US2769615A - Core recovery apparatus - Google Patents

Description

Nov. 6, 1956 G. BURGESS 2,769,615

' CORE RECOVERY APPARATUS Filed April 6, 1953 P m A I g 2 27 29 h l I f I 1.33 1' k; l 2 14 I E [8'1] I w l3 l9 [I g L i 2| 26 FIG. 4 B INVENTOR. 24 BY GERALD BURGESS I I ATTORNEY United States Patent Ofifice CORE RECOVERY APPARATUS Gerald Burgess, Casper, Wyo. Application April 6, 1953, Serial No. 346,840

4 Claims. (Cl. 25572) This invention relates to core recovery apparatus and more particularly to a core barrel by which successive cores may be recovered without removing the drill string from the well.

In drilling wells to attempt to locate a deposit of oil or gas, so-called cable tool drilling, in which a bit is reciprocated upwardly and downwardly at the bottom of a hole by a cable, has many limitations, and has been largely replaced by rotary bit drilling. Furthermore, since a sudden entry of the hole into an oil or gas deposit under considerable pressure has, in the past, often resulted in a blow-out, with a consequent loss of tools and other equipment and sometimes a hazardous fire, it is now customary to pump mud down the bore such mud being generally a slurry or suspension of certain clays and other materials to provide adequate weight. Thus, the hydrostatic head of the column of weighted mud in the bore is depended upon to produce sufiicient pressure to prevent gas at high pressure from blowing out the well. In addition, pump pressure may also be added to the natural hydrostatic head to increase the pressure of the mud atthe bottom of the bore. However, due to the mud pressure forcing mud into the well bore, it is sometimes possible for the bore to be drilled completely through a productive stratum, without the driller knowing it. Of course, the mud and the cuttings may be analyzed at every few feet of drilling, to minimize the possibility of passing through a valuable stratum, but the best information relative to the stratum being drilled through is obtained from a solid sample of the stratum itself. Thus, it is customary, Whenever other evidence indicates the desirability thereof, or particularly in wildcat wells, whenever there is a possibility of the bore approaching or passing through either a productive stratum or a geological marker, to take a core. A .core is usually obtained by drilling with an annular diamond bit, and pulling up the column of stratum left in the middle. It is possible, of course, to attach a core bit to the lower end of the drill string, lower the drill string into the hole, drill downwardly for the desired distance, and then pull the drill string to pull the core up with it, the lower'end of the drill string being provided with a device for pulling the core up with it. However, the time consumed in putting down and pulling up the drill string for each core renders such coring operations expensive, and increasingly expensive as the depth of the bore increases. Thus, it is desirable to use a removable core barrel or receptacle for the core, such a core barrel generally being removed from the well by a wire line. Previous removable core barrels have produced difficulties in operation and inadequacy in results, such as poor recovery due to blocking, undue wear of parts, and have involved unduly complicated parts. In addition, often a complete core has been thought to have been taken, but when the core barrel is retrieved, very little core specimen is obtained.

Among the objects of this invention are to provide a novel core drilling apparatus, including a novel core barrel; to provide such apparatus which enables successive cores to be taken with relative ease; to provide such apparatus which tends to insure that complete cores will be recovered; to provide such apparatus, during the use of which an indication may be given to the driller when ditficulty is being encountered below; to provide such apparatus which is simple in construction; to provide a novel core barrel which may be moved up the drill string by either a wire line or by reverse mud circulation; and to provide such a core barrel which is effective and efllcient in operation.

Additional objects and the novel features of this invention will become apparent from the description which follows, taken in connection with the accompanying drawing, in which:

Fig. l is a condensed, vertical section of the lower end of a drill string embodying core recovery apparatus constructed in accordance with this invention;

Fig. 2 is a fragmentary vertical section taken adjacent the upper end of the core barrel and illustrating a difierent position of the same;

Fig. 3 is a transverse sectiontaken along line 33 of Fig. 1, adjacent the lower end thereof;

Fig. 4 is an enlarged fragmentary vertical section taken at the lower end of a top sub forming apart of the apparatus of Fig. l; and

Fig. 5 is an enlarged, partial vertical section taken at the lower end of the apparatus.

As illustrated in the drawing, core recovery apparatus constructed in accordance with this invention may be attached to the lower end of the lowermost section 10 of drill pipe, and may include an upper sub S connected to the lower end of the drill pipe section 10, as by threads 11, an outer tube 12 connected to the lower end of the upper sub S, as by threads 13, and a drill bit B, in turn attached to the lower end of the outer tube 12, as by threads 14. A removable core barrel, which is hollow and open at the lower end, is disposed within the assembly thus described, and may comprise a head H, normally disposed adjacent the upper sub S, an inner tube 15 connected to the lower end of the head H, as by threads 16, and a lower guide G, connected to the lower end of inner tube 15, as by threads 17. In addition, the core barrel may be provided with an annular core recovery spring 18, disposed Within the lower guide G and provided with a series of lugs 19, which engage the lower end of inner tube 15 and prevent the spring 18 from moving upwardly within the core barrel along with the core. Of course, the spring 18 permits the core to move up into the barrel as drilling proceeds downwardly.

In accordance with this invention, the sub S is provided adjacent its lower end with a series or" radially spaced, inwardly extending wings 20, which form slots 21 therebetween, as in Fig. 4, and which maintain the core barrel particles of diamonds or the like, the matrix 24 extendingacross the bottom and up both the inside and the outside of the lower end of the bit B. A series of radially spaced slots 25, as in Fig. 3, may extend down the outside ofthe matrix 24, and also across the bottom and up the inside. As will be evident from Fig. 3, each of the holes 23 preferably terminates at one of the slots 25 in the diamond matrix 24. The bit B may further be provided with a seat 26 for the lower end of guide G.

During the normal drilling of a core, the parts willv be disposed in substantially the position shown in Fig. 1,

Patented Nov. 6, 1956' in which the main "body of the head H of the core barrel isdisposedwithinthe series of-inwardly-extending wings 20 and the guide G'is disposed within Wings 22. 'The normal circulation of mud :will bedown throughthe sub'S, pastthe head of 'H of the core barrel, through slots 2j1' between the Wings' ZO, thence downwardly through aniannular'space 27,fbetween;the outer tube 1 2 andtheinner'ttibe 15, through the slots "between lower Wing's 22,j which surround -the guide G at the lower end of the core barrel, and finally through discharge holes 2310 the bottom of the bit 'B.

' In furtheraccord'ance with this invention, a generally annular, enlarged or choke section 30 is formed infsub S immediately abovethe wingsZtl with a section--29 of restrictedcross-sectional area immediately above.' The cross-sectional area ofhead H corresponds to the crosssectional 'area of restricted'sec'tion 291, preferably just slightly less, and the choke section 30 is normally disfill to a marked degree the requirements and objects,

hereinbefore set forth; As will be evident, the section of larger cross-sectionalarea, such as the choke section V 30 and the section of 'lesser cross-sectional area immediately thereabove, cooperate with .a movable. core barrel which is normally positioned so. as not to interfere with the flow of mud through'the'section of reduced posed adjacent a tapering neckI31 of head H of the core barrel. Also, head H may "be provided with an upwardly extending'passage 32, which leads from. a point on the outside of. the body of the head H normally justb'elow. wings '20, to the upper end of a central passage 33, which extends downwardly within head H to the interior space within inner tube 15. An initial flow of 'mud through passages 32 and 33 may provide internal flushing for the core barrel, thus tending to prevent the core from becoming jammed with n the inner tube against cuttings or other harder material. As the core moves upwardly in the barrel, the downward direction of passage 32 on the outside,.assists in permitting the .mud trapped within the barrel to be easily forced out of the barrel by the core, thereby permitting afull core tobe taken. Also, a wire line recovery head 34 may be formed integrally with the head H or remov V ably attached thereto. 7

'As will be evident, as coring proceeds, the parts of the apparatus tend to stay in the'position of. Fig. l, the

core entering'the inner tube '15 of the barrel, as the bit B rotates and cuts an annular hole deeper. When the maximum length of core has been taken, or in the event that the core becomes jammed or misaligned within the barrel, the core barrel will be prevented from moving downwardly as the bit B moves downwardly, so that the 'head H of the barrel will move to the position of Fig. 2,

In position, instead of the tapered neck 31 being opposite ,the choke section 30, the larger,'main body of the head'H willbe within thechoke section 30, and

"the flow past the core barrel will be considerably restricted. As will be evident, the head H is still within theguide wings when the flow is so restricted. This will be reflected, at the top of the well, in anincrease in the pressure necessary to maintain mud circulation, thereby indicating to the drillerthat the core barrel has moved upwardly within the sub S. If the difiiculty cannot be overcome by shiftingthe drill stem, or other stratagems, or if depth measurement indicates that the full length of core has been taken, the core barrel may be retrieved, as by reversing mud circulation to push the core barrel. up to the top of the drill string, in which event a. suitable catcher for the core barrel, as

.ofconventional construction, is provided at the top of the drillstring. Or, a wire line and recovery tool may be run: down thevdrill string, for'engagement with the wire line recovery head34 provided at the top of head H of the 'core barrel. After the recovery of one core, the core. barrel ma'y be dropped back into the drill string and moved down with the mud, ;or may be lowered by a wire line, so that another core may be taken without undue time delay. A s willbe evident, a number of cores maybe taken in succession, with the timerequired for-movement of the core barrel to and from the surface being held to a minimum. This 'i'sa particular advantage in exploratory drilling, wherein long sections of 'thewell are often cored continuously. 'If desired, suitable cross-sectional area, and thereby 'indicate'to the driller when the core barrel has moved upwardly in'the drill stem, in addition to indicate that the core may be jammed or that some other undesirable event has occurred. The

lack of such an indication further furnishes information to the driller, i. e. that coring is proceeding in thep desired manner. In addition to the quickness'and ease with which the core barrel may be movedbetween bottom hole and the collar,-the simplicity of construction'of the coring apparatus of 'thisinvention not only "reduces the V initialj'c'ost, but'also the upkeep due to wear. [The 'parts involved are held together by conventional'threaded 'connections, which permit ready assembly and disassembly, and there are no complicated mechanical con V V nections which were'forrnerly thought necessary to attach siderably.

1 corebarrel is free to rotate in the drill stem, thereby a-corebarrel to a drill'stem. The mud flowing down past;the barrel also'tendsto. maintain it in position,

section 30, when the pressure of mud will'increase conthe. passages leading to theinterior of the barrel tend'to clean the core asit enters the'barrel, while the passages also permit'the mud trappedin the barrel to be forced outYby the rising core. As will also be evident, the

damage to the core, and'tending to assure that cores .of maximumdiameter will be taken.

Although-specific embodiment of'this inventionhas been.illustra-ted and described with particularity, it will be understood that other embodiments may exist and that 7 various. changes may be made therein, all without departingfrom the: spin'tfand scope of this invention. Whatis claimed is: I i 1. In core drilling apparatus, including an'outer tube,

, a hollow bit at the lower end of said tube, and -a hollow core barrel open at its lower end and disposed :within said tube, the improvement wherein said tube includes agenerally cylindrical sub threadedly attachableto the,

lower end of a section of drill-pipe, a cylindrical tube; threadedlyattachable :to'the lower endof said sub, and

a generally cylindrical drill bit threadedly attachable to. the lower end of said cylindrical tube; said sub having anupper section of restricted cross-sectional area, an intermediate section of greater cross-sectional area and a lower section having a plurality of integral, inwardly extending wings, the. diameter at the inneredges of'said' I said drill bit-having-a plurality of inwardly extending" wings whose inner diameter corresponds to thediameter wings corresponding to the diameter at said section of. restrictedfarea; said cylindrical tube having an inner diameter 'greater than said section of restricted area;

at said section of restricted area, an annular seat below said. bit wings for the lower end of said core barrel, a'

plurality-ofpassages leading from spaces between said bit wings to the lower end of said bit, and relatively harddrilling material attached to the inside below said seat, to the bottom and to the outside of said bit; and said core barrel having a cross-sectional area corresponding to said restricted area and being normally disposed below *said restricted area but movable upwardly tosaid restricted area to reduce the cross-sectional area availablefor flow of fluid downwardly past said core barrel.

-As. indicated, the flushing action provided by 2. In core drilling apparatus, including an outer tube, a hollow bit at the lower end of said tube, and a hollow core barrel open at its lower end and disposed within said tube and movable upwardly and downwardly within said tube, the improvement wherein said outer tube is provided with a wall defining a fluid passage having a section of restricted cross-sectional area above a section of greater cross-sectional area, said wall being provided with a plurality of inwardly extending wings below said section of greater cross-sectional area, said wings having a greater longitudinal extent than said section of greater cross sectional area, said bit also having inwardly extending wings and the diameter at the inner edges of said Wings corresponding to the diameter at said restricted area, and said core barrel having an outer diameter corresponding to said restricted area and being normally disposed below said restricted area but movable upwardly by the core to said restricted area to reduce the cross-sectional area available for flow of fluid downwardly past said core barrel.

3. In core drilling apparatus, including an outer tube, a hollow bit at the lower end of said tube, and a hollow core barrel open at its lower end and disposed within said tube and movable upwardly and downwardly within said tube, the improvement wherein said tube is provided with a wall defining a fluid passage having a section of restricted cross-sectional area above a section of greater cross-sectional area, said wall having a plurality of inwardly extending wings below said section of greater cross-sectional area, the diameter at the inner edges of said wings corresponding to the diameter at said section of restricted area; and said core barrel having at least adjacent its upper end a diameter corresponding to said restricted area and being normally disposed below said restricted area but movable upwardly by the core to said restricted area to reduce the cross-sectional area available for flow of fluid downwardly past said core barrel, said upper portion of said core barrel having suflicient longitudinal extent that a portion thereof is still Within said wings when the cross-sectional area available for flow is reduced.

4. In core drilling apparatus, a hollow bit at the lower end of including an outer tube, said tube, and a hollow core barrel open at its lower end and disposed within said tube, the improvement wherein said outer tube is provided with a wall defining a fluid passage having a section of restricted cross-sectional area above a section of greater cross-sectional area; said core barrel includes a generally irnperforate head, an inner tube threadedly attached to the lower end of said head, a generally cylindrical guide threadedly attached to the lower end of said inner tube and an annular core spring having outwardly extending lugs and disposed within said guide; said head having a generally solid cylindrical section, a frustoconical neck thereabove tapering upwardly and a wire line recovery pin at the upper end, said neck being nor- ".ally disposed opposite said outer tube section of greater crosssectional area and said wire line pin being normally disposed opposite said section of restricted crosssectional area; said cylindrical section of said head having a diameter corresponding to said outer tube section or" restricted cross-sectional area so that upon upward movement of said core barrel said cylindrical section will move upwardly to said section of restricted area to reduce the area available for flow of fluid downwardly past said core barrel; said cylindrical section of said head also having a central passage extending to the interior of said core barrel and an upwardly inclined passage leading fIOIll the outside thereto adjacent the lower end to the upper end of said central passage; and said guide being constructed and arranged to form a space beneath the lower end of said inner tube to receive said outwardly extending lugs of said core spring, said lugs engaging the lower end of said inner tube to restrict upward movement of said core spring.

I References Cited in the file of this patent UNITED STATES PATENTS 2,164,598 Thrift July 4, 1939 2,189,057 Copelin Feb. 6, 1940 2,234,264 Lang Mar. 11, 1941 2,347,726 Auld et a1. May 2, 1944 2,357,907 Phillips Sept. 12, 1944 2,565,101 Taylor Aug. 21, 1951 2,621,897 Brown Dec. 16, 1952

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