RU2247924C1 - Blasting cartridge for shooting-blasting operations - Google Patents

Abstract

FIELD: initiation means, applicable for initiation of the detonating wire in a sealed shooting-blasting equipment mainly used in geological exploration and mining of oil and gas fields.

SUBSTANCE: the blasting cartridge has a case (cartridge case without any bottom), positioned in which are an electric primer assembly, booster lead and a small-sized primer detonator consisting of an envelope containing the initiating charge of brisant explosive and the main charge of brisant explosive. There is a gap between the small-sized primer detonator and the booster lead. One or several openings are made in the case wall communicating the gap with the environment. The envelope bottom is made of metal or alloy, having a high value of acoustic stiffness (the product of density by sound velocity), for example, copper, steel. The thickness of the envelope makes up 0.15 to 0.25 mm. The relation between the envelope bottom densities and the brisant charge is within 0.3 to 0.6. The envelope may be made in the form of a cap with a pierced bottom, a component forming the bottom: plate, cup, second cap may inserted in it.

EFFECT: enhanced adaptability to manufacture of the cartridge and reduced danger of its manufacture.

2 cl, 1 dwg, 1 tbl

Description

The invention relates to means of initiation and is intended to initiate a detonating cord in a sealed perforating explosive equipment, used primarily in the exploration and development of oil and gas fields.

One of the problems of perforating and blasting operations using sealed perforated explosive devices of reusable use is the prevention of accidents arising from a violation of their tightness. The operation of the detonating cord in the apparatus filled with the borehole fluid leads to deformation of the body and jamming it in the casing. Therefore, explosive cartridges used in sealed perforating explosive equipment, along with their usual functions, as a rule, have a safety action, which consists in the fact that when immersed in liquid, the explosive cartridge cannot initiate a detonating cord attached to it.

Known explosive cartridge PVPD-N [1], electric detonator [2], the protective effect of which is ensured by blocking the force of the flame of the electric igniter by the borehole fluid. The PVPD-N cartridge consists of a thin-walled metal shell (sleeve without bottom) in which an electric igniter and a transfer charge are placed, between which there is a gap. A hole is made in the wall of the sleeve of the PVPD-N explosive cartridge in the region of the gap between the electric igniter and the secondary charge, which communicates the gap with the environment.

The transfer charge is a cap with pressurized charges of a blasting explosive (BVV), initiating (IVV) and incendiary pyrotechnic composition pressed into it. The open end of the cap and, accordingly, the incendiary composition are turned toward the electric igniter, the bottom of the cap and, accordingly, the charge of the explosive charge, toward the detonating cord connected to the sleeve.

The electric igniter includes a block part with an incandescent bridge and an igniter composition, fixed in a metal cap. The metal cap protects the igniter applied to the incandescent bridge from moisture. At the bottom of the cap, a figured punching in the form of an asterisk is made, drowning local sections of the bottom.

Cartridge PVPD-N works as follows. When a high-frequency electrical signal is applied, an electric igniter is activated. The force of gaseous products destroys the bottom of the cap of the electric igniter, weakened by a figured stamping, passes the air gap and sets fire to the incendiary pyrotechnic composition in the transfer charge. From the heat pulse, the explosive charge is triggered, initiating the charge of the explosive detonator, which in turn initiates a detonating cord connected to the cartridge.

During depressurization of a perforating-explosive device, the gap between the electric igniter and the transfer charge through the hole in the liner wall is filled with borehole fluid, which prevents the force of the gaseous products of the operation of the electric igniter assembly to the transfer charge.

The disadvantage of the cartridge PVPD-N is the lack of reliability, which is associated with the following factors.

In mass production, it is difficult to ensure the exact dimensions of the figured punching of the bottom of the cap of the electric igniter. If the punching depth is insufficient, which occurs, for example, when the stamping tool is worn, failures may occur due to the fact that the bottom of the cap does not open properly under the influence of the ignition composition trigger products. During through penetration of the bottom of the cap, which can also be obtained in the process of figured stamping, the igniter composition can be damaged under the influence of high temperature and humidity during the descent of the perforating explosive device into the well, which lasts several hours.

The transfer charge in the PVPD-N cartridge is open. The incendiary pyrotechnic composition contained in it is quite resistant to moisture. Nevertheless, violations of storage conditions (for example, storage in an unpressurized package in a humid environment) and the subsequent exposure to high temperature and humidity during the descent of a perforated explosive device can lead to a decrease in its sensitivity and to failure.

It should be noted such a drawback of PVPD-N and similar cartridges as the high dependence of the reliability of operation on the mass of the igniter composition in the electric igniter. With a large mass of igniter composition, the risk of failures in the protective effect increases, since a powerful flow of response products can eject the well fluid from the gap between the electric igniter and the transfer charge and ignite the incendiary charge in the transfer charge. In case of insufficient mass of the ignition composition, failures in ignition of the incendiary charge can occur.

A small mass spread of the igniter composition can be achieved by pressing its sample directly onto the incandescent bridge. To avoid breaks, the glow bridge should rest on the surface of the shoe part of the electric igniter. However, in this design, there is a large outflow of heat generated on the bridge when applying electric current to the block part. When limiting the magnitude of the electric current flowing along the incandescent bridge, which occurs, for example, in an electric igniter with transformer coupling of power circuits and an incandescent bridge (namely, such an electric igniter is used in the PVPD-N pagron), thermal energy may not be enough for reliable ignition of the igniter composition. Then, to reduce heat loss, the glow bridge is soldered to wires protruding from the shoe part a few millimeters. The application of the ignition composition is done by dipping the incandescent bridge in a suspension of the ignition composition in a volatile solvent. With this technology, for a number of reasons, ignition heads are of different sizes. The control, carried out by visual comparison of the igniter heads with the control samples, is subjective and does not guarantee complete rejection of unsuitable samples.

The disadvantages inherent in the design of the PVPD-N cartridge are deprived of explosive cartridges, the safety action of which is ensured by breaking the detonation chain. Examples of this design are the initiating device [3] and the explosive cartridge PVPD-M [4], selected as a prototype of the present invention.

The PVPD-M cartridge consists of a sleeve without a bottom, in which a small-sized electric detonator is placed, and a transfer charge. There is an air gap between the small-sized electric detonator and the transfer charge. A hole is made in the wall of the sleeve of the PVPD-M explosive cartridge in the region of this gap, which communicates the gap with the environment.

The transfer charge is a cap into which the explosive charge and explosive charge charges are closed, covered by a cup. The cup and the explosive charge are turned towards a small-sized electric detonator. The bottom of the cap and the charge of the detonator are facing towards the detonating cord connected to the cartridge.

The small-sized electric detonator is a block with output wires and an incandescent bridge, on which the explosive and explosive charge charged by an aluminum cap are pressed.

Cartridge PVPD-M works as follows. When an electrical signal is applied, a small-sized electric detonator is triggered. During detonation of the charge of the explosive charge, the bottom of the aluminum cap is thrown in the direction of the transfer charge. Upon impact of the bottom of the cap with the transfer charge, a shock wave arises, which initiates the charge of the explosive transfer charge. Then, shock-wave initiation of the charge of explosive charge and the detonating cord connected to the cartridge occurs.

During depressurization of a perforating-explosive device, the gap between the small-sized electric detonator and the transfer charge through the hole in the liner wall is filled with borehole fluid. The speed of throwing the bottom in a condensed medium drops sharply. Shrapnel initiation becomes impossible. Shock-wave initiation does not occur due to the attenuation of the shock wave during its movement in the gap from the charge of the explosive charge to the transfer charge.

The speed of throwing the bottom of the shell of a small-sized electric detonator of the PVPD-M explosive cartridge is determined by the mass of the charge of the explosive charge, which can be equipped with high accuracy. Punching the bottom of the shell is not required. The transfer charge is closed by a cup. All this allows you to increase the reliability of the explosive cartridge PVPD-M. However, it is less technologically advanced, and its production is more dangerous.

To ensure safety, the gap between the small-sized electric detonator and the transfer charge in the PVPD-M cartridge is 30 mm (in PVPD-N the gap is 11 mm), which requires the use of significant lengths of non-technological sleeves in the design.

In the manufacture of the PVPD-M cartridge, there are 2 especially dangerous operations for pressing explosive charges (in the manufacture of a transfer charge and in the manufacture of a small-sized electric detonator).

The purpose of the present invention is to improve manufacturability by reducing the length of the gap and, accordingly, the length of the cartridge case of the explosive cartridge and reducing the risk of production associated with the equipment of the transfer charge.

The goal is achieved by using as the material of the bottom of the shell a charge of explosive charge in a small metal or alloy electric detonator with a high value of acoustic rigidity (product of density by the speed of sound), for example, copper, brass, making the thickness of the bottom of the shell in the range 0.15-0.25 mm and the ratio of the linear density of the bottom of the shell (the product of the density of the material of the bottom to its thickness) to the linear density of the propellant charge marking it (the product of the charge density and its height) ranging from 0.3 to 0.6. The transfer charge in this case contains only heat-resistant BVV, for example, RDX, HMX.

The proposed explosive cartridge is shown in the drawing. It consists of a housing (sleeve without bottom) 1, in which an electric igniter assembly 2, a transfer charge 3, and a small detonator capsule, which is a shell 4 containing the initiating charge of the explosive charge, or explosive charge and the main charge of the explosive charge 5, are placed 5. Between the small detonator capsule and the transfer charge 3 has a gap 6. In the wall of the housing 1 in the region of the gap 6 there is a hole 7 communicating the gap 6 with the environment.

The transfer charge 3 is a cap 8, in which the charge of the explosive charge is closed, closed by the cup 9. The cup 9 protects the charge of the explosive charge from moisture.

The shell 4 is a metal cap or, as shown in FIG. 1, is a combined structure consisting of a cap with a punched bottom 10 into which a second cap 11 is inserted. The element forming the bottom of the shell 4 along with the second cap 11 may be a plate or cup . The combined design provides the ability to make the walls and bottom of the shell 4 from different materials, as well as to make the bottom of the shell 4 with a thickness less than its walls. The bottom of the shell 4 is made of metal or alloy having a high value of acoustic rigidity. The thickness of the bottom of the shell 4 is 0.15-0.25 mm. The ratio of the linear densities of the bottom of the shell 4 and the charge of the explosive charge 5 is in the range from 0.3 to 0.6.

Explosive cartridge works as follows. When an electrical signal is applied, a small-sized electric detonator is triggered. The bottom of the shell 4 during detonation of the charge of the explosive charge 5 is thrown in the direction of the transfer charge 3. The impact leads to the initiation of detonation of the transfer charge 3. The latter initiates a detonating cord attached to the cartridge.

The protection mechanism is the same as the prototype protection mechanism. When depressurization of a random explosive device, the gap 6 through the hole 7 is filled with well fluid. The fragmentation initiation of the transfer charge 3 becomes impossible due to the low throwing speed of the bottom of the shell 4 in a condensed medium. The shock-wave initiation of the transfer charge 3 does not occur due to the attenuation of the shock wave from the charge of the explosive charge 5 in the process of its movement through the gap 6.

The use as a material of the bottom of the shell 4 of a metal or alloy with a high value of acoustic stiffness with a bottom thickness in the range of 0.15-0.25 mm and a ratio of the linear densities of the bottom of the shell 4 and the marking charge BVV 5 ranging from 0.3 to 0, 6 allows to provide critical conditions for the fragmentation initiation of the transfer charge 3 with a minimum charge mass of the explosive charge 5. The result of minimizing the charge mass of the explosive charge 5 is to reduce the initial intensity of the shock wave created by it. Therefore, the length of the gap 6, in which the shock wave is weakened to a level that excludes the possibility of initiating the transfer charge 3, is significantly reduced and can be 6-10 mm

The selection of the parameters of the claimed design of the explosive cartridge was made on the basis of the results of the experiments shown in the table, taking into account the reserves for the reliability of initiation and safety action and necessary for the production of technological tolerances. In the experiments, for each design variant, the value of the gap length was determined at which an explosive cartridge immersed in water does not initiate a detonating cord. Further, with this value of the length of the gap, the failure-free operation of the explosive cartridge in air was evaluated (the “-” sign indicates the presence of failures, the “+” sign indicates their absence).

The physical explanation of the results of the table is as follows:

When a metal or alloy bottom with a high value of acoustic rigidity (copper, iron) and a bottom thickness of 0.1 mm is used as a material, high impact pressures are achieved, however, failure-free initiation of the transfer charge does not occur due to the short duration of this pressure, which is determined bottom thickness. As the bottom thickness increases, the collision pressure decreases, since a heavier bottom accelerates to lower speeds. But this also increases the duration of the pressure, which leads to the achievement of critical conditions for the initiation of the transfer charge. With a further increase in the bottom thickness, its throwing speed becomes insufficient to create the collision pressure values required to initiate the transfer charge.

For sufficiently large ratios of linear densities of the bottom and bottom-throwing charge of the explosive charge, a high rate of throwing of the bottom and, accordingly, a high collision pressure are not provided. At sufficiently small values of this ratio and, accordingly, a sufficiently large mass of the charge of the explosive charge, the gap length required for the protective action increases. And with a large gap length, there are failures in initiating the transfer charge associated with the dispersion of fragments, the inhibition of peripheral fragments when they touch the walls of the body, and significant differences in the frequency of impact of the fragments with the surface of the transfer charge. Unlike failures associated with insufficient pressure or impact time, such failures do not have a clear relationship with the energy characteristics of the fragments.

When aluminum bottom is used as a material, high speeds of throwing fragments are achieved, however, due to the low value of acoustic rigidity, the impact pressure of the fragments with the transfer charge is insufficient to initiate the latter.

List of references

1. A set of design documentation for the explosive cartridge PVPD-N DISHV.773955.501. Inv. No. 14687, 15715. FSUE NPP Krasnoznamenets, 1992

2. US patent No. 2759417. 1956

3. US patent No. 2891477. 1955

4. A set of design documentation for the explosive cartridge PVPD-M TU 41-12-047-89. Inv. in No. 4,166.4241. FSUE NPP Krasnoznamenets. 1989 year

Claims (2)

1. An explosive cartridge for perforating and blasting operations, containing an electric igniter assembly, a transfer charge and a detonator capsule, including a blasting explosive substance (BVV) charge in a shell in the form of a cap placed in a case - a sleeve without a bottom, in the wall of which there is a gap between one or more holes are made by the shell and the transfer charge, characterized in that the bottom of the shell is made of metal or an alloy having a high value of acoustic rigidity, for example, copper, steel, the thickness of the shell bottom It wishes to set up of 0.15-0.25 mm, and the ratio of the linear density of the bottom shell to the linear density BVV charge ranges from 0.3 to 0.6. 2. Explosive cartridge according to claim 1, characterized in that the shell is made in the form of a cap with a punched bottom, into which an element forming the bottom is inserted: a plate, a cup, and a second cap.