U.S. patent application number 10/345196 was filed with the patent office on 2003-07-24 for shaped element for rotary drilling equipment, and a drillrod including at least one shaped element.
This patent application is currently assigned to S.M.F. INTERNATIONAL. Invention is credited to Boulet, Jean Gilbert.
Application Number | 20030136587 10/345196 |
Document ID | / |
Family ID | 8871356 |
Filed Date | 2003-07-24 |
United States Patent
Application |
20030136587 |
Kind Code |
A1 |
Boulet, Jean Gilbert |
July 24, 2003 |
Shaped element for rotary drilling equipment, and a drillrod
including at least one shaped element
Abstract
The shaped element has at least one stirring and entrainment
zone in which the outside surface of the shaped element has
recessed portions and projecting portions configured substantially
in the form of helices about the axis of rotation of the drillrod,
said portions being wound in a direction such as to encourage the
flow of a drilling fluid in the upward direction in an annular
space between the drillrod and the wall of a borehole under the
effect of the drillrod rotating. The angle of inclination of the
helices in which the recessed portions and the projecting portions
of the shaped element are configured increases in the flow
direction of the drilling fluid in the annular space.
Inventors: |
Boulet, Jean Gilbert;
(Paris, FR) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
S.M.F. INTERNATIONAL
|
Family ID: |
8871356 |
Appl. No.: |
10/345196 |
Filed: |
January 16, 2003 |
Current U.S.
Class: |
175/323 |
Current CPC
Class: |
E21B 17/22 20130101;
E21B 17/10 20130101 |
Class at
Publication: |
175/323 |
International
Class: |
E21B 010/44 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 18, 2002 |
FR |
02 00 648 |
Claims
What is claimed is:
1/ A shaped element for rotary drilling equipment such as a
drillrod, the element being generally in the form of a body of
revolution of axis coinciding with the drilling axis of rotation
and having an outside surface with projecting portions and recessed
portions extending in radial directions perpendicular to the axis
in configurations that are substantially helical about the axis of
the shaped element so as to produce an effect of controlled
stirring and accelerated rise of a drilling fluid with cuttings in
an annular space between the shaped element of the drilling
equipment and the wall of a borehole while the drilling equipment
is rotating, wherein each helix along which the projecting portions
and the recessed portions of the shaped element are disposed has an
angle of inclination relative to a plane perpendicular to the axis
of the shaped element that increases in the axial flow direction of
the drilling fluid in the annular space, i.e. upwards when the
drilling equipment is in its operating position, the axial flow of
the drilling fluid being accelerated along the projecting portions
and the recessed portions because of the direction of rotation of
the drillrod.
2/ A shaped element according to claim 1, wherein, in the flow
direction of the drilling fluid in the annular space, the recessed
portions of the shaped element constituted by grooves present a
decrease in at least one of width in a circumferential direction of
the shaped element and depth in a radial direction perpendicular to
the axis of the shaped element, and thus present a decrease in
cross-section in a plane perpendicular to the axis of the shaped
element.
3/ A shaped element according to claim 1, further comprising, on
either side in the axial direction of a stirring and entrainment
zone in which the shaped element presents projecting portions and
recessed portions disposed in helices, a pre-loading zone in which
the drillrod presents a portion projecting radially outwards, and a
bearing zone in which the drillrod also presents a portion
projecting radially outwards with a maximum diameter greater than
the maximum diameter of the shaped element in the stirring and
entrainment zone and greater than the nominal diameter of the
drillrod in its ordinary portions disposed on either side in the
axial direction of the shaped element.
4/ A shaped element according to claim 1, including a second
loading zone or post-loading zone analogous to the pre-loading
zone, said second loading zone being situated downstream from the
bearing zone in the flow direction of the drilling fluid in the
annular space.
5/ A shaped element according to claim 3, further comprising, on
either side of the pre-loading zone disposed upstream of the
stirring and entrainment zone in the flow direction of the drilling
fluid in the annular space, a prior stirring and entrainment zone
situated upstream and a turbulence zone situated downstream in the
flow direction of the drilling fluid in the annular space, the
outside surface of the shaped element presenting a diameter that
increases in the flow direction of the drilling fluid in the prior
stirring and entrainment zone and a diameter that decreases in the
flow direction of the drilling fluid in the annular space in the
turbulence zone.
6/ A shaped element according to claim 5, further comprising, in
the prior stirring and entrainment zone and in the pre-loading
zone, at least one of a plurality of recessed elements and a
plurality of projecting elements spaced apart in the
circumferential direction of the shaped element, configured in
helices about the axis of the shaped element with an angle of
inclination relative to a transverse plane perpendicular to the
axis of the shaped element that increases in the flow direction of
the drilling fluid in the annular space.
7/ A shaped element according to claim 6, further comprising, in
the prior stirring and entrainment zone and in the pre-loading
zone, recessed portions constituted by grooves machined in helices
in the outside surface of the shaped element of the drillrod.
8/ A shaped element according to claim 6, further comprising, in
the prior stirring and entrainment zone, projecting portions
constituted by ribs configured in helices between which the outside
surface of the shaped element of the drillrod is machined to
constitute the recessed portions.
9/ A shaped element according to claim 1, further comprising, at
least in a stirring and entrainment zone having recessed portions
and projecting portions configured in helices, at least one nozzle
passing through a tubular wall of the shaped element of a drillrod
between an internal central space for a flow of drilling fluid in
the drillrod and the annular space outside the shaped element of
the drillrod, the nozzle comprising an inlet channel extending
substantially radially perpendicularly to the axis of the shaped
element of the drillrod and opening out into the inside space of
the shaped element of the drillrod, and an outlet channel
communicating with the inlet channel and opening out to the outside
of the shaped element of the drillrod, the outlet channel being
directed in a direction that is substantially parallel to the axis
of the shaped element in the flow direction of the drilling fluid
in the annular space, i.e. upwards when the drillrod is in its
operating position.
10/ A shaped element according to claim 1, comprising at least one
stirring and entrainment zone having recessed portions and
projecting portions configured in helices about the axis of the
shaped element, and in axial alignment with the at least one
stirring and entrainment zone, it further comprises at least one
mechanical activation and bearing zone in which the drillrod
presents a maximum diameter and has, in its outside surface, at
least one helical groove.
11/ A shaped element according to claim 10, wherein the at least
one mechanical activation and bearing zone comprises, in the
direction of the axis of the shaped element of the drillrod, a
first portion of maximum diameter of the drillrod machined in its
outside surface to form at least one substantially continuous
helical groove analogous to a thread, a middle zone of diameter
smaller than the maximum diameter of the drillrod and without any
helical groove, and a second portion of maximum diameter of the
drillrod machined in its outside surface to present at least one
substantially continuous helical groove.
12/ Drilling equipment such as a drillrod including at least one
shaped element according to claim 1.
Description
[0001] The invention relates to a shaped element for rotary
drilling equipment.
BACKGROUND OF THE INVENTION
[0002] In the field of prospecting and operating petroleum
deposits, strings of rotary drillrods are used that are made up of
rods and possibly other tubular elements depending on drilling
requirements, which rods and elements are assembled end to end.
[0003] Such drill strings can be used in particular to make
deflected boreholes, i.e. boreholes in which the inclination of the
borehole can be caused to depart from the vertical and in which the
azimuth direction can be varied while drilling is taking place.
[0004] With deflected boreholes of large departure including
segments that are horizontal or practically horizontal, friction
torque due to the rotation of the drill string can reach very high
values during drilling. Friction torque can compromise the
equipment used or drilling objectives. Furthermore, it is often
very difficult to raise the cuttings produced by the drilling,
given the way the cuttings produced in the borehole tend to settle,
in particular in the highly inclined portion of the borehole. This
leads to the borehole being poorly cleaned, to an increase in the
coefficient of friction between the rods of the drill string inside
the borehole, and to an increase in the contact surface areas
between the rods and the walls of the borehole.
[0005] In order to reduce the coefficient of friction and the
contact area between the drill string and the walls of the
borehole, and in order to improve the cleaning of the borehole and
the removal of cuttings in the drilling fluid, proposals have been
made in French patent application No. 97/03207 for a drillrod
having at least one bearing zone with a central bearing portion and
two end segments on either side of the central bearing zone, the
outside surface of each end segment having at least one groove
disposed in a helical configuration and of a cross-section that
presents an undercut portion. The bearing zone of the drillrod
which is of diameter greater than the diameter of the end segments
and which can come into contact with the wall of the borehole
serves to reduce friction to some extent between the drillrod and
the wall of the borehole. The end portions which have hydraulic
profiles serve to activate circulation of the drilling fluid and to
unstick cuttings that have become stuck to the wall of the
borehole.
[0006] French patent No. 99/01391 proposes a shaped element for
rotary drilling equipment, which element is generally in the form
of a body of revolution on the axis of rotation of the drilling and
with projecting portions and recessed portions in radial directions
at its outside surface in configurations that are substantially
helical in shape having the same axis as the axis of rotation of
the drilling equipment and in which the projecting portions and the
recessed portions present at least one geometrical and dimensional
characteristic which varies along the axial direction of the
element, at least over a portion of the length of said shaped
element.
[0007] The recessed portions or grooves disposed in helices in the
shaped element are preferably of a transverse flow section on a
plane perpendicular to the axis of the drillrod that tapers in the
axial direction and in the flow direction of the drilling fluid in
the drilling annulus.
[0008] Such shaped elements present distinct advantages when they
are used on a drill string being used for directional drilling, but
it has been found that in some cases it can be desirable to further
improve the stirring and entrainment effect on the drilling fluid
and on the cuttings in the drilling annulus.
OBJECT AND SUMMARY OF THE INVENTION
[0009] The object of the invention is to provide a shaped element
for rotary drilling equipment, the element being generally in the
form of a body of revolution of axis coinciding with the drilling
axis of rotation and having an outside surface with projecting
portions and recessed portions extending in radial directions
perpendicular to the axis in configurations that are substantially
helical about the axis of the shaped element so as to produce an
effect of controlled stirring and accelerated rise of a drilling
fluid with cuttings in an annular space between the shaped element
of the drilling equipment and the wall of a borehole while the
drilling equipment is rotating, said shaped element presenting
improved properties of stirring the drilling fluid and the cuttings
and of entraining the drilling fluid in the drilling annulus.
[0010] For this purpose, each helix along which the projecting
portions and the recessed portions of the shaped element are
disposed has an angle of inclination relative to a plane
perpendicular to the axis of the shaped element that increases in
the axial flow direction of the drilling fluid in the annular
space, i.e. upwards when the drilling equipment is in its operating
position, the axial flow of the drilling fluid being accelerated
along the projecting portions and the recessed portions because of
the direction of rotation of the drillrod.
[0011] The invention also relates to other characteristics of the
shaped element which, combined with the projecting and recessed
portions of varying inclination in accordance with the invention
make it possible further to increase the stirring effect and the
entrainment effect on the drilling fluid and the cuttings in the
drilling annulus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] In order to make the invention well understood, there
follows a description made with reference to the accompanying
figures of two embodiments of a drill string including examples of
shaped elements in accordance with the invention.
[0013] FIG. 1 is a side elevation view of a drillrod having three
shaped elements of the invention, in its working position in a
borehole.
[0014] FIG. 2 is a developed view of a shaped element of the
drillrod shown in FIG. 1.
[0015] FIG. 3 is an axial half-section view of the shaped element
shown in FIG. 2 in developed form.
[0016] FIG. 4A is a cross-section view on 4-4 of FIG. 2 showing a
portion of the section of the shaped element in a first
embodiment.
[0017] FIG. 4B is a cross-section view on 4-4 of FIG. 2 showing a
second embodiment of a portion of the cross-section of the shaped
element.
[0018] FIG. 5A is a cross-section view on 5A-5A of FIG. 2 showing a
first embodiment of the cross-section.
[0019] FIG. 5B is a section view on 5B-5B of FIG. 2 showing the
cross-section of a portion of the shaped elements, in a second
embodiment.
[0020] FIG. 6 is an elevation view of a drillrod having two shaped
elements in a second embodiment.
[0021] FIG. 7 is a side elevation view shown partially in section
of a shaped element in the drillrod shown in FIG. 6.
[0022] FIG. 8 is a cross-section view of a drillrod including a
shaped element of the invention, in its in-service position in a
borehole.
MORE DETAILED DESCRIPTION
[0023] FIG. 1 shows a drillrod given overall reference 1 which
drillrod comprises three shaped elements 2 of the invention in
three zones that are spaced apart along the axial direction of the
rod.
[0024] In conventional manner, the drillrod comprises a female
coupling 1a at one of its ends (its top end) and a male coupling 1b
at its bottom end, the couplings being constituted by frustoconical
threaded portions enabling the successive rods 1 of a drill string
to be connected together.
[0025] FIG. 2 shows a segment of the rod constituting a shaped
element 2, this figure being on a larger scale and in developed
form.
[0026] The rod segment constituting the shaped element 2 mainly
comprises a zone 3 extending over the major fraction of the length
of the shaped segment for the purpose of stirring a drilling fluid
around the drillrod 1 inside a borehole in the annular space 10
that exists between the outside surface of the drillrod and the
wall of the borehole, a shown in FIG. 1.
[0027] In the zone 3, the outside surface of the drillrod is
generally cylindrical in shape, having the same axis as the
drilling axis 4 of the drillrod and having recessed portions 5 and
projecting portions 6 extending in continuous manner along the full
length of the stirring and turbulence zone 3 of the shaped
element.
[0028] The recessed portions 5 are constituted in the form of
grooves of cross-section that may have the shape shown in FIG. 4A
(first embodiment) or in FIG. 4B (second embodiment).
[0029] The projecting portions 6 are in the form of blades lying
between two successive recessed portions or grooves 5.
[0030] The grooves 5 and the blades 6 present respective axes 5a,
6a disposed helically about the same axis as the axis 4 of the
drillrod and turning in a direction for encouraging the drilling
fluid to rise in the annulus 10, given the direction of rotation of
the-drillrod (arrow .OMEGA. in FIG. 2).
[0031] In the invention, the helices 5a and 6a are of inclination
that increases in the flow direction of the drilling fluid in the
drilling annulus (arrow 7), i.e. going upwards when the drillrod 1
is in its operating position inside a borehole, said inclination
being taken relative to a transverse plane perpendicular to the
axis 4 of the drillrod.
[0032] In FIG. 2, there can be seen the trace, in the plane of the
figure, of a cross-section plane 8 together with the tangents to
the helices 5a and 6a of a groove 5 and of a blade 6 in the
stirring zone 3 of the shaped element. The tangents to the helices
5a and 6a constituting the axes or mid-lines of the grooves 5 and
of the blades 6 form an angle .alpha..sub.y with the plane of trace
8 in FIG. 2, which angle is the angle of inclination of the helix
at the cross-section plane of trace 8 at ordinate position y (along
the direction of the axis 4 of the drillrod).
[0033] In the invention, .alpha..sub.y increases with increasing y,
with the ordinates of the points of the drillrod along the
direction of the axis 4 increasing upwards, i.e. in the direction 7
of drilling fluid flow in the annulus 10.
[0034] In particular, the angles of inclination .alpha..sub.e of
the helices 5a and 6a at the inlet to the zone 3 are smaller than
the angles of inclination .alpha..sub.s of the helices at the
outlet from the stirring and entrainment zone 3 of the
drillrod.
[0035] As can be seen in FIG. 4A, the grooves 5 may be of a shape
in cross-section such as that described and claimed in French
patent application No. 97/03207, said shape making it possible to
bail out the drilling fluid present in the annulus 10 of the
borehole vigorously given that the section of the groove 5 presents
in particular an undercut portion defined by a straight line
portion of the section making an angle .beta.1 with the direction
perpendicular to the axis 4 of the drillrod, along the outer edge
of the section 5 disposed towards the back of the groove relative
to the direction of rotation .OMEGA. of the drillrod about its axis
or rotation 4 (FIG. 2).
[0036] In addition, the grooves disposed helically about the
drillrod serve to entrain the drilling fluid and the cuttings
within the annulus 10 in an upward direction as shown by arrow 7,
due to the rotation of the drillrod.
[0037] The increasing slope of the helices in the upward direction
entrains the drilling fluid at increasing speed in the annulus and
provides an increased sweeping effect of the borehole. As a result,
the field of speeds inside the annulus 10 is modified, the speeds
being modified in absolute value and in direction along the
direction y of the axis 4 of the drillrod and of the shaped element
2. The increase in the inclination of the helices in the direction
y can be modulated as a function of the operating conditions of the
drillrod.
[0038] In addition, the sections s.sub.y of the grooves 5 decrease
in the direction of the arrow 7, i.e. in the direction of
increasing ordinate values y. The decreasing sections s.sub.y of
the grooves 5 can be obtained either because the grooves 5 are of
depth that decreases in the direction of increasing ordinate values
y, or because the grooves are of width that decreases in the
direction of increasing ordinate values, or indeed because they
present both depth and width that decrease.
[0039] Each projecting portion 6 or blade is disposed between two
successive grooves 5, and because of the decreasing section and
width of the grooves 5, these portions are of section and width
that increase in the direction of increasing ordinate values y (or
the fluid flow direction in the annulus 10 as represented by arrow
7).
[0040] As can be seen in FIG. 4B, in cross-section the grooves 5
may be asymmetrical in shape without any undercut portion, the
effect of bailing out and stirring the drilling fluid nevertheless
being less intense than it is with the grooves of the first
embodiment as shown in FIG. 4A where there is an undercut portion.
The grooves in the second embodiment are easier to machine, and
they nevertheless enable a satisfactory bailing out and stirring
effect to be obtained because of the presence of the blades 6
between pairs of successive grooves 5. As in the first embodiment,
the grooves 5 may be of section, depth, and/or width that tapers in
the direction 7 in which fluid flows in the annulus 10 (the
direction in which ordinate values y increase), the blades 6 being
correspondingly of section and of width that increase.
[0041] As can be seen in FIG. 2, upstream from the stirring and
entrainment zone 3 relative to the flow direction 7 of the drilling
fluid, the shaped element 2 has in succession: a prior stirring
zone 9; a hydraulic pre-loading zone 11; and a turbulent zone
13.
[0042] As can be seen in FIG. 3, the pre-loading zone 11 is
constituted by a portion of the drillrod that has a diameter
.PHI..sub.r that is perceptibly greater than the maximum diameter
of the drillrod 1 in the stirring zone 3. On the outside surface of
the drillrod, the zone 11 may be defined by a toroidal surface, as
shown in particular in FIGS. 1 and 3, with the maximum diameter
.PHI..sub.r then being the diameter of the middle portion of the
toroidally-shaped zone 11.
[0043] The connection between the pre-loading zone 11 of the
drillrod and the stirring zone 3 is made via the "turbulence" zone
13 in which the drillrod presents a tapering diameter following a
curved surface of section as shown in FIG. 3.
[0044] The pre-loading zone 11 runs into the ordinary portion of
the drillrod below the shaped element 2 via the prior stirring zone
9 of diameter that increases in the direction of increasing
ordinate values y (or in the flow direction 1 of the drilling fluid
in the annulus 10) and of curved longitudinal section that is
substantially analogous to the longitudinal section of the
turbulent zone 13, as can be seen in FIG. 3. The inclination of the
curved portion of the prior stirring zone 9 relative to a direction
parallel to the axis 4 of the drillrod, where it connects with the
pre-loading zone 11, is less that the inclination of the curved
portion connecting the turbulence zone 13 to the bearing zone
(angle .beta.2.ltoreq..beta.3, see FIG. 3).
[0045] On either side of the shaped element 2, the ordinary portion
of the drillrod presents a nominal diameter .PHI..sub.DN.
[0046] The shaped element 2 also connects with the ordinary portion
of the drillrod 1 of nominal diameter .PHI..sub.DN, at its
downstream end, via a bearing zone 4 where the rod has a maximum
diameter .PHI..sub.u that is perceptibly greater than or equal to
the diameter .PHI..sub.r of the upstream pre-loading zone 11 (which
can in some cases also constitute a bearing zone).
[0047] The diameters .PHI..sub.r and .PHI..sub.u are perceptibly
greater than the nominal diameter .PHI..sub.DN of the ordinary
portion of the drillrod, with the pre-loading zone 11 and the
bearing zone 14 constituting two radially-projecting zones,
respectively in the upstream and downstream portions of the shaped
element 2.
[0048] In the prior stirring zone 9, and in the pre-loading zone
11, the shaped element 2 has hollow portions or projecting portions
16 that are spaced apart from one another in the circumference
direction of the drillrod and each of which is disposed along a
helix 16a of inclination relative to a plane extending transversely
to the drillrod that increases in the direction of increasing
ordinate values y, in the same manner as the helices 5a and 6a of
the grooves and projecting portions 5 and 6 of the stirring zone
3.
[0049] When the portions 16 are recessed portions in the radial
direction and constitute grooves, their section, their depth,
and/or their width may be constant or tapering in the direction of
increasing ordinate values y. When the portions 16 are projecting
portions, their section and/or their width may be constant or
increasing in the direction of increasing ordinate values y. Their
height may decrease in the direction of increasing ordinate values
y.
[0050] This produces an increased entrainment effect on the
drilling fluid in the initial stirring zone 9 and in the
pre-loading zone 11.
[0051] Furthermore, the presence of the curved surface in the zones
9 and 11 which present increasing diameter in the flow direction of
the fluid gives rise to the stream lines of the fluid separating
from the drillrod, with these stream lines then being delivered
with turbulent flow from the pre-loading zone 11 into the
turbulence zone 13 where the drilling fluid establishes vortices
that are favorable for mixing and entraining drilling cuttings in
the drilling fluid, which fluid is then taken up by the main
entrainment and stirring zone 3.
[0052] FIG. 5A shows the cross-section of grooves 16 placed in
helices and constituting recessed portions of the prior stirring
zone 9 and of the pre-loading zone 11, in a first embodiment. The
grooves 16 present depth and width, and thus section, that are
generally constant in the fluid flow direction 7 or the direction
of increasing ordinate values y. Nevertheless, the width and/or the
depth, and thus the section, of the grooves 16 may also decrease in
the direction of increasing ordinate values. The grooves 16 are
obtained by machining the outside surface of the drillrod in the
vicinity of the curved surface coupling the ordinary portion of the
drillrod with the toroidal bearing zone 11.
[0053] FIG. 5B relates to a second embodiment in which projecting
portions 16 constitute ribs following helical paths around the axis
of the drillrod. The inclination of the helical paths followed by
the ribs 16 increases in the direction of increasing ordinate
values. In addition, the width of the ribs 16 may decrease and/or
their height may decrease in the direction of increasing ordinate
values y, such that the cross-section of the recessed zones 17
between two projecting portions 16 decreases in the direction of
increasing ordinate values y. This gives rise to transverse flow of
the drilling fluid, thereby increasing turbulence and stirring.
[0054] The pre-loading zone 11 makes it possible to deflect the
drilling fluid outwards, thereby encouraging cuttings to rise in
the annulus 10. In addition, like the zone 9, the pre-loading zone
11 serves to create pre-stirring of the drilling fluid and the
cuttings prior to the zone 3.
[0055] The pressure of the drilling fluid is also raised
(pre-loading) in the zone 11.
[0056] A second loading zone 11' analogous to the above-described
zone 11 may be situated downstream from the bearing zone 14 (in the
flow direction 7 of the fluid in the annulus 10) in order to
reinforce the cutting-rising effect. This additional zone
constitutes a post-loading zone for the device.
[0057] For this purpose, downstream from the radial projecting
portion 14 of the drilling device, there is provided a second
radially-projecting portion constituting zones analogous to the
stirring zone 9 and to the pre-loading zone 11 situated at the
upstream end of the device.
[0058] FIGS. 2 and 3 also show a nozzle 18 which is inserted and
fixed in the wall of the tubular drillrod 1 in the stirring and
entrainment zone 3.
[0059] By way of example, the nozzle 18 may be placed in the bottom
and in the middle portion of a groove 5 in the stirring and
entrainment zone 3. The nozzle 18 has a first duct or inlet channel
18a extending substantially in a radial direction of the drillrod,
opening out into the inside space of the tubular drillrod 1, and a
second duct 18b or outlet channel communicating with the inlet
channel 18a and extending substantially axially or slightly
inclined towards the outside of the drillrod 1 in an upward
direction. The outlet channel 18b opens out into the annulus 10
outside the drillrod via a top end portion of the nozzle 18 that
points upwards.
[0060] The drilling fluid flowing downwards in the inside space of
the tubular drillrod 1 (arrow 7') is at a pressure that is
significantly higher than the pressure of the drilling fluid
flowing upwards in the drilling annulus 10 outside the drillrod
(arrow 7). As a result, the drilling fluid is entrained from the
inside of the inlet channel 18a of the nozzle 18 and then ejected
upwards via the outlet channel 18b inside the groove 5 in which the
nozzle 18 is fixed. This increases the flow speed and the stirring
of the fluid, with one or more nozzles being used that are
preferably disposed inside one or more stirring and entrainment
grooves 5 in the zone 3 of the shaped element 2 of the
drillrod.
[0061] FIG. 6 shows a drillrod given overall reference 1 and
comprising two dual shaped elements of the invention, constituting
a variant embodiment and referenced 2'.
[0062] As can be seen in FIG. 7, the shaped element 2' of the
drillrod 1 is made in dual form and comprises in succession, going
upwards: a first stirring and entrainment zone 3'a, a first
mechanical activation and bearing zone 13'a, a second activation
and entrainment zone 3'b, and a second mechanical activation and
bearing zone 13'b.
[0063] The stirring and entrainment zones 3'a and 3'b are made in
accordance with the invention, i.e. they have grooves 5' separated
by blades 6' disposed along helices of angle relative to a
transverse plane perpendicular to the axis 4 of the drillrod that
increases in the flow direction 7 of the drilling fluid in a
drilling annulus 10 outside the rod 1. The widths and/or depths,
and thus the cross-sections of the grooves 5' may decrease in the
flow direction 7 of the drilling fluid in the annulus 10 so as to
increase turbulence and produce a fluid-bearing effect.
[0064] In addition, the stirring zones 3'a and 3'b are also made in
the form of deflection zones in accordance with French patent
application No. 01/05752, the outside surface of the drillrod in
the stirring and entrainment zones 3'a and 3'b that are inclined
relative to the axis 4 of the drillrod presenting a meridian line
in an axial plane that goes away from the axis 4 of the shaped
element 2 and of the drillrod 1 in the flow direction 7 of the
drilling fluid in the annulus, i.e. in the upward direction when
the drillrod is in its operating position in a borehole.
[0065] This produces a stirring effect that is increased because a
component in the radial direction is added to the speed of the
drilling fluid entrained by the grooves 5' and by the projecting
portions 6' of the stirring and entrainment zones 3'a and 3'b.
[0066] A circular arrow .OMEGA. shows the direction in which the
drillrod rotates when in operation in a borehole. The ordinary
portion of the drillrod of diameter .PHI..sub.DN is shown on either
side, i.e. upstream and downstream of the shaped element 2'.
[0067] In the mechanical activation and bearing zones 13'a and
13'b, the shaped element 3' presents a maximum diameter that is
significantly greater than the diameter .PHI..sub.DN. In the zones
13'a and 13'b, the outside surface of the shaped element is
machined so as to present two successive portions of greatest
diameter separated by a middle portion of smaller diameter.
[0068] The two portions of greatest diameter in the mechanical
activation and bearing zones 13'a and 13'b are machined so as to
present at least one continuous helical groove at a small angle of
inclination, generally less than 30.degree. relative to planes
extending transversely to the drillrod and perpendicularly to the
axis 4, such that the two portions of the mechanical activation and
bearing zones 13'a and 13'b on either side of the middle zone
without a helical groove are of a shape that is analogous to a
threaded element with successive threads that are substantially
helical in shape. This produces an effect of entraining the fluid
in the bearing zone when the drillrod is rotating in the direction
shown by arrow .OMEGA. (Archimedes' screw effect) and a fluid
bearing effect where the drillrod bears via the bearing zones 13'a
and 13'b.
[0069] FIG. 8 shows a cross-section of a shaped element 2 of a
drillrod 1 across a stirring zone such as the stirring zone 3 in
which the shaped element 2 has asymmetrical grooves 5 possibly
including undercut portions serving to bail out the drilling fluid
out thoroughly from the annulus 10 inside the borehole 20 when the
drillrod is rotating in the direction of arrow .OMEGA.. In the
annulus 10, the drilling fluid entrains the cuttings 19 produced by
the drilling inside and along the grooves 5 of the stirring and
entrainment zone 3 of the shaped element. As it rotates inside the
borehole 20, the drillrod 1 approaches the edge of the borehole
such that the annulus 10 is of with that varies in the
circumferential direction of the drillrod.
[0070] FIG. 8 is a cross-section through the drillrod seen from the
bottom of the borehole, the flow of drilling fluid in the drilling
annulus causing the cuttings 19 to be entrained taking place in a
direction that is perpendicular to the section plane of FIG. 8,
towards the back of the plane of FIG. 8.
[0071] The provision of the stirring and entrainment zone 3 on the
shaped element of the drillrod of the invention makes it possible
to bail out and entrain upwards the drilling fluid and the cuttings
19 so that circulation of the drilling fluid and the cuttings in
the annulus 10 takes place preferentially in the zone 21 where the
outside surface of the drillrod is at its furthest away from the
wall of the borehole 20, and not in the zones 22 where the drilling
annulus 10 does not present maximum width. The dispositions of the
invention thus serve to obtain an ideal distribution of vertical
entrainment speeds in the annulus 10 around the drillrod.
[0072] Similarly, the pre-loading zone 11 serves to establish a
speed gradient and thus a pressure gradient in the flow of drilling
fluid in the annulus 10 so as to direct the flow preferentially
towards the zone 21.
[0073] The shaped element of the invention thus makes it possible
to optimize stirring and entrainment of the drilling fluid and the
cuttings inside the annulus, in particular in deflected boreholes
that present portions that are practically horizontal.
[0074] The invention is not limited strictly to the embodiments
described above.
[0075] Certain variant embodiments of the shaped element can be
devised by a plurality of stirring zones, loading zones, and/or
pre-loading zones, and entrainment zones with a plurality of
mechanical activation and bearing zones such as those described
above.
[0076] The invention applies to any element of a string of
drillrods and in particular to those elements of a string of
drillrods that are used for directional drilling.
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