RU2129654C1 - Device for perforating deep wells - Google Patents

Abstract

FIELD: oil-and-gas producing industry, in particular, devices for perforating wells, mainly, deep wells. SUBSTANCE: device has body with hermetic seals and connected to logging cable. Device body accommodates charges, detonator, detonating cord and is filled with fluid communicating with well fluid through pressure regulator made in the form of system of air hollow and pistons of various diameters. Pistons are provided with seals and engageable with one another. Ratio of pistons cross-section areas provides for tightness and strength of body, charge, detonator and presence in device body of fluid communicating with well fluid through pressure regulator. The latter builds up and automatically maintains inside perforator the rated pressure of such value which ensures safe difference of pressure in well and in perforator. The rated pressure precludes destruction of body and other parts of perforator, detonating cord and is determined by formulas. EFFECT: perforator serviceable in wells of any depth without failures. 1 dwg

Description

 The invention relates to the field of oil and gas industry, namely, to devices for perforating wells, mainly deep.

 A device for perforating wells is known that contains a tape connected to a geophysical cable, charges, a detonator, a detonating cord mounted on a tape (see Grigoryan N.G. Opening of oil and gas strata with perforating guns., M., Nedra, 1982, 263 pp.) .

 The disadvantages of this device is that all its elements are open and are in direct contact with aggressive well fluid. In addition, at great depths, the hydrostatic pressure of a wellbore column can destroy charges, a detonator, and a detonating cord.

 These disadvantages are eliminated in the device adopted as a prototype of the proposed solution. This device contains a housing with hermetic seals connected to the geophysical cable, charges, a detonator, a detonating cord installed in the housing (see Shooting and explosive equipment. Handbook edited by L.Ya. Fridlyander. 2nd edition, M., Nedra, 1990, p. 33-48).

 The disadvantage of this device is that the sealed housing withstands the pressure of the well fluid up to 60-70 MPa. At higher pressures, the casing is destroyed and, therefore, all elements located inside the casing are destroyed, for which the indicated pressure values are almost also limiting. A pressure of 60-70 MPa can occur in wells with a depth of 5-6 km. Thus, perforation in deep wells with this device is not possible to perform.

 The objective of the present invention is to provide a device for perforation, capable of working in any deep and superdeep (up to 10 or more km) wells, withstanding pressure and not collapsing.

где S₁ - площадь в поперечном сечении поршня, контактирующего со скважинной жидкостью;
S₂ - площадь в поперечном сечении поршня, контактирующего с жидкостью в корпусе;
S₃ - минимальная площадь в опасном сечении корпуса, заряда, детонатора или детонирующего шнура;
P₁ - давление жидкости в скважине;
P₂ - минимально допустимое давление жидкости в корпусе, рассчитываемое по формуле (2);
σ_сж.min - минимальное значение напряжения сжатия, выбранное из ряда минимально допустимых напряжений сжатия для корпуса, заряда, детонатора или детонирующего шнура.This object is achieved in that in a device for perforating wells, comprising a housing with hermetic seals connected to a geophysical cable, charges, a detonator, a detonating cord installed in the housing, a fluid is poured into the housing, communicating with the borehole fluid through a pressure regulator made in the form of a system of a cavity with air and pistons of different diameters interacting with each other with seals, the ratio of the areas of which in the cross section is made with the condition of ensuring tight spine and body strength, charge, the detonator and the detonating cord is defined by the formulas
S ₁ / S ₂ = P ₂ / P ₁ ; (1)

where S ₁ is the cross-sectional area of the piston in contact with the well fluid;
S ₂ - the cross-sectional area of the piston in contact with the liquid in the housing;
S ₃ - the minimum area in a dangerous section of the housing, charge, detonator or detonating cord;
P ₁ - fluid pressure in the well;
P ₂ - the minimum allowable fluid pressure in the housing, calculated by the formula (2);
σ _{squeeze min} - the minimum value of the compression stress selected from a number of the minimum allowable compressive stresses for the housing, charge, detonator or detonating cord.

 The presence in the device casing of fluid communicating with the borehole fluid through the pressure regulator creates and automatically maintains inside the punch a design pressure of such a value that provides a safe pressure difference in the borehole and in the punch, which eliminates the destruction of the casing and other parts of the punch.

 The drawing shows a longitudinal section of a device for perforating deep wells.

 The perforator contains a housing 1 with hermetic seals 2 connected to a geophysical cable 3. Charges 4, a detonator 5, a detonating cord 6 are installed in the housing 1. Liquid 7 is poured inside the housing 1. A pressure regulator made in the form of a system of cavities with air 8 and interconnected pistons of different diameters — a piston 9 in contact with the well fluid and a piston 10 in contact with the fluid 7 in the housing 1. Seals 11 are installed on the pistons 9 and 10.

The cross-sectional areas S ₁ and S _{2 of the} pistons 9 and 10, providing a safe pressure P ₂ , are defined as follows. In the reference books, the minimum values of permissible stresses σ _{srmin were found} for case 1, charge 4, detonator 5, detonating cord 6. Then, the minimum values of areas S ₃ in the dangerous section of case 1, charge 4, detonator 5, detonating cord 6 were determined. the density of the borehole fluid, its static pressure P _{1 was} determined at the maximum depth of the perforator. According to formulas (2) and (3), the minimum permissible values of the pressures P ₂ in the housing 1 are determined that do not lead to the destruction of the housing 1, the charge 4, the detonator 5, the detonating cord 6. The minimum permissible pressure P ₂ is the minimum value from the indicated series of pressures . After that, the maximum possible diameter of the piston 10 is structurally determined for reasons that the larger the diameter of the hole, the easier it is to make it. The value of S _{2 is} determined by the circle area formula. The area S _{1 of the} piston 9 is determined by the formula (1). The diameter of the piston 9 is calculated by the circle area formula.

The device operates as follows. When the perforator is lowered into the borehole on the geophysical cable 3 to a predetermined depth, the borehole pressure acts on the piston 9, which transfers the action to the piston 10, and through it to the fluid 7 inside the housing 1. The balance of forces acting on the pistons occurs: P ₁ • S ₁ = P ₂ • S ₂ . Thus, a pressure of such a value is created and automatically maintained that provides a safe pressure difference in the well and in the perforator, which eliminates the destruction of the casing and other parts of the perforator.

Claims (1)

A device for perforating deep wells, comprising a housing with hermetic seals connected to a geophysical cable, charges, a detonator, a detonating cord installed in the housing, characterized in that the fluid that communicates with the well fluid through the pressure regulator is made inside the housing, made in the form of a system of cavities with air and pistons of different diameters interacting with each other with seals, the ratio of the areas of which in cross section is made with the condition of ensuring tightness and durability STI housing charge, detonator, detonating cord and is determined by the formulas
S ₁ / S ₂ = P ₂ / P ₁ ; (1)

where S ₁ is the cross-sectional area of the piston in contact with the well fluid;
S ₂ - the cross-sectional area of the piston in contact with the liquid in the housing;
S ₃ - the minimum area in a dangerous section of the housing, charge, detonator or detonating cord;
P ₁ - fluid pressure in the well;
P ₂ - the minimum allowable fluid pressure in the housing, calculated by the formula (2);
σ _{squeeze min} - the minimum value of the compression stress selected from a number of the minimum allowable compression stresses for the housing, charge, detonator or detonating cord.