WO2007001187A1

WO2007001187A1 - Impact hammer for coiled tubing drilling

Info

Publication number: WO2007001187A1
Application number: PCT/NO2006/000245
Authority: WO
Inventors: Per Olav Haughom
Original assignee: Hav Technology As
Priority date: 2005-06-27
Filing date: 2006-06-27
Publication date: 2007-01-04
Also published as: NO20053130L; NO20053130D0; NO325972B1

Abstract

A hydraulic hammer is built up around an inner cylindrical string section (1) and an outer cylindrical mantle consisting of cylindrical sections (4, 6) , and (8) connected to adapters (5) and (7). The impact hammer is driven by liquid pressure provided by choking ingoing liquid flow 10 through a nozzle (32). The liquid pressure is directed through apertures (26, 27) and acts on valve part (25) so that springs (12) and (29) are compressed building up force until valve part (17) with valve faces (19) impacts valve face (15). In this position the volume (36) is enclosed and the pressure increases so that the differential pressure acting on valve part (25) is reduced and the pressure force is overcome by the spring force of spring (29). The valve part (25) now accelerates more rapidly than valve parts (23) and (17) as the spring (29) connected to valve part (25) is more powerful than the spring (12) connected to valve parts (23) and (17) through the string section (1) and locking rings (16) and (22). Due to the greater acceleration of valve part (25) the valve faces are held open until impact against the projecting edge (34) occurs. In this position the valve faces (24) are closed, and the sequence is repeated. The impact frequency is determined by the rate of liquid input and pressure.

Description

IMPACT HAMMER FOR COILED TUBING DRILLING

The present invention relates to an impact hammer, in particular of the kind preferably used in connection with drilling and maintenance operations in oil and gas wells.

With the existing technology, oil and gas wells are generally drilled using a rotating drill string and a drill bit arranged at the bottom end of the drill string. In some cases, a continuous reeled drill string (coiled tubing) is used. The coiled tubing is run into and pulled out of the borehole using an injector. At the bottom end of the coiled tubing there is often provided a liquid motor that rotates the drill bit by means of drilling mud being pumped down through the coiled tubing. A signal cable for directional control and steering is commonly run down through the centre bore of the coiled tubing.

The coiled tubing is also used in connection with the maintenance of production wells that have been in production for a long time and need to be cleaned up in order to maintain the production. In such cases, it is often desirable to remove deposits accumulated in the pipe system. In order to be able to carry out this kind of operations it has shown convenient to use hammering techniques to remove deposits. A hammer is also used in connection with special operations such as, for example, setting of plugs, "fishing operations", opening and closing of valves, "sliding sleeves", etc. The hammer is positioned at the bottom end of the coiled tubing and driven by liquid being pumped down through the coiled tubing.

Current hammering techniques have shown poor efficiency with respect to the functional requirements of the work to be performed. In particular, this is the case for reliability and operational dependability.

With the present invention, a hammer design is provided that makes it possible to improve the efficiency and reliability through a simplified and more robust design of the valve that controls the hammer movement. The invention also simplifies the production process, making the product cheaper and thus viable for use in more cases in which economic criteria are of vital importance.

As compared to the prior art, the present invention represents significant improvements with respect to functionality, efficiency, reliability, and economics.

The invention will now be explained in more detail with reference to an exemplary embodiment, as illustrated in the accompanying drawings, in which: Fig. 1 shows the assembled impact hammer having a liquid inlet.

Fig. 2 shows the hammer design partitioned into sections.

Fig. 3 shows a detailed view of section 2 of fig. 2.

Fig. 4 shows a detailed view of section 3 of fig. 2. Fig. 5 shows a detailed view of section 1 of fig. 2.

The main operating principle of the hammer is that it converts a liquid pressure to a reciprocating movement by having the liquid pressure to compress two springs 12 and 29. When the springs reach a given load a valve opens, and the spring forces accelerate the movable mass so that the kinetic energy is converted to impact energy on impact against a projecting edge 34.

The hammer itself is build up around an inner cylindrical string section 1 having through apertures for liquid flow. Concentric around inner cylindrical string section 1 an outer cylindrical mantle is arranged, consisting of pipe sections 4, 6, and 8 connected by adapters 5 and 7. The end piece 9 imparts the impact energy to tools that are connected to the hammer.

The liquid flow 10 is guided into the end of the cylindrical string section 1. The liquid used for impact energy is flushed out through the apertures 3. The remaining fluid 11 exits the hammer through the outlet end of string section 1. Hydraulic pressure to activate the hammer is built up by a differential pressure across the nozzle 31 in the outlet of string section 1.

The pressure is directed through the apertures 26 and further on through the apertures 27 so that the pressure acts on the piston area 35 and moves the piston 25 against the spring force of springs 12 and 29. The liquid pressure is directed further on through the apertures 28 to valve face 24. The valve part 23 is anchored to string section 1 by means of locking rings 22, so that string section 1 follows the movement of the piston part 25 and valve part 23. The force from piston part 25 is transferred through the valve faces 24, which thereby seals against the liquid pressure.

The springs 12 and 29 are pretensioned through a connection to the inner string section 1. Spring 12 extends through string section 14 with the locking ring 16 against string section 1. Spring 29 is attached to the piston part 25 through the end piece 30 and locking ring 33. The liquid pressure then pretensions springs 12 and 29 until the valve part 17 with valve faces 19 impacts the valve seat 15. In this position the volume 36 is enclosed and the pressure balances on each side of the piston 25, which thereby experiences a reduced force.

The spring force of springs 12 and 29 now overcomes the liquid pressure acting on piston 25, so that piston 25 is set in motion and opens the valve faces 24. At the same time the apertures 26 and 27 are displaced relative to each other to block the inlet.

The spring 20 delays the opening of valve faces 19 so that spring 29 increases the velocity of cylinder part 25 before string section 1 is set in motion. To further ensure that the valve faces 24 are held open in the impact movement, the stiffness of spring 29 is greater than that of spring 12. As a result, valve faces 24 are held in the open position until the end piece 32 attached to string section 1 impacts 34 end piece 9.

During the impact phase the liquid is discharged through the slots 18 in valve part 17 and further on through the space between string section 15 and the adapter 5 to the outlet apertures 3.

Impact against the faces 34 transfers the impact energy to the end piece 9 and further on to a tool mounted thereon.

When the valve part 25 hits the impact shoulder 34 the valve faces 24 are closed, and the sequence is repeated. The impact frequency is determined by the rate of liquid input.

Claims

1. An impact hammer driven by liquid pressure and specially designed for use in drilling and maintenance operations carried out in oil or gas wells using coiled tubing, wherein the impact hammer is designed in such a manner that liquid pressure compresses and releases the force of springs 12 and 29 by opening and closing a valve device consisting of a valve part 25 having valve faces 24 against a valve part 23 and a valve part 17 having valve faces 19, and an intervening spring 20, characterized in that when the valve faces 19 impacts the valve faces 15, the impact hammer is designed in such a manner that the liquid volume 36 is compressed between the valve parts 23 and 17 so that the differential pressure acting on valve part 25 is equalized and the valve faces 24 are opened by the spring force of the spring 29.

2. The impact hammer of claim 1, characterized in that valve part 17 comprises slots 18 for fluid flow.

3. The impact hammer of claims 1 and 2, characterized in that spring 29 has higher stiffness than spring 12.

4. The impact hammer of the preceding claims, characterized in that flow through apertures 26 and 27 is established and blocked by axial displacement of valve part 25.