RU2246610C1 - Method for cleaning face-adjacent bed area - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes forming of gas pillow by forcing gas into inter-tubular space. Further pushing liquid is forced therein with forcing away of liquid from inter-tubular space along tubing column into tank or store, pressure is dropped from inter-tubular space down to atmospheric and hydro-impact is used to effect well face by rotating liquid flow from tubing column. Pillow is formed by plant for forcing pushing liquid and gases. As gas, mixture of air and exhaust gases is used in relation no greater than 2:3. pillow pressure provides for prevention of gas from getting into tubing column. Volume of pushing liquid is determined from formula: V_pl=0.785^.(d $\genfrac{}{}{0ex}{}{\text{2}}{\text{1}}$ -d $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ )^.(H_T-H_gp-H_i-t)^.10^-6, where d₁ - inner diameter of casing column, mm; d₂ - outer diameter of tubing pipes, mm; H_T - depth of lowering tubing column in well, m; H_gp - height of gas pillow in inter-tubular space, m; H_gp=K·P_gp; K - hydrostatic coefficient of resistance to pushing of liquid and gas (K=100 m/MPa), m/MPa; P_gp - end pressure of gas pillow, MPa; H_i-t - inter-tubular space height.

EFFECT: higher safety, higher efficiency.

3 cl, 2 dwg, 2 ex, 1 tbl

Description

The invention relates to the oil industry and can be used to restore the productivity of producing wells and injectivity of injection wells, as well as for the development of wells after drilling.

There is a method of cleaning the bottom-hole formation zone (PZP) by creating a depression on the bottom-hole zone by forcing air into the annular space between the production string and tubing and subsequent air suppression with an aqueous solution of surface-active substances (surfactants) with isolation of the annular space using a packing element ( AS No. 426029 USSR, E 21 B 43/22, 1972).

The disadvantage of this method is the low quality of cleaning and the complexity of the implementation associated with ensuring the tightness of the annulus of the packer element, which significantly reduces its effectiveness.

There is also a method of cleaning the bottom-hole zone of the formation by creating depression by injecting air into the annulus and then suppressing it with liquid, diluting the pressure in the annulus (Allahverdiev R.A. Intensification of the inflow by cyclic impulse action on the bottom-hole zone of the reservoir. Oilfield business and oil transportation .-- No. 3. - 1985. - p.10-12).

The disadvantage of this method is the low cleaning efficiency of the bottomhole formation zone due to the fact that during the rapid discharge of pressure in the annulus there is a rapid release of gas from the oil reservoir, which leads to clogging of the pores of the bottomhole zone.

The closest in technical essence is a method of developing oil wells, including pumping air into the space between the tubing and the casing, purging it with liquid and depressurizing the annulus, and depressurizing is carried out smoothly at a speed of 2-2.5 MPa / h and at the end of the discharge process, a hydraulic shock is made to the bottom of the well with a rotating stream of falling fluid from the tubing of the fluid, and the productive formations are weakly cemented Orodes (patent No. 1682540 RU, E 21 B 43/25, 1993).

The disadvantage of this method is that when air is injected into the space between the tubing and tubing and the casing, if there is a hydrocarbon medium in it, the explosion and fire hazard increase.

In addition, in the process of cleaning the well, a sharp drop in pressure in the tubing and the bottomhole formation zone and the release of air and liquid from the tubing occur, resulting in an emergency. An additional disadvantage of this method is the lack of a preliminary stage of the cleaning of the PPP.

The present invention is aimed at solving the problem of eliminating the risk of an emergency and increasing the success of well treatment.

The technical result realized when using this invention is to increase fire and explosion safety and increase the efficiency of cleaning the bottom-hole formation zone.

The specified technical result in the implementation of the present invention is achieved by the fact that the method of cleaning the bottom-hole zone of the formation, including the creation of a unit for injection of squeezing fluid and gases of a gas pad by injecting gas into the annulus, subsequent injection of the squeezing fluid with the displacement of the fluid from the annulus along the tubing string (Tubing) into a container or barn, depressurizing the annulus to atmospheric pressure and impacting it with a water hammer rotating the well fluid flow from the tubing at the end of the pressure relief process, as the gas is a mixture of air and exhaust gases in a ratio of not more than 2: 3, with the creation of a gas cushion pressure sufficient to avoid ingress of gas into the tubing, while the volume of displacement fluid is determined by the formula:

V _pzh = 0.785 $\genfrac{}{}{0ex}{}{\text{2}}{\text{one}}$ -d $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ ) · (N _NKT -H _go -H _KZ ) · 10 ^-6 ,

where d ₁ is the inner diameter of the casing, mm;

d ₂ - the outer diameter of the tubing, mm;

N _tubing - the depth of descent of the tubing into the well, m;

H _go - the height of the gas cushion in the annulus, m;

H _go = K · R _go ,

K is the hydrostatic coefficient of counteracting the forcing of liquid and gas (K = 100 m / MPa), m / MPa;

P _go - the final pressure of the gas cushion, MPa;

N _KZ - the height of the annulus required for a critical margin when forcing gas through a liquid (N _KZ ≥ 50 m).

The determination of the volume of the squeezing fluid is necessary in order to avoid the ingress of gas into the tubing during the cleaning of the bottomhole zone.

The ratio of air and exhaust gases is chosen no more than 2: 3, by volume, in order to eliminate the ignition of oil gas when pumping the mixture into the annulus.

Prior to injection of the mixture of air and exhaust gases into the annulus, the acid treatment of the bottom-hole zone is performed. The peculiarity of acid treatment is that in order to reduce the reaction rate during hydrochloric acid treatment of the bottom-hole zone of the injection and production wells, surfactants Neftenol VVD, IVF water repellent are added to hydrochloric acid. This allows you to coordinate in time the process of chemical exposure and depressive cleaning of the bottomhole zone and eliminate secondary pollution of the bottomhole zone.

The essence of the invention lies in the fact that as a mixture of air and exhaust gases in a gas cushion of the annular space using a fire and explosion-proof mixture in a hydrocarbon environment. To do this, use a mixture of air and exhaust gases of an internal combustion engine - the main element of the installation of injection into the annulus. The ratio of the volumes of air and exhaust gases, taken no more than 2: 3, ensures the oxygen content in the gas mixture is not more than 8.4% and fire and explosion safety (Levin A.M. Principles of rational gas combustion. L .: Nedra, 1977. - p.30-33).

In addition, the risk of an accident is reduced by taking into account the (permissible) volume of displacement fluid, which depends on the parameters of the downhole equipment and the gas cushion.

Figure 1 shows a diagram of the implementation of the method; figure 2 is a variant of a block diagram of a device for producing an explosion-proof gas.

The implementation scheme (FIG. 1 and FIG. 2) includes a casing 1, a tubing 2, a connecting pipe 3, valves 4-9, pipelines 10-12, an installation for pumping a mixture of air and exhaust gases and water 13 connected through pipes 11, 12 and 3, valves 5, 6 and 7 with annular space 14. The output of the installation 13 is also connected via an exhaust gas cooler 15, a gas flow meter 16 to the inlet of the ejector 17, the second input of which is connected through the valve 18 and the air flow meter 19 to atmospheric by air. The output of the ejector 17 is connected to the input of the installation 13, the second input of which is connected through a water flow meter 20 with a capacity of 21 for water. As an installation for pumping a mixture of air and exhaust gases and water 13 into the annular space 14, pump-ejector, compressor, and gas booster units, for example, self-propelled units of the UNG 8/15 type, which provide the required parameters of the gas-liquid mixture in terms of pressure and performance, can be used.

The connecting pipe 3 is equipped with a pressure gauge 22. The casing 1 is connected to the PPP and the formation 23 through perforations 24. A flow rotator 25 rotates the liquid flow incident on the tubing to further clean the bottom.

The method is implemented as follows. Before injection of the mixture of air and exhaust gases into the annulus 14, acid treatment is performed (the acid treatment scheme is not shown in the drawings). The peculiarity of acid treatment is that to reduce the reaction rate during hydrochloric acid treatment of the bottom-hole zone of the reservoir of injection and production wells, surfactant Neftenol VVD, (0.4-1.0%), water-repellent IVV-1 (0.1-0 5%), while hydrochloric acid with a concentration of 12.0-24.0 wt.% - 98.5-99.5%. This allows you to coordinate in time the process of chemical exposure and depressive cleaning of the bottomhole zone and eliminate secondary pollution of the bottomhole zone.

After the acid treatment of the BCP by installation 13 in the annular space 14 create a gas cushion of a mixture of air and exhaust gases with a pressure of 8-10 MPa. A mixture of air and exhaust gases is obtained when the internal combustion engine (not shown) of the installation 13 is turned on, the exhaust gases pass through the cooler 15, the flow meter 16 and the ejector 17, in the latter a vacuum is formed, causing air to flow through the flow meter 19. Knowing the exhaust flow gases and the required ratio of air and gases, using the valve 18 set the allowable air flow. With a ratio of air consumption and gas mixture of 2: 3 or less, the oxygen content in the mixture does not exceed 8.4% and the mixture is safe under conditions of ignition of a hydrocarbon medium. When injecting a mixture of gases, the valves 6, 7 and 9 are open, and the valves 4, 5 and 8 are closed. The liquid displaced by the mixture of air and exhaust gases from the annulus 14 through the tubing through a valve 9 is fed into a container or a barn (not shown in the drawing). After increasing the pressure of the mixture of air and exhaust gases in the annulus 14 to the desired value (for example, up to 10 MPa), the valve 6 is closed, and the installation 13 is transferred after opening the valve 5 to the pump mode, i.e. injection of fluid into the annulus. The volume of squeezing fluid V _pzh is determined by the proposed formula. So, when P _go = 10 MPa, N _KZ = 50 m, d ₁ = 130 mm and d ₂ = 73 mm, V _pzh = 8.6 m ³ . In this case, the valves 4, 6 and 8 are closed, and 5 and 9 are open. The same amount of fluid (namely, 8.6 m ³ ) is displaced from the tubing.

After that, the liquid is discharged from the annulus 14 through the pipeline 10 into the reservoir (not shown in the drawing). The valve 7 controls the rate of pressure drop within 2-2.5 MPa / h. The pressure change is controlled by a pressure gauge 22. In this case, the valve 4 is open, and the valves 5, 6, 8 and 9 are closed.

The mixture of air and exhaust gases is poured out gradually with a pressure drop rate of 2–2.5 MPa / h. The regulation is carried out by the valve 4. This ensures a smooth increase in depression on the reservoir 23 and the pressure drop in the PPP. As air is discharged, the well is filled with pollution products, chemical reaction wastes, and the bottomhole layer is cleaned with formation fluid.

After rarefaction of the annular space to atmospheric pressure, additional drainage of the formation 23 and bottom cleaning are performed: the valve 9 is opened and the liquid column in the tubing 2 falls onto the bottom of the well. The impulse effect resulting from the fall of fluid from the tubing to the bottom leads to the opening of old and the formation of new microcracks, the destruction of deposits on the perforations 24 of the casing 1 without disturbing the technical condition of the well. A rotating stream carries along the sludge from the perforations.

Immediately after the last operation, they begin to repeat all operations, i.e. the implementation of the second cycle. The cycles are repeated 3-4 times. When oil appears, it is sent to the reservoir by opening the valve 8. Work is stopped if the pressure of the mixture of gases does not exceed 5 MPa.

Example 1. Determination of the volume of the squeezing fluid.

Initial data: the depth of the tubing _run into the well N _tubing = 1600 m, the liquid level in the annulus H _w = 0 m, the final pressure of the gas cushion P _go = 10 MPa, the hydrostatic coefficient of counteracting the forcing of the fluid K = 100 m / MPa, the height of the annulus required for a critical margin of N _KZ = 50 m, the inner diameter of the casing string d ₁ = 130 mm, the outer diameter of the tubing d ₂ = 73 mm. The height of the gas cushion is equal to N _go = 100 · 10 = 1000 m. The volume of the squeezing liquid is

V _pzh = 0.785 · (130 ² -73 ² ) · (1600-1000-50) · 10 ^-6 = 5 m ³

The volumes of displacement fluid for the possible process parameters are shown in table 1.

Table 1
Calculation results for displacement fluid for different wells N _tubing , m P _go , MPa N _go , m N _W , m V _pzh , m ³ 1200 8 800 0 3.18 400 - 600 - 10 1000 0 1.36 400 - 600 - 1600 8 800 0 6.81 400 3.18 600 1.36 10 1000 0 5,0 400 1.36 600 - 2000 8 800 0 10.44 400 6.81 600 5,0 10 1000 0 8.63 400 5,0 600 3.18 Note: For all calculation options, d ₁ = 130 mm, d ₂ = 73 mm.

Example 2. When conducting hydrochloric acid treatments of wells in the fields of Western Siberia, the success rate is, on average, 51%. The success rate of depression treatment under the same conditions does not exceed 71%. When conducting joint hydrochloric acid and depressive treatment at the test sites according to the claimed method, the success rate increases, on average, to 80%.

Thus, the preliminary acid treatment, the use of explosive and fireproof gas mixtures in hydrocarbon environments, the injection into the annular space of the allowable volume of liquid can significantly (1.5-2.0 times) increase the efficiency of the cleaning of PPP, increase by 10-20 % success rate of treatments, to reduce the risk of an accident during the implementation of the method.

Claims (3)

1. The method of cleaning the bottom-hole zone of the formation, including the creation of a unit for injection of the squeezing fluid and gases of the gas cushion by pumping gas into the annulus, the subsequent injection of the squeezing fluid with the displacement of the annulus from the annulus along the tubing string into the tank or barn, discharge pressure from the annulus to atmospheric pressure and the impact of a hydraulic shock on the bottom of the well with a rotating fluid flow from the tubing at the end of the pressure relief process, which differs I mean that as a gas use a mixture of air and exhaust gases in a ratio of not more than 2: 3 with the creation of a gas cushion with pressure, which ensures that gas does not enter the tubing, and the volume of the squeezing liquid is determined by the formula V _pzh = 0.785 (d $\genfrac{}{}{0ex}{}{\text{2}}{\text{one}}$ -d $\genfrac{}{}{0ex}{}{\text{2}}{\text{2}}$ ) (N _tubing -H _go -N _KZ ) · 10 ^-6 , where d ₁ is the inner diameter of the casing, mm; d ₂ - the outer diameter of the tubing, mm; N _tubing - the depth of descent of the tubing into the well, m; N _th - the height of the gas cushion in the annulus, m; H _go = KP _go , K is the hydrostatic coefficient of counteracting the forcing of liquid and gas, K = 100 m / MPa; P _go - the final pressure of the gas cushion, MPa; H _kz - height annulus necessary to reserve at critical jacking gas liquid (H ≥50 _kOe m). 2. The method according to claim 1, characterized in that the exhaust gases of the installation are used to pump the squeezing liquid. 3. The method according to claim 1, characterized in that prior to injecting the mixture of air and exhaust gases into the annulus, acid treatment of the bottomhole formation zone is performed.

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