The Chinese utility model patent No. 97242235.8 under the title of “a high-energy combined overbalance high density double jet perforating device for oil-gas wells” employs a cylindrical powder sleeve or a solid-propellant sleeve, any of which has several charge sockets distributed in its different lengths and different phases and has a detonating cord hole used for inserting a detonating cord while a charge is mounted in the corresponding charge socket. The structure of the powder sleeve or the solid-propellant sleeve is difficult to realize through a certain manufacturing process, moreover before the down hole operation in the oil field it is required to cut the composite solid-propellant sleeve, which decreases the efficiency of assembling and increases the potential failure in safety.
In the above-mentioned patent, the pressure-relief vent is sealed with a circular steel plate which is covered by a sealing cap made of rubber layer and is inserted in the pressure-relief vent thus to achieve the sealing. Since the rubber layer of said sealing cap is only combined with the upper surface of the circular steel plate, under the action of pressure, temperature and chemical medium, said rubber layer is fallen off easily and loses its sealing function, then water may flow into the perforating gun, which may extinguish the detonating cord even a failure of gun explosion will happen.
Moreover, in the above-mentioned patent, the positioning mechanism between the charge strip and the perforating gun can only position the charge strip in the perforating gun radically and can not position the charge strip in the perforating gun axially which is not only detrimental to detonation propagation but also causes the shaped charges unable to align with the pressure-relief vent thus the jets produced through the detonation of the shaped charge may be deflected and is harmful to the quality of perforation as well as to the effect of the gas fracturing.
In addition, the inner surface of the gun bottom at the lowermost end of the perforating device is a planar surface and the space of the lowermost end of the perforating device is very small, in which after the explosion of the shaped charges and deflagration of the powder sleeve or the solid-propellant sleeve, a local pressure may build up enormously, resulting in an accident of gun explosion.
From above, the device according to the said patent is difficult to realize by means of a certain manufacturing process because of using the powder sleeve or the solid-propellant sleeve. In the meantime the down hole operation is hardly to meet a variety of underground conditions and it is impossible to achieve efficiently the effect of perforation and fracturing.
The invention is aimed at providing a high energy combined new perforating device for oil-gas wells. The device can efficiently increase the fracturing energy and can be manufactured through a simple process so as to be suitable for commercial production.
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