US3578093A

US3578093A - Method for drilling and coring

Info

Publication number: US3578093A
Application number: US825524A
Authority: US
Inventors: Wayland D Dlenburg
Original assignee: WAYLAND D DLENBURG
Current assignee: WAYLAND D DLENBURG
Priority date: 1969-05-19
Filing date: 1969-05-19
Publication date: 1971-05-11
Anticipated expiration: 1988-05-11

Abstract

A method of drilling bore holes which enables a cylindrical solid core sample to be obtained from a formation. A coring bit together with a core barrel and concentrically arranged drill pipe provides central and annular passageways. The annular passageway is used for circulating fluid to the bit and back up the bore hole annulus while the central passageway provides for the return of drilling fluid and cores. The circulating fluid is forced down through the drill string annulus to the drill bit, and back up through the hole annulus to thereby remove debris and cool the bit in an improved manner. The cores which have been cut by the bit are accumulated within the core barrel and from time to time the pressure of the drilling fluid is increased while the central passageway is opened to the flow of fluid, thereby forcing the fluid to flow into and up through the central passageway, carrying the accumulated cores therewith. A predetermined pressure drop is maintained across the face of the diamond bit by adjusting the bearing pressure thereof with respect to the formation to thereby enable the bit to cooperate with the formation in a manner analogous to the action of a valve.

Description

United States Patent Wayland D. Elenburg P. O. Box 1588, Monahans, Tex. 79756 [21] Appl. No. 825,524 [22] Filed May 19, 1969 Division of Ser. No. 714,551, Mar. 20, 1968, Pat. No. 3,473,517. [45] Patented May 11, 1971 [72] lnventor [54] METHOD FOR DRILLING AND CORING 3,338,322 8/1967 Henderson Examiner-Emest R. Purser Assistant Examiner-Richard E. Favreau Attorney-Marcus L. Bates ABSTRACT: A method of drilling bore holes which enables a cylindrical solid core sample to be obtained from a formation. A coring bit together with a core barrel and concentrically arranged drill pipe provides central and annular passageways. The annular passageway is used for circulating fluid to the bit and back up the bore hole annulus while the central passageway provides for the return of drilling fluid and cores. The circulating fluid is forced down through the drill string annulus to the drill bit, and back up through the hole annulus to thereby remove debris and cool the bit in an improved manner. The cores which have been cut by the bit are accumulated within the core barrel and from time to time the pressure of the drilling fluid is increased while the central 7 passageway is opened to the flow of fluid, thereby forcing the fluid to flow into and up through the central passageway, carrying the accumulated cores therewith. A predetermined pressure drop is maintained across the face of the diamond bit by adjusting the bearing pressure thereof with respect to the formation to thereby enable the bit to cooperate with the forma tion in a manner analogous to the action of a valve.

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MARCUS L. BATES METHOD FOR DRILLING AND CORING CROSS-REFERENCE TO RELATED APPLICATIONS This application is a division of my copending Pat. application Ser. No. 7l4,55l, filed Mar. 20, 1968 now U.S. Pat. No. 3,473,5l7 issued Oct. 21, 1969. BACKGROUND OF THE INVENTION In order to obtain geological samples of formations located in the earths structure, a diamond bit is often utilized which enables a cylindrical elongated sample of the formation to be cut into predetermined lengths, called cores." The core passes through the bit as the diamonds on the face of the bit cut away a portion of the formation while the borehole is being drilled. By using a diamond bit of this design, a more representative sample is obtained as compared to the chip drilling operation" wherein large cuttings or chips are relied upon for analysis. In using drilling and coring apparatus of this type, it has been found satisfactory to carry out the coring operation until a core barrel is tilled with the individual lengths of cores. During the coring operation, the circulation pattern of the drilling fluid can be traced down through the annulus of the drill string and back up through the hole annulus where the fluid flows into a mud pit. When it is desired to retrieve the cores, the central tubing is opened causing the flow path to change. The drilling fluid continues to travel down through the annulus of the drill string but now is caused to reverse its flow path where the major flow occurs back up through the central tubing string, carrying the cores therewith to the surface of the earth. In the past art, the cuttings are carried away by the drilling fluid which is directed through passageways located in the drill bit and which communicate with the hole annulus rather than the central portion of the drill. Accordingly, when it is desired to change the circulation pattern, the bit is usually raised or elevated slightly in order to allow the circulation flow path to occur across the bit and back up through the central passageway, carrying the cores to the surface of the earth. This method of drilling requires tremendous pump pressure inasmuch as the fluid tends to flow along the path of least resistance and is therefore divided into two flow paths, one of which follows the hole annulus, and the other being through the core barrel and up the central tubing.

SUMMARY OF THE INVENTION The present invention comprehends both method and apparatus for carrying out an improved boring and coring operation while forming a borehole. Concentrically arranged drill pipe having a central and annular passageway formed therein for circulating fluid to the bit and for providing a return flow path for obtaining the core is suitably connected to a bit by a combination sub and core barrel. Drilling fluid is forced down through the annulus of the drill pipe or drill string and into close proximity of the diamond or otherwise faced cutting teeth of the bit, with a passageway being radially disposed about the inside central portion of the bit, outwardly of the core receiving annulus. This flow path causes the fluid to be forced with high velocity across the diamonds of the drill bit whereupon the flow then circulates back to the surface of the earth through the hole annulus. Accordingly, the pressure drop across the bit can be controlled by the pressure of the diamonds as they are forced into cutting relationship with respect to the formation. Total flow across the entire bit face maintains the bit cool and clean of debris, and enables the bit to cooperate with the formation with a valvelike action. When it is desired to circulate the accumulated cores out of the core barrel, the fluid pressure is increased a predetermined amount while the bit is maintained in drilling relationship, or close contact with the fonnation to thereby force the major portion of the fluid flow back up the central tubing and pushes the cores to the surface of the earth in-an improved manner. All this time the drilling operation continues since this method provides sufficient flow across the bit to protect the diamond face.

The apparatus used in carrying out the present invention includes the before-mentioned drill bit and drill string with the bit being connected to the string by a sub. The sub supports a core barrelwherein the core barrel is rotatably secured to the sub with the lower marginal end of the barrel being secured in a nonrotating manner to the core which is being cut to thereby prevent rotation of the barrel and accordingly, improving the quality of the core. A valve means located above the ground and associated with the central tubing, along with the valvelike action of the bit enables the above method to be carried out. 4

It is therefore a primary object of the present invention to provide a method of obtaining cores from a borehole by circulating the cores back to the surface of the earth by an improved flow pattern.

Another object of the present invention is the provision of a method which enables coring operations to be carried out by an improved circulation pattern.

A further object of the present invention is the provision of a bit having an improved flow path across a coring or cutting face thereof.

Another object of the present invention is the provision of an improved combination which includes a coring bit, sub, and core barrel and which enables cores to be obtained in an improved manner.

The above objects are attained in accordance with the present invention by the provision of concentrically arranged drill pipe which are connected to a bit and to a nonrotating core barrel which all cooperate together to provide an improved flow path across a bit.

Other objects of the present invention will become apparent to those skilled in the art as the description proceeds. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatical representation of a cross section of the earths structure with the present well boring apparatus being positioned therein in order to explain the operation of the invention;

7 FIG. 2 is an enlarged cross-sectional view of part of the device seen in FIG. I;

FIG. 3 is a fragmentary cross-sectional view taken along line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary cross-sectional representation of the invention which has been taken along line 4-4 of FIG. 2. DETAILED DESCRIPTION OF THE INVENTION FIG. 1 schematically sets forth a portion of a well drilling apparatus 10 which is in the act of boring a hole into the earths structure 11. Part of the apparatus is located above the surface of the earth as seen at 12 while the remainder of the apparatus is located below the surface of the earth. A high pressure inlet 14 provides a flow of drilling fluid to the uppermost part of a swivel or the like, schematically illustrated by numeral I6, while fluid is returned from the borehole either by means of a gooseneck l8 upwardly along the hole annulus 20, depending upon the circulation pattern desired.

A rotatable drill pipe 22 telescopingly receives a longitudinally extending, centrally positioned tubing 24 therewithin, with the drill pipe and tubing being connected together from several joints in the usual manner to form a drill string, as is known to those skilled in the art. At the terminal end of the drill string there is located an outer barrel or sub 25 which carries a diamond bit 26 threadedly attached to the lower depending end thereof. As the bit is rotated by the drill string, a core 28 is formed within the central aperture of the bit, with the core extending upwardly where it is received within a core barrel 30. The core is broken into uniform lengths such as indicated by the arrow at numeral 32., The core barrel is rotatably attached to the outer barrel or sub by the illustrated journal means 34. The sub includes radially spaced-apart passageways extending therethrough for isolating the drilling fluid from the bearing, and to enable the fluid to flow to the drill bit as well as to provide a means for the flow of the accumulated cores back up through the central tubing from time to time.

The rotatable barrel includes spaced-apart guide means 33 for maintaining the lower terminal end of the barrel properly aligned with the outer barrel, so as to assure cutting a uniform core.

Numerals

36 and 38 indicate spaced-apart hypothetical voids, sometime called fractures" or fissures." The void 36 has been drilled through or penetrated, and fluid can escape up hole annulus 40 into the void. The bit has also penetrated to a position where it rests on the bottom of the void 38 and drilling fluid can escape thereinto also. The purpose of illustrating the two spaced-apart voids will be realized later on.

Looking now to FIG. 2, wherein an enlarged cross-sectional view of the before-mentioned outer and inner barrel and bit are shown in detail. It should be understood that the device of FIG. 2 is connected to the drill string and related apparatus of FIG. 1. The annulus formed between the inner and outer tubing provides an annular passageway 44 with the core barrel being attached to the sub by means of a bearing such as seen at 46. A collar 48 threadedly engages the core barrel in a manner to capture the bearing therebetween as illustrated at 50. The central portion 52 of the barrel extends downwardly to where it threadedly engages member 54, the depending end of which forms a shoulder at 55. A core breaker 58 commences near shoulder 55 and longitudinally extends in an upward and outward direction for a limited length with respect to the inside peripheral wall surface of the core barrel. The core breaker is preferably circumferentially coextensive with the inside peripheral wall surface for approximately thereof, and is several times longer in length as compared to its width. The vertical distance between the core breaker and the drill bit face determines the length of the individual cores.

Threadedly attached to the lower terminal end of the core breaker member is a cylindrical downwardly converging core catcher housing 60 having a key 62 thereon, and which includes vertically spaced-apart splines thereon (not shown) which cooperate with similar spaced-apart splines provided on the outside peripheral wall surface of the inverted frustoconical core catcher 64, the details of which are best seen in FIG. 3. The lower tenninal end portion of the core barrel terminates at 61. The inside face of the drill bit is provided with grooves 67, having a bottom-most portion 68, to thereby leave a passageway between the lower terminal end of the inner barrel and the inside of the bit.

The face of the bit containing the diamonds is generally seen at 66, with the lower inside portion of the bit being provided with the before-mentioned grooves which permit the passage of fluid to be forcibly bent across the inside peripheral portion 69 which forms the central aperture of the bit. Accordingly, a passageway 70 is formed between the outer peripheral surface of the various members which forms the core barrel and the inside peripheral wall surface of the outer barrel. The passageway continues as seen at 73 to where it branches into a multiplicity of radially spaced-apart passageways 74 which are drilled through the before-mentioned sub 42 so as to communicate at 75 with the annular passageway formed by the drill string.

Looking again now to FIG. 3, in conjunction with FIGS. 1 and 2, wherein the before-mentioned core catcher is better il lustrated. As seen illustrated therein, as stated above, the core catcher includes a multiplicity of splines 80 which cooperate with similar but oppositely disposed splines 82 formed on the inside peripheral wall surface of core catcher housing 60. Edge portion 84 of the expandable core catcher cooperates with the before-mentioned key 62 with the edge portion 84 being slidably and guidably received by the key to thereby enable reciprocation of the core catcher between the limits provided by shoulder 55 and the illustrated position of the core catcher in FIG. 2.

As seen in FIG. 4, the lower guide means 33 are each preferably located 90 apart and extend for a limited distance about the annulus 73 so as to leave passageway 72 therebetween. The core barrel rotates against the inside surface area forrned by the outwardly directed guide member.

Looking again to FIG. I, there is further seen illustrated an inlet valve .92 with leads to the high pressure source of drilling fluid. Outlet valve 94 controls the fluid flow' through gooseneck 18 to thereby permit the cores to be caught on a conventional mud screen 96 as the cores are circulated from the borehole.

In order to catch elongated sections of core which extend from more than 5 inches in length, the core can alternatively be telescopingly received through the tubing 97, which includes a hinged flange .98 to permit the core catching cylindrical portion 99 to be separated from lower portion 97. Drain apertures 102 are provided in the tubing 97. It will be realized by those skilled in the art that the

section

97, 98, 99,-and 102 is best placed with its central axis in alignment with the central axis of the tubing 24, i.e., elements 97-l02 replace the gooseneck I8.

OPERATION In operation, with the apparatus of the present invention assembled as schematically illustrated in FIG. I, the diamond bit continuously cuts a core. As the core enters the central aperture formed by inside peripheral portion 69 of the bit, the core forces its way upwardly through the core catcher. Since the core catcher has splines which cooperate with the splined inner surface of the core catcher housing, the core barrel remains affixed to the telescopingly received core as the outer barrel rotates about the journal formed by bearing 46.

As the coremoves into the barrel, it contacts the core breaker which places a sheer or transverse force on the core body, whereupon the core breaks into uniform lengths with each length of core being accumulated within the core barrel. Since the core breaker and barrel are stationary with respect to the core, the core sample is received in uniform undamaged cylindrical pieces.

During this stage of the operation, drilling fluid enters through inlet 14 where it travels down the annulus of the drill string and at the fluid is diverted into a multiplicity of radially spaced-apart passageways 74, where the fluid then travels down through passageway 73 and between the four spacedapart guide means, to where the fluid can now enter annulus 70. From annulus 70 the fluid travels through the passageways formed between the lower depending end 61 of the core barrel and through the multiple grooves 67 formed on the inside lower wall portion of the bit. Since valve 94 of the gooseneck is closed, the fluid must now flow across the diamonds located in the cutting face of the drill bit and back up the hole annulus, carrying the cuttings from the formation with it during its upward travel back to the surface of the earth. The rate of drilling during this time is preferably controlled by observing the pressure drop across the face of the bit rather than by utilizing a weight indicator in the conventional manner. A pressure drop of pounds across the face of the drill bit is desirable for most applications, although this figure will usually be changed when encountering unusual formations.

For example, a 2 /e-inch core, received withing a ZA-inch tube, using a 4/s-inch bit attached to a 4k-inch outside diameter drill pipe provided excellent core samples and exceptionally long bit service when using a drilling fluid flow rate of 40 gallons per minute when coring, and 150 gallons per minute when circulating the cores to the surface.

The pressure drop across the bit face was adjusted by lifting the bit face free of the formation floor, observing the hydrostatic head at 14, and cautiously setting the bit down until the indicated pressure increased an additional 150 pounds per square inch, which is the pressure drop across the bit. This value provides a reasonable rate of penetration while maintaining the diamonds of the bit sufficiently cooled and cleaned to thereby prolong the bit life. It should be understood that the recited pressure drop of 150 pounds is measured across the cutting surface of the bit, and is exclusive of the hydrostatic head or the friction head of the drill pipe.

While the above operation is described as being carried out by using a liquid drilling mud," it is also contemplated to use air or other compressible fluid, as well as a combination thereof.

the hole annulus, is restricted to thereby enable a substantial rise in pressure at the drill stem. The flow restriction is then removed from the central tubing by opening the valve associated therewith, whereupon the pressure drop across the cores located in the core barrel forces the cores up through the central passageway of the drill string and through the gooseneck, much like the operation of a piston within a cylinder.

Often it is desirable to use a combination of air and liquid, especially where a strong aquifier is encountered. In this instance, it is preferable to circulate the cores to the surface by restricting the flow of fluid from the bore hole by utilizing the valve action between the drill bit and the formation. Compressed gas is supplied to the drill string annulus, and when the pressure reaches a suitable value, opening of the valve associated with the central tubing enables circulation of the cores to the surface.

Where air alone fails to properly circulate the cores to the surface, it is possible to admix water or mud with the air which is being used as the return fluid, to thereby provide more body to the fluid in order to better circulate the cores from the core barrel to the gooseneck.

The improved circulation pattern includes forcibly flowing fluid through passageways 67 located on the lower inside face of the bit, wherein the flow is forced to proceed directly across the bit face to where the drilling fluid then returns up the hole annulus. This improved flow pattern causes all of the drilling fluid to be forced across the drilling face, and when encountering voids or fissures, such as seen at 38, escape of drilling fluid into the formation does not result in destruction of the diamonds as usually occurs when using a conventional circulation system. Therefore, even under conditions wherein there is a complete loss of circulation, the improved bit is safely provided with adequate fluid flow ther'eacross, so long as fluid enters at 92.

Accordingly, by forcibly pumping fluid from inside the bit to an area externally of the bit assures the cutting face of the bit of always having a cleaning and cooling fluid. This improved method enables the diamonds located in the cutting face of the bit to engage the formation at a smaller cutting depth, while still maintaining a satisfactory rate of penetration. Should the diamonds suddenly engage a harder or tougher formation,vthe individual diamonds will not be torn from the bit and lost.

As indicated by the arrow at numeral 90, the cutting face of the bit seats against the undrilled or remaining portion of the formation with an action similar to that of a valve; that is, when the bit bears against the formation with a large force, the pressure drop across the face of the bit must be increased in order to maintain the same flow rate of drilling fluid, and with thebit slightly displaced from the formation, a larger flow of fluid is required in order to maintain the same pressure drop. Therefore, the cooperation between the cutting face of the bit and the formation which is to be removed can be controlled by observation of the pressure drop as measured at 14.

As the core is cut, the fluid within the central tubing and core barrel is quiescent which eliminates the heretofore undesirable erosion or washing of the accumulated samples.

As a core is being cut (as illustrated at 28 in FIG. 1), the core catcher (seen at 64 in FIG. 2) travels upwardly within its housing as it expands to accept the core therethrough. The

core catcher continues its upward travel until the upper edge portion of the core catcherabuts against face 55 of the barrel, thereby permitting the core to slide through the catcher and into the barrel. This action permits the edge portions 84 of the core catcher to expand with the core being forced therebetween and up into the barrel where it bears against the inwardly sloped face of the core breaker 58. The core breaker imparts sufficient sheer or lateral force into the core to cause it to break into uniform lengths whereupon the cores may accumulate or stack up within the core barrel until it is desired to'circjulate them back to the' surface of the earth in the before-described manner. 7

As further seen in FIG. 2, in conjunction with FIG. 1, the diamond bit is removably attached in a conventional manner to the outer tube 25 which in turn is threadedly attached to the sub 42 with the sub threadedly attaching the entire combination to the drill string. The entire device is easily broken down into its various components by merely removing the outer tube 25 and the inner tube connector 45 so as to enable the bearing 46 to be pressed therefrom. The core breaker and the lowermost member which contains the core catcher are threadedly disengaged from the main body of the core barrel by the indicated threaded connections.

The down time required for the coring operation of the present invention is negligible, which, coupled with the increased efficiency of operation brought about by utilizing the present method enables a substantial increase of footage drilled per unit of time.

While the core barrel of the present invention is of the nonrotating type, it is contemplated to use the present invention in conjunction with other types of core barrels.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive'and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

I claim:

1. A method of drilling boreholes and obtaining cores therefrom, wherein'a drill bit is connected to concentrically arranged drill pipe whichforms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:

l. circulating drilling fluid down through the drill string annulus, across the cutting face of the drill bit, and back up through theborehole annulus, while'the bit cuts cores to form the borehole;

2. accumulating the cut cores in a core barrel;

3. arranging the core barrel in joumaled relationship with respect to the drill pipe and stationary with respect to the formation by interlocking the core-which is being cut with structure associated with the core barrel;

- 4. retrieving the cores'of step (2) by increasing the flow of drillingfluid while maintaining the bit in cutting relationship to the formation and circulating a major portion of the fluid from the drill string annulus into the core barrel and back up the central passageway to thereby provide an increased pressure drop across the cores in the core barrel which causes the accumulated cores to move from the core barrel to the surface of the earth.

2. A method of drilling boreholes and obtaining cores therefrom, wherein a drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:

l. circulating drilling fluid down through the drill string annulus, across the cutting face of the drill bit, and back up through the borehole annulus, while the bit cuts cores to form the borehole;

2. breaking the core into convenient lengths which will facilitate their removal from the borehole;

3. accumulating several lengths of cut core in a core barrel,

4. retrieving the cores of step (3) by increasing the flow of drilling fluid while maintaining the bit in cutting relationship to the formation to thereby provide an increased pressure drop across the cores in the core barrel;

5. circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway when it is desired to retrieve the accumulated cores from the core barrel to the surface of the earth.

3. The method of claim 2 wherein the following additional step is included:

6. interlocking the core which is being cut with structure associatedwith the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.

4. The method of claim 2 wherein step (4) includes the following additional steps:

a. restricting the flow of fluid from the borehole annulus by using the action of the drill bit against the formation as a valve means;

b. supplying a source of compressible fluid pressure to the annulus of the drill string;

c. releasing the flow restriction from the central passageway to thereby permit the flow of liquid, cores, and compressed fluid therethrough.

5. A method of drilling boreholes and obtaining cores therefrom, wherein the drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:

1. using liquid drilling mud as the drilling fluid to thereby cool the drill bit while lubricating the hole annulus, and wherein the flow to the bit is caused to flow across the bit face;

2. Controlling therate of penetration of the bit by maintaining a constant pressure drop across the face of the bit to thereby prolong the life of the bit;

3. circulating drilling fluid down through the drill string annulus, across the cutting face of the drill bit, and back up through the borehole annulus, while the bit cuts cores to form the borehole;

4. accumulating the cut cores in a core barrel;

5. retrieving the cores of step (4) by increasing the flow of drilling fluid while maintaining the bit in cutting relationship to the formation to thereby provide an increased pressure drop across the cores in the core barrel; and, circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway to thereby cause the accumulated cores to move from the core barrel to the surface of the earth.

6. The method of claim 5 wherein the following additional step is included:

6. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.

7. The method of claim 5 wherein step (5) includes the following additional steps: I

c. releasing the flow restriction from the central passageway to thereby permit the flow of liquid, cores, and compressed fluid tlterethrough.

8. A method of drilling boreholes and obtaining cores therefrom, wherein a drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:

l. circulating drilling fluid down through the drill string an nulus, across thecutting face of the drill bit, and back up through the borehole annulus, while the bit cuts cores to form the borehole;

2. accumulating the cut cores in a core barrel;

3. retrieving the cores of step (2) byv the following additional steps:

a. restricting the flow of fluid from the borehole and from the central passageway of the drillstring while increasing the pressure at the drill string annulus to thereby cause a rise in pressure at the drill bit;

b. maintaining the bit in cutting relationshipto the formation;

c. removing the flow restriction from the central passageway and circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway to thereby provide a pressure drop across the cores of step (2) in order to force the cores up through the central passageway of the drill string.

9. The method of claim 8 wherein the following additional step is included:

4. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.

10. A method of drilling boreholes and obtaining cores therefrom, wherein the drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:

. accumulating the cut cores in a core barrel; restricting the flow of fluid from the central passageway of the drill pipe while carrying out step (2); 4. retrieving the cores of step (2) by carrying out the following steps:

0. increasing the flow pressure of the drilling fluid while maintaining the bit in cutting relationship to the forma- HOD d. releasing the flow restriction from the central passageway to thereby permit a major portion of the fluid to flow from the drill string annulus, into the core barrel, and back up the central passageway so as to move the accumulated cores from the core barrel to the surface of the earth.

I]. The method of claim 10 wherein the following additional step is included:

5. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.

12. The method of claim 11 and including the following additional steps:

5. continuously flowing compressed fluid into the drill string annulus before and after step (40) is carried out; and

6. injecting liquid into the compressed fluid flow as the cores travel up the central passageway.

Claims

2. accumulating the cut cores in a core barrel;
2. accumulating the cut cores in a core barrel;
2. accumulating the cut cores in a core barrel;
2. A method of drilling boreholes and obtaining cores therefrom, wherein a drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:
2. breaking the core into convenient lengths which will facilitate their removal from the borehole;
2. Controlling the rate of penetration of the bit by maintaining a constant pressure drop across the face of the bit to thereby prolong the life of the bit;
3. circulating drilling fluid down through the drill string annulus, across the cutting face of the drill bit, and back up through the borehole annulus, while the bit cuts cores to form the borehole;
3. accumulating several lengths of cut core in a core barrel;
3. The method of claim 2 wherein the following additional step is included:
3. arranging the core barrel in journaled relationship with respect to the drill pipe and stationary with respect to the formation by interlocking the core which is being cut with structure associated with the core barrel;
3. restricting the flow of fluid from the central passageway of the drill pipe while carrying out step (2);
3. retrieving the cores of step (2) by the following additional steps: a. restricting the flow of fluid from the borehole and from the central passageway of the drill string while increasing the pressure at the drill string annulus to thereby cause a rise in pressure at the drill bit; b. maintaining the bit in cutting relationship to the formation; c. removing the flow restriction from the central passageway and circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway to thereby provide a pressure drop across the cores of step (2) in order to force the cores up through the central passageway of the drill string.
4. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.
4. retrieving the cores of step (2) by increasing the flow of drilling fluid while maintaining the bit in cutting relationship to the formation and circulating a major portion of the fluid from the drill string annulus into the core barrel and back up the central passageway to thereby provide an increased pressure drop across the cores in the core barrel which causes the accumulated cores to move from the core barrel to the surface of the earth.
4. retrieving the cores of step (2) by carrying out the following steps: a. restricting the flow of fluid from the borehole annulus by using the action of the drill bit against the formation as a valve means; b. supplying a source of compressible fluid pressure to the annulus of the drill string; c. increasing the flow pressure of the drilling fluid while maintaining the bit in cutting relationship to the formation; d. releasing the flow restriction from the central passageway to thereby permit a major portion of the fluid to flow from the drill string annulus, into the core barrel, and back up the central passageway so as to move the accumulated cores from the core barrel to the surface of the earth.
4. The method of claim 2 wherein step (4) includes the following additional steps: a. restricting the flow of fluid from the borehole annulus by using the action of the drill bit against the formation as a valve means; b. supplying a source of compressible fluid pressure to the annulus of the drill string; c. releasing the flow restriction from the central passageway to thereby permit the flow of liquid, cores, and compressed fluid therethrough.
4. retrieving the cores of step (3) by increasing the flow of drilling fluid while maintaining the bit in cutting relationship to the formation to thereby provide an increased pressure drop across the cores in the core barrel;
4. accumulating the cut cores in a core barrel;
5. retrieving the cores of step (4) by increasing the flow of drilling fluid while maintaining the bit in cutting relationship to the formation to thereby provide an increased pressure drop across the cores in the core barrel; and, circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway to thereby cause the accumulated cores to move from the core barrel to the surface of the earth.
5. circulating a major portion of the fluid from the drill string annulus, into the core barrel, and back up the central passageway when it is desired to retrieve the accumulated cores from the core barrel to the surface of the earth.
5. A method of drilling boreholes and obtaining cores therefrom, wherein the drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:
5. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.
5. continuously flowing compressed fluid into the drill string annulus before and after step (4c) is carried out; and
6. injecting liquid into the compressed fluid flow as the cores travel up the central passageway.
6. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.
6. The method of claim 5 wherein the following additional step is included:
6. interlocking the core which is being cut with structure associated with the core barrel to thereby enable the core barrel to remain stationary with respect to the formation and to rotate with respect to the drill pipe.
7. The method of claim 5 wherein step (5) includes the following additional steps: a. restricting the flow of fluid from the borehole annulus by using the action of the drill bit against the formation as a valve means; b. supplying a source of compressible fluid pressure to the annulus of the drill string; c. releasing the flow restriction from the central passageway to thereby permit the flow of liquid, cores, and compressed fluid therethrough.
8. A method of drilling boreholes and obtaining cores therefrom, wherein a drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:
9. The method of claim 8 wherein the following additional step is included:
10. A method of drilling boreholes and obtaining cores therefrom, wherein the drill bit is connected to concentrically arranged drill pipe which forms a central and annular passageway for circulating fluid to and from the bit, comprising the steps of:
11. The method of claim 10 wherein the following additional step is included:
12. The method of claim 11 and including the following additional steps: