RU2060380C1 - Method for delancy shooting well and torpedo for implementing the same - Google Patents

Abstract

FIELD: well explosion. SUBSTANCE: divided charges are placed in an interval of productive stratum. Then they are set off with delay as to each other. Delay time between blasts of adjacent charges is determined by particular formula. Device has casing with a charge inside and blast initiator connected to a small tip. Torpedo has support members and detonating cord clips. Charge is divided between support members and interconnected with detonating cord. Length of support members is minimum. EFFECT: effective explosion. 8 cl, 3 dwg, 1 tbl

Description

 The invention relates to the field of blasting in wells and can be used mainly to excite oil, water and gas wells, as well as to intensify the initial stage of erosion during the construction of underground storage in salt deposits by leaching.

 A known method of torpedoing a well by exploding a high-explosive torpedo located in the zone of a productive formation [1] The disadvantages of this method are the insignificant efficiency of blasting operations, firstly, due to the lack of dilatancy decompression zone when a single explosive charge explodes, and secondly, the technological capabilities of the method are limited due to the limitation of the mass of the torpedo in terms of well safety

Closest to the claimed method is a method of stimulating oil production, which includes opening a productive formation by a well, placing in the well opposite multiple layers of explosive charges with reduced detonation properties, blasting them first and subsequent blasting of dispersed charges in ultrashort-slow mode at intervals of productive formations [2]
The disadvantage of this method is its multi-stage and the complexity associated with several trips charges. In addition, the known method is characterized by low blasting efficiency, since according to experimental data, the effectiveness of dilatancy torpedoing depends more on the slowdown time between explosions of adjacent charges than on the presence of free surfaces in the array, as well as on the distance to the roof and the bottom of the formation. From the description of the invention does not clear what technical means the implementation of the method is possible. A disadvantage of the design of the well-known downhole torpedo [1] is the low efficiency of explosive treatment of the reservoir due to the limited size of the zone of decompaction of the rock.

 The aim of the invention is to increase the efficiency of blasting due to dilatancy decompression of rocks.

The goal is achieved by the fact that in the method of dilatancy torpedoing of wells, including placing a system of dispersed explosive charges in a well in the interval of a productive formation and blasting them with a slowdown in relation to each other, the slowdown time between explosions of adjacent explosive charges is determined by the formula
Δ tt _n + (0.3.0.5) t _t , (1) where t _{n is the} time of pressure rise in the front of the blast wave, s;
t _n a _n Q ^1/3 + b _n r;
t _t time of action of a blast wave, s;
t _n a _t Q ^1/3 + b _n r _i ;
a _n 2.31 · 10 ³ (ρV _p ) ^-1.21 ;
and _t 5.01 · 10 ⁴ (ρV _p ) ^-1.3 ;
b _n 7.59 · 10 ¹² (ρ V _p ) ^-2.36 ;
b _t 1.66 · 10 ⁹ (V _p ) ^-1.86 ;
Q is the mass of explosive charges, kg;
ρ is the density of the rock in the reservoir, kg / m ³ ;
V _{p is the} speed of sound in the reservoir, m / s, while the mass of explosive charges is determined for the conditions of volumetric compression of the rock and its maximum dilatancy decompression.

The goal is also achieved by the fact that the torpedo is equipped with supporting elements and segments of the LH, and the explosive charge is dispersed between the supporting elements and connected by segments of the detonating cord, wound in a spiral on the supporting elements, while the length of the detonating cord is determined by the formula
l _dsh D / [t _n + (0.3.0.5) t _t ] (2) where D is the detonation velocity of the detonating cord, m / s;
t _{n is the} time of pressure rise in the front of the blast wave, s.

t _n a _n Q ^1/3 + b _n r; t _t a _t Q ^1/3 + b _t r _i ;
a _n 2.31 · 10 ³ (ρV _p ) ^-1.31 ;
and _t 5.01 · 10 ⁴ (ρV _p ) ^-1.3 ;
b _n 7.59 · 10 ¹² (ρV _p ) ^-2.36 ;
b _t 1.66 · 10 ⁹ (ρV _p ) ^-1.86 ; Q is the mass of explosive explosive charges; ρ, V _{p the} density and speed of sound in the rock, and the length of the supporting elements is made minimal so that detonation of the LH in the moderator is transmitted along the LH without transferring it from turn to turn. In addition, the ends of the DS are fixed at the ends with elastic gaskets, elastic inert gaskets are installed at the ends of the support elements, and grooves are made on the support element for laying the DS in them.

 The goal is also achieved by the fact that the torpedo is equipped with an intermediate fighter combined at the contact between the detonating cord and the explosive charge; the first explosive charge is made with the initiator in the form of an explosive cartridge, and the rest in the form of puncture action units and the possibility of triggering from a hydroshock wave of an adjacent explosion. In addition, the initiator of the explosion is installed at the lower end of the supporting elements in the lower part of the device.

 The method of dilatancy torpedoing of wells is implemented as follows.

Before the production of design and explosive shooting operations, a diagram of the volumetric compression of the rock of the formation is determined, for example, in the following way. Samples are made of core material and subjected to testing in a high-pressure chamber under rock and pore pressure conditions corresponding to the depth of the formation, as well as simulating explosive loading on an experimental bench. According to the test results, volumetric strain diagrams of the rock are determined, and the load (σ ₁ axial and σ ₃ - lateral stress and unevenness coefficient ξ = σ ₃ / σ ₁ , at which residual volumetric (dilatancy) deformation of the rock appears. Knowing the laws of shock wave attenuation , thereby determining the necessary masses of charges that provide dilatancy decompression of the formation rock.

After that, using the data on the propagation of waves of radial σ _r (t) and tangential stresses σ _θ (t) during explosions of charges of chemical explosives or nuclear charges in a given rock, determine the time of deceleration of the explosion of neighboring charges, which ensures maximum dilatancy decompression of rocks over outside the area of macrocracks. The deceleration interval Δ t is selected from the condition that the compression phase in the stress wave σ _r (t) from the second charge coincides with the compression phase in the stress wave σ _θ (t) from the first charge. Under such conditions of wave superposition, the maximum non-uniformity of the volumetric stress state of the rocks in the massif is realized and the maximum in size zone of dilatancy decompression occurs. The deceleration time is found by the formula
Δ tt _n + (0.3.0.5) t _t , (1) where t _{n is the} time of pressure rise in the front of the blast wave, s;
t _n a _n Q ^1/3 + b _n r;
t _t time of action of a blast wave, s;
t _t a _t Q ^1/3 + b _t r;
a _n 2.31 · 10 ³ (ρV $\genfrac{}{}{0ex}{}{\text{) -1.21}}{\text{p}}$ ;
a _t 5.01 · 10 ⁴ (ρV _p ) ^-1.3 ;
b _n 7.59 · 10 ¹² (ρV _p ) ^-2.36 ;
b _t 1.66 · 10 ⁹ (V _p ) ^-1.86 ;
Q is the mass of explosive charges, kg;
ρ is the density of the rock in the reservoir, kg / m ³ ;
V _{p the} speed of sound in the reservoir, m / s

To do this, determine in laboratory or field geophysical tests the density ρ and the velocity of longitudinal compression waves in the rock V _r . In the absence of core material in the case of a shallow (up to 1000 m) well, data on the properties of the rock as a whole in the reservoir are used.

 In FIG. 1-4 shows a device for implementing the method.

 The deceleration interval Δt, determined using the experimental laws of wave propagation, calculated by the formula (1), is technically carried out in various ways. For example, in the system of dispersed charges 3 placed in the well, support elements 6 are inserted onto which segments of the DS 7 are wound, the length of which is determined by the formula (2) (Fig. 1). The height of the supporting elements 6 is taken to be minimal, but provided that the detonation of the LH will be carried out along it, and not from turn to turn. The diameter of the support elements 6 is also selected from these considerations, i.e. the most admissible sizes. To reduce the distance between adjacent turns DS 7 in the moderator when processing low-power formations, it is placed in an inert material absorber. The most suitable for these purposes is fine sand, which fill the gaps between the charges 3.

According to another method, an electric detonator is installed in one of the torpedo sections, and detonators of puncture action, which are used, for example, in cumulative perforators, lowered into the well on tubing, are installed in the remaining sections. The detonation of an adjacent charge is excited by exposing the detonator to a detonator with a shock wave, while the deceleration time Δt is ensured by selecting the properties of the well fluid and the distance between charges l: Δ tl / D _у . The velocity of the shock wave in the borehole fluid D _y is determined empirically, or reference data is used. Finally, it is possible to carry out the blasting of the system of charges with a slowdown Δ t by installing an individual explosive cartridge in each explosive charge, and initiating signals to be supplied with the required interval Δ t to each initiator using an electronic device.

 Before torpedoing closed boreholes and open boreholes in the case of low-strength rocks, perforation of the well is carried out in the interval of the reservoir. If shooting works were carried out earlier, then perforation is not performed.

 After performing the above operations, the charge system 3 is lowered on the cable 13 into the zone of the reservoir 14 and explode, initiating the explosion of one of the explosive charges.

Experimental explosions conducted in water, oil, and special geotechnological wells showed that it is the observance of the described conditions that the closest possible closest charges and ultrashort deceleration, determined from the condition of wave superposition by formula (1), gives the maximum dilatation softening effect of the rocks (the appearance of additional microcracking and microporosity) outside the zone of radial cracks (r _Tr ).

 The table shows the data on the increase in oil and water well production rates and on the increase in the injectivity of absorbing wells obtained at oil and gas producing, agricultural and geological enterprises in Russia, Ukraine and other republics.

The following notation is used in the table: Δ t _i / Δt the ratio of the deceleration time between explosions of charges to the time determined by the formula (1); Q ₊ / Q _{+ o the} ratio of the flow rates of oil and water wells after and before treatment; Q _- / Q _-o injectivity ratio of water injection and absorption wells after and before treatment.

The range of values 0.3-0.5 in the formula (1) is selected taking into account the fact that t _{t the} time of action of the blast wave is much greater than the value t _n (t ₊ >> t _n ) of the time of increase of pressure at the front of the blast wave and taking into account the experimental torpedoing results of various wells.

 To implement the method of dilatancy torpedoing of boreholes, borehole torpedoes of various designs can be used, two of which are shown in FIGS. 2 and 3. The common elements of both torpedoes are cable lug 1, housing 2 with explosive charges 3 and blast initiators 12, elastic gasket 4, rod or tubular support elements 6, the detonating cord 7 and the retainer LH on the support elements 8, the electric wire 15. The torpedo body is solid (figure 2) or non-continuous (figure 3). Separate sections of the housing are connected by adapters 5 (Fig. 2) or (Fig. 3) closed by end caps 5 with screws 9. The thickness of the elastic gaskets 4 is such that the ends of the LH are reliably pressed to the ends of the checkers 3. To increase the reliability of the transmission of detonation on the contact LH 7 and explosive charge 3, an intermediate action movie is formed from DS 7 in the form of a flat ring or concentrated charge 15 (Fig. 2,3). At the ends of the supporting elements 6 in the structure shown in FIG. 2, additional elastic gaskets 9 are placed to prevent arcing during assembly and launch of the torpedo into the well. The lower section of the torpedo 10 is connected to the tip of the streamlined shape 11. On the supporting elements 6 are grooves for laying and fixing the detonating cord on the supporting element. The initiator 12 of the explosion is located in the lower or at least in the intermediate section of the torpedo at the lower end of the support element. Placing the initiator of the explosion 12 in the upper part of the torpedo can lead to the breaking of the detonation chain and the lower part of the torpedo and its incomplete operation.

The process of exploding a borehole torpedo proceeds as follows. Upon initiation of detonation in the lower checker of explosive 3, it is transmitted to the helical moderator from DS 7, through it to the next checker, etc. until the torpedo is fully fired. The completeness of the operation of the torpedo is controlled by the sound effect or instrumental methods. During the explosion of a torpedo and the addition of explosive waves that are delayed in relation to each other, a stress state close to the shear occurs in the formation, as a result of which there is a volumetric softening of the rock, and a zone of increased dilatancy permeability with dimensions (r _p ) appears outside the macrocrack zone (r _tr ) ), depending mainly on the mass of the charge and the deceleration interval between explosions of adjacent charges (Fig. 1).

 An example of a specific implementation of the method.

An oil well was put into operation in 1976. The diameter of the production casing in the well is 130 mm. The roof mark of the reservoir is 2544.2 m. The thickness of the reservoir is approximately 10 m. In the lower part of the well has an open trunk. The quantity of reservoir pressure of 280 MPa, the temperature is about 80 ^C. The host sandstone rock is characterized by the following parameters: ρ = 2,6 · March ¹⁰ kg / m ^3, V _p 4615 m / s. It is necessary to decompress rocks in the r ≅r _p mass the mass of an individual charge (2.9 kg) is determined using the volumetric strain curve of the rock sample under uneven dynamic compression taking into account the law of attenuation of stress waves σ _r (r) k (r / r ₃ ) ^μ k, μ are the attenuation constants for a given rock mass, the values of which are taken in the reference literature (k 1.1 · 10 ¹⁰ Pa, μ 1.53). Studies of core material also showed that the most significant effect of dilatancy decompression is observed at ξ σ ₃ / σ ₁ ≅ 0.1. At the time of torpedoing, the well was plugged with a solution of calcium chloride with a specific gravity of γ 1.3 g / cm ³ and shot in the interval of the productive formation with a PKS-80 tape puncher.

The well was torpedoed in two trips by two torpedoes consisting of three charges weighing 2.9 kg each. Explosive charges (checkers, RDX from the TS-84 torpedo kit) were placed in thin aluminum shells with a diameter of 100 mm. Between charges, support elements were introduced from aluminum tubes of smaller diameter (50 mm) 0.6 m long, on which a detonating cord was laid. At the ends of the checkers formed flat fighters from the LH. The calculation of the length of the segments of the LH in moderators was determined by the formula (2). The estimated distance was taken equal to the calculated value of the effective radius of the well from the condition of a twofold increase in the flow rate of the well r _e r _p 3 m. The value of the coefficients a _n ; b _n ; a _t ; b _t :
a _n 2.31 · 10 ³ (12 · 10 ⁶ ) ^-1.21
6.28 · 10 ^-5 s / kg ^1/3 ;
b _n 7.5910 ¹² ( ^{1210 6} ) ^-2.36
0.149 · 10 ^-4 s / m;
and _t 5.01 · 10 ⁴ (12 · 10 ⁶ ) ^-1.3 3.14 · 10 ^-5 s / kg ^1/3 ;
b _t 1.66 · 10 ⁹ (12 · 10 ⁶ ) ^-1.86
1.12 · 10 ^-4 s / m.

t _n 6.28 · 10 ^-6 · 2.99 + 0.149 · 10 ^-4 · 3
(9 + 44.7) · 10 ^-6 53.7 · 10 ^-6 s.

t _t 3.14 · 10 ^-5 · 2.9 + 1.12 · 10 ^-4 · 3
(44.9 + 336) · 10 ^-6 380.9 · 10 ^-6 s.

From where l _LH 7000 (53.7 · 10 ^-6 +
+ 0.4 · 380.9 · 10 ^-6 ) 7000 · 206.1 · 10 ^-6
1.44 m.

 LH segments of this length were wound onto a support tubular element 0.6 m long. Torpedoes were initiated from below by a PG-170 detonator.

 After the development and commissioning of the well, the flow rate of the well was 33.2 tons / day.

 The technical advantage of the dilatancy torpedoing method of the wells, in comparison with the known methods for increasing the permeability of the bottom-hole zones of the wells, along with simplicity and efficiency is the possibility of volumetric irreversible decompression of the rock of the reservoir, an increase in permeability outside the zone of radial fractures by 2–3 times, and the ability to increase the effective well radius up to several meters.

Claims (8)

1. A method of dilatancy torpedoing of wells, including placing dispersed explosive charges in a well in the interval of a productive formation and blasting them with deceleration with respect to each other, characterized in that the deceleration time Δt between explosions of adjacent explosive charges is determined by the formula
Δt = t _n + (0.3 ... 0.5) t _t ,
where t _{n the} time of pressure rise in the front of the blast wave, s,
a _n t _n • Q ^1/3 + b _n • r,
t _t time of action of a blast wave, s,
_t t a _n • Q ^1/3 + b _t • r
a _n = 2.31 • 10 ³ (ρ • V _p ) ^-1.21 ;
a _t = 5.01 • 10 ⁴ (ρ • V _p ) ^-1.3 ;
b _n = 7.59 • 10 ¹² (ρ • V _p ) ^-2.36 ;
b _t = 1.66 • 10 ⁹ (ρ • V _p ) ^-1.86 ;
Q is the mass of explosive charges, kg;
ρ rock density in the reservoir, kg / m ³ ;
V _{p the} speed of sound in the reservoir, m / s,
the mass of the explosive charge is determined for the conditions of volumetric compression of the rock and its maximum dilatancy decompression. 2. A torpedo for dilatancy torpedoing of wells, including a housing with an explosive charge placed in it and an explosion initiator connected to a cable lug, characterized in that it is equipped with supporting elements and detonating cord segments, and the explosive charge is dispersed between the supporting elements and connected by segments detonating cord, wound in a spiral on the supporting elements, while the length l _{d w the} segments of the detonating cord is determined from the expression
l _{d w} D [t _n + (0.3 0.5) t _t ]
where D is the detonation velocity of the detonating cord, m / s;
t _{n the} time of pressure rise in the front of the blast wave, s,
a _n t _n • Q ^1/3 + b _n • r;
t _t time of action of a blast wave, s,
_t t a t • Q ^1/3 + b _t • r;
a _n = 2.31 • 10 ³ (ρ • V _p ) ^-1.21 ;
a _t = 5.01 • 10 ⁴ (ρ • V _p ) ^-1.3 ;
b _n = 7.59 • 10 ¹² (ρ • V _p ) ^-2.36 ;
b _t = 1.66 • 10 ⁹ (ρ • V _p ) ^-1.86 ;
Q is the mass of explosive charges, kg;
ρ rock density in the reservoir, kg / m ³ ;
V _{p the} speed of sound in the reservoir, m / s,
and the length of the supporting elements is made minimal from the condition for the transmission of detonation along the detonating cord in its spiral section.  3. The torpedo according to claim 2, characterized in that the detonating cord at the end is made with an elastic gasket fixing the detonating cord in the explosive charge.  4. The torpedo according to claim 2, characterized in that the supporting elements at the ends are made with elastic inert gaskets.  5. Torpedo according to claim 2, characterized in that the support elements are made with grooves for the detonating cord.  6. A torpedo according to claim 2, characterized in that it is equipped with an intermediate fighter combined at the contact between the detonating cord and the explosive charge.  7. The torpedo according to claim 2, characterized in that the first explosive charge is made with the initiator in the form of an explosive cartridge, and the remaining explosive charges are made with the initiator of the explosion in the form of puncture action units and the possibility of triggering from a shock wave of an adjacent explosion.  8. Torpedo according to claim 2, characterized in that the initiator of the explosion is installed at the lower end of the support elements in the lower part of the device.

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