Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02541516 2006-03-31
DRILL STRING SYSTEM FOR PERFORMING MEASUREMENT WHILE
DRILLING AND LOGGING WHILE DRILLING OPERATIONS
Field of the Invention
[0001] The invention relates generally to the field of drilling and, more
particularly, to the field of "underbalanced" drilling systems.
Background of the Invention
[0002] Petroleum exploration activities occasionally require specialized
drilling techniques to optimise production from certain types of reservoir
stratum. One such drilling technique is known as "underbalanced" drilling,
which employs singly or a combination of nitrogen, carbon dioxide or other
inert gasses, and drilling mud as the primary composite drilling fluid. In
this
situation, downhoie pressure of the composite drilling fluid is monitored
within
the drill string bore and the well annulus, with the goal of preventing
formation
fracture due to overly high gas pressures. Another goal of underbalanced
drilling is to minimise loss of the composite drilling fluid to the formation,
which can be re-circulated until drilling is complete. As with all directional
drilling, the orientation of the drill string is monitored to determine the
actual
drilling path to permit correction where the actual drilling path has deviated
from the desired drilling path.
[0003] Such systems generally employ a tool disposed in the bore of
the drill string that is operable to both determine the pressure inside and
outside and the orientation of the drill string. The tool includes a three-
dimensional orientation sensor for determining the orientation of the tool. As
it is ultimately desired to determine the orientation of the drill string, the
tool is
secured in a fixed known position inside the driil string. The orientation of
the
drill string can thereafter be determined using the orientation information
reported by the tool to the surface. In current systems, the orientation of
the
tool relative to the drill string is maintained by retaining the tool in a
tool guide
at its upper end and seating the tool in a mule shoe at its lower end. The
tool
guide permits rotation and vertical travel of the tool. The mule shoe has a
helical groove into which the tool is fitted in order to limit vertical travel
of the
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tool and to maintain the tool in a known orientation relative to the drill
string.
Deployment of the muleshoe, however, is time-consuming and costly.
Summary of the Invention
[0004] In accordance with an aspect of the invention, there is provided
a drill string system for performing measurement while drilling and logging
while drilling operations for oil and gas drilling, said drill string system
comprising:
a drill string section having a bore defined by an inner length of
surface of a pipe wall which also has an outer surface;
a tool guide secured in said drill string section and a support for
centering said tool guide in said bore;
communication ports extending through said drill pipe wall from
said outer pipe surface to said inner surface and through said support to an
inner surface of said tool guide, said communication ports being in
communication with one another;
an elongate cylindrical tool disposed in said tool guide;
a first terminated passageway in said tool in communication with
a pressure sensor within said tool to sense said drill string annular
pressure;
a second terminated passageway in said tool in communication
with said drill string bore and in communication with a pressure sensor within
said tool to sense said drill string bore pressure;
a three-dimensional orientation sensor in said tool determining
orientation of the tool; and
an alignment mechanism provided by said tool and said tool
guide for inhibiting rotation of said tool relative to the tool guide when
said tool
is in a desired orientation relative to said tool guide, said first terminated
passageway being in communication with said communication port of said
tool guide when said tool is in said desired orientation.
[0005] The alignment mechanism can be an alignment key and a
corresponding key slot. The alignment key and key slot can extend
longitudinally along the tool guide and the tool. The alignment key can be at
least one biasable element and the alignment key can be tapered at a lower
longitudinal end thereof. The key slot can also be tapered at a lower
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longitudinal end thereof. The support can be a fit ring connected to the tool
guide via support legs extending longitudinally along the tool guide, the fit
ring
being fitted to the inner diameter of the drill string pipe. The drill string
system
can include ring seals above and below the communication port on the tool
guide.
[0006] The tool can comprise at least one spacer at a lower end
thereof for spacing the tool from the drill string pipe. The at least one
spacer
can be centralizer fins that extend generally radially from the tool. The tool
can include a feature to abut against the tool guide to limit vertical
movement
of the tool in the drill string pipe. The tool guide can be tubular.
[0007] In accordance with another aspect of the invention, there is
provided a drill string system for performing measurement while drilling and
logging while drilling operations for oil and gas drilling, said drill string
system
comprising:
a drill string section having a bore defined by an inner length of
surface of a pipe wall which also has an outer surface;
a tool guide secured in said drill string section and a support for
centering said tool guide in said bore;
communication ports extending through said drill pipe wall from
said outer pipe surface to said inner surface and through said support to an
inner surface of said tool guide, said communication ports being in
communication with one another;
an elongate cylindrical tool disposed in said tool guide;
a first pressure sensor within said tool to sense said drill string
annular pressure;
a second pressure sensor in said tool in communication with
said drill string bore to sense said drill string bore pressure;
a three-dimensional orientation sensor in said tool determining
orientation of the tool; and
a mechanical retention device connected to said tool guide for
inhibiting rotation of said tool relative to the tool guide when said tool is
in a
desired orientation relative to said tool guide, said first terminated
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passageway being in communication with said communication port of said
tool guide when said tool is in said desired orientation.
[0008] In accordance with a further aspect of the invention, there is
provided a landing assembly for use in a drill string section, said landing
sleeve assembly comprising:
a tool guide for receiving an elongate cylindrical tool;
a support for centering said tool guide in a bore of said drill
string section;
a communication port extending through said tool guide and
said support for communication with a corresponding communication port in
said drill string section and a pressure sensor in said tool when said landing
assembly is placed in said drill string section; and
a mechanical retention device connected to said tool guide and
said support for inhibiting rotation of said tool relative to the tool guide
when
said tool is in a desired orientation relative to said tool guide.
[0009] The drill string system and ianding assembly of the invention
facilitates and/or maintains correct rotational alignment of a pressure
measurement and orientation tool within a drill string bore.
Brief Description of the Drawings
[0010] A preferred embodiment of the invention is described with
respect to the drawings wherein:
Figure 1 is a schematic diagram of a downhole drill string;
Figure 2a is a sectional view of the lower end of the drill string;
Figure 2b is a schematic diagram of the geometry of the drill
string;
Figure 3 is a sectional view of a drill string system of this
invention;
Figure 4 is an exploded sectional view of the drill string system
of Figure 3;
Figure 5 is another exploded view of the drill string system of
Figure 3; and
Figure 6 is a sectional view of a drill string section with a landing
shoe assembly placed therein.
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Detailed Description of the Preferred Embodiments
[0011] A representative drilling system is shown in Figures 1 and 2a.
The above ground drilling structure 10 has the usual tower 11 with drill
string
assembly and drive components 12. The drill string 13 is made up of
individual drill string sections 14. The lowest drill string section is
coupled to a
collar 15, a bent subassembly 16, and a mud motor in unit 17 for driving a
drill
bit 18. The drilling structure 10 operates in a bore 19 in the earth formation
created by the downward movement of the drill bit 18. The space around the
drill string 13 within the bore 19 is referred to as an annular space 20. The
drilling structure is capable of performing directional drilling via the drill
bit 18
that is angled via the bent subassembly 16.
[0012] Figure 2b illustrates various axes corresponding to the
orientation of the drill string system. The vector representing the axis of
the
lower end of the drill string 13 is identified as ADS. The vector representing
the axis of the drill bit is identified as ADB. The vector ADB has a component
that is coaxial to ADS, namelyAD , and a component that is normal to ADS,
namelyA ~. A vector, VHS, is defined as being the polar opposite of A 8. This
vector represents the "highside" of the drill string 13 as indicated on Figure
2a. In order to cause the drill bit 18 to "steer" away from the highside
direction, downward pressure is applied to the drill string 13, causing the
drill
bit 18 to deviate direction.
[0013] In order to clear away materials from the drill bore 19, a drilling
fluid is pumped downwards through a bore in the drill string 13. The drilling
fluid exits the drill string 13 adjacent the drill bit 18 and flows upwards
within
the annular space 20 about the periphery of the drill string 13. Differences
between the drill string bore pressure and drill string annular pressure can
result in fractures in the drill string 13. In order to monitor these
pressures,
the drill string 13 is provided with electronic components that are used to
provide for "measurement while drilling and logging while drilling
operations".
[0014] A drill string system 24 in accordance with an embodiment of
the invention shown in Figure 3. The system 24 enables alignment of the
electronic components in a fixed orientation within a specialized downhole
drill string segment referred to as a landing sleeve 28. An upper female
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connector 32 of the landing sleeve 28 is connected to a male threaded
connector of an upper drill string section. Correspondingly, a lower male
connector 36 of the landing sleeve 28 is threaded into the collar 15. The
electronic components for measurement while drilling, logging while drilling
and the determination of orientation are housed in an elongate cylindrical
tool
40. The tool 40 is positioned within a landing shoe assembly 44 that is fitted
within the landing sleeve 28. A tapered sleeve insert 48 is disposed above
the landing shoe assembly 44 in the landing sleeve 28 and a seal ring 52 is
placed atop the tapered sleeve insert 48. Centralizer fins 56 project
generally
radially from a lower end 60 of the tool 40 to fix the lower end 60 of the
tool
40 in a coaxial relation within the landing sleeve 28. The centralizer fins 56
permit flow of drill fluid thereby. A toothed crown 64 is secured to an upper
end of the tool 40 and allows a rotational force to be applied to the tool 40
in
order to rotate.it when it is disposed within the landing sleeve 28.
[0015] The cylindrical tool 40 contains a multitude of electrical
opponents therein, including devices for measuring drilling fluid pressure in
a
bore 68 of the drill string and the drill string annular pressure in the
annular
space 20. The annular space 20 is defined between earth formations and an
exterior 76 of the landing sleeve 28. A pressure transducer 80 is provided to
measure the pressure of a circulating drilling fluid in the drill string bore
68. A
port 104 in the tool 40 communicates with a passageway 108, and terminates
at the pressure transducer 80. The pressure in the annular space 20
surrounding the drill string is measured by a pressure transducer 92. The
pressure transducer 92 is in communication with a passageway 96 which, in
turn, communicates through a port 100. In turn, port 100 is in communication
with a port 104 through the landing shoe assembly 44 and ultimately with a
passageway 108 in the landing sleeve 28. The external entrance of the port
104 is located within a recessed region 106 on the periphery of the landing
shoe assembly 44. The passageway 108 has a removable plug 112 inserted
therein that fits into the recessed region 106 of the landing shoe assembly 44
to fix movement of the landing shoe assembly 44 relative to the landing
sleeve 28. The removable plug 112 has a port 116 that communicates with
the annular space 20, noted as the drill string annular space 20 that conveys
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returned drilling fluid to the surface. As a result, the pressurized fluid in
the
annular space 20 outside of the landing sleeve 28 can communicate static
pressure through ports 116, 104 and 100 and through passageway 96 to the
pressure transducer 92.
[0016] Port 104 is located on a side of the tool 40 opposite port 100
and is in communication with the pressurized fluid within the bore of the
drill
string. Port 100 is located between seals generally designated as 120 and
124. The cylindrical tool 40 is of-a dimension that readily slides through the
bore of landing shoe assembly 44. Seals 120 and 124 project slightly from
the periphery of the tool and form an interference fit with the interior
surface
128 of the landing shoe assembiy 44, the resulting seal deformation providing
a liquid tight seal with the interior of the landing shoe assembly 44. As a
result, the seals 120 and 124 prevent the fluid from the drill string bore 68,
which is at a higher pressure than the fluid in the annular space 20, from
leaking into the annular space formed between the seals 120 and 124, the
tool 40 and landing shoe assembly 44.
[0017] A third seal 132 similar to seals 120, 124 is provided to stabilize
lateral movement of the tool 40 within the landing shoe assembly 44.
Although, in accordance with this embodiment, the seals are provided in the
tool 40, it is appreciated that the seals may be provided on the inner surface
128 of the landing shoe assembly 44 to provide a sealed space when the tool
40 is inserted into the landing shoe assembly 44.
[0018] The landing shoe assembly 44 includes an outer fit ring 136
attached to an upper end of a tool guide 140 by three legs 144. The tool
guide 140 can be any shape that permits axiai and rotational movement of
the tool 40 while retaining the tool coaxially relative to the landing sleeve
28.
The outer fit ring 136 and the tool guide 140 are coaxially aligned. The legs
144 radially extend from the tool guide 140 to the outer fit ring 136 to space
the outer periphery of the tool guide 140 from the interior surface of the
landing sleeve 28. Three arcuate channels 152 are defined by the legs 144
between the outer fit ring 136 and the tool guide 140. The arcuate channels
152 allow the pressurized drilling fluid in the drill string bore 68 to flow
through
the spaces defined between the periphery of the tool guide 140 and the
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interior of the landing sleeve 28. Seals 156, 160 are seal rings that project
slightly from the outer periphery of landing shoe assembly. Seals 156, 160
are seal rings that project slightly from the outer periphery of the landing
shoe
assembly 44.
[0019] The tool 40 also includes a three-dimensional orientation sensor
162 for determining its orientation. Various types of three-dimensional
orientation sensor known to those skilled in the art can be employed. In the
described embodiment, the three-dimensional orientation sensor is a three-
dimensional compass.
[0020] In order to determine the direction of the drilling being
performed, the orientation of the lower end of the drill string is used to
gauge
along what path the drilling is headed. In particular, the orientation of the
landing sleeve 28 is used. As the orientation of the tool 40 can be
determined, the tool 40 is fixed in a known orientation inside the Ianding
sleeve 28. This is achieved primarily by an alignment mechanism provided by
the tool 40 and the tool guide 140.
[0021] The electrical components of the tool 40 communicate the drill
string bore and annulus pressures and orientation to the surface via
telemetry, such as Mud Pulse Telemetry or Electro-Magnetic Telemetry.
[0022] The alignment mechanism includes an alignment key 164
located on a lower end of the tool guide 140. The alignment key 164 is slip-
fitted into a vertically-extending machined aperture 168 in an extension of
one
of legs 144 along the lower end of the tool guide 140. A pair of bolts 170
secures the alignment key 164 to the tool guide 140. The alignment key 164
includes alignment elements 172 that are spring-biased towards the axis of
the tool guide 140. The alignment elements 172 form a projection 176 that is
tapered at its longitudinal ends.
[0023] In addition, the alignment mechanism includes a vertical key slot
180 machined into the outer surface of the tool 40 directly below and radially
aligned with the port 100. The key slot 180 has dimensions that are
complementary to the projection 176 of the alignment key 164. In particular,
the key slot 180 has a tapered upper end 184, that transitions to a flat
recess
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188 and a tapered lower end 192, providing a valley-like vertical profile.
Lateral sides 196, 200 of the key slot 180 are not tapered.
[0024] A shoulder 204 of the tool above seal 120 is set in a machined
annular recess 208 on the inner surface 128 of the tool guide 44.
[0025] The exterior passageway 108 extends through the wall of the
landing sleeve 28. The passageway 108 communicates with the port 104
which extends through the leg 144 of the landing shoe assembly 44 via a
space defined between the exterior surface of the inner surface 148 of the
landing sleeve 28 and the outer surface of the outer fit ring 136 of the
landing
shoe assembly 44. There is a slight gap between the inner surface 148 of the
landing sleeve 28 and the outer surface of the landing shoe assembly 44 to
permit insertion of the landing shoe assembly 44 in the landing sleeve 28.
This space is sealed off to each side of the port 100 by seals 156 and 160,
which form a liquid tight seal with the inner surface 148 of the landing
sleeve
28 to inhibit fluid from the bore 68 of the landing sleeve 28 from entering
port
104 or passageway 108. This ensures that all pressurized fluids passing
through passageway 108 and port 104 are contained within the annular
space. The port 104 opens up into the space defined between the exterior
surface of the cylindrical tool 40 and the inner surface 128 of the landing
shoe
assembly 44. There is a slight gap between the cylindrical tool 40 and the
inner surface 128 of the landing shoe assembly 44 to permit insertion and
retraction of the cylindrical tool 40. This space is sealed off to each side
of
the port 104 by seals 120 and 124. This ensures that all pressurized fluids
passing through passageway 108 and port 104 are contained within the
annular space. Port 100 is in communication with the annular space so that
any pressurized fluid in the annular space enters port 100 and travels along
passage 96. As a result, the pressure of such fluid is sensed by the pressure
transducer 92.
[0026] When the drilling system 24 is being assembled at the surface,
the landing shoe assembly 44 is fitted into the landing sleeve 28. The
recessed region 106 is aligned with the passageway 108 and the plug 112 is
inserted into the passageway 108. When fully inserted, the plug 112 projects
into the recessed region 106 which is dimensioned to inhibit movement of the
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landing sleeve assembly 44 when the plug 112 is inserted. The tapered
sleeve insert 48 is inserted into the landing sleeve 28 after insertion of the
landing shoe assembly 44, and the seal ring 52 is placed atop the tapered
sleeve insert 48. The tool 40 is then inserted into the bore of the landing
sleeve 28 through the landing shoe assembly 44 until the shoulder 204 of the
tool 40 abuts against the machined annular recess 208 of the landing shoe
assembly 44. The shape of the tapered sleeve insert 48 guides insertion of
the cylindrical tool 40 into the landing shoe assembly 44 during assembly.
[0027] The tapered sleeve insert 48 and seal ring 52 are retained in
place by connection of a drill string section to landing sleeve 28. The seal
ring 52 is compressed between the tapered sleeve insert 48 and the end of
the male connector 36 of the connecting drill string section, thereby creating
a
liquid tight seal between the bore of the landing sleeve 28 and that of the
connecting drill string section. An apertured bracket is secured over the
toothed crown and limits upward movement of the tool 40.
[0028] In order to fix the orientation of the tool 40 within the landing
sleeve 28, the tool 40 is rotated via a rotary drive coupled to the toothed
crown 64 until the alignment key 164 is radially aligned with the key slot 180
of the tool 40. In this position, the projection 176 then moves freely into
the
key slot 180. Upon biasing of the projection 176 of the alignment key 164 into
the key slot 180, abutment of the projection 176 with the side walls 196, 200
inhibits further rotation of the tool 40 in either direction. As the tool
guide 140
and the centralizer fins 56 maintain the upper and lower ends of the tool 40
coaxial to the landing sleeve 28, and the alignment mechanism inhibits
rotation of the tool 40, the tool 40 is held in a fixed known orientation
relative
to the landing sleeve 28. Thus, the orientation of the landing sleeve 28 can
be determined from the orientation of the tool 40.
[0029] Thereafter, further sections of the drill string 13 are appended
atop the landing sleeve 28 to construct the drill string 13.
[0030] In this manner a reliable economical system is provided which
permits securement of a tool having a three-dimensional orientation sensor
inside the drill string in a fixed known orientation relative thereto.
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[0031] Although preferred embodiments of the invention have been
described herein in detail, it wili be understood by those skilled in the art
that
variations may be made thereto without departing from the spirit of the
invention or the scope of the appended claims.
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