Note: Descriptions are shown in the official language in which they were submitted.
CA 02607466 2007-10-23
1 "AC POWERED SERVICE RIG"
2
3 FIELD OF THE INVENTION
4 Embodiments of the invention relate to service rigs for servicing
wellbores and, more particularly, to an integrated power system for powering
at
6 least the propulsion, drawworks and sandline on a service rig.
7
8 BACKGROUND OF THE INVENTION
9 Oil wells typically require some servicing during the lifetime of the
wellbore whether it be to increase production, such as by acidizing or
fracturing
11 the formation and the like, perform testing on the formation or the
wellbore
12 integrity, replace components such as sucker rods or production tubing or
casing
13 or to perform a variety of other operations as necessary.
14 Service rigs are typically designed to at least have the capacity to
trip out or run in the production tubing and to run in and trip out a variety
of
16 downhole tools. Conventionally, the service rig generally comprises at
least a
17 drawworks for raising and lowering tubulars and the like and typically a
sandline
18 for raising and lowering downhole tools such as during swabbing operations.
19 Each of the drawworks and sandline are typically powered by diesel motors
to
which they are mechanically connected. The conventional powering systems
21 typically do not provide as fine a motor control of the drawworks and the
sandline
22 as is desired for servicing operations. AC motors are used in the drilling
industry
23 where weight is less of a limitation on design.
24 Production tubing typically cannot handle as much torque as a drill
stem and therefore more control is required for tripping out and running in of
I
CA 02607466 2007-10-23
1 production tubing as compared to drill pipe. Conventional positioning of
2 components into or out of the wellbore for servicing therefore has required
3 careful and continuous monitoring and management of at least the drawworks
4 and sandline systems by the onsite driller to ensure safe operations.
Conventionally power has been provided for braking systems on
6 the drawworks and the sandline drums through diesel motors and mechanical
7 connections associated therewith. Similarly in conventional rigs, hydraulic
motor
8 systems are also provided to operate tongs and slips required to break or
make
9 sections of tubing from the tubing string as it removed from or inserted
into the
wellbore.
11 In many cases, where the formation is to be treated by chemicals,
12 pumping units are brought onsite to provide specialized treatment fluids
which
13 are pumped into the wellbore. The pumping unit is typically provided with a
14 separate power source onsite.
Service rigs are generally portable rigs which comprise a
16 transportable platform mounted on an undercarriage and which are powered by
17 a propulsion system for moving the rig from wellsite to wellsite.
Conventionally
18 propulsion systems for service rigs are separately powered and typically
19 comprise at least a large diesel engine carried on the platform and
mechanically
connected to the transmission through a gear box. A plurality of axle/wheel
21 configurations are typically available for the undercarriage so as to
conform to
22 Department of Transport regulations. Service rigs must be capable of
carrying a
23 significant amount of weight given the diverse equipment mounted thereon
and
24 must also be able to meet regulations governed by road bans to permit
servicing
of wellbores throughout the year and under a variety of environmental
condition.
2
CA 02607466 2007-10-23
1 This becomes a challenge for rig manufacturers who must balance the
2 competing requirement of the industry for greater functionality of the rig
while
3 trying to reduce the weight to meet the road ban conditions.
4 Additionally, there are electrical requirements onsite to support
servicing operations such as hotel loads, onsite lighting and other such
6 requirements which are conventionally provided by one or more small
generators
7 separately provided.
8 There is a need to provide improved power systems for service rigs
9 that are efficient, supply the needs of the operations at the wellsite and
which do
not add significantly to the problems associated with the weight of the rig so
as
11 to maintain maximum transportability.
12
3
CA 02607466 2007-10-23
1 SUMMARY OF THE INVENTION
2 A substantially electrically-powered service rig housed on a single
3 mobile platform utilizes electrical power generated by an on-board engine-
driven
4 AC generator to power an electrical propulsion system, a drawworks system
and
a sandline system. Further, through use of electrical umblicals power
6 requirements for separately transportable mud pumps systems and hotel loads
7 may be met. In some embodiments, the prior art use of three generators can
be
8 reduced to one.
9 The system utilizes permanent magnet motors to drive a semi or
fully automatic manual transmission and the driven shafts of the drawworks and
11 sandline drums under the control of programmable logic controllers through
12 variable frequency drives. Use of the permanent magnet motors, the
electrical
13 propulsion system and electric motor braking systems for the propulsion
system
14 and drawworks and sandline drums results in a significant weight reduction
over
the use of conventional induction motors enabling integration of the
propulsion
16 system, drawworks system and sandline system on a single mobile unit and
17 which meets transport regulations.
18 In a broad aspect of the invention, an electrically-powered well
19 service rig comprises: a mobile platform for transporting the service rig;
an
engine-driven generator carried by the platform for generating AC power; a
21 propulsion system carried by the platform for transporting the mobile
platform
22 service rig having a collapsible mast thereon, the propulsion system having
a
23 permanent magnet propulsion motor for driving the platform, a propulsion
24 variable frequency drive (VFD) connected between the generator and the
propulsion motor; a drawworks system carried by the platform and having blocks
4
CA 02607466 2007-10-23
1 adapted for raising and lowering a plurality of tubulars into and out of a
wellbore,
2 the drawworks system having at least a drawworks drum having drawworks
3 cable wound thereon and rotatably driven by a permanent magnet drawworks
4 motor; a drawworks VFD connected between the generator and the drawworks
motor; a sandline system carried by the platform and adapted for raising and
6 lowering a sandline tool into and out of a wellbore, the sandline system
having at
7 least a sandline drum having sandline cable wound thereon and rotatably
driven
8 by a permanent magnet sandline motor; a sandline VFD connected between the
9 generator and the sandline motor; and one or more programmable logic
controllers (PLC) carried by the platform for outputting speed setpoints to
the
11 propulsion VFD, the drawworks VFD; and the sandline VFD.
12
13 BRIEF DESCRIPTION OF THE DRAWINGS
14 Figure 1A is a perspective view of a substantially fully electrically-
powered service rig according to an embodiment of the invention, a collapsible
16 mast being shown in a folded transport position;
17 Figure 1 B is a plan view schematic illustrating components of the
18 rig according to Fig. 1A;
19 Figure 2 is a right perspective rear view of the service rig of Fig. 1,
the mast and railings removed for clarity;
21 Figure 3 is a left perspective front view of the service rig of Fig. 1,
22 the mast and railings removed for clarity;
23 Figure 4 is a plan view according to Fig. 2;
24 Figure 5 is a bottom view according to Fig. 2, an engine, generator
and differential removed for clarity;
5
CA 02607466 2007-10-23
1 Figure 6 is a schematic illustrating an electrical power supply and
2 control system for an embodiment according to Fig. 1;
3 Figure 7 is a schematic of an electrical power and control system
4 for a propulsion system for an embodiment according to Fig. 1;
Figure 8 is a schematic of an electrical power and control system
6 for a drawworks system for an embodiment according to Fig. 1;
7 Figure 9 is a schematic of an electrical power and control system
8 for a sandline system for an embodiment according to Fig. 1;
9 Figure 10 is a side schematic view of a drawworks system for an
embodiment according to Fig. 1, illustrating a control system for the
drawworks
11 drum and sensors for providing feedback to a drawworks PLC;
12 Figure 11 is a schematic illustrating operational positions of the
13 drawworks of Fig. 10 wherein drawworks blocks are raised and lowered for
14 positioning a tubing string at target locations and for positioning flagged
collars of
the tubulars a relative to at least some of the target locations;
16 Figure 12 is a flowchart illustrating a calibration operation for the
17 drawworks of Fig. 10 and for subsequent raising and lowering of the blocks
of
18 the drawworks for tripping apparatus into and out of the wellbore;
19 Figure 13 is a flowchart illustrating raising and lowering tubulars
using the drawworks system of Fig. 10 and for positioning collars of the
tubulars
21 at target locations relative to the rig and the wellbore;
22 Figures 14A-14C are side schematic views of a sandline system for
23 an embodiment according to Fig. 1, illustrating a control system for the
sandline
24 drum and sensors for providing feedback to a sandline PLC, more
particularly
6
CA 02607466 2007-10-23
1 Fig. 14A illustrates the sandline in a bottomhole position, a
2 sandline cable payed out from the sandline drum for positioning apparatus
3 connected thereto adjacent a bottom of a wellbore and illustrating a speed
4 profile related to an entire depth from the rig to the bottom of the
wellbore;
Fig. 14B illustrates the sandline of Fig.14A, the sandline
6 cable payed out from the sandline drum for positioning apparatus
7 connected thereto intermediate the weilbore; and
8 Fig. 14C illustrates the sandline system of Fig. 14A, the
9 sandline cable payed out from the sandline drum for positioning apparatus
connected thereto adjacent a wellhead at a top of the wellbore;
11 Figure 15 is a flowchart illustrating a process for running in or
12 tripping out a swabbing tool from a weilbore using the sandline system of
Figs
13 14A-14C;
14 Figure 16 is a schematic illustrating a propulsion system according
to an embodiment of the invention; and
16 Figure 17 is a schematic illustrating connection of a mud pump
17 system and, optionally, hotel loads to an embodiment of the invention
through
18 one or more electrical umbilicals.
19
7
CA 02607466 2007-10-23
1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
2 Having reference to Figs. 1A-5, a substantially electrically-powered
3 well service rig 10 comprises an integrated AC power system for powering
both
4 propulsion for a mobile service rig platform 12 and the apparatus used for
performing service operations. The well service rig 10 comprises a mast or
6 collapsible mast 14, and hoisting capability, such as a drawworks system 16,
7 sandline system 18 or both. The drawworks system 16 typically comprises
multi-
8 line blocks 20 supported from a crown 22 of the mast 14 which are raised and
9 lowered in the mast 14 using drawworks cable 24 wound about a drawworks
hoist drum 26. Elevators supported from the blocks 20 handle apparatus such
11 as lengths of tubing run into and tripped out of a well 28. The well
service rig 10
12 can further comprise the sandline system 18. The sandline system 18 is
raised
13 and lowered through the mast 14 using a sandline cable 30 extending over a
14 sheave 32 in the crown 22 and wound about a sandline drum 34. Downhole
apparatus or sandline tools such as a swabbing tool 36 are raised and lowered
16 through the wellbore 28 connected to the sandline system 18.
17 In an embodiment of the invention as shown in Figs. 1-5, and in
18 more detail, the service rig's mobile platform 12 comprises an
undercarriage 60
19 for transport as a self-propelled portable unit, typically in a truck-type
format. The
undercarriage 60 may comprise a variety of wheel/axle formats as required to
21 meet Department of Transport guidelines. Although not detailed in Fig. 3,
engine
22 50 and generator 54 are generally located over the platform's front wheels.
23 Having reference as well to Figs. 10-15, both the drawworks and
24 sandline systems 16, 18 are operated for maximizing speed of running in and
tripping out and for adjusting cable speeds when the moving apparatus reaches
8
CA 02607466 2007-10-23
1 point of interest or target locations. More particularly, with reference to
Figs
2 10,11 and 14A-14C, it is desirable to carefully control the drawworks and
3 sandline cable 24,30 speed at the extreme ranges of motion of the cables 24,
30
4 and at particular target locations in the well 28 or mast 14. As shown in
Fig. 10,
when running tubing 44, the passage of collars C through wellhead equipment
6 48, a rig floor 38, tubing tongs 40 and the crown 22 are examples of points
of
7 interest for each length of tubing. Further, arrival of an end 42 of the
tubing
8 string 44 of a plurality of lengths of tubing at a bottom of the well 46 can
be a
9 point of interest. As shown in Figs. 14A - 14C, for the sandline system 18,
points of interest are more related to the starting and stopping of the
sandline
11 tool 36, such as at the bottom of the well 46, at the wellhead equipment at
12 surface 48 and at the crown 22.
13 As shown on Fig. 6, an electrical power system 49 comprises at
14 least one diesel engine 50, such as a diesel generator engine from
CATERPILLAR TM, USA which runs an AC generator 52 for generating AC
16 electrical power. A plurality of variable frequency drives (VFDs) 54, under
the
17 control of programmable logic controllers (PLC's) 56, control a plurality
of motors
18 58 for propulsion of the service rig 10 for transporting the rig from
wellsite to
19 wellsite and for controlling the drawworks system 16 and the sandline
system 18
for raising and lowering apparatus into and out of the wellbore 28.
21 With refrence also to Figs. 1 B - 5 and 6, the power system 49,
22 including at least the diesel engine 50, the engine-driven generator 52 and
the
23 VFD's 54 and PLC's 56 as shown in Fig. 6, are mounted on the mobile
platform
24 12. The plurality of motors 58 are controlled by the VFD's 54. Permanent
magnet (PM) motors 58 are much lighter than conventional AC motors and their
9
CA 02607466 2007-10-23
1 use permits integration of the systems into the service rig 10 which is
2 transportable as a single mobile unit. For the same capability, a 1000 pound
PM
3 motor can replace a 6,000 to 10,000 pound induction motor. Further, PM
motors
4 58 do not slip and can therefore provide maximum torque at zero revolutions
to
very low rpm which is useful for manipulating heavy equipment or adjacent
target
6 locations. The no-slip PM motors 58 enhance the rig's ability to accurately
move
7 apparatus connected to the drawworks and sandline systems 16,18 at the
8 various points of interest. The use of PM motors 58 and implementing an
9 electrical propulsion system enables, for the first time, an electrical
service rig 10
and results in a considerable savings in weight of the mobile platform 12,
11 permitting transportability as a single mobile unit. In one embodiment, the
motors
12 58 are DC brushless motors available from POWERTEC Industrial Motors, Rock
13 Hill SC 29732, USA.
14 Also shown in Fig. 6, the braking capability of the lightweight PM
motors 58 for the drawworks and sandline drums 26, 34 are supplemented with
16 multi-disc wetted brakes 62. A series of friction discs and separator discs
are
17 alternately stacked and the stacked discs are splined alternately between
the
18 drum shafts and stationary brake housings. The disc stack is compressed via
19 springs or hydraulic pressure to actuate the brake. Wet multi-disc brakes
run in
fluid such as oil which dissipates the heat generated in use. A lightweight PM
21 motor with a multi-disc wetted brake is about 20 to 30% the weight of an
22 induction motor alone.
23 Having reference to Figs. 6, 7 and 16, a propulsion system 70
24 comprises a transmission VFD 72 controlling a PM propulsion motor 74
connected to a transmission 76. The transmission VFD 72 and propulsion motor
CA 02607466 2011-10-17
1 74 are controlled through a propulsion PLC 78 which is operatively connected
to
2 an operator control 80 for achieving required road speeds. The transmission
76
3 can be a semi-automatic or fully automatic manual transmission. Automated
4 shifting manual transmissions have a weight advantage over automatic
transmissions. Such transmissions incorporate transmission-specific controls
6 such as a transmission PLC 82 for coordinating with the propulsion motor 74
7 such as during shifting and with ABS systems during braking.
8 Generally, the propulsion PLC 78 receives a desired road speed
9 signal from the operator, such as through the operator control 80. The
propulsion PLC 78 communicates the desired road speed to the transmission
11 PLC 82 for management of transmission specific control, such as gear
selection
12 and motor speed output. Ultimately, the transmission VFD 72 receives motor
13 speed set points for operation of the propulsion motor 74. In one
embodiment,
14 the transmission PLC 82 returns the motor speed set point to the propulsion
PLC
78 for control of a propulsion VFD 84. The transmission PLC 82 and propulsion
16 PLC 78 act in concert to control shifting of the transmission in response
to
17 feedback from the operator.
18 In one embodiment, the transmission 76 has a plurality of gears to
19 permit maximum gradeability. An example of such a semi-automatic
transmission is an AS TronicTM transmission (trademark of ZF Friedrichshafen
21 AG, Germany) which implements a shift strategy using a non-synchronized
22 three-stepped basic transmission with a synchronized range and splitter
group
23 and 12 pneumatically controlled gear steps. In particular the AS Tronic TM
24 transmission already incorporates a sophisticated electronic interface
11
CA 02607466 2007-10-23
1 between the transmission 76, various power plant controllers, operator
2 accelerator 80, brake and ABS systems.
3 With reference to Figs. 3, 4 and 5, the mobile platform 12 of the
4 service rig 10 implements an electrical motor braking system 90 which, in
embodiments of the invention, comprises a hybrid braking system for combining
6 braking from the propulsion motor 74 with conventional braking, such as ABS
7 brakes. In embodiments of the invention, dynamic braking and regenerative
8 braking with electrical storage are implemented. When regenerative braking
is
9 not feasible, such as when the electrical storage such as capacitors is
fully
charged, dynamic braking utilizes a resistor bank 91 and cooling system 92 to
11 dissipate braking energy. The propulsion PLC 78 controls how much
12 regenerative or dynamic braking is applied to supplement transmission range
13 selection. The operator is typically provided with a selector switch which
has an
14 off, medium and high option and which is adaptive depending on the
propulsion
motor rpm. For example, as regenerative braking reaches maximum, the
16 transmission 76 will automatically shift gears to lessen the regenerative
or
17 dynamic braking load. Further, the conventional anti-lock braking systems
(ABS)
18 provide signals to the propulsion PLC 78 when the ABS braking systems are
19 operated.
The engine and generator 50,54 of the service rig 10 is capable of
21 incorporating all the power needs for onboard propulsion, drawworks 16,
22 sandline 18 and further, for off-platform needs, including a mud pump
system
23 100 and hotel loads.
24 Particularly advantageous is the ability to power the mud pump
system 100, which is necessarily separately transportable, having the mud pump
12
CA 02607466 2007-10-23
1 motor 102 and mud tanks 104. In an embodiment of the invention, the mobile
2 platform generator 52 also powers the mud pump motor 102. A power umbilical
3 108 or two, depending on the electrical cabling requirements, is releasably
4 coupled with the mobile platform 12. The mud system can utilize mud pumps
driven by an asynchronous induction motor 102 and instrumentation can be
6 directed back to the service rig 10 including mud levels, temperatures and
motor
7 temperatures. Mud pumps are typically positive displacement plunger pumps
8 and a stroke counter can enable calculation of the volume of mud being
pumped.
9 Power can also be provided through one or more umbilicals 108 for hotel
loads
106, such as lighting, heating and the like.
11 A simple hydraulic power takeoff (not shown) from the engine 50
12 can provide auxiliary hydraulic power for lubricators, for the drawworks
and
13 sandline systems, power tongs, mast raising and telescoping hydraulics,
leveling
14 jacks and deck winches.
The collapsible mast 14 is typically mounted at a rear 15 of the
16 platform 12 so as to be moveable between a lowered transport position over
the
17 rig's platform 12 and in a raised position, cantilevered over a wellhead
connected
18 to the wellbore 28 for performing a variety of servicing operations. The
mast 14
19 is generally tilted through one or more hydraulic rams connected between
the
mast 14 and the platform 12 and powered by a hydraulic pump.
21 In an embodiment of the invention, as shown in Figs. 6, 8 and 10-
22 13, the drawworks system 16 comprises a drawworks VFD 110, under the
23 control of a drawworks PLC 112, and a PM drawworks motor 114 operatively
24 connected to the drawworks hoist drum 26. The drawworks motor 112 is
connected to the drawworks hoist drum 26 through a drawworks drum shaft 116
13
CA 02607466 2007-10-23
1 and includes a gear reducer, typically a three-speed gearbox. The drawworks
2 hoist drum shaft 116 further includes an encoder 118 for providing position
3 information for the hoist cable 24. Additional instrumentation includes
gearbox
4 shift and brake controls and sensors for providing feedback regarding
drawworks
system health, including temperature.
6 Having reference to Figs. 9, 14A-14C and 15, the sandline system
7 18 comprises a sandline VFD 120, under the control of a sandline PLC 122 and
8 a PM sandline motor 122 operatively connected to the sandline drum 34. The
9 sandline motor 122 is connected to the sandline drum 34 through a sandline
drum shaft 124. The sandline drum shaft 124 includes an encoder 126 for
11 providing position information for the sandline cable 30. Additional
12 instrumentation includes brake controls and sensors for providing feedback
13 regarding sandline system health, including temperature.
14 In an embodiment of the invention, the mast crown 22 includes
encoders for additional position control of the drawworks and sandline cables
24,
16 30. As shown in Figs. 9 and 10, load sensor 130 enables adjustment for
17 drawworks cable 24 or sandline cable 30 stretch and provides online
calibration
18 to better determine proximity to points of interest. Sandline cable 30 is
19 particularly affected by load and stretch, largely due to the length of
cable 30
payed out. Parameters required by the sandline PLC 122 are a load and a
21 number of layers of sandline cable 30 on the sandline drum 34. The sandline
22 drum 34 typically has a fixed diameter and the length of sandline cable 30
23 wrapped about the first layer is readily calculated from the circumference
and the
24 rotation encoder 128. However, the drum's effective diameter changes, each
wrap or layer of cable 30 requiring adjustments in the length of cable 30
payed
14
CA 02607466 2007-10-23
1 out or reeled in per revolution of the drum 34. The cable diameter and the
2 calibration process from crown 22 to rig floor 38 is typically input to the
sandline
3 PLC 122.
4 As previously stated, the PM motors 58 are used for manipulating
heavy equipment and embodiments of the invention are particularly suited for
6 fine motor control for manipulating the apparatus adjacent points of
interest or
7 target locations. The target locations may or may not be on the service rig.
8 Typically the target locations are fixed and are relative to either the well
service
9 rig 10 or the wellbore 28. For example, the target locations relative to the
wellbore 28 may be the bottom of the wellbore 46, a wellhead or a lubricator
48
11 and the target locations relative to the rig 10 may be the rig floor 38,
power tongs
12 40, and crown position 22.
13 Additionally, conventional tubing logs are maintained to log the
14 running in and out of the production string to maintain a relationship
between a
distal end 42 of production string 44 and bottom 46 of wellbore 28 in the
overall
16 operating system. As the service rig 10 operates, tubing section lengths
are
17 tallied as they are run into and out of the wellbore 28 for comparison with
known
18 target locations, like the bottom 46 of the wellbore 28. The drawworks
PLC's 112
19 is typically programmed with the known target locations, such as the well
bottom
46, which may be derived from previous tubing tallies or well logging tools.
21 Further as shown in Figs. 11 and 14A-14C, flag locations F are
22 utilized to assist with running apparatus such as tubulars 44 or tools 36
into the
23 wellbore 28 and are typically locations on the particular tool itself. The
flag
24 locations F are not fixed relative to the wellbore 28 or the rig 10 and
move with
the apparatus. Examples of flag locations F are the plurality of collars C
between
CA 02607466 2007-10-23
1 tubulars in a tubing string 44 or a top end 35 and bottom end 37 of a
sandline
2 tool 36, such as a swabbing tool.
3 In embodiments of the invention, prior to performing a service on a
4 wellbore 28, a calibration is performed wherein calibration signals are sent
to
either or both of the drawworks PLC 112 and sandline PLC 122 as the apparatus
6 is manipulated by the operator to the various target locations T. The
calibration
7 signal is sent by a switch to indicate correspondence between the target
location
8 T, such as the rig floor 38 and a flag location F, such as the tubing collar
C,
9 when a tubing collar C is aligned at the rig floor 38.
In use, to minimize well servicing duration and cost, it is preferred
11 to operate the drawworks and sandline systems 16,18 at a maximum speed
12 whenever possible. However, the drawworks and sandline PLC's 112,122 act to
13 control the speed of the drawworks and sandline PM motors 114,124 for
14 reducing a maximum speed setpoint M to a slower speed when a flag location
F
is within a preset window distance of the target location T. In this way, the
PLC's
16 112,122 control the operation for ensuring the apparatus is not bottomed
out in
17 the wellbore 28, topped out in the crown 22 or pulled through wellhead
18 equipment 48 at speeds which may result in damage to any of the equipment.
As
19 shown in Fig. 14A, typically, the maximum speed setpoint M at which the
sandline cable 30 is run in or tripped out is much faster than that of the
21 drawworks blocks 20. In accordance with the faster speeds, an appropriate
22 window distance for the sandline system 18, such as about either the bottom
of
23 the wellbore 46 or wellhead equipment 48, may be as much as 60 feet. As
24 shown in Fig. 11, the drawworks cable 24 is run at slower speeds and
therefore
an appropriate window for the drawworks system 18, such as about the wellhead
16
CA 02607466 2007-10-23
1 equipment 48 or at the rig floor 38, power tongs 40 or crown 22, may be
about 2
2 feet. Speed of drawworks cable 24 deployment typically varies depending upon
3 the weight of the tubing string 44 attached thereto and may be, for example,
4 about 2 m/s for a 10,000 pound tubing string to about 1 m/s for tubing
strings
having a weight of about 100,000 pounds.
6 In embodiments of the invention, an operator utilizes a
7 conventional appearing control panel which includes both a drawworks speed
8 joystick and a sandline speed joystick. The drawworks and sandline PLC's
9 112,122 reduce the maximum speed setpoints by reducing the "gain" so that
operator joystick maximum is reduced at target locations T from the higher or
11 maximum speed setpoint used between target locations T. In other words, at
the
12 target locations T, the joystick maximum is set at the target location
maximum for
13 slowing the speed.
14 With reference to Fig. 10 and 14A, embodiments of the invention
utilize a number of conventional sensors to provide feedback to the PLC's 56
16 regarding a variety of operational parameters which assist with controlling
the rig
17 systems. Rotation of the driven shafts 114,126 of the drawworks hoist drum
26
18 and sandline drum 34 are monitored using motor encoders 118,128, typically
19 dual output shaft encoders and resolvers, for monitoring motor 114,124
current
draw, torque required to move the motor 114,124 and power utilized by the
21 motor 114,124. Feedback from the drawworks shaft encoder 118 coupled with
22 the no-slip PM motor 114 permits accuracy of about 1/8" of movement of a
23 heavy tubing string 44 using the multiline blocks 20.
24 Further as shown in Fig. 10, the drawworks deadline or block load
sensor 130 provides feedback to the drawworks PLC 112 regarding the load on
17
CA 02607466 2007-10-23
1 the drawworks system 16 for calculating alterations in tubing parameters,
such
2 as tubing stretch. Corrections to account for the alterations in tubing
parameters
3 can then be incorporated into the operational system, such as to adjust flag
4 locations F relative to the tubing string 44.
Further, as shown in Figs. 14A-14C, sandline sensors typically
6 comprise at least the sandline shaft encoder 128 for providing positioning
7 feedback to the sandline PLC 122 for determining positioning of apparatus,
such
8 as a swabbing tool 36, connected to the sandline cable 30 relative to the
fixed
9 target positions T and the flag positions F.
Dual output encoders are typically used to provide a redundancy in
11 the signal to the various PLC's 56. Two sets of internal electronics
provide the
12 redundancy and if, for some reason, the two signals do not agree, the PLC's
56
13 will automatically slow the speed of the driven drawworks or sandline
shafts
14 116,126 from the maximum speed to the slower target location maximum or
other minimum speed to permit verification of location. Further, resolvers may
be
16 added to the PM motors 58 as an additional redundancy to compare against
17 encoder feedback to ensure accurate positioning. Once the position has been
18 verified or the problem resolved, the PLC's 56 can then reset the speed to
the
19 maximum running speed.
Conventional switches can be used, as previously described, to
21 permit calibration of the correspondence between a fixed target location T
and a
22 flag location F. The switches may be used in isolation to signal to the
drawworks
23 or sandline PLC 112, 122 the location of the relative target and flag
positions T,F
24 or can be used in at least a pair, for example the floor location 38 and
the crown
location 22, for calculating drawworks or sandline cable 24,20 pay-out and
reel-
18
CA 02607466 2007-10-23
1 in distances for a particular drum. Additionally, cable diameter may be used
to
2 calculate variable correspondence between drum encoder 118,128 revolutions
3 and actual distances payed out or reeled in.
4 Having reference to Figs. 10, 12 and 13, the blocks 20 of the
drawworks system 16 are raised and lowered by the drawworks cable between
6 the rig floor 38, the power tongs 40 and the crown 22 of the rig 10 for
moving
7 sections of tubulars 44 of fixed length into and out of the wellbore 28.
Said
8 movement permits operators on the floor 38 of the rig 10 to make up the
sections
9 at the threaded collars C for running in or breaking out the sections at the
threaded collars C when tripping out.
11 Having reference to Fig. 12, at block 200, prior to running the
12 tubulars 44, the drawworks system 16 is first calibrated by moving the
13 drawworks blocks 20 to each target locations T, being at block 201 the rig
floor
14 38, at block 202 the power tongs 40 and at block 203, the crown 22. The
operator sets the location by pressing a switch and the location information
is
16 provided to the drawworks PLC 112 as previously described. The block 20
17 location is coordinated with the sections of tubulars 44 for locating
collars C.
18 Once the system has been calibrated, the tubing string can be run
19 in or tripped out. For ease of description, the process of running in is
described,
the process of tripping out being essentially a reverse operation. At block
204,
21 the drawworks maxmum speed setpoint M is set to run in the tubing at the
22 maximum block speed. At block 205, the operator controls the joystick to
run at
23 up to the maximum speed. At blocks 206 and 207, the drawworks PLC 112 is
24 aware of the tubing string tally and monitors the location of the blocks 20
and
flag locations F relative to the target locations T in the rig 10 through
feedback
19
CA 02607466 2007-10-23
1 from the encoders 118, 130. As the blocks 20 approach the target locations
Tat
2 block 206, the drawworks PLC 112 automatically reduces the gain on the
3 joystick at block 208 which reduces the setpoint M and slows the drawworks
4 speed to ensure safe passage of the flag location F. As the blocks 20 leave
the
target location T, at block 207, the drawworks PLC 112 sets the speed setpoint
6 M to the maximum block speed, as shown at block 204. The drawworks PLC 112
7 continues to operate at the maximum block speed until such time as the
blocks
8 20 approach another target location T.
9 As shown in Fig. 13, when running tubulars, flag positions F,
particularly the position of the tubing collars C, must be monitored to ensure
the
11 tubing collars C are not moved through the wellhead 48 at maximum speed.
The
12 drawworks PLC 112 is programmed with the average length of a tubular and
the
13 preset window distance so as to account for deviations in the length of the
14 tubulars between collars C. The encoders 118 on the drawworks hoist drum
shaft 116 and the drawworks motor 114 provide feedback to the drawworks PLC
16 112. The data is corrected for any cable and tubing stretch through
feedback
17 from the block load sensor 130 to determine more precise flag locations F,
in this
18 case the location of the collars C.
19 As shown at block 210, the drawworks PLC 112 sets the
drawworks at maximum speed. At block 211, the operator controls the joystick
to
21 run at the maximum speed during either running in or tripping out of the
tubulars
22 44, shown at block 212. At block 213, as the preset window distance
approaches
23 the target location T, the drawworks PLC 112 automatically reduces the
speed
24 setpoint M at block 214 from the maximum block speed by automatically
reducing the gain for the joystick and runs the drawworks at the reduced
target
CA 02607466 2007-10-23
1 maximum speed until the preset window distance has passed the target
location
2 T as shown at block 215. The drawworks PLC 112 then automatically increases
3 the running block speed setpoint again to the maximum block speed at block
210
4 until the next preset window distance approaches the target location T.
Having reference to Figs. 14A-14C and 15, in a sandline operation,
6 such as running in and tripping out a swabbing tool 36, target locations T
for
7 calibration, typically the rig floor 38 and the crown 22 are programmed into
the
8 sandline PCL 122, much like the drawworks 16, blocks 20 and tubing string 44
9 calibration. The operator presses a switch as the sandline cable 30 is
deployed
to each of the rig target positions 38, 22. An optional mid-mast position may
also
11 be used for the calibration. Operational target locations T of the service
rig 10,
12 such as the bottom of the wellbore 46 (Fig. 14A) and a top of the wellbore
or
13 wellhead 48 (Fig. 14C) are calculated and programmed into the sandline PLC
14 122. The sandline PLC 122 is also programmed with preset slowdown windows
of distance from the top of the wellbore or wellhead 48 and the bottom 46 of
the
16 wellbore 28.
17 For ease of description, tripping out of the swabbing tool 36 is
18 described, the running in being essentially a reverse operation. As shown
in Fig.
19 14A, as the sandline cable 30 is raised from the bottom 46 of the wellbore
28,
the sandline drum 34 is run at a set maximum speed. As the sandline-deployed
21 swabbing tool 36 approaches the preset window distance from the top of the
22 wellbore 48, the sandline PLC 122 automatically reduces the speed of the
23 sandline motor 124 and the sandline cable 30 and swabbing tool 36 are
raised
24 slowly to the surface to avoid pulling the swabbing tool 36 through the
wellhead
48 at maximum speed.
21
CA 02607466 2007-10-23
1 Having reference to Fig. 15 and for sandline system 1 operation, at
2 block 300 the sandline PLC 122 sets the sandline motor 124 speed setpoint M
at
3 a maximum running speed. At block 301, the operator controls the sandline
4 motor 124 through a joystick which is also set at maximum speed for running
a
swabbing tool 36 into or out of the wellbore 28 (Fig. 14B) at block 302. At
block
6 303 as the swabbing tool 36 approaches a target location T (Figs. 14A and
14C),
7 the sandline PLC 122, at block 304, reduces the maximum sandline speed to a
8 maximum target speed. At block 305, once the swabbing tool 36 leaves the
9 target location T, the sandline PLC 122, increases the speed setpoint M once
again to the maximum running speed (Fig. 14B).
22
