BACKGROUND OF THE INVENTION
Field of the Invention
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The invention is related generally to the field of winches and spooling devices.
More specifically, the invention relates to spooling devices which have more than one
independently driveable spool disposed in a mounting space typically used for a single
spool.
Description of the Related Art
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Well logging systems known in the art include a winch having a spool of armored
electrical cable wound on the spool. Well logging instruments are lowered into and lifted
out of wellbores for various purposes by rotating the spool (called a "cable drum") to
extend and retract, respectively, the armored electrical cable.
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Armored electrical cables for use in well logging operations have a number of
electrical conductors therein, and an external diameter which are related to the type of
logging instruments being used, the expected depth in the wellbore to which the
instruments are to be lowered, and whether subsurface conditions in the wellbore may
require the use of fluid pressure control devices at the earth's surface. Logging
instruments which make specialized measurements of properties of the earth formations
penetrated by the wellbore often require multiple insulated electrical conductors to carry
electrical power to the instruments from the earth's surface, and to transmit signals back
to the earth's surface for recording and interpretation. Typically, multi-conductor cable
has a relatively large weight per unit length. As a result, multi-conductor cables typically
have a relatively large external diameter because of the amount of armoring required to
provide adequate tensile strength to the cable.
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Conversely, simple instruments, particularly "perforating" and other mechanical
wellbore servicing devices, may only require a single insulated electrical conductor to
perform all required functions. Especially in the case of operating perforating devices,
various types of pressure control devices are used at the earth's surface. Such pressure
control devices require that the cable be "threaded through" cable-diameter openings in
them. A mechanical/electrical coupling which connects the cable to the logging
instruments, known as a cable head" must typically be coupled to the cable after
threading the cable through the openings in the pressure control equipment. As is well
known in the art, electrical cables used with pressure control equipment typically have as
small as practical an external diameter (OD) to reduce the tendency of the cable to be
expelled from the wellbore when fluid pressure builds up inside the pressure control
equipment. Still other well logging cables include a single conductor, but have a large
OD and numerous armor wires for operations requiring high breaking strength on the
cable, such as for setting mechanical devices in an unpressurized wellbore, or when
lifting relatively heavy logging instruments or perforating guns.
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Frequently, well logging operations require using both large OD-multi-conductor,
or single conductor cables, and small OD single conductor cables in a single set of
operations. Some well logging units have two separate, independently driven cable
drums on them to accommodate these operations. Such well logging units, while quite
effective, obviously have greater cost than single-drum well logging units because they
have two completely independent winch systems. Other well logging units known in the
art have a single winch drum which is "split". A split drum includes two exterior flanges
on the axial outer ends of the drum, and a third flange in a selected axial position between
the ends of the drum. Split drums have wound thereon both types of logging cables so
that the foregoing multi-purpose well logging operations can be carried out. A limitation
of split drum winch systems is that both cables rotate simultaneously. It is necessary to
remove the cable head from the unused cable during operations which require use of the
other cable. Even if the cable head need not be removed in some cases, it may be
desirable to already have the smaller OD cable "threaded through" the pressure control
equipment to save time during operations at the wellbore site. This is not possible on a
split drum system while operating the winch drum to use the larger OD cable.
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What is needed is a winch system which provides the space advantages of a split
drum, while enabling separate rotation of two different logging cables.
SUMMARY OF THE INVENTION
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The invention is a winch system which includes a first drum rotatably supported
in a cradle, a second drum rotatably supported in the cradle axially alongside the first
drum and rotatable independently of the first drum, and a drive system selectively
connectible to the first drum and the second drum. In one embodiment, the first drum is
rotatably supported at one end by a first bearing in one end of the cradle, the second drum
is rotatably supported at one end by a second bearing in another end of the cradle, and the
second drum is rotatably supported at another end by at least one bearing in a support
bore in the first drum.
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In one embodiment, the drive system is directly coupled to the first drum and
comprises an interlock to rotatably couple the first drum to the second drum.
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In another embodiment, the drive system comprises a drive member
independently rotatable with respect to the first drum and the second drum, and a first and
a second interlock each selectively operable to couple the first and second drums,
respectively, to the drive member.
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In another embodiment, the drive system comprises a first drive unit operably
coupled to the first drum and a second drive unit operably coupled to the second drum.
BRIEF DESCRIPTION OF THE DRAWINGS
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- Figure 1 shows a cross-sectional view of one embodiment of a dual-drive winch
system.
- Figure 2 shows the embodiment of Figure 1 where the two drums may rotate
independently.
- Figure 3 shows an alternative embodiment in which either the first drum or the
second drum may be driven individually by a single drive unit.
- Figure 4 shows another embodiment wherein the first drum and second drum each
has its own drive unit.
- Figure 5 shows an example of a dual drum winch having improved load carrying
capacity.
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DETAILED DESCRIPTION
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Generally speaking, the invention is a winch system which includes two side-by
side cable drums mounted in a cradle. The two cable drums are to rotate independently
of each other, while being fit into a Space otherwise adapted for a single winch drum or a
"split drum".
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One embodiment of a dual-drum winch 10 according to the invention is shown in
Figure 1. A cradle 11 as shown in Figure 1 can be the same or similar to those used to
rotatably support a single cable drum or a split drum as are known in the prior art. The
cradle 11 rotatably supports a cable drum on bearings 20, 22. In this embodiment, the
cable drum is a "dual" drum consisting of a first drum 12 and a second drum 14. A first
cable 16, and a second cable 18 are spooled, respectively, on first drum 12 and second
drum 14, The first drum includes a first flange 12A and a second flange 12B to axially
restrain a first cable 16 to be wound on the first drum 12. The second drum 14 includes
similar flanges 14A, 14B to axially restrain a second logging cable 18 to be wound on the
second drum 14.
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The first drum 12 includes a bearing spindle 12C which at one end turns inside a
support bearing 20 in the cradle 11. The bearing 20 can be a pillow block as is
conventional for rotatable cable drum mounting. The second drum 14 also rotates about
a spindle 14C which is supported in a bearing 22 in the other side of the cradle 11. The
support bearing 22 can also be a pillow block or similar type of bearing. Second drum 14
is rotatably supported at the other end by at least one coaxial bearing 15. Coaxial bearing
15 is disposed inside a support bore 12E in the interior of the first drum 12. Practical
embodiments of the invention may include more than one coaxial bearing 15 in the
support bore 12E, preferably separated by as much axial distance between them as
practical. In this way, the first drum 12 and the second drum 14 may rotate
independently of each other while fitting in a conventional cradle 11, using bearings 20,
22, that are typically used for a single or split drum winch system.
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It should be clearly understood that the particular configuration shown in Figure
1, which has spindle 14C extend from the second drum 14 into the corresponding support
bore 12E in the first drum 12, so that the first drum 12 can rotate about the coaxial
bearings 15 is only one possible configuration of this embodiment. Alternatively, the
spindle 12C of the first drum 12 could extend into a corresponding support bore (not
shown in Figure 1) in the interior of the second drum 14, wherein the coaxial bearings 15
would be located. This is the functional equivalent of the configuration shown in Figure
1 and has the same advantages of that configuration, which will be further explained
below.
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An advantage of the embodiment shown in Figure 1 (and its alternative as
explained above) is that both the first drum 12 and second drum 14 can each have a cable
passage (not shown in Figure 1). The cable passage is formed, and terminates at one end,
substantially in the center of the respective spindles 12C, 14C. The cable passage
terminates at its other end on the cylindrical surface that supports the cable 16, 18 wound
on each drum 12, 14 and at the bearing end of the respective spindle 12C, 14C. Such
cable passages are typical for cable drums known in the art, and the purpose of the cable
passage (not shown), as is known in the art, is to provide a conduit from the interior
cylindrical surface of the cable drum to the center of a slip ring assembly, or "collector"
assembly. The collector is typically mounted on the bearing end of the cradle 11. As is
conventional for a split drum winch, in the independently rotatable drum system of this
embodiment, the first drum 12 includes at the bearing end thereof a first collector 12D.
Correspondingly, the second drum 14 includes a sccond collector 14D at its bearing end.
Both collectors 12D, 14D can be any suitable type known in the art to enable electrical
coupling between a rotating member and a rotationally fixed member. In this
embodiment, as is conventional in the art, the rotationally fixed member is the cradle 11.
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Other embodiments may have the spindle 14C of the second drum 14 fully
supported by both bearings 20, 22 on the cradle 11. In such embodiments, the first drum
12 would include only the support bore 12E therein, and coaxial bearings 15. It is also
possible to have a spindle which extends between bearings 20 and 22, and is a separate
element entirely from the first and second drums. The drums 12, 14 in such
embodiments would rotate independently about the spindle on bearings in a support bore
in each drum. Such embodiments would require each drum to have a different form of
passage for the cable wound thereon to be conducted to the respective collector.
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In the embodiment of Figure 1, the first drum 12 is rotated by a drive system
including a chain 28 and power unit 30. The chain 28 and power unit 30 can be any type
known in the art. In this embodiment, the chain 28 and power unit 30 are the same as
would be used to drive a single drum or split drum. This embodiment has the advantage
of being able to directly replace a single drum or split drum in a drive system and cradle
already adapted to the single drum or split drum. The first drum 12 is stopped from
rotating by a first brake band 26. The first brake band 26 can be any type known in the
art for stopping a winch drum. Correspondingly, the second drum 14 is stopped by a
second brake band 24, In this embodiment, the brake bands 24, 26 can be the same as
used in a single drum or split drum winch, but the brake bands 24, 26 should be adapted
to be separately controllable to enable separate rotation of the drums 12, 14.
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In this embodiment, only the first drum 12 is driven by the chain 28 and power
unit 30. To drive the second drum 14, in this embodiment, an interlock 32 is engaged to
rotationally couple the first drum 12 to the second drum 14. The interlock 32 in this
embodiment can be a pin or the like which engages corresponding holes in the flanges
14A, 14B, 12B of the drums 14, 12 respectively. In Figure 1, the interlock pin 32 is
shown engaging the second flange 12B on the first drum to couple rotation of the first
drum 12 to the second drum 14.
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The same embodiment is shown in Figure 2 with the interlock 32 disengaged, so
that the first drum 12 is driven by the drive unit (chain 28 and power unit 30), while the
second drum 14 is not rotated. Typically the second brake band 24 will be set to stop
rotation of the second drum 14 when the interlock 32 is disengaged as shown in Figure 2.
However, as the second drum 14 is otherwise free to rotate, irrespective of rotation of the
first drum 12, the system operator may in some cases manually pull some of the second
cable 18 from the second drum 14 to perform any activities which may require extending
the second cable 18.
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It is contemplated that the embodiment shown in Figures 1 and 2 would be used
where the first cable 16 is a large diameter multiple conductor cable not requiring
uncoupling of a cable head (not shown) to "thread through" pressure control equipment.
The second cable 18 is contemplated as being a small diameter cable which can be thread
through pressure control equipment (not shown), and have coupled thereto a cable head
(not shown). In this way, the pressure control equipment may be assembled to the second
cable 18 prior to use of the winch system 10, while operations using the first drum 12 and
first cable 16 may proceed uninterrupted.
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An alternative embodiment of the winch system is shown in Figure 3. In the
embodiment of Figure 3, the chain 28 and power unit 30 arc positioned so that the chain
is in between the first drum 12 and the second drum 14. A drive sprocket 28B is
rotatably supported on the spindle 14C by a bearing 28A. The drive sprocket 28B can be
selectively coupled to either or both the first drum 12 by a first interlock 32A, which can
be similar to the interlock (32 in Figure 1) of the previous embodiment, and by a second
interlock 32B to the second drum 14. In the embodiment of Figure 3, either or both
drums 12, 14 may be rotated.
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Yet another embodiment, shown in Figure 4, includes a first drive chain 28A and
first power unit 30A to operate the first drum 12, and a second drive chain 28C and
power unit 30B to operate the second drum. In the embodiment of Figure 4, the drums
12, 14 may be operated completely separately, including in different directions. The
embodiment shown in Figure 4 makes possible carrying out well logging operations on
two wellbores simultaneously.
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A particular embodiment shown in Figure 5 includes a thrust bearing 34 disposed
between the adjacent flanges 12B, 14A of the first drum 12 and second drum 14,
respectively, the embodiment shown in Figure 5 can have improved load carrying
capacity. In some of the embodiments of the invention, such as shown in Figure 1, for
example, some of the drum load is carried by the coaxial bearings (15 in Figure 1).
Depending on the position and number of such bearings, there may still be some residual
load applied as a torque which is applied in a direction to "twist" the axis of rotation of
the drums 12, 14. Some of this load can be transferred between the drums by using the
thrust bearing 34 between the adjacent drum flanges 12B, 14A. The thrust bearing 34
can be any type suitable for taking the thrust load between the flanges 12B, 14A, for
example a roller bearing, ball bearing or torrington (radial roller thrust) bearing. The
embodiment shown in Figure 5 may also provide an additional benefit by reducing the
load carrying capacity required on each drum in the spindle area (or support bore area) so
that the adjacent flanges 12B, 14A may be positioned closer to the axial outermost extent
of the corresponding drum 12, 14. This will provide each dim 12, 14 with some
additional cable carrying capacity.
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The invention provides a winch system which enables operating more than one
winch drum separately from another winch drum, while maintaining the overall
dimensions of single or split drum winch systems known in the art. The winch system of
the invention may prove particularly useful in retrofitting single or split drum winch
systems known in the art without extensive modification to the logging unit chassis or
winch cradle.
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While the foregoing invention has been described in terms of specific
embodiments, it will be readily apparent to those skilled in the art that other embodiments
of the invention can be devised which do not depart from the spirit of the invention as
disclosed herein. Accordingly, the invention shall be limited in scope only by the
attached claims.
