RU2246000C2 - Oil deposits extraction complex - Google Patents

Abstract

FIELD: oil and gas extractive industry.

SUBSTANCE: device has force and product pipelines, column of thermo-isolated pipes, steam generator. Steam generator is made in form of system for feeding easily-boiling liquid. Said system contains thermo-isolated force pipeline with reduction assembly for adjusting amount and pressure of easily-boiling liquid and sprayer. Sprayer serves for dispersing easily-boiling liquid on smallest drops and forming foam of mixture of bubbles of easily-boiling liquid steam and oil from bed. Also provided is compressor for raising foam, cooling machine for transferring steam of easily boiling liquid to liquid state. Inputting pipeline is placed coaxially outside the force pipeline. Output of input pipeline is connected to separator input, and separator output - to cooling machine input.

EFFECT: higher efficiency.

1 dwg

Description

The invention relates to the development of oil fields, in particular to complexes of steam exposure to a formation containing highly viscous oil.

The known complexes for the development of oil deposits by pumping coolant (hot water or steam) into the reservoir. Thermal methods of influence on oil reservoirs. Reference manual "bowels", 1995, p.82,

A known complex of steam injection through a column of insulated tubing, in which a heat-resistant packer is installed above the roof of the developed formation. The complex provides reduction of heat loss, protection of the casing from temperature differences. Steam generators with various parameters are used to act on the formation. Bourget J., Surio P., Combarnu M .: Thermal methods of enhanced oil recovery. Per. with french M .: Nedra, 1988, p. 193.

A well-known complex of development of oil deposits containing injection and intake pipelines, a string of tubing insulated pipes, a steam generator. Patent of the Russian Federation No. 2187630, IPC: Е 21 В 43/24, 2002, Bull. No. 23 (prototype).

A disadvantage of the known complexes for the development of oil deposits is the low coverage of the impact process along the section of the reservoir. In most cases, steam flows mainly into the upper part of the reservoir due to gravitational forces; the hydrostatic pressure of the liquid and oil column is not used.

This invention eliminates the disadvantages of analogues and prototype.

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 is achieved by the fact that in the complex of development of oil deposits containing intake and pressure pipelines, a tubing string of thermally insulated pipes, a steam generator, a steam generator is made in the form of a low-boiling liquid supply system containing a thermally insulated pressure pipeline with a pressure reducing unit for regulating the amount and pressure of low-boiling liquid and a nozzle for dispersing the boiling liquid into tiny drops and creating foam from a mixture of vapor bubbles of the boiling liquid and oil from the reservoir, a compressor for lifting the foam, a refrigeration unit for converting low-boiling liquid vapor to a liquid state, while the intake pipe is coaxially located outside the pressure pipe, the output of the intake pipe is connected to the inlet of the separator, and the output of the separator to the inlet of the refrigeration unit.

The invention is illustrated in the drawing. The drawing schematically shows a complex of oil production from wells, containing an intake pipe 1, a 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.

The oil production complex works as follows. A low-boiling liquid: liquid ammonia or carbon dioxide is fed to the bottom of the well through a heat-insulated pressure pipe 5 with a pressure reducing unit 6 and a nozzle 7 at the end through a nozzle 7. Liquid ammonia or carbon dioxide is supplied under a pressure sufficient to disperse the supplied liquid in the nozzle 7 into the smallest drops and create a foam from oil and bubbles of low boiling liquid. Further, the foam thus obtained rises up the well under the action of an external compressor (not shown in the drawing), as well as under the action of the saturated vapor pressure of the boiling liquid. The vapor of the liquid is separated by a separator 8 and served in the refrigeration unit 4, in which they are transferred into a liquid state and re-returned to the bottom of the well. The quantity and working pressure of low-boiling liquid are regulated by a reduction unit 7 to optimize the process in specific operating conditions.

Once at the bottom of the well, a low-boiling liquid passing through the nozzle 7 breaks into tiny drops (disperses) and evaporates, forming a bubbly foaming mixture. The density of this foam ρ _p can be reduced to a value 3-10 times lower than the density of pure oil. Therefore, with the pressure of the reservoir, external compressors and saturated vapor pressure equal to, for example, 10 atm, the foam rises to a height of 300-1000 m. This ensures its further evacuation from the well.

Under the influence of gravitational forces or forced 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 through pressure-controlled thermally insulated pipe 5 from the refrigeration unit 4 through the pressure-reducing piping 5. 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 of H ₁ , which is determined from the ratio:

H ₁ = H · (1 + ρ _neften / ρ _foam ).

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

Using as low-boiling liquid ammonia (whose boiling point _bp = -33 ° C (240K) at 1 atm, the heat of vaporization of r = 1500 kJ / kg), 1 kg of the evaporation of ammonia is born bubbles totaling 1.73 m ³ . 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, this 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 crucial. For ammonia, the 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 foam density 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 vapors 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 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 vapors of ammonia under normal conditions is ρ _am = 0.6 kg / m ³ , then 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 by taking the heat of condensation in the amount of: Q _chol = r _am · M _am = 1.5 (MJ / kg) · 0.06 (kg) = 90 (kJ) per second. Here r _am is the specific heat of vaporization of ammonia.

It should be noted that the evaporation of ammonia in the well leads to some 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 Δ Т = 6 ° С. The above estimates 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 pressures. 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 because in CO _{2 the} vapor pressure at a temperature of 20-30 ° C reaches a value of 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 oil production in this complex. 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 · (ρ of _{oil is} ρ of _vapor ) · 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. 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 complex of development of oil deposits containing injection and pressure pipelines, a tubing string of thermally insulated pipes, a steam generator, characterized in that the steam generator is made in the form of a low-boiling liquid supply system containing a thermally insulated pressure pipe with a pressure reducing unit for regulating the amount and pressure of low-boiling liquid and a nozzle for dispersing boiling liquid into tiny drops and creating foam from a mixture of vapor bubbles of boiling liquid and oil from the reservoir, a compressor for lifting foam, a refrigeration unit for converting low-boiling liquid vapor into a liquid state, while the intake pipe is coaxially located outside the pressure pipe, the outlet of the intake pipe is connected to the inlet of the separator, and the outlet of the separator to the inlet of the refrigeration unit.