US2915284A

US2915284A - Reservoir coring

Info

Publication number: US2915284A
Application number: US481837A
Authority: US
Inventors: John E Ortloff
Original assignee: Jersey Production Research Co
Current assignee: Jersey Production Research Co
Priority date: 1955-01-14
Filing date: 1955-01-14
Publication date: 1959-12-01
Anticipated expiration: 1976-12-01

Description

Dec. 1, 1959 J. E. ORTLOFF 2,915,284 RESERVOIR comm;

Filed Jan. 14,1955 a Shee ts-Sheet 1 coRE BARREL 7 CORE l4 SLEEVE POSITION j DURING CORING OPERATION DRILL STEM- j 40 TUBE/ l4 I I 4 SIVEEVE TUBINGGPORT CORE VE BALL, 27 SHARP CHECK A EDGE BALL VALVE e ASSEMBLY 2 SPRING .5 a a F j \IQ alT lo SEALS-30 SEALING AMS 26 FIG. I v v REGIPROCATING 2; AIR MOTOR 3| '3 RECIPROOATING ROD I /I4 l4 SUB l8 2L 4 7 SECTION 3-3 4,] FIG. 3

FIG. 2

John E.Ortloff Inventor By 2 z Afiorney J. E. ORTLOFF RESERVOIR 00am:

Filed Jan. 14, 1955 3 Shgets-Sheet 3 I CORE BARREL CORE TUBING 6. PORT DRILL STEM Av E ,8

O l 7 M4 2 m2 RECIPROCATING AIR MOTOR .RECIPROCATING RAM Inventor John E. Ortloff Attorney United States Patent 2,915,234 RESERVOIR coRusG John -E Ortloif, Tulsa, Okla., assignor, by mesne assign- :ments, .;to Jersey'lroduction Research Company Application January 14, 1955, Serial No. 48,, 1,837

1-3 Claims. (Cl. 25-5-14 It particular-1y relates to a method and apparatus ice ing liquid in a hole still constitutes an undesirablefeature' when sampling a reservoir of the-type described above for the reason that the "hydrostatic pressure and the core sample may be obtained without employing drill- 1 ing mud, the presence of which has been found on occa sion to seriously contaminate such samples. The method and apparatus are further particularly characterized by the fact (1) that the core sample may be continuously maintained under substantially ambient formation conditions, and (2) that it may be sealed off to prevent the loss of any fluids therefrom.

A serious and important problem that confronts the petroleum producing industry at the present time is one of obtaining reliable samples of petroliferous formations that lie beneath the surface of the earth. The problem has become one of particular importance in view of the ever increasing use of secondary recovery methods for obtaining additional oil from subterranean oil reservoirs that have ceased primary production. It is essential, before initiating a secondary recovery procedure in any such reservoir,'to have as much information as possible about the structure, the fluid content, the pore volume, the permeability, etc. of the formation. Such information is extremely valuable in determining whether the formation is susceptible to successful exploitation using secondary recovery techniques and just which techniques should preferentially be utilized.

In line with the growing emphasis on secondary recovery programs, many petroleum producers are conducting extensive analyses of old reservoirs and fields that have in years past lost their reservoir pressure and been abandoned. In an effort to evaluate these old reservoirs and fields and in order to determine whether a secondary recovery procedure can be successfully applied to them, the producers are conducting extensive sampling prog rams. One'sampling technique has been to drill and sample the bottoms or side walls of old wells that were originally producing wells associated with a reservoir or field. It has been determined, however, that the samples derived by this technique are quite inaccurate and not representative of the field or reservoir as a whole. Accordingly, it has become more and more the established practice to drill entirely new holes from the earths surface down to a petroliferous formation and to obtain samples of the formation directly from these new holes. Conventional drilling and coring methods such as rotary and cable tool have been employed for this purpose. In

all of these types of drilling, however, it is necessary to use at least a small amount of drilling mud, water or other drilling fluid in the bottom of the hole in order to properly lubricate the bit and to dispose of the cuttings; and it is therefore conventional to have at least about to 50 feet of water or other drilling fluid within a hole.

The presence of the rilling mud, water or other drillwetting eflects of even this small amount of liquidare considered .to seriously interfere with the reliability of the samples that areobtained. Itis accordingly an obi: ject of the present invention to provide an apparatus and method for obtaining reservoir core campleswherein the samplesneed not be subjected to a drilling liquid of any kind. It is a further object .oftheinvention to provide means for coring aformat'ion in suoha manner that the core sample suffers a very limited exposure to any material that could conceivably be a source of contamina tion. It is a particular object of the invention tov pro ide means for isolating a core sample within thecoring apparatus so that connate liquids are retained with;the

sample. it is further a particular object of the invention to provide a coring method and, apparatus'wherein the These objectives are realized in accordance with the invention by utilizing ,a coring apparatus and procedure which employ a conventional type of coring bit. 1 As the bit penetrates the formation, the resulting core sample is forced interiorly of the coring apparatus and into a posi= tion within a core barrel. When the desired amount of core sample has been forced within the barrel, the apparatus is raised and the core sample is parted at a point vertically within the coring apparatus and above the coring bit as will be explained in greater detail later in this description.- At this point the entrance to the core barrel is closed so as to entrap the sample and its connate fluids within the barrel, and preferablyso as to maintain the sample and fluids under ambient formation conditions;

At this point the apparatus and its encased samplernay be withdrawn to the surface of the earthandexamined or analyzed as desired, The apparatus and procedure of the present invention may be employed along with conventional drilling means; but in a preferred embodiment of. the invention, the:ap+ paratus and procedure are utilized inconjunction with air or any other suitable gasiform materialas thedrilling fluid. Further, the invention may make use of rotary-"or percussion-type drilling apparatus, although the lattertype of apparatus is employed in' a preferred embodiment of the invention. Thus, in a particularly preferred embodiment of the invention, a pneumatically powered, percusslon-typepower source is employed to drive a coring bit; and-airjs utilized as. a drilling fluid to cool the bit and to remove cuttings from the vicinity of the bit. This embodiment of the invention as well as the broad concept of the invention is best understood 'by reference to the attached figures where: p

Fig. .1 is a view in vertical cross-section'of a portion of one embodiment of the inventiom;

F g. 2 is a view in vertical cross-section of another portion ofthe embodiment of' Fig. 1 which is a continuat on of the portion in Fig. .1 and which is ordinarily positioned vertically above'the portion illustratedin Fig. 1. Fig. 31s a view taken along the lines 33"of Fig. 1-. Fig. 4 is a view in vertical or ss section of another embodiment of the invention. i

- Fig. 5 is a vview in vertical cross section of a portion of v one embodiment of the invention illustrating theposition sealed within the barrel.

Turning to the figures, it will be observed that the apparatus therein includes a drill stem 4, an air motor 5, a sub 6, a core barrel 7, a core catcher 9, a coring bit 10, and a reciprocating rod 11 connecting the subto the motor 5. The figures further illustrate a sleeve valve assembly 12, a pair of sealing rams 13, conduits 14, check valve assemblies 15 and a core sample 16.

In examining the apparatus of Figs. 1-3 and Figs. 57, it will be assumed that this apparatus is employed at the bottom of a bore hole with the drill bit directly above and contacting the bottom of the hole. It will further be assumed that the widest portion of the apparatus, normally the bit itself, is sized so as to move freely and centrally within the bore hole. Thus, there exists an annular space that lies between the outer surface of the overall apparatus above the bit and the inner wall surface of the bore hole and which extends substantially the entire length of the bore hole.

It will further be assumed that the apparatus, as illustrated in Figs. 1, 2 and 3, is depicted in that phase of a coring operation wherein a sample has been drilled, forced within the core barrel, parted from the formation, and

During the actual coring procedure, the ball 17 is absent from the apparatus and the sleeve valve assembly 12 is in a raised vertical position (indicated by the dotted lines) so as to seal off the upper entrances or ports to the conduits 14. The positions of the various components of the device during drilling operations are illustrated in Figs. 5, 6 and 7.

Having briefly identified the major components that are illustrated in the figures, attention is now directed to a more detailed consideration and description of each one of these components. Taking first the bit member 10, it will be noted that this member may be any conventional type of percussionor rotary-style coring bit. Both types are well known in the art, and a detailed discussion of them therefore is not considered to be necessary in the present description.

The coring bit 10 is mounted and secured to the lower end of the sub member 6 which extends vertically from the bit to the lower end of the reciprocating rod 11. As illustrated, sub member 6 has an annular type configuration and houses the core barrel 7, the core catcher 9, the ball check assemblies 15 and the sealing rams 13. With particular reference to the core barrel 7, it is necessary that the sub member 6 and the core barrel be free to move relative to one another. Thus, in a reciprocatingor percussion-type drilling apparatus such as is illustrated in the figures, it is necessary that the core barrel 7 be free to move vertically up and down within the sub member. Likewise, when the coring apparatus is of the rotary-type, it is necessary that the core barrel 7 be free to move rotationally With respect to the submember 6. Thus, during a coring operation, the core barrel 7 remains substantially stationary during movements of the sub member 6 and its bit 10.

Since the apparatus in the figure is of the percussionor reciprocating-type, it will further be observed that the relative lengths of the core barrel 7 and the core barrel zone 18 within sub member 6 must be of such dimensions that the core barrel remains stationary within the zone 18 entirely unimpaired by the sub member during either stroke of the sub member. By observing this design construction, the core sample within the core barrel 7 is not subjected to shocks or shearing forces that are occasioned by the movement of the sub member and the impacts of theibit 10.

In a lower portion of sub member 6vertically intermediate the bit 10 and the lower end of the core barrel zone 18are provided recessed zones or ram chambers 19 which are adapted to house the closure rams 13. In the figures it will be seen that these zones are adapted to completelyreceive the ram members when the apparatus is actually engaged in a coring operation. During such time,each .ram is entirely contained within its respective ram chamber; and a free and continuous central passageway 20 is provided within the overall apparatus to enable the core sample to move up within the apparatus and thence within the core barrel 7 as particularly illustrated in Figs. 5, 6 and 7. On the other hand, when the coring operation has been completed and a core sample trapped within the core barrel 7, the rams are forced outward from within their respective ram chambers; and the core barrel is sealed when the two rams come together, asparticularly illustrated in both Figure 1 and Figure 3,. The actual step involved in driving the rams against one another is considered at greater length later in this. description.

Each sealing ram member 13 is preferably provided with a rubber or other elastic and compressible surface 31, particularly where they engage one another in order to provide as good a sealing arrangement as possible. While rubber is a particularly preferred material for this purpose, other conventional gasket or sealing materials may be utilized at this point in the apparatus. Whatever material is employed, it may be bonded in any conventional, suitable manner to each one of the rams.

Still referring to the closure rams 13, it is necessary that they be of a size such that they may be housed completely within the ram chambers 19 during a, coring operation and also such that they may completely seal off the passageway 29 when they are driven against one another. In the latter position, it is further necessary that each ram extend sufficiently within its respective ram chamber 19 so as to be amply supported in the sealing position. Along this same line, it is particularly desired that sealing means 30 be provided entirely around the inner periphery of each ram chamber at a point near the entrance to its respective chamber. Suitable sealing means, for example, may be rubber O-rings or other packing materials that are used in situations similar to the one illustrated in the figures. These seals 30 tend to prevent cuttings and other materials from entering the ram chambers during a coring operation and also to prevent fluids or other materials from entering or leaving the core barrel 7 and passageway 20. In other words, the seals 30 assist the rams in their function of completely isolating a core sample 16 within the core barrel 7. The overall dimensions and configuration of the core barrel have been discussed in earlier paragraphs in this description. It may be added here that the core barrel must be provided with a core catcher 9 and a core fracturing section 21 which is adapted to separate the core sample from the formation and to perform the separation at a point vertically above the sealing rams 13. In this connection, a number of conventional core catchers and core fracturing devices may be employed. It is particularly contemplated that a sharp edge such as is illustrated in Fig. l is the best type of core fracturing device to employ. In this type of device, the core catcher 9 loosely grips cores 16 and tends to ride upwardly within recess 40 during a coring operation. However, when coring is completed and the coring apparatus is lifted within the borehole, the core catcher 9 tends to remain stationary relative to the remaining apparatus. The sharp-edged shoulder 21 causes the lower end of the core catcher 9 to be thrust inwardly against the core and to break the core at that point. A typical core catcher of this type is shown in the Composite Catalog of Oil Field Equipment; 20th Edition, 19544955, page 1380. Drilling and Service, Inc., Dallas, Texas, is described as the manufacturer of the device. Page 1379 of the catalog shows the core catcher in an assembled condition within a coring tool.

Pneumatic motor 5 may be any conventional form of reciprocating-type pneumatic motor which is of a size and power adapted to conduct a coring operation. Such motors are well known in the art, and a detailed discussion of them is not considered to be necessary in this description. There exists, for example, a large number of air-hammer type motors which are contemplated to be particularly well suited for the purposes ofthis invention.

Still referring to motor 5, it will be noted thatthe motor, as illustrated, is arranged to impart a vertical reciprocating motion to rod II which in turn imparts a similar motion to sub 6 and bit 10. Thus, the motor supplies the energy necessary to enable the bit to cut through any given formation.

The effective stroke and frequency of the" motor 5 may vary over a rather broad range consistent with known devices and conventional drilling techniques; It is contemplated, however, that" s'trokes'of from 1 to 4 inches and frequencies of from 60 to 300 per minute are the best to employ.

Air or other suitable gasiform fluid may be supplied to motor 5 through a suitable conduit system, preferably drill stem 4'. Drill stem 4 extends from the air motor 5 to the top of the borehole where it may be connected to a source of compressed air or other suitable gasiform fluid. The exhaust from the air motor may be directed into the annular space between the drill stem and the bore hole and vented directly up the bore hole to the surface of the earth.

At the lower portion of the drill stem and immediately above the air motor 5 is positioned a sleeve valve assembly 12 which has been briefly referred to earlier in this description. As pointed out there, the sleeve valve portion 22 of this assembly is capable of taking one of two positions depending upon the phase of the overall operation in which the apparatus is engaged. When the apparatus is actually in the process of drilling a core sample in a formation, sleeve valve 22 is vertically above its illustrated position of Fig. 2 and is in the position shown in Fig. 6 so as to seal the upper entrances to the conduit 14 and thereby prevent air or other fluids from flowing into these conduits from the drill stem 4. With the valve in this upper position, air then flows directly down the drill stem 4 through the central passageway 23 in the sleeve valve portion 22 and thence through the inner open portion of the spring member 24 into the motor 5. Spring member 24 is of a size and strength suflicient to maintain the sleeve valve portion 22 in the'position where it seals off the conduit 14.

Sleeve valve portion 22 is provided with two valve seating surfaces-cne being its outer lateral surface which moves in a close fitting relationship with the inner surface of the drill stem and the other being a conical, seat 25 provided interiorly and near the bottom thereof. The latter valve seat-i.e., 25-i's closed by dropping a ball or other suitable plug down through the drill stem 4. The ball enters the central portion 23 of the valve assembly 12 and then comes to rest on the valve seat 25, where it prevents air from entering the air motor 5; Air pressure within drill stem 4 then overcomes the strength of the spring member 24 and forces the sleeve valve member 22 vertically downward, thereby exposing the entrance connections or ports to the conduits 14'. These conduits extend from the drill stern exteriorly of the coring apparatus to the interior portions" of the ram chambers 19. Thus, air entering the conduits 1'4 flows downwardly through the conduits and through the ball check valve assemblies 15 to the ram chambers 19 where it forces the rams outward from the chambers and against one another. It is apparent that the pressure employed to close the sealing rams.13 may be entirely independent of the formation pressure and is isolated from and has no influence on the pressure within the core barrel 7. Thus, the amount of air pressure required or desired to close the entrance to the core barrel is only indirectly governed or affected by the pressure within the barrel. Furthermore, the pressure exerted on the sealing rams 13 is continuously maintained by virtue of the check valves within the check valve assemblies as well as the seals surrounding the rams within the ram chambers.

It will be noted that the conduits 14 are provided with flexible sections 26 to allow for the reciprocating motion ofthe overall apparatus: These flexible portions may be of a telescoping variety, but it is contemplated that flexible hose elements constitute the best form of apparatus to employ for this purpose.

Having described the structural features of the apparatus in Figs. 1-'3 and Figs. 5-7, attention is now directed toward abriefexplanation of the manner in which the apparatus is operated. Figs. 5, 6 and 7 illustrate the position of the various components of the apparatus dur' ing-a coring operation. At the outset of this description, it will be assumed that the apparatus has been positioned Within a bore holeand thatbit 10 rests substantially at the bottom of the hole. It is further assumed that the apparatusis intended to obtain a core sample of the formation' l-yingimmediately below the bottom of the bore hole.

With these assumptions in mind, it will be observed that sleeve valve 22-is in its upper vertical position, thereby sealing off the entrances to the conduits 14. At this point, compressed air is supplied from the earths surface through the drill stem 4 and thence through the passageway 23 to the air motor 5. The influx of the compressed air causes the motor 5 to impart a vertical reciprocating motion to rod 11 which in turn imparts a similar motion to Sub 6 and bit 10. Bit 10 thereby is repeatedly driven against the bottom of the bore hole to pulverize a portion of the underlying formation and to cause a core sample of the formation to enter the space or passageway 20. The sealing rams 13, of course, are entirely enclosed with in the ram chambers 19, thereby permitting the core sample to enter freely within the interior of the coring apparatus.

At this point it is necessary to indicate that it is preferred to direct a stream of the air or other fluid from within the drill stem 4 (or from the earths surface) to a point near the bottom of the bore hole and in the vicinity of the drill bit 10. This jetted stream of air serves to cool the bit and to carry any cuttings upwardly in the bore hole between the wall of the borehole and the coring apparatus. Air velocities in this annular space of about 3 to 10 ft. per second may be employed for this purpose.-

As the coring operation progresses, the core sample within the passageway 20' progresses upwardly until it eventually enters the core catcher 9 and the core barrel '7; and when a sufficient sample has been enclosed within the core barrel, the entire apparatus is lifted from the bottom of the bore hole. As the apparatus is lifted, it is apparent that the lower edge of the core barrel 7 eventually comes to rest on the shoulders 27 of the sub member 6'. As the apparatus is lifted beyond this point,

the sharp-edged portion 21 causes the lower endof core catcher 9 to be deflected inwardly against the core sample 16. Further lifting of the apparatus therefore causes the core sample to break at this point.

At this point the apparatus is lifted until it is clear of obstructions within the bore hole, and a ball 17 is then dropped Within the drill stem 4 until it comes to rest on the valve seat 25. With the ball in this-position, additional air is forced down the drill stem 4 with the result that the spring 24 is compressed and the sleeve valve 22 moved in a downward manner to expose the entrances to the conduits 14. Air then flows directly through these conduits and into the ram chambers 19 where it forces the sealing rams 13 from their chambers and into the passageway 20. The air pressure in the ram chambers, furthermore, seats the two rams against one another; and the core sample 16 is thereby completely sealed within the core barrel 7. It is important, of course, that the entire apparatus be lifted a sufficient distance after the core sample has been fractured so that the closure rams 13 are free to enter the passageway 20 and not be obstructed in their movement by any remaining portion of the core sample.

Having isolated the core barrel 7 by closure of the sealing rams 13, the entire apparatus may now be withdrawn from the bore hole with the core sample intact within the core barrel 7. After rams 13 are closed the parts of the device are then in positions illustrated in Figs. 1, 2 and 3. The air pressure within the drill stem 4 may be reduced as desired without fear of breaking the seal on the core barrel in View of the fact that the presure on the sealing rarns 13 is retained by the check valve assembly 15.

At this point it will be appreciated that the apparatus and procedure that have been described in connection with Figs. 1-3 and Figs. 5-7 represent merely one specific embodiment of the present invention. Actually, a number of modifications and variations may be resorted to without departing from the spirit or the scope of the invention. Thus, it will be noted that the coring bit and assorted apparatus may be of a type that is actuated by rotary motion in place of a reciprocatingor percussiontype motion. In this instance the rotary motion may be supplied by a turbine-type air motor in place of the reciprocating motor 5, or it may be supplied at the earth's surface by means of a conventional rotary table or other suitable device. It is well known in the art to employ rotary forms of coring apparatus, and only very minor changes would have to be made in the apparatus of Figs. 1-3 in order to utilize a rotary power source. Thus, the core barrel 7 would have to be provided with a conventional type of swivel connection to permit it to remain stationary with respect to the sub 6. Such a feature is a well known one in rotary forms of coring apparatus, and details of this type have not accordingly been illustrated in any separate figures in this description.

It will also be recognized that the sealing ram members 13 may be varied considerably in their configuration and design without departing from the scope of the invention. For example, it may be desirable on occasion to employ a single such ram member which is designed to be housed within one side of the sub member 6 and to be driven across the passageway 20 to the opposite side of the sub member thereby closing off the core barrel in substantially the same manner as described earlier. Alternatively, it may be desirable to employ more than two such ram members.

It will further be appreciated that the sealing ram members 13 may be closed by employing means other than the compressed air apparatus illustrated in the figures. For example, it may be desirable to close the rams by means of compressed springs or solenoids which are triggered by suitable mechanical or electrical means from the earths surface. It is contemplated, however, that the apparatus which is illustrated in the Figures 1-3 constitutes the best mode of carrying out the invention.

Figure 4 illustrates an apparatus embodiment of the invention which includes a number of the alternative features just described. The apparatus in this figure includes a sub 6 and a core barrel 7, but in this instance the sub and the core barrel are adapted for use with a rotary drillin system. Core barrel 7 is mounted within the sub 6 by means of a suitable swivel 33; and the sub is threaded or otherwise adapted at its upper end to be connected to a string of drill pipe, a suitable driving memher, or the like. Thus, inner barrel 7 is of a character to remain stationary with respect to the outer barrel or sub 6 during a coring operation.

The apparatus in Figure 4 further differs from the apparatus of Figures 1-3 in that it is provided with a single ram 13 which is normally retained within chamber 19 during a corin, operation. Wound around recess 19 is a solenoid coil 35 which upon energization is adapted to thrust ram 13 outwardly from its chamber 19 and across passageway 20 into chamber 36. Electrical leads to the solenoid 35 are contained within conduit 34 which extends upwardly through the wall of sub 6. The ram member is preferably provided with a soft resilient material 31 as shown in order to effect a fluid-tight seal upon closure. Seals '31 are also preferably provided to aid in this respect. q

A channel 32 is also provided in the wall of sub 6 to conduct drilling fluid from a drill string or other member or assembly above sub 6 to the bit 10. Thus, drilling fluid such as air may be passed down through channel 32 to the bit in order to remove drill cuttings as they are formed by the bit.

It will also be recognized that drilling fluids other than air may be used as desired. For example, conventional drilling liquids and drilling muds may be employed, particularly where these fluids do not interfere seriously with the sampling operation. In this instance, the drilling fiuid system that is illustrated in the figures may be readily modified to accommodate these drilling liquids. Suitable gasiforrn fluids include the chemically inert gases and other gases which are non-re active with the core sample or its connate fluids and which do not interfere with analyses, etc. performed on the core.

What is claimed is:

1. An apparatus for obtaining a core sample from a formation underlying the bottom of a bore hole which comprises a coring bit, a sub connected to and vertically intermediate said coring bit and a drill stem, means for driving said bit against the bottom of the bore hole whereby a core sample is cut from the formation, a core barrel disposed within said sub member and of a character to receive said core sample, means supporting said core barrel within said sub with free movement therein, r-am closure members recessed within said sub member, means to force said members against one another so as to seal off the entrance to said core barrel, and fracturing means within said sub member positioned vertically above said ram closure members for fracturing and separating the core sample from the formation.

2. Apparatus for obtaining a core sample from a subterranean formation underlying the bottom of a bore hole which comprises a coring bit, a core barrel above said coring bit, means for holding said core barrel above said bit with said core barrel having free vertical movement with respect to said bit, a passageway leading from said coring bit to said core barrel arranged to provide movement of the core sample from the formation into the core barrel, means for driving the coring bit through the formation and for forcing the core sample up within the core barrel, means for fracturing the core sample at a point vertically intermediate the upper end of the core barrel and the bit, at least one retractable closure member disposed adjacent said passageway vertically intermediate the bit and said fracturing means, each said closure member being in the retracted position during a coring operation, and means for forcing each said retractable closure member from its retracted position following a coring operation to close said passageway and to seal the fractured sample within the core barrel under ambient formation conditions.

3. An apparatus for obtaining a core sample from a formation underlying the bottom of a bore hole which comprises in combination a drill stern, a coring bit mounted at the lower end of said drill stern, a core barrel positioned intermediate the drill stem and the drill bit and adapted to receive a core sample cut by the drill bit, means for supporting said core barrel above said bit with said core barrel having free vertical motion with respect to said bit, means for driving said bit through said formation whereby a core sample is forced within said core barrel, core catcher means for holding the core sample within the core barrel, fracturing means for separating the core sample from the underlying formation at a point within the coring apparatus, means for lifting the coring apparatus vertically above the unsevered portion of the formation, retractable'closure members disposed within said coring apparatus and vertically below the fracturing means, said retractable closure members being in the retracted position during a coring operation whereby the core sample freely enters the core barrel, and means for driving the closure members from their retracted position after the coring apparatus has been lifted free of the unsevered portion of the formation whereby the core sample is sealed under substantially ambient formation conditions.

4. An apparatus for obtaining a core sample from a formation underlying the bottom of a bore hole which comprises an annular type coring bit, a sub connected to and positioned vertically above said coring bit, said sub having internal shoulders at its lower end thereof and with the top of said sub enclosed, a drill string connected to and positioned vertically above said sub member, a core barrel within said hub member communicating with the central passageway in the coring bit, said core barrel being of a greater diameter than 'the internal diameter of said shoulder members, means for transmitting power via said drill string to said coring bit whereby a core sample is cut from the formation and is driven upward and within the core barrel, fracturing means for parting the core sample from the formation at a point vertically above and spaced from the coring bit, retractable closure members vertically intermediate said bit and said fracture means arranged to seal the passageway leading to the core barrel when the coring operation has been terminated and when the apparatus has been lifted vertically above the remaining portion of the formation, and means for forcing said closure members from their retracted position.

5. An apparatus as defined in claim 4 in which the retractable closure members are rams adapted to be forced against one another.

6. In an apparatus for obtaining a core sample from the formation underlying the bottom of a bore hole including a string of drill pipe and a core barrel and a coring bit secured to the lower end of the drill string, the improvement which comprises means for supporting said core barrel above said bit with said core barrel having free movement with respect to said bit, fracturing means arranged to sever a core sample within said core barrel from the underlying formation, said fracturing means being positioned vertically above and spaced from the coring bit, retractable closure means positioned vertically intermediate said bit and the lower end of said severed core sample, means for lifting the entire apparatus vertically above the unsevered portion of the formation, and means for driving the retractable closure means from the retracted position and thereby sealing the core sample within the core barrel.

7. An apparatus for obtaining a core sample from a formation underlying the bottom of a bore hole which comprises an annular type coring bit, a sub connected to and vertically above said core bit, said sub being enclosed at its upper end and having internal shoulders at its lower end, a hollow drill stem connected to and vertically above said sub member, means for driving said coring bit against the bottom of the bore hole and for forcing the resulting core sample upward within said sub member, a core barrel within said sub member adapted to receive said core sample through a passageway interconnecting the core barrel with the opening in the coring bit, said core barrel having a larger external diameter than the diameter of said shoulder and having a smaller longitudinal dimension than the longitudinal dimension between said shoulder and said enclosure, core catcher means adapted to retain the core sample within the core barrel, fracturing means within said sub member arranged to separate the sample from the underlying formation at a point vertically above and spaced from the coring bit, retractable ram members disposed within recessed chambers within said sub member, means for driving said ram members at least partially from said recessed chambers and thereby sealing the entrance to the core barrel.

8. An apparatus as defined in claim 7 in which the coring bit is of the rotary type and swivel means are provided to support the core barrel from the sub member.

9. An apparatus as defined in claim 7 in which the coring bit is of the percussion-type and the core barrel is slidably mounted within the sub member.

10. in a coring apparatus including a sub, a coring bit attached to one end of the sub, drive means attached to the opposite end of the sub, and a non-rotating corereceiving barrel mounted within the sub, the improvement which comprises at least one retractable ram member mounted within said sub between said bit and said core barrel and adapted to seal a core within said apparatus, swivel means rotatably supporting said barrel from said sub, means to actuate each said ram from its retracted position, and core-severing means adapted to sever a core within said core barrel.

11. in an apparatus for coring a subterranean formation including a sub attachable at one end to a coring bit and at its opposite end to suitable bit-driving means, the improvement which comprises a core-receiving barrel longitudinally slidably mounted within said hub and adapted to receive a core cut by said bit, ram closure means mounted within said sub and adapted to seal the core opening through said bit, means to actuate said ram closure means, means limiting the longitudinal movement of said core barrel within said sub, and core-severing means adapted to sever a core within said core barrel.

12. In a coring apparatus including a coring bit and a barrel-like sub interposed between and connected at each end to said bit and a bit driving means, the improvement which comprises a core barrel mounted within said sub in a manner to enable relative movement between said sub and said barrel, said barrel being adapted to receive a core cut by said bit, core severing means mounted adjacent the entrance to said core receiving barrel, means limiting the longitudinal movement of said core barrel within said sub, ram closure means retractably mounted within said sub between said bit and said core severing means, means to actuate said ram closure means and said closure means being operable to seal the core entryway into the apparatus.

13. In a rotary coring apparatus including a rotatable sub with a coring bit attached at one end thereof and a core-receiving barrel mounted within said sub, the improvement which comprises retractable ram means mounted within said sub adjacent said bit and operable to seal the core entryway within the sub, swivel means supporting said core receiving barrel from said sub, means to actuate said ram means, and core severing means adjacent the entryway into the core barrel.

References Cited in the file of this patent v UNITED STATES PATENTS 1,1 12,49 8