AU599533B2

AU599533B2 - Downhole recirculating hammer

Info

Publication number: AU599533B2
Application number: AU31325/89A
Authority: AU
Inventors: Ian Graeme Rear
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-24
Filing date: 1989-03-15
Publication date: 1990-07-19
Anticipated expiration: 2009-03-15
Also published as: AU3132589A

Description

p i 599533 COMMONWEALTH OF AUSTRALIA Patents Act 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Class Int. Class Related Art: TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: Actual Inventor: Address for Service:- FOi 1540 1 5 /03/8 IAN GRAEME REAR 60 Clavering Road, Bayswater, in the State of Western Australia, Commonwealth of Australia IAN GRAEME REAR Wray Associates Primary Industry House 239 Adelaide Terrace Perth Western Australia 6000.

Complete Specification for the invention entitled: "DOWNHOLE RECIRCU.LATING HAMMER" The following statement is a full description of this invention, including the best method of performing it known to me:- 1

F

2 THIS INVENTION relates to fluid operated downhole hammers and in particular hammers of the reverse circulation type.

Reverse circulation hammers are designed to pass rock cuttings and detritus from ground formations being drilled through the centre of the hammer in order that uncontaminated samples of the well formation being drilled are passed to the surface or outer atmosphere for collection without passing out through the annular space formed between the walls of the hole being drilled and the hammer and casing connecting the hammer to the drill machine at the surface.

In one form the invention resides in a fluid operated hammer comprising a tubular housing a top sub mounted to o one end of the housing and a drill bit support mounted to I the other end of the housing, a central tube extending t axially through the housing between the top sub and drill bit support and communicating with axial passageways U provided in the top sub and drill bit support, a feed tube concentrically received over the central tube and mounted to the top sub to extend into the housing and terminate intermediate of the top sub and drill bit support, a fluid flow passageway provided through the drill bit support, a piston slidably received in the housing over the feed tube for reciprocation between a first position adjacent the top sub and a second position abutting the drill bit support, the one end portion of the piston adjacent the drill bit support having a reduced diameter and the inner face of the housing adjacent the drill bit support having a reduced diameter portion to define a surface substantially complementary to the one end portion of the piston, fluid porting means in the feed tube and piston to sequentially admit fluid into a first space between the top sub when the piston is at or near its first position and into a second space between the end portion of the piston, the inner face of the housing and the inner end of T the reduced diameter portion of the housing when the -3piston is at or near the second position, the end portion of the piston and the reduced diameter portion of the housing disengaging when the piston is at an intermediate position to allow for the escape of fluid from the second space through the fluid passageway.

The invention will be more fully understood in the light of the following description of one specific embodiment.

The description is made with reference to the accompanying drawings of which:- Figure 1 is a sectional elevation of the hammer in the impact position; Figure 2 is a sectional elevation of the hammer with the piston in the raised position; S' Figure 3 is an additional elevation of the piston at an intermediate position;

C

Figure 4 is a sectional elevation of the hammer in the blowdown position; and Figure 5 is a cross section along lines 5-5 of Figure 3.

4$t £4 E The embodiment is directed to a reverse circulation 6.€ L downhole hammer comprising a substantially tubular housing 11 with a top sub 12 mounted to one end and a drill bit support 13 mounted at the other end. The drill but support accommodates a drill bit 14 which is axially 1 slidable within the drill bit support and is retained in the drill bit support through a bit retaining ring in the drill bit support engaging an enlargement 16 provided on the anvil 17. The engagement between the drill bit chuck 13 and the drill bit 14 is through a series of mating 4 splines which provide a fluid flow between the inner end of the drill bit chuck 13 and the outer end thereof.

The top sub 12 supports a central tube 18 which extends through the top sub and through the housing to be slidably engaged within the central axial bore 19 of the drill bit 14. The end of the central tube 18 which is located in the region of the top sub 12 is adapted for engagement with the drill string and/or a cross over sub. The portion of the bore 19 of the drill bit 14 which slidably engages the central tube 18 is provided with an annular bush 20 which slidably and sealingly engages the outer face of the central tube 18. The top sub 12 also supports a feed tube 21 which extends from the top sub 12 concentrically over the central tube 18 and terminates intermediate of the top sub 12 and the drill bit chuck 13.

The feed tube is connected through the top sub to a pressurised fluid supply. Seals are provided at the innermost end of the feed tube 21 for engagement with the outer face of the central tube 18 to close off the inner end of the feed tube. The housing slidably supports a piston 22 which is slidably and sealingly receivable over the feed tube 21 for reciprocation between a position at which it is in close abutting relationship with the anvil 17 of the drill bit 14 the impact position as shown at Figure 1) and a raised position where its other end is closely adjacent the top sub the raised position as shown at Figure The walls of the feed tube are provided with two sets of apertures 23a and 23b. The first set of apertures 23a comprise three or more sub-sets of axially spaced apertures of differing dimensions which periodically and sequentially are brought into engagement with a first set of passageways 24a in the piston 22 to allow for admission of fluid into the first space between the top sub and the other end of the piston. The second set of apertures 23b comprise a single sub-set of r apertures which are periodically brought into engagement with a second set of passageways 24b in the piston which provides for the admission of fluid into the space at the one end of the piston. The end portion 25 of the one end of the piston 22 is formed with a reduced diameter and is associated with an annular piston stem seal bearing 26 located adjacent the inner end of the drill bit chuck 13 to define a portion of the inner face of the housing of reduced diameter which has a complementary diameter to that of the reduced diameter end portion 25 of the piston 22. The outer face of the reduced diameter and portion of the piston is formed with a set of circumferentially spaced axial scallops or flutes 27 while the inner end of the pistons stem seal bearing is formed with a set of circumferentially spaced axial flutes 28.

0SS t When in the impact mode as shown at Figure 1 fluid is r admitted into the second space defined between the reduced diameter and portion 25 of the piston, the inner end of CtCthe stem seal bearaing 26 and the side wall of the housing 11 to increase the fluid pressure therein and drive the piston towards the top sub end. Such driving action is maintained until the end of the reduced diameter end portion 25 oZ the piston is engaged with the flutes 28 of the piston stem seal bearing 26 at which time fluid in the second space is caused to exhaust from the housing through the fluid passageways defined between the drill bit and drill bit chuck. Subsequently fluid is sequentially admitted into the first space between the top sub and the other end of the piston to slow to piston down, stop the piston, and subsequently drive the piston towards the Sanvil 17 of the drill bit 14. At an intermediate position as shown at Figure 3 the first space opens into the central bore of the piston 22 through the first set of passageways 24a and fluid is permitted to exhaust therefrom into the space between the lower end of the 6 6 anvil and the one end of the piston 22 whereby it is then exhausted through the fluid passageway between the drill bit 14 and drill bit support 13. At this point in time the second space has been sealingly isolated by engagement of the end of the reduced diameter end portion 25 engaging the side walls of the piston stem seal bearing 26 whereby after impact fluid admitted into the second space again causes the piston to be raised towards the top sub end to the raised position as shown at Figure 2.

When in the blowdown position as shown at Figure 4, whereby the drill bit 14 is allowed to drop away from the lower end of the drill bit support 13, such that the flange 18 of the anvil 17 is in engagement with the drill bit support rings 15, the piston is brought into close abutting relationship with the piston stem seal bearing.

The piston is maintained in that position as a result of fluid being admitted directly from both the first and second set of apertures 23a and 23b into the first space between the top sub 12 and the other end of the piston.

Such fluid is cause to exhaust from that first space through the first set of passageways into the central bore of the piston and then through the fluid passageways provided between the drill bit support 13 and drill bit 14. in addition the lowermost of the first set of apertures 24a communicates through the second set of passageways 23b in the piston into the second space between the reduced diameter portion 25 and the piston stem seal bearing 26 and is caused to flow through the flutes 28 provided. in the reduced diameter portion 25 and T 30 then to the fluid passageway between the drill bit chuck 13 and drill bit 14.

The continued impact of the piston on the anvil of the bit exerts a continual repetitive force by the cutting end of the bit on the rock in the ground formation with which the 7 bit is in contact with, causing the rock to spall or beak to be dislodged. The outside diameter of the housing and hammer assembly is only marginally smaller than the drill bit cutting diameter and the spalled rock or dislodged ground formation, forms a small annular area which restricts or stops the passage of the rock detritus from travelling upwards past the exterior.face of the hammer assembly. The holes in the face of the drill bit connected to the inner bore of the bit in turn to the inner tube of the hammer offer unrestricted access to the surface with a subsequent large pressure drop between the t high pressure fluid being passed to the hammer and exiting past the splines of the bit and chuck and the outer S atmosphere at the surface. This causes the rock detritus to pass out through the inner tube of the hammer allowing the bit cutting head to have free contact with fresh rock or undisturbed ground formation.

It should be appreciated that the scope of the present invention need not be limited to the particular scope of the embodiment described above.

C r

Claims

1. A fluid operated hammer comprising a tubular housing a top sub mounted to one end of the housing and a drill bit support mounted to the other end of the housing, a central tube extending axially through the housing between the top sub and drill bit support and communicating with axial passageways provided in the top sub and drill bit support, a feed tube concentrically received over the central tube and mounted to the top sub to extend into the housing and terminate intermediate of the top sub and drill bit support, a fluid flow passageway provided through the drill nit support, a piston slidably received in the housing over the feed tube for reciprocation between a first position adjacent the top sub and a second position abutting the drill bit support, the one end portion of the piston adjacent the drill bit support having a reduced diameter and the inner face of the housing adjacent the drill bit support having a reduced diameter portion to define a surface substantially 1 complementary to the one end portion of the piston, fluid porting means in the feed tube and piston to sequentially admit fluid into a first space between the top sub when the piston is at or near its first position and into a second space between the end portion of the piston, the inner face of the housing and the inner end of the reduced diameter portion of the housing when the piston is at or near the second position, the end portion of the piston and the reduced diameter portion of the housing disengaging when the piston is at an intermediate position to allow for the escape of fluid from the second space S through the fluid passageway.

2. A fluid operated hammer as claimed at claim 1 wherein the reduced diameter portion of the housing wall is provided by a removable annulus supported from the housing. f-

3. A fluid operated hammer as claimed claim 1. wherein fluid from the first space is exhausted from the first space to the fluid passageways through the fluid porting in the piston and the space between the base of the piston central tube when the piston is intermediate to the first and second position.

4. A fluid operated hammer as claimed at claim 2 wherein fluid from the first space is exhausted from the first space to the fluid passageways through the fluid porting in the piston and the space between the base of Ir the piston central tube when the piston is intermediate to I I the first and second position. s rI A fluid operated hammer substantially as herein c described with reference to the accompanying drawings. Dated this FIFTEENTH day of MARCH 1989. IAN GRAEMB REAR Applicant I WKAY ASSOCIATES, Perth, Western Australia, S Patent Attorneys for the Applicant.