RU2245999C2 - Gravitational steam-power oil extraction method - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: method includes inputting working environment under pressure along thermo-isolated pipeline into oil-bearing bed and extracting oil to the surface through inputting pipeline. As working environment easily-boiling liquid is used. It is fed along force thermo-isolated pipeline with reduction assembly and sprayer at end. Easily-boiling liquid is fed under pressure, enough for dispersing easily-boiling liquid on smallest drops and forming a foam of bubbles of easily-boiling liquid and oil from bed. It is fed into inputting pipeline placed coaxially outside force pipeline. Mixture of steam of easily-boiling liquid and oil is extracted to surface. Mixture is separated, oil is gathered, and steam of liquid is condensed for repeated use in well.

EFFECT: higher efficiency.

1 dwg

Description

The invention relates to the oil industry and is intended for transportation through the pipeline of a gas-liquid mixture of the production of oil wells.

A known method of oil production from wells with pressure and intake pipelines into which oil is pumped using a pump. USSR copyright certificate No. 1384871, IPC: F 17 D 1/12, 1988

The disadvantage of this method is the low productivity, because during the stop of the pump, the supply of well products to the pressure pipe is not carried out.

A known method of oil production from wells with pressure and intake pipelines, in which a working medium is introduced into the pressure pipe using a compressor. The gas-liquid mixture allows you to increase the transportation distance from the wells to the final collection point, but only for shallow and rich fields. Patent of the Russian Federation No. 2029074, IPC: E 21 B 43 / 00.1995

There is a known gravitational steam-powered method of oil production from wells by pressure and intake pipelines, in which a pressure medium is introduced into the oil layer through a pressure-insulated pressure pipe and oil is extracted to the surface through the intake pipe. Patent of the Russian Federation No. 2117756, Е 21 В 43/24, 1998 (Prototype).

The disadvantage of this method is the decrease in injectivity and the rate of injection of steam during its injection into injection wells. This is due to the fact that during the period of steam injection, no fluid is taken from the formation, as a result of which, as the pore space of the formation is filled with steam, the reservoir pressure increases in the region of the bottom-hole zones of injection wells. A decrease in the rate of steam injection leads to a decrease in the rate of heating of the reservoir and an increase in the time for its development. Another disadvantage of this method is that during the oil extraction period, the main process is the gravitational flow of oil, the speed of which is low, and hydrodynamic displacement is not used. This leads to a decrease in the rate of oil extraction.

The objective of the present invention is to increase the efficiency of field development by increasing the rate of oil extraction from it by regulating the modes of steam injection and oil selection taking into account changes in the thermodynamic state of the formation.

The technical result of the invention is to increase the efficiency of using gravitational oil outflow and its hydrodynamic outflow due to steam-force impact on the reservoir containing highly viscous oil.

The technical result of the invention is achieved by the fact that in the method of oil production from wells with pressure and intake pipelines, in which a pressure-sensitive heat-insulated pipeline is introduced into the oil-bearing layer under pressure and oil is extracted to the surface through the intake pipe, low-boiling liquid is used as the working medium, it is fed through a heat-insulated pressure pipe, with a pressure reducing unit and nozzle at the end, at a pressure sufficient to disperse the low-boiling liquid finely These drops and the creation of foam arising from bubbles of low boiling liquid and oil from the reservoir, which is fed into the intake pipe located coaxially outside the pressure line, are removed to the surface in the form of a mixture of a pair of low boiling liquid and oil, the mixture is separated, oil is collected, and the vapor of low boiling liquid condensed for reuse in the well.

The method consists in the fact that a low-boiling liquid, for example liquid ammonia or carbon dioxide, is fed through a nozzle to the bottom of a well through a heat-insulated pipeline with a pressure reducing unit and a nozzle at the end. The low boiling liquid is supplied at a pressure sufficient to disperse the supplied liquid in the nozzle into the smallest drops and create a foaming mixture of oil and bubbles of low boiling liquid.

Thus obtained foam rises up the well under the action of an external compressor, as well as the saturated vapor pressure of the boiling liquid. The liquid vapor is separated by a separator and fed to the refrigeration unit, in which they are transferred to the liquid state and returned to the bottom of the well. The amount and working pressure of the liquid are adjusted to optimize the process in specific operating conditions.

Once at the bottom of the well, a boiling liquid passing through the nozzle breaks up into tiny drops (disperses) and evaporates, forming a bubble vapor-oil mixture (foam). The density of this foam ρ _p can be reduced to a value 3-10 times lower than the density of pure oil. Therefore, at reservoir pressure, compressors and saturated vapor pressure equal to, for example, 10 atm, oil foam rises to a height of 300-1000 m. This ensures its further evacuation from the well.

The drawing schematically shows a complex of oil production from wells. The oil production complex contains an intake pipe 1, a pumping pump 2, a compressor 3, a refrigeration unit 4, a heat-insulated pressure pipe 5, a pressure reducing unit 6, a nozzle 7, a separator, 8, a connecting pipe 9 and a starting device 10.

Under the influence of gravitational forces or forcedly increased pressure in the oil reservoir, the oil in the well rises to a certain level H above the bottom of the well, covering nozzle 7. Into nozzle 7, a low-boiling liquid is supplied via pressure-insulated pipe 5 from the refrigeration unit 4 through a pressure-insulated pipe 5 from the refrigeration unit 4. Once in nozzle 7, it is sprayed, vaporized and, mixed with oil, turns into foam, whose density ρ _p is many times lower than the density of oil. The resulting foam according to the law of Archimedes and under the influence of gravity rises through the collection pipe up to a new level H ₁ , which is determined from the ratio:

H ₁ = H * (1 + ρ _oil / ρ _foam ).

Oil from the rising foam is selected by the pump 2, and the steam is separated by a separator 8 and returned through the connecting pipe 9 to the refrigeration unit 4. The entire system is put into operation by the starting device 10.

When using ammonia, in which T _bale = -33 ° C (240 ° K) at a pressure of 1 atm, the heat of vaporization is r = 1500 kJ / kg, during the evaporation of 1 kg, bubbles of 1.73 m ^{3 are} generated.

When this volume is mixed with 1 m ^{3 of} oil, a foam is formed with a volume of 2.73 m ³ weighing 10 ³ kg and a foam density ρ _p = 370 kg / m ³ .

At an overpressure of 10 atm, the foam rises to a level of 300 m. If the overpressure is low, then the additional pressure drop in the well due to saturated vapor pressure becomes decisive. For ammonia, the saturated vapor pressure at a temperature of + 20- + 30 ° C is 10-15 atm, respectively. Therefore, the height of the foam will be determined precisely by the pressure of saturated vapor.

To calculate a specific system for pumping oil from a well 1 km deep, we assume that the volume of bubbles in the foam is 10 times greater than the volume of oil. Then the density of the foam ρ _p will be 10 times lower than the density of oil ρ _n . For definiteness, we take ρ _n = 800 kg / m ³ and ρ _p = 80 kg / m ³ . If we take the pressure of saturated vapor of ammonia P = 8 * 10 ⁵ Pa (8 atm), then the foam will completely fill the well with a depth of 1 km.

For clarity, it is convenient to take the cross-sectional area of the well S = 0.1 m ² , and the foam outflow velocity from the well v _p = 1 m / s. In 1 second, gas with a volume of V _g = 0.1 m ³ and oil with a volume of V _n = 0.01 m ³ or a mass of M _n = 8 kg will leave the well.

If we assume that the density of saturated ammonia vapors under normal conditions is ρ _am = 0.6 kg / m ³ , the mass of the released gas will be M _am = 0.06 kg. To create a continuous process of pumping oil with a capacity of P = 8 kg / s, it is necessary to pump just such an amount of liquid ammonia using a refrigeration unit, that is, 0.06 kg / s. To condense the vapors, it is necessary to cool them, taking the heat of condensation in the amount of:

Q _hol = r _am * M _am = 1.5 (MJ / kg) * 0.06 (kg) = 90 (kJ) per second,

r _am - specific heat of vaporization of ammonia.

It should be noted that the evaporation of ammonia in the well leads to cooling of the oil. However, this cooling is relatively small. The heat capacity of oil is 2 kJ / kg * K, respectively, 8 kg of oil transfer heat to ammonia 16 kJ / K. Since ammonia takes ~ 100 kJ / s from oil, the oil is cooled at ΔТ = 6 ° С. If the density of the foam is 2-3 times higher, then ΔT does not exceed 3 ° C. The estimates given are approximate. It is necessary to take into account the change in the volume and number of bubbles along the depth of the well due to changes in hydrostatic and gas-dynamic pressure. In particular, when the pressure changes from 1 atm on the surface of the oil layer to 10 atm at the bottom of the well (oil layer thickness), the volume of bubbles decreases by 10 times. Therefore, the average value of the volume of bubbles over the entire thickness of the layer will be 0.5-0.6 of the maximum value. As a result, the rise of the foam will not be 1000 m, but 500-600 m, when considering only the static regime without taking into account the appearance of new bubbles, their movement and the work of the gas-dynamic vapor pressure inside the bubbles when rising.

In addition, the reservoir can produce oil in an amount of more or less than 8 kg, which is accepted in the assessment. Therefore, the volume of bubbles and the amount of supplied working medium must be changed due to the reduced supply of ammonia into the well.

The second example of oil production is based on the use of carbon dioxide as a working fluid. It is attractive in that in CO _{2 the} vapor pressure at a temperature of 20-30 ° C reaches 40-50 atm. This allows the production of highly viscous oil from any depth. However, the above remarks on the effect of hydrostatic pressure, as well as the need for deeper cooling of the working fluid (T _boil = -76 ° C) require calculations of the possibility of its practical use for specific fields.

The most important point is the physical basis of the method of oil production. As soon as a bubble of volume V ₀ was born in a liquid (oil), the buoyancy force of Archimedes acts on it:

F = V ₀ * ( _oil ρ -ρ _steam ) * g, where g is the acceleration of gravity.

The presence of this force, caused by the action of the force of gravity, allows you to create foam throughout the depth of the well. And the work of this force, taking into account the work of the working fluid vapor during expansion, is ultimately aimed at increasing the difference between the pressure of the surrounding oil reservoirs and the pressure at the bottom of the well. According to the law of communicating vessels, oil constantly fills the annulus of pressure 5 and intake pipelines 1.

Claims (1)

A method of oil production from wells with pressure and intake pipelines, in which a pressure-sensitive heat-insulated pipeline is used to inject a working medium into the oil layer and to extract oil to the surface through a sampling pipeline, characterized in that low-boiling liquid is used as a working medium, and it is supplied through a pressure head heat-insulated pipeline with a pressure reducing unit and nozzle at the end under pressure sufficient to disperse the boiling liquid into tiny drops and create bubble foam in low-boiling fluid and oil from the reservoir, which is fed into the intake pipe coaxially outside the pressure head and is removed to the surface as a mixture of a pair of low-boiling liquid and oil, the mixture is separated, oil is collected, and the low-boiling liquid vapor is condensed for reuse in the well.