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EP 0 015 137 B1 |
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EUROPEAN PATENT SPECIFICATION |
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Mention of the grant of the patent: |
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22.02.1984 Bulletin 1984/08 |
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Date of filing: 19.02.1980 |
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International Patent Classification (IPC)3: E21B 7/06 |
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Apparatus for directional drilling
Vorrichtung zum Richtungsbohren
Dispositif pour le forage dirigé
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Designated Contracting States: |
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DE FR GB |
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Priority: |
21.02.1979 US 13584
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Date of publication of application: |
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03.09.1980 Bulletin 1980/18 |
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Applicant: Conoco Inc. |
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Ponca City
Oklahoma 74603 (US) |
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Inventors: |
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- Thakur, Pramod C.
Morgantown
West Virginia 26505 (US)
- Lauer, Stephen D.
Waynesburg
Pennsylvania 15370 (US)
- Farris, Nathandale
Ponca City
Oklahoma 74601 (US)
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(74) |
Representative: Leale, Robin George et al |
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Frank B. Dehn & Co.,European Patent Attorneys,
179 Queen Victoria Street London EC4V 4EL London EC4V 4EL (GB) |
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] This invention relates to an apparatus for drilling generally horizontal bore-holes
in a subterranean earth formation, and more particularly to an apparatus for adjusting
the trajectory of such a borehole to maintain same within the upper and lower boundaries
of a mineral bed such as a seam of coal.
[0002] The drilling of long generally horizontal gas drainage holes in coal beds is known
in the art as a method for degasifying a coal bed in advance of mining. The gas drainage
holes drilled in this manner are either vented or connected to a vacuum source to
remove methane from a coal bed. The greatest problem encountered in drilling these
gas relief holes is that of maintaining the bit trajectory within the coal seam such
that the resulting holes are actually through the coal seam rather than through an
overlying or underlying formation. Control of boreholes trajectory is also important
in exploratory drilling for coal or other minerals.
[0003] A directional drilling system including a drill shaft, a down-hole fluid motor connected
to a rotatable bit, and a deflection means is described in U.S. Patent No. 3,260,318.
The deflection means described there is a shaft housing having a slight angle formed
therein to divert the drill bit from the axis of the drill shaft. Rotation of the
drill shaft and housing through part of a turn changes the direction of the borehole
relative to the drill shaft. However this apparatus has been found to give poor results
in controlling the trajectory of generally horizontal boreholes. An apparatus for
drilling boreholes is disclosed in U.S. Patent No. 3,888,319 wherein a deflection
means for drilling apparatus includes a deflection member which is urged by means
of hydraulic pressure against a wall of the borehole. However such an arrangement
is somewhat awkward mechanically.
[0004] According to the invention there is provided drilling apparatus as disclosed in US-A-3,888,319,
comprising a down-hole motor, a rotatable shaft for connecting said motor to a drill
bit, a non-rotating housing extending from said motor over said shaft, and a deflection
member carried by said housing, said deflection member extending radially beyond said
housing sufficiently to apply a deflection force to the wall of a borehole during
drilling and being movable perpendicularly to the longitudinal axis of the housing,
and is characterised in that the deflection force is provided solely by spring means
acting between part of the housing and the deflection member, the deflection member
being mounted on said housing in a manner to assure rotation of said deflection member
corresponding to rotation of said housing and that said spring means continuously
urge a borehole wall contacting surface of the deflection member away from one side
of the housing and into engagement with the borehole wall with sufficient force to
deflect the trajectory of the borehole during drilling.
[0005] In operation the deflection member applies a predetermined radial force to a drill
bit, causing the trajectory of the borehole being drilled to be deflected in the direction
of the applied force.
[0006] Further embodiments of the deflection member and the spring means are indicated in
claims 2-5.
[0007] An embodiment of the invention will now be described by way of example and with reference
to the accompanying drawings, in which:-
Figure 1 is an illustration of a drilling apparatus showing the relation of a deflection
member of the invention to the other parts of the apparatus;
Figure 2 is an exploded view showing the structural details of a preferred embodiment
of the deflection member;
Figure 3 is an axial cross-sectional view of the apparatus in the region of the deflection
member; and
Figure 4 is a transverse cross-section taken along the line 4-4 of Figure 3.
[0008] The relationship of a deflection member of this invention to the other parts of a
drilling apparatus is shown generally in Figure 1.
[0009] Figure 1 shows a drill shaft 10 connected to an orienting sub 11 and a down-hole
motor 12. Motor 12 is preferably a Moyno type fluid motor having a rotatable shaft
(not shown) extending through a shaft housing 14 and connected to drill bit 13. Shaft
housing 14 extends between motor 12 and bit 13. A deflection member 1 is mounted over
a section of shaft housing 14, and extends radially beyond shaft housing 14 at one
side. The portion of the deflection member extending beyond the shaft housing includes
a wall contacting surface 26 which contacts the wall of borehole 16 being drilled
through a mineral bed.
[0010] The drilling apparatus including the drill shaft orienting sub, motor, shaft housing
and drill bit is preferably of the type generally described in U.S. Patent No. 3,260,318.
This type of drilling apparatus, without the deflection member of this invention,
has been widely used in the drilling industry.
[0011] The details of the preferred version of the deflection member of this invention are
shown in Figures 2, 3 and 4.
[0012] Shaft housing 14 is machined to provide a reduced section including a top surface
17, sides 18 and 19, and bottom surface 20. Shaft housing 14 includes an internal
bore 29 through which a rotatable shaft (not shown) connecting the fluid motor and
the rotating drill bit extends. The main body element 21 of deflection member 15 is
formed to fit closely over sides 18 and 19 of the reduced section of shaft housing
14 and to be slidable with respect thereto. Recesses 22 and 23 in main body element
21 are provided for containing springs 24 and 25 which urge borehole wall-contacting
surface 26 of deflection member 15 radially outward from shaft housing 14. Bottom
body element 27 attaches to main body element 21 with fasteners 28 to encompass the
reduced section of shaft housing 14 and to compress springs 24 and 25. The deflection
force provided by the springs depends to some extent on the particular drilling apparatus
and the rate of direction change desired. When the borehole has a diameter of from
75 to 150 mm (preferably 75 to 100 mm) a deflection force of at least 225 newtons
is preferred. In order to provide the preferred rate of angle build of about 0.5°/3
m in a coal seam, a deflection force of 450 to 900 newtons is generally adequate.
[0013] Figures 3 and 4 show the assembled deflection member. When it is assembled and unrestrained,
the springs 24 and 25 act to position the deflection member so that the bottom body
element 27 abuts the bottom surface 20 of housing 14, and wall contacting surface
26 extends outwardly beyond the shaft housing 14 sufficiently to apply the desired
deflection force to the wall of a borehole during drilling.
[0014] The apparatus described above is particularly suited for drilling generally horizontal
degasification holes in underground coal seams to reduce the methane concentration
in a mine working area in advance of mining the seam. To be effective, the degasification
holes must be kept within the boundaries of the coal seam. The deflection member,
properly used, enables an operator to maintain the borehole between the upper and
lower boundaries of the coal seam.
[0015] The method of drilling a borehole in a mineral bed using the deflection member of
this invention will now be described. The drilling apparatus is set up, and after
drilling an initial surface hole a short distance into the seam, the apparatus as
shown in Figure 1 is inserted in the borehole and oriented with the wall-contacting
surface 26 of the deflection member oriented against either the top or the bottom
of the borehole. In order to guide the drill bit successfully and contain it in the
mineral bed, it is essential to know the position of the bit in relation to the roof
and the floor of the mineral bed and the pitch and roll of the borehole. Borehole
survey instruments which provide the required information are available. These instruments
may be pumped down the drill shaft to a position near the motor where they are positioned
by an orienting sub, and information as to the position of the borehole may be obtained.
The survey probe is then removed, and if a change in direction of the borehole is
indicated, the drill shaft is rotated through a part of a turn, thereby also rotating
the deflection member the same amount, and drilling is resumed. Normally, the deflection
member is oriented to provide either an upward or downward force to the drill bit,
although in some cases a side force may be indicated. If the borehole is moving upward,
and the surveying probe indicates that the borehole is near the top surface of the
mineral bed, the drill shaft and deflection member are rotated 180° to provide a downward
force to the drill bit. Drilling in resumed until the surveying probe indicates that
the borehole is approaching the bottom layer of the mineral bed, at which time the
drill shaft and deflection member are again rotated 180°. This procedure is repeated
until the borehole extends the desired distance into the mineral bed.
[0016] The deflection member in accordance with the invention has proven to be effective
in drilling degasification holes in coal seams in advance of mining. Several degasification
holes have been drilled through coal beds for distances greater than 300 meters, thereby
providing significant reductions in methane concentrations at the time of actual mining
of the coal bed.
1. Drilling apparatus comprising a down-hole motor (12), a rotatable shaft for connecting
said motor to a drill bit (13), a non-rotating housing (14) extending from said motor
over said shaft, and a deflection member (15) carried by said housing, said deflection
member (15) extending radially beyond said housing sufficiently to apply a deflection
force to the wall of a borehole during drilling and being movable perpendicularly
to the longitudinal axis of the housing, characterised in that the deflection force
is provided solely by spring means (24, 25) acting between part of the housing (14)
and the deflection member 15, the deflection member (15) being mounted on said housing
(14) in a manner to assure rotation of said deflection member corresponding to rotation
of said housing and that said spring means (24, 25) continuously urge a borehole wall
contacting surface (26) of the deflection member (15) away from one side of the housing
(14) and into engagement with the borehole wall with sufficient force to deflect the
trajectory of the borehole during drilling.
2. Apparatus as claimed in claim 1, characterised in that the deflection member (15)
comprises a main body element (21) adapted for sliding movement over side surfaces
of the housing, the borehole wall contacting surface being formed at the top of said
body element and the body element including recesses (22, 23) containing the spring
means (24, 25), there being a bottom body element (27) attached to the body element
(21) adapted to abut the bottom of the housing when the deflection member is in its
uppermost position relative to the housing (14).
3. Apparatus as claimed in claims 1 or 2, characterised in that the spring means comprise
a pair of coil springs (24, 25).
4. Apparatus as claimed in claim 3, characterised in that the pair of coil springs
(24, 25) provide a deflection force at at least 225 newtons.
5. Apparatus as claimed in claim 4, characterised in that the deflection force is
from 450 to 900 newtons.
1. Bohrapparat mit einem in einem Bohrloch nahe bei einem Bohrmeißel (13) angeordneten
Motor (12), mit einer drehbaren Welle zum Verbinden des Motors mit dem Bohrmeissel
(13), mit einem stillstehende Gehäuse (14), das sich von dem Motor aus über die Welle
erstreckt, und mit einem Ablenkelement (15), das von dem Gehäuse getragen ist, wobei
das Ablenkelement (15) so weit radial über das Gehäuse hinaus ragt, daß es während
des Bohrens eine Ablenkkraft auf die Wand des Bohrloches ausübt und es senkrecht zur
Längsachse des Gehäuses drehbar ist, dadurch gekennzeichnet, daß die Ablenkkraft allein
durch Federmittel (24, 25) erzeugt wird, die zwischen einem Teil des Gehäuses (14)
und dem Ablenkelement (15) wirken, daß das Ablenkelement (15) derart auf dem Gehäuse
(14) befestigt ist, daß die Drehung des Ablenkelement entsprechend der Drehung des
Gehäuses sichergestellt ist, und daß die Federmittel (24, 25) kontinuierlich eine
die Bohrlochwand kontaktierende Fläche (26) des Ablenkelements von einer Seite des
Gehäuses (14) fort und in Eingriff mit der Bohrlochwand mit einer Kraft drücken, die
ausreicht, die Trajektorie des Bohrlochs während des Bohrens abzulenken.
2. Apparat nach Anspruch 1, dadurch gekennzeichnet, daß das Ablenkelement (15) ein
Hauptkörperelement (21) aufweist, das für eine gleitende Bewegung über Seitenflächen
des Gehäuses ausgebildet ist, daß die die Bohrlochwand kontaktierende Fläche auf der
Oberseite des Körperelements (21) ausgebildet ist, und daß das Körperelement Vertiefungen
(22, 23) aufweist, welche die Federmittel (24, 25) enthalten, wobei ein Bodenkörperelement
(27) vorgesehen ist, das an dem Körperelement (21) angebracht und so ausgebildet ist,
daß es an dem Boden des Gehäuses anliegt, wenn sich das Ablenkelement in seiner obersten
Position relativ zum Gehäuse (14) befindet.
3. Apparat nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Federmittel ein
Paar Spiralfedern (24, 25) umfassen.
4. Apparat nach Anspruch 3, dadurch gekennzeichnet, daß das Paar Spiralfedern (24,
25) eine Ablenkkraft von wenigstens 225 Newton erzeugen.
5. Apparat nach Anspruch 4, dadurch gekennzeichnet, daß die Ablenkkraft 450 bis 900
Newton beträgt.
1. Appareil de forage comprenant un moteur de fond (12), un arbre rotatif destiné
à relier ledit moteur à un trépan (13), un carter non rotatif (14) qui s'étend à partir
de ce moteur en recouvrant ledit arbre, et un organe de déviation (15), porté par
ledit carter, ledit organe de déviation (15) s'étendant radialement au-delà du carter
sur une distance suffisante pour appliquer une force de déviation à la paroi d'un
trou de sonde pendant le forage et pouvant se déplacer perpendiculairement à l'axe
longitudinal du carter, caractérisé en ce que la force de déviation est développée
exclusivement par des moyens élastiques (24, 25) qui agissent entre une partie du
carter (14) et l'organe de déviation (15), l'organe de déviation (15) étant monté
sur ledit carter (14) de manière à provoquer une rotation dudit organe de déviation
qui correspond à la rotation dudit carter et en ce que lesdits moyens élastiques (24,
25) tendent continuellement à éloigner une surface (26) de l'organe de déviation (15)
qui entre en contact avec la paroi du trou de sonde d'un côté du carter (14) et à
la mettre en appui contre la paroi du trou de sonde avec une force suffisante pour
dévier la trajectoire du trou de sonde pendant le forage.
2. Appareil comme revendiqué dans la revendication 1, caractérisé en ce que l'organe
de déviation (15) comprend un élément principal de corps (21) adapté pour coulisser
sur des surfaces latérales du carter, la surface entrant en contact avec la paroi
du trou de sonde étant formée en haut dudit élément de corps, et l'élément de corps
présentant des évidements (22, 23) qui contiennent les moyens élastiques (24, 25),
un élément inférieur de corps (27) étant fixé à l'élément de corps (21 ) et adapté
pour buter contre le bas du carter lorsque l'organe de déviation est dans sa position
extrême supérieure par rapport au carter (14).
3. Appareil comme revendiqué dans les revendications 1 ou 2, caractérisé en ce que
les moyens élastiques comprennent une pair de ressorts à boudin (24, 25).
4. Appareil comme revendiqué dans la revendication 3, caractérisé en ce que la paire
de ressorts à boudin (24, 25) développe une force de déviation d'au moins 225 newtons.
5. Appareil comme revendiqué dans la revendication 5, caractérisé en ce que la force
de déviation est comprise entre 450 et 900 newtons.