Core separator assembly

An assembly for dispensing a core separator ring on the top of a previously-cut core that is ejected from a core-cutting bit in a storage bin. The core separator assembly is integral with the forward end of the core ejector system.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention is concerned with a wireline tool for cutting, retrieving 
and separating retrieved sidewall core samples from a borehole. 
2. Discussion of Related Art 
Core samples are plugs of the native rock cut from the rock formations at 
depth levels of interest. The structure, composition and texture of the 
rock formations as evidenced by the core samples are of quantitative 
analytical interest to miners, civil engineers, petrophysicists, 
geologists, oceanographers and other earth scientists. 
Boreholes penetrating the earth are drilled for many different purposes, 
such as water wells, oil and gas wells, brine recovery wells, and 
foundation studies. Ordinarily, the drilling process particulates and 
contaminates the rock formations that are penetrated by the drill so that 
the drill cuttings themselves are of limited use analytically. For that 
reason, special tools have been developed for cutting cores from the 
living rock at selected depth levels, often in the borehole sidewall after 
the borehole has been drilled. 
In days of yore, a plurality of hollow punch-core bits were loaded in 
barrels mounted in an elongated coring tool. The bits are aimed 
perpendicularly to the borehole sidewall and distributed at selected 
intervals longitudinally along a mandrel one or two tens of feet long. 
Each of the bits was secured to the mandrel by a short flexible cable. The 
mandrel comprising the coring tool was lowered to a desired depth from a 
wireline whereupon explosive charges were triggered behind the respective 
core bits, driving them into the sidewall. A core sample was retained in 
the hollow bit after detonation. The coring tool was then recovered from 
the borehole after breaking loose from the sidewall, the plurality of 
punch-core bits and heir contained core samples. Verification of the core 
sequence was assured because each core was resident in a physically 
separate core bin which was secured to the coring tool by the attached 
cable so that the relative depth of each core in the sequence was 
positively known. A missing core was readily detectable by simple 
inspection. 
There were problems with explosively-driven punch-coring tools, not the 
least of which was the need for use of explosives, a hazardous 
proposition. 
A different type of wireline coring tool is in use that employs a hollow 
rotary coring bit that is mounted in a housing fitted in the mandrel of a 
down-hole wireline coring tool. The housing comprises an assembly 
including means for laterally extending a rotating cutting bit into, and 
retracting the bit from a borehole sidewall. Upon retraction, following 
the core-cutting operation, the bit is rotated 90.degree. whereupon a push 
rod shoves the cut core out of the bit into a storage tube. The storage 
tube is mounted longitudinally with respect to the mandrel, beneath the 
housing containing the cutting bit. A typical sidewall core is about an 
inch in diameter and about one-and-one half to two inches long. After the 
first core is cut, the coring tool is moved up the borehole to a new 
location where another core is cut and stored in the core storage tube. 
The process is repeated until the storage tube is full, perhaps acquiring 
twenty or more cores per downhole trip. 
One such arrangement is taught in U.S. patent application Ser. No. 
08/146,441, filed Oct. 29, 1993 in the name of Jacques Maissa et al., 
assigned to the assignee of this invention, and now U.S. Pat. No. 
5,411,106, issued May 2, 1995, which is incorporated herein by reference. 
It is preferable that the respective cores residing in the storage tube be 
physically separated from one another. Additionally, completion of a 
particular sidewall coring operation does not necessarily result in 
successful recovery of a core. Therefore the core sequence must be 
properly indexed such the non-existence of one or more cores can be 
positively verified. 
U.S. Pat. No. 5,310,013, issued May 10, 1994 to A. C. Kishino et al. 
discloses means for placing an indexing marker above each recovered core. 
No indication of a missing core appears to be provided for. 
U.S. Pat. No. 4,714,119, issued Dec. 22, 1987 to Joel Hebert et al. also 
provides means for inserting a marker disc between the recovered cores. 
Both of the above patents employ a tubular reservoir of marker discs that 
are urged upwards by a pusher spring. A separate tubular core storage bin 
is mounted beside to marker reservoir. After a core is deposited in the 
core storage bin, a system of levers shoves a marker disc laterally from 
the open upper end of the marker reservoir to the mouth of the storage 
bin. Somehow a magnetic solenoid at the top of the storage bin, captures 
the marker disc (which is magnetic) so that it will fall on top of the 
previously-deposited core. The mechanical arrangement of the two 
references is deemed to be far too complicated to be practical. 
U.S. Pat. No. 4,449,593, issued May 22, 1984, to Gary D. Bruce et al. also 
teaches use of indexing washers to separate core samples. Here again, 
Bruce's system involves a separate storage bin for the marker discs and a 
lever system for shoving the marker into the core storage bin. 
In all three of the above patent references, the marker disc must in some 
way fall into place rather than be firmly deposited in place. 
There is a need for a mechanically simple, reliable means for positively 
dispensing core a separator between individual cores during a core storage 
operation. 
SUMMARY OF THE INVENTION 
This invention provides a novel core separating assembly in combination 
with a sidewall coring tool. The novel combination includes a hollow 
core-cutting bit that may be disposed in either a core cutting position or 
in a core storage position. When the core cutting bit is in the core 
storage position, a hydraulically-actuated core ejector executes a core 
ejection stroke to push the core from the core cutting bit into a core 
storage tube. The leading end of the core ejector includes a 
hydraulically-operated, integral core separator assembly. The core 
separator assembly consists of a mandrel over which a plurality of 
separator rings are concentrically stacked. After a core has been 
deposited in the core storage tube, a cam means releases a single core 
separator ring for positive disposition on top of the deposited core 
before the core ejector executes a return stroke prior to disposing the 
cutting bit to the core cutting position. The process is repeated a 
plurality of times until the plurality of stacked core-separator rings is 
exhausted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows a coring tool 10 suspended in a borehole 11, having a sidewall 
12 in a selected earth formation 14, from a wireline 16 engaging a sheave 
18 associated with a surface control unit 20 on the surface of the earth 
22. Surface unit 20 includes means for controlling and programming the 
necessary functions of coring tool 10 by sending electronic signals 
through a standard 7-conductor-plus-stress-member logging cable 16 as is 
well known to the art. Coring tool 10 includes a core cutting bit 24, 
shown in the retracted position from bit opening 26 in the core cutting 
tool. Coring tool includes caliper arms 28 and 30 for locking the tool 
against the sidewall 12 of a borehole 11 as shown in FIG. 2. Coring tool 
10 may include separate sections such as 32 wherein is contained 
electronics control modules 33 as well as means 35 for providing hydraulic 
power for operating the caliper arms 28 and 30, core cutting bit 24 and 
other equipment to be explained later. Section 34 includes the mechanisms 
that control the functions of the core cutting bit and core ejector 
assemblies. Section 36 may include ancillary equipment, none of which is 
pertinent to this disclosure. 
FIG. 2 shows coring tool 10 locked in position opposite an earth formation 
3 of interest and above an uninteresting earth formation 39. Core cutting 
bit 24 is shown extended laterally through bit opening 26 in the side of 
coring tool 10 to cut a core from formation 37. 
Please refer now to FIGS. 3 and 4 which taken together are intended to show 
the general schema of the core-cutting/core-storage bit-position 
mechanization to show how the core separator assembly of this invention 
interacts in combination with a core-cutting operation. A detailed 
mechanical exegesis of the bit extension and bit retraction system itself, 
usually some form of slotted cam-plate arrangement as taught by any one of 
the references earlier cited, is not presented here to avoid prolixity and 
undue complexity of the drawings since such details are not germane to 
this invention. 
FIGS. 3 and 4 represent a longitudinal cross section of section 34 of 
coring tool 10 showing the core cutting bit assembly 40, the core ejector 
assembly 42, the core separator assembly 44 and the core storage bin 46, 
all resident inside the cylindrical wall 39 of section 34. 
In FIG. 3, the cutting bit assembly 40 is shown in the core-cutting 
position, extending through bit opening 26 where a core 48 is being cut 
from earth formation 37. The core ejector assembly 42 is withdrawn. The 
core-cutting bit assembly 40 includes bit 24, a bit housing 50 and a 
hollow hydraulically or electrically operated motor and transmission 
means, symbolically shown as 51, for rotating coring bit 24 during 
core-cutting operations. 
Core ejector assembly 42 includes a double-acting hydraulic cylinder 52, 
piston rod 54 and core separator assembly 44 which is integral with the 
forward end of the ejector as represented by the core ejector piston rod 
54. Core separator assembly 44 includes a number of separator rings, the 
lowermost of which is designated by the reference numeral 57. Further 
details of core separator assembly 44 will be explained in detail later in 
connection with FIGS. 5-7. As also will be explained later, certain 
members internal to core separator assembly 44 are in fluid communication 
with pressurized hydraulic fluid provided by hydraulic source 35 to 
cylinder 52 in core separator assembly 44 via a passageway in piston rod 
54. 
Core storage bin 46 is a tube 56 of suitable length to hold a plurality of 
cores; the tube has a diameter commensurate with the diameter of the cut 
cores. Tube 56 is shown holding a previously-cut core 49, upon the top of 
which reposes a core separator ring 58 that was positively deposited 
thereon from a previous core-cutting cycle. 
In FIG. 4, after a core 48 has been cut and broken loose from formation 37, 
cutting bit assembly 40 is retracted from the core-cutting position and 
rotated to the core-storage position by means not shown, with the core 
assembly disposed vertically, that is, parallel to the longitudinal axis 
of coring tool 10, over the core storage bin 46. Assuming that the core 
material is not friable, the newly-cut core 48 is frictionally retained in 
the core-cutting bit by a retaining ring (not shown) during the bit 
retraction cycle. After the core cutting bit assembly is in the 
core-storage position, core ejector 42 is activated by the surface control 
system 20 to extend piston rod 54 with the core separator assembly 44 
integral with the forward end thereof, thereby to push the cut core 48 out 
of bit 24 and into storage bin 46 on top of the previously-cut core 49 and 
core separator ring 58. After core ejection, but before core ejector 
piston rod 54 is retracted., the hydraulic system that operates cylinder 
52 is slightly over-pressured to cause core separator assembly 44 to 
positively deposit the lowermost separator ring 57 directly on the top of 
core 48. By use of that stratagem, that is, by direct positive deposit, 
the separator ring is not obliged to tumble down by gravity free-fall 
through viscous drilling mud in storage tube 56 before coming to rest, 
perhaps awry, on a core sample far below in the storage tube, as was done 
in known prior-art tools. 
Please now refer to FIGS. 5 and 6. Core separator assembly includes a 
compression sub 60 having an internal pressure chamber 62 for containing 
an actuator rod 64. Compression sub 60 is threadedly coupled to core 
separator mandrel 66 that has a longitudinal slot 68 cut along a portion 
of its length. The mandrel is terminated by an end plate 71. An actuator 
ring 70 is mounted externally around mandrel 66 with a sliding fit. A 
guide pin 72, into which the forward end of actuator rod 64 is screwed, 
transfers the motion of the internally-mounted actuator rod 64 to the 
externally mounted actuator ring 70 through slot 68. A grease fitting 74 
is provided for lubrication. 0-rings 76 and 78 along with 0-ring backup 80 
seal compression chamber 62 around actuator rod 64. 
At the right-hand end of core separator assembly 44, that is, at the 
forward end, a stack of Belleville springs 81 are mounted between spring 
plate 82 and spacer end cap 84. The Belleville springs are held in place 
by spacer 86 that is mounted interiorly to mandrel 66 and pressed snugly 
against the springs 81 by compression sub 60. The springs are separated by 
thin washers such as 88. 
Referring now to FIGS. 5 and 7, the right hand forward end of mandrel 66 
includes a pair of sprockets 90 and 92 that are mounted on opposite sides 
of the forward end of the mandrel 66. Since the sprockets are 
substantially identical, only one will be described in detail with 
particular reference to the enlarged drawing of FIG. 7. The sprockets each 
have a cam member such as 94 that is loaded by the force of the Belleville 
springs 81 through spring plate 82. The sprockets are rotatable about axes 
such as 96 that are transverse to the longitudinal axis of the mandrel. 
The sprockets 90 and 92 each have a first tooth such as 98 and a second 
tooth such as 100. A plurality of core separator rings, of which the 
lowermost ring is shown as 57, are stacked externally around the mandrel, 
using a generous sliding fit, between the sprockets 90 and 92 and actuator 
ring 70. The core separator rings are held in place by the first tooth 
such as 98 of each of the sprockets 90 and 92 while the sprockets are in 
the cocked position. 
In a presently preferred embodiment, mandrel 66 has a capacity for 20 
separator rings. 
Spring-loaded cam member such as 94 of each sprocket normally maintains the 
sprockets in the cocked position as shown, against the hydraulic pressure 
that may be resident in compression sub 60. The spring force is adjusted 
to exceed, by a small selected increment, the total force exerted by 
actuator piston rod 64 at normal system operating pressure. At the normal 
system operating pressure of 2000 psi, the force exerted by the piston is 
about 80 pounds. The spring force is adjusted by adding or removing one of 
the Belleville springs or by adjusting the length of spacer 86 or both. 
In the best mode of operation, to deposit a separator ring on a 
previously-ejected and stored core, the hydraulic pressure applied to 
actuator rod 64 is raised to the relief pressure of 2300 psi, thus 
allowing actuator piston 64 to exert an applied force increment of about 
10 pounds. Actuator piston, through guide pin 72 and actuator ring 70 
pushes lowermost separator ring 57 against the first tooth 98 of sprocket 
90 and similarly for sprocket 92. The force applied to core separator ring 
57 causes the sprockets to rotate because the applied force overcomes the 
opposing force exerted by the spring-loaded cam member 94 of sprocket 90 
and similarly for sprocket 92. Rotation of the sprockets causes the first 
tooth to retract, thereby allowing lowermost separator ring to be released 
from mandrel 66. At the same time, second tooth 100 emerges to trap the 
next separator ring in line, 104. No additional amount of incremental 
force will allow the sprockets to rotate further because a stop surface of 
a sprocket such as 102 contacts the inner edge of end plate 71 and 
therefore can rotate no farther. Therefore only one ring at a time is 
released by core separator assembly 44. Release of the incremental 
pressure, allows the spring system 81 to recock itself for a new cycle. 
To continue the best mode of operation, following a complete cycle of core 
cutting, core ejection and core storage, the core cutting tool is ready to 
be moved to a new location up the borehole by first releasing caliper arms 
28 an 30 (FIGS. 1 and 2). At the new location, the caliper arms are again 
extended. At that time, the afore-mentioned over pressuring operation is 
performed to positively deposit a separator ring on the stored core. The 
core ejector 42 is then withdrawn preparatory for a new core-cutting 
cycle. That particular sequence of operations is preferred because, in the 
event that a core is not recovered for some reason, the cycle of events 
just enumerated will still take place but with the result that two 
separator rings instead of one will be deposited on the previously-stored 
core. In that manner, the operators have positive knowledge of the depth 
sequence of the respective cores. 
The novel features of this invention have been described with a certain 
degree of particularity by way of example but not by way of limitation. 
Variations of this invention will become apparent to those skilled ion the 
art but which will fall within the scope and spirit of this invention 
which is limited only by the appended claims.