Note: Descriptions are shown in the official language in which they were submitted.
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TECHNICAL FIELD
This invention relates to improvements in oil
well drilling equipment. In particular, it relates to an
improved mechanism for activating down hole adjustable
stabilizers.
Furthermore, the present invention provides an
adjustable stabilizer which has a number of selectable
positions which can be locked in place or released.
BACKGROUMD OF THE INVENTION
In recent years drilling techniques for oil and
gas wells have developed to the point where sophisticated
controls may be used to alter the direction or rate of advance
of the drilling bit. Among these techniques is the use of
a device widely known as an adjustable stabilizer whereby
a section of drill pipe (often referred to as a sub) near
the bottom of the drill string slightly behind the bit, may
be used to alter the manner in which the drill string rests
against the side of the hole and thereby change the direction
of the nearby bit, and hence the direction of the hole.
These adjustable stabilizers frequently take the form of
pads mounted in the sub which can be expanded radially to
increase the diameter of the sub or released and contracted
to narrow the effective diameter of the drill string at the
location of the stabilizer sub.
In addition, the marginal profitability of many
oil and gas well drilling operations requires that these
control functions be capable of operating with a minimum
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of down time. It is, therefore, important to develop
activating mechanisms which can be controlled by the driller
without withdrawing the drill string and stabilizer sub from
the hole which is a time consuming interruption in the
drilling performance. Consequently, various techniques have
been developed for manipulating the mechanism of adjustable
stahilizers while the equipment is down hole.
Some of these prior mechanisms have been controlled
by adjusting the weight on the drill string but this approach
has the disadvantage that often it is very hard to determine
the actual weight which is being applied at the down hole
location of the stabilizer sub because deep, deviated holes
have a large amount of "hole drag".
Other mechanisms are designed to be set or released
by the flow ra~e at which drilling mud is pumped through
the central bore of the drill string. However, often the
rig is operating at close to the maximum flow rate and
therefore there is little flexibility available to increase
the flow enough to activate a tool of this design.
Still other mechanisms rely on controls activated
by the pressure of the drilling mud but like the former flow
set tools, a range of pressures is not always available to
the drillerl or it may not be desirable to operate the drill
at less than maximum pressure. For the above reasons, it-
is important to develop mechanisms by which down hole devices
such as stabi:Lizers may be engaged or disengaged by operations
which can be conducted at the drill floor but without limiting
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the drillers abili-ty to select the desirable weight, flow
rate or mud pump pressure for optimum conditions during
drilling operations.
DISCLOSURE OF THE INVENTIO~
It is, therefore, the purpose of this invention
to provide a down hole control mechanism for adjustable
stabilizers and other tools which may be activated from the
drill floor without pulling out the drill string.
It is a further purpose of this invention to
provide a control mechanism for down hole tools which may
be set and locked so that it will remain at the desired
setting regardless of variations in the drill string weight,
mud flow rate, or pump pressure which a driller wishes to
use during the drilling operations.
It is a further purpose of this invention tv
provide a mechanism which may be activated, locked and
subsequently unlocked and readjusted repeatedly as required.
It is a further purpose of this invention to
provide a control mechanism which may be activated by varying
degrees to provide the desired setting of ~he tool as required
with some degree of certainty and precision.
These objects and other advantages are sought
to be achieved by the present invention which provide a down~
hole drilling tool activating mechanism comprising a drill
sub connectabla between adjacent lengths of drill pipe having
a main body and tool elements mounted in the body ~o be
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activated and deactivated by a mandrel located within the
body, capable of vertical movement relative to the main body
and having cam surfaces bearing against the tool elements
to activate and deactivate same upon vertical movement of
the mandrel. A series of flexible fingers extending ~rom
one end of the mandrel and vertically fixed thereto has
engaging teeth thereon and teeth engaging means mounted to
said body and vertically fixed thereto so that the mandrel
and the main body are fixed vertically relative to each other
when the teeth and teeth engaging means are engaged. A male
spline member is rotatably locked to said main body to permit
rotational forces to be transmitted through the tool but
the male spline member is capable of vertical movement
relative to the main body, by lifting or lowering the drill
string, and a portion of the male spline member is moveable
vertically within the main body between a locking position
in which the male portion engages the flexible fingers forcing
them to engage with the tooth engaging member and an unlocked
position in which the portion of the male spline member is
removed from the flexible fingers to allow them to disengage
said teeth engaging member. Bias means, such as a spring,
is located to urge the mandrel in one vertical direction
and seal means are provided on said mandrel located such
that mud pump pressure exerted through the bore of the drill-
string will act on the end of the mandrel in a direction
opposite to the bias means.
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In one embodiment, the activating mechanism is
used in connection with a t:ool which is a stabilizer and
the tool elements are radially adjustable pads capable of
adjusting ~he diameter of the stabilizer tool.
In one variation of the invention, the mechanism
is designed so that the pads have inwardly inclined surfaces
and the mandrel has truncated conical shaped elements bearing
against the inclined surfaces of the pads.
In another variation of the invention, the mandrel
comprises at least one surface adapted to bear against the
inner surface of the pads in which said mandrel surface is
shaped to provide an increasing radial dimension in a given
circumferential direction so that rotational movement will
activate or deactivate the pads.
The tool may be designed so that the pads are
arranged in a helic~l configuration and the mandrel ha~ a
similar helical configuration about the longitudinal axis
of the tool. In variations where a rotational motion is
required or a helical mandrel is employed, the rotational
movement of the mandrel is controlled by a key and keyway
controlling the relative rotational movement between the
mandrel and the main body.
The invention may also be provided with a flow
restrictor mounted on the drill sub comprising a restrictor
sleeve mounted for movement with the movement of the mandrel
and a bullet mounted for movement with the main body such
that when the mandrel is moved relative to the main body,
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back pressure resulting from the restricted flow is variable
according to the relative ve:rtical position of the mandrel
compared to the main body and the position may be determined
by the operator.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invent:ion may be better understood
by a description of one embodiment thereof with reference
to the attached drawings in which:
Figure 1 is a vertical cross section of an
embodiment of the present invention separated in sections
l(a), l(b) and l(c);
Figure 2(a) and Figure 2(b) are illustrations
of a modified version of the mechanism shown in Figure 1
in two different setting positions;
Figures 3(a), 3(b) and 3(c) are schematic
illustrations of activating parts of the mechanism in three
different positions;
Figures 4(a) and 4(b) show in vertical cross
section, a modified version of the mechanism in Figure 1
in two positions respec,tively;
Figures 5 is a graphic representation of a
perspective view of the part showing in Figures 3(a), 3(b)
and 3(c).
BEST MODE OF CARRYING OUT THE INVENTION
Although the present invention may have other
applications, the preferred embodiment illustrated in the
drawings applies to a multi-position adjustable stabilizer
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sub shown in Figure 1. The elements shown in Figure l(a)
include a box end 2 of a s~abili.zer sub attached to a male
spline 4 which has a male spli.ne shoulder 6 immediately above
a seal cap 8 having seals 10 isolating the bottom of the
male spline 4 and an oil plug 12. The seal cap 8 is
threadedly engaged to a female spline section 14 so that
a longitudinal section of spline bars 16 have overlapping
adjacent splines f.rom the male and female section respectively
so that the maLe spline 4 may move vertically with respect
to the female spline but the two are locked circumferentially
so that rotational mov2ment may be transmitted through them
from the drill string above to the drill string below.
Threaded onto the bottom of the female spline
is the main body 20 of the stabilizer sub into which extends
the lower extension 18 of the male spline 4.
The main body is provided with an oil plug 22.
Between the lower extension of the male spline 18 and the
lower bore of the female spline is an upper stopper ring
24 threaded to the male spline extension and a lower stopper
ring 26 threaded to the bore of the female spline 14.
As best seen in Figure l(b), a floating piston -.
28 is positioned between the male spline extension 18 and
the inner bore of the main body 20. Below the floating piston
28 is an Annular port 30 equalizing the fluid pressure of
the annular space between the drill string and the bore hole
with the inner space between the male spline extension and
the main body.
Beneath the anular port is a slip seal ring 32
sealed against the extension 18 and the main body and fixed
in position by set screws 34 locking it relative to the main
body 200 The bored out section of the slip ring 32 has a
set of inwardly facing teeth 36 which engage a set of
outwardly facing teeth 38 on a series of slip fingers 40
spaced at intervals around the periphery of the male spline
extension 18.
The fingers 40 are connected at their lower end
to a ring 42 threaded into the top of a pad mandrel 44 so
that the fingers and pad mandrel are fixed vertically
together.
A set screw 48 holds the ring 42 in position and
a set of seals 46 ïsolate the slip fingers and slip seal
ring from the drilling mud and annulus pressure to which
the lower end of the pad mandrel is exposed.
The pad mandrel 44 has a series of inclined or
tapered surfaces 50 which engage similarly inclined surfaces
52 of the pads 54. Thus, when the mandrel is moved vertically
downward, the inclined surfaces will force the pad 54 outward
in a radial direction providing an increased diameter to
the drill string at that location. The details of this
activation will be referred to below.
The pads 54 are biased in the inward direction
by pad springs 56 and are isolated from the anular mud by
pad seals 58 held in place by pad lock rings 60.
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For purposes of the illustration in Yigure 1,
the pads are shown vertically aligned in the plane of the
cross sectlon. It is, however, possible and even advantageous
to arrange these pads in a sequence along an inclined helical
path or pattern so that the contact with the bore hole will
be provided for in a uniform distribution about the periphery
of the stabilizer sub.
The bottom of the pad mandrel, like the top, has
a cylindrical portion which fits within the lower end of
the main body 20 below the adjustable stabilizer pads.
The bottom of the pad mandrel has a wash pipe
62 connected by threads having an internal diameter equivalent
to the ID of the male spline and the pad mandrel but having
an outer diameter substantially reduced so as to leave a
chamber between i~ and the lower main body 20 housing a spring
64 which urges the mandrel upward.
As seen in Figure l(c) the spring 64 rests at
its lower end on a seal sleeve 66 mounted in the lower end
of the main body 20 and held in place by the pin end of a
bottom sub 70.
The seal sleeve 66 is provided with outer seals
68 against the main body 20 and a lower floating piston 72
between the sleeve and the wash pipe 62. A lower anular
port 74 allows equalization of the pressure between the bore-
hole annulus and the interior of the seal sleeve.
The bottom sub 70 has a restrictor sleeve 76
threadedly connected to the lower end of the wash pipe 62
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and the wash pipe at its lower end is sealed against the
body of the bottom sub by bottom sub seals 78.
Beneath the restric~or ~leeve, a restrictor bullet
is inserted in the bore of the bottom sub in such a way that
it combines with the restrictor sleeve to effect the flow
rate and back pressure when rnud is pumped through the bore.
Because the bullet is fixed in the bottom sub 70 by a set
screw 80 the flow restriction will depend on the relative
position of the restrictor sleeve which in turn is determined
by the vertical placement of the pad mandrel to which it
is connected by means of the wash pipe 62.
The lower end of the bottom sub is provided with
a threaded pin end for connection to the lower end of the
drill string carrying the drill bit.
INDUSTRIAL_APPLICATION
By the mechanism illustrated in Figure 1, the
effective diameter of the stabilizer sub may be altered from
the minimum diameter shown in the illustration to a larger
diameter represented by the full outward radial extension
of the pads 54. Furthermore, by virtue of the combination
of features in this invention, the pads 54 may be set at
any desired intermediate position. Furthermore, by this
mechanism the dPsired diameter may be set and locked in place
so that it will remain constant regardless of variations
in drill string weight, pump pressure or flow rate which
may be chosen for optimum drilling conditions.
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The operation of the illustrated embodiment may
be understood by the following example.
The spline bars 16 allow the male spline 4 to
move vertically relative to the female spline and the main
body of the stabilizer sub. The downward movement is limited
by the male spline shoulder 6 which seats on the seal cap
8 and the upward limits of the movement of the male spline
is governed by the upper stop ring 24 which encounters the
top of the bore in which it is located. If the male spline
is moved upward, the extension 18 will rise out of and above
the slip fingers 40 and the slip fingers are then free to
flex inwardly so that they are no longer rigidly locked in
vertical relationship to the slip seal ring 32.
In this position, the slip fingers and the pad
mandrel 44 to which they are connected are free to move
vertically.
If no mud pressure is applied, the spring 64 will
urge the mandrel into its uppermost position as illustrated
in Figure 1, in which the top of the mandrel is butting
against the lower end of the slip seal ring 32. The pads
54 are then retracted.
If increased pressure is applied by the mud pump,
this pressure will be communicated down the bore of the drill
string to the bottom of the male spline extension 18 and~
through the gaps between the split fingers to the top of
the pad mandrel wher~ the pressure will be applied across
an area equivalent to the difference between the diameter
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of the m~ in body and the inner diameter of the pad mandrel.
Thls pressure will tend to force the pad mandrel downward
against the resistance of the spriny 64 and the distance
of that vertical movement will depend on the degree of mud
pump pressure which is applied against that spring. As the
pad mandrel moves downwardly, the inclined surfaces 50 will
bear against the mating surfaces 52 of the pads 54 and force
them in a radially outward direction against the resistance
of the pad springs 56 and the degree of vertical movement
of the pad mandrel will determine the degree of outward
movement of the pads and therefore determine the chosen
setting between the minimum and maximum diameter. By suitable
testing and calibration, it can be determined what degree
of mud pump pressure is required to compress the spring 64
in order to achieve various degrees of adjustment of the
pads and thus the overall diameter of the stabilizer sub. . .~.
Once the adjusted diameter is achieved, the
position may be locked by lowering the drill string so that
the male spline extension 18 moves downwardly into the
position illustrated in Figure l(b) where it forces the slip
fingers outwardly to engage the teeth of the slip ring 32
thus locking the fingers and therefore the pad mandrel in
vertical relationship to the main body. In this way the.-
radial setting of the pads 54 will remain fixed.
The various seals separate the drilling mud flow
from the parts of the mechanism which are filled with
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hydraulic fluid to avoid contamination and to isolate
pressures needed to activate the mechanism.
The lower anular port 74 exposes the bottom of
the floating piston and therefore the spring chamber and
the lower end of the pad manclrel to the mud pressure of the
bore hole annulus which is generally lower than the mud
pressure on the inner bore of the string because of the
restriction at the drill bit. Thus, an increased pump
pressure will have the effect of moving the pad mandrel
vertically downward when the tool is in the adjustable
position.
As previously mentioned, the pads illus~rated
in Figure l(b) are shown in vertical alignment for ease of
illustration but it may be desirable to arrange them in an
inclined helical sequence so that they are distributed evenly
around the circumference of the stabilizer sub.
It is also possible to use a pad mandrel in which
the inclined surface bearing against the inner end of the
pads is no* a tapered, trunca~ed, cone shape about a vertical
axis as illustrated in l(b) but may be an inclined surface
in which the radius varies in a horizontal circumferential
direction as illustrated in Figure 5.
The operation of this version is illustrated in
Figures 3(a), 3(b) and 3(c). On the left, the horizontal
cross section of a modified pad mandrel 144 is illustrated
with a pad 154 located at various positions on the mandrel.
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It will be appreciated that iE a mandrel of this
configuration is rotated counter clockwise relative to the
pad as illustrated sequentiaLly in Figures 3(a), (3(b) and
3(c), the increasing diameter of the mandrel 144 will push
the plug 154 in an outward radial direction.
If the mandrel shown in Figure 6 has pads
positioned in an inclined, helical, configuration, the cam
effect of the profile can be effected by rotational movemen~,
vertical movement, or a combination of both. Thus, as
illustrated schematically to the left in Figures 3(a), 3(b)
and 3(c), the edge of the profile 157 is represented by an
inclined or helical line and the relative location of the
plugs (also arranged in an inclined helical sequence, is
shown in relative proximity. As the extreme outer dimension
of the mandrel represented by the line 157 moves downwardly
and/or rotatingly towards the plugs 154, the increased
diameter of the mandrel will cause the plugs to move radially
outward to a lar~er diameter.
Thus, the vertical movement illustrated in Figure
1 may be employed to effect adjustment with a mandrel with
an inclined configuration shown in Figures 3 and 5. In this
case, since the mandrel is not cylindrical, it is important
to control the rotational position of the mandrel and this
is done by means of a keyway 160 cut in the bottom of the-
mandrel and a cooperating key 162 locked in the lower main
body of the sub. If the key and keyway are vertically
disposed, the mandrel will move vertically but will be fixed
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against rotational movement. If the keyway is inclined,
vertical movement of the pad mandrel will result in a combined
vertical and rotational movement. Either way, the relative
movement of the mandrel from a position in which the pads
contact a small diameter portion to a position in which the
pads contact a larger diameter portion will have the effect
of increasing the radius of the stabilizer sub.
An alternative arrangement is shown in Figures
2(a) and 2(b) in which the male spline 4 has a stopper ring
25 threaded onto the lower extension 18 which butts against
the pln end of the female spline sub 14 to limit upward
movement. The downward position is illustrated in Figure
2(b).
An alternative arrangement of the flow restrictor
is illustrated in Figures 4(a) and 4(b) in which the
constriction in the bore formed by a diminished ID 77 is
located in the bottom of the wash pipe 62 and therefore moves
up and down with the mandrel while the plug 79 is adjustably
fixed by threads 81 to the bottom of the main body of the
sub. Thus, in the position shown in Figurs 4(b) the drill
s~ring bore is relatively open to mud flow whereas in the
position of Figure 4(a) ~he flow is considerably restricted
and will result in a measurable back pressure at the mud
pump. This measurable back pressure can be used by the
driller as an indication of the vertical location of the
mandrel and therefore the diameter adjustment.
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Mechanisms such as the embodiments illustrated
may be calibrated so that known operating criteria such as
mud pump pressure or flow rate will provide the desired
vertical movement (or vertical and rotational movement) of
the mandrel suficient to achileve various degre~s of expansion
or activation of the pads so as to effect specific desired
diameters.
Similarly, the flow restrictor and bullet or plug
may be adjusted and calibrated so that the operator can
identify the precise location of the mandrel by virtue of
the back pressure effected by thP flow restrictor.
Thus, by means of the present invention, a down
hole adjustable stabilizer may be activated by liEting the
drill string sufficient to release the slip finger, activating
the mud pump to effec~ the desired degree of vertical movement
of the mandrel and therefore the desired degree of increased
diameter in the stabilizer pads and then this setting may
be locked by returning the male spline extension into
engagement with the fingers to lock them in position and
maintain the relative vertical adjustment of the mandrel.
This adjustment setting will then be maintained during
drilling operations regardless of the weight on the bit,
the flow rate of the circulating mud or the pump pressure
applied. Similarly, the pads may be deactivated or readjusted
repeatedly as desired.
It will, of course, be realized that numerous
modifications and varia~ions of the illustrated embodiment
may be employed without departing from the inventive concept
herein.
