Note: Descriptions are shown in the official language in which they were submitted.
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MECHANICALLY ACTUATED TRAVELING VALVE
TECHNICAL FIELD
A mechanically actuated traveling valve for use in fluid pumping equipment is
provided. More particularly, a multiple component traveling plug valve is
provided
for use in subsurface positive displacement pumps capable of pumping high
viscosity fluids, with any gas to liquid ratio, operating at any inclination
angle.
BACKGROUND
In the oil industry, various types of subsurface pumps are used for extracting
crude
oil from the reservoir to the surface. Among conventional artificial lift
systems, the
most prevalent type are mechanically driven subsurface pumps activated by
means of a sucker rod string from the surface via beam pumping or other
pumping
units. Such pumps are capable of handling very high reservoir temperatures
resulting from advanced recovery techniques (e.g., the injection of steam or
in-situ
combustion to lower the viscosity of the heavy and extra heavy crude oil). Due
to
the limited diameter of mechanical subsurface pumps and the number of strokes
per unit of time at which they can operate, it is essential to achieve maximum
volumetric efficiency at each pump stroke.
In mechanically actuated positive displacement subsurface pumps, the valve
attached to the component that induces reciprocating motion is known as the
traveling valve; while, the valve attached to the stationary component is
known as
the standing valve. The traveling and standing valves are basically retention
valves
arranged so that both allow fluid flow in the same direction. Consequently,
the
relative motion between these two valves produces the pumping action.
Mechanical pumps can be configured such that valve elements act as a plug and
a seat, where fluid flows in one direction when the plug becomes separated
from
the seat by the pressure differential at both sides of the valve. The plug and
seat
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may have any shape; provided that there must be a hermetic seal between them,
in order to prevent reverse flow, when the valve is closed. Currently, the
most
commonly used configuration in the oil industry for the plug is a ball or
sphere
referred to as a "ball and seat" valve.
In order to allow interchangeability between manufacturers, the American
Petroleum Institute (API) established the Standard API 11AX, which
standardizes
threads and tolerances of valve elements, but does not take into account the
design nor the flow areas through the various components of subsurface pumps.
When pumping crudes with high gas to oil ratio, conventional subsurface pumps
with ball and seat valves are somewhat inefficient. Due to pressure drops that
occur between the traveling and standing valves within the subsurface pump in
the
suction phase, part of the gas separates from the oil and creates a gas
chamber
between the traveling valve and the oil flowing across the standing valve.
Since
both valves require a pressure differential for the ball to separate from the
seat, it
is necessary to compress the gas during the discharge phase until the gas
pressure inside the pump cylinder exceeds the pressure of the fluid column
downstream the traveling valve. In most cases, the mobile component can
plummet the oil causing a strong fluid pound effect, harming the pump and
decreasing its lifespan. Attempts have been made to overcome this problem,
including affixing an annular valve to the discharge end of the cylinder to
support
the counter pressure generated by the weight of the oil column, significantly
reducing the pressure differential required to open the traveling valve by the
gas
trapped between the traveling valve and the liquid phase of the crude oil and
increasing, to some extent, the volumetric efficiency of the pump.
Attempts have also been made to address the low volumetric efficiency when
pumping fluids with high gas to oil ratio. For example, valves having a single
plug
and seat have been developed where the plug (directly connected to the sucker
rod string through a rod) is forced to move with a reciprocating motion
induced
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from the surface by a beam or other pumping unit, while the plunger moves
freely
between the plug and a stop. In this case, the plunger can have a seat
attached to
it, such that whenever the plug contacts the seat, a seal is formed, and when
they
separate the fluid is able to flow. In such systems, the plug can be separated
from
the seat due to: (i) the weight of the sucker rod string which acts directly
on the
plug, (ii) the pressure differential between the suction side and the
discharge side
of the traveling valve, and (iii) the friction between the plunger and the
pump barrel
acting on the moveable component. Such valves can open much faster and are
more efficient than ball and seat valves (including subsurface pumps with
annular
valve); however, annular valves could also be implemented were high gas to oil
ratios exist.
Many configurations of pumps having single plug and seat traveling valves
exist,
including the VRSTM disclosed in United States Patent Nos. 4,591,316,
4,708,597'
and 5,048,604, Canada Patent No. 1,221,875, and the LOCK-NO plunger
manufactured by the HARBISSON FISHER Company. United States Patent No.
5,044,395 teaches the implementation of a plug, a seat, and one or several
seating
rings operable as a check valve that offers minimum pressure drop and the
maximum possible flow area in a confined cylindrical space. In such valves,
the
fluid passes in one direction when the intake end of the plug separates from
the
discharge end of the first ring, while the intake end of the same ring
separates from
the discharge end of the subsequent ring or rings, depending if there is more
than
one ring. If there is more than one ring, the fluid is not allowed to return
when the
intake end of the plug seals against the discharge end of the first ring,
while the
intake end of the same ring seals against the discharge end of the second
ring,
and so on, until the intake end of the last ring seals against the discharge
end of
the seat. As such, the standing valve using one or more rings between the plug
and the seat, and the resulting incremented flow area, enables the valve to
handle
higher viscosity fluids.
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United States Patent Nos. 4,591,315 and 4,740,141 teach composite retention
valves located specifically at the intake of the plunger, which opens and
closes
mechanically for the single plug and seat retention valves, but with much
greater
flow areas. These composite retention valves have the seat attached to the
suction
end of the plunger, while the rings and the reciprocally actuated plug (by
means of
a rod that ran across the plunger) are altogether outside said plunger.
Such single plug and composite retention valves require that the traveling
valves,
rather than the plunger, plunge into to the liquid phase of the fluid within
the pump
chamber. However, if the intake end of the plunger contacted the fluid before
the
traveling valve, then the drag force acting on the plunger could aid in an
earlier
opening of the valve and at the same time extend its useful life, since the
fluid
pound would be on the plunger and not on the sealing elements of the valve.
Conventional pumps have been somewhat successful to meet the pumping
requirements of fluids with high gas to oil ratio, produced in vertical or
slightly
deviated wells; however, known pump designs can become somewhat inefficient
when pumping oil of: (a) very high viscosity, (b) medium or high viscosity
with
steam due to the injection of steam into the well or adjacent wells to lower
the
viscosity of heavy and extra heavy crude oil, (c) any viscosity particularly
with high
gas to oil ratio, or (d) any viscosity in horizontal or highly deviated wells.
zo There is a need for valve design for increasing the performance of
mechanically
actuated positive displacement subsurface pumps, the valve being capable of
significantly reducing oil seepage and being able to pump a greater amount of
fluid.
Such a valve may comprise' plug and seat sealing elements, where the sealing
elements may comprise at least one annular sealing element positioned between
the plug and sealing elements. Such a configuration may provide for a
considerable increase in the valve flow area.
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SUMMARY OF THE INVENTION
Pumping crudes of high viscosity using conventional mechanical positive
displacement pumps can be inefficient due to the low pumping rate imparted on
the pumping system as a direct consequence of flow area restrictions across
pump
valves, a problem that is further aggravated where gas and/or steam are
present
in the fluid being pumped. Moreover, if the pump must work at any significant
deviation angle from the vertical, the pumping efficiency can also be affected
by
the increased seepage of fluid across the sealing elements of both standing
and
traveling valves.
A mechanically actuated traveling valve is provided having a plug, a seat, and
at
least one or more displaceable valve rings. According to embodiments herein,
intermittently at each valve during the suction and discharge phases, the plug
can
form a seal against a first displaceable ring adjacent thereto, each ring can
form a
seal against the next ring adjacent thereto (e.g. where more than one ring is
provided in series), where the other end of the ring or the last ring in
series can
form a seal against the seat. In this arrangement, the sum of the annular flow
area
outside each ring plus the flow area inside the same ring may be substantially
similar to the entire flow area of the seat. The present valve configuration
can
permit a substantial flow area increment across the fluid passages of both
standing
and traveling valves, permit a larger number of strokes per unit of time, and
consequently increase the amount of fluid that can be pumped in the same time
period.
The present traveling valve can be located within the moveable (e.g.
reciprocating)
component of the pump. In such embodiments, the valve can comprise a
reciprocating valve stem having a first end and a second end, and having an
outer
periphery, a valve stem reciprocating means (i.e. a reciprocating motion
inducing
element) connected to the valve stem by a valve connector for imparting
reciprocating movement from the reciprocating means to the valve stem, a valve
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seat secured within the housing, the valve seat having an inner periphery,
where
the inner periphery of the valve seat and the outer periphery of the valve
stem
define a first fluid flow area, a valve plug connected to the valve stem at
its second
end, the valve plug having an outer periphery, where the outer periphery of
the
valve plug and the inner periphery of the housing define a second annular
fluid
flow area, and at least one displaceable valve ring having an internal and
external
periphery, the internal periphery of the valve ring(s) and the outer periphery
of the
valve stem defining a third fluid flow area, and the external periphery of the
ring(s)
and the internal periphery of the housing defining a fourth fluid flow area,
wherein
3.0 the size or capacity of the first fluid flow area is substantially
equal to or smaller
than that of the second fluid flow area, and substantially equal to the sum of
the
third and fourth fluid flow areas. Reciprocating movement of the valve stem
opens
and closes the valve. As such, the valve will open primarily due to the force
exerted
thereon by the reciprocating motion inducing element on the valve stem, in
addition
to any pressure differential across the valve and the friction between the
plunger
and the pump cylinder, enabling the gas of highly gaseous fluids to be handled
more adequately. Further, because the reciprocating movement of the valve stem
opens and closes the valve, it is contemplated that the present valve (and
pump)
can operate efficiently at any inclination angle.
zo Other objects, advantages and features of the present invention will
become clear
from the following detailed description of the invention when read in
conjunction
with the drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view through the mechanically actuated
traveling
valve according to embodiments herein, the valve being in the "open" position;
FIG. 2 is a longitudinal sectional view through the mechanically actuated
traveling
valve according to embodiments herein, the valve being in the "closed"
position;
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FIG. 3 is a longitudinal sectional view of the mechanically actuated traveling
valve
used in a positive displacement subsurface pump showing an embodiment having
one ring;
FIG.4 is a longitudinal sectional view of the standing valve used in a
positive
displacement subsurface pump showing an embodiment having one ring;
FIG. 5 is a longitudinal sectional view of a positive displacement subsurface
pump
having its valves in the open and closed position during "Discharge" and
"Suction"
stages where the plunger is the moveable component and the barrel is the
stationary component; and
3.0 FIG. 6 is a longitudinal sectional view of a positive displacement
subsurface pump
having its valves in the open and closed position during "Discharge" and
"Suction"
stages where the barrel is the moveable component and the plunger is the
stationary component.
DESCRIPTION OF THE EMBODIMENTS
Mechanically actuated positive displacement pumps or compressors can comprise
at least one traveling and one standing valve. Traveling valves can be
positioned
within the reciprocally moving portion of such pumps or compressors (e.g.
along
the pump plunger or cylinder). According to embodiments herein, the present
mechanically actuated traveling valve can be located anywhere within the
length
of the plunger, when said plunger is the moveable component or within the
discharge end of the pump cylinder, when said cylinder is the moveable
component. Although reference herein is made to mechanically actuated
subsurface pumps used in the oil industry, embodiments of the present system
can be operable with any other positive displacement pump or compressor.
More specifically, the present mechanically actuated traveling valve may be
fixedly
attached within the moveable component of the positive displacement subsurface
pump, resulting in two possibilities: Case A, in which the plunger is the
moveable
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component and the pump cylinder or barrel (according to Standard API 11AX
nomenclature) is the stationary component, and Case B, in which the barrel is
the
moveable component, and the plunger is the stationary component. The present
mechanically actuated traveling valve can be implemented in positive
displacement subsurface pumps and can operate at any deviation angle.
Having regard to FIGS. 1 and 2, a mechanically actuated traveling valve 100
for
providing an increased flow area and minimum pressure drop is provided, in
open
position (FIG. 1), and in the closed position (FIG.2). Valve 100 comprises
valve
seat 110, valve connector 120, valve stem 130, valve plug 140, first hollow
valve
ring 150a, second hollow valve ring 150b and the i-th or last hollow valve
ring 1501.
The valve is housed at the discharge end of both plunger 50 for Case A and
barrel
60 for Case B. Valve plug 140 can be part of or be attached by any means to
valve
stem 130 which at the same time is attached by any means to valve connector
120. In embodiments herein, between valve plug 140 and valve seat 110 there is
a plurality of hollow valve rings 150a, 150b, 1501. These hollow valve
rings are
limited by any means to open to a specific distance from one another and
contact
each other through their sealing surfaces when closed. The farthest position
of
valve plug 140 from valve seat 110, defines the traveling valve chamber 105.
Valve connector 120 serves to induce the reciprocal motion from the
reciprocating
motion inducing element 30 (e.g., in the oil industry, the last sucker rod or
the rod
valve) to valve stem 130. Valve connector 120, valve plug 140 and hollow valve
rings 150a, 150b, ..., 150i can be guided by any means in order to assure that
when traveling valve 100 is closed, the sealing surfaces of valve seat 110 and
the
plurality of hollow valve rings 150a, 150b,..., 1501 seal against each other
and the
ith or last hollow valve ring 1501 seals against valve plug 140.
In embodiments herein, valve 100 can be configured to minimize pressure drop
and maximize flow area across the valve 100. This can be accomplished by
arranging annular flow area Ad, defined by the inner peripheral surface 112 of
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valve seat 110 and the outer peripheral surface 132 of valve stem 130, to be
substantially equal to or smaller than annular flow area As defined by the
outer
peripheral surface 142 of valve plug 140 and the inner peripheral surface 55
of
plunger 50 in Case A or of barrel 60 in Case B. Further, this can be
accomplished
by arranging that for each of the hollow valve rings 150a, 150b, ..., 1501,
the sum
of their external annular flow area Ahj (where j = a, b, i)
defined by the outer
peripheral surface 152a, 152b, ..., 152i of each hollow valve ring 150a, 150b,
1501 and the inner peripheral surface 55 of plunger 50 in Case A or of barrel
60 in
Case B, plus their internal annular flow area Arj (where j = a, b, i)
defined by
the outer peripheral surface 132 of valve stem 130 and the inner peripheral
surface
154a, 154b, 1541
of each hollow valve ring 150a, 150b, ..., 1501, be
substantially equal to annular flow area Ad for the first valve ring 150a, and
substantially equal to or greater than annular flow area Ad for subsequent
rings
150b,..., 150i. This enables the number of hollow valve rings to be
determined,
since if more rings are used, the inner diameter 112 of valve seat 110 will
increase
and at the same time the outer diameter 142 of valve plug 140 will decrease.
It
should be understood that the additional flow area attained with the addition
of
another hollow valve ring may only provide a slight increase in annular flow
area
Ad within valve seat 110. Since the first hollow valve ring provides the most
significant flow area increment with respect to other traveling valves that
use only
one sealing element, subsurface pump sizes commonly used in the oil industry
may utilize at least one hollow valve ring.
As can readily be seen in FIG. 1, when a plurality of hollow valve rings 150a,
150b,
..., 1501 are employed, they can be disposed in series between valve plug 140
and
valve seat 110 and the internal annular flow area Arj (where j = a, b, i)
of each
hollow valve ring decreases while the external annular area Ahj (where j = a,
b,
i) of each hollow valve ring increases as the hollow valve rings progress from
valve seat 110 toward valve plug 140. In addition, with particular reference
to FIG.
2, it can be seen that when the valve is in closed position, the discharge end
of the
first hollow valve ring 150a seats on the intake end of valve seat 110 in a
sealing
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manner, while the discharge end of the second hollow valve ring 150b seats in
a
sealing manner on the intake end of the first hollow valve ring 150a, and so
on until
the discharge end of valve plug 140 seats in a sealing manner on the intake
end
of the ith or last hollow valve ring 1501. The foregoing is accomplished
because the
outside diameter of the first hollow valve ring 150a should be greater than
the
inside diameter of valve seat 110, while the outside diameter of the second
hollow
valve ring 150b should be greater than the inside diameter of the first hollow
valve
ring 150a, and so on until valve plug 140, where the outside diameter of said
valve
plug 140 should be greater than the inside diameter of the ith or last hollow
valve
ring 1501. A preferred sealing surface of the components herein corresponds to
a
spherical zone, allowing for slight angular misalignment without breaking up
the
seal; however, it should be understood that the sealing surfaces might have
any
other configuration, including line contact rather than surface contact,
provided that
when two sealing elements are in contact with each other, a perfect seal is
maintained. This insures that the pressure drop across the traveling valve is
minimized and the flow through the valve body is maximized.
The minimum distance at which one hollow valve ring separates from the next
one
when the mechanically actuated traveling valve 100 is in its open position is
established by the internal annular flow area Ark (where k = a, b, m,
and m is
the hollow valve ring next to the ith or last hollow valve ring 1501) of the
largest of
the two hollow valve rings; in the sense that the surface of revolution
(conical) flow
area at the opening between the hollow valve rings be equal or greater than
said
internal annular flow area Ark (where k = a, b, m,
and m is the hollow valve
ring next to the ith or last hollow valve ring 1501) of the largest of the two
hollow
valve rings.
The minimum distance at which valve seat 110 separates from the first hollow
valve ring 150a when the mechanically actuated traveling valve 100 is in its
open
position is established by the internal annular flow area Ad of valve seat 110
and
the internal annular flow area Ara of the first hollow valve ring 150a; in the
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that the conical surface of revolution flow area at the opening between valve
seat
110 and hollow valve ring 150a be equal or greater than the internal annular
flow
area Ad of valve seat 110 minus the internal annular flow area Ara of the
first
hollow valve ring 150a.
The minimum distance at which valve plug 140 separates from the ith or last
hollow
valve ring 1501 when the mechanically actuated traveling valve 100 is in its
open
position is established by the internal annular flow area An of hollow valve
ring
1501; in the sense that the conical surface of revolution flow area at the
opening
between valve plug 140 and the ith or last hollow valve ring 150i be equal or
greater
than the internal annular flow area An of the ith or last hollow valve ring
1501.
In order to maximize pumping efficiency, the surfaces of valve plug 140,
hollow
valve rings 150a, 150b, ..., 150i, and valve seat 110 which will be contacted
by
the flowing fluid, should be as smooth as possible so as to reduce drag and
thereby
reduce the pressure drop which may occur as the fluid passes over these
surfaces.
Since the traveling valve 100 operates mainly mechanically (that is, it will
open and
close in a forced manner), the valve can be positioned anywhere within the
entire
length of plunger 50. A preferred positioning of the mechanically actuated
traveling
valve 100 in Case A can be at the discharge end of plunger 50; while for case
B,
the location of said mechanically actuated traveling valve 100 can only be at
the
discharge end of the moveable barrel 60.
By providing a mechanically actuated, multiple component traveling valve,
pressure drop across the valve can be minimized and flow area can be
maximized,
thus maximizing flow through the valve thereby maximizing pumping efficiency
and
prohibiting the phenomena of gas lock and/or steam lock.
The mechanically actuated traveling valve object of this invention that offers
the
greatest flow area and minimum pressure drop for the moving component, when
used with any currently available standing valve, will improve significantly
the
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pump's performance; however, when used in conjunction with the standing valve
that offers the greatest flow area and minimum pressure drop for the
stationary
component, as described in Patent No. 5,044,395 by the author of this
invention,
the most efficient positive displacement subsurface pump will be produced.
Having regard to FIG. 3, the mechanically actuated traveling valve 100 can be
fixedly attached by any means to the moveable element. In such embodiments of
the valve 100 can comprise valve seat 110, a single hollow valve ring 150,
valve
plug 140, valve stem 130 and valve connector 120, each having a collinear axis
and moving along the subsurface pump's longitudinal axis 500 where hollow
valve
lo ring 150 moves between valve plug 140 and valve seat 110.
Valve 100 can comprise an annular flow area 300 around valve plug 140 that can
be determined by the inner peripheral surface 55 of plunger 50 in Case A or
barrel
60 in Case B and the outer peripheral surface 142 of valve plug 140. The
annular
flow area 310 at valve seat 110 is determined by the inner peripheral surface
112
of valve seat 110 and the outer peripheral surface 132 of valve stem 130.
Since
the annular flow area 300 around valve plug 140 must be substantially equal to
the
annular flow area 310 within valve seat 110, the internal diameter of valve
seat
110 and the external diameter of valve plug 140 can be determined for a
specified
outer diameter 134 of valve stem 130 and a specified inner diameter 57 of
plunger
.. 50 in Case A or barrel 60 in Case B. The outer diameter 134 of valve stem
130 will
depend on the yield strength of the selected material plus whatever safety
factor
is considered appropriate. The inner diameter 57 of plunger 50 for Case A or
of
barrel 60 for Case B can be established by the plunger and barrel
manufacturers
and/or standards known by those skilled in the art.
The outer annular flow area 320 of hollow valve ring 150 can be determined by
the
inner peripheral surface 55 of plunger 50 for Case A or of barrel 60 of Case
Band
the outer peripheral surface 152 of hollow valve ring 150. The inner annular
flow
area 330 of hollow valve ring 150 is determined by the inner peripheral
surface
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154 of hollow valve ring 150 and the outer peripheral surface 132 of valve
stem
130. The sum of the outer annular flow area 320 of hollow valve ring 150 plus
the
inner annular flow area 330 of the same hollow valve ring 150 can be
substantially
equal to the annular flow area 300 around valve plug 140. This establishes
both
the outer and inner diameter of hollow valve ring 150, taking into
consideration the
overlap that exists between: (i) the outer diameter 155 of hollow valve ring
150 and
the inner diameter 116 of valve seat 110, such that when the valve is closed
both
contacting surfaces 158 of hollow valve ring 150 and 114 of valve seat 110
make
a perfect seal, and (ii) the outer diameter 146 of valve plug 140 and the
inner
diameter 153 of hollow valve ring 150, such that when the valve is closed both
contacting surfaces 144 of valve plug 140 and 156 of hollow valve ring 150
also
create a seal. The contacting surfaces 158 of hollow valve ring 150 and 114 of
valve seat 110, as well as the contacting surfaces 144 of valve plug 140 and
156
of hollow valve ring 150, correspond to spherical segments, ensuring that any
slight angular misalignment between the sealing elements will maintain a seal.
The inner annular flow area 330 or Ai of hollow valve ring 150 determines the
minimum separation distance 340 or Hp between the intake end of hollow valve
ring 150 and the discharge end of valve plug 140. This minimum separation
distance 340 can be determined from the conical surface of revolution 350 that
is
generated between the overlap of sealing surface 156 of hollow valve ring 150
and
sealing surface 144 of valve plug 140. The large diameter Dp of conical
surface of
revolution 350 corresponds to the outer diameter 146 of valve plug 140, while
the
minor diameter Di of this same conical surface of revolution 350 corresponds
to
the inner diameter 153 of hollow valve ring 150. Once these parameters are
established, the minimum separation distance 340 or Hp can be determined from
Equation 1:
4 Ai 2 (Dp ¨ Di) 2
Hp= Square Root ( ---------------------------------------- (Eq. 1)
7r2 (Dp + Di) 2 4
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Thus, the separation distance 340 or Hp calculated in Equation 1 must be
greater
than or equal to the minimal distance attained with the above relationship.
The annular flow area 310 or As of valve seat 110 minus the inner annular flow
area 330 or Al of hollow valve ring 150 determine the minimum separation
distance
360 or Hs between the intake end of valve seat 110 and the discharge end of
hollow valve ring 150. This minimum separation distance 360 can be determined
from the conical surface of revolution 370 that is generated between the
overlap
of sealing surface 158 of hollow valve ring 150 and sealing surface 114 of
valve
seat 110. The large diameter Ds of conical surface of revolution 370
corresponds
to the outer diameter 155 of seat 150, while the minor diameter Do of this
same
conical surface of revolution 370 corresponds to the inner diameter 116 of
valve
seat 110. Once these parameters are established, the minimum separation
distance 360 or Hs can be determined from Equation 2:
4 (As ¨ Ai) 2 (Ds ¨ Do) 2
Hs = Square Root ( ----------------------------- (Eq. 2)
TC2 (Ds + Do) 2 4
Thus, the separation distance 360 or Hs calculated in Equation 2 is greater
than
or equal to the minimal distance attained with the above relationship.
FIG. 4 shows the standing valve 200 used in one embodiment of a subsurface
zo pump. Valve 200 can be fixedly attached by any means to the stationary
component of the subsurface pump, for e.g., a standing valve body 270, said
body
being a separate component or simply the internal diameter of barrel 60 of the
subsurface pump. For explanation purposes, it is shown as a separate
component.
Valve 200 can comprise a valve seat 210, a single hollow valve ring 250 and a
valve plug 240, each having collinear axis and moving along the subsurface
pumps
longitudinal axis 500, where hollow valve ring 250 moves between valve plug
240
and valve seat 210. =
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In standing valve 200, the annular flow area 400 around valve plug 240 can be
determined by the inner peripheral surface 275 of standing valve body 270 and
the
outer peripheral surface 242 of valve plug 240. The circular flow area 410 at
valve
seat 210 is determined by the inner peripheral surface 212 of valve seat 210.
Since
.. the annular flow area 400 around valve plug 240 can be substantially equal
to or
greater than the annular flow area 410 within valve seat 210, the internal
diameter
of valve seat 210 and the external diameter of valve plug 240 can be
determined
for a specified standing valve body 270 inner diameter. The inner diameter of
standing valve body 270 can depend on the yield strength of the selected
material,
and include any appropriate safety factor, which can be established by the
standing valve or pump barrel manufacturers and/or standards known by those
skilled in the art.
The outer annular flow area 420 of hollow valve ring 250 is determined by the
inner
peripheral surface 275 of standing valve body 270 and the outer peripheral
surface
252 of hollow valve ring 250. The inner circular flow area 430 of hollow valve
ring
250 is determined by the inner peripheral surface 254 of hollow valve ring
250. The
sum of the outer annular flow area 420 of hollow valve ring 250 plus the inner
circular flow area 430 of the same hollow valve ring 250 can be substantially
equal
to the annular flow area 400 around valve plug 240. This establishes both the
outer
diameter 255 and inner diameter 253 of hollow valve ring 250, taking into
consideration the overlap that must exist between: (i) the outer diameter 255
of
hollow valve ring 250 and the inner diameter 216 of valve seat 210, such that
when
the valve is closed both contacting surfaces 258 of hollow valve ring 250 and
214
of valve seat 210 make a perfect seal, and (ii) the outer diameter 255 of
valve plug
240 and the inner diameter 253 of hollow valve ring 250, such that when the
valve
is closed both contacting surfaces 244 of valve plug 240 and 256 of hollow
valve
ring 250 also make a seal. The contacting surfaces 258 of hollow valve ring
250
and 214 of valve seat 210, as well as the contacting surfaces 244 of valve
plug
240 and 256 of hollow valve ring 250, correspond to spherical segments,
ensuring
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that any slight angular misalignment between the sealing elements will
maintain a
seal.
The inner circular flow area 430 or Ac of hollow valve ring 250 determines the
minimum separation distance 440 or Hc between the discharge end of hollow
valve
ring 250 and the intake end of valve plug 240. This minimum separation
distance
440 can be determined from the conical surface of revolution 450 that is
generated
between the overlap of sealing surface 256 of hollow valve ring 250 and the
sealing
surface 244 of valve plug 240. The large diameter Db of conical surface of
revolution 450 corresponds to the outer diameter 246 of valve plug 240, while
the
minor diameter Dk of this same conical surface of revolution 450 corresponds
to
the inner diameter 253 of hollow valve ring 250. Once these parameters are
established, the minimum separation distance 440 or Hc can be determined from
Equation 3:
= 4 Ac2 (Db ¨
Dk) 2
Hc = Square Root ( ---------------------------- (Eq. 3)
TC 2 (Db + Dk) 2 4
Thus, the separation distance 440 or Hc calculated in Equation 3 is greater
than
or equal to the minimal distance attained with the above relationship.
The circular flow area 410 or At of valve seat 210 minus the inner circular
flow
zo area 430 or Ac of hollow valve ring 250 determines the minimum separation
distance 460 or Ht between the discharge end of valve seat 210 and the intake
end of hollow valve ring 250. This minimum separation distance 460 can be
determined from the conical surface 470 that is generated between the overlap
of
sealing surface 258 of hollow valve ring 250 and the sealing surface 214 of
valve
seat 210. The large diameter Dp of conical surface of revolution 470
corresponds
to the outer diameter 255 of valve seat 250, while the minor diameter On of
this
same conical surface of revolution 470 corresponds to the inner diameter 216
of
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valve seat 210. Once these parameters are established, the minimum separation
distance 460 or Ht can be determined from Equation 4:
4 (At ¨ Ac) 2 (Dp ¨ Dn) 2
Ht = Square Root ( --------------------------------------- (Eq. 4)
n2 (Dp + Dn) 2 4
Thus, the separation distance 460 or Ht calculated in Equation 4 is greater
than or
equal to the minimal distance attained with the above relationship.
For subsurface pumps assembled according to: (i) Case A, the mechanically
actuated traveling valve 100 can be located at the discharge end of plunger
50;
io while standing valve 200 can be located at the intake end of barrel 60,
and (ii)
Case B, the mechanically actuated traveling valve 100 can be located at the
discharge end of barrel 60; while standing valve 200 can be located at the
discharge end of plunger 50.
For example, having regard to FIG. 5, one embodiment of a positive
displacement
subsurface pump for Case A is shown for both the open and closed position of
the
valves. Having regard to FIG. 6, an embodiment for Case B is shown for both
the
open and closed position of the valves. In both figures, the present
mechanically
actuated traveling valve 100 is shown having only one hollow valve ring and
the
standing valve 200 having only one hollow valve ring. It is understood that
zo additional hollow valve rings can be included, but for explanatory
purposes, only
embodiments having a single hollow valve ring are depicted.
In embodiments herein, the longitudinal axis of each individual component of
mechanically actuated traveling valve 100 and standing valve 200 are collinear
,
and move along the longitudinal axis 500 of the positive displacement
subsurface
pump. When the valves are open, there must be a minimum distance at which
their
respective hollow valve ring separates from their corresponding seat and
another
minimum distance at which their respective plug separates from the other side
of
the hollow valve ring. It is contemplated that any possible configurations and
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embodiments that comply with these concepts are considered, such as those in
which the valve constituents are not collinear with the pump's longitudinal
axis 500
when open or closed.
For both Cases A and B, the discharge end of valve connector 120 can be
affixed
.. to the reciprocating motion inducing element 30, which can either be the
sucker
rod, continuous rod, rod valve (according to Standard API nomenclature) or any
other means capable of imparting reciprocating motion depending on the type of
subsurface pump selected (whether rod, tubing or casing).
All the contacting sealing surfaces between the valve components can be
specifically spherical zones, since this particular shape will maintain a seal
even
for slight angular misalignment between them; however it must be understood,
that
any other shape or configuration that can maintain a seal is also contemplated
herein.
Embodiments of the present travelling valve can enable the reciprocating
portion
of a displacement pump to descend at a faster rate due to the reduction in the
drag
resistance to the motion caused by the increment in flow areas across said
traveling valve. As such, the present valve can be used to handle high
viscosity
crude oil (particularly heavy and extra-heavy crudes), while permitting a
higher
number of strokes per unit time and improving the pump's performance.
Embodiments of the present traveling valve can provide a travelling valve
having
mechanically actuated (guided) sealing elements, reducing oil seepage across
the
valve, and because its operation is unaffected by the vertical component of
the
force of gravity, improving the overall performance of the pump at any
deviation
angle, particularly when used in highly deviated or horizontal wells.
Embodiments of the present traveling valve can operate mechanically and by
pressure differential, thus opening in each stroke regardless of the fluid gas
to oil
ratio, improving the pump's volumetric efficiency.
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In operation, a positive displacement pump for Case A is shown in FIG. 5, and
for
Case B in FIG. 6. In both cases, during the suction stage, mechanically
actuated
traveling valve 100 is closed and standing valve 200 is open; while at the
discharge
stage, mechanically actuated traveling valve 100 is open and standing valve
200
is closed. Accordingly, the present system aims to provide the following
advantages:
1. By equating the flow areas across each of the components of the
mechanically
actuated traveling valve 100 a minimal pressure drop is attained; consequently
the
flow across the valve will maximized compared to single sealing element
valves.
2. By placing the mechanically actuated traveling valve 100 at the discharge
end
of the moveable element, it can be implemented in pumps that have either: (i)
the
plunger 50 as the moveable component, or (ii) the barrel 60 as the moveable
component, permitting the implementation of mechanically opening valves, of
any
sort, in pumps that have the barrel as the moveable component.
3. The contacting surfaces of each of the components of the mechanically
actuated
traveling valve 100 can have a spherical zone configuration, which assures a
substantially perfect seal even when slight angular misalignment appears due
to
wear after lengthy operation.
4. Since traveling valve 100 operates mechanically, the gas that separates
from
the crude oil can be displaced in each stroke by the fluid that is downstream
of the
valve, thus avoiding gas or steam lock.
5. For the case when the plunger 50 is the moveable component, since the
mechanically actuated traveling valve 100 is located at the discharge end of
said
plunger 50, the suction end of this plunger 50 will contact the fluid before
the
mechanically actuated traveling valve 100 does, thus allowing for the
viscosity of
the fluid to generate a drag force which aids in the earlier opening of the
said
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traveling valve. Prior art did not have this advantage, since the traveling
valve was
specifically located outside the plunger at its suction end.
6.- A positive displacement subsurface pump assembled with the mechanically
actuated traveling valve 100 according to embodiments herein, together with
any
other standing valve, can operate more efficiently; however, when used with a
standing valve 200, a maximum efficiency pump can be generated, since now both
valves allow for minimal pressure drop and maximum fluid flow across the pump
in each pump stroke, enabling an increase in the pumping rate, consequently
incrementing the oil production.
It is to be understood that the invention is not limited to the illustrations
described
and shown herein, which are deemed to be merely illustrative of the best modes
of carrying out the invention, and which are susceptible of modification of
form,
size, arrangement of parts and details of operation. The invention rather is
intended to encompass all such modifications which are within its spirit and
scope
as defined by the claims.
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