US2927776A

US2927776A - Coring apparatus

Info

Publication number: US2927776A
Application number: US719931A
Authority: US
Inventors: Alexander B Hildebrandt; Harold C Bridwell
Original assignee: Jersey Production Research Co
Current assignee: Jersey Production Research Co
Priority date: 1958-03-07
Filing date: 1958-03-07
Publication date: 1960-03-08
Anticipated expiration: 1977-03-08

Description

5 Sheets-Sheet 1 CORING APPARATUS 9 m 2 url f 1/ 2 WK 4 f n li.

A. B. HILDEBRANDT ETAL March 8, 1960 Filed March 7, 195s Inventors Alexander B. Hildebrandt Harold C. Bridwell 2,927,776 Patented Mar. 8, 1960 ice CORING APPARATUS Alexander B. Hildebrandt and Harold C. Bridwell, Tulsa,

Okla., assignors, by mesne assignments, to Jersey Production Research Company Application March 7, 1958, Serial No. 719,931 7 Claims. (Cl. Z55-72) This invention is concerned with an improved apparaytus for securing cores from subterranean formations. `The apparatus of the invention is particularly character- "ized by its ability to obtain representative cores from sandy or other unconsolidated formations. The invention is particularly adapted for coring operations that are performed in conjunction with well-drilling operations.

i In prospecting and drilling for oil and other mineral deposits, it is a conventional procedure to determine eriodically the character and nature of the substrata hrough which a well or borehole is being drilled. One .rqnethod lies in cutting cores from the substrata at particulr selected depths,`"thereafter removing the cores to the surface of the earth and analyzing them for the purposes stated. Many procedures and apparatus have been developed, for this purpose, and it has been a continuing object of such procedures and apparatus to obtain as rep- 'esentative cores as possible.

In general, coring apparatus and procedures employ core bits which drill an annular-type hole, leaving a center core which is broken off and taken to the earths surface by various means. For the most part, a core enters a core-receiving barrel where it is retained by means of a ,device called a core catcher. The core-receiving barrel is supported by means of a swivel from a rotating outer :barrel to. which the core bit is attached. The swivel enables the core-receiving barrel to remain stationary during a coring operation, with the result that twisting of the; core is reduced.

Hereto'fore in the art, and in spite of continuous study and Work, a problem has existed with respect to securing representative cores in all types of formations. With respectto cemented sands and other consolidated structures, the problem has not been overly acute. However, uncemented sands and other unconsolidated formations .,g., broken formations), it has been very dicult to secure representative cores wherein the grains of the cores are undisturbed with respect to one another. It will be recognized that non-disturbance of the grains in a core is necessary if accurate permeability and porosity measurements as well as the orientation o-f the core are to be determined.

Heretofore in the art, it has been the practice-as mentioned above-to use a core-receiving barrel to receive and retain a core after it has been cut by a coring bit. Conventional core-receiving barrels are in effect rigid steel sleeves, and they employ spring-actuated vcatchers or the like to retain a core therein.

While core-receiving barrels of the type just described are reasonably satisfactory in coring Well-consolidated structures, they are not very satisfactory in coring unconsolidated or loosely cemented structures. Cores from unconsolidated structures tend to bridge and jam within a barrel, and this effectively precludes long cores from being, obtained. General experience has shown that a core if 111 an unconsolidated formation cannot be pushed very f3 ,into a Steel tube-type core barrel before the material ofl'the core will not sustain its own weight. Accordingly,

itk has been the practice in coring such a formation to be satisfied with securing cores of relatively short length. This condition has been manifestly undesirable, but until recently little or no progress in overcoming this limitation has been realized. A new type of coring apparatus ernploying a rubber or other elastic sleeve which encases a core as soon as it is cut has proven to be quite valuable n this service. Coi-ing apparatus emplo-ying this principle are described and claimed in a co-pending application, Serial No. 701,840, filed December l0, 1957, in the name of A. B. Hildebrandt.

The present apparatus, like the apparatus described in the Hildebrandt patent application, supra, makes use of a rotary-type core barrel which has a rotatable outer barrel and a stationary core-receiving barrel. The outer barrel and a coring bit attached to the lower end thereof are supported from the lower end of 'a string of drill pipe in a co-rotatable and longitudinally slidable relation. A hydraulic push-down or feed-off arrangement is preferably interposed between the drill pipe and the outer barrel and uses the pressure of down-flowing drilling lluid within the drill string to push the outer barrel downward relative to the drill string. Splines or equivalent means interconnect the outer barrel to the drill string-directly or indirectly*to permit the outer barrel to move longitudinally relative to the drill string while still rotating with the drill string.

In a preferred form of this invention, an intermediate barrel is fastened to and within the outer barrel so as to define an annular passageway therebetween. The lower end of this intermediate barrel is sealed around its lower periphery to the inner periphery of the coring bit. Drilling fluid owing down through the outer barrel can thereby pass directly to drilling-fluid passageways or ports within the coring bit Without irst contacting any portion of the core cut by the bit.

A core-receiving barrel is detachably and rotatably supported at its upper end within and from the intermediate barrel. An annular space is defined between the inner surface of the intermediate barrel and the outer surface of the core-receiving barrel; and a radially stretchable, flexible, preferably duid-impermeable sleeve is positioned within this space. This sleeve is mounted or supported upon the outer surface of the core-receiving barrel; and it extends from the bottom of the annular space around the lower end of the core-receiving barrel, whence it is attached to a plug element which is movable longitudinally within the barrel. The lower end of the corereceiving barrel is spaced from the coring bit to enable the sleeve to move freely around the end of the barrel. Rollers are preferably mounted around the lower end of the core-receiving barrel to promote ready movement of the sleeve in this region.

In a preferred form of the invention, the core-encasing sleeve is mounted on the outer surface of the corereceiving barrel such that the sleeve is folded back over itself-both ends of the sleeve being disposed toward the bottom of the barrel. The outermost layer of the folded sleeve is the one attached to the aforementioned plug element, with the result that downward movement of the barrels causes the sleeve to be peeled off the outer surface of the core-receiving barrel. A lubricating uid -e.g., viscous drilling mud-is preferably inserted between the layers of the folded sleeve to promote a sliding movement therebetween.

An important feature of the invention is the inclusion of means for effecting a continuous pressure balance between the interior of the core-receiving barrel and the annular space between this barrel and the intermediate barrel. A convenient and satisfactory device for this purpose can be one or more passageways penetrating the wall of the core-receiving barrel-preferably near the upper end thereof.

The plug element is supported directly or indirectly from the drill pipe by means of an elongated rod. This rod is attached at its lo-wer end to the plug element, and it is supported at its upper end from the drill pipe. Rotational movement between the drill pipe and the plug element is provided by means of a swivel joint inserted at any convenient place within the rod-supporting structure. Since the rod must necessarily pass upward through the intermediate barrel and the core-receiving barrel, a suitable sealing device is interposed between the rod and the intermediate barrel or the core-receiving barrel to prevent drilling liuid from entering the core-receiving barrel from the outer core barrel. The sealing device is conveniently a packing gland which enables the required longitudinal and/ or rotational movement to occur between the rod and the surrounding barrel structure at the point of sealing.

Returning to thesleeve portion of the invention, it is necessary that the sleeve be radially stretchable and flexible. The sleeve should also be impermeable to iiuids, and it should be reinforced longitudinally to prevent any longitudinal stretching. The unstretched inner diameter of the sleeve is preferably preselected to be somewhat smaller than the outer diameter of a core to be cut by an apparatus using the sleeve. Thus, as the sleeve encases the core, it exerts a compressive force upon the core and holds it securely so as to prevent its disorientation. The sleeve should also be capable of stretching to the diameter required for its insertion and withdrawal from the annular space between the core-receiving barrel and the intermediate barrel. Stretching beyond this dimension can be readily avoided by the use of an additional sleeve (eg, a fabric-type sleeve) in conjunction with the elastic sleeve. The additional sleeve has a length coextensive with the elastic sleeve and is arranged to be the outermost sleeve when assembled within the aforementioned annular space. Materials other than fabrics, of course, may be employed in the practice of the invention.

The invention may be more fully understood by reference to the attached drawing in which:

Figure l is a schematic illustration of an apparatus employing the principles of this invention.

Figure 2 illustrates a preferred embodiment of the invention which is contemplated to constitute the best mode of practicing the invention.

Figure 3 is a view taken along the section lines 3-3 of Figure 2.

Figure 4 illustrates one method of loading a core-receiving barrel of the invention with a radially expansible sleeve and an expansion-limiting sleeve.

Referring to Figure l, it will be seen that the apparatus illustrated there includes a bit 10, an outer barrel 11, a non-rotating core-receiving barrel 12, and drill string 13. The upper end of outer barrel 11 terminates in a spline section 14, the upper end of which in turn terminates in a ange 15 provided with a plurality of nozzles 16. Spline section 14 slidably engages a sub 17, which may be considered to be either integral with or a separate member from drill string 13. Sub 17 is attached at its upper end to the main body of the drill string 13; and it is provided with splines 18 at its lower end which engage the splines of the spline section 14.

An interior liange or cross member 19 provided with ports 20 is positioned transversely within sub 17 at a point above flange 15. The ports 20 enable drilling fluid ,to flow from the drill string 13 through the sub section 17. Cross member 19, it will be noted, supports an elongated rod 21. Rod 21 in turn supports plug element 22, and it includes a swivel 23 which enables rotational movement to occur between sub 17 and the plug element. Plug element 22 is of a size to tit within the core-receiving barrel 12 and to move longitudinally Within this barrel.

Flange 15 is provided on its periphery with piston rings or other sealing means 24 so as to maintain a fluid-tight sliding relationship between this ange and the inner wall surface of sub 17. Thus, as drilling mud or other drilling lluid flows into sub 17 and then through the nozzles 16 into the spline drive section 14 of the outer barrel 11, the pressure drop through the nozzles generates a thrust to drive the outer barrel downward relative to sub 17 and drill string 13.

Transverse member 25 provided with uid ports 26 exists within outer barrel 11 at an intermediate point. Supported from this transverse member is an intermediate barrel 27. Since barrel 27 is rigidly attached to cross member 25, and since it rotates and moves longitudinally with outer barrel 11, it may in a sense be considered to be an integral part of the outer barrel. For ease of manufacture and assembly, however, intermediate barrel 27 is preferably a separate entity distinct from the outer barrel. Together with the outer barrel, it defines an annular passageway 28 extending from ports 26 in cross member 2S to flow ports 29 in bit 10. Sealing means in the form of an O-ring or the like is provided between the lower end of intermediate barrel 27 and the bit so as to direct al1 fluid within annular passageway 28 through the ports 29. Bit 10, it will be recognized, may be any conventional type of coring bit; but it is generally preferred that it be a diamond-type bit.

Rod 21 penetrates within intermediate barrel 27 and inner barrel 12 by means of passageway 30. Sealing means 31 positioned Within the passageway effects a uidtight relation between the rod and the passageway but still enables longitudinal movement therebetween.

Core-receiving barrel 12 is supported within and from intermediate barrel 27 by means of swivel 32 which enables rotational movement to occur between these two barrels.

Core-receiving barrel 12 and intermediate barrel 27 define an annular space 34 therebetween. Port 33 in the wall of the core-receiving barrel and near the upper end of this barrel continuously equalizes pressures between space 34 and the interior of the core-receiving barrel.

The lower end of barrel 12 is spaced from bit 10, and it is preferably rounded to permit passage of sleeve 35. Sleeve 35, as explained earlier, is a flexible, radially expansible, and preferably fluid-impermeable member which is used to encase cores cut by the bit 10. Sleeve 35 has a normal, unexpanded diameter slightly less than that of cores formed by the bit. When expanded, sleeve 35 has a diameter potentially greater than that of barrel 12 in order that it may be mounted on the outer surface of the barrel and within annular space 34. In a preferred arrangement, sleeve 35 is arranged within space 34 as shown directly in Figure l. Thus, one end of the sleeve is positioned on the exterior surface of barrel 12 and near the lower end thereof. The sleeve then extends up and around the barrel to a point below port 33, whence it is folded back on itself and brought down and taken around the lower end of the barrel to the plug element 22. The latter end of the sleeve is securely fastened to the plug element so that downward movement of the barrels relative to the plug element causes the sleeve to be gradually withdrawn from space 34.

The rounded lower end of barrel I12 facilitates movement of sleeve 35 from space 34 within barrel 12. This movement is further facilitated by providing a lubricating material between the folds of the sleeve within space 34. This material should be selected so as to be not harmful to the sleeve, and it should be reasonably liuid. It should also be adherent to the sleeve so `as to tend to remain within the folds of the sleeve. Bentonitic-type drilling muds, for example, have been found to be especially effective in keeping the folds from contacting one another and in lubricating them so as to promote a slid- Awalt surface of drive section 14.

ing movement therebetween. Other materials contemplated toV be suitable for use are petroleum jelly, cup grease, automobile greases, synthetic polymeric-type lubricants., and the like. Sleeve 35 may be loaded within the annular space 34 in several diierent Ways. One particularly satisfactory Way will be explained later in this description.

In operation, the apparatus of Figure 1 performs substantially in the following manner.

Following assembly of the coring apparatus, it is at- `tachedv to the lower end of drill string 13 and lowered `Within a borehole 40 to core an underlying formation 41. A -s the apparatus is lowered within the hole, pressures are continuously equalized `between the interior of barrel 12 and annular space 34 by means of port 33. Thus, there is no p-ressure dierential tending to expand or contract the sleeve 35. Furthermore, plug element 22.-.-in this initial condition of the apparatus-is positioned substantially at the entrance to the inner barrel 152-;l and ilange or piston 15 is at the upper end of its stroke within sub 17. At this point, it will be noted that-several techniques may be used for holding piston 15 at an upper position within sub 17 until the over-all apparatus has been lowered to the bottom of a borehole @dit isdesired tol stai-'t a coring operation. As will be -explained` in connection with the apparatus of Figure 2, at J.s1ot. arrangeemnt 4is particularly suitable for this purpose.

Once the apparatus` of Figure 1 is located at the bottom of, a borehole, coring is commenced by circulating drill- `ing luid down through drill string 13 and simultaneously rotating the drill string;

Downward flow of the drilling fluid develops a pres- Lsuie drop across the nozzles 16 which in effect thrusts aidrilling load upon bit 10. Rotation of the bit is effeetedz through the splined section 14 and the splines 18, with. the net result that a core 42 is formed. Core 42 *enters within the core-receiving barrel 12, where it is en- @'asedf by sleeve 35. Since drilling iiuld has little or no -access to the core at any time, it will be recognized that contamination o-f the core is greatly minimized. In addition., bridging, disorientation, and other disturbances of 4the core are avoided by virtue of the fact that sleeve y35j, aids the core to retain its original shape and orienta- Furthermore, since swivel 23 enables rod 21 and ey drill string and barrels to rotate while the plug ele- '-ent remains stationary, it will be recognized that the ore is not subjected to any twisting or turning action.

if When the apparatus of Figure l has cut as much core as can be received within barrel 12, parting and recovery .the corefrom formation 41 may be carried out in ny usual manner. Thus, one suitable procedure conin interrupting the liow of drilling fluid so as to lgifeducc the. load on the bit and thereafter spinning the, drill string 13. Enough vibration inherently occurs in.v the drilling system to cause fracture of the core substantially at the bit, Since this apparatus is designed and yirrtendetzl primarily for use in unconsolidated or uncemented structures, it will be recognized that parting of Dthe cores obtained is not a diiiicult problem. The squeezing action of sleeve, 35 itself upon a core will generally -be sufficient to achieve this object. "ssupports the weight of the core, and the sleeve preserves Rod 2l effectively i-i'tsshaperand orientation.

`Attentionwis next directed to Figure 2 in which, as mentionedl earlier, is illustrated a preferred embodiment l0f;v the invention. Figure 2A shows an upper section .Qfzthe embodiment; and Figures 2B and 2C show intermediate and lower sections, respectively.

Referring to Figures 2A and 3, there are illustrated "dfilll string 13, sub sectionv 17, drive section 14, and splines 1.8i The splines in this instance are in the nature of dogs which are attached to the inner wall surface of sub 17 l`and are adapted to engage .l-shaped slots in the outer Thus, when pistou is in its uppermost position within sub 17, it may be locked in this position by rotating the Sub a portion of a turn relative to section 14 until the dogs 18 align themselves with the short-leg portions of the J-slots. Then, by lifting the drill string and the sub section 17, the dogs are locked within the short-leg portions of the J-slots. To release the dogs, the drill string and sub section 17 are first lowered relative to drive section 14. Then, the drill string and sub section are rotated until the dogs are aligned with the long straight-edge portions of the J-slots; and the apparatus is then in a condition for hydraulic pressure to be applied against piston 15 so as to drive the piston downward within the sub section. Dogs 18, by sliding along the long straight portions of the J-slots, enable the drive section 14 to rotate with the drill string 13 while sliding downward relative thereto.

Restated briefly, the coring apparatus of Figure 2 is lowered within a borehole with the dogs 18 located within the short-leg sections of the J-slots. Then, with the bit 10 resting on the bottom of the hole, the dogs are released and placed within the long portions or legs of the J-slots by simply lowering the drill string relative to the drive section and thereafter turning the string with respect thereto. The bit is then in a condition free to core.

Still referring to Figure 2A, it may be seen that the upper end of rod 21 is held in position by means of one or more set screws or the like -45 which are in turn supported by the drill string 13.

Turning next to Figure 2B, it may be seen that outer barrel 11 is not connected directly to section 14 but rather through an interconnecting member 52. The use of the latter member is not a critical aspect of the invention but rather facilitates the manufacture and assembly of the apparatus of the invention. Ports 53 in member 52 lead from the interior of section 14 to annular passageway 28 between the intermediate and outer barrels. Intermediate barrel 27 is supported from member 52 so that it rotates with outer barrel l1.

Core-receiving barrel 12 is supported indirectly from intermediate barrel 27 through collar-like member 57 provided at its upper end with a spring-loaded detent locking mechanism 58. The detent locking mechanism releasably engages a suitable recess within the inner wall surface of the intermediate barrel 27. A swivel in the lower portion of the collar 57 rotatably supports barrel 12. Ports 33 in the wall of barrel 12 effect a continuous pressure balance between the inside of barrel 12 and the annular space 34.

Sleeve 35 is mounted within space 34 in the same general manner as in the apparatus of Figure 1. One end of the sleeve extends around the lower edge of barrel 12 and is supported from plug element 22. Swivel 23 supports the plug element from the rod member 21. A seal 46 on the lower outer surface of the intermediate barrel 27 etfects a seal between that barrel and the inner periphery of the coring bit lil. Rollers 6i) provided around the lower periphery of the core-receiving barrel 12 facilitate movement of sleeve 35 from space 34 into barrel 12. Plug element 22 is provided with a recess 62 in its lower end to permit this member to be held by a suitable tool during assembly and disassembly. A seal 63 is preferably provided between plug element 22 and swivel 23 to exclude dirt and other materials from the swivel. Plug element 22 for ease of manufacture and assembly preferably includes a nipple element 72 and a locking member 77. The sleeve 35 is then preferably attached to element 72 rather than directly to the main body of the plug element 22.

No detailed discussion of the manner in which the apparatus of Figure 2 operates is felt to be necessary, since it is believed that its operation will be readily apparent from this figure-especially when taken in conjunction with Figures l and 3 and the preceding discussion. Accordingly, attention is next directed to Figure 4, in which is illustrated a preferred manner for loading a corereceiving barrel of the present invention with an elastic sleeve. Different stages of the loading operation are shown in Figures 4A, 4B, and 4C; and the core-receiving barrel in this instance is assumed to be of the readily removable type shown in Figure 2.

The apparatus shown in Figure 4 includes core-receiving barrel 12, nipple element 72, and passageway 61. It also includes plug 71, clamps 73, and pulling ange 76.

In addition to a radially expansible, elastic sleeve 35, the apparatus of Figure 4 also includes an expansionlimiting sleeve '75. As explained earlier, sleeve 75 may consist of a woven fabric material such as canvas or nylon which has a preselected maximum diameter. The maximum diameter is less than the inner diameter of the intermediate barrel shown in either Figure 1 or Figure 2. While it is not absolutely necessary to use such a sleeve, its use is preferred since it simplies the task of loading the elastic sleeve upon the surface of the corereceiving barrel. It also helps to protect the elastic sleeve, as for example by providing resistance to longitudinal stretching.

In describing Figure 4, it may be assumed that corereceiving barrel 12 is of a character to receive a threeinch diameter core; that the limiting diameter of sleeve 75 is about four and one-half inches; and that sleeve 35 has a normal diameter (unstretched) of two inches. A core barrel of the type shown in Figure 2C having these dimensional characteristics has been repeatedly used with outstanding success. The intermediate barrel (see member 27 in Figure 2C) of this same core barrel has an internal diameter of about ve inches.

Referring iirst to Figure 4A, a loading operation is commenced by clamping one end of each

sleeve

35 and 75 to the nipple member 72. Clamps 73 are provided for this purpose, and it will be noted that the elastic sleeve in this instance is clamped over the limiting sleeve 75. The remainder of each sleeve is rolled back over the nipple member; and the opposite ends of the sleeves are nipped or held between the inner wall surface of barrel 12 and plug 71. The maximum diameter of plug 71 is preselected such that this member can be slid or moved through the barrel 12 when the

sleeves

35 and 75 are not interposed between the member and the barrel. With the apparatus in the condition shown in Figure 4A, a quantity of a lubricant is introduced within sleeve 35 through passageway 61. The nature ofthe lubricant has been explained earlier; and the quantity employed should be sulcient to coat the surface of sleeve 35. The quantity should also be preferably suflicient to provide a cushion-like action between the folds of the sleeve 35 after it has been assembled within the annular space between the core-receiving barrel and the intermediate barrel. This cushion or film greatly assists the sleeve or sleeves to move smoothly out of the annular space 34 and into the core-receiving barrel in response to downward movement of the outer and intermediate barrels. Conventional bentonitic water-base drilling muds have been found to be quite satisfactory for this purpose.

Following the injection of the lubricant, the sleeve (or sleeves) are inflated by injecting air, for example, through passageway 51. lnliation causes both sleeves to expand to the maximum diameter possible for sleeve 75. The expanded sleeves are forced into the position shown in Figure 4B by working them toward barrel 12; and the iniiating uid is then bled off. Bands are then temporarily wrapped around the sleeves to hold them against the surface Si) of flange 75; and plug 71 is then pushed out of. engagement with the sleeves. The sleeves are pulled around the end of the barrel 12 into the position shown in Figure 4C, and plug 7l and its attached rod are removed as shown in Figure 4C. The temporary bands around thesleeves are then removed, and ange '76 is pulled free. Following this, the end of barrel 12 which is not shown is plugged or capped; and the sleeves are reinated through passageway 61 and manually rolled on barrel 12 simply by moving nipple 72 toward the barrel and working both sleeves on the barrel. The cap or plug on the non-illustrated end of the barrel is then removed, and the sleeve is ready for installation within the coring apparatus proper. It will be noted that a small body or lm of liquid will now be present in the space between the two folds of the sleeve 3S.

To insert the core-receiving barrel 12 (after it has been loaded with a sleeve) within the core barrel of Figure 2C, bit 10 is first removed. Then, as the barrel 12 is inserted, the spring-loaded detent means 58 engages matching recesses within the intermediate barrel 27; and the barrel 12 is thus locked in operating position. The nipple 72 is fastened to the plug element 22 which secures the sleeve 3S to the rod 21. Bit 10 may then be threaded to the outer barrel 11, and the entire apparatus is in readiness for a coring operation. While the apparatus shown and discussed in this description constitutes a preferred embodiment of the invention, it will be recognized that numerous changes and variations may be made in the apparatus without departing from the spirit or scope of the invention.

T he invention claimed is:

l. In a coring apparatus including an outer barrel supported from the lower end of a drill string in a corotatable and longitudinally movable relation therewith, and a coring bit attached to the lower end of said outer barrel, the improvement which comprises: an intermediate barrel positioned within said outer barrel and deiining an annular passageway therebetween, said intermediate barrel being co-rotatably supported from said outer barrel and sealed around its lower periphery to said bit, said annular passageway at its lower end connecting with drilling-fluid passageways within said bit, a core-receiving barrel supported at its upper end from and within said intermediate barrel, swivel means enabling relative rotation between said intermediate barrel and said core-receiving barrel, said core-receiving barrel deiining an annular space with said intermediate barrel and terminating at its lower end in longitudinally spaced relation with said bit, a plug element within said corereceiving barrel in longitudinally movable relation therewith, a rod element attached at its lower end to said plug element and supported at its upper end from said drill string, said rod element including swivel means enabling rotational movement between the drill string and said plug element, sealing means between the upper end of said intermediate barrel and said rod enabling longitudinal and rotational movement therebetween, a radially stretchable, flexible sleeve supported on the outer surface of said core-receiving barrel within said annular space, one end of said sleeve attached to said plug element and adapted to be withdrawn from said second annular space upon downward movement of said intermediate barrel relative to said plug element, and a passageway in the wall of said core-receiving barrel interconnecting an upper portion of said annular space with the interior of said core-receiving barrel.

2. An improved coring apparatus which comprises an outer barrel assembly supported from the lower end of a rotatable pipe string in a co-rotatable and longitudinally movable relation therewith, the lower end of said assembly adapted to receive a coring bit provided with passageways for the ow of drilling fluid, said outer barrel assembly provided with a passageway for the ow of drilling uid from said pipe string to the passageways of said bit, a core-receiving barrel disposed within and supported from said outer barrel assembly in rotatable relation therewith and defining an annular space therebetween, a flexible, radially and elastically stretchable sleeve supported by the exterior surface of said corereceiving barrel within said annular space, a plug element disposed within said core-receiving barrel in a manner to enable longitudinal movement therebetween,

means to support said plug element from said drill string 1n rotatable relation therewith, said sleeve attached at one end to said plug element and adapted to be withf drawn from said annular space upon downward movement of said outer barrel assembly and said core-receiving barrel relative to said plug element, and means to equalize pressures within said core-receiving ybarrel and said annular space.

3. An improved coring apparatus which comprises an l outer barrel assembly supported from a drill string in a 1 co-rotatable and longitudinally movable relation, said 'outer barrel assembly including an outer barrel and an inner barrel supported from and within said outer barrel L,and defining a laterally conined annular passageway therebetween, said barrel assembly adapted to receive a p curing bit containing drilling-duid at its lower end in fda vmanner to connect said bit passageways with said i said plug element from said drill string in a rotatable relation therewith, said plug element attached to one end of said sleeve and adapted to withdraw said sleeve from said annular space upon downward movement of said core-receiving barrel relative to said plug element, and means to continuously equalize pressures within said annular space and said core-receiving barrel.

4. An improved apparatus for coring unconsolidated earth from within a borehole which comprises an outer barrel member supported at its upper end in a corotatable and longitudinally movable relation from a rotatable string of well pipe, the wall of said outer barrel l provided with a passageway connecting at its upper end w1th the interior of said well pipe and extending the length of said barrel, said barrel adapted to be connected at its lower end to a coring bit in a manner to connect said passageway with drilling-duid courses within the bit, a core-receiving barrel supported from and within said outer barrel to dene an annular space therebetween and in rotatable relation therewith, said core-receiving barrel being open at its lower end and adapted to receive a core cut by said bit, an elongated member including swivel means supported at its upper end from said well pipe and connected at its lower end to said plug element, said elongated member passing through said core-refceiving barrel in a Huid-tight slidable relation, a radially ,contractile lexible sleeve supported by said core-receiving barrel within said annular space, one end of said sleeve extending from said space and attached to said plug element, said sleeve adapted to be withdrawn from said annular space upondownward movement of said core-receiving barrel relative to said plug element, and

means to equalize the pressure continuously between the interior of said core-receiving barrel and said annular space.

5. An apparatus as delned in claim 4 in which the pressure-equalizing means is a port extending through the wall of said core-receiving barrel.

6. An apparatus as dened in claim 4 including a plurality of rollers supported from and spaced around the lower end of said core-receiving barrel, the axes of said rollers being substantially normal to radii of said corereceiving barrel.

7. An improved coring apparatus which comprises in combination an outer barrel attachable at its upper end to the lower end of a rotatable string of drill pipe in a co-rotatable and longitudinally movable relation, a transverse member within and attached to said outer barrel and provided with a plurality of downward-directed jets, an intermediate barrel member supported from and within said outer barrel and defining an aunular passageway therebetween, the lower ends of said intermediate and outer barrels adapted to engage a coring bit in a manner to seal the lower peripheries of the barrels, said annular passageway between said outer and intermediate barrels adapted to convey drilling fluid issuing through said jets from said well pipe to drilling- Huid courses in said bit, a core-receiving barrel closed at its upper end and adapted to receive a core cut by said bit, said core-receiving barrel supported from said intermediate barrel in rotatable relation therewith and dening an annular space therebetween, a plug element disposed within said core-receiving barrel and of a size to enable longitudinal movement of the barrel relative to the plug element, an elongated support member including a swivel supporting said plug element from said drill pipe in a manner to enable said drill pipe to rotate relative to said plug element, said support member passing through said transverse member and the upper end of said core-receiving barrel in a longitudinally slidable Huid-tight relation, a radially constrictive, elastic, flexible, impermeable sleeve supported along the exterior surface of said core-receiving barrel within said annular space, the upper end of said sleeve folded over and extending past the lower end of said sleeve from said annular space and attached to said plug element, said sleeve upon constriction being adapted to possess a smaller diameter than a core cut by said bit, the regions between the folds of said sleeve within said annular space coated with a lubricating material, the upper end of the wall of said core-receiving barrel provided with a port therethrough to equalize pressures between the interior of said corereceiving barrel and said annular space.

Norway Oct. 12. 1953 France Apr. 3, 1955