RU2321731C2 - Oil field development method (variants) - Google Patents

Abstract

FIELD: oil production, particularly oil field development methods.

SUBSTANCE: method involves injecting water into well provided with production string via tubing; installing isolation devices, namely packers, in well; lowering liquid-gas ejector connected to tubing in well, wherein the ejector includes low-pressure chamber for water-gas mixture injection having outlet communicated with water-saturated volume. In the case of gas pool or gas cap presence in oil field and gas pool/gas cap location under water-gas mixture injection interval one isolation device is installed over water-gas mixture injection interval. The second device is arranged between water-gas mixture injection interval and gas pool or gas cap. Low-pressure chamber of gas-liquid ejector lowered in well is communicated with liner through cavity defined by outer tubing wall and inner wall of production string, namely pipe. Lower pipe end is communicated with gas pool through perforated orifices. Upper end of production string, namely pipe, is communicated with hole annuity.

EFFECT: increased oil recovery from oil deposit, decreased capital and operational costs.

2 cl, 2 dwg

Description

The invention relates to the oil industry, in particular to methods for developing an oil deposit by forcing a water-gas mixture into a water-saturated volume below the oil-water contact (WOC).

Known methods of injecting into the reservoir water-gas mixture formed in the process of ejection: Pat. 2088752 Е21В 43/20 “Method for the development of an oil field”; Pat. 2269646 ЕВВ 43/20 "Method for the displacement of oil from the reservoir"; Z. No. 93003931 Е21В 43/22 “Method for the development of an oil field”; Z. No. 94007734 Е21В 43/22 “Method for the development of an oil reservoir”, Z. No. 99121601 Е21В 43/20 “Method for the displacement of oil from a reservoir”. In this case, the gas-water mixture is prepared either on the surface or in the wellbore.

To mix water and gas by ejection at a depth in the wellbore, water and gas are simultaneously pumped from the wellhead along different lines: Pat. 2269646 "Method for the displacement of oil from the reservoir." This requires an external high-pressure gas source, as well as communications for supplying gas to the wellhead. In some cases, gas cleaning and compression may be required. In addition to additional capital costs due to the supply of external gas intended for mixing with water, there are also additional operating costs. This is a significant drawback of methods, including the supply of gas from the wellhead for ejection into the well.

Closest to the proposed is the "Method for the development of oil reservoir" US Pat. No. 2060378, IPC 6 Е21В 43/24.

The proposed method for developing an oil reservoir eliminates the need for gas to be supplied to the liquid-gas ejector from the wellhead. As a source of high pressure gas, gas strata or gas caps available in the section of the well below or above the injection interval of the gas-water mixture are used.

In the proposed method, gas is taken from one of these sources and without lifting to the surface is directed to a low-pressure chamber of a liquid-gas ejector mounted on a column of elevator pipes in the interval of injection of the water-gas mixture into the formation.

The technical result to which the invention is directed is to increase oil recovery, as well as to reduce capital and operating costs.

To achieve the named technical result, it is proposed:

1. A method of developing an oil deposit, including injecting water into a well with a production column through a string of elevator pipes, installing uncoupling packers in the well, launching a liquid-gas ejector with a low-pressure chamber into the well on a string of elevator pipes to inject a gas-gas mixture, the discharge of which hydraulically communicate with a water-saturated volume, if there is a gas reservoir or a gas cap in the reservoir located below the water-gas mixture injection interval, one of the uncoupling devices is installed above the inter tore off the injection of the water-gas mixture, and the second, between the interval of injection of the gas-water mixture and the gas reservoir or gas cap, the low-pressure chamber of the liquid-gas ejector lowered into the well through the cavity formed between the outer walls of the lift pipes and the inner walls of the production casing pipe, communicate with the shank , the lower end of which is communicated through perforations with a gas reservoir, while the production string-pipe from above communicates with the annulus.

2. A method of developing an oil deposit, including injecting water into a well with a production column through a column of elevator pipes, installing an uncoupling device-packer in a well, lowering a liquid-gas ejector with a low-pressure chamber into the well at a column of elevator pipes to inject a gas-gas mixture, the discharge of which hydraulically communicate with the water-saturated volume, in the presence of a gas reservoir or gas cap in the reservoir and their location above the interval of injection of the water-gas mixture, the uncoupling device-packer is installed between and with the gas-gas mixture injection interval and the gas reservoir or gas cap, the low-pressure chamber of the liquid-gas ejector lowered into the well is placed above the disconnecting device-packer and communicate through the cavity formed between the outer walls of the lift pipes and the inner walls of the production string through the perforations with gas formation, while the production casing-pipe on top communicate with the annulus.

The proposed method is illustrated in the drawing. Figure 1 presents a variant of the proposed method in relation to the location of the gas reservoir in the context of the well below the interval of injection of the gas mixture.

According to the proposed method according to this option, in the well 1, intended for pumping a water-gas mixture into a water-saturated volume 2, located below the OWC, disconnecting packers are installed: the top 3 is above the pump-gas mixture injection interval, and the lower 4 is below the pump-gas mixture injection interval. In the interval between these uncoupling devices-packers, a liquid-gas ejector 6 is installed on the column of elevator pipes 5, a high-pressure working nozzle 7 is hydraulically in communication with the internal cavity of the column of elevator pipes 5, and a low-pressure chamber 8 through the cavity 9 formed between the outer walls of the ejector 6 and the inner walls of the pipe 10, communicate with the shank 11, the lower end of which is communicated through perforations 12 with the gas reservoir 13. The liquid-gas ejector 6 is provided with two diameters cial oppositely vykidami 14 having fluid communication through the perforations 15 with water-saturated volume 2, located under the oil pool 16.

The method according to this option is as follows. The water supplied under pressure from the wellhead to the string of elevator pipes 5 enters the high-pressure working - active nozzle 7 of the ejector 6. Due to the high speed of the outflow of water from the nozzle 7 in the low-pressure chamber 8, a reduced pressure is created, which contributes to the flow of gas from the gas reservoir 13 through the perforation holes 12, the shank 11, the cavity 9 into the low-pressure chamber 8. The water-gas mixture formed in the liquid-gas ejector 6 through vykidy 14 and perforation holes 15 enters the water-saturated volume 2.

A necessary condition for the operation of the ejector 6 in the considered embodiment is to reduce the dynamic pressure P _n1 in the low-pressure chamber 8 to a value that ensures gas flow from the gas reservoir 13 into the low-pressure chamber with a given flow rate Q ₁ . The required value of P _n1 is found by the formula (I):

where P _g1 - reservoir pressure in the gas reservoir 13;

A ₁ , B ₁ - filtration resistance coefficients for gas inflow into the well from the gas reservoir 13;

D ₁ , F ₁ , λ ₁ - respectively, the inner diameter, living area and coefficient of hydraulic resistance of the shank 11;

H ₁ - the vertical distance from the middle of the interval of the perforations 12 to the entrance to the low-pressure chamber 8;

T ₁ , Z ₁ - respectively, the average temperature and supercompressibility coefficient of the gas along the length of the shank 11;

R _article ; T _article - respectively pressure and temperature under standard conditions;

g is the acceleration of gravity;

ρ _st - gas density under standard conditions.

Figure 2 presents a variant of the proposed method in relation to the location of the gas reservoir in the context of the well above the interval of injection of the gas mixture.

According to the proposed method according to this option, in the well 1, intended for pumping a water-gas mixture into a water-saturated volume 2, located below the WOC, an uncoupling device-packer 3 is installed between the gas reservoir 13 and the interval for pumping the gas-water mixture into the water-saturated volume 2; a liquid-gas ejector 6 is installed on the column of elevator pipes 5. In this case, a high-pressure working - active nozzle 7 and a low-pressure chamber 8 of the ejector are located above the packer 3. The low-pressure chamber 8 is communicated through the cavity of the annulus 17 formed between the inner walls of the production well casing D _ve and the outer walls of the elevator pipes D _nl , the perforations 12 with the gas reservoir 13, and the discharge 14 of the liquid-gas ejector 6 through the shank 11 and the perforations 15 communicate with the water-saturated a lift 2 located under the oil reservoir 16.

The method according to this option is as follows. The water supplied under pressure from the wellhead to the string of elevator pipes 5 enters the high-pressure working - active nozzle 7 of the ejector 6. Due to the high speed of the outflow of water from the nozzle 7 in the low-pressure chamber 8, a reduced pressure is created, which contributes to the flow of gas from the gas reservoir 13 through the perforations 12, the cavity of the annulus 17 into the low pressure chamber 8. The water-gas mixture formed in the liquid-gas ejector 6 through the outlet 14 of the perforations 15 enters the water-saturated volume 2.

A necessary condition for the operation of the ejector 6 in this embodiment is to reduce the dynamic pressure P _n2 in the low-pressure chamber 8 to a value that ensures the flow of gas from the gas reservoir 13 into the low-pressure chamber with a given flow rate Q ₂ . The value of P _n2 is found by the formula (4):

where P _g2 - reservoir pressure in the gas reservoir 13;

And ₂ , In ₂ - the coefficients of the filtration resistance to the influx of gas from the gas reservoir 13;

D ₂ , F ₂ , λ ₂ - respectively, the hydraulic diameter, living area and coefficient of hydraulic resistance of the cavity of the annulus 17;

N ₂ is the vertical distance from the middle of the interval of the perforations 12 to the entrance to the low-pressure chamber 8;

T ₂ , Z ₂ - respectively, the average temperature and the coefficient of supercompressibility of the gas along the length of the cavity of the annulus 17;

R _article , T _article - respectively, pressure and temperature under standard conditions;

g is the acceleration of gravity;

ρ _st - gas density under standard conditions.

The operation mode of the liquid-gas ejector: the pressure at the inlet to the high-pressure working - the active nozzle of the ejector, the flow rate supplied to the ejector from the mouth of the water, the flow rate of the gas transferred to the low-pressure chamber, the pressure of the gas-gas mixture at the outlet of the ejector is calculated by known methods: I. Mishchenko . and others. "The choice of the method of operating wells in oil fields with hard-to-recover reserves." - M., 2005.

The pressure control in the low-pressure chamber can be carried out by calculation by measuring the pressure in the cavity of the annulus of the well — between the inner walls of the production string pipes and the outer walls of the lift pipe string, including at the wellhead.

When the gas reservoir is located below the injection interval of the water-gas mixture, when an uncoupling device-packer is installed above the gas formation - to control the pressure in the low pressure chamber of the ejector, the cavity of the annulus above the uncoupling device-communicator connected with the low-pressure chamber is used.

When the gas reservoir is located above the injection interval of the water-gas mixture, when there is no disconnecting device-packer above the gas reservoir, it is also possible to use pressure measurements in the annulus of the well, including at the wellhead.

The flow rate of gas entering the low-pressure chamber from gas reservoirs or gas caps is controlled by the calculation method based on preliminary studies, using indicator lines - the relationship between the gas flow rate and the value of the difference of the squares of pressure: reservoir and in the well in the gas supply interval.

Claims (2)

1. A method of developing an oil deposit, including injecting water into a well with a production column through a string of elevator pipes, installing uncoupling packers in the well, launching a liquid-gas ejector with a low-pressure chamber into the well on a string of elevator pipes to inject a gas-gas mixture, the discharge of which hydraulically communicate with a water-saturated volume, characterized in that in the presence of a gas reservoir or gas cap located below the water-gas mixture injection interval, one of the uncoupling devices the pressure is lowered above the interval of injection of the gas-water mixture, and the second, between the interval of injection of the gas-gas mixture and the gas reservoir or gas cap, the low-pressure chamber of the gas-liquid ejector lowered into the well through the cavity formed between the outer walls of the lift pipes and the inner walls of the production casing pipe, is communicated with the shank , the lower end of which is communicated through perforations with a gas reservoir, while the production string-pipe from above communicates with the annulus. 2. A method of developing an oil deposit, including injecting water into a well with a production column through a column of elevator pipes, installing an uncoupling device-packer in a well, lowering a liquid-gas ejector with a low-pressure chamber into the well at a column of elevator pipes to inject a gas-gas mixture, the discharge of which hydraulically communicate with a water-saturated volume, characterized in that in the presence of a gas layer or gas cap in the reservoir and their location above the interval of injection of the gas-water mixture, the uncoupling device-packer set between the interval of injection of the water-gas mixture and the gas reservoir or gas cap, the low-pressure chamber of the gas-liquid ejector lowered into the well is placed above the disconnecting device-packer and communicated through the cavity formed between the outer walls of the elevator pipes and the inner walls of the production string through the perforations with gas formation, while the production casing-pipe on top communicate with the annulus.

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