Method and apparatus for acquiring and identifying multiple sidewall core samples

A method and apparatus for acquiring a plurality of sidewall cores from an earth formation intersected by a wellbore while a coring tool is located downhole. A sidewall coring tool is provided having an internal core receptacle for receiving and storing sidewall cores in serial orientation. The coring tool incorporates a movable bit box providing rotary support and linear coring and retracting movement of a rotary coring bit. A bit box tilting and rotation actuator is incorporated within the coring tool for achieving breaking at the core sample from the formation and for selectively positioning of the bit box and rotary coring bit at a coring position where the bit is oriented in normal relation with the axis of the wellbore and a core ejecting position where the rotary coring bit is positioned in registry with the internal core receptacle for deposit of cores in serially oriented relation therein. Another actuator is provided for accomplishing lateral coring and retracting movement of the rotary coring bit for acquiring a core and for retracting the bit and core within the coring tool. A third actuator is provided within the coring tool for displacing cores from the rotary coring bit into the core receptacle after the rotary coring bit has been positioned in registry with the core receptacle. A mechanism is also provided for locking the coring bit against inadvertent extension during bit box rotation. The sidewall coring mechanism further incorporates a reduction gear transmission permitting slow speed, high torque rotation of the coring bit, which transmission is automatically disengaged when the bit box is rotated from the coring position.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates generally to wireline apparatus for sidewall coring 
in well bores drilled for production of petroleum products. More 
particularly, the present invention relates to rotary sidewall coring 
apparatus for acquiring multiple sidewall cores while operating in the 
downhole environment and for depositing the cores within a core receiving 
receptacle in such manner that individual cores may be separately 
classified so as to be related to formation depth when subsequent analysis 
is performed. 
Discussion of Related Art 
It is common geophysical practice to collect cores from oil and gas bore 
holes at known depth for analyzing the core materials in order to 
determine various characteristics of the subterranean earth formation. 
Various sidewall coring apparatus has been developed and utilized for 
obtaining sidewall cores at selected depths. For the most part, however, 
these previous sidewall coring tools have the problem of easily stalling 
during coring activity because the coring bit thereof is typically 
operated by small high speed direct drive motors having only low torque 
capability. These types of coring tools typically have limitations that 
present a significant need which is effectively satisfied by the present 
invention. 
SUMMARY OF THE INVENTION 
It is a principle feature of the present invention to provide a novel 
sidewall coring tool which incorporates a coring box assembly which is 
selectively positionable in a coring position for generally normal 
orientation of a rotary coring bit with respect to the axis of the 
borehole and which is positioned in rotatable and linearly movable 
relation for coring into the sidewall of the wellbore and positionable in 
a core ejection position where cores taken from the formation can be 
ejected from the rotary coring bit and into a core containing receptacle. 
It is another feature of this invention to provide a sidewall coring tool 
mechanism having a drive motor and a rotary coring bit which are 
selectively interconnected in driving relation by a geared transmission 
which causes the drive motor to be engaged in rotheary driving relation 
with the rotary coring bit at the coring position thereof and disengaged 
from driving relation with the rotary coring bit at the core ejecting 
position of the bit. 
It is also a feature of this invention to provide a novel sidewall coring 
mechanism incorporating an automatic drilling feature which maximizes 
drilling capability and minimizes sticking of the bit while drilling. 
It is an even further feature of this invention to provide a novel sidewall 
coring tool having a rotary coring bit that provides for high torque, slow 
speed rotation of the rotary coring bit thereof to minimize heat 
generation during coring operations and to promote extensive service life 
thereof. 
It is also a feature of this invention to provide a novel sidewall coring 
tool incorporating a bit box assembly which is subject to compound 
rotational movement between its coring and core ejecting positions and 
which is tilted for breaking the core from the formation and which 
includes a bit box rotation actuation mechanism having an actuator arm 
pivot connection with the bit box which defines locked and unlocked 
positions relative thereto. 
It is also a novel feature of this invention to provide a method and 
apparatus for efficient recovery of multiple core samples from the 
sidewall formation of well bores. 
It is another feature of the present invention to provide a novel sidewall 
coring tool incorporating an internal bit closure element which is moved 
between open and closed positions relative to a bit opening in the housing 
in response to compound rotational movement of the bit box assembly of the 
tool. 
It is also a feature of this invention to provide a novel sidewall coring 
mechanism having a coring bit provided with a core retainer that permits 
linear retraction of the rotary bit while rotating or without rotation 
while the core remains connected to the formation, to thus permit the 
clearing of any debris build-up behind the bit which might cause it to 
stick in the sidewall formation. 
It is another feature of the present invention to provide a novel sidewall 
coring mechanism providing well service personnel with the capability of 
controlling individual coring tool functions such as bit rotation, bit box 
positioning, bit box tilt for core breaking, core ejection from the coring 
bit as well as coring bit extension and retraction. 
It is another feature of this invention to provide a novel sidewall coring 
mechanism which permits continuous monitoring of coring tool operation by 
operating personnel at the surface. 
Briefly, in accordance with a primary principle of the present invention, a 
sidewall coring tool for wireline use in an earth bore hole is provided 
which includes an elongate tool body adapted for movement within the 
borehole by a wireline cable or by any other tool conveyance means for 
positioning thereof at various selected well depths and locations and 
which defines therein a receptacle capable of receiving and storing 
multiple cores in such manner that the cores are subsequently identifiable 
in conjunction with the formation depth from which they were taken. The 
sidewall coring tool includes a decentralizing system incorporating two or 
more decentralizing arms which are mounted in the tool body on the 
opposite side of the body from which the rotary coring bit is advanced and 
which are pivotally movable to engage the wail of the bore hole and permit 
forcible positioning of the rotary coring bit side of the tool against the 
wail surface of the bore hole. This feature locates the coring tool in 
substantially immovable relation within the bore hole during the coring 
operation and permits maximum penetration of the rotary coring bit into 
the formation wail as each core sample is being acquired. 
To enable the acquisition of multiple sidewall cores, the sidewall coring 
tool includes an internal bit box structure which is positionable at a 
coring position being oriented such that the rotary coring bit therein is 
located in substantially normal relation with the axis of the bore hole 
and a core ejection position at which the rotary coring bit is positioned 
in substantial registry with the core receptacle of the coring tool body 
with its axis of rotation coincident with or parallel to the axis of the 
well bore. The bit box assembly is movable within the tool body in such a 
manner that it disengages a reduction gear transmission that drives the 
rotary coring bit and is rotated substantially 90.degree. by a compound 
rotational movement from the coring position to the core ejecting 
position. For controlling such compound rotational movement, a pair of 
linearly movable actuator plates are provided having cam slots which are 
tracked by orientation guide pins of the bit box during hydraulically 
energized downward and rotational movement of the bit box assembly while 
the actuator plates are held stationery at a bit box rotating position. A 
pair of bit box actuator mechanisms including a pair of actuator arms are 
provided for cooperatively applying downward force on the bit box assembly 
to induce its compound rotational movement. When the bit box assembly is 
secured at an immobilized position against internal positioning stops of 
the housing by upward force of the actuator arms the actuator plates are 
moved linearly to achieve linear bit movement for coring activity. For 
linear coring movement of the rotary coring bit and for linear core 
retraction movement the cam slots of the actuator plates include inclined 
substantially straight cam slot sections which are traversed by guide pins 
of a linearly movable bit block assembly within the bit box housing while 
the bit box housing is held stationary against internal positioning stops 
by the bit box actuators while the actuator plates are moved linearly by 
the plate actuator mechanism. For ejection of the cores from the rotary 
coring bit, the bit is oriented in registry with the core receptacle after 
which a core ejection plunger contained within the tool is moved through 
the central passage of the rotary coring bit to displace the core from the 
bit and into the core receptacle. The core receptacle is arranged in a 
manner permitting serial orientation of the cores so that the cores may be 
individually correlated with the well bore depth or location from which 
each core was taken.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1 a schematic illustration of the rotary sidewall 
coring tool of the present invention is illustrated generally at 10 as 
being positioned within a well bore 12 that is drilled into an earth 
formation 14. In FIGS. 1 and 2 the sidewall coring tool 10 is shown to be 
positioned within the well bore by means of a wireline 16 extending over a 
sheave 18 by a standard winch or hoist apparatus (not shown) which is a 
component part of a surface unit 20. It should be born in mind that the 
sidewall coring tool, especially in the case of deviated or horizontal 
well bores, may be positioned by coil tubing strings, by drill strings or 
by any other means of tool conveyance without departing from the spirit 
and scope of t invention. Electrical and hydraulic control of the sidewall 
coring tool is accomplished by selective manipulation of control elements 
of a control panel 22 by operating personnel. The coring tool includes a 
rotary and linearly movable sidewall coring bit 24 which is shown in FIG. 
1 at a retracted position within the tool housing in relation to a bit 
opening 26 in the tool housing of the sidewall coring tool. In FIG. 2 is 
shown upper and lower decentralizing locking arm pairs 28 and 30 
respectively which are located on the side of the tool generally opposite 
to the coring bit 24. The decentralizing arms are shown in the collapsed 
positions thereof in FIG. 1 and are shown extended in FIG. 2 for urging 
the coring tool into firm engagement with the bore hole wall so that the 
coring bit may be extended fully into the formation during coring. 
The coring tool 10 comprises three major sections, being an electrical and 
electrohydraulic section 32 in which the subsurface electrical components 
and circuits are located and within which certain apparatus for 
electrohydraulic actuation of the decentralizing arms and rotary coring 
bit assembly are located. The tool incorporates an intermediate coring 
section 34 which defines the opening 26 for the rotary coring bit 24 and 
which contains apparatus for selectively positioning and actuating the 
rotary coring bit for coring and core ejection. The coring tool 10 also 
incorporates a core receptacle section 36 which contains a core receiving 
tube within which the cores are deposited in serially oriented relation so 
that the formation depth from which they were taken can be determined at 
the time of analysis. 
Referring now to FIGS. 3 and 4, within the sidewall coring tool 10 is 
provided a bit box assembly shown generally at 40, within which the rotary 
coring bit 24 is mounted for rotation and linear movement between a fully 
retracted position where the coring bit 24 is fully contained within the 
bit box housing and a fully extended position as shown in FIG. 3 where the 
coring bit is extended through an opening 42 in a wall 44 of the bit box 
and into penetrating relation with the earth formation 46 to acquire a 
core 48. 
It is desirable to achieve substantially rotationally positioning of the 
bit box assembly 40 for positioning thereof at a coring position as shown 
in FIG. 3 and for positioning thereof at a core ejecting position as shown 
in FIG. 4. To accomplish such selective positioning of the bit box 
assembly and to ensure acquisition of large sidewall cores it has been 
found desirable to provide the bit box assembly with compound rotary 
motion to achieve the positioning set forth in FIGS. 3 and 4. This 
compound rotary motion is evidenced in the partial sectional and partial 
elevational views of FIGS. 5-7. A pair of spaced actuator plates 50 and 52 
are positioned for linear movement within the coring section 34 of the 
sidewall coring tool and are moveable linearly by respective hydraulic 
actuators connected thereto by means of respective operator shafts 54 and 
56. The operator shafts are adjustable with respect to the actuator plates 
by means of threaded adjustment elements 58 and 60, thus permitting 
precision adjustment of the actuator plates relative to the drive shafts 
54 and 56 of the hydraulic actuators 62 and (&gt;4. Internally the actuator 
plates 50 and 52 each define control cam slots 66 and 68, each having 
curved lower portions and straight and inclined upper portions. The facing 
internal surfaces of the actuator plates also define L-shaped elongate 
guide slots 70 and 72. The respective actuator slots 66 and 68 each 
receive guide pins such as shown at 74 which cooperate with the upper and 
lower actuators and with the cam slots of the actuator plates to 
selectively achieve compound rotation of the bit box assembly between its 
coring and core ejection positions and to achieve linear coring and 
retracting movement of the coring bit. These features will be discussed in 
greater detail herein below in connection with FIGS. 5-12. 
For efficient coring operations it is desirable that the bit box assembly 
be capable of immobilization within the coring tool during coring and core 
bit retraction and for core ejection it is desirable that the coring bit 
be locked at its fully retracted position against linear movement. To 
accomplish these features, a pair of actuator arms 76 and 78 have lower 
ends thereof movably connected to the upper portion of the bit box 
assembly 40 and with the upper portions thereof being secured by means of 
pivot pins 80 and 82 to pivot brackets 84 and 86. The pivot brackets are 
provided at the lower ends of respective actuator shafts 88 and 90 that 
receive forcible actuation from respective hydraulic actuators 92 and 94 
with which they are operatively connected. As shown in greater detail in 
FIGS. 10 and 11, in the exploded view of FIG. 15 and in the partial 
sectional views of FIGS. 16 and 17 the respective lower ends 96 and 98 of 
the actuator arms are in assembly with respective movable locking brackets 
100 and 102, each being movably received within respective bracket slots 
95 and 99 having respective actuator arm openings as shown at 101 having a 
locking depression 103 at the lower portion thereof as shown in FIG. 15 
which is located to receive a pivot pin 105 which receives a retainer 
screw 106 at the end thereof. The lower, generally circular pivot 
connector elements 96 and 98 of the actuator arms 76 and 78 each define 
elongate downwardly opening slots 97 having opposed guide recesses 99 
which receive the circular head of the retainer screw 106. For pivoting 
movement of the actuator arms relative to the bit box the elongate slots 
97 will be positioned as shown in FIG. 16 with respect to the pivot pin 
105. For non-pivoting relation these components will be positioned as 
shown in FIG. 17. With reference again to FIG. 15, the lower pivot 
connector ends 96 and 98 of the actuator arms each define generally 
circular bosses 107 which are received within the circular openings 101 of 
the locking brackets 100 and 102. The elongate open bottomed slots 97 
permit lost motion movement of the actuator arms and movable brackets 
within limits defined by the length of the elongate slots 97. When the 
pivot pins 105 are positioned at the upper ends of the slots 97, and are 
thus centralized with respect to the circular openings 101 of the locking 
brackets the actuator arms and bit box establish a pivotal relationship 
that permits the bit box to undergo its compound rotational movement as 
shown in FIGS. 5-7. Conversely, when the pivot pins are located within the 
lower portions of the slots 97, the pivot pins will also be located within 
the locking depressions 103 of the locking brackets, thus establishing a 
non-pivotal, locked relationship between the actuator arms and the bit 
box. T non-pivotal relationship is established to permit coring activity 
as shown in FIG. 17. 
A pair of leaf springs 108 and 110 are secured to the bit box body 
structure by means of screws 112 and 114, with the free ends of the leaf 
springs contacting and applying a downward force on the upwardly facing 
shoulders 116 of the movable bit locking brackets 100 and 102. The leaf 
springs each apply a downward force on the locking brackets which results 
in the application of respective upward forces on the bit box. Thus, when 
the actuator arms begin to be moved downwardly by the actuators, rather 
than floating freely within the housing, the bit box is urged by the leaf 
springs to remain stationary with relation of the tool body until arms 78 
and 76 reach their tilting position as shown in FIG. 10. This will 
position the bottom 117 of locking brackets against the driven gear 164 of 
the core bit 24 so that the bit box 154, the driven gear 164 and the bit 
24 are now locked in their retracted positions within the housing that is 
defined by the bit box structure as shown in FIG. 16 to prevent its 
inadvertent linear extension during compound rotary movement and during 
upward movement to the coring position of the bit box. Thus, when the 
actuator arms are moved upwardly, such as shown in FIGS. 11 and 16 the 
connectors 96 and 98 will be in pivotal relation with the bit box during 
an initial segment of upward actuator arm movement and then will become 
locked against pivotal movement relative to the bit box housing when the 
bit box reaches its coring position. When the upward force on the actuator 
arms is relaxed the leaf springs acting against the brackets 100 and 102 
will urge the bit box upwardly to the position shown in FIG. 10 to unlock 
the nonpivotal actuator arm connection with the bit box and permit 
pivoting of the actuator arms about the pivot pins 105. Thus the actuator 
arm connection with the bit box assembly accommodates the compound 
rotational movement that the bit box assembly undergoes in its transition 
between the coring and core ejection positions. This feature also permits 
bit box tilting for breaking the core away from the formation. 
At their upper portions the actuator arms 76 and 78 each define bifurcated 
projections 118 and 120 each defining laterally opening slots 122 and 124 
for receiving the respective actuator pins of a bit opening closure 
element to be discussed hereinbelow. When moved upwardly by upper 
actuators 92 and 94 the actuator arms apply upward force to the bit 
locking brackets 100 and 102 moving them to their bit unlocking positions 
with the pivot pins 105 being received within the locking depressions 103 
for locking the pivot connections relative to the bit box. Through the bit 
locking brackets the actuator arms urge the bit box housing upwardly 
against internal housing stops 125 and 127 as shown in FIG. 7. The housing 
stops may be adjustable if desired so that the bit box housing can be 
accurately positioned and securely stabilized for efficient coring. 
The bit box assembly illustrated generally at 40 defines a housing 
structure including a transverse bushing support member 126 and an end 
wall plate member 128 to which is secured a pair of sidewall members 130 
and 132 by means of retainer screws or bolts 134. The bit box housing also 
includes a bottom wail structure 136. The sidewalls 130 and 132 define 
rectangular openings 138 and 140 with rectangular opening 138 being 
defined in part by upper and lower parallel planer guide surfaces 142 and 
144 and with opening 140 being defined in part by upper and lower parallel 
planer guide surfaces 146 and 148 respectively. Likewise, the bottom wall 
136 of the bit box housing defines a generally rectangular opening 150. 
Thus, the bit box housing, defined by the side and end members and the 
bottom plate is generally in the form of a rectangular framework within 
which the rotary coring bit 24 is supported for rotatable and linear 
movement. The end plate 128 is provided with a bearing assembly 152 to 
provide the rotary coring bit 24 with efficient bearing support relative 
to the bit box housing structure. A linearly movable bit support block 154 
is received within a generally rectangular end opening 156 defined by the 
bit box housing and is provided with a bearing assembly for rotatable 
support of the coring bit 24 relative thereto. The bit support block 154 
is provided with opposed lateral guide projections 158 having the guide 
pins 74 projecting laterally therefrom for respective engagement within 
the cam slots 66 and 68 as mentioned above. The transverse or lateral 
guide projections 158 provide for guided linear movement of the bit 
support block and rotary coring bit within the bit box housing to thus 
provide for linear movement of the rotary coring bit as it is projected 
into or withdrawn from the sidewall formation of the wellbore during 
coring and core retrieving operations. The rotary coring bit 24 is 
provided with a circular formation cutting face 160 at one end for cutting 
into the formation during coring operations. At its opposite end, the 
rotary coring bit is provided with a core ejection opening 162 from which 
cores retrieved from the formation are ejected into a storage magazine 
provided therefor. The rotary coring bit also defines a pair of spaced 
weakened sections 163 and 165 which permit fracturing of the bit 24 in the 
event it should become stuck in the formation and cannot be fully 
retracted. Fracturing of the bit at either of these weakened 
circumferential areas is achieved simply by tilting the bit box to achieve 
application of lateral force on the core that is present within the rotary 
coring bit. 
In most cases, coring bits are provided with core catchers which 
automatically grip the core when the bit is moved in a direction for 
extraction of the core from the formation. In t case, linear cycling of 
the coring bit to clear accumulated debris cannot be done. In accordance 
with this invention the coring bit defines an internal core retainer 
groove within which is located a split ring type spring retainer 166 which 
establishes frictional gripping of the core sample but which permits 
relative linear movement of the coring bit. The split ring core retainer 
will slip relative to the core so that the bit can be linearly cycled for 
clearing of accumulated debris. When the core is broken away from the 
formation by controlled tilting of the bit box the retainer will secure 
the core within the bit and ensure its extraction from the formation and 
will readily release the core when it is ejected from the coring bit by 
the core ejector. 
For high torque, low speed rotation of the coring bit 24 a driven pinion 
gear 164 of large diameter is fixed in non-rotatable relation with the 
rotary coring bit. The driven pinion gear 164 establishes driven geared 
relation with an elongate idler pinion gear 166 which is journaled for 
free rotation by bushing supporting pivotal block sections 168 and 170 
which are provided respectively by the end member 126 and the end wall 128 
of the bit box housing. The elongate idler gear is disposed for selective 
geared engagement with a drive pinion gear 172 which is supported for 
driving rotation by the output drive shaft 174 of a drive motor 176 that 
is fixed within the coring tool body structure. The elongate pinion gear 
166 permits the driving relationship between it and the driven gear 164 to 
be maintained as the rotary coring bit and its driven gear are moved 
linearly for coring and core retraction as the bit support block 154 is 
moved laterally by reaction of the guide pins 74 with the upper, inclined 
portions of the cam slots 66 and 68. Preferably, the drive motor 176 is a 
hydraulically energized rotary motor; however, in the alternative, the 
rotary drive motor may be energized electrically or by any other suitable 
means. 
To permit the drive motor to have high torque capability and to enable the 
coring bit to retrieve cores in all types of earth formations the drive 
motor is separate from the rotary coring bit and is connected in driving 
relation with the bit only when the bit and its bit box housing are 
oriented for coring. As shown in FIG. 12 the drive pinion gear is 
positioned in driving relation with the elongate idler gear 166. This 
condition is established when the bit box assembly is oriented in coring 
position, with the rotary coring bit 24 oriented in substantially normal 
relation with the axis of the well bore. When the bit box assembly is 
oriented at its core ejecting position as shown in FIG. 4 with axis of 
rotation of the rotary coring bit in substantially coaxial relation with 
the axis of the wellbore, the elongate idler gear 166 will have been moved 
to its disengaged relation with the drive pinion gear 172 thus releasing 
or declutching the drive relation of the drive motor 176 with the rotary 
coring bit. The drive pinion gear 172, the idler pinion gear 166 and the 
driven pinion gear 164 cooperate to define a geared motor output speed 
reduction transmission which, because of the much greater diameter of the 
driven pinion gear relative to the idler pinion gear and the drive pinion 
gear, establishes a high torque, relatively slow rotational relationship 
between the output shaft of the drive motor and the rotary coring bit. 
This relationship causes the rotary coring bit to be rotated at slow speed 
with high torque thereby permitting efficient coring operations while at 
the same time maintaining efficient cooling of the cutting face 160 of the 
rotary coring bit so that its service life is quite long as compared to 
conventional coring bits which are for the most part coupled in directly 
driven relation with the output shaft of a drive motor. The declutching 
relationship of the elongate idler pinion gear 166 relative to the drive 
pinion gear 172 is evident from the operational views shown in FIGS. 5, 6, 
and 7. 
With reference particularly to FIGS. 5-7 the bit box assembly 40 is shown 
in FIG. 5 in its core ejection position which is also shown in FIG. 4. In 
FIG. 6 the bit box assembly is shown during its compound motion between 
the core ejecting position of FIG. 5 and the coring position of FIG. 7. In 
the coring position, with the bit box housing forced upwardly against the 
housing stops 125 and 127, the rotary coring bit 24 is shown to be 
positioned in registry with an opening 178 in the wall structure 180 of 
the intermediate housing section 34. For coring operations the rotary 
coring bit 24, while being continuously rotated by the motor through the 
engaged pinion gears of the transmission, is moved linearly through the 
housing opening 178 and into the formation against which the housing is 
tightly positioned by the decentralizing arms 28 and 30. 
When coring operations are not being conducted it is desirable to close the 
coring bit opening 178 of the tool housing to prevent large drill cuttings 
and other debris from entering the coring tool housing and potentially 
fouling the rotary coring mechanism. To accomplish t feature a closure 
element 182 is movably positioned within the housing section 34 and 
defines an opening 184 which is positioned in registry with the housing 
opening 178 in the coring position of the core box assembly as shown in 
FIG. 7. For accomplishing controlled movement of the closure member 182 
between its open and closed positions relative to the bit opening 178, as 
shown in FIG. 7, the closure member is provided at its upper end with a 
pair of laterally extending drive projections 186 each having drive pins 
188 which are received respectively within the laterally opening drive 
slots 122 and 124 of the actuator arms 76 and 78. Thus, as the actuator 
arms 76 and 78 are moved upwardly and downwardly for controlled rotary 
actuation of the bit box assembly between the positions of FIGS. 5, 6, and 
7, the closure member 182 is correspondingly moved to block the housing 
opening 178 as shown in FIG. 5 and to move the closure to a position where 
its opening 184 is in registry with the housing opening 178 when the bit 
box assembly has reached its coring position. FIG. 6 illustrates the 
position of the coring box assembly and the closure 182 at a transitional 
position intermediate, the core ejection position of FIG. 5 and the coring 
position of FIG. 7. Thus, when coring operations are not being conducted, 
the housing opening 178 is closed and entry of relatively large foreign 
matter such as drill cuttings into the coring tool housing is minimized to 
the point that it does not constitute a problem from the standpoint of 
coring tool operations. 
One of the important features of the present invention is declutching of 
the pinion gear transmission between the drive motor and the rotary coring 
bit. This feature is also evident from the operational views of FIGS. 5, 
6, and 7. As shown in FIG. 7 with the bit box assembly at its coring 
position, the drive pinion gear 172 is in geared driving engagement with 
the idler pinion gear 166. As the bit box assembly begins its compound 
rotation or translation from the coring position of FIG. 7 the idler 
pinion gear 166 is moved out of driven relation with the drive pinion gear 
172 as shown in FIG. 6 while maintaining its driving relation with the 
driven pinion gear 164. In FIG. 5 the idler pinion gear is shown to have 
been positioned with its axis of rotation disposed in substantially 
90.degree. offset position relative to its position as shown in FIG. 7. 
Provision of t transmission declutching arrangement permits a large high 
torque drive motor, which is stationary within the coring tool housing, to 
be utilized for coring operations. Normally, the limited housing space 
that is available for sidewall coring operations requires a direct bit 
driving motor to be of fairly small dimension and requires that it be 
coupled in a direct driving relation with the rotary coring bit. This 
direct driving relationship typically requires the rotary coring bit to be 
driven at high speed so that in many cases it develops extensive heat 
during coring operations, thus rapidly wearing the coring bit and 
significantly detracting from its service life. In accordance with the 
present invention, the high torque low speed geared transmission 
arrangement allows the rotary coring bit 24 to be rotated at slow speed 
with high torque so that heat build up during coring is held at a minimum 
and its service life is significantly longer as compared to that of 
conventional sidewall coring mechanisms. This high torque feature also 
allows the bit to penetrate difficult formations without stalling often. 
With the coring box assembly 40 positioned at its core ejection position as 
shown in FIGS. 4 and 5, it is desirable to eject a core that has been 
taken from the sidewall formation of the wellbore and to eject into 
downwardly into the core storage receptacle 55. For core ejection as shown 
in FIG. 4 a core ejection plunger 190 is movably supported within the 
housing structure of the sidewall coring tool by means of an operator 
shaft 192 which is driven linearly by the piston 194 of a core ejection 
hydraulic actuator 196. The core ejection plunger can be operated only 
when the bit box is positioned at its core ejection position. 
It is desirable to ensure optimum drilling capability of the rotary coring 
bit 24. However, in the event the coring bit encounters a drilling 
condition in the formation where the torque provided to its hydraulic 
drive motor become lower than is desired, the bit may reach a point where 
it is about to stall in the formation. When this condition occurs, it is 
desirable to minimize the drilling force on the drill bit, thereby 
permitting its substantially free rotation and thus, preventing stalling 
from occurring. As shown in the schematic illustration of FIG. 13, a 
rotary hydraulic drilling motor 200 having its output shaft driving the 
drive gear 172 of the reduction gear transmission gear described above, 
receives hydraulic actuating pressure via a hydraulic circuit 202 from a 
hydraulic pump 204 driven by an electric motor 206. The hydraulic pump 
receives its supply from a hydraulic supply 208 and has its discharge line 
2 10 coupled in driving relation with the bit drive motor 200 across a 
two-way solenoid valve 212. The discharge pressure of the pump is in 
communication with a pilot line 214, the pressure of which is controlled 
by a pressure relief valve 216. The pilot line is coupled to the pilot 
side 218 of an adjustable sequence valve 220 having a closed state as 
shown at 222 in FIG. 13 and an open state as shown in 224 in FIG. 14. 
NORMAL CORING MODE 
When hydraulic fluid flow under pressure is supplied to hydraulic motor 200 
in the CW condition the hydraulic fluid output from the two way valve 212 
is also applied to the pilot side 218 of sequence valve 220. If the 
hydraulic pressure provided is lower than a preset adjustment of the 
sequence valve pilot 218 the sequence valve will remain closed and there 
will be no communication between the input side 219 and the output side 
221 of the sequence valve. Thus, the hydraulic line 223 connected from 
input 219 to point "B", which is the piston side of hydraulic cylinder 62 
will not have a flow of fluid therein. 
As mentioned above, the rotary coring bit 24 is moved linearly during 
extension and retracting movement by linear actuation of the actuator 
plates 50 and 52. For purposes of simplicity, only actuator plate 50 is 
shown in FIGS. 13 and 14. The linear force applied to the actuator plate 
50 through the shaft 54 by hydraulic pressure in the hydraulic actuator 
62, which acts upon the actuator piston 63, acting through the guide pin 
74, controls the force of the rotary coring bit 24 against the formation 
being cored. For selective actuation of the hydraulic cylinder 62, a line 
226 is coupled with the piston shaft side of the hydraulic actuator while 
line 228 is coupled with the piston side of the actuator. Hydraulic 
pressure to the cylinder 62 is controlled by a hydraulic supply pump 230 
being driven by an electric motor 232 and having its discharge conducted 
across a four-way solenoid valve 224 for supplying and permitting 
discharge of pressure from the respective chambers of the cylinder 
actuator 62. The solenoid control valve is coupled across pressure relief 
valves 236 and 238 which permit flow within the cylinder supply and return 
lines 226 and 228. 
BY-PASS MODE 
If the coring bit 24 encounters a coring condition where the torque 
provided to hydraulic motor 200 by the hydraulic pump 204 is near its 
maximum, then the bit will be near the point where it is about to stall. 
At t time, the oil pressure at point "C.revreaction. increases. When the 
oil pressure reaches the preset value of pilot 218 it will cause the input 
219 to connect to the output 221 of the sequence valve as shown in FIG. 
14. This will cause oil from the pilot check valve 238 to flow through the 
bypass line 223 and through the sequence valve 220 to the receiving tank 
209, thereby decreasing pressure that is ordinarily applied, in the coring 
mode, through actuator line 226 to the shaft side of the actuator piston 
63. This action has the effect of canceling the force on the bit 24 
allowing it to be turned freely by the motor 200, without the load that is 
normally applied to it by the piston actuator 62. At this time, pressure 
at point "C" decreases since the load on the bit has decreased, thus 
causing the pilot 218 of sequence valve 220 to interrupt the oil flow from 
point "B" to the bypass tank 209. Since this activity removes the stalling 
force the hydraulic pressure to pilot 218 will decrease below the preset 
pilot pressure and the sequence valve will be returned to the normal, 
coring mode of FIG. 13. 
AUTOMATIC CORING 
While drilling (coring) if the force applied to the bit by the bit drive 
motor 200 is too high, the bit will cease to turn and the oil will bypass 
the linear hydraulic actuator motor 62 as described above regarding the 
bypass mode. But if the force applied to the bit is too small, the bit 
will not penetrate the formation. This means that the force applied to the 
bit (bit load) must be constantly adjusted for the optimum drilling 
condition. This is almost impossible to execute manually from the surface. 
An automatic system has been incorporated into the sidewall coring tool of 
this invention to accomplish this result without necessitating manual 
attention. 
Under normal coring conditions the control system will be in the normal 
coring mode of FIG. 13, with pump pressure driving the rotary motor and 
driving the actuator plates downwardly to advance the bit into the 
formation. When the bit force becomes excessive the system will 
automatically switch to the bypass mode of FIG. 14, thus deenergizing the 
actuator 62 and relieving the bit force. 
Under conditions where the rotary bit drive motor 200 is about to stall, 
the pilot pressure in line 214 will begin to increase as the pilot 
pressure sensed by pilot 218 reaches the preset pilot pressure of thee 
adjustable pilot, the normally closed sequence valve 200 will change from 
its closed state 222 to its open state 224. In its open state, fluid 
pressure in the by-pass line 223 will be conducted through the sequence 
valve to the hydraulic reservoir, thus relieving the pressure on supply 
line 226 so that the piston 63 ceases its downward hydraulic actuation and 
thus, the rotary coring bit 24 ceases its linear extension force against 
the formation. Under t condition, the rotary coring bit 24 can be freely 
rotated by the bit drive motor 200. T freely rotating condition of the 
coring bit causes the pilot pressure in line 224 to diminish below the 
pre-set pressure level of the pilot 218. This causes the sequence valve 
220 to return to its closed state as shown in 222, thus ceasing flow in 
the by-pass line 223 and again permitting the pump pressure to act through 
line 226 on the stem side of the piston 63, thus driving it downwardly as 
shown in FIG. 13 and causing extension actuation of the rotary bit 24 by 
downward actuation of the actuator plate 50 so that its angulated slot 
reacts against the guide pin 74 for developing and advancing force on the 
rotary coring bit. 
Thus, it can be seen that the rotary coring bit is provided with an 
automatic, pressure responsive capability which removes the advancing 
force in the event it is about to stall and restores the advancing force 
when the stalling position has depleted. The coring bit, therefore, is 
driven against the formation in a manner that achieves optimum bit 
penetration and yet, prevents stalling of the bit if stalling conditions 
are present. This automatic drilling hydraulic circuitry enables optimum 
drilling of the rotary coring bit without requiring any significant degree 
of attention by service personnel. 
All of the various functions of the sidewall coring mechanism are capable 
of being controlled and monitored individually from the surface. Since the 
functions can be individually controlled operating personnel can alter the 
sequence of sidewall coring events, according to the various conditions of 
the bore hole, the formation being cored, and conditions of the coring bit 
itself. For example, to prevent any undesired build-up of debris behind 
the coring bit as it penetrates will into the formation, it may be 
desirable to cycle the coring bit back and forth between its coring and 
partially retracted positions. As the core bit is retracted, while being 
rotated, or while non-rotated, any debris build-up behind the coring face 
of the bit is displaced into the well bore so that it does not interfere 
with operation of the bit. In some circumstances, t debris could become 
sufficiently extensive that the coring bit may not be withdrawn from the 
bore hole. This disadvantage is effectively overcome by providing 
operating personnel with the capability of individually controlling cyclic 
extension and retracting of the core bit for periodic displacement of 
coring debris which could interfere with coring or core retraction as 
coring operations are conducted. As the coring bit is linearly cycled in 
this manner the split ring retainer simply slides along the length of the 
core without interfering with bit movement. 
The present invention effectively provides operating personnel with the 
capability of monitoring and individually controlling many different 
coring functions from the surface. Operating personnel are provided with a 
visual readout at monitor 23, while coring, of the voltage at the surface, 
voltage at the tool head and the electrical current being supplied to the 
coring tool. There is also provided a monitor readout of the pressure of 
hydraulic fluid at the tool head as an indication of the torque being 
experienced by the bit drive motor for coring bit rotation and the 
pressure of hydraulic fluid for auxiliary hydraulic functions such as 
hydraulic actuator operation for bit box positioning. The monitor 23 
provides a display capability for bit load as coring progresses, rate of 
bit penetration, depth of coring bit penetration, elapsed time of coring 
activity and estimated time for each coring procedure. The positions of 
various components of the sidewall coring tool are also visually presented 
by the monitor to enable operating personnel to very closely monitor tool 
operation and determine that selected functions are being carried out. For 
example, the monitor 23 will visually display the bit box position and bit 
location relative to the bit box as well as angle of bit box tilting for 
core breakage. The position of the core ejecting rod is also visually 
displayed. 
OPERATION 
The sidewall coring tool of the present invention is run into the well bore 
by means of conventional wireline equipment as indicated above and is both 
run and retrieved relative to the wellbore with the bit box assembly 
positioned in its core ejecting position as shown in FIG. 5 and with the 
closure 182 at its closed position. Upon being positioned at a selected 
location within the well bore the decentralizing arms 28 and 30 are 
energized thus forcing the sidewall coring tool laterally such that its 
coring side is disposed in tight engagement with the wellbore wall and 
with the core bit opening 178 in juxtaposition relation with the formation 
to be cored. At this point the bit box assembly is moved for the core 
ejection position of FIG. 5 by compound rotational movement and is 
positioned for coring as shown in FIG. 7. This is accomplished by first 
rotating the bit box assembly to its coring position and then immobilizing 
the bit box housing within the tool. The rotational activity is 
accomplished by upwardly energizing the actuator arms 76 and 78 by means 
of the hydraulic cylinders 92 and 94 thus providing an upward force on the 
bit box assembly through the lost motion connection defined between 
actuator arm connectors 96 and 98 and the movable bit locking brackets 100 
and 102 and the respective movable relationships thereof relative to the 
actuator slots 104 and the actuator pivot pins or screws 106. At the bit 
box position of FIG. 5 the pivot pin 105 will be centered within the 
circular opening 101 of the locking brackets so that the bit box is 
unlocked and freely pivotal relative to the actuator arms 76 and 78. As 
upward force is applied to the bit box housing through the connectors 
96-98, the pivot pins 105 and the bit unlocking brackets 100-102, the 
guide pins 75 will function essentially as pivots while guide pins 74 will 
traverse the lower curved portions of the guide slots 66 and 68. Thus the 
bit box assembly will undergo compound rotational movement as evidenced by 
FIG. 6 which is determined cooperatively by the L-shaped guide slots 72 
and the lower curved portions of the guide slots 66 and 68. 
After reaching the position of FIG. 7 the bit box housing must be 
immobilized within the tool housing so that no coring box movement occurs 
as the coring bit is rotated and extended into the formation. Also, the 
rotary coring bit must be unlocked so that it can be extended linearly 
during its rotation. Bit box immobilization occurs as further upward force 
of the actuators 92 and 94 urge the locking brackets and bit box housing 
upwardly so that the housing seats on and becomes stabilized by the 
internal downwardly facing stops 125 and 127. When t occurs that bit box 
housing becomes essentially fixed within the coring tool housing. After 
the bit box housing has engaged the tops 125 and 127 the locking brackets 
are moved upwardly to the extent permitted by the length of the actuator 
arm connector slots 97 as shown in FIG. 17 thus moving the lower portion 
of the locking brackets upwardly to positions clearing he driven gear 164 
and thus releasing the coring-bit 24 for linear movement. Upward movement 
of the locking brackets relative to the seated bit box preloads the leaf 
springs 108 and 110 so that, when the upward force on the locking brackets 
and bit box is subsequently relieved, the springs will again position the 
bit box housing at its bit locking position relative to the locking 
brackets. 
In FIGS. 5-7 the relative positions of the guide pins 74 and the lower 
curved portions of the guide slots 66 and 68 are clearly evident. The 
various positions of the guide pins 74 relative to the guide slots is 
depicted by solid line and broken line positions, the solid lines of the 
guide pins indicating the respective actual positions of the guide pins 
relative to the guide slots at the bit box housing position shown in FIGS. 
5, 6, and 7. During this upward movement of the actuator arms 76 and 78 
the actuator arms will pivot about the pivot pins 80 and 82 and will also 
pivot about the pivot pins 105. This pivoting arrangement is necessary to 
permit the compound rotational movement that is induced by the bit box 
housing structure during correlation of the guide slots at various 
rotational positions. 
As mentioned above, during compound rotation of the bit box assembly from 
the FIG. 5 position of the FIG. 7 position the elongate idler gear 166 is 
separated from the drive pinion gears 172, thereby declutching the drive 
transmission between the drive motor 176 and the driven gear 164 of the 
rotary coring bit. The transmission between the drive motor and coring bit 
is engaged only when the bit box is seated against the housing stops 125 
and 127. 
During compound rotation of the bit box assembly as shown in FIGS. 5-7 the 
actuator plates 50 and 52 will be maintained substantially fixed within 
the coring tool housing, being supported by the actuator shafts 54 and 56 
of the hydraulic actuators 62 and 64. After compound rotation of the bit 
box assembly has achieved immobilized coring positioning of the bit box 
assembly as shown in FIG. 7 the lower hydraulic actuators 62 and 64 will 
be energized thereby inducing downward movement of the actuator plates 50 
and 52 while the bit box hosing remains immobilized by its seating against 
the stops 125 and 127 as indicated above. T downward actuator plate 
movement causes the guide pins 74 to traverse the straight, inclined upper 
section of the guide slots and thus accomplishes linear driving of the bit 
block assembly 154 through the guide pins 74 of lateral projections 158. 
This causes the guide projections 158 to move linearly within the bit box 
housing being guided by the upper and lower guide surfaces of the 
rectangular side plate openings and thus causes the rotary coring bit 24 
to be moved linearly into the formation while it is rotated by the drive 
motor through the geared transmission. The drive motor 176 is energized 
during lateral driving of the rotary coring bit so that the cutting face 
of the coring bit cuts into the formation and achieves a core within the 
coring bit passage 161. During linear coring movement of the coring bit 24 
the driven pinion gear 164 traverses the length of the elongate idler gear 
166 while maintaining geared driving relation therewith. The actuator 
plates 50 and 52 will be driven downwardly by the lower hydraulic 
actuators until the guide pins 74 will have reached the uppermost portions 
of the guide slots 66 and 68. At this position, the rotary coring bit 24 
will have been fully extended and will have completed its coring 
operation. 
After coring has been completed it is necessary to separate the core sample 
from the formation. This is best done by applying lateral force to the 
core while the core bit is fully extended, thus breaking the core sample 
from the formation at a point near the cutting face 160 of the bit. When 
the core breaks in this manner the split ting retainer will secure the 
core sample in immovable relation within the bit passage 161 so that the 
core sample cannot remain in the formation during bit retraction and 
cannot interfere with bit box movement during rotation of the bit box 
toward its core ejecting position. 
After a core sample has been acquired in t manner the lower hydraulic 
actuators 62 and 64 will be energized to drive the actuator plates 50 and 
52 upwardly, thereby causing the guide pins 74 to again traverse the upper 
inclined portions of the actuator slots 66 and 68, thereby shifting the 
bearing block 154, its guide projections 158 and the rotary coring bit to 
its fully retracted position as shown in FIG. 7. Thereafter, with the 
lower actuators 62 and 64 deenergized, and securing the actuator plates in 
their immovable bit box rotating positions, the upper actuators will again 
be energized so as to apply a downward force on the actuator arms 76 and 
78 with the coring bit fully retracted as shown in FIG. 16, causes 
unlocking movement of the locking brackets 100 and 102 form the FIG. 17 
positions thereof toward the FIG. 16 positions. As the brackets move 
downwardly the leaf springs, applying the preload spring force between the 
brackets and bit box housing, will shift the bit box and brackets so as to 
center the pivot pin 105 within the circular bracket openings 101, thus 
unlocking the actuator arms from the bit box so that the connection 
therebetween will become pivotal. Thus, downward movement of the actuator 
arms and locking brackets unseats the bit box housing from the 
immobilization stops 125 and 127 and shifts the bit locking brackets 
downwardly to engage behind the driven gear 164 and lock the coring bit 24 
at its retracted position in readiness for pivoting. Further downward 
force on the bit box housing then causes the guide pins 74 to traverse the 
lower arcuate portions of the guide slots 66 and 68 thereby inducing 
compound rotation to the bit box assembly through the position shown in 
FIG. 6 to the core ejecting position shown in FIG. 5. 
After the position of FIG. 5 has been reached the core 48 is ejected from 
the passage 161 of the rotary coring bit through the core ejection opening 
162 by the core ejection plunger 190 under the influence of downward force 
applied by the hydraulic actuator 196 through the plunger drive shaft 192. 
The split ring core retainer will allow the core to slip through it as its 
frictional retaining force on the core sample is overcome by the force of 
the core ejection plunger. After reaching this position a coring operating 
cycle will have been completed, and a core will have been received by the 
core storage receptacle 55. The core storage receptacle may be of any 
character appropriate for positioning multiple cores in serially oriented 
manner so that upon retrieval from the wellbore each of the cores may be 
correctly associated with the formation depth from which it was taken. As 
shown in the drawings the core receptacle may comprise an elongate tube 55 
of sufficient length to retain a desired number of core samples. 
As mentioned above, the rotary coring bit 24 is moved linearly during 
extension and retracting movement by linear actuation of the actuator 
plates 50 and 52. For purposes of simplicity, only actuator plate 50 is 
shown in FIGS. 15 and 14. The linear force applied to the actuator plate 
50 through the shaft 54 by hydraulic pressure in the hydraulic actuator 
62, which acts upon the actuator piston 63, acting through the guide pin 
74 controls the force of the rotary coring bit 24 against the formation 
being cored. For selective actuation of the hydraulic cylinder 62, a line 
226 is coupled with the piston shaft side of the hydraulic actuator while 
line 228 is coupled with the piston side of the actuator. Hydraulic 
pressure to the cylinder 62 is controlled by a hydraulic supply pump 230 
being driven by an electric motor 232 and having its discharge conducted 
across a four-way solenoid valve for supplying and preventing discharge 
from the respective chambers of the cylinder actuator 62. The solenoid 
control valve is coupled across pressure relief valves 236 and 238 which 
permit flow within the cylinder supply and return lines 226 and 228. 
Many modifications and variations besides those specifically mentioned may 
be made without substantially departing from the concept of the present 
invention. Accordingly, it should be clearly understood that the forms of 
the invention described and illustrated herein are exemplary only and are 
not intended as limitations on the scope of the present invention.