RU2490438C1 - Oil deposit development method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves delivery of water-gas mixture to oil deposit through an injection well; the mixture is prepared at the mouth of the injection well by means of a mixer and then delivered to the mixer under pressure of water and gas. According to the invention before delivery of gas stream light hydrocarbon fractions, foe example, oil, gas condensate, associated gas or a mixture of low-pressure gas with fractions of hydrocarbons C_2+higher are input into the mixer by means of an ejector. At that mixing of high-pressure gas with a stream of gas having high concentration of hydrocarbon fractions C_2+higher is carried out by means of an ejector installed in the gas well in production tubing over the roof of high-pressure gas formation. The stream of gas from high-pressure gas formation in drill string - borehole annulus is isolated by means of an isolating packer from the stream of low-pressure gas and delivered to high-pressure nozzle of the ejector. At that the stream of low-pressure gas with high content of C_2+higher fractions fed from the well mouth through borehole-drill string annulus of the gas well is sent to low-pressure chamber of this ejector.

EFFECT: improvement of oil recovery factor with simultaneous prevention of low-pressure gas compression using compressors or similar power plants.

4 cl, 1 dwg

Description

The invention relates to the oil industry, in particular to methods for developing an oil reservoir with injection, in order to increase oil recovery, water-gas mixture.

Known methods for the development of oil deposits with injection of a water-gas mixture into the reservoir - RF patents Nos. 2088752, 2269646, 2321731, 2391495, 2060378. A gas-water mixture is prepared by mixing water and a hydrocarbon or other gas or gas mixture with a liquid using ejection or ejection-dispersing devices.

A disadvantage of the known methods is either the insufficiently high displacement coefficient of the oil injected into the oil-saturated formation by the water-gas mixture — when using a high-pressure gas with a low hydrocarbon content of C _{2 +} fractions to prepare the mixture _. or high capital, operating and energy costs - when using a low-pressure associated (petroleum) gas, which must be precompressed before being fed to the ejection-dispersing device (EDU).

Closest to the proposed is the method according to patent No. 2060378, according to which associated petroleum low-pressure gas, before being fed to the well for mixing with water in the downhole ejector, is compressed using a liquid-gas ejector mounted on the surface (Figs. 3, 4). The disadvantage of this method is the need to create a high-pressure flow of water supplied to the liquid-gas ejectors, spending energy on this to operate the pumps.

It is known that with an increase in the content of hydrocarbon fractions of C _{2 + higher} fractions in the gas displacing oil _. the coefficient of oil displacement by gas increases (Butorii O.I., Piyakov G.N. Generalization of experimental studies to determine the effectiveness of applying gas and water-gas effects on the reservoir. NTS "Oilfield business." - 1995, No. 8-10, pp. 54-59 ) For example, when instead of a dry hydrocarbon gas, a mixture containing 16% of C ₂ -C ₄ components and 84% methane is used, the growth rate of the oil displacement coefficient increases by 2 times, from 15-16% to 31-32%. It is noted that the technology of stimulation of the formations should be carried out using associated (petroleum) gas. Containing a sufficient amount of C _{2 +} fractions _higher. . However, the difficulty of using associated (petroleum) gas is due to the low pressure, usually occurring at the outlet of this gas from oilfield processing plants, in the range of 1-1.5 MPa, and the required amount of heavy hydrocarbon fractions is not always contained in this gas.

Ensuring the content in the gas supplied to the EDU in the required quantities of the C _{2 +} fraction _higher. It is proposed in the absence of associated (petroleum) gas with the required hydrocarbon content of the fraction C _{2 + higher.} , to carry out by introducing into the flow directed into the annular space of the gas well gas of liquid hydrocarbons - oil or gas condensate.

Obtained in a borehole gas ejector operating due to the natural energy of a high-pressure gas, a mixture of gases, or a mixture of high-pressure gas with light liquid hydrocarbons, is sent to the input of the EDF with a pressure sufficient for the formation of HCV.

The invention solves the issues of increasing the coefficient of oil displacement from the reservoir due to the saturation of the high-pressure gas with additional C _{2 +} fractions _higher. while eliminating the need to compress low-pressure gas using compressor or other power plants. The mixture of high-pressure gas with a low-pressure (associated) gas or light liquid hydrocarbons obtained in an ejector operating due to the natural energy of a high-pressure gas is directed to the input of the EDF with a pressure sufficient to form an HCV.

Technical solution to the problem. Before applying gas to the EDU input, it is preliminarily mixed with fractions of light hydrocarbons, for example, oil, gas condensate or associated petroleum gas having an increased concentration of hydrocarbons of fractions C _{2 + higher.} moreover, the mixing is carried out using an ejector operating by using the energy of a gas stream of a high-pressure gas reservoir.

Novelty. The specified ejector is installed in a gas well above the roof of a high-pressure gas reservoir, which is a source of energy that feeds the gas ejector. As a result of the displacement at the bottom of a gas well of a high-pressure formation gas with a low-pressure associated (oil) gas or a mixture of gas with liquid light hydrocarbons supplied from the wellhead, the concentration of C _{2 + higher} fractions increases _. at the outlet of the gas mixture from the lift pipes of the gas well and the EDU connected with them, the result of which is an additional increase in the concentration of fractions C _{2 + higher} at the exit from the EDU, and as a result, after the HCV passes through the treated oil reservoir, an additional increase in the coefficient of oil displacement by the gas-gas mixture; due to the use of a gas ejector installed at a depth in the trunk of a high-pressure gas well for mixing, the need for a compressor or other power plant is eliminated, energy resources are saved, and the costs of heating the ejector are eliminated.

Significant differences. In the prototype - RF patent No. 2060378 - in the ejector installed on the bottom of the well, the energy of the coolant flow supplied from the wellhead through the column of elevator pipes located in it is used. In the proposed method, mixing in a borehole ejector of high pressure gas having a low hydrocarbon content of fractions C _{2 + higher.} , with a stream introduced from the wellhead having a high content of these fractions, it is ensured by using the energy of a high-pressure formation gas at the bottom of the well, for which it is proposed to supply high-pressure gas from the gas reservoir opened by this well to the high-pressure chamber of the downhole ejector, and a low-pressure associated gas (oil ) gas or a mixture of low-pressure gas with light liquid hydrocarbons to be fed into the low-pressure chamber of this ejector along the annular (annular) space of the same well - between the walls and columns of casing and elevator pipes, and the resulting mixture, having passed through the mixing chamber in the ejector, after leaving the ejector, rises up the column of elevator pipes up to the mouth of the gas well. Thus, in the prototype and in the proposed technical solution, the column of elevator pipes is used for various purposes.

Positive effect. At the entrance to the low-pressure chamber of the gas ejector, an additional pressure is advantageously used, created by the weight of a column of associated (oil) gas or a mixture of low-pressure gas with light liquid hydrocarbons. This is ensured by the difference in the marks of the mouth of the gas well and the installation site of the gas ejector in the well, as a result of which the pressure of the low-pressure gas moving down the annular (annular) space of the gas well increases at the entrance to this ejector, and gas enters the high-pressure nozzle of the gas ejector with a pressure equal to the bottomhole in this well, which helps to improve the hydrodynamic conditions of ejection. In addition, the energy that is usually lost during the production of high-pressure gas is useful when regulating the technological mode of gas extraction from the wellhead using a nozzle, and the high temperature of the rock at the depth of the ejector installation eliminates the formation of hydrates in the cold season, which is possible when the ejector is installed on the surface.

The drawing shows a flow chart of the proposed method.

Description of the drawing: 1 - oil reservoir; 2 - lift pipe string in the injection well; 3 - injection well; 4 - ejection-dispersing device (EDU); 5 - gas ejector; 6 - column pipe elevator in a gas well; 7 - gas well: 8 - disconnector (packer); 9 - high-pressure gas reservoir; 10 - low-pressure chamber of a gas ejector; 11 - high-pressure nozzle of a gas ejector; 12 - gas pipeline; 13 - low pressure chamber EDU; 14 - high pressure nozzle EDU; 15 - pipe branch; 16 - locking device.

The implementation of the method. In the oil reservoir 1 through the pipe string 2 into the injection well 3, the water-gas mixture (HCV) is formed, which is formed in the EDU 4. At the inlet of the EDU 4, a mixture of hydrocarbon gases with a given increased concentration of C _{2 +} fractions _higher. and high pressure water. A mixture of hydrocarbon gases with a given concentration of fractions of C _{2 + supra is} obtained in a gas ejector 5 mounted on lift pipes 6 in a gas well 7 above a disconnector (packer) 8 located above the roof of a high-pressure gas reservoir 9; the low-pressure chamber 10 of the gas ejector 5 is in communication with the annular cavity above the disconnector (packer) 8, and the high-pressure nozzle 11 of the gas ejector 5 is connected with the annular cavity below the disconnector (packer) 5 and further with the high-pressure gas reservoir 9. Into the annular gas space 7 wellbore pressure P ₁ fed low pressure liquefied petroleum) gas (or mixture of low pressure gas to liquid hydrocarbons) at a flow rate Q ₁ that is moving downwards at a depth setting of the ejector has a pressure determined by f rmulami

where D ₁ , F ₁ , λ ₁ respectively hydraulic diameter, living area and coefficient of hydraulic resistance of the cavity of the annular (annular) space of a gas well;

H ₁ is the vertical distance from the mouth of the gas well to the entrance to the low-pressure chamber 10 of the gas ejector 5;

T ₁ , Z ₁ - respectively, the average temperature and supercompressibility coefficient of gas along the length of the cavity of the annular (annular) space of a gas well 7;

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

g is the acceleration of gravity;

D _VE , D _NL - respectively, the inner diameter of the production casing and the outer diameter of the elevator casing.

With a pressure of P ₂ associated (petroleum) gas enters the low pressure chamber 10 of the ejector 5.

At the high-pressure nozzle 11 of the ejector 5 from the gas reservoir 9, gas is supplied with a flow rate (flow rate) of Q ₂ and a pressure of P ₃ determined by the formula

$$P_3{}^2=P_{Plg}{}^2-A\cdot Q_2-B\cdot Q_2{}^2,(6)$$

where R _{PL g} - reservoir pressure in the gas reservoir 9;

A, B - filtration resistance coefficients for gas inflow into the well;

Q ₂ - flow rate of a gas well.

At the outlet of the gas ejector, the pressure of the gas mixture (P ₄ ) depends on the values of P ₂ , P ₃ , Q ₁ , Q ₂ , as well as on the dimensions of the main elements of the ejector and will be within $$P_2<P_{\mathrm{four}}<P_3.(7)$$

The pressure of the gas mixture at the wellhead, P ₅ , is determined by the formulas

where λ ₂ , D ₂ , F ₂ - respectively, the coefficient of hydraulic resistance, inner diameter, sectional area of the elevator column 6;

N ₂ is the vertical distance from the ejector 5 to the mouth of the gas well ;;

T ₂ , Z ₂ - respectively, the average temperature and the coefficient of supercompressibility of the gas along the length of the elevator column 6;

Q ₃ - consumption of a mixture of gases:

$$Q_3=Q_{\mathrm{one}}+Q_2.(\mathrm{eleven})$$

Next, the mixture of hydrocarbon gases through the pipeline 12 is sent to the low-pressure chamber 13 of the EDU 4, and to the high-pressure nozzle 14, a high-pressure water flow.

The water-gas mixture (HCV) obtained in the EDU is supplied to the injection well 3 and through the lift column 2 to the oil reservoir 1.

The regulation of the modes of supply of associated (oil) and high-pressure gas to the gas ejector 5 and water supply to the EDU 4 is carried out from the given conditions: the gas concentration in the water-gas mixture supplied to the well 3 and the bottomhole pressure in the injection well during the period of pumping the HCV into the oil reservoir 1. For of this, on the line of associated (oil) gas before it enters the annulus of the gas well 7 and on the line of the gas mixture at the outlet of the gas well, gas flow meters and manometers are installed. On the water supply line before entering the EDU, a flow meter and a manometer are installed. A pressure gauge is also installed at the outlet of the HCV from the EDU.

If it is necessary to introduce liquid hydrocarbons into the low-pressure gas stream, a branch 15 with a shut-off device 16 is provided on the low-pressure gas line.

In order to increase the efficiency of oil displacement from low-permeability rock, a removable dispersant (not shown in the drawing) is installed on the shoe of the lift pipe string 2 lowered into the injection well, and HCV injection into the formation 1 is carried out in a cyclic mode, changing the pressure at the outlet of the EDU for this ranging from a given maximum to a specified minimum value.

Claims (4)

1. A method of developing an oil reservoir, comprising supplying to the oil reservoir through an injection well a water-gas mixture prepared at the mouth of an injection well using a mixing device, feeding to the mixing device under water and gas pressure, characterized in that the gas stream before being fed to the mixing light hydrocarbon fractions, for example oil, gas condensate, associated petroleum gas or a mixture of low-pressure gas with hydrocarbon fractions C _{2 + higher} , are introduced using an ejector through an ejector; f high-pressure gas with a gas stream having an increased concentration of hydrocarbons of fractions C _{2 + higher} , is carried out using an ejector installed in a gas well on an elevator pipe string above the roof of a high-pressure gas reservoir, and the gas flow from a high-pressure gas reservoir in the annular annular space of the well is isolated using a disconnector - packer from a low-pressure gas stream and fed to the high-pressure nozzle of the ejector, while the low-pressure gas stream with a high content of fractions C _{2 + higher} supplied from the wellhead through the annular-annular space of a gas well, they direct it to the low-pressure chamber of this ejector. 2. The method according to claim 1, characterized in that a dispersing device is installed on the shoe of the column of elevator pipes lowered into the injection well. 3. The method according to claim 2, characterized in that the dispersing device on the shoe of the pipes lowered into the injection well is provided in a removable design. 4. The method according to any one of claims 1 to 3, characterized in that at the outlet of the mixing device installed at the mouth, the pressure is periodically changed in the range from a given maximum to a predetermined minimum value.

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