture to the separation facility;
(d) separating a majority of the jetting fluid from the mixture by means of the separation
facility; and
(e) recirculating the separated jetting fluid back to the jet pump and entraining
further production fluid therewith.
[0011] A single separation facility may provide jetting fluid to a plurality of and possibly
all wellbores in a field.
[0012] Such a method may only require a relatively small diameter conduit for supplying
a batch of jetting fluid to the separation facility. Once adequate jetting fluid has
been provided, this conduit will no longer be required for this purpose. The pipe
for conveying production fluid from the separation facility to the host facility need
not be enlarged to cater for conveying the jetting fluid. Separation at the host facility
can be avoided as can the provision, from the host, of a continuous flow of appropriately
treated jetting fluid. The problems associated with a downhole mechanical pump discussed
above are also avoided.
[0013] Preferably at least 90% and more preferably substantially all of the jetting fluid
is separated from the mixture by the separation facility in order to minimise the
volume of fluid for conveyance to the host facility and in order to minimise or preferably
eliminate the requirement for additional jetting fluid from the host facility.
[0014] To maximise the savings resulting from the invention, the separation facility is
preferably situated at or close to the wellbores.
[0015] Preferably the separation facility includes a pump which is used to pressurise the
separated jetting fluid for assisting its recirculation.
[0016] Separation is preferably effected by gravity separation which relies on the jetting
fluid and the production fluid having different specific gravities. Gravity separators
are robust and suitable for use in a hostile location which may be difficult to access.
[0017] According to a second aspect of the invention there is provided a system for boosting
production from a wellbore situated remotely from a host facility and comprising a
downhole jet pump, pressurising means for supplying the jet pump with pressurised
jetting fluid for forming a mixture of jetting fluid and wellbore production fluid,
and a separation facility situated substantially closer to the wellbore than the host
facility including separation means for separating a majority of the jetting fluid
from the mixture and recirculation means for delivering the separated jetting fluid
back to the jet pump for entraining further production further fluid therewith, characterized
in that the wellbore is subsea and that the separation facility is located on a seabed.
[0018] Preferably the separator means includes at least one gravity separation chamber.
[0019] In order to provide system redundancy to minimise the chance of wellbore shut-in
being required, preferably the separator means includes at least two separators for
separating the mixture which are connected in parallel with each other.
[0020] If the separator means includes throttling means arranged to control flows of production
fluid and jetting fluid out of the separation chamber, control of the separation means
can be easily effected, possibly from a control module situated at the separation
means.
[0021] The invention will now be described by way of example only with reference to the
accompanying schematic figures in which:
FIG. 1 shows a system suitable for putting the invention into practice;
FIG. 2 shows the components of the system of Fig. 1 in greater detail; and
FIG. 3 shows a typical jet pump which will be situated at a downhole location in the
systems shown in Figs. 1 and 2.
[0022] In the following description the terms production fluid and jetting fluid will be
employed. These will generally be oil and water (appropriately treated) respectively
but could comprise other fluids or mixtures of fluids.
[0023] A system for putting the invention into practice is shown in Fig. 1. The system includes
at least one wellhead tree 2 which routes fluids from a wellbore or lower production
tubing 4 to a separation facility 6 via a mixture pipe 8. A jetting fluid delivery
pipe 10 extends from the separation facility 6 to the wellhead tree 2 for supplying
jetting fluid to a downhole jetting fluid conduit 12 and hence to a downhole jet pump
14. The separation facility 6 is connected to a host facility 16 by a production pipeline
18 and a jetting fluid supply pipe 20.
[0024] The components of the system will be described in detail with reference to Fig. 2.
[0025] The separation facility 6 includes first and second duplicated separating means 22
and 24 only the first 22 of which will be described in detail. Only one separating
means may be provided.
[0026] The mixture pipe 8 from the wellhead tree is connected to a mixture inlet 26 which
is connected via a failsafe valve 28 to an inlet 30 of a separator chamber 32 containing
a weir 34. A first outlet 36 of the chamber 32 is connected by a jetting fluid conduit
39 containing a recirculation pump 38, a throttle valve 40 and a non-return valve
42 to a jetting fluid outlet 44 of the separation facility 6. A recirculation loop
pipe 46, containing a non-return valve 48 and a pressure restricting device 49, connects
the jetting fluid conduit 39, downstream of the recirculation pump 38, to the inlet
30 of the chamber 32.
[0027] A second outlet 50 of the chamber 32, situated on the opposite side of the weir 34
to the first outlet 36, is connected via a throttle valve 52 to a production fluid
outlet 54 which is connected to the production pipeline 18 leading to processing equipment
on the host facility 16.
[0028] The chamber 32 includes a level sensor 56 for determining the level of the interface
between the production fluid 58 and jetting fluid 60 within the chamber 32.
[0029] The jetting fluid supply pipe 20 from the processing equipment on the host facility
is connected to a jetting fluid inlet 62 of the separation facility which is connected
via a jetting fluid conduit 64, containing a non-return valve 66, to the jetting fluid
outlet 44.
[0030] The host facility 16 includes apparatus (not shown) for processing production fluid
58 received through the production pipeline 18 and a pump 68 for pumping jetting fluid
(water treated as required to inhibit corrosion and hydrate formation problems etc.
upon mixing with the production fluid) to the separation facility 6.
[0031] The jet pump 14 shown in Fig. 3 is a conventional jet pump and will accordingly only
be described in outline. The jet pump includes a nozzle 69 into which jetting fluid
is fed (arrow A) from the jetting fluid conduit 12. Production fluid is routed to
the jet pump via a lower production tubing conduit 70 (arrow B) from the lower production
tubing 4, which opens into a low pressure entrainment region 72 at an outlet end of
the nozzle 68. An intake nozzle 74, also opening into the low pressure entrainment
region 72, is connected to upper production tubing 76 for delivering a mixture of
production and jetting fluid (arrow C) to the wellhead tree 2 via the wellbore riser
76.
[0032] The operation of the system will now be described.
[0033] When production from the lower production tubing 4 needs boosting, for example because
the well pressure is too low, a batch of jetting fluid will be pumped by the host
pump 68 down the jetting fluid supply pipe 20 to the jetting fluid inlet 62 of the
separation facility 6 where it passes through the conduit 64 to the jetting fluid
outlet 44 and on through the jetting fluid delivery pipe 10 to the downhole jetting
fluid conduit 12.
[0034] The jetting fluid then enters the jet pump 14 (arrow A) and is forced through the
nozzle 69 into the entrainment region 72 where a lower pressure zone occurs causing
production fluid to be drawn into the jet pump through the lower production tubing
conduit 70 (arrow B) where it mixes in the entrainment region 72 with the jetting
fluid. The resulting mixture then passes into the intake nozzle 74 and leaves the
jet pump 14 up the upper production tubing 76 (arrow C).
[0035] On emerging from the wellhead tree 2, the mixture passes through the mixture pipe
8 and is conveyed to the inlet 30 of the chamber 32 via the mixture inlet 26 and the
failsafe valve 28. Upon entering the chamber 32, as a consequence of their different
specific gravities, the denser jetting fluid 60 (water) occupies the region to the
left of the weir 34 (as shown in Fig. 2) and the less dense production fluid (oil)
passes over the weir 34 into the region to the right thereof. Once the level sensor
56 detects that the interface between the jetting fluid 60 and the production fluid
58 has reached the level shown in Fig. 2 (i.e. partway up the weir) the supply of
jetting fluid from the host facility will be halted. Thereafter, jetting fluid 60
is drawn from the chamber 32 by the recirculating pump 38 and routed to the jetting
fluid outlet 44 via the jetting fluid conduit 39 from where it travels on to the jet
pump and recombines with further production fluid as described above. Meanwhile, production
fluid leaves the chamber 32 via the second outlet 50 (as a consequence of chamber
pressure) and passes via the throttle valve 52 to the production fluid outlet 54 and
through the production pipeline 18 to the host facility for processing.
[0036] A control system (not shown) receives signals from the level sensor 56 and a pressure
sensor 78 and controls the throttle valves 40 and 52 and the recirculation pump 38
to maintain the interface between the fluids in the chamber 32 at the required level
and the overall pressure in the chamber 32 at an appropriate level. For example, if
the amount of jetting fluid in the chamber 32 needs to be increased, the throttle
valve 40 will be closed slightly in order that jetting fluid will be forced through
the recirculation loop pipe 46 back into the chamber 32.
[0037] Accordingly, the same batch of jetting fluid will be cycled repeatedly between the
jet pump 14 and the separation facility 6. Hence, in the case of local seawater being
deemed unacceptable for the purpose only a relatively small bore pipe 20 will be required
for delivering the initial batch of jetting fluid to the separation facility 6 and
the production pipeline 18 does not need to be unnecessarily enlarged so as to accommodate
a flow of jetting fluid in addition to production fluid. Furthermore, any tariff charged
by the host facility owner will only be in respect of production fluid delivered thereto
and will not be increased as a consequence of delivering jetting fluid thereto.
[0038] The invention has been described in the context of a subsea hydrocarbon field.
1. A method of boosting production from a subsea wellbore (4) having a downhole jet pump
(14) and a remote host facility (16), the method comprising the steps of:
(a) providing a separation facility (6) located on a seabed and substantially closer
to the wellbore (4) than the host facility (16);
(b) providing means (38, 68, ...) to deliver jetting fluid (60) under pressure to
the jet pump (14);
(c) entraining wellbore production fluid with the flow of the jetting fluid in the
jet pump (14) and conveying the resulting mixture to the separation facility (6);
(d) separating a majority of the jetting fluid (60) from the mixture by means of the
separation facility (6); and
(e) recirculating the separated jetting fluid (60) back to the jet pump (14) and entraining
further production fluid therewith.
2. The method according to claim 1 wherein at least 90% of the jetting fluid (60) is
separated from the mixture by the separation facility (6).
3. The method according to claim 2 wherein substantially all of the jetting fluid (60)
is separated from the mixture by the separation facility (6).
4. The method according to any preceding claim wherein the separation facility (6) is
situated at or close to the wellbore (4).
5. The method according to any preceding claim wherein the separation facility (6) includes
a pump (38) which is used to pressurise separated jetting fluid (60) for assisting
its recirculation.
6. The method according to any preceding claim wherein the separation is effected by
gravity separation.
7. A system for boosting production from a wellbore (4) situated remotely from a host
facility (16) and comprising a downhole jet pump (14), pressurising means (38, 68)
for supplying the jet pump (14) with pressurised jetting fluid (60) for forming a
mixture of jetting fluid (60) and wellbore production fluid, and a separation facility
(6) situated substantially closer to the wellbore (4) than the host facility (16)
including separation means (22, 24) for separating a majority of the jetting fluid
(60) from the mixture and recirculation means (10, 12, 38, 39) for delivering the
separated jetting fluid (60) back to the jet pump (14) for entraining further production
fluid therewith, characterized in that the wellbore (4) is subsea and that the separation facility (6) is located on a seabed.
8. The system according to claim 7 wherein the separation means (22, 24) includes at
least one gravity separation chamber (32).
9. The system according to claim 7 or 6 wherein the separation means (22, 24) includes
at least two separators (32) for separating the mixture which are connected in parallel
with each other.
10. The system according to claim 7, 8 or 9 wherein the separation means (22, 24) includes
throttling means (40, 52) arranged to control flows of production fluid and jetting
fluid (60) from the separation means (22, 24).
1. Verfahren zum Fördern eines Produkts aus einem Unterwasser-Bohrloch (4), welches eine
in die Tiefe gerichtete Bohrloch-Strahlförderpumpe (14) und eine entfernte Leiteinrichtung (16)
aufweist, wobei das Verfahren folgende Schritte aufweist:
(a) das Vorsehen einer Abscheideeinrichtung (6), welche auf dem Meeresboden und im
Wesentlichen näher an dem Bohrloch (4) angeordnet ist als die Leiteinrichtung (16);
(b) das Vorsehen von Mitteln (38, 68, ...) zur Förderung einer unter Druck stehenden
strahlgeförderten Flüssigkeit (60) zur Strahlförderpumpe (14);
(c) Mitnahme eines flüssigen Bohrlochproduktes mit dem Strom einer strahlbetriebenen
Flüssigkeit in der Strahlförderpumpe (14) und Förderung des entstehenden Gemisches
zu einer Abscheideeinrichtung (6);
(d) Abscheidung des größten Teils der strahlgeförderten Flüssigkeit (60) aus dem Gemisch
durch die Abscheidungseinrichtung (6); und
(e) Rückführung der abgeschiedenen strahlgeförderten Flüssigkeit (60) zur Strahlförderpumpe
(14) und Mitnahme weiterer Produktflüssigkeit damit.
2. Verfahren nach Anspruch 1, worin mindestens 90 Prozent der strahlgeförderten Flüssigkeit
(60) des Gemischs durch die Abscheideeinrichtung (6) abgeschieden wird.
3. Verfahren nach Anspruch 2, worin im Wesentlichen die gesamte strahlgeförderte Flüssigkeit
(60) des Gemischs durch die Abscheideeinrichtung (6) abgeschieden wird.
4. Verfahren nach einem der vorhergehenden Ansprüche, worin die Abscheideeinrichtung
(6) in der Nähe dem Bohrloch (4) angeordnet ist.
5. Verfahren nach einem der vorhergehenden Ansprüche, worin die Abscheideeinrichtung
(6) eine Pumpe (38) aufweist, welche dazu verwendet wird, die abgeschiedene, strahlgeförderte
Flüssigkeit (60) unter Druck zu stellen, um deren Rückfluss zu unterstützen.
6. Verfahren nach einem der vorhergehenden Ansprüche, worin die Abscheidung durch Schwerkrafttrennung
erfolgt.
7. System zum Fördern eines Produkts aus einem Bohrloch (4), welches sich entfernt von
einer Leiteinrichtung (16) befindet, welches eine in die Tiefe gerichtete Strahlförderpumpe
(14), drucksteigernde Mittel (38, 68) zur Speisung der Strahlförderpumpe (14) mit
unter Druck stehender, strahlgetriebener Flüssigkeit (60) mit einem flüssigen Bohrlochprodukt,
eine Abscheideeinrichtung (6), welche im Wesentlichen näher an dem Bohrloch (4) angeordnet
ist als die Leiteinrichtung (16), welche ihrerseits Abscheidemittel (22, 24) zum Abscheiden
eines Großteils der strahlgetriebenen Flüssigkeit (60) aus dem Gemisch einschließt,
und Rückführungsmittel (10, 12, 38, 39) zur Lieferung der abgeschiedenen, strahlgetriebenen
Flüssigkeit (60) zurück zur Strahlförderpumpe (14), um weitere Produktionsflüssigkeit
mitzufördern, dadurch gekennzeichnet, dass das Bohrloch (4) Unterwasser ist und dass sich die Abscheideeinrichtung (6) auf dem
Meeresgrund angeordnet ist.
8. System nach Anspruch 7, worin die Abscheidungsmittel (22, 24) mindestens eine Schwerkrafttrennkammer
(32) enthalten.
9. System nach Anspruch 7 oder 8, worin die Abscheidungsmittel (22, 24) mindestens zwei
Abscheider (32) zum Abscheiden des Gemisches aufweisen, welche parallel miteinander
verbunden sind.
10. System nach Anspruch 7, 8 oder 9, worin die Abscheidungsmittel (22, 24) Drosselmittel
(40, 52) aufweisen, welche dazu angeordnet sind den Fluss des Produktflusses und der
strahlgetriebenen Flüssigkeit (60) der Abscheidungsmittel (22, 24) steuern.
1. Procédé destiné à augmenter la production d'un forage de puits sous-marin (4) ayant
un éjecteur à orifice orienté vers le bas (14) et une installation hôte distante (16),
le procédé comprenant les étapes de :
(a) fourniture d'une installation de séparation (6) située sur un fond marin et sensiblement
plus proche du forage du puits (4) que de l'installation hôte (16);
(b) fourniture de moyens (38, 68,...) pour délivrer à l'éjecteur (14) un fluide d'éjection
(60) sous pression ;
(c) entraînement du fluide de production du forage du puits avec le flux du fluide
d'éjection dans l'éjecteur (14) et acheminement du mélange résultant vers l'installation
de séparation (6) ;
(d) séparation de la plus grande partie du fluide d'éjection (60) du mélange au moyen
de l'installation de séparation (6) ; et
(e) recyclage du fluide d'éjection (60) par retour vers l'éjecteur (14) et entraînement
ainsi de nouveau du fluide de production.
2. Procédé selon la revendication 1, dans lequel au moins 90% du fluide d'éjection (60)
est séparé du mélange par l'installation de séparation (6).
3. Procédé selon la revendication 2, dans lequel sensiblement la totalité du fluide d'éjection
(60) est séparée du mélange par l'installation de séparation (6).
4. Procédé selon l'une quelconque des revendications précédentes dans lequel l'installation
de séparation (6) est située à l'endroit, ou au voisinage, du forage du puits (4).
5. Procédé selon l'une quelconque des revendications précédentes dans lequel l'installation
de séparation (6) comprend une pompe (38) qui est utilisée pour mettre sous pression
le fluide d'éjection séparé (60) pour faciliter son recyclage.
6. Procédé selon l'une quelconque des revendications précédentes où la séparation est
effectuée par séparation gravimétrique.
7. Système destiné à augmenter la production d'un forage de puits (4) situé à distance
d'une installation hôte (16) et comprenant un éjecteur à orifice dirigé vers le bas
(14), un moyen de mise sous pression (38, 68) pour fournir à l'éjecteur (14) un fluide
d'éjection sous pression (60) pour former un mélange de fluide d'éjection (60) et
de fluide de production du forage du puits, et une installation de séparation (6),
située sensiblement plus près du forage du puits (4) que de l'installation hôte (16)
et comportant un moyen de séparation (22, 24) pour séparer du mélange la plus grande
partie du fluide d'éjection (60) et un moyen de recyclage (10, 12, 38, 39) pour ramener
le fluide d'éjection séparé (60) vers l'éjecteur (14), pour entraîner ainsi de nouveau
le fluide de production, caractérisé en ce que le forage du puits (4) est sous-marin et que l'installation de séparation (6) est
située sur un fond marin.
8. Système selon la revendication 7 dans lequel le moyen de séparation (22, 24) comprend
au moins une chambre de séparation gravimétrique (32).
9. Système selon la revendication 7 ou 8 dans lequel le moyen de séparation (22, 24)
comprend au moins deux séparateurs (32) destinés à séparer le mélange, lesquels sont
connectés en parallèle l'un avec l'autre.
10. Système selon la revendication 7, 8 ou 9 dans lequel le moyen de séparation comprend
un moyen d'étranglement (40, 52) disposé pour contrôler les débits du fluide de production
et du fluide d'éjection (60) en provenance du moyen de séparation (22, 24).