RU2318998C1 - Viscous oil and bitumen deposit development method - Google Patents

Abstract

FIELD: oil production, particularly enhanced recovery methods for obtaining hydrocarbons, namely using heat for viscous oil and bitumen production.

SUBSTANCE: method involves chemically and thermally treating deposit to be developed by obtaining vapor, oil and non-condensed gas mixture in tanks at well head. The mixture has pressure of 30-70 MPa. The mixture includes oil with viscosity not exceeding that of deposit to be developed. Non-condensed gases are nitrogen and carbon dioxide. The obtained mixture is left as it is for mixture cooling up to 147.13°C or lower temperature along with gas-oil mixture dilution. The mixture is injected in deposit to be developed via well in liquid state under gas saturation pressure, which is less or equal to deposit pressure.

EFFECT: increased deposit recovery due to oil viscosity reduction and reservoir energy increase due to dissolved gas drive provision in deposit.

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Description

The invention relates to the oil industry, in particular to methods for developing deposits of heavy oils or bitumen, and can be used in the production of viscous oils or bitumen by physico-chemical and thermal effects on the reservoir.

There is a method of developing massive oil deposits with fractured-porous-cavernous rocks by a stage-by-stage method (RF patent No. 1343914, IPC ЕВВ 43/22, published on 08/09/1995), according to which during the selection of reservoir fluids through production wells drilled for the next floor, through wells drilled to the upper floor, carbon dioxide is pumped along with oil. As a result of the dissolution of carbon dioxide in the reservoir oil at the first stage, the reservoir pressure increases, the volumetric coefficient of the reservoir oil, its gas content, saturation pressure increase and conditions are created for the resumption of operation of wells on the first floor.

There is a method of displacing oil from a massive type deposit (AS No. 1667432, IPC ЕВВ 43/22, publ. 10.12.1996), by which gas, for example, nitrogen, with a maximum miscibility pressure with oil, is pumped into the domed part of the formation. In the zone of advancing advancement of the displacement front, gas is injected (dry or fatty hydrocarbon gas or mixtures thereof) with a lower miscibility pressure with oil. In this case, the gas is pumped at a rate lower than the rate of nitrogen injection.

There is a method of increasing well productivity (RF patent No. 2235870, IPC ЕВВ 43/263, published on 09/10/2004) by thermogasochemical effect on the bottomhole zone of wells and increasing the mobility of the produced fluid, in particular viscous oil, due to its saturation with gas and heating.

A known method of producing viscous oil or bitumen from the reservoir (AS No. 834339, IPC ЕВВ 43/24, publ. BI No. 20, 1981), comprising heating the formation by pumping coolant and gas into it, while gas is subsequently heated to the next upload periodically.

The closest in technical essence and the achieved result to the proposed one is a method for producing viscous oil or bitumen from a formation (RF patent No. 2223398, IPC 7 ЕВВ 43/24, publ. 02/10/2004), adopted as the closest analogue for producing viscous oil or bitumen from the formation by physicochemical and thermal effects on the formation, by pumping coolant and gas into it. The gas used is a mixture of non-condensable gases generated during the combustion of liquid fuel, with the following ratio of components, wt.%: Nitrogen 15.2-19.0, carbon dioxide 4.8-6.0, while the gas content in the mixture with the coolant is 20-25 wt.%, and the mixture and steam are injected according to the amount of injected steam according to the empirical formula.

The disadvantage of this method is a small fraction of the solubility of non-condensable gases at existing pressures in the oil reservoir. Since in the presence of free gas in the formation, the steam-gas-thermal mixture breaks through to production wells, the result is reduced coverage of the thermal and physico-chemical effects on the formation over the area.

The technical result, the achievement of which the invention is directed, is to increase oil recovery by reducing the viscosity of the reservoir oil, and increasing the reservoir energy as a result of the formation of a dissolved gas regime in the reservoir.

The technical result is achieved by the fact that in the method for developing a reservoir of viscous oil and bitumen, including physicochemical and thermal effects on the developed formation, it is new that a gas-oil mixture in the single-phase state is pumped through the well in which the gas saturation pressure is less than or equal to reservoir pressure.

A single-phase gas-oil mixture is obtained by mixing under pressure of steam, a mixture of non-condensable gases - nitrogen and carbon dioxide, formed during the combustion of hydrocarbon or carbon fuels, as well as oil, whose viscosity does not exceed the viscosity of the developed field or less viscous.

The formation of a single-phase gas-oil mixture is carried out before injection into the developed formation in high pressure vessels at a pressure of from 30 to 70 MPa.

The drawing shows an example implementation of the method, where: 1 - installation of a gas and steam generator UMPG-10/16; 2 - pressure vessel (test pressure 100 MPa); 3 - discharge unit - AN-700; 4 - discharge line; 5 - valve; 6 - thermometer; 7 - manometer; 8 - injection well.

The method is as follows. We use UMPG-10/16 1 as a source of steam gas, where liquid fuel is burned, and the steam enters the high pressure vessel 2 located at the mouth of the injection well 8. When the pressure reaches 16 MPa, the valve 5 is closed and the gas is compressed in the vessel 8 until 70 MPa due to injection of oil by the injection unit - AN-700 3. Under the influence of high pressure from 30 to 70 MPa in the vessel 2 oil, a mixture of non-condensable gases (nitrogen and carbon dioxide) and steam mix rapidly and a single-phase (in liquid state) gas oil is formed a vapor mixture in which the gas saturation pressure is less than or equal to the reservoir pressure. A single-phase gas-oil-gas mixture in a liquid state, obtained by compressing steam, a mixture of non-condensable gases - nitrogen and carbon dioxide and oil, is left to cool to a temperature below 147.13 ° C (critical temperature of nitrogen gas) and then pumped through discharge line 4 into the discharge well 8.

The essence of the proposed method lies in the fact that the pressure of saturation of oil with gas and the pressure of solubility of gas in oil under certain conditions differ several times. That is, the pressure of gas solubility in oil is always higher than the pressure of saturation of oil with gas. At a pressure of 30 to 70 MPa in vessels where oil and gas-vapor mixture are mixed, a single-phase liquid is obtained that will have a gas saturation pressure of oil less than or equal to the average reservoir pressure for a given development period of the site, and during injection the injection pressure should be higher than the pressure saturation of gas-oil mixture. The gas is dissolved in oil during the cooling time of the gas-oil mixture to a temperature of 147.13 ° C and below.

The gas-oil mixture, falling into the oil-bearing formation, will move radially over the area of the oil-bearing formation, and as it moves away from the injection well, the mixture will expand due to the elasticity of the gas-oil-gas mixture and will be sprayed, mixing with the reservoir oil, since when dissolved in sections of the formation with lower pressure, the dissolved gas will tend to go into the gas phase. As a result of mixing the gas-oil mixture with the reservoir oil of the developed area, the viscosity of the reservoir oil decreases due to an increase in the dissolved gas in the oil and an increase in the temperature of the reservoir in the injection influence zone. As a result, the reservoir energy of the dissolved gas regime will increase, the hydraulic conductivity of the reservoir will increase, and therefore, the production rate of oil producing wells will increase.

An additional effect on the increase in oil recovery in comparison with thermal methods is a wider coverage of the oil-bearing formation in terms of area due to physicochemical effects.

The dependence of the saturation pressure on the composition and amount of gas being dissolved in the gas-oil mixture can be determined by the example of the reaction of diesel fuel combustion in the UMPG-10/16 steam and gas generator (maximum productivity 10 t / h of steam at a pressure of 16 MPa).

1 × C ₁₈ H ₃₆ + 27 × O ₂ + N ₂ = 18 × CO ₂ + 18H ₂ O + N ₂

When burning 1 kg (4 moles) of diesel fuel, we get 1.6 m ^{3 of} carbon dioxide, 10 m ^{3 of} nitrogen gas and 1.3 kg of fresh water. The saturation pressure of the gas-oil-thermal mixture will be found from approximate empirical dependencies. For example, according to the TatNII, the pressure of oil saturation with gas for the oils of Tatarstan and Bashkiria (with a gas factor of 2 to 40 m ³ / m ³ ) can be determined from the ratio:

P _H = 3.13 + (N ₂ C ₁ C _T ) * 10 ^-4 ,

where P _H is the saturation pressure in MPa; With _t gas factor m ³ / m ³ ; N ₂ C ₁ - the content of nitrogen and methane in gas in% (Reference book on oil production. Edited by Dr. Sc. K. Gimatudinova. M., "Nedra", 1974. p. 36.) So as methane is absent in the mixture, the formula is as follows:

P _H = 3,13 + (N ₂ C _T ) * 10 ^-4 , in this case, upon receipt of 10 m ³ N ₂ - P _H = 3,13+ (80С _T ) * 10 ^-4 .

Claims (1)

A method for developing a reservoir of viscous oil or bitumen, including physicochemical and thermal effects on the reservoir being developed, characterized in that a mixture of steam and oil with a viscosity not exceeding the viscosity of the developed reservoir is obtained at the wellhead in vessels with a pressure of 30 to 70 MPa, and non-condensable gases - nitrogen and carbon dioxide, the resulting mixture is left to cool to a temperature below 147.13 ° C with dissolution of the gas mixture in oil and in a single-phase - liquid state with a gas saturation pressure less than or equal to the reservoir The pressure is pumped through the hole in the target formation.