BACKGROUND OF THE INVENTION

Field of the Invention

[0001] Embodiments of the present invention generally relate to a downhole cutting tool. More particularly, the embodiments relate to a downhole water/ abrasive cutter for use with a safety valve.

Description of the Related Art

[0002] A downhole safety valve refers to a component in an oil and gas well which acts as a failsafe to prevent the uncontrolled release of reservoir fluids in the event of a worst case scenario surface event. It is almost always installed as a vital component on the production tubing string. The valves typically have a "flapper" that closes against upward pressure in the event of an emergency. In normal use, the flapper is retained in an open position due to a sleeve that extends through the bore of the valve and prevents the flapper from closing. The sleeve is held in place with positive hydraulic control pressure from a control line. In the event of a loss in control pressure, the tube retracts and the flapper closes against a seat.

[0003] In the event of a malfunction of a tubing mounted safety valve, replacement would typically mean pulling the production string. Rather than suffer this type loss in time and revenue, the tubing valve is permanently locked in the open position and a replacement valve is run into the well, typically on wireline. The new valve has a smaller diameter than the first one but requires the same source of pressurized fluid to keep it open in normal operations. This means accessing the control line pressure from the existing valve body, typically by penetrating a metallic wall of the body. Current solutions include downhole cutters utilizing batteries and printed circuit boards to power a rotating cutting head and a downhole machining operation run on wireline. Batteries and circuit boards are delicate, and downhole machining requires high and surging torque that can be problematic. Other solutions permit an aperture to be formed through the wall of the valve body with a punching operation but also require that the punching device be rotationally positioned to form the aperture at the right location. There is a need therefore for a better way to cut material downhole. There is a more particular need for an apparatus and method to access a source of control fluid to be utilized by a replacement downhole safety valve.

SUMMARY OF THE INVENTION

[0004] In one aspect, the invention includes a downhole cutting tool having a source of abrasive material; a source of high pressure fluid mixable with the abrasive material; a rotatable nozzle section, the nozzle section rotatable due to a source of low pressure fluid acting on a piston surface formed on a sleeve, the sleeve rotationally and axially movable in a body of the tool; whereby the sources of high and low pressure fluid and the abrasive material are housed in the tool. In another aspect the invention includes a method of operating a tool having the forgoing characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0006] Figure 1 is a section view of a cutting tool according to one aspect of the invention.

[0007] Figure 2 is an enlarged section view of a nozzle section at a lower end of the tool.

[0008] Figure 3 is a section view showing a lower section of the tool and including a low pressure water section. [0009] Figure 4 is a section view showing an upper section of the tool and including a high pressure water section and an abrasive section.

[0010] Figure 5 is a section view showing the tool disposed at a predetermined location in a wellbore.

[0011] Figures 6 and 7 are perspective views of a rotatable sleeve illustrating slots formed in the sleeve and used to rotate a nozzle section of the tool.

[0012] Figures 8A-C are additional perspective views of the rotatable sleeve as shown at various times during the operation of the tool.

[0013] Figure 9 is a section view of the tool in an activated state with valves open to the flow of low and high pressure water.

[0014] Figure 10 is a section view showing the tool with the nozzle section rotated 180 degrees from its position in Figure 2.

[0015] Figure 11 is a section view showing the tool rotated 360 degrees from its position in Figure 2.

[0016] Figure 12 is a section view of the nozzle section of the tool.

[0017] Figures 13 and 14 are section views of the valve housing before and after the cutting operation.

DETAILED DESCRIPTION

[0018] In one embodiment, a downhole tool is run into a wellbore on wireline in order to access a source of hydraulic control fluid to be utilized by a wireline safety valve that will be installed later. The tool cuts through a "web" of metal that separates the source of fluid from an interior of the body of a tubing-run safety valve that has been permanently locked out due to a malfunction. Wireline deployed safety valves and well know in the art and described in one instance in a catalogue viewable on the web site of Weatherford International at [http://www.weatherford.com/ECMWEB/ groups/web/documents/weatherfordcorp/WFT003619.pdf] and that publication is incorporated by reference herein.

[0019] The tool of the present invention includes a rotating nozzle section along with a source of high pressure and low pressure fluid, like water and a source of abrasive material, like Garnett abrasive. In this disclosure, high and low fluids mean that the high pressure fluid is of a higher pressure than the low pressure fluid. The tool is designed to be run into the well and then, at a predetermined time and location, actuated wherein the cutter nozzle rotates as a high pressure stream of water and abrasive is applied to an internal surface of the safety valve body. High pressure water cutters using abrasive material are well known in the art. In this disclosure, the term "cutting" refers to any removal of material made by the tool, including but not limited to apertures, cuts, slots, and grooves.

[0020] Figure 1 is a section view of a cutting tool 10 according to one aspect of the invention. The tool includes a rotatable nozzle section 12 visible at a lower end of the Figure as well as an abrasive section 23, a low pressure water section 22 and a high pressure water section 21. The nozzle is intended to redirect a source of high pressure and high volume water at a 45 degree angle from the center line of the tool. Aspects of the nozzle are more specifically shown in Figure 11. High pressure water enters a high pressure section 16 of the nozzle via line 15 and then continues through an orifice creating a high velocity area 18. Thereafter, an area of expanded volume 20 creates a venturi effect and abrasive material from line 25 is urged into the stream due to the vacuum-like properties of the venturi. As the water/abrasive stream exits the nozzle, its rotational speed and pressure create an aperture 140 in the metal therearound adequate to pierce a relatively thin "web" 115 of material leading to an area 145 of hydraulic control fluid. The tool is typically run into a well on wireline.

[0021] Figure 2 is an enlarged section view of the nozzle section of the lower end of the tool. The tool includes two shiftable pilot valves 60a, 60b that prevent high pressure and low pressure water (in lines 15, 17 respectively) from communicating with other areas of the tool until a predetermined time. In the position shown in Figure 2, the low and high pressurized water is prevented from flowing due to O-rings 130 that block a fluid path through the valves. When the pilot valves are shifted as will be explained herein, the high pressure water travels towards the nozzle section 12 and the low pressure water acts to rotate a sleeve 65. In one aspect, the valves are shifted due to a jarring effect of weight that provides enough force to shear pins 135 thereby permitting an inner section of the tool 10 to move downwards relative to an outer section. As explained herein, the rotatable sleeve 65 moves axially and rotates due to fluid pressure applied by the low pressure water to a piston area 70 formed on an outer surface of the sleeve 65.

[0022] Figure 3 is a section view showing a lower section of the tool 10 and including the low pressure water section 22. In the embodiment shown, a supply of water 40 is provided along with a piston 55 and a source of pressurized gas 45, like nitrogen. The water is communicated to pilot valve 60a via low pressure line 17 and thereafter, when the pilot valve is opened, to piston area 70 of sleeve 65.

[0023] Figure 4 is a section view showing an upper section of the tool and including a high pressure water section 21 and an abrasive section 23. Water is stored in a chamber 30 and is separated from a source of high pressure nitrogen 35 by a piston 50. In addition to the high pressure gas, the pressure of the water is increased due to a relatively large piston area 51 adjacent the nitrogen and a relatively small piston area 52 adjacent the water. The high pressure water communicates with the pilot valve 60b via high pressure water line 15.

[0024] The abrasive section 23 is also shown in the Figure and includes a source of abrasive material in a chamber 24 and a line 25 that extends to the nozzle where it is mixed with the high pressure water during cutting. As stated herein, the abrasive material, typically Garnett is not pressurized but enters the stream of water due to suction-like property created in an expanded area of the nozzle section 12. In one embodiment, a pocket of air is provided behind the abrasive material in the chamber to prevent a vacuum being formed. [0025] Figure 5 is a section view showing the tool disposed at a predetermined location in a housing 120 of a pre-existing safety valve. Visible alongside the safety valve is a control line 121 with hydraulic fluid for keeping the valve flapper in an open position. The tool is run in until a shoulder 105 formed on the tool hits a no-go formation 110 formed on an inner surface of the housing 120. As shown in the Figure, the shiftable portions of the tool are initially pinned together with shear pins 135 and a spring loaded button member 125 retains rotatable sleeve 65 in its initial position. An indicator 95 designed to ensure the tool is seated in the right location in the wellbore is located adjacent a recess 97 formed in an interior of the housing 120. The indicator is constructed and arranged to extend into the recess due to a raised surface 96 moving under it as the tool is shifted (Figure 9) to open the pilot valves 60a, 60b.

[0026] Figures 6 and 7 are perspective views of the rotatable sleeve 65 illustrating slots 75, 80 formed in an outer surface of the sleeve. The tool is constructed and arranged whereby the low pressure water acts on the piston surface 70 of the sleeve 65 and urges the sleeve downwards in the tool body. As the sleeve 65 moves axially toward the nozzle section, it is rotated due to a pin 85 (Figure 5) extending inwardly from an inner wall of the tool housing and acting on angled slot 75 formed in an outer surface of the sleeve. At the same time, the nozzle section rotates due to another pin 90 extending from its inner surface that acts with the other oppositely angled slot 80. Effectively, the upper pin and slot 85, 75 cause the sleeve to rotate as it moves downwards and the lower pin and slot 90, 80 cause the nozzle to rotate. The result is that for every degree of rotation of the sleeve 65, the nozzle section rotates two degrees. The arrangement causes the sleeve to move axially towards the nozzle section 12 as it rotates, while movement of the nozzle section is limited to rotational movement. Comparing Figures 5, 9, and 10, those Figures show the nozzle in its first position (Figure 5), its position at 180 degrees (Figure 9) and it final position having rotated 360 degrees (Figure 10). In each view the lower end of the sleeve 65 is progressively lower in the tool as can be appreciated from its distance from lower pin 90. The Figures also make it clear that upper pin 85 is rotationally fixed while lower pin 90 rotates with the nozzle section.

[0027] Figures 8A-C are additional perspective views of the rotatable sleeve 65 as shown at various times during the operation of the tool and also illustrates the pins 85, 90. For example, prior to operation (Figure 8A) , the sleeve is located at a first axial and rotational position within the body of the tool 10 and both pins 85, 90 are at a lower end of their respective grooves 75, 80. As the tool operate and the nozzle rotates 180 degrees as shown in Figure 8B, the sleeve has assumed a lower axial position in the body and the pins are located about ½ way up their respective grooves. Noticeably, lower pin 90 has rotated with the nozzle section and is located on a left side of the sleeve 65. Finally, when the nozzle has rotated a full 360 degrees as shown in Figure 8C, the pins are located in their original rotational position but each pin 85, 90 is at an upper end of its groove 75, 80.

[0028] Figure 9 is a section view of the tool 10 in an activated state. Due to a downward force applied from the surface, the shear pins 135 have been sheared, permitting an inner portion of the tool that includes the pilot valves 60a, 60b to move down relative to the housings of the valves. In doing so, the valves have been opened and a fluid path established around the O-ring seals 130. In Figure 9, sleeve 65 is shown in its initial position, retained by spring loaded button 125. However, with the pilot valves open, low pressure water is free to communicate directly with piston area 70 of the sleeve 65 (not visible), beginning the axial and rotational movement of the sleeve 65 and with it, the rotation of nozzle section 12.

[0029] Figure 10 is a section view showing the tool 10 with the nozzle 14 adjacent a source of pressurized control fluid and the nozzle section rotated 180 degrees. The sleeve 65 is shown in an axial and rotational position between its initial position and its final position. Indicator 95 has been moved out into recess 97 due to surface 96 having moved beneath it. Rotation of the nozzle 14 is evident by the partial twisting of the abrasive line 25 and the high pressure water line 15. [0030] Figure 11 is a section view showing the tool 10 rotated 360 degrees to a rotational position in essentially identical to the one prior to the operation (see Figure 2). The sleeve 65 is shown in its final position having rotated 180 degrees, and due to the grooves 75, 80 and pins 85, 90, the nozzle section 12 has rotated 360 degrees. Additional twisting of the lines 15, 25 are evident and the onboard sources of high and low pressure water and abrasive material should be depleted.

[0031] Figure 12 is an enlarged section view of the nozzle section 12 of Figure 9 and illustrates an aperture 140 formed in web 115 by the water/abrasive mixture. As shown, fluid communication has been established between the interior of the tool housing 120 and the area of control fluid 145. In addition to the aperture 140, depending upon the speed of the rotating nozzle section 12 and the pressure of the fluid/abrasive mixture, a groove has been formed all the way around the interior of the valve body 120. In the embodiment of the example, the only need is to penetrate the web 115. However, the tool 10 is equally usable to form grooves or penetrating cuts of a variety of depths depending on the downhole needs of an operator. Such functions and results are within the scope of the invention. In one embodiment, the nozzle is constructed and arranged to rotate at least slightly beyond 360 degrees, thus ensuring penetration of the wall of a component, regardless of the location of a source of hydraulic control fluid.

[0032] Figures 13 and 14 are section views of the valve housing before and after the cutting operation. The cutting tool is not shown in Figures 13 and 14 and the purpose of the Figures is to illustrate the eccentric nature of the interior of the valve housing 120. Visible in Figure 13 is the area of control fluid 145, the valve housing 120 and the eccentric shape of its interior. In Figure 14, the cutting operation has taken place and the cut is shown by line 140 which intersects the web of material 115. The Figure illustrates how the cutting does not extend completely around the interior of the valve body. Rather, the cutting starts and stops at about 1 :00 and 5:00 o'clock, respectively. [0033] The tool 10 is typically loaded with water and nitrogen at the surface of the well. In one example, 500 psi nitrogen is loaded into the high pressure section 21 at a surface temperature of 100 degrees Fahrenheit. The lower pressure water section 22 is loaded to a pressure of 100 psi at the same temperature. After run-in to a depth where it will be operated, the downhole temperature might be 300 degrees Fahrenheit, resulting in an effective pressure of 1 ,500 psi and 300 psi respectively. Furthermore, due to the multiplying effect of the pistons areas 51 , 52 in the high pressure section 21 , the actual pressure of the cutting fluid will be about 30,000 psi. In a typical application, the distance between the end of the nozzle 14 and the web portion 115 to be penetrated is about .200" and the web portion itself is about .106". Also, a typical tubing run valve body has an eccentric bore in the area of the web that causes the nozzle 14 to be slightly closer to the wall of the body in the area of the web.

[0034] In practice, the tool 10 is run into the wellbore on wire line and seated against the no-go area 110 formed on an interior of the existing valve body 120. Initially, an interior portion of the tool and an exterior portion are separated and retained in that separated position by shear pins 135. In the initial condition shown in Figure 2, the pilot valves 60a, 60b are closed due to their location relative to O-ring seals 130. However, when the tool is "jarred", in one instance by dropping weighted members located in the wellbore, the pins 135 are sheared and the portion of the tool including the pilot valves moves downwards in relation to the outer portion. This position is shown in Figures 9-11. As soon as the parts move down and the valves open, fluid communication is permitted between the low and high pressure water sources and the nitrogen charges behind each force the water to their respective locations. After the tool has operated to establish contact with hydraulic control fluid, it is removed and a replacement valve is run into the wellbore and seated and sealed in the interior of the existing valve body.

[0035] Various features of the tool 10 facilitate its downhole use. For example, the lines carrying water and abrasive are provided with additional coils of length to permit assembly and rotation of the nozzle section 12. Additionally, a spring loaded button member 125 serves to retain the rotating sleeve 65 in its initial position prior to being urged downwards by the low pressure water. An indicator 95 is useful to ensure the tool is seated in the valve body 120 rather than being inadvertently seated at some location thereabove. In the initial pinned position, the indicator 120 extends partially into a recess 97 formed in the valve body 120. As the pins 135 are sheared and the inner portion moves down, a sloped shoulder 96 moves the indicator out and into the recess 97.

[0036] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.