Note: Descriptions are shown in the official language in which they were submitted.
CA 02316467 2000-08-16
DYNAMIC PRESSURE DEVICE FOR OIL DRILL SYSTEMS
Field of the Invention
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, down hole 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 gays 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. Clearly, a specialized
drilling
device is needed to measure the drill string and well bore pressures to make
underbalanced drilling possible.
Backqround of the Invention
Although there are a variety of devices for measuring downhole drilling
fluid pressure, some of the devices require a temporary cessation of drilling
operations, which in some cases incur cost and time delays unacceptable to
drilling operators in the competitive exploration market. Such a system is
described in Canadian Patent 607,352. Other types of systems allow
downhole pressure measurement while drilling, generally making use of
electronic pressure measurement tools rigidly fixed to the lower portion of
the
drill string, near the drill bit. While satisfactory for this service, such
devices
are irrecoverable in the event that this section of the drill string becomes
stuck
downhole, and consequently abandoned if efforts to free it are unsuccessful.
Typically the drill string above the stuck section is disconnected in some
fashion and brought to the surface, leaving behind the drill motor, drill bit,
pressure measurement tools and the lower section of the drill string.
Examples of such systems are described in U.S. Patents 4,297,880 and
4,805,449, which are capable of sensing drill bore and annulus pressure, but
as mentioned are irrecoverable in the event of drill string abandonment due to
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their mechanical design.
There is a significant need for an electronic downhole system that
measures pressure in the drill string bore and the well annulus (the area
between the collar OD and the well bore), that is retrievable and re-seatable,
and reports pressure measurements to the surface in a timely fashion. Such
a system permits drillers to make real-time decisions on how to proceed with
the drilling operation based upon this and other information. The value of
such a device is greatly enhanced by providing retrieval and resenting
capabilities. Retrieval permits the recovery of the device in situations where
the drill string becomes stuck and must be abandoned. However, certain
situations arise where the tool must be recovered temporarily and then
returned to the end of the drill string so that the drilling job may be
continued.
This is known as re-seating, and offers a level of operational flexibility not
observed in the general market for similar devices.
Summary of the Invention
The Dynamic Pressure Device (DPD), in accordance with an aspect of
this invention measures pressure in the drill string bore and the well annulus
(the area between the collar OD and the well bore) and reports the
measurement to a transmitter located within the tool string. The transmitter
communicates this information to the surface, where drillers make decisions
on how to proceed with the drilling operation based upon this and other
information.
In accordance with another aspect of the invention a drill string section
for use in making up a drill string for oil and gas drilling is provided. The
drill
section carries instrumentation for Measurement While Drilling and Logging
While Drilling operations, said instrumentation including a Dynamic Pressure
Device for measuring drill string bore pressure of incoming pressurized
drilling
fluid, and drill string annular pressure of returned pressurized drilling
fluid,
said instrumentation being retrievable from said drill string when said drill
string section is stuck or otherwise abandoned downhole, or otherwise
reseatable into said drill string as required when drill string is deemed
operational and fit for continued drilling. The drill string section
comprises:
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i) a length of drill string pipe having a bore defined by an inner
surface of a pipe wall which has an outer surface,
ii) a cylindrical landing sleeve and a support for centering said
sleeve in said pipe bore,
iii) communicating ports extending through said drill pipe wall from
said outer pipe surface to said inner surface and through said support to an
inside surface of said landing sleeve,
iv) said instrumentation being provided in an elongate cylindrical
tool shell, spaced apart seals which engage said inside surface of said
landing sleeve and the outer surface of said tool shell, means for locating
said
communicating ports between said spaced-apart seals,
v) said instrumentation in said tool shell having a first terminated
passageway in said tool shell between said seals which communicates with a
pressure sensor within said shell to sense thereby said drill string annular
pressure,
vi) said instrumentation having a second terminated passageway in
said tool shell in communication with said drill string bore and in
communication with a pressure sensor within said shell whereby said drill
string bore pressure is sensed.
Brief Description of the Drawings
Preferred embodiments of the invention are described with respect to
the drawings wherein.
Figure 1 is a schematic of the abandonment of a downhole drill string.
Figure 2 is a section through the drill string of this invention.
Figure 3 is an exploded view of the drill section Figure 2.
Figures 4, 5, 6 and 7 show embodiments of the invention where the
pressure sensor system and related electronics can be withdrawn from the
drill string when it is necessary to abandon the drill string, or alternately
re-
seated when required.
Figure 8 is an exploded view of an alternative embodiment for the
mounting of the pressure measurement system in the drill string.
Figure 9 is a section through the assembly of Figure 8.
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Figure 10 shows yet another alternative embodiment for the mounting
of the pressure measurement device within the drill string.
Detailed Description of the Preferred Embodiments
A representative drilling system is shown in Figure 1. The above
ground drilling structure 10 has the usual tower 12 with drill string assembly
and drive components 14. The drill string 16 is made up of individual drill
string sections 18, the lower most of which includes a drill bit 20. For a
variety of reasons it may be necessary to abandon the downhole drill string
particularly the drill string adjacent the drill bit due to the drill bit
becoming
stuck or otherwise seized in the formation. The abandonment of the lower
most drill string can be costly because of the value of the electronic
components in the tool sub-assembly which are used to provide for
"measurement while drilling and logging while drilling operations". In other
cases, the tool itself may fail and requires replacement. In these situations,
the replaced tool must be lowered down the drill string and re-seated at its
original location so that drilling operations may resume. It is understood of
course that when the drill bit 20 is abandoned the operator may commence
redrilling of the bore and provide for an alternate route around the abandoned
drill section as indicated by the dotted lines 22. A number of contemporary
systems provide for retrieval or re-seating of the electronics in
circumstances
of drill string abandonment or tool replacement, however such systems are
not intended or otherwise designed for measuring drill string bore pressure
and drill string annular pressure.
In accordance with this invention, the system shown in Figure 2
provides for pressure measurements and at the same time allows retrieval
and re-seating of the electronic components from, and into, the downhole drill
section. The upper female connector 24 of the drill string section is
connected to a male threaded connector 26 of an upper drill string section.
Correspondingly the male section 28 is threaded into a female section 30 of
the lower drill string 18. The electronic components for measurement while
drilling and logging while drilling are housed in an elongate cylindrical tool
shell 32.
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The cylindrical tool shell is positioned within a landing sleeve 34. The
cylindrical tool shell may be removed from, or installed into, the landing
sleeve in the manner discussed with respect to Figures 4 through 7 by
grasping a connector stub 36 which is secured to the cylindrical tool shell. A
suitable latching mechanism 37 is provided in the drill string to releasably
secure the tool shell in the drill string and locate it in the drill string.
Although
there are a multitude of electrical opponents within the cylindrical tool
shell,
the specific components of interest in respect to the invention are the
devices
for measuring drilling fluid pressure in the bore 38 of the tool string and
drill
string annular pressure in annulus 40. The annulus 40 is defined between
the earth formation 42 and the exterior 44 of the drill string section.
Pressure
transducer 46 is provided to measure the pressure of a circulating drilling
fluid
in the drill string bore 38. A port 48 in the cylindrical tool shell
communicates
with a passageway 50, and terminates at the sensor 46. Drill string annular
pressure is measured by pressure transducer 52. Pressure sensor 52 is in
communication with passageway 54, which in turn communicates through an
annular passage formed between the tool barrel and the inside diameter of
landing sleeve 34 and ultimately through passageway 56. Passageway 56
communicates with annular space 40, noted as the drill string annular region
that conveys returned drilling fluid to the surface.
Further details of the system are shown in the exploded view of Figure
3. The elongate cylindrical tool shell 32 has the respective ports 48 and 58
on the periphery 60 of the shell 32. Port 48 is in communication with the
pressurized fluid within the bore of the drill string section. Port 58 is
located
between seals generally designated 62 and 64. The cylindrical tool shell 32 is
of a dimension that readily slides through the bare of landing sleeve 34.
Seals 62 and 64 project slightly from the periphery 60 of the tool shell and
form an interference fit with the interior surface 63 of the landing sleeve,
the
resulting seal deformation providing a liquid tight seal with the interior of
the
landing sleeve. Although in accordance with this embodiment, the seals are
provided in the tool shell, it is appreciated that the seals may be provided
in
the interior surface 62 of the landing sleeve to provide a sealed space when
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the tool shell is inserted into the landing sleeve. The landing sleeve 34
includes supports in the form of legs 65, in accordance with this embodiment,
to space the outer periphery 66 of the landing sleeve from the interior
surface
68 of the drill string section 18. This allows the drilling fluid to flow
through
the spaces defined between the periphery of the landing sleeve and the
interior of the drill string section. The landing sleeve 34 is secured within
the
drill string section in accordance with the embodiments to be discussed with
respect to Figures 4 through 7. In addition the leg 65 includes a port 70
which extends through the leg and the wall section 72 of the landing sleeve.
The port 70 is in communication with a port 74 defined within removable plug
76. The landing sleeve is of course fitted to the drill string section before
the
drill string section is put into use. When the tool shell is inserted in the
landing sleeve, a suitable stop, such as the latch 37, is provided to locate
the
seals 62 and 64 on opposite sides of the port 70 so that the pressurized fluid
in the annulus outside of the drill string section may flow through ports 74,
70
and 58 and through passageway 54 to the pressure transducer 52. Seals 62
and 64 also prevent the fluid from the drill string bore, which is at a higher
pressure than the annulus fluid, from leaking into the annular space 92
formed between the seals, tool barrel 32 and landing sleeve bore.
Figures 4, 5 and 6 demonstrate the manner in which the cylindrical tool
shell may be extracted from the drill string section 18. On the interior
surface
68 of the drill string, cams 78 are mounted on drill string interior to guide
insertion of the cylindrical tool shell into the landing sleeve 34 during a
seating
or re-seating operation. The landing sleeve 34 has its leg portions 65
secured in the drill string wall 82 by way of bolts 84 which are threaded into
the respective legs 65 in threaded bores 86. The pressurized drilling fluid in
the drill string bore flows over the tubular sleeve by way of a space defined
between the interior 68 and the exterior 66 of the landing sleeve.
The extraction tool 80 is shown in Figure 5 as having clamped onto the
connector stub 36. Extraction device 80 is connected to a wire line or the
like
88. With the extraction device clipped on to the stub 36 , the tool shell 32
may be pulled from the landing sleeve in the manner shown in Figure 6 where
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the tubular shell is moving in the direction of arrow 90. In this manner, the
valuable electronic components in the cylindrical tool shell may be recovered
before the drill string and drill bit are abandoned. Similarly, the
cylindrical tool
shell may be re-installed if the drill string and drill bit are restored to
service or
the electronics require servicing.
With reference to Figure 7 the relative relationship of the exterior bore
74 to the interior bore 58 is shown. The exterior bore 74 extends through the
wall 82 of the drill string section. The bore 74 communicates with bore 70
which extends through the leg 65 of the landing sleeve 34. The bore opens
up into the space defined between the exterior surface 60 of the cylindrical
tool shell and the interior surface 63 of the landing sleeve. As previously
explained there is a slight gap between the cylindrical tool shell and the
interior of the landing sleeve to permit insertion and retraction of the
cylindrical tool shell. This space is sealed off to each side of the port 70
by
seals 62 and 64. This ensures that all pressurized fluids passing through
bores 74 and 70 are contained within the annular space 92. Port 58 is in
communication with the annular space 92 so that any pressurized fluid in
space 92 enters port 58 and along passage 54 thereby the pressure of such
fluid is sensed by the pressure transducer 52. In this manner a reliable
economical system is provided which permits measurement of drill string
annular pressure while at the same time permitting extraction of the
cylindrical
tool shell.
An alternative embodiment for the drill string section is shown in Figure
8. The construction of the cylindrical tool shell 32 is essentially the same
with
the spaced apart seals 62 and 64. A slight recess 94 is provided for port 58.
The landing sleeve 34 is replaced with an alternative embodiment 96 which is
fixed on the interior surface 68 of the drill string section 18 by use of clip
rings
to be described in more detail with respect to Figure 9. The port 70 in the
landing sleeve 96 is longitudinally aligned with the port 74 of plug 76 which
can be achieved during assembly, however radial orientation of port 70 with
respect to port 74 is unimportant. With reference to Figure 9 the landing
sleeve 96 is secured inside the tubular string wall 82 by way of C-clips 98
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which engage the faces 93 and 95 of landing sleeve 96. The C-clips
interconnect with groves 100 and 102 in the drill string section wall. This
arrangement permits the installation of the C-clips so that they can bear up
against the upstream and downstream faces 93 and 95 of landing sleeve 96.
In accordance with this preferred embodiment the cylindrical tool shell
32 has a ledge 104 which defines a stop and which abuts the upstream face
93 of the landing sleeve. Alternatively, the tool shell 32 may be located by
other mechanical stops incorporated on the tool similar to other embodiments
of the invention. The landing sleeve includes seals 104 to seal the exterior
of
the landing sleeve within the interior 68 of the drill string section. In
addition
to or as a replacement for the preferred embodiment showing seals 62 and 64
on the cylindrical tool shell, the landing sleeve may include seals 106 which
seal to the exterior 108 of the cylindrical tool shell to ensure a leak tight
connection. The port 74 which extends through the wall of the drill string
section is aligned longitudinally, but not necessarily radially, with port 70
and
leads into annular space 110. Port 58 leads from pressure transducer 52 and
opens into annular space 110, permitting a reading of drilling fluid annular
pressure to be made. Multiple arcuate apertures 112 provide open channels
for the flow of drilling fluid along the drill string bore. In a manner
discussed
with respect to Figure 2, pressure transducer 46 communicates with port 48
through passageway 50 permitting a pressure measurement of the drill string
bore fluid to be made.
With reference to Figure 10, an alternative embodiment for the landing
sleeve is shown. In this embodiment the landing sleeve is integral with the
drill string section 18 and its wall section 82. The landing sleeve 114 is
machined as part of the drill string bore during the fabrication process. The
landing sleeve wall 116 is spaced from the interior wall 118 of the drill
string
by circumferentially arranged legs 120. The landing sleeve 114 has arcuate
shaped channels 122 which extend through the landing sleeve 114 and
provide the necessary flow paths for the pressurized drilling fluid. The
landing sleeve 114 has the port 124 extending from the exterior of the drill
string section through the wall 82 through the leg 120 and through the wall
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116 of the sleeve. The cylindrical tool shell 32 may be constructed in the
same manner as that of Figure 3 so that the seals 62 and 64 are positioned to
each side of the port 124. This provides, as discussed with respect to the
prior embodiments, for the usual communication of pressurized drilling fluid
on the exterior of the drill section to within the system for measurement by
the
pressure transducer 52.
Accordingly, various embodiments are provided which demonstrate the
effectiveness of a landing sleeve in providing for annular pressure
measurements of drilling fluid, and at the same time providing for a
retraction
or re-seating of the cylindrical tool shell while the drill string is down
hole.
Although preferred embodiments of the invention have been described
herein in detail, it will 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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