RU2093660C1 - Pipe cutter - Google Patents

Abstract

FIELD: oil and gas production industry. SUBSTANCE: device is intended for cutting pipes inside oil, gas and other wells. For effective cutting of drill pipes with thick walls with simultaneous reduction of their radial deformation and less mass of explosive charge, explosive charge is located between upper and lower metal plugs with no clearance. Axial hole in charge is blind to half of charge height. Initiating system is installed with its lower end face on bottom of blind hole in charge. Relation of thickness of each metal plug Δ to diameter of charge d_ch is within interval of

. Relation of charge height h_ch to diameter of charge d_ch is within interval of

Description

 The invention relates to the field of ultra-high-speed pulse impact and is intended for transverse cutting of cylindrical pipes in oil, gas, exploration and other wells.

 The proposed device solves the problem of cutting thick-walled pipes by increasing the efficiency of the explosive charge. At the same time, the pipe sections adjacent to the fracture site practically do not undergo radial deformation of the walls, which allows them to be freely removed from the well.

 A device for cutting pipes containing a disk cumulative charge with an initiation system (SI) located on the axis of the device. This device, having a cumulative recess with a lining, forms an annular metal stream that burns the pipe walls to a depth of not more than 10-15 mm [1] The disadvantage of this device is the relatively low ability to cut thick-walled pipes with a small inner diameter due to the limited size of the cumulative charge.

 A device for cutting pipes, consisting of a cylindrical body located in it with an explosive charge (BB) and an initiation system (SI). SI in the form of an explosive cartridge is located on the upper base of the charge. The device is designed to cut stuck drill pipes in wells in emergency situations [1, 2] When an explosive cartridge detonates, detonation is excited on the upper base of the charge, so that the detonation wave propagates along the axis of the charge from the upper base to the lower. As a result, under the influence of explosion products (PV), the walls of the pipe are destroyed. The disadvantage of this device is the relatively low destructive effect due to unloading of the PV with a rather large mass of explosive charge.

 As a prototype of the claimed object, a device is taken comprising a cylindrical body, an explosive charge placed in the housing with an axial hole, an upper metal plug with an opening coaxial with the charge hole, a lower metal plug and initiating means located in the explosive charge hole [3] This device also does not provide cutting thick-walled pipes with a relatively high mass of explosive charge.

 The technical result consists in increasing the efficiency of cutting drill pipes with thicker walls while reducing their radial deformation by reducing the mass of the explosive charge.

 This is achieved by the fact that in comparison with the prototype containing a cylindrical body, an explosive charge placed in the housing with an axial hole, an upper metal plug with an opening coaxial with the charge hole, a lower metal plug and initiating means placed in the explosive charge hole is new that the case is equipped with two metal plugs adjacent to the bases of the explosive charge, an axial hole is made in the upper tube and explosive charge, and the hole in the explosive charge is blind and is half its height, and the initiation system is located at the bottom of the charge hole.

а отношение толщины Δ каждой из пробок к диаметру заряда находится в интервале

.In addition, the ratio of the charge height h _zar to its diameter d _zar lies in the range

and the ratio of the thickness Δ of each of the plugs to the diameter of the charge is in the range

.

The presence of massive metal plugs adjacent to the base of the charge, restraining the expansion of the PV, increases the destructive effect of the charge. Metal plugs provide the formation of shock waves reflected from the plugs, during repeated collision of which a structure of destructive stresses arises in the walls of the drill pipe, leading to effective pipe rupture. In the case of tubes of small thickness Δ <0,7d they _charge quickly gaining speed and flying away in opposite directions to expand the volume PV, which leads to a drop in pressure within the explosion products tube and accordingly to reduce the destructive action of the charge. With a tube thickness of D> 1.2d _zar , a noticeable increase in the fracture effect is not observed.

An important role in cutting the walls of the pipe is played by the height of the charge. At a charge height h _zar <1.5d _zar , the absence or incomplete destruction of the pipe walls is observed; at h _zar > 2d the _zar pipe undergoes complete destruction, but the explosive mass increases and the radial deformation of the pipe walls increases accordingly.

 In FIG. 1 shows the inventive device; in FIG. 2 shows the inventive device with means for initiating off-charge.

а отношение Δ толщины каждой из пробок к диаметру заряда находится в пределах

.The pipe cutter (Fig. 1) contains a cylindrical body 1 with a charge 2 located in it and an initiation system 3. Two metal plugs 4 and 5 are installed in the housing 1, adjacent to the bases of the charge 2. An axial hole 6 is made in the upper plug 4 and the explosive charge. The depth of the blind hole 6 in the explosive charge 2 is half its height. The initiation system 3 is installed in the hole 6 and is adjacent to the bottom of the blind hole of the charge 2. For clarity, the pipe 7 to be destroyed is schematically shown. The ratio of the charge height h _zar to its diameter d _zar lies in the range

and the ratio Δ of the thickness of each of the plugs to the diameter of the charge is within

.

 In FIG. 2 shows a specific device of the explosive charge initiation system. It consists of initiating means (electric detonator) 8 located on the outer end of the upper tube 4 and the detonation transmission channel in the form of an explosive rod (10) placed in a tube 9 of non-explosive material. The tube 9 with the BB 10 rod is installed in the axial hole 6 and is adjacent on one side to the initiating means 8, and on the other to the bottom of the dead hole of the charge 2. The wall thickness of the tube 9 from the non-explosive material is selected so that the possibility of premature detonation excitation is excluded or destruction of the explosive charge by the shock wave from the explosive rod over a period of time until the charge undermines in the center.

 The device operates as follows. As can be seen from FIG. 1, when SI 3 is detonated, detonation is excited in this part of the hole 6 of charge 2. A spherical diverging detonation wave arising in the center of charge 2 propagates along the charge and reaches its bases at the same time. The shock waves reflected from the plugs 4, 5 are directed towards each other. When multiple collisions of shock waves in the walls of the destroyed pipe 7 there is a structure of stresses, which in magnitude exceed the strength of the material of the pipe walls, which leads to its transverse rupture.

 The operation of the pipe cutter in FIG. 2 differs from the operation of the pipe cutter in FIG. 1 only by the fact that the excitation of detonation of the charge is carried out through a bar of explosives of small cross-section, installed in a tube of non-explosive material.

 As an example of a specific embodiment, the design of a pipe cutter was chosen, the view of which is schematically depicted in FIG. 2.

The main parameters and dimensions of the structure:
explosive charge: diameter 40 mm, height 60 mm, explosive mass 130 g;
metal plugs: diameter 40 mm, thickness 35 mm;
case: outer diameter 50 mm; wall thickness 5 mm;
tube with explosives: bar diameter 1.8 mm; tube diameter -5 mm;
destructible pipe: outer diameter 130 mm: wall thickness 35 mm, material steel grade 40XH2MA.

 As experiments showed, the pipe cutter reliably cuts a pipe made of steel grade 40XH2MA with an outer diameter of 130 mm and a wall thickness of 35 mm. As a result of research, it was found that at a given charge diameter, the destructive ability of the pipe cutter depends on the strength properties of the material of the pipe being destroyed. For this reason, the pipe cutter was tested on pipes made of steel grade 40XH2MA, the most common and used in the oil and gas industry. Upon rupture, the outer surface of the undamaged part of the pipe underwent slight radial deformation, so that this part of the pipe can be freely removed from the well.

Claims (1)

1. A pipe cutter comprising a cylindrical body with upper and lower metal plugs, inside of which an explosive charge with an axial hole is placed, and an initiation system installed in the axial hole, characterized in that the explosive charge is placed between the upper and lower metal plugs without a gap, the axial hole of the charge is blind at half the height of the charge, and the lower end initiation system is installed at the bottom of the blind hole of the charge, and the ratio of the thickness of each metal plugs Δ to the diameter of the charge d _{z a p} is in the range

2. The pipe cutter according to claim 1, characterized in that the ratio of the charge height h _{z a p} to its diameter d _{z a p} is in the range
1.5 ≅ h _{z a p} / d _{z a p} ≅ 2.

Images