RU2229021C1 - Method for impact influence onto oil layer - Google Patents

Abstract

FIELD: oil extracting industry. SUBSTANCE: method includes increasing of liquid column in tubing string lowered in the well until excessive pressure is reached in tubing string and impact chamber limited by casing string and rigid packer, overlapping ring-shaped space between casing pipe and tubing string. Generation of pressure impulses is provided for by sharp periodical lowering and increasing of pressure in force- pumping line, which connects force pump with tubing column, and transfer of pressure impulses from impulse chamber to oil layer. According to the method, a column of liquid in tubing column is formed of at least two layers of liquids of different density. Density of lower liquid layer is taken higher than density of upper liquid layer. Height of liquid layers is determined on basis of condition of maximum excessive pressure taking place in impact chamber during hydraulic impact according to analytic expression. For limiting of impact chamber an additional rigid packer is mounted in bottom-hole of well. Concrete barrel may be used instead of additional packer. EFFECT: increased effectiveness due to increased range of adjustment of impact influence onto oil layer and lowered energy losses in impact chamber. 1 ex, 1 tbl

Description

The invention relates to oil production using pulsed effects on the oil reservoir.

A known method of pulsed exposure to an oil reservoir, comprising supplying a liquid under pressure to a well through a tubing string (tubing) and sequentially destroying the diaphragms installed therein. The pressure impulses that arise in this case are transmitted to the oil-saturated bottom-hole zone of the well (Suchkov B.M. Application of hydropercussive action on the formation with an acid solution. - M .: VNIIOENG, 1988, pp. 7-15).

The disadvantages of this method are:

- limited number of pulses, determined by the number of diaphragms installed in the tubing;

- limited pulse repetition rate, since between successive impact pulses it takes time to lower a calibrated ball into the well to close the hole in the next diaphragm.

The closest technical solution (prototype) is a method of pulsed impact on an oil reservoir, which includes increasing the pressure of a liquid column in a cased well by a power pump and transmitting pressure pulses from the well to the reservoir, which are generated due to a sharp periodic discharge and pressure increase in the injection line, which reports the power a pump with a tubing string lowered into the well, while pressure pulses are transmitted to the reservoir from a chamber bounded by a casing string and a rigid packer, deflated into the well on tubing (Patent RF, №2151280, E 21 B 43/25, 1997).

The disadvantages of the known technical solutions are:

- limited ability to control the amplitude of the pressure pulses only due to the pressure created by the power pump, ceteris paribus;

- energy loss of impulse exposure associated with the fact that the impulse chamber, as a rule, is limited from below by a rubber plug used in cementing wells, which leads to energy loss on it.

The purpose of the invention is to increase the efficiency of the method by expanding the range of regulation of the impulse effects on the oil reservoir and reducing energy losses in the pulse chamber.

This goal is achieved by the fact that in the method of pulsed action on the oil reservoir, which includes increasing the pressure of the liquid column in the tubing by the power pump, which is lowered into the well, until overpressure occurs in the reservoir and the pulse chamber bounded by the casing and rigid packer , overlapping the annular space between the casing pipe and the NCC, the generation of pressure pulses due to a sharp periodic discharge and pressure increase in the discharge line, communicating the power pump with the NCC, and p soap has pressure pulses from the pulse combustor in the oil reservoir, the liquid column in SAC is formed by at least two layers of different-density fluids, the density of the lower liquid layer higher than the density of the upper liquid layer, and the height of the layers of liquids is determined from the condition of maximum overpressure? P _y developed in a pulse chamber during water hammer

ΔP _y ≤ P _wd - (hρ _l + (H - h) ρ _t ) g,

where R _zd - the maximum allowable pressure in the pulse chamber at the bottom of the well; H is the total length of the NCC; h is the height of the layer of light fluid; ρ _t , ρ _l - density of heavy and light fluids; g is the acceleration of gravity,

at the same time, an additional hard packer or cement cup is installed at the bottom of the well, which limits the impulse chamber.

The advantages of using a liquid filling the NCC and the pulse chamber of different-density liquids as a column is due to the fact that, ceteris paribus (the same response time and size of the control valve bore, etc.) if the NCC has the upper H length part, from the wellhead to depth h, is filled with a medium with a low density ρ _l , and the lower part is filled with a medium with a high density ρ _t , then the excess hydrostatic pressure on the bottom of the well, which in this case is equal to the pressure in the pulse chamber pe, equal to P _s.st. = (hρ _l + (H-h) p _t ) g. If _we denote by ΔР _у the excess pressure created by the source of pressure during hydraulic shock, then based on the condition of non-fracture of the casing, which occurs when pressure P _{zr is reached} , the pressure at the bottom of the well during hydraulic shock P _zy must satisfy the condition

P _s.u. = ΔP _y + P _s.st. = ΔP _y + (hρ _l + (H - h) ρ _t ) g≤P _s.r.

From this formula it follows that the lower the hydrostatic pressure at the bottom of the well R _s.st , i.e. the lower the density of the liquid, the greater the excess pressure due to the hydraulic shock ΔР _у can be created, and therefore, the amplitude of the pulse action on the oil reservoir can be increased.

As a condition that determines the maximum allowable pressure created by water hammer, the condition can be used that in the bottom-hole zone there should be no destruction of the original oil reservoir. In this case, the limiting pressure that can develop during hydraulic shock of the formation should not more than double the rock pressure R _g (Popov A.A. Impact impacts on the bottom-hole zone of wells. - M .: Nedra, 1990, p. 85) .

In the general case, it can be written that the overpressure created at the bottom of the well due to hydraulic shock must satisfy the condition

ΔP _y ≤ P _wd - (hρ _l + (H-h) ρ _t ) g, (1)

where P _zd - the maximum allowable pressure at the bottom of the well, defined as the value of P _zr , 2P _g or other condition.

The excess pressure created with a water hammer ΔР _у is associated with the excess pressure created by the power pump ΔР _н , by the ratio (ibid., Pp. 80-85)

ΔР _у = ((2 · ΔР _н / ξ) (К / (1+ (d · K / δ / Е)))) ^1/2 ,

where ξ is the velocity coefficient; K is the modulus of elasticity of the liquid (Pa); d is the inner diameter of the casing string (m); δ is the wall thickness of the casing (m); E is the elastic modulus of the casing wall material (Pa).

If for the sake of simplicity we put in the last formula that the velocity coefficient is equal to unity, for d = 10 ^-1 m, δ = 10 ^-2 m, E = 2 · 10 ⁹ Pa (water) and 1.3 · 10 ⁹ Pa (oil) , E = 200 · 10 ⁹ Pa, which corresponds to the expected values of the parameters, the last formula goes into the approximate

ΔP _y = (2 · ΔP _n · K) ^1/2 . (2)

From the last formula it follows that the same impulse of excess pressure can be created either by increasing the excess pressure ΔP _n created by the pump in a liquid with a small modulus of elasticity E, or by lowering the pressure ΔP _n in a liquid with a large modulus of elasticity E.

Thus, the height of the layers of light and heavy fluids should be determined from the condition of the maximum value of excess pressure that a high pressure pump ΔР _н can develop, fluid properties (ρ and К), the depth of the oil reservoir (N) and the maximum allowable pressure at the bottom of the well R _w

The installation of a hard packer or cement cup at the bottom of the well is aimed at reducing energy losses from the pressure impulse, which are dissipated through the rubber plug commonly used in cementing wells.

The drawing shows a diagram of the piping of the well for a pulsed impact on the oil reservoir.

The method can be implemented as follows.

The impact on the oil reservoir is carried out through the cemented casing 1 with an unperforated or perforated interval, if the latter does not have fluid inflow or injectivity.

A tubing string 2 is installed in the well, and the annulus between the casing and tubing above the top of the formation is blocked by a hard packer 3. A hard packer or cement cup 4 is installed on the bottom of the well, below the bottom of the formation. The pulse chamber 5 forms part of the casing bounded by packers 3 and 4 A controllable valve 8 is installed on the flow line 6 of column 2 connected to the high-pressure power source 7. Valve 8 can operate from a control device (not shown) or when the specified pressure limit is reached.

When the high-pressure pump 7 is operating in the pulse chamber 5, the maximum overpressure occurs, upon reaching which the valve 8 switches and the excess pressure in the liquid in line 6 through the pipeline 9 is discharged into the reservoir 10. At the same time, the valve 8 switches the fluid flow from line 6 through the pipe 11 into the tank 10, i.e. pump 7 is put into recirculation mode. After a sharp pressure relief to a predetermined value, the valve 8 returns to its original state, and the pressure in the chamber 5 again rises to a predetermined level.

Parameter Definition Example

P _wd = 8 · 10 ⁷ Pa, N = 2000 m, ΔP _n = 10 ⁶ Pa, ρ _l = 850 kg / m ³ , K _l = 1.33 · 10 ⁹ Pa, ρ _t = 850 kg / m ³ , K _t = 2 · 10 ⁹ Pa.

Setting h = 0, i.e. if only heavy liquid (water) is used, we obtain that the calculation by formula (1) gives ΔР _у ≤ 6 · 10 ⁷ Pa, and by formula (2) ΔР _у = 6.3 · 10 ⁷ Pa. This means that the generated pressure pulse exceeds the permissible value.

Setting h = 2000 m, i.e. if only light liquid (oil) is used, we obtain that the calculation according to formula (1) gives ΔРу ≤ 6.3 · 10 ⁷ Pa, and according to formula (2) ΔР _у = 5.2 · 10 ⁷ Pa. This means that the generated pressure pulse can be increased, since it is less than the maximum permissible.

Optimal will be the filling of the tubing with fluids, in which the value of the allowable pressure pulse will be equal to the pressure pulse developed during hydraulic shock.

The elastic modulus of a liquid column, consisting of two different density layers

K = K _t / ((1-h / H) + (hK _t / H / K _l )).

Equating (1) and (2) we get that at h = 180 m ΔР _у = 6.06 · 10 ⁷ Pa. Thus, the height of the lower layer, consisting of water, is equal to 1820 m, in the upper, consisting of oil, - 180 m.

By changing the height of the layer of light fluid h, it is possible to reduce the hydrostatic pressure at the bottom of the well P _s.st. , and on the other hand, the column of light fluid acts as a kind of damper, somewhat reducing the amplitude of the hydraulic shock that is created at the bottom of the well, since, as a rule, a light fluid has a lower modulus of elasticity.

Pressure pulses create hydraulic shocks in chamber 5, which are transmitted through the walls of the casing and cement stone 13 to the reservoir 12. The amplitude of pressure surges is determined by the working pressure developed by pump 7, and the pulse repetition rate corresponds to the response frequency of valve 8, provided that the pump performance is much more than the volume of fluid discharged into the tank 10, and does not require any operations in the well.

The proposed method of pulsed impact on the oil reservoir has wide control possibilities both in amplitude and in frequency of pulsed impact and does not impose any special conditions on the well design and used high pressure pumps and control valves. After completion of the impact and formation of additional cracks in the oil reservoir, the process of developing a non-perforated well (perforation and inflow of oil) can be performed using conventional technology.

Claims (1)

A method of impulse action on an oil reservoir, including increasing the pressure of a liquid column in a tubing string lowered into a well by a power pump until overpressure occurs in the tubing string and pulse chamber bounded by the casing string and a rigid packer covering the annular space between the casing pipe and tubing string, the generation of pressure pulses due to a sharp periodic discharge and pressure increase in the discharge line, informing the power us os with a tubing string, and the transmission of pressure pulses from the pulse chamber to the oil reservoir, characterized in that the liquid column in the tubing string is formed from at least two layers of different density liquids, while the density of the lower liquid layer is higher than the density of the upper liquid layer, and the height of the liquid layers is determined from the condition of the maximum overpressure ΔР _у developed in the pulse chamber during water hammer: ΔP _y ≤ P _zd - (hρ _l + (H - h) ρ _t ) g, where P _BH is the maximum allowable pressure in the pulse chamber at the bottom of the well; h is the height of the layer of light fluid; ρ _l is the density of the light fluid; N is the total length of the tubing string; ρ _t is the density of a heavy liquid; g is the acceleration of gravity, at the same time, an additional hard packer or cement cup is installed at the bottom of the well, which limits the impulse chamber.