Note: Descriptions are shown in the official language in which they were submitted.
IS18.0422-CA-NP
FRACTURING SYSTEMS AND METHODS WITH RAMS
BACKGROUND
[0001] This section is intended to introduce the reader to various
aspects of art
that may be related to various aspects of the presently described embodiments.
This
discussion is believed to be helpful in providing the reader with background
information to facilitate a better understanding of the various aspects of the
present
embodiments. Accordingly, it should be understood that these statements are to
be
read in this light, and not as admissions of prior art.
[0002] In order to meet consumer and industrial demand for natural
resources,
companies often invest significant amounts of time and money in searching for
and
extracting oil, natural gas, and other subterranean resources from the earth.
Particularly, once a desired subterranean resource is discovered, drilling and
production systems are often employed to access and extract the resource.
These
systems may be located onshore or offshore depending on the location of a
desired
resource. Further, such systems generally include a wellhead assembly through
which
the resource is extracted. These wellhead assemblies may include a wide
variety of
components, such as various casings, valves, fluid conduits, and the like,
that control
drilling or extraction operations.
[0003] Additionally, such wellhead assemblies may use a fracturing tree
and
other components to facilitate a fracturing process and enhance production
from a
well. As will be appreciated, resources such as oil and natural gas are
generally
extracted from fissures or other cavities formed in various subterranean rock
formations or strata. To facilitate extraction of such resources, a well may
be
subjected to a fracturing process that creates one or more man-made fractures
in a
rock formation. This facilitates, for example, coupling of pre-existing
fissures and
cavities, allowing oil, gas, or the like to flow into the wellbore. Such
fracturing
processes typically include injecting a fracturing fluid¨which is often a
mixture
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including sand and water¨ into the well to increase the well's pressure and
form the
man-made fractures. The high pressure of the fluid increases crack size and
crack
propagation through the rock formation to release oil and gas, while the
proppant
prevents the cracks from closing once the fluid is depressurized. During
fracturing
operations, fracturing fluid may be routed via fracturing lines (e.g., pipes)
to
fracturing trees installed at wellheads. Conventional fracturing trees have
valves that
can be opened and closed to control flow of fluid through the fracturing trees
into
the wells. Unfortunately, proppant may interfere with the operation of valves
that
control pressure in the well during fracturing operations.
SUMMARY
[0004] Certain aspects of some embodiments disclosed herein are set
forth
below. It should be understood that these aspects are presented merely to
provide
the reader with a brief summary of certain forms the invention might take and
that
these aspects are not intended to limit the scope of the invention. Indeed,
the
invention may encompass a variety of aspects that may not be set forth below.
[0005] At least some embodiments of the present disclosure generally
relate to
fracturing systems using rams to control fluid flow through a fracturing tree
during
fracturing operations. In some embodiments, the fracturing tree includes a
frac stack
body having ram cavities provided along a bore. Rams in the ram cavities can
be
opened and closed to control fracturing fluid and pressure in the fracturing
tree.
[0006] In one embodiment, a fracturing system that includes a wellhead
and a
frac stack coupled to the wellhead. The frac stack includes a flow control
device
having a housing defining a bore that receives a fracturing fluid. The flow
control
device also includes a single ram that opens and closes the bore and forms a
seal
with the housing around the bore without seats.
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[0007] Various refinements of the features noted above may exist in
relation to
various aspects of the present embodiments. Further features may also be
incorporated in these various aspects as well. These refinements and
additional
features may exist individually or in any combination. For instance, various
features
discussed below in relation to one or more of the illustrated embodiments may
be
incorporated into any of the above-described aspects of the present disclosure
alone
or in any combination. Again, the brief summary presented above is intended
only
to familiarize the reader with certain aspects and contexts of some
embodiments
without limitation to the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] These and other features, aspects, and advantages of certain
embodiments will become better understood when the following detailed
description
is read with reference to the accompanying drawings in which like characters
represent like parts throughout the drawings, wherein:
[0009] FIG. 1 generally depicts a fracturing system having a fracturing
tree in
accordance with an embodiment of the present disclosure;
[0010] FIG. 2 is a block diagram of the fracturing system of FIG. 1 with
a
fracturing manifold coupled to multiple fracturing trees in accordance with
one
embodiment;
[0011] FIG. 3 is a block diagram showing components of the fracturing
tree of
FIG. 1, including a frac stack having rams for controlling flow through the
fracturing
tree, in accordance with one embodiment;
[0012] FIG. 4 is a schematic depicting the frac stack of FIG. 3 as
having rams
disposed in a body of the frac stack in accordance with one embodiment;
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[0013] FIGS. 5 and 6 depict examples of rams that can be used in a
fracturing
tree, such as within the frac stack body of FIG. 4, in accordance with some
embodiments;
[0014] FIGS. 7 and 8 schematically depict closing of rams within the
frac stack
body of FIG. 4 in accordance with some embodiments;
[0015] FIGS. 9 and 10 generally depict protective sleeves disposed in
frac stack
bodies to shield rams from erosive flow in accordance with some embodiments;
[0016] FIGS. 11-13 depict a protective sleeve that can be rotated to
selectively
shield rams in a frac stack body in accordance with one embodiment;
[0017] FIGS. 14-16 depict a protective sleeve that can be moved axially
within a
bore of a frac stack body to selectively uncover a pair of rams to facilitate
flow
control within the frac stack body in accordance with one embodiment;
[0018] FIGS. 17-26 depict sealing configurations of rams that can be
used in a
fracturing tree in accordance with certain embodiments;
[0019] FIG. 27 depicts a portion of a ram packer or other seal having a
wire
mesh for reducing erosive wear of a body of the ram packer or other seal in
accordance with one embodiment;
[0020] FIG. 28 depicts rams with wipers for pushing sand out of ram
cavities
and into a bore of a frac stack body in accordance with one embodiment;
[0021] FIG. 29 depicts a frac stack having flow control devices with
sealing rams
in accordance with one embodiment;
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[0022] FIG. 30 is a cross-sectional view of one of the flow control
devices of
FIG. 29 in an open position in accordance with an embodiment of the present
disclosure;
[0023] FIG. 31 is a cross-sectional view of the flow control device of
FIG. 30 in
a closed position in accordance with an embodiment of the present disclosure;
[0024] FIG. 32 is a detail view of the flow control device of FIGS. 30
and 31 in
accordance with an embodiment of the present disclosure;
[0025] FIG. 33 is a cross-sectional view of a flow control device like
that of
FIG. 30 but in which the flow control device housing includes a seal for
sealing
against a closed ram of the flow control device in accordance with an
embodiment
of the present disclosure;
[0026] FIG. 34 is a cross-sectional view of the flow control device in
FIG. 32 in
accordance with an embodiment of the present disclosure;
[0027] FIG. 35 is a perspective view of a ram of the flow control device
of
FIG. 32 in accordance with an embodiment of the present disclosure;
[0028] FIG. 36 is a cross-sectional view of a flow control device in a
closed
position in accordance with an embodiment of the present disclosure;
[0029] FIG. 37 is a cross-sectional view of a flow control device in
accordance
with an embodiment of the present disclosure;
[0030] FIG. 38 depicts a frac stack having flow control devices with
sealing rams
in accordance with one embodiment;
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[0031] FIG. 39 is a cross-sectional view of one of the flow control
devices of
FIG. 38 in an open position in accordance with an embodiment of the present
disclosure;
[0032] FIG. 40 is a cross-sectional view of the flow control device of
FIG. 39 in
a closed position in accordance with an embodiment of the present disclosure;
[0033] FIG. 41 is a perspective view of wedge rams of the flow control
device
of FIG. 38 in accordance with an embodiment of the present disclosure;
[0034] FIG. 42 is a perspective view of a wedge seal in accordance with
an
embodiment of the present disclosure;
[0035] FIG. 43 is a cross-sectional view of a ram in accordance with an
embodiment of the present disclosure; and
[0036] FIG. 44 is a cross-sectional view of a flow control device in an
open
position in accordance with an embodiment of the present disclosure.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0037] Specific embodiments of the present disclosure are described
below. In
an effort to provide a concise description of these embodiments, all features
of an
actual implementation may not be described in the specification. It should be
appreciated that in the development of any such actual implementation, as in
any
engineering or design project, numerous implementation-specific decisions must
be
made to achieve the developers' specific goals, such as compliance with system-
related and business-related constraints, which may vary from one
implementation to
another. Moreover, it should be appreciated that such a development effort
might be
complex and time-consuming, but would nevertheless be a routine undertaking of
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design, fabrication, and manufacture for those of ordinary skill having the
benefit of
this disclosure.
[0038] When introducing elements of various embodiments, the articles
"a,"
"an," "the," and "said" are intended to mean that there are one or more of the
elements. The terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than the listed
elements. Moreover, any use of "top," "bottom," "above," "below," other
directional
terms, and variations of these terms is made for convenience, but does not
require
any particular orientation of the components.
[0039] Turning now to the present figures, examples of a fracturing
system 10
are provided in FIGS. 1 and 2 in accordance with certain embodiments. The
fracturing system 10 facilitates extraction of natural resources, such as oil
or natural
gas, from a subterranean formation via one or more wells 12 and wellheads 14.
Particularly, by injecting a fracturing fluid into a well 12, the fracturing
system 10
increases the number or size of fractures in a rock formation or strata to
enhance
recovery of natural resources present in the formation. Wells 12 are surface
wells in
some embodiments, but it will be appreciated that resources may be extracted
from
other wells 12, such as platform or subsea wells.
[0040] The fracturing system 10 includes various components to control
flow of
a fracturing fluid into the well 12. For instance, the fracturing system 10
depicted in
FIG. 1 includes a fracturing tree 16 that receives fracturing fluid from a
fluid
supply 18. In some embodiments, the fracturing fluid supply 18 is provided by
trucks
that pump the fluid to fracturing trees 16, but any suitable sources of
fracturing fluid
and manners for transmitting such fluid to the fracturing trees 16 may be
used.
Moreover, the fluid supply 18 may be connected to a fracturing tree 16
directly or via
a fracturing manifold 22, as generally depicted in FIG. 2. The fracturing
manifold 22
can include conduits, such as pipes, as well as valves or sealing rams to
control flow
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of fracturing fluid to the fracturing trees 16 (or from the fracturing trees
16, such as
during a flowback operation). As depicted in FIG. 2, the fracturing manifold
22 is
connected to provide fracturing fluid to multiple fracturing trees 16, which
may then
be routed into respective wells 12 via wellheads 14. But it is noted that the
fracturing
manifold 22 may instead be coupled to a single fracturing tree 16.
[0041] Fracturing trees have traditionally included valves (e.g., gate
valves) that
control flow of fracturing fluid to and from wells through the trees. In at
least some
embodiments of the present disclosure, however, the fracturing trees 16 use
sealing
rams instead of valves to control flow through the trees. One example of such
a
fracturing tree 16 is depicted in FIG. 3 as including a goat head 26, wing
valves 28
and 30, and a fracturing stack ("frac stack") 32. The goat head 26 includes
one or
more connections for coupling the fracturing tree 16 in fluid communication
with
fluid supply 18, such as via fracturing manifold 22. This allows fracturing
fluid from
the fluid supply 18 to enter the fracturing tree 16 through the goat head 26
and then
flow into the frac stack 32. When included, the wing valves 28 and 30 can take
any
of various forms. In one embodiment, for example, the wing valves 28 include
pumpdown valves for controlling flow of a pumpdown fluid into the frac stack
32
and the wing valves 30 include valves for controlling flowback fluid exiting
the
well 12 through the wellhead 14 and the frac stack 32. In some other
embodiments,
either the wing valves 28 or the wing valves 30 could be omitted and the
remaining
wing valves (or even a single remaining wing valve) 28 or 30 could be used at
different times for controlling flow of both pumpdown fluid and flowback
fluid.
[0042] The frac stack 32 includes rams 34 that can be used to control
flow of
the fracturing fluid through the fracturing tree 16 (e.g., into a wellhead 14
and
well 12). The frac stack 32 also includes actuators 36 for controlling opening
and
closing of the rams 34. One example of a frac stack 32 is depicted in FIG. 4
as
having a hollow main body 40 with a bore 42 for conveying fluid through the
body 40. The frac stack main body 40 also includes flanges 44 and 46 to
facilitate
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connection of the body 40 to other components. For example, the main body 40
can
be mounted on a wellhead 14 with the lower flange 44 and connected to the goat
head 26 with the upper flange 46. The main body 40 can be fastened directly to
the
wellhead 14 and the goat head 26 in some embodiments, though in others the
body 40 can be coupled to the wellhead 14 or the goat head 26 via an
intermediate
component, such as an adapter spool or a blowout preventer that is installed
between
the fracturing tree 16 and the wellhead 14.
[0043] In at least some embodiments, flow of fracturing fluid through
the
fracturing tree 16 and into the well 12 is controlled with rams 34 of the
fracturing
tree 16, and the fracturing tree 16 does not include a valve for controlling
flow of
fracturing fluid pumped through the fracturing tree 16 into the well 12.
Further, in at
least one such embodiment, the fracturing system 10 also does not include a
valve
between the fracturing tree 16 and the well 12 for controlling flow of
fracturing fluid
pumped into the well 12 through the fracturing tree 16.
[0044] The frac stack body 40 is depicted in FIG. 4 as having three
pairs of
opposing ram cavities¨namely, ram cavities 52, 54, and 56¨with installed rams
34
that are controlled by actuators 36. In other instances, however, the frac
stack
body 40 can have a different number of ram cavities. Rams are installed in the
frac
stack body 40 with keyed engagement in some embodiments to maintain desired
orientation of the rams. For example, the rams may include keys that fit
within slots
along the ram cavities, or the ram cavities may include keys that fit within
slots in the
rams.
[0045] The frac stack main body 40 is also shown in FIG. 4 as including
conduits 62 for routing fluid between the bore 42 and other components
external to
the body, such as the wing valves 28 and 30, which can be coupled to the body
40 in-
line with the conduits 62. The body 40 can include valve flats or any other
suitable
features to facilitate attachment of the wing valves to the body. In some
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embodiments, a pumpdown fluid can be pumped into the bore 42 and then into a
well 12 through one of the conduits 62 and flowback fluid from the well 12 can
flow
into the bore 42 and out of the frac stack body 40 through the other conduit
62. In
another embodiment, pumpdown fluid can be pumped into the bore 42 and the
flowback fluid can flow out of the bore 42 at different times through the same
conduit 62. Flow through that conduit 62 may be controlled with one or more
valves, such as a wing valve 28 or 30. In such cases, the body 40 may include
just a
single conduit 62, but other embodiments can include a different number of
conduits 62. Further, conduits 62 can be provided at different axial positions
along
the body 40 in some instances. For example, one conduit 62 can be provided
through
the body 40 between ram cavities 52 and 54 (as depicted in FIG. 4), while
another
conduit 62 could be provided through the body 40 between the ram cavities 54
and 56. This would allow the rams in ram cavities 54 to selectively isolate
the
conduits 62 from one another to provide further control of flow through the
body 40.
[0046] The frac stack 32 can include any suitable rams 34 and actuators
36. For
example, the rams 34 can include blind rams, pipe rams, gate-style rams, or
shear
rams, and the actuators 36 could be electric, hydraulic, or electro-hydraulic
actuators.
Two examples of rams 34 that can be used in the frac stack body 40 are
depicted in
FIGS. 5 and 6. More particularly, the rams 34 are depicted as pipe rams in
FIG. 5,
with each ram 34 including a body or ram block 66, a ram seal 68 (here shown
as a
top seal), and a ram packer 70. The ram seal 68 and the ram packer 70 include
elastomeric materials that facilitate sealing by the ram 34 in the frac stack
main
body 40. The ram packer 70 includes alignment pins 72 that are received in
corresponding slots of the ram block 66 when the ram packer 70 is installed.
The
ram packers 70 include sealing surfaces 74 and recesses 78 that allow a pair
of
opposing pipe rams 34 to close about and seal against a tubular member, such
as a
pipe. The recesses 78 may be sized according to the diameter of the pipe about
which the packers 70 are intended to seal. Additionally, in other embodiments,
the
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rams 34 could be provided as variable-bore pipe rams used to seal around pipes
within a range of diameters. Each ram 34 is also shown as including a slot 76
for
receiving a portion (e.g., a button) of a connecting rod controlled by an
actuator 36
for moving the ram 34 into and out of the bore 42 of the frac stack body 40.
[0047] Rams 34 in the frac stack body 40 may also or instead be provided
as
blind rams, such as those depicted in FIG. 6. In this example, the blind rams
34
include ram blocks 66, top seals 68, and ram packers 70. Unlike the packers 70
of the
pipe rams in FIG. 5, however, the packers 70 in FIG. 6 do not include recesses
78 for
receiving a pipe. Consequently, when installed in a frac stack body 40, the
pair of
blind rams 34 may close against one another along sealing surfaces 74 to seal
the
bore 42 and prevent flow through the frac stack 32. The ram packers 70 of FIG.
6
include alignment pins 72 similar or identical to those of FIG. 5. And like
the pipe
rams of FIG. 5, the blind rams shown in FIG. 6 include slots 76 for receiving
connecting rods to enable control of the rams by actuators 36. Although the
rams 34
depicted in FIGS. 5 and 6 are oval rams, in other instances the rams 34 could
be
round rams having a circular cross-section. Further, opposing rams 34 in the
body 40
could instead be provided in other forms, such as gate-style rams that slide
over one
another or shear rams.
[0048] The actuators 36 can be hydraulic actuators with operating
cylinders that
are coupled to the frac stack body 40 and include operating pistons that
control the
position of the rams via connecting rods. In some other embodiments, the
actuators 36 are electric actuators, which may include electric motors that
control a
drive stem for moving the rams. The actuators 36 can be attached to the frac
stack
body 40 in any suitable manner, such as with bonnets fastened to the frac
stack
body 40 with bolts, hydraulic tensioners, or clamps.
[0049] As noted above, the rams 34 can be used to control flow through
the frac
stack body 40. As generally shown in FIG. 7, for example, each of the ram
cavity
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pairs 52, 54, and 56 includes a pair of opposing rams 34 (e.g., blind rams)
that are
closed to seal against one another and prevent flow through the bore 42. The
rams 34 in the cavities 52, 54, and 56 may be selectively retracted (i.e.,
opened) to
allow fluid to flow through the bore 42. For instance, all of the rams 34 in
FIG. 7
can be retracted to allow fracturing fluid to flow through the bore 42 from
the upper
end of the frac stack body 40 (such as from the goat head 26) to the lower end
of
the body 40, from which the fracturing fluid may flow into the wellhead 14 and
then
down into the well 12.
[0050] In other cases, some of the rams 34 in the frac stack body 40 are
opened
while other rams 34 in the body 40 remain closed. For example, the rams 34 in
the
ram cavities 52 may be closed while the rams 34 in the ram cavities 54 and 56
are
open, as generally illustrated in FIG. 8. This allows fluid to pass between
the
conduits 62 and a lower portion of the bore 42, while the rams 34 of the ram
cavities 52 isolate the lower portion of the bore 42 from an upper portion of
the
bore. In this arrangement, pumpdown fluid may be pumped through a conduit 62
into the bore 42 and then down into a well 12 while preventing flow of the
pumpdown fluid out of the upper end of the frac stack 32. Similarly, flowback
fluid
coming up through the well 12 can be routed out of the frac stack body 40
through a
conduit 62, with the closed rams 34 of the ram cavities 52 preventing flowback
fluid
from flowing out of the upper end of the frac stack 32.
[0051] Fracturing fluid typically contains sand or other abrasive
particulates that
can erode components exposed to the fluid. In some embodiments, a protective
sleeve is provided within the frac stack body 40 to isolate the rams 34 and
their seals
from erosive flow. One example of this is depicted in FIG. 9, which shows a
protective sleeve 82 positioned in the bore 42 of the frac stack body 40. As
shown,
the protective sleeve 82 is landed on an internal shoulder within the frac
stack
body 40 and has an inner diameter equal to that of the bore 42 below the
protective
sleeve 82 at the internal shoulder. Seals 84 act as pressure barriers between
the
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protective sleeve 82 and the wall of the bore 42 to prevent fracturing fluid
from
flowing along the outside of the sleeve 82 to the rams 34.
[0052] In some embodiments, the protective sleeve 82 is installed in the
frac
stack body 40 with an adapter component. In FIG. 9, for example, the
protective
sleeve 82 is connected via a threaded interface 88 to an adapter spool 86,
which is
fastened to the upper flange 46 of the frac stack body 40. But in other
embodiments,
the protective sleeve 82 is installed in the bore 42 without an adapter. One
such
embodiment is depicted in FIG. 10, in which the protective sleeve 82 is
threaded
instead to the upper end of the frac stack body 40. Although the top of the
protective sleeve 82 is shown protruding from the frac stack body 40, the
entire
sleeve 82 could be received within the body 40 in other instances.
[0053] The protective sleeve 82 can be moved within the bore 42 of the
frac
stack body 40 to selectively cover ram cavities and protect installed rams 34.
By way
of example, a protective sleeve 82 with apertures 92 is depicted in FIGS. 11-
13.
With the sleeve 82 positioned as shown in FIG. 11, the apertures 92 are
circumferentially offset from the ram cavities 56 and the side walls of the
sleeve 82
shield rams 34 in the cavities 56 from erosive flow (e.g., of fracturing
fluid) through
the sleeve 82. Flow through the sleeve 82 (and, thus, the frac stack body 40)
can be
prevented by rotating the sleeve 82 to align the apertures 92 with the ram
cavities 56
and then closing the rams 34 together through the apertures 92 to seal the
bore, as
generally shown in FIGS. 12 and 13. The rams 34 can later be opened and
withdrawn out of the apertures 92 to allow flow, and the sleeve 82 can be
rotated to
again cover the ram cavities 56. In other embodiments, the protective sleeve
82 can
be raised or lowered within the bore 42 to move the apertures 92 axially to
selectively
cover the ram cavities 56. Although ram cavities 56 are depicted in FIGS. 11-
13, it
will be appreciated that these same techniques and others described below
could also
or instead be used with other ram cavities, such as ram cavities 52 or 54.
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[0054] Another example of a frac stack 32 having a protective sleeve is
generally
depicted in FIGS. 14-16. In this embodiment, the protective sleeve 102 is
disposed
within the bore 42 to cover ram cavities 104, 106, and 108 and shield
installed
rams 110, 112, and 114 from erosive flow. The assembly includes seals 116
between
the exterior of the sleeve 102 and the frac stack body 40. The seals 116
include lip
seals in some embodiments, but the seals 116 (and the seals 84 above) can be
provided in any suitable form. Because of the seals and the shape of the
protective
sleeve 102, pressurized fluid within the bore 42 applies a differential
pressure on the
sleeve 102 and biases the sleeve down into the position depicted in FIG. 14.
[0055] The protective sleeve 102 is shown in FIG. 14 as covering each of
the
ram cavities 104, 106, and 108. Although other rams may instead be used in the
ram
cavities, in at least some embodiments the rams 110 are shear rams, the rams
112 are
pipe rams, and the rams 114 are blind rams. The protective sleeve 102 can be
axially
displaced to uncover the ram cavities 108 and allow the rams 114 to close and
seal
the bore 42.
[0056] In at least some embodiments, the protective sleeve 102 is
hydraulically
actuated. For example, as shown in FIGS. 14-16, the upper end of the
protective
sleeve 102 operates as a piston head to facilitate hydraulic actuation of the
sleeve 102. More particularly, the sleeve 102 can be raised by routing fluid
(such as
with a pump 120) through conduit 122 into the bore 42 to lift the sleeve 102.
In at
least one embodiment, fluid within the bore 42 is used as the control fluid
for
actuating the protective sleeve 102. Fracturing fluid within the bore 42 can
be
diverted out from the bore 42 through conduit 124 and then be pumped with
pump 120 or otherwise routed back into the bore through the conduit 122 to
raise
the protective sleeve 102, for instance. In at least some cases, the pipe rams
112 are
closed to seal about the exterior of the sleeve 102 (as shown in FIG. 15) and
fluid is
then routed through the conduit 122 into the bore 42¨more specifically, into
an
enclosed volume that is outside the sleeve 102 and partially bound by the pipe
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rams 112¨to lift the sleeve 102 and expose ram cavities 108 (as shown in FIG.
16).
The protective sleeve 102 can be lifted in different ways in other
embodiments, such
as with an electric motor or with an external hydraulic sleeve or cylinder.
Once the
sleeve 102 is lifted, the blind rams 114 may be closed to seal the bore 42 and
prevent
flow through the bore 42 of frac stack body 40. In an emergency, such as in
the case
of excessive flowback, shear rams 110 can be closed to shear the protective
sleeve 102 and close the bore 42.
[0057] The rams of the frac stack 32 can be designed with features to
reduce
erosive wear on sealing elements and increase service life. One example is
generally
depicted in FIGS. 17 and 18, which show rams 34 disposed in opposing ram
cavities 128 of a frac stack body 40. These rams 34 include top seals 68 and
side
packers 130 that seal against the frac stack body 40. But rather than having
packers
that extend across opposing front faces of the rams and seal against one
another
along those front faces when the rams are closed, the depicted rams 34 include
a
protruding ridge or nose 132 that is received in a slot 134 when the rams 34
are
closed (FIG. 18).
[0058] Seals 136 and 140 (which may also be referred to as nose packers)
within
the slot 134 seal against the nose 132. When the rams 34 are closed, the seals
136
and 140 cooperate with the top seals 68 and the side packers 130 to prevent
flow
through the bore 42. Because the surfaces of the seals 136 and 140 that
contact the
nose 132 are positioned within the slot 134 transverse to the flow direction
through
the bore 42, erosive wear on these surfaces may be lower than in the case of
front-
facing packers (e.g., packers 70) exposed to abrasive flow generally parallel
to their
sealing faces. Although upper and lower nose packers 136 and 140 are depicted
in
FIGS. 17 and 18, either of these could be omitted and a single nose packer
could be
used in other embodiments. In at least some instances, plates 138 can be
positioned
along the front face of the ram 34 that has the nose packers 136 and 140 to
retain or
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protect the packers 136 and 140. The plates 138 can be fastened to the ram
block or
attached in any other suitable manner.
[0059] In another embodiment generally depicted in FIGS. 19 and 20,
protective
doors or blades 144 protect the nose packers 136 and 140. These blades 144 are
displaced by the nose 132 during closing of the rams 34 against one another,
with
the nose packers 136 and 140 sealing against the nose 132 within the slot 134,
as
described above. As also shown in FIGS. 19 and 20, the ram 34 having the slot
134
can also include a weep hole 146 to allow fluid within the slot 134 to drain
from the
slot when displaced by the nose 132 during closing of the rams.
[0060] In FIGS. 17-20 above, the nose packers 136 and 140 are shown
recessed
from the front face of the ram. That is, the nose packers 136 and 140 in those
figures are not provided at the leading edges of the rams 34. In other
embodiments,
the plates 138 and blades 144 are omitted and the nose packers 136 and 140 are
positioned along the front face of the ram, such as depicted in FIGS. 21 and
22. In
this example, the nose packers 136 and 140 press against one another when the
rams 34 are open (FIG. 21), which may reduce abrasive wear on the surfaces of
the
nose packers 136 and 140 that seal against the nose 132 when the rams 34 are
closed (FIG. 22).
[0061] In yet another embodiment shown generally in FIGS. 23 and 24, the
rams 34 include levers 148 (e.g., metal levers) that are positioned in front
of seals 150
in slots 134 to protect those seals during fracturing. As depicted, the levers
148
contact each other and rotate about pins 152 when the rams close against one
another. The rotating levers 148 push the seals 150 into sealing engagement
with
each other to close the bore and prevent flow.
[0062] In a still further embodiment shown generally in FIGS. 25 and 26,
the
rams 34 include seals 150 in slots 134, along with metal plates 156, 158, and
160.
These metal plates 156, 158, and 160 protect the seals 150 during fracturing
and
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drive the seals 150 toward each other upon closing the rams 34. More
specifically, as
the rams 34 close, the metal plates 156 of the two rams engage one another and
are
pushed back into their respective slots 134 as the rams continue to close.
This is
followed by the metal plates 158 engaging one another and being pushed back
into
their slots 134, and then the metal plates 160 engaging one other and being
pushed
back into the slots 134, as the rams close. As the plates 156, 158, and 160
move back
into the slots 134, they displace the seals 150 and drive the seals into
sealing
engagement with one another. While the plates 156, 158, and 160 are positioned
in
FIGS. 25 and 26 to generally drive the seals 150 below the plates, this could
be
reversed and the plates could drive the seals 150 above the plates (e.g., by
flipping the
rams 34). The metal plates 156, 158, and 160 can be connected within the ram
34 in
any suitable manner. For example, the plates can be received in slots in the
ram
blocks or adhered to the seals 150. In certain embodiments, the plates 156,
158,
and 160 are connected together, such as with mating pins and slots that allow
the
plates to slide relative to one another.
[0063] The packers and other seals described above can be formed of any
suitable materials, and in at least some embodiments include elastomer. Some
ram
packers or seals can include a wire mesh to reduce erosive wear. For example,
as
depicted in FIG. 27, a ram packer 70 (or some other ram seal) includes a wire
mesh 166 on an elastomer body 168. In some embodiments, the wire mesh 166 is
partially embedded in the elastomer body 168, such as in a sealing face of the
packer 70. The wire mesh 166 may reduce wear of the elastomer body 168 when
placed in erosive service, such as within the frac stack body 40.
[0064] Still further, in at least some embodiments the frac stack 32
includes
features to reduce collection of sand or other particulates from the
fracturing fluid
within the frac stack body 40. By way of example, rams 34 in the frac stack
body 40
can include blades or rubber wiper seals 172, as generally depicted in FIG.
28. As the
rams 34 close, the blades or wiper seals 172 displace sand or other
particulates that
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have settled on surfaces of the ram cavities 128. And in at least some
embodiments,
seals (e.g., lip seals) can be provided about the exterior of the rams 34 to
seal against
the surfaces of the ram cavities 128 and prevent fracturing fluid from flowing
past
the rams 34 from the bore 42 and depositing sand (or other particulates)
behind the
rams 34.
[0065] Another example of a frac stack 32 having sealing rams 34 is
shown in
FIG. 29. In this depicted embodiment, the body of the frac stack 32 includes
stacked
flow control devices 232 with sealing rams 34 that can be opened and closed
with
actuators 36 (e.g., electric actuators, pneumatic actuators, hydraulic
actuators, manual
actuators, or a combination thereof). More specifically, the flow control
devices 232
of FIG. 29 each include a single ram 34 that can be used to control flow of
fracturing or other fluid through the frac stack 32. Although just a portion
of the
frac stack 32 is shown in FIG. 29, it will be appreciated that various
additional
components (e.g., goat head 26 and wing valves 28 and 30) can be used to
control or
otherwise facilitate flow through the frac stack 32, such as described above.
The flow
control devices 232 of the frac stack body can be connected to one another and
to
other equipment in any suitable manner. Further, while two flow control
devices 232
are shown in FIG. 29, it will be appreciated that the frac stack 32 may
include some
other number of flow control devices 232, such as between three and six flow
control devices 232 or just a single flow control device 232. The flow control
devices 232 may be used for large bore (e.g., seven-inch) and high pressure
(e.g.,
15,000 psi) applications. In some embodiments, the flow control devices 232
are
used in place of lower and upper master gate valves in a fracturing tree. The
flow
control device 232 could be used apart from the frac stack in other fracturing
operations or could be used in other (i.e., non-fracturing) flow control
contexts in
other embodiments.
[0066] FIG. 30 is a cross-sectional view of one of the flow control
devices 232
of FIG. 29 in an open position. The flow control device 232 includes a housing
238
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with a bore 240 for conveying fluid through the housing 238. In operation, the
flow
of fracturing fluid through the bore 240 is controlled with the ram 34. As
explained
above, fracturing fluid includes proppant (e.g., sand) that props open cracks
formed
under pressure so that hydrocarbons can flow out of a formation. The ram 34
rests
within a cavity 242 of the housing 238 and moves axially in axial directions
244
and 246 (FIG. 31) to open and close the bore 240. In an open position, the ram
34 is
out of the bore 240 enabling fracturing fluid to flow through the housing 238
and
into the well 12. By retracting the ram 34 out of the bore 240, the ram 34 is
not
exposed to the direct flow path through the housing 238, which may reduce
erosion
and wear on the ram 34.
[0067] The axial position of the ram 34 is controlled with the actuator
36. As
explained above, the actuator 36 may be an electric actuator, pneumatic
actuator,
hydraulic actuator, manual actuator, or a combination thereof. The actuator 36
couples to the ram 34 with a shaft 248 that extends into the cavity 242. As
will be
explained below, the flow control device 232 includes a seal system 250 that
enables
ram 34 to form a seal with the housing 238, around the bore 240, without valve
seats.
[0068] FIG. 31 is a cross-sectional view of the flow control device 232
in a
closed position. The ram 34 includes a body 270 that supports the seal system
250.
The body 270 includes a front face 272, a rear face 274, an upper surface 276,
and a
lower surface 278. In the closed position, the front face 272 rests within a
recess 280
defined by the housing 238. The combination of the recess 280 and the cavity
242
enable the housing 238 to support the ram 34 under pressure within the bore
240. In
order to form a seal within the housing 238, the ram 34 includes the seal
system 250.
The seal system 250 includes a front seal 282 and an upper seal 284. The front
seal 282 is an elastomeric seal (e.g., nitrile, hydrogenated nitrile) that
rests within a
slot 286 of the front face 272 and is configured to form a seal with a surface
288 that
defines the recess 280 (i.e., recess surface).
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[0069] The upper seal 284 is also an elastomeric seal (e.g., nitrile,
hydrogenated
nitrile) and likewise forms a seal with the housing 238. As illustrated, the
upper
seal 284 engages and seals against a surface 290 (i.e., cavity surface) that
defines the
cavity 242. In order to retain the upper seal 284, the body 270 defines an
upper seal
groove 292 that receives the upper seal 284. By including elastomeric seals in
the seal
system 250, the flow control device 232 is able to form seals that block the
flow of
fracturing fluid through the bore 240 without using valve seats. More
specifically, the
elastomeric seals in the flow control device 232 may facilitate sealing in an
erosive
hydraulic fracturing environment because the elastomeric seals may be less
susceptible to pitted surfaces. Accordingly, instead of forming a metal-to-
metal seal
between a ram and valve seats, the elastomeric seals of the flow control
device 232
enable the ram 34 to seal with the housing 238.
[0070] FIG. 32 is a detail view of the flow control device 232 of FIGS.
30
and 31. In some embodiments, the seal system 250 may include energizing plates
320
and 322. These energizing plates 320 and 322 may be made out of metal or
another
material that is more rigid than the elastomeric material of the front seal
282. The
energizing plates 320 and 322 rest within the slot 286 and are placed on
opposite
sides of the front seal 282. The body 270 retains the energizing plates 320
and 322
with respective ledges/protrusions 324 and 326 that engage notches 328 and 330
on
the respective energizing plates 320, 322. As illustrated above in FIG. 30,
the
energizing plates 320 and 322 are configured to extend beyond the front face
272.
For example, the energizing plates 320 and 322 may extend between 1 mm and 20
mm beyond the front face 272. As the ram 34 moves in axial direction 244, the
energizing plates 320 and 322 contact the surface 288, which blocks further
axial
movement of the plates 320 and 322 in axial direction 244. As the ram 34
continues
to move in axial direction 244, the energizing plates 320 and 322 are driven
in axial
direction 246 (relative to the moving ram 34). As the energizing plates 320
and 322
move in axial direction 246, they engage ledges 332 and 334 on the elastomeric
front
seal 282. The force of the energizing plates 320 and 322 on the elastomeric
front
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seal 282 flows through the elastomeric front seal 282 and drives the
elastomeric front
seal 282 in axial direction 244. In other words, the force of the energizing
plates 320
and 322 energizes the elastomeric front seal 282 in axial direction 244
increasing the
sealing force of the elastomeric front seal 282 against the housing 238. The
energizing plates 320 and 322 may also limit or prevent extrusion of the
elastomeric
front seal 282 (e.g., into a gap between the front face 272 of the body 270
and the
surface 288 of the recess 280) when closing the ram 34.
[0071] In some embodiments, the seal system 250 may not include
energizing
plates 320 and 322. Instead, a portion of the front seal 282 may extend beyond
the
front face 272, while the front seal 282 is retained within the slot 286
through
contact between the ledges 332 and 334, and the ledges/protrusions 324 and
326.
[0072] Further, in some instances the housing 238 of the flow control
device 232 may include a seal in the recess 280 opposite the ram 34. One
example of
such a flow control device 232 is shown in FIG. 33. In this depicted
embodiment,
the housing 238 of the flow control device 232 includes a seal 350 (e.g., an
elastomer
seal) in the recess 280 across the bore 240 from the ram 34. This opposing
seal 350 is
positioned to seal against the front seal 282 when the ram 34 is moved to the
closed
position. The seal 350 can be retained in the recess 280 with mounting plates
352 or
in any other suitable manner. In another embodiment, the seal 350 can include
projecting arms (e.g., a U-shaped packer) extending along the sides of the
bore 240
toward the cavity 242 to facilitate sealing along sides of a closed ram 34.
[0073] As explained above, the flow control device 232 controls the flow
of
fracturing fluid through the bore 240. Fracturing fluid contains proppant
(e.g., sand)
that props open cracks created by the pressurized fracturing fluid after the
fracturing
fluid is depressurized. The seal system 250 enables the flow control device
232 to
form seals with the housing 238 without using valve seats. However, the flow
of
sand in the fracturing fluid may result in sand buildup. To facilitate the
removal of
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sand or to prevent the buildup of sand within the flow control device 232, the
ram 34 may include one or more grooves/slots in the body 270. For example, the
body 270 may define a groove/slot 336 in the upper surface 276. This
groove/slot 336 may facilitate evacuation of sand from the recess 280 and
reduce
interference from sand on movement of the ram 34 into and out of the recess
280.
In some embodiments, the groove/slot 336 may have a length 338 that is greater
than a depth/length 340 of the recess 280. In still other embodiments, the
groove/slot 336 may also be angled. For example, the groove/slot 336 may form
an
angle 342 with a longitudinal axis 344 of the body 270. The angle 342 of the
groove/slot 336 may enable sand to slide off the upper surface 276.
[0074] In addition to the groove/slot 336, the ram 34 may include
another
groove/slot 346 in the lower surface 278 of the body 270. The groove/slot 346
may
extend from the front face 272 to the rear face 274. This groove/slot 346 may
reduce sand accumulation in the recess 280 and interference from sand on
movement of the ram 34 in axial direction 244 while closing the bore 240.
Furthermore, the groove/slot 346 may facilitate opening of the bore 240 as the
ram 34 moves in axial direction 246. More specifically, sand and fluid
accumulation
in the cavity 242 is able to flow out of the cavity 242 through the
groove/slot 346 as
the ram 34 moves in axial direction 246. In this way, the flow control device
232 may
use little to no grease during operation while still controlling the flow of
fracturing
fluid into and out of the well 12. In other words, the flow control device 232
may
not include grease in the cavity 242 to block proppant from entering the
cavity 242.
[0075] FIG. 34 is a cross-sectional view of the flow control device 232
in
FIG. 32 along lines 34-34. As illustrated, the body 270 of the ram 34 may have
an
oval shape. In operation, the housing 238 reduces deflection of the ram 34 in
directions 370 and 372 by enabling the ram 34 to rest within the recess 280 in
a
closed position as well as by providing grooves that receive the sides of the
ram 34.
More specifically, the body 270 may include opposing side surfaces 374 and 376
that
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rest within respective sidewall grooves 378 and 380 of the housing 238, which
block/reduce movement (e.g., deflection) of the ram 34 in directions 370 and
372. In
addition, the oval shape of the body 270 may block rotation of the ram 34. It
should
be understood that the body 270 of the ram 34 may have a different shape
(e.g.,
square, rectangular, circular, semi-circular). However, if the body 270 of the
ram 34
has a circular shape the flow control device 232 may include an anti-rotation
feature
to orient the seal system 250 and the grooves/slots 336, 346.
[0076] FIG. 35 is a perspective view of the ram 34 of the flow control
device
depicted in FIG. 32. As explained above, the ram 34 includes the seal system
250 that
enables the ram 34 to seal with the housing 238 to block the flow of
fracturing fluid
through the bore 240. The seal system 250 includes the front seal 282 and the
upper
seal 284. In addition to these seals, the seal system 250 includes side seals
400
and 402 that rest within respective grooves/recesses 404 and 406 in the body
270.
The side seals 400 and 402 are also elastomeric seals (e.g., nitrile,
hydrogenated
nitrile) that seal against the housing 238. The side seals 400 and 402 may
extend a
distance 408 along the body 270. In FIG. 35, this distance 408 is less than
the entire
length of the body 270. However, in some embodiments the side seals 400 and
402
may extend along the entire length of the body 270.
[0077] In order to form a seal about the bore 240, the side seals 400
and 402
contact the upper seal 284. As illustrated, the upper seal 284 curves over the
upper
surface 276 until it engages the side seals 400 and 402. In some embodiments,
the
upper seal 284 may include notches/grooves 410 and 412 at respective ends of
the
upper seal 284. These notches/grooves 410 and 412 in the upper seal 284
receive
and contact respective portions 417 of the side seals 400 and 402. In other
embodiments, however, the upper seal 284 does not include notches/grooves 410
and 412.
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[0078] The side seals 400 and 402 are energized by contact between end
surfaces 414 and 416 and the housing 238. As illustrated, the end surfaces
414, 416
extend beyond the front face 272 of the body 270. In operation, the end
surfaces 414 and 416 contact the housing 238 as the ram 34 moves in axial
direction 244 (i.e., surface 288). As the ram 34 continues to move in axial
direction 244, the side seals 400 and 402 compress. The compression drives the
side
seals 400 and 402 radially outward in directions 418 and 420 forming a seal
with the
housing 238. The side seals 400 and 402 also compress against the upper seal
284,
which energizes the top seal 284 as well. Specifically, the portions 417 of
the side
seals 400 and 402 that rest within the notches/grooves 410 and 412 of the
upper
seal 284 transfer energy to the upper seal 284 energizing the upper seal 284
to seal
with the housing 238.
[0079] In some embodiments, the ram 34 may include wear pads 422. The
wear
pads 422 couple to the body 270 and form part of the upper surface 276. In
operation, the wear pads 422 may reduce friction between the ram 34 and the
housing 238 as the ram 34 opens and closes the bore 240. For example, the wear
pads 422 may include Teflon, bronze, among other materials that have a
coefficient
of friction less than that of the body 270. The length of the wear pads 422
may
extend over a portion of the length of the body 270 or they may extend between
the
front face 272 and the rear face 274 along the upper surface 276. In some
embodiments, the lower surface 278 may include one or more wear pads 422 as
well.
Instead of, or in addition to, using wear pads 422, the body 270 may be formed
of a
softer material (e.g., stainless steel) to prevent galling of the housing 238
(e.g., along
the cavity surface 290).
[0080] FIG. 36 is a cross-sectional view of a flow control device 232 in
a closed
position. Over time, the flow of fracturing fluid through the flow control
device 232
may result in the accumulation of proppant (e.g., sand) in the cavity 242. To
facilitate
removal of the proppant within the cavity 242, the flow control device 232 may
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include an agitator 430 that breaks up proppant so that fluid is able to carry
the
proppant out of the cavity 242 through the groove/slot 346. In some
embodiments,
the agitator 430 may also push the proppant out of the cavity 242 as the ram
34
moves axially in direction 244. The agitator 430 may include one or more
blades 432
that extend from the shaft 248. These blades 432 may wrap around the shaft 248
in
spiral or helical manner. In this way, as the shaft 248 moves axially, the
blades 432
push or breakup proppant piles to facilitate removal. In some embodiments, the
shaft 248 may move axially while rotating, enabling the blades 432 to cut into
accumulated piles of proppant, breaking it up to facilitate its removal. The
blades 432 may extend along the length of the shaft 248 or a portion of the
shaft 248. For example, the blades 432 may extend from the rear face 274 to
the
actuator 36. In some instances, proppant may also or instead be flushed from
the
cavity 242 by injecting water or another fluid into the cavity 242 (e.g.,
through ports
in the housing 238 or from the actuator 36).
[0081] FIG. 37 is a cross-sectional view of a flow control device 232.
As
explained above, the flow control device 232 controls the flow of fracturing
fluid.
The seal system 250 enables the flow control device 232 to form seals with the
housing 238 without using valve seats. However, the flow of sand in the
fracturing
fluid may result in the buildup of sand in the cavity 242. To reduce or
prevent the
buildup of proppant in the cavity 242, the ram 34 may include a bottom seal
450
within a groove 452 of the lower surface 278. The bottom seal 450 is also an
elastomeric seal (e.g., nitrile, hydrogenated nitrile) that seals against the
housing 238.
As illustrated, the bottom seal 450 engages and seals against a surface 290
(i.e., cavity
surface) that defines the cavity 242.
[0082] The ram 34 may also include one or more grooves/slots in the body
270.
For example, as shown in FIG. 37, the body 270 may define a groove/slot 336 in
the
upper surface 276 and another groove/slot 454 in the lower surface 278. These
grooves/slots 336 and 454 may facilitate evacuation of sand from the recess
280 and
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reduce interference from sand on movement of the ram 34 into and out of the
recess 280. In some embodiments, the grooves/slots 336, 454 may have a length
338
that is greater than a depth/length 340 of the recess 280 to facilitate
movement of
proppant out of the recess 280. In still other embodiments, one or both of the
grooves/slots 336 and 454 may also be angled. By angling the grooves/slots
336,
454, the grooves/slots 336 and 454 may enable proppant to slide off the ram
34.
[0083] Because of the high pressures used during hydraulic fracturing
operations, hydraulic fluid including proppant may enter the cavity 242. In
order to
remove the proppant as well as enable the ram 34 to retract, the housing 238
may
include one or more apertures 456. The apertures 456 couple to one or more
accumulators 460 that receive proppant and fluid within the cavity 242. The
accumulators 460 enable sand and fluid in the cavity 242 to flow out of the
cavity 242 through the apertures 456 as the ram 34 moves in axial direction
246. In
this way, the flow control device 232 may use little to no grease during
operation
while still controlling the flow of fracturing fluid into and out of the well
12. In
other words, the flow control device 232 may not include grease in the cavity
242 to
block proppant from entering the cavity 242.
[0084] In some embodiments, the housing may include apertures 466 and
468
that couple the cavity 242 to the bore 240 below and above the ram 34. Fluid
flow
through these apertures 466 and 468 is controlled by respective valves 472 and
474.
In operation, these apertures 466 and 468 may enable pressure in the bore 240
to
assist in closing the ram 34 or to enable fluid to escape the cavity 242 when
opening/retracting the ram 34. For example, if pressurized fluid is flowing
through
the bore 240 in direction 372, the valve 474 may be opened and the valve 472
closed
in order to use the pressure of the fluid in the bore 240 to increase the
closing force
on the ram 34 (e.g., supplement the force from the actuator 36). The opposite
would
occur if the pressurized fluid were flowing through the bore 240 in direction
370. It
should also be understood that regardless of the fluid flow direction, the
valves 472
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and 474 may be controlled to facilitate closing depending on which side of the
ram 34 the bore 240 should be sealed on. In other words, sealing the area
below the
ram 34 would involve opening valve 472 and closing valve 474, while sealing
the area
above the ram 34 would involve opening valve 474 and closing valve 472.
[0085] The valves 472 and 474 and apertures 466 and 468 may facilitate
opening
of the ram 34 as well. As explained above, fluid may accumulate in the cavity
242. In
order to open the ram 34, the fluid in the cavity 242 is vented as the ram 34
retracts.
In some embodiments, all of the valves 472 and 474 may be opened to enable
fluid
to vent from the cavity 242 when retracting the ram 34. In another embodiment,
one
of the valves 472 and 474 may be opened to vent. For example, if the pressure
in the
bore 240 above the ram 34 is greater than the pressure below the ram 34, the
valve 472 may be opened and the valve 474 remains closed to facilitate venting
fluid
from the cavity 242. Likewise, if the pressure in the bore 240 above the ram
34 is less
than the pressure below the ram 34 then the valve 474 may be opened and the
valve 472 closed while venting fluid from the cavity 242. In this way, fluid
communication between the cavity 242 and the bore 240 may facilitate opening
and
closing of the ram 34. Also, the flow control device 232 may use little to no
grease
during operation while still controlling the flow of fracturing fluid into and
out of
the well 12.
[0086] Still another example of a frac stack 32 having sealing rams is
shown in
FIG. 38. In this example, the body of the frac stack 32 includes stacked flow
control
devices 532 with sealing rams that can be opened and closed with actuators
(e.g.,
electric actuators, pneumatic actuators, hydraulic actuators, manual
actuators, or a
combination thereof). The sealing rams are depicted as wedge rams 542 and 544
that
can be used to control flow of fracturing or other fluid through the frac
stack 32. As
discussed above with respect to FIG. 29, various additional components (e.g.,
goat
head 26 and wing valves 28 and 30) can be used to control or otherwise
facilitate
flow through the frac stack 32 and the flow control devices 532 of the frac
stack
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body can be connected to one another and to other equipment in any suitable
manner. And as also noted above for FIG. 29, while two flow control devices
532 are
shown in FIG. 38, the frac stack 32 may include some other number of flow
control
devices 532, such as between three and six flow control devices 532 or just a
single
flow control device 532. The flow control devices 532 may be used for large
bore
(e.g., seven-inch) and high pressure (e.g., 15,000 psi) applications. In some
embodiments, the flow control devices 532 are used in place of lower and upper
master gate valves in a fracturing tree. A frac stack 32 may include a
combination of
flow control devices 232 and 532 in some instances. Still further, the flow
control
device 532 could be used apart from the frac stack in other fracturing
operations or
could be used in other (i.e., non-fracturing) flow control contexts in other
embodiments.
[0087] FIG. 39 is a cross-sectional view of one of the flow control
devices 532
of FIG. 38 in an open position. The flow control device 532 includes a housing
538
with a bore 540 for conveying fluid through the housing 538. The flow of fluid
through the bore 540 is controlled with first and second wedge rams 542 and
544.
The wedge rams 542 and 544 rest within respective first and second cavities
546
and 548 of the housing 538 and move axially in directions 550 and 552 (FIG.
40) to
open and close the bore 540. In an open position, the wedge rams 542 and 544
are
completely withdrawn out of the bore 540 enabling fracturing fluid to flow
through
the housing 538 and into the well 12. As explained above, fracturing fluid
includes
proppant (e.g., sand) in order to prop open cracks formed under pressure so
that
hydrocarbons can flow out of a formation. Accordingly, by retracting the wedge
rams 542 and 544 out of the bore 540, the wedge rams 542 and 544 are not
exposed
to the direct flow path of the fracturing fluid through the housing 538, which
may
reduce erosion and wear on the wedge rams 542 and 544.
[0088] The axial position of the wedge rams 542 and 544 are controlled
with
respective first and second actuators 554 and 556. The actuators 554 and 556
may be
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electric actuators, pneumatic actuators, hydraulic actuators, manual
actuators, or a
combination thereof. The first actuator 554 couples to the first wedge ram 542
with
a first shaft 558, and the second actuator 556 couples to the second wedge ram
544
with a second shaft 560. As will be explained below, the flow control device
532
includes a seal system 562 that enables the first and second wedge rams 542
and 544
to form a seal with the housing 538 without valve seats.
[0089] FIG. 40 is a cross-sectional view of the flow control device 532
in a
closed position. The first and second wedge rams 542 and 544 include
respective
bodies 580 and 582 that support the seal system 562. The bodies 580 and 582
include respective angled front faces 584 and 586; rear faces 588 and 590;
upper
surfaces 592 and 594; and lower surfaces 596 and 598. In the closed position,
the
angled front faces 584 and 586 contact each other to close the bore 540. In
addition
to contacting each other, a portion of each front face 584 and 586 rests in
the cavity
of the opposing ram. That is, a portion of the first wedge ram 542 enters the
second
cavity 548, and a portion of the second wedge ram 544 rests within the first
cavity 546. In this arrangement, the flow control device 532 is able to
maintain a seal
within the bore 540 regardless of whether pressurized fluid flows through the
bore 540 in axial direction 600 or 602.
[0090] In operation, the actuator 554 drives the shaft 558 coupled to
the first
wedge ram 542 in axial direction 552 and the actuator 556 drives the shaft 560
coupled to the second wedge ram 544 in axial direction 550. As the front faces
584
and 586 of the respective first and second wedge rams 542 and 544 contact each
other, the front faces 584 and 586 slide over each other. As the front faces
584
and 586 slide over each other, the first wedge ram 542 creates a force in
direction 600 on the second wedge ram 544 that wedges an end portion 604 of
the
second wedge ram 544 between the housing 538 and the first wedge ram 542.
Likewise, the sliding motion enables the second wedge ram 544 to generate a
force in
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direction 602 on the first wedge ram 542 that wedges an end portion 606 of the
first
of the first wedge ram 542 between the housing 538 and the second wedge ram
544.
[0091] As explained above, the flow control device 532 includes the
seal
system 562, which forms a seal between the first and second wedge rams 542
and 544 and between the wedge rams 542, 544 and the housing 538. The seal
system 562 includes front seals 608 and 610 (i.e., elastomeric seals such as
nitrile
seals, hydrogenated nitrile seals). These front seals 608 and 610 (e.g., wedge
seals) rest
and are retained within respective slots 612 and 614 of the first and second
wedge
rams 542 and 544.
[0092] In some embodiments, the seal system 562 may include
energizing plates
that drive the front seals 608 and 610 in respective directions 552 and 550.
For
example, the first wedge ram 542 may include energizing plates 616 and 618,
and the
second wedge ram 544 may include energizing plates 620 and 622. These plates
616,
618, 620, and 622 may be made out of metal or another material that is more
rigid
than the elastomeric material of the front seals 608 and 610. The energizing
plates 616, 618, 620, and 622 are placed on opposite sides of their respective
front
seals 608 and 610. In some instances, the energizing plates 616 and 618 are
configured to extend beyond the front face 584 of the first wedge ram 542 and
the
energizing plates 620 and 622 are configured to extend beyond the front face
586 of
the second wedge ram 544. For example, the energizing plates 616, 618, 620,
and 622
may extend between 1 mm and 20 mm beyond the respective front faces 584
and 586.
[0093] In operation, as the first and second wedge rams 542 and 544
contact
each other the energizing plates 616 and 618 are driven in direction 550
(relative to
the ram 542) and the energizing plates 620 and 622 are driven in direction 552
(relative to ram 544). As the energizing plates 616 and 618 move in direction
550,
they engage ledges 624 and 626 on the elastomeric front seal 608. The force of
the
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energizing plates 616 and 618 on the elastomeric front seal 608 flows through
it and
drives the elastomeric front seal 608 in axial direction 552. In other words,
the force
of the energizing plates 616 and 618 energizes the elastomeric front seal 608
in axial
direction 552 and radially outward against the housing 538 increasing the
sealing
force of the elastomeric front seal 608 against the second wedge ram 544 and
the
housing 538.
[0094] Likewise, as the first and second wedge rams 542 and 544 contact
each
other the energizing plates 620 and 622 are driven in direction 552. As the
energizing
plates 620 and 622 move in direction 552, they engage ledges 628 and 630 on
the
elastomeric front seal 610. The force of the energizing plates 620 and 622 on
the
elastomeric front seal 610 flows through it and drives the elastomeric front
seal 610
in axial direction 550. That is, the force of the energizing plates 620 and
622
energizes the elastomeric front seal 610 in axial direction 550 and radially
outward
against the housing 538 increasing the sealing force of the elastomeric front
seal 610
against the first wedge ram 542 and the housing 538. The energizing plates
616, 618,
620, and 622 may also limit or prevent extrusion of the elastomeric front
seals 608
and 610 (e.g., along the front faces 584 and 586) when closing the wedge rams
542
and 544.
[0095] In some embodiments, the wedge ram 542 may include ledges that
engage the ledges 624 and 626 on the first wedge seal 608. The wedge ram 544
may
also include ledges that engage the ledges 628 and 630 on the second wedge
seal 610.
These ledges on the wedge rams 542, 544 facilitate retention of the wedge
seals 608
and 610 during operation.
[0096] As illustrated, the first wedge ram 542 includes a lower seal 632
that rests
and is retained within a groove 634 in the lower surface 596. The lower seal
632
engages and seals against the housing 538 within the cavity 546. The second
wedge
ram 544 includes an upper seal 636 that rests and is retained within a groove
638 in
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the upper surface 594. The upper seal 636 engages and seals against the
housing 538
within the cavity 548. Together the lower seal 632, upper seal 636, first
front seal 608,
and second front seal 610 form part of seal system 562 that seals between the
first
and second wedge rams 542, 544 and between these wedge rams 542, 544 and the
housing 538 to block the flow of fracturing fluid through the bore 540. It
should be
understood that the lower seal 632 and the upper seal 636 are also elastomeric
seals
(e.g., nitrile, hydrogenated nitrile). By including elastomeric seals in the
seal
system 562, the flow control device 532 is able to form seals that block the
flow of
fracturing fluid through the bore 540 without using valve seats. Furthermore,
because elastomeric seals may be less susceptible to pitted surfaces,
including
elastomeric seals in the flow control device 532 may facilitate sealing in an
erosive
hydraulic fracturing environment. Accordingly, instead of forming a metal-to-
metal
seal between a ram and valve seats, the elastomeric seals of the flow control
device 532 enable seal formation between the first and second wedge rams 542,
544
and the housing 538.
[0097] Over time, the flow of fracturing fluid through the flow control
device 532 may result in the accumulation of proppant (e.g., sand) in the
cavities 546,
548. To facilitate removal of the proppant from the cavities 546, 548, the
flow
control device 532 may include one or more agitators 640 that breaks up
proppant to
facilitate removal. In some embodiments, the agitator 640 may also push the
proppant out of the cavities 546, 548 as the first or second wedge rams 542,
544
move axially. In some embodiments, the agitator 640 may include one or more
blades 642 that extend about the shafts 558 and 560. These blades 642 may wrap
around the shafts 558 and 560 in a spiral or helical manner. In this way, as
the
shafts 558 and 560 rotate, the blades 642 cut into accumulated piles of
proppant,
breaking it up to facilitate removal. The blades 642 may extend along the
length of
the shafts 558, 560 or a portion of the shafts 558, 560. In some instances,
proppant
may also or instead be flushed from the cavities 546, 548 by injecting water
or
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another fluid into the cavities 546, 548 (e.g., through ports in the housing
538 or
from the actuators 554, 556).
[0098] FIG. 41 is a perspective view of the first and second wedge rams
542
and 544. As explained above, the flow control device 532 includes the seal
system 562 that enables the rams 542, 544 to form seals with the housing 538
to
block the flow of fracturing fluid through the bore 540. As illustrated, the
front
seals 608 and 610 extend along the sides of the first and second wedge rams
542
and 544. In this way, the front seals 608 and 610 enable sealing along the
sides of the
respective ram bodies 580 and 582. Furthermore, and in some embodiments, the
front seals 608 and 610 seal with and energize the lower seal 632 and the
upper
seal 636. As illustrated, the upper seal 636 curves over the upper surface 594
until it
engages (e.g., contacts) the front seal 610. Similarly, the lower seal 632
curves over
lower surface 596 and engages (e.g., contacts) the front seal 608. In some
embodiments, the upper seal 636 and lower seal 632 may include respective
notches/grooves 650, 652 that receive and contact respective portions of front
seals 610 and 608. But the upper seal 636 and lower seal 632 do not include
respective notches/grooves 650, 652 in some other embodiments.
[0099] The lower seal 632 and upper seal 636 are energized by contact
with
respective front seals 608, 610. As explained above, as the front faces 584
and 586 of
the first and second wedge rams 542 and 544 contact each other they energize
the
front seals 608 and 610 with the energizing plates 616, 618, 620, and 622. The
compression of the front seals 608 and 610 drives the front seals 608 and 610
radially outward in directions 654, 656 and towards the opposing wedge ram, as
well
as compresses/energizes the respective lower seal 632 and upper seal 636. More
specifically, force from the front seal 608 is transferred to the lower seal
632, which
compresses and is driven in direction 602 and into sealing contact with the
housing 538. Likewise, force from the front seal 610 is transferred to the
upper
seal 636, which compresses and is driven in direction 600 and into sealing
contact
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with the housing 538. Furthermore, the force on the respective front faces 584
and 586 generated from the front faces 584 and 586 sliding over one another
blocks
the lower seal 632 and the upper seal 636 from de-energizing from their
respective
sealing contact surfaces because a portion of the front faces 584 and 586
rests in the
cavity of the opposing ram. In this arrangement, the flow control device 532
is able
to maintain a seal in both directions 600 and 602 within the bore 540
regardless of
whether pressurized fluid flows through the bore 540 in axial direction 600 or
602.
[0100] In some embodiments, the first and second wedge rams 542, 544 may
include wear pads 660. In operation, the wear pads 660 may reduce friction
between
the first and second wedge rams 542 and 544 and the housing 538 as the first
and
second wedge rams 542 and 544 open and close the bore 540. For example, the
wear
pads 660 may include Teflon, bronze, or other materials with a coefficient of
friction
less than that of the material of the bodies 580 and 582. The length of the
wear
pads 660 may extend over a portion of the length of the bodies 580 and 582 or
they
may extend along their entire length. It should be understood that wear pads
660
may couple to the both the upper surfaces 592, 594 and lower surfaces 596, 598
of
the wedge rams 542, 544. Instead of, or in addition to, using wear pads 660,
the
bodies 580 and 582 may be formed of a softer material (e.g., stainless steel)
to
prevent galling of the housing 538 (e.g., along surfaces defining cavities 546
and 548).
[0101] As explained above, the flow control device 532 controls the flow
of
high-pressure fracturing fluid through the bore 540. Fracturing fluid contains
proppant (e.g., sand) that props open cracks created by the pressurized
fracturing
fluid after the fracturing fluid is depressurized. To facilitate the removal
of sand or to
block the buildup of sand within the flow control device 532 and to facilitate
opening of the flow control device 532, the first and second wedge rams 542
and 544 may include one or more grooves/slots in their respective bodies 580
and 582. For example, the body 580 may define a groove/slot 662 in the upper
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surface 592. This groove/slot 662 extends from the front face 584 to the rear
face 588 enabling fluid to flow and equalize pressure in the cavity 546.
Similarly, the
body 582 may define a groove/slot 664 in the lower surface 598. This
groove/slot 664 extends from the front face 586 to the rear face 590 enabling
fluid
to flow and equalize pressure in the cavity 548 as well as facilitate removal
of sand
buildup in the cavity 548.
[0102] FIG. 42 is a perspective view of an embodiment of the front seals
608,
610 (e.g., wedge seals). The front seals 608, 610 include an elastomer body
680 with
an angled surface 682 configured to seal against each other. In some
embodiments,
the front seals 608, 610 may also include a retention feature 684 that
facilitates
coupling of the front seals 608, 610 to the wedge rams 542, 544. The retention
feature 684 may include a block 686 of resilient material (e.g., metal)
embedded in
the body 680. The block 686 defmes one or more apertures 688 (e.g., 1, 2, 3,
4, 5)
that are configured to receive a pin that couples the front seal 608, 610 to
the
bodies 580, 582 of the wedge rams 542, 544.
[0103] FIG. 43 is a cross-sectional view of a wedge ram 542, 544 with a
front
seal 608, 610. As illustrated, the front seal 608, 610 is inserted into the
body 580, 582
until the apertures 688 in the retention feature 684 align with a pin aperture
702. A
pin 704 may then be inserted through the pin aperture 702 and through the
aperture 688 in the retention feature 684 and into a recess 706 in the body
580, 582.
In this way, the surfaces of the body 580, 582 that define the recess 706 and
the
aperture 702 reduce or block movement of the pin 704 in axial directions 550,
552.
As illustrated, the aperture 688 in the block 686 is larger than the pin 704.
This
enables the front seal 608, 610 to move in response to changes in pressure on
the
front seal 608, 610 as the flow control device 532 opens and closes. In some
embodiments, the pin 704 may be molded into the lower and upper seals 632, 636
that rest within respective grooves 634, 638.
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[0104] FIG. 44 is a cross-sectional view of a flow control device 532 in
an open
position. To reduce or block the buildup of proppant in the cavities 546, 548,
the
first wedge ram 542 may include an upper seal 734 in a groove 736 of the upper
surface 592. The upper seal 734 works with the lower seal 632 to form a seal
about
the cavity 546 to block proppant from entering the cavity 546. Similarly, the
second
wedge ram 544 may include a lower seal 738 in a groove 740 of the lower
surface 598. The lower seal 738 in combination with the upper seal 636 form a
seal
about the cavity 548 to block proppant from entering the cavity 548. By
creating a
seal about the cavities 546 and 548, the seals 734 and 738 may block or reduce
pressure equalization in the cavities 546 and 548.
[0105] To facilitate pressure equalization in the cavities 546 and 548,
the
housing 538 may include one or more apertures 742 and 744 in the housing 538.
The
aperture 742 couples one or more accumulators 746 to the cavity 546 to receive
fluid. More specifically, fluid in the cavity 546 is able to flow out of the
cavity 546
through the apertures 742 as the first wedge ram 542 moves in axial direction
550.
Likewise, aperture 744 couples one or more accumulators 748 to the cavity 548
to
receive fluid as the second wedge ram 544 moves in axial direction 552. In
some
embodiments, the accumulators 746 and 748 may also pump fluid into the
respective
cavities 546 and 548 to increase the force on the wedge rams 542 and 544. In
other
words, the accumulators 746 and 748 may provide pressurized fluid that
supplements
(i.e., generate additional force on the rear faces 588 and 590) or replaces
the force
from the actuators 554 and 556.
[0106] In still other embodiments, the flow control device 532 may
include
apertures 750 and 752 that couple the cavities 546 and 548 to the bore 540
below the
wedge rams 542, 544, as well as apertures 754 and 756 that couple the cavities
546
and 548 to the bore 540 above the wedge rams 542, 544. Fluid flow through
these
apertures 750, 752, 754, and 756 is controlled by respective valves 758, 760,
762,
and 764. In operation, these apertures 750, 752, 754, and 756 may enable
pressure in
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the bore 540 to assist in closing the wedge rams 542, 544 or to enable fluid
to escape
the cavities 546, 548 when opening the wedge rams 542, 544. For example, if
pressurized fluid is flowing through the bore 540 in direction 600, the valves
758
and 760 may be opened and the valves 762 and 764 closed in order to use the
pressure of the fluid in the bore 540 to increase the closing force on the
wedge
rams 542, 544 (e.g., supplement the force from the actuators 554 and 556). The
opposite may occur if the pressurized fluid were flowing through the bore 540
in
direction 602. It should also be understood that regardless of the fluid flow
direction, the valves 758, 760, 762, and 764 may be controlled to facilitate
closing
depending on which side of the wedge rams 542, 544 the bore 540 should be
sealed
on. In other words, sealing the area below the wedge rams 542, 544 would
involve
opening valves 758, 760 and closing valves 762, 764, while sealing the area
above the
wedge rams 542, 544 would involve opening valves 762, 764 and closing valves
758,
760.
[0107] The valves 758, 760, 762, and 764 and apertures 750, 752, 754,
and 756
may facilitate opening of the wedge rams 542 and 544 as well. As explained
above,
fluid may accumulate in the cavities 546 and 548. In order to open the wedge
rams 542 and 544, the fluid in the cavities 546 and 548 is vented as the wedge
rams 542, 544 retract. In some embodiments, all of the valves 758, 760, 762,
and 764
may be opened to enable fluid to vent from the cavities 546 and 548 when
retracting
the wedge rams 542, 544. In another embodiment, a subset of the valves 758,
760,
762, and 764 may be opened to vent. For example, if the pressure in the bore
540
above the wedge rams 542, 544 is greater than the pressure below the wedge
rams 542, 544 the valves 758 and 760 may be opened and the valves 762 and 764
may remain closed to facilitate venting fluid from the cavities 546, 548.
Likewise, if
the pressure in the bore 540 above the wedge rams 542, 544 is less than the
pressure
below the wedge rams 542, 544 then the valves 762 and 764 may be opened and
the
valves 758 and 760 closed while venting fluid from the cavities 546 and 548.
In this
way, fluid communication between the cavities 546, 548 and the bore 540 may
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facilitate opening and closing of the wedge rams 542, 544. Also, the flow
control
device 532 may use little to no grease during operation while still
controlling the flow
of fracturing fluid into and out of the well 12.
[0108] From the discussion above, it will be appreciated that a
fracturing system
in one embodiment includes a wellhead and a frac stack coupled to the
wellhead. The
frac stack can include a flow control device that can move between open and
closed
positions to open and close a bore for conveying a fracturing fluid, and the
flow
control device can include a housing defining a first cavity, a second cavity,
and the
bore. A first wedge ram can move axially within the first cavity and a second
wedge
ram can move axially within the second cavity. In the closed position, a first
portion
of the first wedge ram rests within the second cavity and a second portion of
the
second wedge ram rests within the first cavity. The wedge rams can include
elastomer
wedge seals. First and second plates for energizing an elastomer wedge seal
may be
received in a slot of a wedge ram. An elastomer wedge seal can have an
aperture for
receiving a pin to block removal of the wedge seal from a wedge ram. The first
wedge ram can have an upper surface with a groove that enables fluid
communication between the bore and the first cavity. The first wedge ram can
have a
lower surface with a seal groove for receiving a lower elastomeric seal for
sealing
with the housing inside the first cavity. The second wedge ram can have a
lower
surface with a groove that enables fluid communication between the bore and
the
second cavity. The second wedge ram can have an upper surface with a seal
groove
for receiving an upper elastorneric seal for sealing with the housing inside
the second
cavity.
[0109] In another embodiment, a system includes a flow control device
that can
move between open and closed positions to open and close a bore. The flow
control
device can include: a housing defining a first cavity, a second cavity, and
the bore; a
first wedge ram that can move axially within the first cavity; and a second
wedge ram
that can move axially within the second cavity. The first wedge ram can
include a
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lower seal in a first groove on a lower surface and the second wedge ram can
include
an upper seal in a second groove on an upper surface. In the closed position,
a first
portion of the first wedge ram rests within the second cavity and a second
portion
of the second wedge ram rests within the first cavity. A wedge ram can include
a slot
for receiving an elastomer wedge seal. A wedge ram can include plates for
contacting
an opposing wedge ram and energizing an elastomer wedge seal of the wedge ram.
The elastomer wedge seal can include an aperture for receiving a pin to block
removal of the wedge seal from a wedge ram. The system may also include a
shaft
coupled to a wedge ram, and the shaft can include a blade for pushing or
agitating
proppant in the first or second cavity as the wedge ram moves axially.
Additionally,
the system can include an accumulator coupled to received fluid from the first
or
second cavity as the first or second wedge ram retracts.
[0110] In another embodiment, a system includes a first wedge ram
that can
move axially within a first cavity and a second wedge ram that can move
axially
within a second cavity. When the wedge rams are moved to a closed position, a
first
portion of the first wedge ram can rest within the second cavity and a second
portion of the second wedge ram can rest within the first cavity to seal a
bore. The
system can include a housing defining the first cavity, the second cavity, and
the bore.
The first and second wedge rams can include elastomer wedge seals that engage
one
another to seal the bore. A wedge ram can include a groove that enables fluid
communication between the bore and the first or second cavity.
[0111] While the aspects of the present disclosure may be
susceptible to various
modifications and alternative forms, specific embodiments have been shown by
way
of example in the drawings and have been described in detail herein. But it
should be
understood that the invention is not intended to be limited to the particular
forms
disclosed. Rather, the invention is to cover all modifications, equivalents,
and
alternatives falling within the spirit and scope of the invention as defined
by the
following appended claims.
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