Note: Descriptions are shown in the official language in which they were submitted.
Y.\CM001\4361 CA\CIPO\Rplcmt Desc 181105.wpd
ARRANGEMENT FOR HYDROCARBON EXTRACTION IN WELLS
USING PROGRESSIVE CAVITY PUMPS
FIELD OF THE INVENTION
This invention refers to an arrangement for hydrocarbon extraction in wells
using
progressive cavity pumps, and more in particular it relates to an oil
extraction tubing
arrangement developed in order to reduce its wearing out as a result of
friction and
corrosion in field wells in which progressive cavity pumps or "PCP" are used.
PRIOR ART AND ADVANTAGES OF THE INVENTION
Within prior art as to this matter, it is worth mentioning that usually in
hydrocarbon extraction field wells, power transmission from the surface engine
to the
bottom pumps "progressive cavity pumps" type, or PCP, is carried out by means
of one
or more metal rods or bars which rotate inside the metal tubing. As the
production well
depth may be of several hundred meters or over one thousand meters, it is
impossible
to avoid certain contact and friction between the tubing and the rods rotating
inside it.
The progressive cavity pump uses the oil which it pumps from the bottom of the
well as
a lubricant between the surfaces which suffer this friction, i.e. between the
internal face
of the tubing and the external face of the rods which rotate along its inside.
One of the
disadvantages arising from the friction between the bottom pump driving rods
and the
tubing appears as oil fields grow old, as the secondary recovery process
increases the
percentage of water in the "water-oil" mixture reaching amounts over 95%,
bringing
about poor lubrication and, in many cases, a combined situation of tubing
wearing out
due to friction and corrosion. As a consequence of the reiterated friction
between rods
and tubing the protective boundary layer breaks up -this layer is formed by
the building
up of a thin deposit of the hydrocarbon present in water and/or by the
artificial injection
of certain film coating product used as non-corrosive, should this latter
method be used-
causing tubing corrosion and wearing out. Therefore, it is extremely important
to solve
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this serious problem as it causes considerable economic losses, clearly
enough, as
exploitation processes at oil fields must be interrupted until tubings are
repaired or
replaced.
With the aim of solving the above mentioned problems, the arrangement subject
matter of this invention has been developed, it allows to considerably reduce
the tubings'
"wearing out-corrosion-wearing out" combined problem, as it shall be explained
below
in the "how to put it into practice" proposal.
SUMMARY OF THE INVENTION
The purpose of this invention is to provide an arrangement for hydrocarbon
extraction in wells using progressive cavity pumps, this arrangement was
developed with
the aim of reducing wearing out as a result of friction and corrosion in
conventional
tubings used in field wells in which the extraction of fluids is carried out
by means of
progressive cavity pumps. This arrangement consists of a rotating tube located
inside
a fixed tube placed along the well casing. The rotating tube carries the fluid
from the
bottom of the well to the surface. Between the rotating tube and the fixed
tube there is
an "0" ring-type space into which an anti-friction lubricant is injected
between the
external face of the rotating tube and the internal face of the fixed tube.
The bottom end
of the rotating tube has a section with holes which allow fluids to flow into
it and it is
connected to the progressive cavity pump by means of a rod, its top end is
connected
to a production outlet and to its propelling motor mechanism. The upper
section of the
fixed tube is connected to an anti-friction lubricant injection pipe in the
space left
between the rotating tube and the fixed tube.
In one aspect, the present invention provides an assembly for use with an oil
field
well having a well head, a well casing, a production zone within the well, a
production
outlet at the well head and a propelling motor mechanism at the well head; the
well
casing extending between the well head and a progressive cavity pump located
in the
production zone, the progressive cavity pump having a stator and a rotor, the
assembly
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including: a fixed tube having an inner wall, the fixed tube disposed within
the well
casing and extending between the vicinity of the well head and the vicinity of
the
progressive cavity pump, and the fixed tube fixed relative to the well casing;
a rotatable
tube having an outer wall, a bottom end and a top end, the rotatable tube:
disposed
within the fixed tube, defining a rotatable tube fluid conduit extending
between the
vicinity of the well head and the vicinity of the progressive cavity pump, and
rotatable
relative to the fixed tube; the fixed tube inner wall and the rotatable tube
outer wall
defining an anti-friction lubricant container; the fixed tube having an anti-
friction lubricant
injection inlet in the vicinity of the well head for receiving anti-friction
lubricant into the
anti-friction lubricant container; the rotatable tube bottom end having:
rotatable tube
bottom end holes in fluid communication with the rotatable tube fluid conduit
for
receiving fluid from the production zone; and connecting pump-drive means for
connecting the rotatable tube bottom end to the rotor; the rotatable tube top
end having,
in the vicinity of the well head: connecting fluid means for fluid
communication between
the rotatable tube fluid conduit and the production outlet; and connecting
rotatable-tube-
drive means for drivably connecting the rotatable tube to the propelling motor
mechanism; wherein, in use, the rotatable tube is rotated by the propelling
motor
mechanism which in turn rotates the rotor, causing fluid from the production
zone to flow
into the rotatable tube fluid conduit via the rotatable tube bottom end holes
and thence
to the production outlet.
The connecting fluid means may include a swivel to accommodate rotation of the
rotatable tube and the connecting rotatable-tube-drive means may be located
between
the swivel and the rotatable tube bottom end.
The rotatable tube may include a series of interconnected sections attached
one
to another by threaded joints.
The rotatable tube fluid conduit may include a conduit wall having a
protective
paint coating.
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The rotatable tube may include 2 3/8-inch API standard pipe and the fixed tube
may include 2 7/8-inch API standard pipe.
The rotatable tube may have an 1.88-inch external diameter and the fixed tube
may have a 2 3/8-inch internal diameter.
In use, an anti-friction lubricant injection inlet having a viscosity of SAE
10 may
be injected in the anti-friction lubricant injection inlet.
The connecting pump-drive means may include a rod interposed between and
interconnecting the rotatable tube bottom end and the rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding and clarity of the purpose of this invention, it
has been
illustrated in several drawings which represent it according to the preferred
ways in
which to carry it out, all of them should be taken as examples, that is:
Figure 1 outlines a typical example of a conventional arrangement for
hydrocarbon extraction in wells using progressive cavity pumps.
Figure 2 outlines the arrangement for hydrocarbon extraction in wells using
progressive cavity pumps, subject matter of this invention.
Figures 3 to 6 respectively show the blown up details A, B, C and D of the
arrangement shown in Figure 2.
It is worth mentioning that in Figure 1, corresponding to the prior art, and
in the
following figures in which this invention is illustrated the same or
equivalent parts are
indicated with the same reference numbers in both cases.
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DETAILED DESCRIPTION
Figure 1 shows that the illustrated example of a conventional pumping
arrangement consists of a casing 1, with a wellhead outlet 2, which holds
inside a tubing
3, which carries the fluid from the bottom of the well to the surface, formed
by a
succession of sections 4 connected among them by joints 5. Between the casing
1 and
the tubing 3 there is a longitudinally defined "0" ring-type space 13. The
upper section
4 of the tubing 3 which projects itself from the wellhead at the field's land
T surface has
a production outlet 6, through which the first of a succession of rods 8
connected among
them by joints 9 passes as well as through a stuffing box 7, the last rod 8 at
the tubing's
lower section 4 is connected to a bottom PCP pump 10. In order to drive the
rotating
movement of the group of rods 8, and consequently to drive the pump 10, the
upper rod
8 is connected to an electric engine 11 by means of a belt-and-pulley
transmission
mechanism 12.
As it has already been stated, the pump 10 uses the oil which it pumps from
the
bottom of the well as a lubricant between the surfaces subject to friction,
i.e. between
the internal face of the tubing 3 and the external face of the rods 8 which
rotate along
its inside. As oil fields grow old the percentage of water present in the
"water-oil" mixture
increases, thus lubrication becomes poor causing the tubing's wearing out as a
result
of friction and corrosion until the protective boundary layer, formed as a
consequence
of the building up of a thin deposit of the hydrocarbon present in water,
breaks up.
In Figure 2 the way in which this invention solves the problem of the wearing
out
of the pumping rods due to friction and their resulting corrosion is shown. As
a matter
of fact, the herein proposed arrangement, aimed at solving such problems,
consists of
a rotating tube 14 located inside a fixed tube 15, between which a space is
left which
serves as a lubricant oil container, as it can be seen in figure 3, detailed
under reference
A in this figure 2. For the injection of the lubricant oil, the top end of the
fixed tube 15 is
connected to a pipe 22 which can be accessed from land T surface.
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In the preferred way of carrying it out which is described and drawn, tubing
14 has
a 2 3/8-inch section and tubing 15 has a 2 7/8-inch section, which is enough
to achieve
the necessary lubrication in order to avoid the wearing out of tube 14 as a
result of
friction with tube 15. That is to say, the invention comprises a casing with
the necessary
length to transform the well into a giant bearing which shall operate
protected by the
layer of lubricant oil which is injected from the outside. In this way, the
tubing's internal
wearing out, as a result of rods' friction, and the accelerated tubing's
corrosion, as it
occurs in conventional arrangements, are avoided.
Tube 15 is made up of a succession of sections connected by means of joints 5,
as shown in figure 4 corresponding to detail B in figure 2. Tube 14 is made up
of a
succession of sections connected by means of joints 16, as shown in figure 5
corresponding to detail C pointed out in figure 2.
The upper section of tube 14 has a diameter reduction 17 from where it is
connected to a pipe 18 with an articulated joint or "swivel" which ends at the
production
outlet 6. The lower section of tube 14 shows an end defined by an end tube 19
with
holes 30 through which the fluid extracted by the pump 10 flows, said pump is
connected to such lower section of tube 14 by means of a rod 20. In figure 6
tube 19 is
enlarged and is indicated in figure 2 under reference D, where its holes 30
can be clearly
seen.
Tube 14 transmits output power and carries 100% of the fluid extracted from
the
bottom of the well to the surface along its inside. The oil film 21 between
both tubes 14
and 15 (see figure detail) prevents tube 15 internal corrosion and tube 14
external
corrosion. In addition, a paint coating on the internal face of tube 14, which
carries the
fluid, contributes to prevent internal corrosion caused by it. The only
modification on
tube 14 consists in the structure of the threaded joint 16, by adapting the
connecting
nipple (see detail C in figure 5) which allows to link both tubes without
modifying their
external diameter.
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In summary, the arrangement, subject matter of this invention, basically
consists
of the use of two tubes, 14 and 15, API standard manufacturing, of 2 3/8-inch
and 2
7/8-inch respectively, which jointly form a "hydraulic bearing" from the
surface to the
bottom of the well, which can be lubricated by filling the ''0" ring space
between both
tubes with clean oil and with the desired viscosity, for example SAE 10. This
lubricant
prevents corrosion and attenuates the wearing out between both tubes 14 and
15. This
arrangement also allows the flowing of all the fluid produced along the inside
of tube 14
with no internal moving parts, thus allowing the application of a paint
coating in its inside
in order to avoid internal corrosion. Also, a similar arrangement could be
arranged with
tubes holding different diameters, for example 1.42-inch internal diameter,
1.88-inch
external diameter within a 2 3/8-inch internal diameter tube, or in other
diameters,
obtaining the same and before mentioned "hydraulic bearing" effect.
In this way important advantages are achieved as compared to already known
and used arrangements, such as:
- By increasing the contact area between the two frictioning surfaces, contact
pressure
decreases. This contact pressure causes wearing out, thus having less contact
pressure
results in less wearing out ("hydraulic bearing" effect).
- It allows to reduce the number of revolutions per minute of the rotating
tube 14 which
transmits power, as it bears higher torsion for holding a bigger diameter than
the rods
in conventional arrangements, giving it a greater moment of inertia, thus
allowing a
reduction in the number of friction cycles originated by the rotation
frequency for the
same power applied, since by transmitting higher torque it is able to rotate
at a slower
speed resulting in a lower number of wear-out cycles.
- It allows to add an artificial lubricant, chosen by the user, between both
frictioning
surfaces, i.e. between tubes 14 and 15.
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- It allows to do without rods inside the tube which carries production
towards the
surface, thus being able to apply paint to prevent corrosion on its internal
face.
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