US3349857A

US3349857A - Coring apparatus

Info

Publication number: US3349857A
Application number: US472623A
Authority: US
Inventors: Alexander B Hildebrandt
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1965-07-16
Filing date: 1965-07-16
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31

Description

Oct. 31, 1967 A, B. HILDEBRANDT 3,349,857

CURING APPARATUS Filed July 16, 1965 PIA-2 ALEXANDER B HILDEBRANDT INVENTOR.

WWEQML ATTORNEY United States Patent 3,349,857 CORIN G APPARATUS Alexander B. Hildebrandt, Tulsa, Okla, assignor to Esso Production Research Company, a corporation of Delaware Filed July 16, 1965, Ser. No. 472,623 8 Claims. (Cl. 175-250) ABSTRACT OF THE DISCLOSURE The present invention relates to apparatus useful in drilling oil 'wells, gas wells and similar boreholes and is particularly concerned with apparatus for use in rotary core drilling operations.

The apparatus employed for the recovery of cores during rotary drilling operations normally includes a core barrel having an outer housing, a concentric inner member into which the core extends, and a passageway between the two through which drilling fluid is circulated. Slips or collets are provided near the lower end of the inner member to serve as a core catcher. These are designed to slide along the core as it is cut and to prevent it from slipping from the barrel as the apparatus is lifted from the borehole. Experience has shown that this type of core catcher often damages relatively soft cores, that such devices are easily clogged or jammed by sand particles and similar fragments, and that severe slippage may take place if the core has to be broken from the formation by lifting the drill string. These and related difliculties are responsible for many of the problems encountered in rotary coring operations.

' The present invention provides improved core drilling apparatus which largely obviates the difficulties outlined above. The apparatus of the invention comprises a core barrel and bit assembly provided with a core catcher which moves outwardly away from the core in response to hydraulic pressure exerted by the drilling fluid. Movement of the apparatus with respect to the core is unimpeded as long as fluid is being circulated. When circulation is interrupted, a spring or other means forces the core catcher inwardly into contact with the core surface. This substantially eliminates damage to soft cores, re-

duces the frequency with which clogging and jamming problems are encountered, and provides a positive means for holding the core so that it can be broken from the underlying formation.

The nature and objects of the invention can best be understood by referring to the following detailed description of a rubber sleeve core barrel and bit provided with the improved core catcher and to the accompanying drawing in which:

FIGURE 1 is a fragmentary vertical elevation, partially in section, of the lower end of coring apparatus pro-, .vided with the core catcher of the invention, and

FIGURE 2 is .a vertical cross-section through a portion of the apparatus of FIGURE 1.

The apparatus shown in FIGURE 1 of the drawing includes the lower portion of a rubber sleeve core barrel generally similar to that depicted in US. Patent 3,012,- 622. This core barrel is provided with an outer cylindrical housing 11 and threads 12 by means of which the housing is attached to the upper end of a core bit. An inner concentric cylindrical member 13 extends downwardly within the housing to provide an annular passage- .above'the collet to a point way 14 through which drilling fluid is circulated into the borehole beneath the bit. Cylindrical member 15 in the barrel serves as the support for a rubber sleeve 16 in which the core 17 is encased as it is cut. Core barrels on this type have been widely used in recent years and will therefore be familiar to those skilled in the art. The invention it not restricted to this particular type of barrel, however, and is instead applicable to any core barrel containing an outer housing, a concentric inner member, and an annular passageway between the two through which drilling fluid may be circulated.

The core bit shown in FIGURE 1 of the drawing includes a body member 18 surfaced at its lower end with a matrix 19 in which diamonds or similar particulate cutting elements 20 are embedded. The matrix is normally formed by sintering, infiltration or similar powder metallurgy techniques. The lower end of the body member contains an axial opening or port into which core 17 extends. A collar 21 having a tapered inner surface 22 projects upwardly within the body member. The tapered surface extends from a shoulder 23 located near the lower end of collar 21 to the upper end of the collar. Ports or nozzles 24 extend through the bottom of the bit at points about the collar to permit the discharge of drilling fluid beneath the tool. These ports may be equally spaced from the core opening or may instead be staggered about the opening. Watercourses 25 extend from the fluid discharge ports outwardly and upwardly across the lower face and gage surfaces of the bit. These may be arranged in a variety of different patterns. Spiral watercourses are sometimes employed in place of the radial channels shown.

The core catcher of the invention is positioned between the lower end of inner member 13 on the core barrel and collar 21 on the bit. The catcher includes a split retaining member of collet 26 having an external flange 27 at its upper end. This flange is employed to hold the collet in place. A series of tapered fingers 28 extend downwardly below the flange. These are shown more clearly in FIGURE 2 of the drawing. The outer faces of the fingers are tapered so that they will seat against tapered surface 22 in collar 21. The inner faces 29 of the fingers extend parallel to the longitudinal axis of the tool assembly and rare roughened or serrated to facilitate the engagement and retention of core 17. The fingers are cut away near their upper ends to facilitate expansion and contraction on the bit.

downwardly around it. An 0 ring or similar member. 31 set in a groove in the lower part of the sleeve provides a seal between the inner wall of the, sleeve and the outer surface of the collanFlange 27 on the collet extends into an annular groove 32 in the innerwall of the sleeve. The external diameter of the flange is slightly greater than the internal diameter of the sleeve adjacent the groove and hence the collet must be compressed slightly to permit its installation. The outer wall of the sleeve extends upwardly above the lower end of inner concentric member 13. An 0 ring 33 is mounted in a groove in the outer surface of the inner member near its lower end to provide a seal between the inner member and sleeve. Spacers 34 at the upper end of the sleeve extend in contact with the inner wall of the bit body and thus hold the sleeve in a concentric position within the body. The sleeve contains an internal shoulder 35 on which helical spring 36 rests. The upper end of this spring bears against the lower end of inner member 13. The sleeve and collet are thus held in a normally downward position with respect to the body of the bit and the core barrel. In this position, the collet is compressed by collar 21 so that the fingers 26 engage the surface of core 17. Movement of the sleeve and collet upwardly with respect of the bit results in expansion of the collet within groove 32. FIG- URE 2 of the drawing shows the collet in the expanded position.

During operation of the apparatus shown in the drawing, drilling fluid is circulated downwardly between the outer housing 11 and inner member 13 of the barrel through passageway 14. This fluid flows into the annular space between body 18 of the bit and sleeve 30 of the core catcher.

Seals

31 and 33 prevent the leakage of fluid into the space within the sleeve. The pressure within the bit body is considerably higher than that beneath the bit and adjacent the core surface because of the pressure drop across ports or nozzles 24. As a result of this difference in pressure, the sleeve moves upwardly against the force of spring 36. As the sleeve and collet 28 rise, the collet expands. The collet fingers slide upwardly on tapered surface 22 in the bit so that the inner surfaces 29 move back away from the core surface. This frees the core from the core catcher and permits movement of the apparatus downwardly about it as the drill string is rotated. As long as circulation of fluid through the tool is continued, the differential pressure on the sleeve holds it in an upward position so that the collet fingers do not engage the core surface. The coring operation can thus be carried out without danger of damaging the surface of the core or clogging the core catcher as the bit advances.

When it is desired to withdraw the apparatus from the borehole, the circulation of drilling fluid is interrupted at the surface. This results in an equalization of the pressure across ports or nozzles 24. In the absence of a differential hydraulic pressure on sleeve 30, spring 36 forces the sleeve downwardly so that fingers 28 on the collet engage the core surface as shown in FIGURE 1 of the drawing. The inner surfaces of the fingers grasp the core with suflicient force to prevent it from slipping from the apparatus as the tool is lifted in the borehole. The core can thus be broken off below the bit and withdrawn in the core barrel to the surface.

It will be understood that the apparatus is not restricted to the specific embodiment depicted in the drawing and that various modifications can be made without departing from the invention. The core catcher disclosed can be employed with any of a variety of different core barrels having an outer housing, a concentric inner member and an annular passageway through which drilling fluid is circulated between the two. It is thus not limited to the rubber sleeve core barrel shown. The coil spring employed to force the collet downwardly so that it contacts the core surface can be replaced with a rubber member or with a spring mounted outside the intermediate member, rather than inside as shown. Slips set in longitudinal grooves and held in place by a split ring can be substituted for the collet. These and other modifications will be apparent to those skilled in the art to which the invention pertains.

What is claimed is:

1. In coring apparatus including an annular drill bit containing ports through which drilling fluid is discharged and a core barrel provided with an outer housing connected to said bit, a concentric inner member extending downwardly in said housing near said bit, and a passageway between said inner member and said housing through which fluid is circulated downwardly to said ports in said bit, the improvement which comprises:

(a) a retaining member positioned within said apparatus near the lower end of said inner member of said core barrel for engaging the surface of a core extending upwardly through said bit into said barrel;

(b) means within said apparatus for normally biasing said retaining member in an inward position in contact with said surface of said core; and,

(c) means in said apparatus for moving said retaining member into an outward position away from said surface of said core in response to an increase in fluid pressure within said passageway.

2. Apparatus as defined by claim 1 wherein said retaining member comprises a collet having a plurality of wedge-shaped fingers.

3. Apparatus as defined by claim 2 wherein said bit includes a tapered surface against which said wedgeshaped fingers extend and said means for biasing said retaining member comprises a spring for forcing said collet downwardly in contact with said tapered surface.

4. Apparatus as defined by claim 3 wherein said means for moving said retaining member into said outward position comprises an axially slidable sleeve to which said collet is connected and against which hydraulic force is exerted as the pressure within said bit is increased.

5. In coring apparatus including an annular drill bit containing ports through which drilling fluid is discharged and a core barrel provided with an outer housing connected to said bit, a concentric inner member extending downwardly in said housing near said bit, and a passageway between said inner member and said housing through which fluid is circulated downwardly to said ports in said bit, the improvement which comprises:

(a) a sleeve extending between said bit and said inner member in said core barrel, said sleeve being axially slidable with respect to said bit and inner member in response to an increase in pressure within said passageway in said bit and core barrel;

(b) means for maintaining a seal between said sleeve and bit;

(c) means for maintaining a seal between said sleeve and inner member;

(d) means for normally biasing said sleeve in a first axial position with respect to said bit and inner member and permitting movement of said sleeve into a second axial position with respect to said bit and inner member in response to an increase in pressure within said passageway; and,

(e) retaining means connected to said sleeve and movable therewith, said retaining means contacting the surface of a core extending through said bit into said core barrel when said sleeve is in said first axial position and extending away from the surface of said core when said sleeve is in said second axial position.

6. Apparatus as defined by claim 5 wherein said retaining means comprises a collet held within an annular groove in the inner surface of said sleeve.

7. Apparatus as defined by claim 6 wherein said collet includes a plurality of wedge-shaped fingers extending downwardly below said sleeve and said bit includes a tapered surface against which said fingers bear as said sleeve moves between said first axial position and said second axial position.

8. Apparatus as defined by claim 7 wherein said means for biasing said sleeve comprises a spring positioned between said sleeve and said inner member in said core barrel.

References Cited UNITED STATES PATENTS 643,082 2/ 1900 Bullock l25l 2,038,793 4/ 1936 Howard 250 X 2,698,737 1/1955 Dean 175-251 CHARLES E. OCONNELL, Primary Examiner.

NILES C. BYERS, Assistant Examiner.

Claims

5. IN CORING APPARATUS INCLUDING AN ANNULAR DRILL BIT CONTAINING PORTS THROUGH WHICH DRILLING FLUID IS DISCHARGED AND A CORE BARREL PROVIDED WITH AN OUTER HOUSING CONNECTED TO SAID BIT, A CONCENTRIC INNER MEMBER EXTENDING DOWNWARDLY IN SAID HOUSING NEAR SAID BIT, AND A PASSAGEWAY BETWEEN SAID INNER MEMBER AND SAID HOUSING THROUGH WHICH FLUID IS CIRCULATED DOWNWARDLY TO SAID PORTS IN SAID BIT, THE IMPROVEMENT WHICH COMPRISES: (A) A SLEEVE EXTENDING BETWEEN SAID BIT AND SAID INNER MEMBER IN SAID CORE BARREL, SAID SLEEVE BEING AXIALLY SLIDABLE WITH RESPECT TO SAID BIT AND INNER MEMBER IN RESPONSE TO AN INCREASE IN PRESSURE WITHIN SAID PASSAGEWAY IN SAID BIT AND CORE BARREL; (B) MEANS FOR MAINTAINING A SEAL BETWEEN SAID SLEEVE AND BIT; (C) MEANS FOR MAINTAINING A SEAL BETWEEN SAID SLEEVE AND INNER MEMBER; (D) MEANS FOR NORMALLY BIASING SAID SLEEVE IN A FIRST AXIAL POSITION WITH RESPECT TO SAID BIT AND INNER MEMBER AND PERMITTING MOVEMENT OF SAID SLEEVE INTO A SECOND AXIAL POSITION WITH RESPECT TO SAID BIT AND INNER MEMBER IN RESPONSE TO AN INCREASE IN PRESSURE WITHIN SAID PASSAGEWAY; AND, (E) RETAINING MEANS CONNECTED TO SAID SLEEVE AND MOVABLE THEREWITH, SAID RETAINING MEANS CONTACTING THE SURFACE OF A CORE EXTENDING THROUGH SAID BIT INTO SAID CORE BARREL WHEN SAID SLEEVE IS IN SAID FIRST AXIAL POSITION AND EXTENDING AWAY FROM THE SURFACE OF SAID CORE WHEN SAID SLEEVE IS IN SAID SECOND AXIAL POSITION.