WO2014165894A1

WO2014165894A1 - Improved core drilling system and apparatus therefor

Info

Publication number: WO2014165894A1
Application number: PCT/AU2013/000401
Authority: WO
Inventors: Leslie Michael Anderson
Original assignee: Leslie Michael Anderson
Priority date: 2013-04-08
Filing date: 2013-04-17
Publication date: 2014-10-16

Abstract

An improved core drilling system including a drill string, an inner core barrel assembly, an outer core barrel assembly connected to a drill means at a lower end which by rotation drills the core sample for removal from the drilling hole, and a retrieval tool that connects the inner tube of the inner core barrel assembly to a wireline cable and hoist for retrieving core samples, the retrieval tool including an overshot [11].

Description

IMPROVED CORE DRILLING SYSTEM AND APPARATUS THEREFOR

Field of the Invention

The present invention relates to an improved core drilling system and apparatus therefor and in particular to a core drilling system that uses a wireline system for obtaining drilling core samples from deep drilling holes.

The invention has been developed primarily for use with Q series and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

Background of the Invention

Drilling for core samples allows observation of subterranean formations within the earth at various depths for many different purposes. For example, by drilling a core sample and testing the retrieved core, scientists can determine what materials, such as petroleum, precious metals, and other desirable materials, are present or are likely to be present at a desired depth. In some cases, core sampling can be used to give a geological timeline of materials and events. As such, core sampling may be used to determine the desirability of further exploration in a particular area.

In order to properly explore an area, many core samples can be required from varying depths. In some cases, core samples are retrieved from thousands of metres below ground-level. In such cases, retrieving a core sample can be time consuming and a costly process of removing the entire drill string from the borehole.

It has been known since about 1960 to use a faster wireline core drilling system which can include a core retrieval assembly that travels or trips in and out of the drill string by using a wireline cable and hoist.

The components of such a drilling system can include various components of the core barrel retrieval system listed below:

a) Overshot assembly is dropped, or pumped, into the drill string to retrieve the inner tube assembly via wireline cable and hoist. b) Locking coupling threads to the drill rod string and provides a hardened mating surface against which the core barrel inner tube assembly latches ride while drilling.

c) Adapter coupling mates between the locking coupling and core barrel outer tube, providing the pocket into which the head assembly latches deploy.

d) Head assembly provides latching and pivoting spearpoint mechanisms to allow insertion and retrieval of the inner tube assembly, a bearing assembly to allow the inner tube to remain stationary and avoid sample damage while drilling, and fluid pressure operating indications and fluid control valves.

e) Outer-tube houses the inner tube assembly and connects to the diamond products cutting the hole. The increased wall thickness of the outer tube provides additional stiffness for directional control and a tighter hole annulus for increased fluid velocity and rapid cuttings evacuation for bit performance.

f) Inner-tube captures the core sample as drilling progresses. Multiple inner-tubes can be assembled with couplers or extensions to accept longer core samples.

g) Inner- tube stabilizer is seated in the reaming shell, or in mated outer tube extensions, the replaceable and reversible inner tube Stabilizer provides centralizing for improved sample recovery, and a bearing between the stationary inner tube and the rotating outer tube.

h) Core lifter is a hardened steel, split collar with a tapered body that mates to a tapered socket in the core lifter case. In a core breaking operation, the drill string is lifted off bottom and the core sample begins to slide out of the inner tube. Grip features on the inner surface of the core lifter catch the moving core sample and pull the core lifter towards the smaller end of the tapered socket in the core lifter case. The core lifter is constricted against the core sample and retains it after it has broken, allowing retrieval to surface.

i) Core lifter case mates to the inner tube and houses the core lifter in a tapered socket which controls movement of the core lifter. As the drill string is lifted during a core breaking operation, the core lifter case bottoms out on the inside of the drill bit transferring the pullback load from the drill string to the core lifter until the core sample breaks.

j) Stop ring is a hardened steel snap ring designed to seat into a mating groove, and retain the core lifter in the core lifter case. The very efficient sampling technique of wireline core drilling system, makes it possible for the core sample to be retrieved from the bottom of the hole without removing the entire rod string. To retrieve the core sample, an overshot is lowered inside the drill rods on a wireline cable until it latches onto the spearhead point of the core barrel head assembly. Positive latching lifting dogs securely attach, and the core barrel inner tube containing the core sample is retracted to the surface using the wireline cable and winch.

While wireline systems can be more efficient than retracting and extending the entire drill string, the time to trip the core sample tube in and out of the drill string still often remains a time- consuming portion of the drilling process. The slow tripping rate of the core retrieval assembly of some conventional wireline systems can be caused by several factors. For example, the core retrieval assembly of some wireline systems may include a spring-loaded latching mechanism. Often the latches of such a mechanism may drag against the interior surface of the drill string and, thereby, slow the tripping of the core sample tube in the drill string. However restriction of flow of drilling fluid inside the drill string, and restrictive outer diameters of apparatus create a backflow hydraulic pressure that limits the rate at which the core sample tube can be tripped in and out of the borehole.

Looking at a general structure of known wireline systems there are clearly limitations on the structure of the core retrieval assembly of some wireline systems including:

k) Complexity of apparatus

1) Restricted fluid flow which restricts descent

m) Limitation on fine tuning external shapings

n) Fundamental of catastrophic nature of restricting water flow to drill bit to keep cool and clean.

It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

The present invention seeks to provide an improved core drilling system and apparatus therefor, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative. This application increases the productivity of the core drilling system. The system includes a drill string, an inner core barrel assembly, an outer core barrel assembly, and a retrieval tool that connects the inner core barrel assembly to a wireline cable and hoist. The inner core barrel assembly comprises a latching mechanism. The latching mechanism contains a timing mechanism that retains the latches in either a semi-engaged or retracted position until it is activated or deactivated.

The inner tube / backend assembly also comprises new dual fluid path porting.

Accordingly, the drilling system significantly increases productivity and efficiency in core drilling operations by reducing the time required for the descent of the drilling apparatus. Over an extended drilling distance of over 1000 metres descent time can decrease by up to 70%. Accordingly a first aspect of the present invention is the increased shift time available for drilling, time which was previously lost to tube tripping.

According to a first aspect of the present invention, an improved core drilling system and apparatus therefor is provided. Other aspects of the invention are also disclosed. It can be seen that the improved inner tube backend system and apparatus obtains its improvement in efficiency by combination of one or more of the following:

a) Use of dual fluid paths

b) No mechanism, device or valves capable of interrupting, restricting or reducing the flow of fluid to cool and clean the drill bit.

c) Increased fluid flows through the inner tube

d) Increased fluid flows due to reduction and streamlining of assembly body.

e) Use of fluid flow to rotate inner tube during descent

f) Use of dual fluid paths to give a clear and sustained landing signal.

g) A low cost connector sub between the inner tube and backend that also serves as the seat for a new and improved high flow check valve.

h) Simple low maintenance design.

i) A high strength recovery spearpoint that by its shape and spring tension maintains position. The improved inner tube backend system and apparatus can obtains its improvement in efficiency by use of dual fluid paths between descent mode and operating mode and preferably the improved inner tube backend system and apparatus obtains its improvement in efficiency by no mechanism, device or valves capable of interrupting, restricting or reducing the flow of fluid to cool and clean the drill bit; thereby increasing fluid flows through the inner tube and increasing fluid flows due to reduction and streamlining of assembly body.

The dual fluid paths between descent mode and operating mode can be formed to have the first fluid path having fluid flowing through the inner tube and expelled via three high flow ports (in the tube connector) cut at an angle so as to impart spin to the inner tube, with all fluid flowing past the (reduced diameter) of the bearing assembly and entering tripping ports thus by-passing the external landing shoulder, whereby the core tube assembly descends with fluid being pumped into the drill string, and wherein the wings of the latches are held in a semi retracted position by the internal diameter of the drill pipe, and the tines of the timer are not able to engage with the cutouts in the latches (until such time as the latches deploy into the adaptor coupling pocket and engage the locking coupling).

The second fluid path can be formed for entering and exiting above and below a circumferential landing shoulder formed by entering drill ports in an external circumferential surface leading through internal channel to exit drill ports below a circumferential landing shoulder wherein upon the inner tube assembly landing (arriving in the latched in, drilling position) the landing shoulder on the inner tube assembly forms a seal with the landing ring located in the outer tube; wherein the latches (under spring pressure) are able to deploy into the increased diameter of the pocket in the adaptor coupling, the tynes of the timer enter the cutouts in the latches allowing the timer, and the latch case attached thereto, to descend whereby the descent of the latch case closes the tripping ports and diverts all flow through the drill ports. Preferably, the improved inner tube backend system and apparatus obtains its improvement in efficiency by use of fluid flow to rotate inner tube during descent with the inner tube (high flow) exit ports being located at the lower end of the tube connector and with the exit porting at an angle provide the rotation effect of the inner tube during descent.

Below the latches are the fluid channels, input drill ports extend through channels from opposing sides towards an inner axial channel that feeds through a valve to outwardly extending drill ports at a lower level than the input drill ports wherein due to the outer dimensions of the core barrel including a retainer and landing shoulder engages a landing ring in in the outer tube, which forms a seal on landing in the drilling position, at which position peripheral fluid in the down pipe feeds into the input drill ports and is metered out the drill port exits by valve, whereby there is never complete restriction of flow below the exit drilling ports and therefore always provides fluid for cleaning and cooling drill bit and thus eliminates possibility of damage. The invention also provides a method of drilling including the core tube assembly descends with fluid being pumped into the drill string. The wings of the latches are held in a semi retracted position by the internal diameter of the drill pipe, and the tines of the timer are not able to engage with the cutouts in the latches (until such time as the latches deploy into the adaptor coupling pocket and engage the locking coupling). During descent fluid flowing through the inner tube is expelled via three high flow ports (in the tube connector) cut at an angle so as to impart spin to the inner tube, all fluid flows past the (reduced diameter) of the bearing assembly and enters the tripping ports thus by-passing the external landing shoulder, because there are no obstacles to the flow, flow is increased, on exiting the tripping ports the fluid flows past the reduced size of the latch body assembly, because of the increased flow the assembly descends more rapidly. Upon the inner tube assembly landing (arriving in the latched in, drilling position) the landing shoulder on the inner tube assembly forms a seal with the landing ring located in the outer tube. The latches (under spring pressure) are able to deploy into the increased diameter of the pocket in the adaptor coupling, the tynes of the timer enter the cutouts in the latches allowing the timer, and the latch case attached thereto, to descend whereby the descent of the latch case closes the tripping ports and diverts all flow through the drill ports. A timing signal occurs as due to the big reduction of flow passage, the fluid pressure rises giving a clear and sustained signal that the assembly is in place to commence drilling. During drilling all fluid flows through the inlet drill ports and then through a central orifice in a spring mounted self-cleaning valve and out the drill exit ports which because of reduced flow capacity of the orifice, pressure is maintained in the drill string, at any flows capable of cooling the bit, thus ensuring a safer less risky drilling operation especially in holes without fluid return and because there is no mechanism, device or valves to impede or restrict the flow of fluid to the bit, the risk of sticking, bogging or burning the bit is greatly reduced. For retrieval of the core tube assembly the overshot, suspended on the wireline is descended into the drill string to engage the spearpoint mounted on the top of the latch body assembly when the overshot is raised the latch case is retracted disengaging the timer and the tripping ports are opened allowing for increased through flow of fluid on the ascent.

Brief Description of the Drawings

Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

• Figures 1A and IB are front and side elevations of an overshot in accordance with a preferred embodiment of the present invention;

• Figures 2A and 2B are perspective and exploded views of the overshot of Figures 1A and IB

• Figure 3 are perspective views of the three main elements of the overshot of Figures 1A and IB

• Figures 4A and 4B are cross sectional views of head assembly core barrel inner tube top portion in accordance with a preferred embodiment of the present invention at 90 degrees axial rotation to each other and Figure 4C is a cross sectional view of head assembly core barrel inner tube bottom portion with a preferred embodiment of the present invention; and

• Figures 5A and 5B are cross sectional views of head assembly core barrel inner tube top portion in accordance with another preferred embodiment of the present invention at 90 degrees axial rotation to each other and Figure 5C is a cross sectional view of head assembly core barrel inner tube bottom portion with another preferred embodiment of the present invention. Description of Embodiments

It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features. Referring to the drawings there is shown an improved core drilling system and apparatus therefor which includes a head assembly connectable to the core tube, the core tube therefore has an inner tube backend assembly with top part 50A screw mounted on tube connector 50B and topped by a spear point 51 that can be retrieved by engaging with an overshot assembly 11 attached to a wireline. The outer tube (not shown) has at a lower end a diamond strengthened circular coring bit which by rotation drills the core for removal from the drilling hole.

A particular improvement of the overshot 11 in the present invention is the ability to disengage the overshot from the inner tube via a signal from the driller lifting and lowering the overshot body, in the event of the inner tube being trapped in the outer tube. This function also serves to lower the inner tube into position in dry holes where the fluid level is so low in the rod string as to prove dangerous to allow the tube assembly to free fall. A particular improvement of the overshot of the present invention is the inclusion of a central rotator 13 between an overshot head 12 and an overshot base portion 14.

In operation a lifting and lowering of the overshot by wireline will lift the outer tube (of the overshot) and by means of a translator, which engaged by fingers from an inner tube connected to the outer tube, will translate vertical movement into rotational movement of the outer tube. By rotating the outer tube and the rotator, rotational movement of an unlatching sleeve is achieved. The unlatching sleeve on reaching a cut out descends under spring pressure thereby maintaining the lifting dogs in the unlatch position, which position is achieved by the mating shapes of the spearpoint pin (on the inner tube backend) and the lifting dogs.

Referring to Figures 4A, 4B and 4C there is shown a head assembly with a core barrel for connection to the core tube. The core barrel has an inner tube backend structure topped by a spearpoint 51 that forms a positive latching to the overshot 11 connected by wireline to enable retrieval of the inner tube assembly. The spearpoint 51 is mounted on a spear cap 52 and spring 53 to resiliently mount the spearpoint 51. A retaining pin 54 extends across the axially extending core barrel 12 and below which is spring 56 engaging a lower U-shaped timer 57 that can move its two spaced tynes into and out of engagement with matching cutouts of a pair of scissor cross latches 58 mounted on lower latch pins 60 and with latch springs 61. This acts as a timer in order to time the engagement / disengagement so that drilling only takes place on a clear and sustained signal that the latches are deployed in the drilling position and that the tripping port is closed producing the signal. It should be noted that there is no other way for a landing signal to be generated.

The spring 56 tends the tynes to engage the latches 58. The scissor cross latches 58 further include outer wings that form the outermost extremity.

Below the latches are the fluid channels. Input drill ports 62 extend through channels from opposing sides towards an inner axial channel that feeds through a valve to outwardly extending drill ports 63 at a lower level than the input drill ports 62. Due to the outer dimensions of the core barrel including a retainer 15 and landing shoulder engages a landing ring in in the outer tube, which forms a seal on landing in the drilling position. At this position peripheral fluid in the down pipe feeds into the Input drill ports 62 and is metered out the drill port exits 63 by valve. This valve can have dimension of 3/16 of an inch and provide metered flow. It can also be seen that there is no restriction of flow below the exit drilling ports and therefore always provides fluid for cleaning and cooling drill bit and thus eliminates possibility of damage.

The inner tube (high flow) exit ports 66 are located at the lower end of the tube connector 50B 15 and with the exit porting at an angle provide the rotation effect 67 of the inner tube during descent.

In operation the following steps occur:

a. The core tube assembly 50A and 50B descends with fluid being pumped into the drill string, the wings of the latches 58 are held in a semi retracted position by the internal diameter of the drill pipe, and the tines of the timer 57 are not able to engage with the cutouts in the latches (until such time as the latches deploy into the adaptor coupling pocket and engage the locking coupling)

b. During descent fluid flowing through the INNER TUBE is expelled via three high flow ports 66 (in the tube connector) cut at an angle so as to impart spin to the inner tube, all fluid flows past the (reduced diameter) of the bearing assembly and enters the tripping ports (FLUID PATH ONE ) thus by-passing the external landing shoulder 64, because there are no obstacles to the flow, flow is increased, on exiting the tripping ports the fluid flows past the reduced size of the latch body assembly, because of the increased flow the assembly descends more rapidly. c. Upon the inner tube assembly landing (arriving in the latched in, drilling position) the landing shoulder 64 on the inner tube assembly forms a seal with the landing ring located in the outer tube.

d. The latches (under spring pressure) are able to deploy into the increased diameter of the pocket in the adaptor coupling, the tynes of the timer 57 enter the cutouts in the latches allowing the timer, and the latch case attached thereto, to descend. The descent of the latch case closes the tripping ports and diverts all flow through the drill ports 62 and 63.(FLUID PATH TWO)

e. Because of the big reduction of flow passage, the fluid pressure rises giving a clear and sustained signal that the assembly is in place to commence drilling. f. During drilling all fluid flows through the inlet drill ports 62 (FLUID PATH TWO) and then through a central orifice in a spring mounted self-cleaning valve and out the drill exit ports 63. Because of reduced flow capacity of the orifice, pressure is maintained in the drill string, at any flows capable of cooling the bit, thus ensuring a safer less risky drilling operation especially in holes without fluid return. Because there is no mechanism, device or valves to impede or restrict the flow of fluid to the bit, the risk of sticking, bogging or burning the bit is greatly reduced.

g. For retrieval of the core tube assembly 50A, 50B the overshot 11, suspended on the wireline is descended into the drill string to engage the spearpoint 51 mounted on the top of the latch body assembly. When the overshot is raised the latch case is retracted disengaging the timer and the tripping ports are opened allowing for increased through flow of fluid on the ascent.

A particular improvement of the core barrel of this embodiment of the present invention in Figures 4A, 4B and 4C is the reduced outer dimensions of the square shape and therefore higher fluid flow past the latchbody..

A particular improvement of the core barrel of this embodiment of the present invention is the removal of need for peripheral shut off valves, which restricts outer dimensions; and can catastrophically interrupt the flow of cooling / cleaning fluid to the bit. A first flow path occurs with the 35 latches in the lifted position (both in ascent and descent) the timer in a blocked position (by the latches) and therefore the tripping ports opened to increased fluid flows. The second flow path occurs when the landing shoulder engages into the landing ring, the latches deploy into the pocket in the adaptor coupling, the timer, latch case and tripping port plugs descend closing off the tripping ports and thereby diverting water flow into the drilling ports. As shown at Figure 4C. The orifice at 3/16 of an inch but is able to deliver 12 gallons per minute at 100 to 150 PSI.

A particular improvement of the core barrel of this embodiment of the present invention is the use of expulsion of fluid from the inner tube angled to provide rifling effect in descent.

A particular improvement of the core barrel of this embodiment of the present invention is the landing signal / fluid metering valve.

A particular improvement of the core barrel of this embodiment of the present invention is the improved spearpoint A particular improvement of the core barrel of this embodiment of the present invention, is the configuration and use of a timer to control opening and closing of fluid path one, divert flow and deliver a clear and sustained latched in / landing signal.

Referring to Figures 5 A, 5B and 5C there is shown a inner tube backend assembly for connection to the core tube topped by a spearpoint that forms a positive latched connection to an overshot connected by wireline to enable retrieval of the inner tube assembly.

Interpretation

Embodiments:

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the above description of example embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the Detailed Description of Specific Embodiments are hereby expressly incorporated into this Detailed Description of Specific Embodiments, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Different Instances of Objects

As used herein, unless otherwise specified the use of the ordinal adjectives "first", "second", "third", etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking, or in any other manner.

Specific Details

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. Terminology

In describing the preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "forward", "rearward", "radially", "peripherally", "upwardly", "downwardly", and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

Comprising and Including

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" are used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Any one of the terms: including or which includes or that includes as used herein is also an open term that also means including at least the elements/features that follow the term, but not excluding others. Thus, including is synonymous with and means comprising.

Scope of Invention

Thus, while there has been described what are believed to be the preferred embodiments of the invention, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the scope of the invention. For example, any formulas given above are merely representative of procedures that may be used. Functionality may be added or deleted from the block diagrams and operations may be interchanged among functional blocks. Steps may be added or deleted to methods described within the scope of the present invention.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms. Industrial Applicability

It is apparent from the above, that the arrangements described are applicable to the mining industries.

Claims

1. An improved core drilling system including a drill string, an inner core barrel assembly, an outer core barrel assembly connected to a drill means at a lower end which by rotation drills the core sample for removal from the drilling hole, and a retrieval tool that connects the inner tube of the inner core barrel assembly to a wireline cable and hoist for retrieving core samples, the retrieval tool including an overshot.

2. An improved core drilling system according to claim 1 wherein the inner core barrel assembly includes a latching mechanism.

3. An improved core drilling system according to claim 2 wherein the latching mechanism contains a timing mechanism that retains the latches of the latching mechanism in either a semi-engaged or retracted position until it is activated or deactivated.

4. An improved core drilling system according to claim 1 wherein the inner tube / backend assembly also comprises a dual fluid path porting wherein the time required for the descent of the drilling apparatus to decrease descent time.

5. An improved core drilling system according to claim 1 wherein an improved core drilling system and apparatus therefor is provided, wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by combination of one or more of the following:

o) Use of dual fluid paths between descent mode and operating mode;

p) No mechanism, device or valves capable of interrupting, restricting or reducing the flow of fluid to cool and clean the drill bit;

q) Increased fluid flows through the inner tube;

r) Increased fluid flows due to reduction and streamlining of assembly

body;

s) Use of fluid flow to rotate inner tube during descent

t) Use of switching from first to second of dual fluid paths to give a clear and sustained landing signal;

u) A low cost connector sub between the inner tube and backend that also serves as the seat for a new and improved high flow check valve;

v) A simple low maintenance design; and w) A high strength recovery spearpoint that by its shape and spring tension maintains position.

6. An improved core drilling system according to claim 1 wherein an improved core drilling system and apparatus therefor which includes a head assembly connectable to the core tube, the core tube therefore has an inner tube backend assembly with top part screw mounted on tube connector and topped by a spear point that can be retrieved by engaging with an overshot assembly attached to a wireline.

7. An improved core drilling system according to claim 1 wherein the overshot is able to disengage the overshot from the inner tube via a signal by lifting and lowering the overshot body.

8. An improved core drilling system according to claim 7 wherein the overshot includes a central rotator between an overshot head and an overshot base portion.

9. An improved core drilling system according to claim 7 or 8 wherein in operation a. a lifting and lowering of the overshot by wireline will lift the outer tube (of the overshot) and

b. by means of a translator, which engaged by fingers from an inner tube connected to the outer tube, will translate vertical movement into rotational movement of the outer tube, and

c. by rotating the outer tube and the rotator, rotational movement of an unlatching sleeve is achieved,

whereby the unlatching sleeve on reaching a cut out descends under spring pressure thereby maintaining the lifting dogs in the unlatch position, which position is achieved by the mating shapes of the spearpoint pin (on the inner tube backend) and the lifting dogs.

10. An improved core drilling system according to claim 1 wherein a head assembly includes a core barrel for connection to the core tube, with the core barrel having an inner tube backend structure topped by a spearpoint that forms a positive latching to the overshot connected by wireline to enable retrieval of the inner tube assembly.

11. An improved core drilling system according to claim 10 wherein the spearpoint is mounted on a spear cap and spring to resiliently mount the spearpoint.

12. An improved core drilling system according to claim 1 wherein a retaining pin extends across the axially extending core barrel and below which is spring engaging a lower U- shaped timer that moves its two spaced tynes into and out of engagement with matching cutouts of a pair of scissor cross latches mounted on lower latch pins and with latch springs wherein this acts as a timer in order to time the engagement / disengagement so that drilling only takes place on a clear and sustained signal that the latches are deployed in the drilling position and that the tripping port is closed producing the signal.

13. An improved core drilling system according to claim 12 wherein the spring tends the tynes to engage the latches and wherein the scissor cross latches further include outer wings that form the outermost extremity.

14. An improved core drilling system according to claim 1 wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by use of dual fluid paths between descent mode and operating mode.

15. An improved core drilling system according to claim 14 wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by no mechanism, device or valves capable of interrupting, restricting or reducing the flow of fluid to cool and clean the drill bit; thereby increasing fluid flows through the inner tube and increasing fluid flows due to reduction and streamlining of assembly body.

16. An improved core drilling system according to claim 14 or 15 wherein dual fluid paths between descent mode and operating mode comprises the first fluid path having fluid flowing through the inner tube and expelled via three high flow ports (in the tube connector) cut at an angle so as to impart spin to the inner tube, with all fluid flowing past the (reduced diameter) of the bearing assembly and entering tripping ports thus bypassing the external landing shoulder, whereby the core tube assembly descends with fluid being pumped into the drill string, and wherein the wings of the latches are held in a semi retracted position by the internal diameter of the drill pipe, and the tines of the timer are not able to engage with the cutouts in the latches (until such time as the latches deploy into the adaptor coupling pocket and engage the locking coupling).

17. An improved core drilling system according to claim 14, 15 or 16 wherein dual fluid paths between descent mode and operating mode comprises the second fluid path entering and exiting below a circumferential landing shoulder formed by entering drill ports in an external circumferential surface leading through internal channel to exit drill ports below a circumferential landing shoulder wherein upon the inner tube assembly landing (arriving in the latched in, drilling position) the landing shoulder on the inner tube assembly forms a seal with the landing ring located in the outer tube; wherein the latches (under spring pressure) are able to deploy into the increased diameter of the pocket in the adaptor coupling, the tynes of the timer enter the cutouts in the latches allowing the timer, and the latch case attached thereto, to descend whereby the descent of the latch case closes the tripping ports and diverts all flow through the drill ports.

18. An improved core drilling system according to claim 1 wherein an improved core drilling system and apparatus therefor is provided, wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by use of fluid flow to rotate inner tube during descent.

19. An improved core drilling system according to claim 18 wherein the inner tube (high flow) exit ports are located at the lower end of the tube connector and with the exit porting at an angle provide the rotation effect of the inner tube during descent.

20. An improved core drilling system according to claim 12 wherein an improved core drilling system and apparatus therefor is provided, wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by use of switching from first to second of dual fluid paths to give a clear and sustained landing signal.

21. An improved core drilling system according to claim 18 wherein an improved core drilling system and apparatus therefor is provided, wherein the improved inner tube backend system and apparatus obtains its improvement in efficiency by a low cost connector sub between the inner tube and backend that also serves as the seat for a new and improved high flow check valve.

22. An improved core drilling system according to claim 19 wherein below the latches are the fluid channels, input drill ports extend through channels from opposing sides towards an inner axial channel that feeds through a valve to outwardly extending drill ports at a lower level than the input drill ports wherein due to the outer dimensions of the core barrel including a retainer and landing shoulder engages a landing ring in in the outer tube, which forms a seal on landing in the drilling position, at which position peripheral fluid in the down pipe feeds into the input drill ports and is metered out the drill port exits by valve, whereby there is never complete restriction of flow below the exit drilling ports and therefore always provides fluid for cleaning and cooling drill bit and thus eliminates possibility of damage.

23. An improved core drilling system according to claim 20 wherein the valve has dimension of 3/16 of an inch and provides metered flow.

24. A method of drilling including the following steps of:

a. The core tube assembly descends with fluid being pumped into the drill string, the wings of the latches are held in a semi retracted position by the internal diameter of the drill pipe, and the tines of the timer are not able to engage with the cutouts in the latches (until such time as the latches deploy into the adaptor coupling pocket and engage the locking coupling);

b. During descent fluid flowing through the inner tube is expelled via three high flow ports (in the tube connector) cut at an angle so as to impart spin to the inner tube, all fluid flows past the (reduced diameter) of the bearing assembly and enters the tripping ports thus by-passing the external landing shoulder, because there are no obstacles to the flow, flow is increased, on exiting the tripping ports the fluid flows past the reduced size of the latch body assembly, because of the increased flow the assembly descends more rapidly;

c. Upon the inner tube assembly landing (arriving in the latched in, drilling position) the landing shoulder on the inner tube assembly forms a seal with the landing ring located in the outer tube;

d. The latches (under spring pressure) are able to deploy into the increased diameter of the pocket in the adaptor coupling, the tynes of the timer enter the cutouts in the latches allowing the timer, and the latch case attached thereto, to descend whereby the descent of the latch case closes the tripping ports and diverts all flow through the drill ports;

e. A timing signal occurs as due to the big reduction of flow passage, the fluid pressure rises giving a clear and sustained signal that the assembly is in place to commence drilling;

f. During drilling all fluid flows through the inlet drill ports and then through a central orifice in a spring mounted self-cleaning valve and out the drill exit ports which because of reduced flow capacity of the orifice, pressure is maintained in the drill string, at any flows capable of cooling the bit, thus ensuring a safer less risky drilling operation especially in holes without fluid return and because there is no mechanism, device or valves to impede or restrict the flow of fluid to the bit, the risk of sticking, bogging or burning the bit is greatly reduced;

g. For retrieval of the core tube assembly the overshot, suspended on the wireline is descended into the drill string to engage the spearpoint mounted on the top of the latch body assembly

h. when the overshot is raised the latch case is retracted disengaging the timer and the tripping ports are opened allowing for increased through flow of fluid on the ascent.

25. A method of drilling according to claim 24 wherein the core barrel is the reduced outer dimensions of the square shape and therefore higher fluid flow past the latchbody.

26. A method of drilling according to claim 24 wherein a first flow path occurs with the latches in the lifted position (both in ascent and descent) the timer in a blocked position (by the latches) and therefore the tripping ports opened to increased fluid flows.

27. A method of drilling according to claim 24, 25 or 26 wherein the second flow path occurs when the landing shoulder engages into the landing ring, the latches deploy into the pocket in the adaptor coupling, the timer, latch case and tripping port plugs descend closing off the tripping ports and thereby diverting water flow into the drilling ports.

28. A method of drilling according to claim 27 wherein the orifice at 3/16 of an inch and able to deliver of the order of 12 gallons per minute at 100 to 150 PSI.

29. A method of drilling according to claim 24 wherein the core barrel uses expulsion of fluid from the inner tube angled to provide rifling effect in descent.

30. A method of drilling according to claim 24 wherein the core barrel includes an landing signal / fluid metering valve.

31. A method of drilling according to claim 24 wherein the core barrel includes an improved spearpoint

32. A method of drilling according to claim 24 wherein the core barrel includes the configuration and use of a timer to control opening and closing of fluid path one, divert flow and deliver a clear and sustained latched in / landing signal.

33. A method of drilling according to claim 24 including an inner tube backend assembly for connection to the core tube topped by a spearpoint that forms a positive latched connection to an overshot connected by wireline to enable retrieval of the inner tube assembly.