US2848194A - Sidewall sampler - Google Patents

Description

Aug. 19, 1958 F. v. PORTER SIDEWALL SAMPLER FiledJune 28, 1954 2 Sheets-Sheet 1 roeeesr l4 oem-g INVENTOR. v

19, 1958 F. v. PORTER 2,848,194

SIDEWALL SAMPLER Fil'ed June 28, 1954 2 Sheets-Sheet 2 SIDEWALL SAMPLER Forrest V. Porter, Monterey Park, Califi, assignor, by mesne assignments, to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Application June 28, 1954, Serial No. 439,629

15 Claims, (Cl. 255-14) This invention relates to the drilling of earth boreholes such as gas and oil wells, and more especially to a means of obtaining samples of the earth formations forming the sidewalls of such previously drilled, uncased earth boreholes.

This application is a continuation-in-part of copending application Serial No. 333,424 filed January 27, 1953, now abandoned. That application discloses a sidewall sampling device having an elongated body adapted to be lowered into a well borehole and formed with a plurality of transverse bores extending substantially completely therethrough forming shooting bores for a plurality of tubular open end core sampling projectiles,the bores and projectiles having annular shoulder formations which cooperate to form annular powder chambers external to the projectiles. Retrieving means for the sampling projectiles comprise wires or cables which are disposed in folded arrangement within the projectile barrels, each cable having one end secured to the rear end of the projectile and the other end secured to the body of the tool at the sides of the shooting bores of the elongated body.

In the shooting of such formation sampling projectiles the satisfactory attachment of the projectile retrieving cables to the gun body and to the projectile has presented a difiicult problem inasmuch as, for example, due to the high acceleration of the projectiles and the inertia of the cables attached thereto, the cables are frequently sheared at the bend points thereof which are necessarily present in portions thereof, particularly those adjacent the point of attachment to the gun body and to the projectiles. Another feature in the design of sidewall formation sampling instrumentalities is the desirability of changing or varying the velocity of the core sampling projectiles to suit varying borehole conditions and different characteristics of the strata surrounding the boreholes to be penetrated. These and other problems which have presented themselves in formation samplers of the prior art are overcome in the development of the present invention.

It is, therefore, an object of the invention to provide an explosively actuated formation sampling tool of improved construction and operating characteristics having important advantages over those heretofore employed.

Another object of the invention is to provide a novel formation sampling tool operable in a manner resulting in increased sample recovery.

A further object of the invention is to provide a novel explosively actuated sampling tool having a plurality of explosively propelled sample-taking projectiles, the operation of which results in increased recovery of the sampling projectiles.

An additional object of the invention is to provide a novel sampling tool wherein the size of the powder charge chamber for the propellent powder charge may be readily altered or adjusted to vary the propellent force whereby the acceleration and velocity of the projectile 7 2,848,194 Patented Aug. 19, 1958 may be correspondingly varied without changes in the structure of the tool itself.

Another object of this invention is to provide an improved and more durable and reliable means of attachment of the core sampling projectiles to the gun body thereby increasing the reliability of recovery of the core sampling projectiles after firing.

The foregoing and other objects, advantages and features of novelty will appear and be brought out more fully in the following specification, reference being had to the accompanying drawings wherein:

Figure 1 is a view in elevation of the general assembly of a sidewall sampling tool embodying the invention;

Figure 2 is an enlarged longitudinal sectional view of a portion of the tool shown in Figure 1;

Figure 3 is a partial elevational view further enlarged of a portion of thje tool shown in Figure 2;

Figure 4 is an enlarged transverse section taken along the line 44 of Figure 2;

Figure 5 is a fragmentary sectionalview taken along the line 5-5 of Figure 4; and

Figure 6 is a transverse sectional view similar to Figure 4 showing a modified form of the invention.

Referring first primarily to Figures 1-5, inclusive, of the drawing, the numeral 10 designates an elongated gun body having an upper end portion 11 making threaded connection to the lower portion 12 of a control head 13, the upper end of which is suitably secured as by a threaded connection, not shown, to a cable head 14 to which is secured a suspension conductor cable 15. The upper portion of body It has a plurality of longitudinally spaced-apart, laterally directed gun bores 18 which extend completely therethrough from a flat exterior face 19 on one side of the body. The lower portion of body 10 is formed with an elongated, laterally-facing side recess or cavity 28 to receive the suspended formationsarnpling projectiles after they have been fired into and retrieved from the borehole wall formations, as more fully described hereinafter.

Each gun bore 18 has a forward bore portion 20, an intermediate bore portion 21 of less diameter than portion 20, and a rear bore portion 22 which is internally threaded and of larger diameter than portion 21. Intermediate the forward bore portion 20 and the intermediate bore portion 21 is an undercut portion 20a of slightly increased inside diameter as compared to portion 20, and forming at the juncture thereof with the beforementioned intermediate bore portion 21 a forwardly facing, annular shoulder 23. The rear end of bore 18 is provided with a closure member or breech plug 24 which has external threads engaging the internally threaded portion of the bore 22. Breech plug 24 is formed with an annular concentric groove or recess 25 which forms a central, forwardly extending boss 26 which in turn has an internally threaded bore 27 into which is threaded a hollow nut 69 to be described more fully hereinafter.

A forwardly facing annular shoulder is formed on the inner surface of the annular recess 25 of the breech plug 24, which serves as a seat, adjustable in longitudinal position, for the inwardly extending rear end of the core sampling projectile 31.

The lower end of body 10 is formed with a threaded pin connection 29 onto which may be threaded the box connection of another sampling tool body of a construction which may be the same or similar to that herein described and shown at 10. Normally, in the absence of another sampling tool body being connected thereto the pin 29 makes threaded connection with an end bull .plug as shown at 30. O-ring grooves and seals 17 are provided on the upper end portion 11 and lower pin connection 29 of body 10 to exclude borehole fluid from the ignition passage in the body.

Disposed within each gun bore 18 is a hollow or generally tubula'rsh'aped sample-taking projectile 31, each projectile being formed with an axial bore or passage 36 extending therethrough and with a rearwardly extending tubul'a'r portion having a cylindrical outer surface 32 making a sliding fit within the intermediate bore portion '21, and a forward externally enlarged .end portion 33 having a cylindrical outer surface portion 33a making a slida'ble fit Within the forward bore portion 20 of the before-mentioned gun bore -'18. The forward end portion of the rearward cylindrical surface 32 of the projectile 31 is curved outwardly to meet the forward cylindrical surface 33a thereof, thereby forming at the juncture of said surfaces a rearwardly facing annular shoulder 34. The before-mentioned'annular shoulders 23 and 34, the interior-surface of the undercut recess 211a and the forward portion of the exterior surface of the cylindrical surface 32 form boundaries of an annular chamber or cavity for containing a combustible or explosive charge 16 for propelling the core sampling projectile laterally from the bore 18 into an adjacent earth formation.

Charge 16 which may comprise arsuitable propellent material such as gun powder, may be contained within a suitable envelope 16a of paper, fabric, plastic or the equivalent material, or it may be pelletized or otherwise suitably consolidated, whereby the charge may be conveniently handled in the form of a relatively solid ring or annular shaped body when loading the gun. The forward, externally enlarged end portion 33 of the core sampling projectile member 31 is tapered or beveled as shown at 35 to meet the cylindrical inner wall portion of the bore 36 to form a sharp forward cutting edge 37.

An annular groove '38 is formed vin the forward end portion 33 of the bore barrel projectile 31 for containing anCO-ring seal 39 and the intermediate bore portion 21 of the gun bore 18 is similarly grooved, forming an annular groove 40 in which is retained an O-ring seal 41. Seals 39 and 41 serve primarily to protect the propellent charge 16 in the aforementioned annular chamber surrounding the projectile from the entrance of borehole fluid. Body 10 is formed with a pair of coaxially aligned, threaded drill holes 42 which extend radially with respect to the longitudinal axis of the gun bore 18 into the forward portion 20 of thegun bore 18 and in each of these holes is a threaded shear set screw 43, the inner end of which engages the tapered forward end portion 35 of the projectile 31 for initially retaining the core sampling projectile in seated position in its bore 18. Set screws 43 may be of any desirable length to accommodate different longitudinal positions of the projectile 31 as determined 18 to the exterior of the body 10 is an opening 44 of varying internal diameter in the inner enlarged portion of which is disposed an igniter device comprising an electric igniter cap 45 attached to the inner end of an igniter conductor pin 46. This igniter device may be constructed in any suitable manner such as, for example, as disclosed in the Phillips Patent No. 2,649,736. Pin 46 which serves both to fasten the igniter in place and to conduct the ignition current to the igniter cap 45 extends outwardly through one or more insulating and sealing bushings in the cap 45, not shown, and through bushings 47 in opening 44, and opening 44 is enlarged at its outer end at 48 in which enlargement is positioned a'contact terminal ring 49 insulated from the gun body andsecured on the threaded end of pin- 46 by a nut 46a. A plug 50 is threadedly secured in the threaded end portion 51 of opening 44 and an O-ring seal 52 may be suitably positioned and secured between the flanged portion of the plug 50 and the body 10 at the outer end of opening 44 to prevent entrance of borehole fluid.

An insulated electrical conductor 53 has one exposed 'end thereof electrically connected and attached to the otherwise, to form thereby a closed, fluid-tight conduit for containing the several electrical conductors which lead, as before-described, from the several electrical igniters of the core sampling projectile propulsion chambers to their respective switch contact terminals 56 of the ignition controller switch 57. A duct b extends downwardly .in body 10 from the lower end of groove 55 through which electrical connection may be made .to the controller of another ygun body which, as hereinbefore mentioned, maybe connected to the lower end of body 10 on threaded pin 29.

.Controller switch 57 is-connected to a source of electric current -by means of an insulated electric conductor 60 contained in the conductor cable 15. Controller 57 may be :of any well .known type such as that disclosed in the Lane Patent No. 2,062,974 or the equivalent, and comprises essentially an electromagnetically actuated stepping .switch having a rotary contact arm which is moved stepwise to sequentially engage a plurality of switch contact points, each'of which is connected to one of. the before-mentioned switch contact terminals 56 which are in turn each connected through a conductor 53 to one .of the electrical igniters 45,each time a current impulse is sent through'conductor 60. After each :ignition .of anigniter cap 45 the rotary contact arm of the controller 57 is stepped to the next succeeding terminal contact, thereby closing a circuit for detonating another igniter cap and so on until all of the charges have been fired.

The-bore36 of projectile 31 is undercut at its rear end and provided with internal'threads 61,.said undercut forming a rearwardly facing shoulder 62. A hollow annular nut 64 is threaded into the threaded portion 61 of the projectile and-secures a ring 65 in seated position against shoulder 62. A flexible projectile retrieving member 66 such as a wire or stranded steel cable has one end thereof secured to ring 65 by suitable anchoring means such as-by being extended through avflared passage 76 in thering 65 and being welded at itstflared end to the surrounding vportion of the ring, and the 'otherend of the cable being secured to .a suitable, preferably swivelable, anchoring means such as a ball 67 attached theretoby suitable means such .as by swaging the ball onto the end of the cable. The ball 67 is seated in a beveled 'or spherical seat 68 formedin the hereinbeforementionedhollow nut 69 which is threaded into the bore 27 of the before-described boss 26 extending from the center of the closure member or breech plug 24. The ball 67 is provided with clearance under thehollow nut 69 to permit it to have a certain amount of freedom for swiveling movement therein. The intermediate portion of flexible member 66 is preferably folded in a figure 8 configuration and disposed substantially wholly within bore 36 of the projectile 31. An approximately conical shaped shield 71 of suitable material such as plastic surrounds the flexible member 66 and is initially disposed within the bore 36 of the projectile as shown in Figure 4, with its smaller end adjacent to nut 69'and ball 67. The base of the shield 71 is compressedin diameter initially to allow it to be inserted into bore 36.

Breech plug or closure member 24 is formed, as best shown in Figure 3, with a plurality of radially disposed notches 72 in its outer end face and an index bar 73 is suitably secured as by screw 74 to 'the exterior of body 10 andhas its free end extending into one of thenotches 72.

The purpose of the notches and indexing bar arrangement is to lock the closure member 24 in place and prevent inadvertent or accidental shifting thereof after being properly set.

Figure 6 shows a modified form of the invention. In this figure the numeral 10a designates a body similar to the hereinbefore described body 16 having a plurality of laterally directed gun bores 120, each gun bore having an undercut portion 120a, a threaded portion 120!) and an inner, rear end portion 1200 of reduced diameter. Portion 1200 is formed with an annular groove 40 in which is retained an O-ring seal 41. An annular nut 24a is threaded into the threaded bore portion 12Gb. The inner end of thegun bore 120 diflers from that of gun bore 18 in that it does not extend entirely through the body 10a and therefore does not require the threaded breech plug or closure member 24 to form a rear end closure thereof, as shown in Figure 4. An internally threaded recess 27a similar to threaded recess 27 shown in Figure 4 is formed, centrally located in the rear end of the gun bore to receive a hollow nut 69 which serves to anchor the anchor ball 67 of the retrieving cable of the projectile 31 in a manner similar to that employed for the projectile of the form shown in Figure 4. An annular, combustible or explosive charge pellet 16 is placed in the cavity or chamber bounded by outer cylindrical surface 32 of the projectile, internal cylindrical surface of bore portion 120a, rearwardly facing curved shoulder portion 34 of the projectile, and the forwardly. facing annular surface of nut 24a. Nut 240 has an internal slot or keyway 24b extending parallel to its axis, cooperating slidably with a key 240 fixed in and extending from the outer surface 32 of projectile 31. By this construction it will be apparent that with the rear end of projectile 31 seated against shoulder 75a at the inner end of bore 120 and secured in such position by shear set screws 43, the position of nut 24a may be threadedly adjusted longitudinally along the axis of the gun bore, and by so changing its position the size of the charge chamber may be increased or decreased to vary the density of the powder charge 16 relative to the volume of the chamber and thus the explosive force of the powder charge may be. altered within suitable limits without changing the amount of the charge itself.

' In the operation of the invention the sidewall sampler tool after assembly with the core sampling projectiles in position in the bores 18 is lowered in the well borehole to the desired depth and conductor 60 is connected to a source of electric current through surface switching apparatus (not-shown) located at the earths surface. At each operation of such surface switching apparatus which applies a current impulse to the circuit; controller 57 1s actuated-stepwise as explained hereinbefore to connect the current source to each switch contact point successively, and each such applied current impulse is thereby connected to a separate one of the igniters, and its associated propulsive charge 16.is fired thereby, and the core sampling projectile of that unit is propelled into the adjacent well wall stratum by the force of the propulsive charge. A generally cylindrical core sample of the formation is cut from the borehole wall and is forced into the interior bore 36 of the sampling projectile. During such propulsive movement of the sampling projectile the flexible members .66 are withdrawn from within the bore of the sampling projectiles. Ordinarily the sampling projectiles after detachment from the borehole wall formation into which they have been fired, drop downwardly in the annular space between the body 10 and the wall of the borehole to the extent permitted by the flexible members 66, and are received partially or wholly within the elongated recessor cavity 28 in the side of the body as shown in'Figure 2. If any core sampling projectile should, for any reason, be retained in the stratum which it has penetrated, it may usually be withdrawn therefrom by a lifting of the tool sufficiently to apply tension to the flexible member 66 to effect such release. If such a pull on the flexible member 66 is necessary to dislodge it from the formation the inner rounded surface 70 of nut 64 over which the retrieving cable would be pulled under such condition will serve to prevent or minimize damage to the cable. 7

The several projectiles are fired in succession starting from the lowermost ones since otherwise flexible member 66 might be cut by later fired higher core barrel projectiles. On firing the projectile, the inertia of shield 71, and the resistance of the air and well fluid thereagainst, will cause the shield to lag behind the projectile. The projectile is propelled with great rapidity away from its position about the shield previously enclosed thereby; as soon as the projectile clears the forward end of the shield, the latter is permitted to expand to' its normal diameter. When the sampling projectiles are shot out of the gun bores, the afterblast causesthe conical hoods or shields 71 to slide down the retrieving cables and cover the rear or upper end openings of the projectiles, as shown in Figure 2, to prevent excessive washing of the core sample contained therein as the apparatus is'moved through the borehole fluid as it is withdrawn from the borehole. As shown in Figure 4, retrieving cables 66 are folded in a figure 8 arrangement, and the opposite end portions thereof are secured to the ring and swivel ball 6'7 respectively without sharp bending or deviation thereof, thereby minimizing the frequency ofoccurrence of severing of the cables. Thus a very high percentage of core barrel recoveries results.

The energy imparted to the core sampling projectiles 31 may be varied by adjustment of the axial position of the breech plug closure 24 shown in Figure 4, thereby determining the initial longitudinal position of the core sampling projectile 31 in the bore 18, or, as hereinbefore mentioned, such energy variation may be effected by adjustment of the axial position of the annular nut 2411 as shown in Figure 6, by which adjustments the lengths and hence the size or volume of the propellant charge chamber is varied. In this manner the effective density of the propellent charge 16 relative to the chamber volume may be varied, and consequently, the propulsive power there-, of may correspondingly be modified without changing the actual load or amount of the propulsive charge itself. Thus the energy imparted to the projectiles may be adjusted to the value best suited for taking samples from the particular types of formations indicated, by the logging method employed, as probably presentin the area being thus examined.

An important feature of the invention is the provision of the closed inner end of the bore 20 which, in the embodiment shown in Figures l5, is provided by the closure member or breech plug 24, which constitutes an improved means for attachment of the retrieving cable 66, which cable is folded in a free, figure 8 arrangement and disposed substantially wholly within the bore of the projectile in such a manner that the cable will unfold smoothly when the gun is fired. In this connection it will be noted that the inner rear end edge of the hollow nut 64 has a radiused curve 70 which will pass smoothly over the retrieving cable when the projectile is fired from the gun barrel and over which a cable may be pulled without damage when it is necessary to dislodge the projectile from the formation which it has penetrated. This nut 64 and ring 65 also aid in some cases in compressing and retaining in the projectile bore some of the samples of soft types of formations. The nut and ring to which the cable is attached may be readily removed after the projectile is recovered from the well and the core sample may then be pressed forwardly out of the bore of the projectile by application of pressure from the breech end, and thus the part of the core sample which was deepest in the formation does not come in contact with the ram or other tool used for its removal, and the core sample therefore will retain the characteristics of the formation from which it was taken. By the provision of a hollowor tubular sampletaking projectile, the surrounding drilling mud through which'the projectile passes when it is fired from the gun is thus allowed an ,initial free passage therethroughand permits'the formation core sample to enter an unobstructed bore of 'the projectile. A further feature of advantage and novelty in this core sampler is the shield or hood 71 which provides a closurefor the rear end of the base of the corefsampling projectile 31 and serves to prevent excessive washing and to minimize contamination of the core in the projectile when the tool is being pulled upward through the well fluid.

WhileFigures 4 and 5 show several modified features of the apparatus of this invention, .someor all of these features may be combined in a single embodiment of the invention.

I It is to be understood that the foregoing is illustrative only of preferred embodiments in the use of the invention, and the invention isnot limited thereby, but may include various modifications and changes made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

' What is-claimed is:

l. A sidewall sampler comprising in combination: a gun body having a shooting bore therein; a hollow, sampletakingprojec'tile in said bore and of substantially the same length as said bore; cooperating means on said gun body and on said projectile forming a chamber intermediate the ends of said bore for receiving a propellent charge and providing an acting surface on .the projectile for said charge for propelling said projectile from said bore; means foradjusting the size of said chamber including a closure member closing the rear end of said bore having means for limiting the rearward position of said projectile in said bore; and a flexible, projectile-retrieving member initially disposed substantially wholly within the hollow of said projectile and having one end thereof secured adjacent the rear end of said bore and the other end thereof secured to said projectile.

2. A sidewall sampler comprisingin combination: a gun body having a shooting bore therein; a hollow, sampletaking projectile in said bore and of substantially the same length as said bore; cooperating means on said gun body and on said projectile forming a chamber intermediate the ends of said bore for receiving a propellent charge and providing an acting surface on the projectile for said charge for propelling said projectile from said bore; adjustable seating means for adjustably positioning said projectile longitudinally of said bore, effective thereby to vary the size of said charge chamber; and a flexible, projectileretrieving member disposed substantially wholly within the hollow of said projectile and having one end thereof secured to said body adjacent the rear end of said bore and the other end thereof secured to said projectile.

'3. A sidewall sampler comprising in combination: a gun body having a shooting bore extending transversely therein, said bore having a rear end closure; a hollow, sample-taking projectile seated in said bore and of substantially the same length as said bore; cooperating means on said gun body and on said projectile forming a chamber intermediate the ends of said bore for receiving a propellent charge and providing an acting surface on the projectile for said charge for propelling said projectile from said bore; adjustable seating means included in said closure for adjustably positioning said projectile longitudinally of said bore, thereby to vary the longitudinal spacing between said cooperating means and thereby to vary the size of said charge chamber; and a flexible, projectile-retrieving member initially disposed substantially WllOliY'Wl'thlIl the hollow of-said projectile and havingone end thereof secured tosaid body adjacent said rear end of said bore and the other end thereof secured to said projectile.

4. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder on the inner surface thereof; a tubular, core cutting projectile in said bore,

having an axial, sample-receiving passage extending therethrough and a rearwardlyfacing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders, adapted to. contain a combustible propellent charge; a closure in the rear end of said bore; and a flexible, projectile-retrieving member initially substantially wholly disposed in said passage and having. one end thereofsecured to said closure and the other end thereof secured to said projectile.

5. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder on the inner surface thereof; a tubular, core cutting projectile in said bore, having an axial, sample-receiving passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders, adapted to contain a combustible propellent charge; a closure in the rear endof said bore; anchor means attached to the inner face of said closure; a swivel connector means attached to said anchor means and having limited freedom for swiveling motion relative to said anchor means; and a flexible, projectile-retrieving member disposed .in said passage and having one end thereof secured to said swivel connector means and the other end thereof secured to said projectile.

6. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder on the inner surface thereof; a tubular, core cutting projectile in said bore,

having an axial, sample-receiving passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders, adapted to contain a combustible propellent charge; a closure member detachably secured in the rear end of said bore; anchor means attached to the inner face of said closure member; a swivel connector means attached to said anchor means and having limited freedom for swiveling motion relative to said anchor means; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said swivel connector means and the other end thereof secured to said projectile.

7. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof; a tubular core cutting projectile in said bore, having an axial sample-receiving passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders adapted to contain a combustible propellent charge; a counterbore formed in the rear end portion of said passage of said projectile forming on the inner surface thereof a rearwardly facing annular attachment shoulder; an annular nut threaded into said counterbore; an anchor ring retained between the inner end of said annular nut and the said attachment shoulder; a closure for the rear end of said bore; anchor means attached to the inner portion of said closure; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said anchor means and the other end thereof secured to said anchor ring.

8. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof; a tubular core cutting projectile in said bore, having an axial passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders adapted to contain a combustible propellent charge; a closure in the rear end of said bore and forming a seat for 9 the rear end of .said projectile;means for limited adjustment of the longitudinal position of said closure in said bore; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said closure and the other end thereof secured to said projectile. g

9. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof; a tubular core cutting projectile in said bore and having an axial passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders adapted to contain a combustible propellent charge; a counterbore formed in the rear end portion of said passage of said projectile forming on the inner surface thereof an internal, rearwardly facing, annular attachment shoulder; an annular nut threaded into said counterbore; an anchor ring retained between the inner end of said annular nut and the said attachment shoulder; a closure in the rear end of said bore; and forming a seat for said projectile; means for limited adjustment of the longitudinal position of said closure in said bore, thereby to vary the longitudinal position of said projectile in said bore and the size of said charge chamber; anchor means on the inner central portion of said closure; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said anchor means on said closure and the other end thereof secured to said anchor ring.

10. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof, the rear end of said bore having internal threads; a tubular core cutting projectile in said bore and having an axial passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders adapted to contain a combustible propellent charge; a closure member positioned in said rear end of said bore, having external threads engageable with said internal threads of said bore and forming an adjustable seat for a rear end portion of said projectile; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said closure and the other end thereof secured to said projectile.

'11. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof, the rear end of said bore having internal threads; a tubular, core cutting projectile in said bore and having an axial passage extending'therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between said shoulders adapted to contain a combustible propellent charge; a closure member positioned in said rear end of said bore, having external threads engageable with said internal threads of said bore and forming a longitudinally adjustable seat for said projectile, adjustment thereof being effective to vary the size of said charge chamber; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said closure member and the other end thereof secured to said pro jectile.

12. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof, the rear end of said bore having internal threads; a tubular, core cutting projectile in said bore and having an axial passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between the inner surface of said bore and the external surface of said projectile and between said shoulders adapted to contain a combustible propellent charge; a counterbore formed in the rear end portion of said passage of said projectile forming on the inner surface thereof an internal, rearwardly facing, annular attachment shoulder; an annular nut threaded into said counterbore; an anchor ring retained between the inner end of said annular nut and the said attachment shoulder; a closure member positioned in said rear end of'said bore and forming a seat for the rear end of said projectile, said closure member having external threads engaging said internal threads of said bore; anchor means on the inner central portion of said closure member; swivel connector means associated with said anchor means; and a flexible, projectile-retrieving member disposed in said passage and having one end thereof secured to said anchor means on said closure member and the other end thereof secured to said anchor ring.

13. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a forwardly facing shoulder formed on the inner surface thereof, the rear end of said bore having internal threads; a tubular, core cutting projectile in said bore and having an axial passage extending therethrough and a rearwardly facing shoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between the inner surface of said bore and the external surface of said projectile and between said shoulders adapted to contain a combustible propellent charge; a counterbore formed in the rear end portion of said passage of said projectile forming on the inner surface thereof an internal, rearwardly facing, annular attachment shoulder; an annular nut threaded into said counterbore; an anchor ring retained between the inner end of said annular nut and the said attachment shoulder; a closure member positioned in said rear end of said bore and forming a seat for the rear end portion of said projectile, said closure member having external threads engageable with said internal threads of said bore and thereby being adjustable longitudinally to vary the initial longitudinal position of said projectile in said bore and thereby to vary the size of said charge chamber; anchor means on the inner central portion of said closure member; and a flexible, projectileretrieving member disposed in said passage and having one end thereof secured to said anchor means on said closure member and the other end thereof secured to said anchor ring.

14. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a coaxially positioned, axially adjustably movable annular member fitting therein and thereby forming an axially movable, forwardly facing shoulder on the inner surface thereof; a tubular, core cutting projectile in said bore having an axial, sample-receiving passage extending therethrough and a rearwardly facingshoulder on the exterior thereof positioned forwardly of said forwardly facing shoulder, there being a chamber thereby formed between the inner surface of said bore and the external surface of said projectile and between said shoulders, adapted to contain a combustible propellent charge, and adjustable in length by axial movement of said axially movable annular member; and a flexible, projectileretrieving member disposed in said passage and having one end thereof secured to said body and the other end thereof secured to said projectile.

15. A sidewall sampler comprising in combination: a body formed with a shooting bore for a projectile and having a coaxially positioned, axially adjustably movable annular member fitting therein and thereby forming an axially movable forwardly facing shoulder on the inner surface thereof; a tubular, core cutting projectile in said bore, having an axial, sample-receiving passage extending therethrough and a rearwardly facing shoulder on the 11. exterior. thereof, positioned forwardly of saidforwardly References Cited the file of this patent facing shoulder, there being a .chamber thereby formed UNITED STATES PATENTS between the inner surface of said here and .the external surface, of saidl projectile and between said. shoulders, 2,962,974 Lane T .r 3 adapted to contain a combustible rpropellentycharge and 5 2,511,408 PQ June 1950 adjustable. in length by axial movement of said axially Phllllps Allg- 1953 movable vannular member; a closure in the rear .end of said bore; and a flexible,projeetile-retrieving member dis- OTHER REFERENCES posed .in said passage and having lonenend thereof secured -56); Q- 271;524,-Sh1llmbefrger Published to said closure andthe other end thereof secured to said 0 M y 2 4 projectile.

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