PUMPING SYSTEM
Field of the invention
The present invention relates to a wellbore pumping system submerged into a
wellbore for unloading liquid from a wellbore comprising well fluid, such as gas,
having a wellbore pressure, comprising a pump having an inlet and an outlet, a
tubing fluidly connected with the outlet of the pump, and a driving unit connected
with and powered by a cable, such as a wireline, and having a rotatable drive
shaft for driving the pump, wherein the pump is a reciprocating pump comprising
at least one pumping unit having a first moving member displaceable in a housing
for sucking well fluid into and out of a first chamber. Furthermore, the inven
tion relates to a wellbore pumping method.
Background art
During gas production, water particles may be present in a well fluid or be pro
duced while being transported up through the wellbore or borehole, and some of
these water particles may condense on the inner face of the wellbore and subse
quently flow along the inner face down to the bottom of the wellbore. In this way,
the water accumulates at the bottom of the well and will subsequently block the
passage of gas from the formation into the wellbore.
When the water has reduced or even stopped the passage of gas from the well
bore, a pump is connected to a drill pipe and lowered into the well in order to
pump the water up through the drill pipe. However, the existing pumping solutions
are very large and require the presence of a drill pipe or similar solutions.
Description of the invention
It is an object of the present invention to wholly or partly overcome the above
disadvantages and drawbacks of the prior art. More specifically, it is an object to
provide a pumping system which is more simple and easier to submerge into a
wellbore without using drill pipes or coil tubing to pump water up from the well.
The above objects, together with numerous other objects, advantages, and features,
which will become evident from the below description, are accomplished by
a solution in accordance with the present invention by a wellbore pumping sy s
tem submerged into a wellbore for unloading liquid from a wellbore comprising
well fluid such as gas, having a wellbore pressure, comprising:
- a pump having an inlet and an outlet,
- a tubing fluidly connected with the outlet of the pump, and
- a driving unit connected with and powered by a cable, such as a wireline, and
having a rotatable drive shaft for driving the pump,
wherein the pump is a reciprocating pump comprising at least one pumping unit
having a first moving member displaceable in a housing for sucking well fluid into
and out of a first chamber.
The wellbore pumping system is a wellbore liquid unloading pumping system for
unloading liquid, such as water, from a bottom of a wellbore comprising well
fluid, such as gas, having a wellbore pressure to a location away from the wellbore,
and wherein the tubing is fluidly connected with the outlet of the pump and
extended to the location. The location may be a rig, a vessel or the water above
the well head. Furthermore, the pump is a submersible pump and the driving unit
is a submersible driving unit.
In one embodiment, the first moving member may divide the housing into the
first chamber and a second chamber.
In another embodiment, the system may comprise a one-way valve arranged be
tween the inlet and the first chamber, and a second one-way valve arranged between
the outlet and the first chamber, enabling liquid to be sucked into the first
chamber and subsequently forced out through the second one-way valve by d is
placing the moving member.
The wellbore pumping system may further comprise a compensator device comprising
a compensator chamber having a compensator moving member displace
able in the compensator chamber and dividing the compensator chamber into a
first chamber section and a second chamber section, wherein the first chamber
section is in fluid communication with the well fluid, and the second chamber of
the reciprocating pump is in fluid communication with the second chamber section.
The purpose of this is to create a pressure equilibrium between the two chambers
to ensure that dirty liquid from the wellbore does not leak into the clean side of
the pump.
In one embodiment, the compensator moving member may be a piston.
Also, the compensator device may comprise at least one flexible element ar
ranged in the first chamber section forcing the compensator moving member t o
wards the pump.
Additionally, the compensator moving member may have a circumferential seal
ing means.
Further, a wellbore pumping system according to the invention may have a systern
housing having openings into which a screen or filter may be arranged pre
venting scales or other particles from entering the compensator device or the
pump and deteriorating their function.
Furthermore, the first chamber may be filled with liquid during pumping of the
liquid, such as water, and the second chamber may be filled with a second liquid.
Additionally, the second liquid may be a dielectric fluid, such as mineral oil, cas
tor oil, Polychlorinated biphenyls, etc.
In one embodiment, the tubing may be made from a non-metallic material.
In another embodiment, the tubing may be made from a material more flexible
than iron or steel.
In yet another embodiment, the tubing may be made from plastic, syntactic or
natural rubber or a composite.
Moreover the pumping unit may be surrounded by a cavity filled with the second
liquid and be in fluid communication with the second chamber of the pumping
unit.
Furthermore, the pump may have a plurality of pumping units, and the moving
members may be arranged so that when one moving member moves in one d i
rection, another moving member moves in an opposite direction.
Additionally, the reciprocating pump may be a radial or axial pump.
In one embodiment of the invention, a first moving member may displace a first
volume of liquid when moved in one direction, and a second moving member
may displace a second volume of liquid when moved in another direction opposite
the first direction, wherein the first and the second volumes are substantially
equal in size.
In another embodiment, a first moving member may displace a first volume of
liquid when moved in one direction, and two or more moving members may displace
a second volume of liquid when moved in one direction, wherein the first
and the second volumes are substantially equal in size.
The wellbore pumping system may further comprise a control unit for activating
the pump.
Furthermore, the control unit may have a measuring unit for measuring the
power used by the driving unit for driving the pump.
If the measuring unit measures that the driving unit uses less power than a predetermined
value, the pump is stopped again. The value is set at the power used
by the driving unit when it drives a pump which pumps up no or only a small
amount of liquid. In this way, it is possible to save power when no or only a small
amount of liquid is present in the wellbore. The system waits a predetermined
period of time and then reactivates the pump while measuring the power. When
the system has activated the pump accordingly at the predetermined time inter
val a predetermined number of times, the time interval is extended
In an embodiment of the invention, the moving member may be a solid or a
flexible member/plate/disk.
Furthermore, the number of moving members may be at least two.
In addition, the measuring means may be used for detecting the level of energy
consumption during the pumping activity.
Moreover, the control unit may comprise a receiving means for receiving the level
of the energy consumption or power needed for driving the pump as well as a
calculator unit for comparing the consumption with a predetermined minor value.
Furthermore, the reciprocating pump may be a diaphragm pump, a piston pump
or a plunger pump.
Additionally, a filter device may be placed in front of or be an integrated part of
the inlet.
In addition, the pump may be activated when a predetermined period of time has
passed since the last stop of the pump.
This period of time may increase from activation to activation or when a prede
termined number of activation attempts have been made if the energy consump
tion or power is lower than the predetermined value.
Furthermore, the time period may be between 5 minutes and 1 month.
The wellbore pumping system may further comprise a fixation means for fixating
the pump inside the wellbore.
Moreover, the driving unit may comprise a starting means which during act iva
tion of the pump may reduce a torque delivered to the drive shaft driving the
pump.
Such a starting means is also called "soft starters" and is used in combination
with AC electrical motors.
Moreover, the driving unit may be an electrical motor or a hydraulic motor.
The wellbore pumping system may further comprise a driving tool for moving the
pumping system inside the wellbore.
Additionally, the driving tool may be a downhole tractor.
In one embodiment of the invention, the drive shaft may be connected with ro
tating cams connected with the first moving member producing reciprocating motion.
Also, the drive shaft may drive several pumps.
In one embodiment, the tubing may have a cross-sectional width being less than
25% of an inner diameter of the wellbore or a casing in the wellbore, preferably
less than 10% of the inner diameter and more preferably less than 5% of the in
ner diameter.
Further, the wellbore system may comprise a wellbore pumping system according
to the invention, and may comprise a driving tool for moving itself and the well
bore pumping system inside the wellbore.
The present invention furthermore relates to a method comprising the steps of:
- entering a wellbore pumping system according to the invention,
- activating the pump,
- measuring the power used by the driving unit for driving the pump,
- determining whether the power is higher than a predetermined value, and
- stopping the pump when the power is lower than the predetermined value.
Finally, the invention relates to a method further comprising the step of react i
vating the pump after a predetermined period of time.
Brief description of the drawings
The invention and its many advantages will be described in further detail below
with reference to the accompanying schematic drawings, which for the purpose of
illustration show some non-limiting embodiments and in which
Fig. 1 shows a wellbore pumping system in a wellbore,
Fig. 2 shows the wellbore pumping system seen from the side,
Fig. 3 shows a partly cross-sectional view along the longitudinal direction of the
system, and
Fig. 4 shows a partly cross-sectional view along the longitudinal direction of the
system of another embodiment of the wellbore pumping system
All the figures are highly schematic and not necessarily to scale, and they show
only those parts which are necessary in order to elucidate the invention, other
parts being omitted or merely suggested.
Detailed description of the invention
Fig. 1 shows a wellbore pumping system 1 according to the invention submerged
into a wellbore 38 for pumping liquid 13 from the wellbore to above surface. The
borehole comprises well fluid 14, such as gas, at a certain wellbore pressure P.
During gas production, water particles may be present in the well fluid or be pro
duced while being transported up through the wellbore or borehole. When pass
ing inside the wellbore, some of these water particles condense on the inner face
of the wellbore and subsequently flow along the inner face down to the bottom of
the wellbore. The gas may also precipitate other liquids than water.
In order to pump the water up from the bottom of the well, the wellbore pumping
system 1 is submerged into the well by means of a wireline, as shown in Fig. 1.
The wellbore pumping system 1 comprises a small flexible tubing 5 in which the
water flows while being pumped to above surface. The tubing has a crosssectional
width wt being less than 25% of an inner diameter Dc of the wellbore or
a casing 39. The cross-sectional width wt of the tubing is less than 25% of the in
ner diameter Dc of the wellbore 38 or the casing 39 in the wellbore, preferably
less than 10% of the inner diameter Dc and more preferably less than 5% of the
inner diameter Dc, and even more preferably less than 2% of the inner diameter.
The wellbore pumping system 1 comprises a system housing 37 comprising a
pump 2 for pumping liquid 13 to above surface or to another place, and the well
bore pumping system furthermore comprises a driving unit 6 used to activate
and drive the pump 2, as shown in Fig. 2. The driving unit 6 is connected to and
powered by a cable 7 which may be part of the tubing 5 or a separate cable, such
as a wireline. Furthermore, the wellbore pumping system 1 comprises a compensator
22 being a compensator device 22 to compensate for the high well pressure
at the bottom of the well. The compensator device 22 supplies the pump 2 with
fluid if the well pressure surrounding the pump increases, ensuring that the walls
of the pump do not collapse. If the pressure drops again, the compensator device
22 is capable of accumulating the fluid inside the pump 2 to ensure that the
pump does not bulge outwards.
The compensator device 22 allows for the pumping system 1 to have thin walls,
causing it to be less expensive to produce. A thin wall construction weighs less
than prior art pumping systems and thus does not put as much stress on the t ub
ing as heavier prior art systems, making it possible to use a smaller tubing.
As shown in Fig. 3, the pump 2 has an inlet 3 for letting liquid 13 into the pump 2
and an outlet 4 which is fluidly connected to the tubing 5 used for transporting
the liquid 13. The pump 2 is a reciprocating pump since this type of pump is a
simple pump which is also capable of pumping small amounts of liquid. Thus, the
pumping system 1 can be used as a permanent system arranged inside the well
during gas production, eliminating the need for an additional larger pumping sy s
tem.
The pump 2 is a radial piston pump comprising two pumping units 8 having a
first moving member 9, such as a piston, being displaceable in a housing 10 and
dividing the housing into a first chamber 11 and a second chamber 12. The liquid
13 is pumped into the first chamber 11 from the weiibore, further out through
the outlet 4 and into the tubing 5. Thus, the first chamber 11 is situated on the
"dirty" side of the moving member 9, and the piston 8 is capable of pushing the
dirt in front of itself when moving towards the inlet 3. In this way, any dirt or undesired
elements are forced to flow with the well fluid 14 when being pumped
back out through the outlet 4.
The second chamber 12 is filled with a second fluid which is cleaner than the well
fluid 14, minimising the risk of dirt from the weiibore entering the vital parts of
the pump 2. The second fluid is often a dielectric fluid also used in transformers
and is therefore also called a "transformer fluid". The second liquid may be a
mineral oil, castor oil, polychlorinated biphenyls (PCBs) or the like.
The pumping unit 8 comprises a one-way valve 15 arranged between the inlet 3
and the first chamber 11 and a second one-way valve 16 arranged between the
outlet 4 and the first chamber 12. The one-way valves 15, 16 are shown as balls
in a ball set but could be any suitable one-way valve. This means that when the
moving member 9 is forced away from the inlet 3, thereby increasing the volume
of the first chamber 11, the well fluid 14 fills the first chamber 11, but when the
moving member 9 moves back towards the inlet 3, the fluid 14 is unable to flow
back in through the inlet 3. The liquid 13 sucked into the first chamber 11 is sub
sequently forced out through the second one-way valve.
The moving members 9 are arranged so that when one moving member moves in
one direction, another moving member moves in an opposite direction. This
means that during one stroke, one piston is in its top position, and the other pis
ton is in its bottom position. The volume VI of the first chamber 11 of one pumping
unit 8 is substantially the same as the volume V2 of the second chamber 12
of the other pumping unit. The top position is the position nearest to the inlet 3
and outlet 4, and the bottom position is the position furthest away from the inlet
3 and the outlet 4. In this way, the volume of the first chamber 11 of one pump
ing unit 8 is the same as the volume of the second chamber 12 of the other
pumping unit. Hereby, one pumping unit feeds the other with the second fluid,
ensuring that the "dirty" well fluid 14 is not sucked into the "clean" side of the
pumping unit 8.
The wellbore pumping system 1 further comprises a compensator device 22, as
shown in Fig. 3. The compensator device 22 comprises a compensator chamber
17 having a compensator moving member 18 acting like a piston displaceable in
the compensator chamber 17 and dividing the compensator chamber into a first
chamber section 19 and a second chamber section 20. The first chamber section
19 is in fluid communication with the well fluid 14 through an opening 23 in the
wall of the chamber and through an opening 24 in the wall of the wellbore pump
ing system 1. The second chamber 12 of the pump is in fluid communication with
the cavity 2 1 surrounding the housing 10 of the pumping units 8 and with the
second chamber section 20. In this way, the well fluid 14 presses on the dirty
side of the compensator moving member 18, equalising the pressure inside the
pump 2 to be equal to the wellbore pressure P.
By having a compensator device 22, the loss of fluid due to leakage is less than
for e.g. known pumps used downhole. Furthermore, the system is more energyefficient,
also in relation to liquids such as oil and water.
The compensator chamber 17 is thus a separate chamber from the cavity 21, and
only the second chamber section 20 is in fluid communication with the cavity 2 1
through an orifice 40.
A screen or filter 30 is arranged in the openings 24 so that scales or other particles
cannot enter the compensator device 22 or the pump 2 and deteriorate their
function.
The compensator moving member 18 is displaceable inside the compensator
chamber 17, and due to a circumferential sealing means 36, such as an O-ring,
arranged between the compensator moving member 18 and the inside wall of the
compensator chamber 17, the dirty well fluid is not mixed with the clean second
fluid inside the pump 2. The compensator moving member 18 is arranged in a
sliding relationship with two sliding rods 25. In this way, the compensator moving
member 18 does not tilt while moving inside the compensator chamber 17 and
furthermore, the compensator moving member 18 is a piston.
On the dirty side of the compensator moving member 18, where the well fluid 14
is, flexible elements 34, such as springs, are arranged around the rods 25 so that
the fluid in the cavity 2 1 surrounding the housings 10 of the pumping units 8 has
a higher pressure than that of the well fluid 14. This ensures that the well fluid 14
does not enter the cavity 21. This is especially useful if the well fluid 14 is very
aggressive. Thus, the compensator device 22 comprises at least one flexible ele
ment 34 arranged in the first chamber section 19 forcing the compensator mov
ing member 18 towards the pump 2.
In order to move the pistons in the housing 10, the driving unit 6 rotates a drive
shaft 26 on which cams 27 are arranged for forcing a piston rod 28 of the piston
up and down or back and forward. Thus, the rotating cam 27 is connected with
the first moving member 9 producing reciprocating motion and the piston rod 28
functions as the cam follower.
The flow paths connecting the openings 24 of the pumping system 1 and the
inlets of the pumping units 8 may be hollow spaces or drilled bores on the side of
the pumping system 1, or a combination thereof. The drive shaft 26 penetrates
the wall between the pump 2 and the driving unit 6 and is arranged with a sealing
arrangement ensuring that the fluid surrounding the driving unit 6, such as a
motor, is not mixed with the second fluid. The fluid inside and/or surrounding the
motor may be the same as the second fluid, meaning that leaks in the transition
between the pump and the driving unit around the drive shaft do not affect the
function of the motor or the pump.
As shown in Figs. 3 and 4, the drive shaft 26 drives several pumps 2 and thus,
the drive shaft is connected with several cams 27 interacting with several pistons
so that when one piston moves away from the inlet 3 sucking fluid into the first
chamber 11, another piston moves towards the inlet 3 equalising the volume of
fluid in the second chamber 12. Hereby, the amount of fluid in the cavity 2 1 is
substantially unchanged. However, some fluid in the cavity may leak through the
first moving member 9 or piston but since the compensator device 22 applies a
certain fluid pressure corresponding to the spring 34, dirty well fluid is not let into
the cavity 21. Thus, the fluid inside the cavity may be sloshed around. However,
the position of the compensator moving member 18 is substantially the same
during the pumping procedure.
The system 1 may have more than two pump units 8 driven by the same drive
means, and the three or more pump units may, in the same way as two pump
units, equalise each other, e.g. when having three pump units, two moving
members may move in one direction and the third in the other direction. The
pump units may vary in displaced volume.
In Figs. 3 and 4, the channels leading up to inlet 3 and away from outlet 4 are
not in the same cross-sectional plane, but the outlet channel 4 is merely shown
as a dotted line for illustration purposes only.
In Fig. 4, the pump 2 is an axial piston pump comprising two pumping units 8.
Each pumping unit 8 has a first moving member 9 displaceable in a housing 10
for sucking well fluid 14 into and out of the first chamber 11. In this embodiment,
the moving member 9 is a piston connected to a cam in the form of an inclined
plate 29 which is rotated by the drive shaft 26 of the driving unit 6. When a piston
9 is retracted towards the driving unit 6 in the housing 10, the volume VI of
the first chamber 11 is increased, and well fluid 14 is sucked into the chamber.
Subsequently, the well fluid 14 is forced out through the outlets 4 and into the
tubing 5 when the piston moves towards the outlet 4.
In Fig. 4, the second chamber 12 of the pump housing 10 is also the cavity 21.
The cavity 2 1 is thus in fluid communication with the rest of cavity 2 1 by a chan
nel 35.
The compensator device 22 has the same design as the compensator device in
Fig. 3, but has one sliding rod 25 instead of two.
As can be seen from Figs. 3 and 4, the pumping system 1 has several openings
for letting well fluid 14 into the pump 2. The system 1 may have openings 24 in
one end of the system 1 as well as along its sides 31. By having openings in the
wall of the pumping system both at the end of the system and along the sides, it
is possible to use the wellbore pumping system 1 even though it is somewhat
tilted and not in an upright position with its longitudinal axis parallel with the lon
gitudinal axis of the wellbore.
The tubing 5 is used for pumping liquid 13, such as water, to above surface and
is made of a non-metallic material, such as plastic, syntactic or natural rubber or
a composite, making it possible to produce small diameter tubing which is flexible
and does not fracture easily. Furthermore, having a flexible tubing ensures that
even if the tubing is bent, it is still possible to pump liquid up through the tubing.
The inner diameter of the tubing is 50-1 mm, preferably 30-5 mm and more
preferably 20-5 mm. The tubing 5 may be in connection with the cable feeding
power to the driving unit 6, e.g. in the form of an umbilical comprising both a
fluid tubing and electrical cables.
When the tubing 5 is made of a material more flexible than iron or steel, making
it possible to produce small diameter tubing, the pump 2 is also capable of pump
ing small amounts of fluid. A thin-walled reciprocating pump according to the
present invention cannot pump the fluid all the way up to above surface if the diameter
of the tubing 5 is too large since the pump 2 cannot not lift a liquid col
umn having a large diameter, such as the diameter of a drill pipe or coiled t ub
ing. The pumps made for drill pipes or coiled tubing are larger pumps designed
for a substantially larger pumping capacity. The design of prior art pumps is
therefore more complex and expensive. However, the pump 2 of the present in
vention has a simpler and less expensive design, meaning that a pump can be
submerged for a longer time period of time and can be discarded when it is not
functioning anymore. The driving unit 6 and the compensator device 22 may be
reused, but may also be disposable, meaning that the entire wellbore pumping
system may be a disposable system.
The amount of power needed for driving the pump 2 is estimated at less than 2
horsepower per day, preferably less than 1.5 horsepower if the well has a depth
of 10,000 feet and accumulates a water rate of 10 barrels per day. If the pump
ing system 1 is submerged for a longer period of time for precautionary reasons,
the pump 2 does not have to be as large as the known pumping systems which
are submerged when production has stopped and need to pump up a large
amount of water very quickly.
In another embodiment, the wellbore pumping system 1 has three pumping units
6, meaning that a first moving member 9 displaces a first volume VI of liquid
when moved in a first direction, and the two other moving members displace a
second volume V2 of liquid when moved in the opposite direction of the first d i
rection, wherein the first and the second volumes are substantially equal in size.
When the first and the second volumes are substantially equal in size, the pump
ing system 1 does not need fixation devices to fixate the system in relation to the
wellbore system since the movements of the moving members counterbalance or
neutralise each other.
As shown in Fig. 1, the wellbore system 1 also comprises a control unit 32 for ac
tivating the pump 2. The control unit 32 is primarily arranged above surface, but
part of it may be arranged in the part of the system being submerged into the
wellbore. The control unit 32 sends a signal to the driving unit 6 to start or stop.
The driving unit 6 comprises a starting means which during activation of the
pump 2 reduces the torque delivered to a drive shaft 26 driving the pump 2. The
control unit 32 furthermore comprises a means for controlling the driving unit 6
to reduce the torque delivered to the drive shaft 26. The starting means is also
called "soft starters" and is primarily used in combination with AC electrical mo
tors. Using a starting means performing a "soft" start eliminates the need for a
fixation device for fixating the system in relation to the wellbore.
Known pumping systems using a fixation means for fixating the pumping system
in relation to the wellbore are more complex in their design since the fixation
means has to be unfolded when the system has been arranged at the bottom of
the hole. If these known pumping systems are not fixated, they risk tilting when
the pump starts, and the risk of a resulting malfunctioning pumping system
thereby increases substantially.
Also, the control unit 32 may have a measuring unit 33 for measuring the power
used by the driving unit 6 for driving the pump 2. If the measurements of the
measuring unit 33 show that the driving unit 6 uses less power than a predeter
mined value, the pump 2 is stopped again. The value is higher than the amount
of power used by the driving unit 6 for driving a pump 2 when the pump pumps
up no or only a small amount of liquid. This makes it possible to save power
when no or only a small amount of liquid is present in the wellbore.
After stopping the driving unit 6, the system 1 waits a predetermined period of
time period and then reactivates the pump 2, while measuring the power. When
the system has activated the pump 2 accordingly at the predetermined time in
terval a predetermined number of times, and the power is still not higher than
the predetermined value, the time interval is extended. In this way, the measur
ing means is used for detecting the level of energy consumption during the
pumping activity, and the control unit 32 controls the driving unit 6 based on the
measured power. Hereby, the wellbore pumping system 1 does not consume any
more energy than required for pumping up the liquid and is thus more env iron
mentally friendly.
If the level of energy consumption during the pumping activity is still lower than
the predetermined value after a predetermined number of activation attempts,
the period of time from activation to activation is increased once again. The time
period is between 5 minutes and 1 month, preferably between 5 minutes and 2
weeks and more preferably between 10 minutes and 1 week.
When in use, the wellbore pumping system 1 is entered into the wellbore, and
when in place, the pump 2 is activated by sending a start signal to the driving
unit 6 to activate the pump. Subsequently, the measuring unit 33 measures the
power or level of energy consumption used by the driving unit 6 for driving the
pump 2. The control unit 32 determines whether the power is higher than a predetermined
value and if it is not, the pump 2 is stopped again. After a predeter
mined period of time, the pump 2 is reactivated, and the power is measured
again. If the power is lower than a predetermined value, the pump 2 is stopped
again. This start and stop procedure is repeated a predetermined number of
times, and then the time period is prolonged. The start and stop procedure may
be repeated 3-30 times, preferably 5-20 times and more preferably 5-10 times
when the power consumption is lower than the predetermined value. The number
of repetitions performed before increasing the time period may vary depending
on the time period.
In order to be able to determine when to start and stop the driving unit 6, the
control unit 32 comprises a receiving means for receiving the level of energy con
sumption X or power required for driving the pump 2 and a calculator unit for
comparing the consumption with a predetermined minor value.
As shown, the reciprocating pump may be a piston pump, but may also be a dia
phragm pump or a plunger pump.
A screen 30 or similar filter device may be placed in front of or as an integrated
part of the inlet 3. It may also be arranged inside the walls of the pumping sy s
tem 1, e.g. in a system housing, so that fluid entering several openings 24 has to
flow through the same screen or filter device.
The wellbore pumping system 1 may comprise a fixation means for fixating the
pump 2 in the wellbore, e.g. if the driving unit 6 does not have a starting means
capable of performing a so-called "soft start".
The driving unit 6 may be any kind of means capable of driving the pump 2.
Thus, the driving unit 6 may be an electrical motor or a hydraulic motor.
The driving unit 6 may also comprise a compensator device ensuring that the
driving unit does not collapse or bulge outwards. Furthermore, if the driving unit
6 is compensated in the same way as the wellbore pumping system 1, the second
fluid surrounding the pump 2 will not penetrate the transition between the pump
and the driving unit where the drive shaft 26 of the driving unit enters the pump.
Nor will the fluid inside the driving unit 6 mix with the second fluid in the pump 2,
since the pressures inside the pump and the driving unit are equal.
By fluid or well fluid 14 is meant any kind of fluid which may be present in oil or
gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By
gas is meant any kind of gas composition present in a well, completion, or open
hole, and by oil is meant any kind of oil composition, such as crude oil, an oilcontaining
fluid, etc. Gas, oil, and water fluids may thus all comprise other ele
ments or substances than gas, oil, and/or water, respectively.
By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used
downhole in relation to oil or natural gas production.
In the event that the system is not submergible all the way into the casing, a
downhole tractor can be used to push the system all the way into position in the
well. A downhole tractor is any kind of driving tool capable of pushing or pulling
tools in a well downhole, such as a Well Tractor®.
Although the invention has been described in the above in connection with pre
ferred embodiments of the invention, it will be evident for a person skilled in the
art that several modifications are conceivable without departing from the inven
tion as defined by the following claims.
Claims
1. A wellbore pumping system (1) submersible into a wellbore for unloading
liquid (13) from a wellbore comprising well fluid (14), such as gas, having a wellbore
pressure, comprising:
- a pump (2) having an inlet (3) and an outlet (4),
- a tubing (5) fluidly connected with the outlet of the pump, and
- a driving unit (6) connected with and powered by a cable (7), such as a wire
line, and having a rotatable drive shaft (26) for driving the pump,
wherein the pump is a reciprocating pump comprising at least one pumping unit
(8) having a first moving member (9) displaceable in a housing (10) for sucking
well fluid into and out of a first chamber (11).
2. A wellbore pumping system according to claim 1, wherein the first moving
member divides the housing into the first chamber and a second chamber
(12).
3. A wellbore pumping system according to claim 1 or 2, wherein the sy s
tem comprises a one-way valve (15) arranged between the inlet and the first
chamber, and a second one-way valve (16) arranged between the outlet and the
first chamber, enabling liquid to be sucked into the first chamber and subse
quently forced out through the second one-way valve by displacing the moving
member.
4. A wellbore pumping system according to any of the preceding claims,
further comprising a compensator device (22) comprising a compensator cham
ber (17) having a compensator moving member (18) displaceable in the compen
sator chamber and dividing the compensator chamber into a first chamber sec
tion (19) and a second chamber section (20), wherein the first chamber section is
in fluid communication with the well fluid, and the second chamber of the recip
rocating pump is in fluid communication with the second chamber section.
5. A wellbore pumping system according to claim 4, wherein the compensa
tor moving member is a piston.
6. A wellbore pumping system according to claim 4 or 5, wherein the com
pensator device comprises at least one flexible element (34) arranged in the first
chamber section forcing the compensator moving member towards the pump.
7. A wellbore pumping system according to any of claims 4-6, wherein the
compensator moving member has a circumferential sealing means (36).
8. A wellbore pumping system according to any of the preceding claims,
wherein the system has a system housing (37) having openings (24) into which a
screen or filter (30) is arranged, preventing scales or other particles from enter
ing the compensator device (22) or the pump (2) and deteriorating their function.
9. A wellbore pumping system according any of the preceding claims,
wherein the first chamber is filled with liquid during pumping of the liquid, such
as water, and the second chamber is filled with a second liquid.
10. A wellbore pumping system according to claim 9, wherein the second liq
uid is a dielectric fluid, such as mineral oil, castor oil, Polychlorinated biphenyls
(PCBs), etc.
11. A wellbore pumping system according to any of the preceding claims,
wherein the tubing is made from a non-metallic material.
12. A wellbore pumping system according to any of the preceding claims,
wherein the pumping unit is surrounded by a cavity (21) filled with the second
liquid and is in fluid communication with the second chamber of the pumping
unit.
13. A wellbore pumping system according to any of the preceding claims,
wherein the pump has a plurality of pumping units, and wherein the moving
members are arranged so that when one moving member moves in one direction,
another moving member moves in an opposite direction.
14. A wellbore pumping system according to any of the preceding claims,
wherein a first moving member displaces a first volume (VI) of liquid when
moved in one direction, and a second moving member displaces a second volume
(V2) of liquid when moved in another direction opposite the first direction,
wherein the first and the second volumes are substantially equal in size.
15. A wellbore pumping system according to any of the preceding claims,
further comprising a control unit (32) for activating the pump.
16. A wellbore pumping system according to claim 15, wherein the control
unit has a measuring unit (33) for measuring the power used by the driving unit
for driving the pump.
17. A wellbore pumping system according to claim 16, wherein the pump is
activated when a predetermined period of time has passed since the last stop of
the pump.
18. A wellbore pumping system according to any of the preceding claims,
wherein the driving unit comprises a starting means which, during activation of
the pump, reduces a torque delivered to the drive shaft driving the pump.
19. A wellbore pumping system according to any of the preceding claims,
wherein the drive shaft is connected with rotating cams (27) connected with the
first moving member producing reciprocating motion.
20. A wellbore pumping system according to any of the preceding claims,
wherein the drive shaft drives several pumps..
21. A wellbore pumping system according to any of the preceding claims,
wherein the tubing has a cross-sectional width (wt) being less than 25% of an in
ner diameter (Dc) of the wellbore or a casing in the wellbore, preferably less than
10% of the inner diameter (Dc) and more preferably less than 5% of the inner diameter
(Dc) .
22. A wellbore system comprising a wellbore pumping system according to
any of the preceding claims, and comprising a driving tool for moving itself and
the wellbore pumping system inside the wellbore.
23. A method comprising the steps of:
- entering a wellbore pumping system according to any of claims 1-21,
- activating the pump,
- measuring the power used by the driving unit for driving the pump,
- determining whether the power is higher than a predetermined value, and
- stopping the pump when the power is lower than the predetermined value.
24. A method according to claim 23, further comprising the step of:
- reactivating the pump after a predetermined period of time.