SU1493280A1 - Method of preparing oil - Google Patents

Abstract

This invention relates to methods for treating petroleum and may be used in the petroleum industry. The aim of the invention is to increase the efficiency of extraction of gaseous components from oil, including hydrogen sulfide. The method consists in supplying gas through pipeline 6 to the beginning of the vertical section of pipeline 5 before low-pressure separator 3. When oil is mixed with gas in pipeline 5, desorption of light hydrocarbon components and hydrogen sulfide occurs, resulting in a more stable commercial oil, with a lower content of hydrogen sulfide. The oil is mixed with gas in an upward gas-liquid flow with a true volumetric gas content of the latter 3-30. Reaction time is determined by the formula K Τ = 0,112 + α ^{- °, 48e} / ^D. (0.888-Α ^- ° ^{, 48E} ), where Τ is the time of oil exposure with gas

K - empirical coefficient (K = 4.2-7.8)

D is the diameter of the stream

α - true volumetric gas content

e is the base of the natural logarithm. 1 hp ff, 1 tab., 3 ill.

Description

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The invention relates to the petroleum industry, in particular to the technology of field oil treatment, and can be used for the separation and purification of oil from hydrogen sulfide.

The purpose of the invention is to increase the efficiency of extracting gaseous components from oil, including hydrogen sulfide.

The method is carried out as follows.

A multi-stage separation of oil and gas supply are carried out for mixing with oil in an upward gaseous-liquid flow with a true gas content of oil of 3-30 and interaction time not less determined by the formula

, ° ai2.i..L,

   D (0.888 -o (-o, 49e)

where c is the time of interaction of oil with gas; K 4,2-7,8 - empirical coefficient

ficient)

D is the diameter of the flow (for smooth pipes the internal diameter of the pipeline); 0 - true volumetric gas soder

living;

e is the base of the natural logarithm.

Before mixing the oil with the gas, it is advisable to feed the reagent demulsifier into the oil,

In the preparation of flooded oil, the supply of the demulsifier reagent to the oil, prior to its mixing with the gas, intensifies the mass exchange by reducing the NIN viscosity and the surface tension coefficient of the oil and, consequently, increases the efficiency of the method

In technological pipelines of oil treatment plants with a true volumetric gas content of more than 3, the projectile mode of movement of the gas-liquid mixture prevails. In horizontal areas, it is characterized by the presence of relatively stable immiscible volumes of oil and gas. The efficiency of mass transfer in this case is low. The ascending flow of the sludge is characterized by intensive mixing of the phases. Moving up the fluid props constantly lose some liquid. The lagging liquid under the action of gravitational forces flows along the walls

tubes, which increases the time the gas contacts the liquid. At the point of collision of the trapped liquid, a vortex appears at the beginning of the next plug, which disperses the gas phase and draws it into the plug of the liquid phase. The same vortex promotes mixing the trapped liquid with the slug liquid.

Thus, increasing the efficiency of mass transfer and consequent degassing of oil in the ascending gas-liquid flow, as compared with the horizontal flow, is achieved by increasing the time of oil contact with gas and the specific interfacial surface during the projectile flow

The true volumetric gas content of a two-phase flow is understood as the ratio of the volume of the gas phase under given thermodynamic conditions to the volume of the liquid phase. This indicator is maintained within the prescribed limits by changing the amount of gas supplied to the pipeline before the stages of oil separation.

With a true volumetric gas content of less than 3, the projectile mode of movement of the gas-oil mixture turns into a bubble, which is accompanied by a decrease in the efficiency of mass transfer and, therefore, degassing of oil and purification from hydrogen sulfide.

The increase in the true volumetric gas content above 30 is impractical because it does not lead to a significant increase in the degree of extraction of gaseous components, I

Fig. 1 shows the structure of the projectile flow: horizontal a and upward 5; Fig. 2 shows the experimental dependence of the efficiency of extraction of gaseous components (I /) on the true volumetric gas content (o) for horizontal a and upstream S of two-phase FLOWS; Fig. 3 is a process flow diagram of an installation implementing the proposed method.

The technological scheme includes separators of high 1, medium 2 and low 3 pressure, installation 4 desulfurization and technological gas and oil pipelines. Separator 3 is mounted on a pedestal and connected to a vertical section of the inlet pipeline 5, the lower part of which

connected to a gas pipeline 6, which supplies the gas of the first separation stage; oil is withdrawn from the installation via line 7.

The dimensions of the vertical section of the pipeline are calculated as follows.

By the known values of the internal diameter D of the pipeline, the true volumetric gas content / (at a separation pressure of 0.105 MPa is assumed to be equal to the specific gas flow) and an empirical coefficient K (in the absence of experimental value of the coefficient K is assumed to be maximum - 7.8) The value of d is calculated as the ratio of the free volume of gas in the pipeline to the volume of oil at separation pressure (taking into account the intrinsic gas factor of the separated oil). The value of (the oil and gas performance with regard to the fluid delay in the pipeline calculates the length of the vertical section of the pipeline, ensuring the minimum interaction time f. In the case when the calculated length of the vertical section of the pipeline cannot be achieved in practice, the diameter of the pipeline increases and the calculation is repeated yut.

Example 1, Initial data: L 200 — plant capacity, D 0.5 MJ K 7.8, since the initial calculation was performed without preliminary experimental studies and, according to the description of the invention, the empirical coefficient is assumed to be equal to the maximum, e 2.72; s / 3 then

-0,8 2,71

, 7.8 - ° -I12-i-3 -, 0.5 (0.888 -) 8.4 s,

d 30

-0.4v. 1.71

78

 -0.4. 1.71.

0.5 (0.888 - 30) 2.2 s,

Then, based on the found value of the minimum required interaction time C, the value of about (, the plant performance and the diameter

pipeline calculate the minimum length of the vertical section of the pipeline N by the equation

n - 3600 biennium 52 l

where (l is the liquid delay in the vertical section of the pipeline compared to the time of the gas-liquid flow in an equal-sized section of the pipeline in the mode of ideal displacement.

Fluid retention takes place

due to the continuous flow part of the liquid from the upstream liquid plugs B, the plugs located below. The delay increases the residence time of the fluid in the pipeline.

The delay is calculated as the ratio of the gas content of the stream "/ to the relative length of the gas plug (l n / lfl) and is:

at / 3 1.7

c / oO / 3 5.3 when the value of the criterion F g is 0.01-0.1,

Then

H,

)

3600 -3.14-0.52 1.7

 5.6 m;

2gO 4j - | -30) 3.6 m. 3600-3.14-0.52-5.3

35

The method is carried out as follows.

Oil from the well goes through three stages of separation

 1-3, in the separator 3, it is degassed to atmospheric pressure and through line 7 is removed from the plant. Before the separator 3 of the third stage at the beginning of the vertical section of the pipeline

 5 through pipeline 6 into the oil serves

gas of the first stage of separation, purified from hydrogen sulphide in a desulfurization unit 4, sorption of light hydrocarbon components and hydrogen sulphide occurs in the pipeline when oil is mixed with gas. In the subsequent separation of the oil and gas mixture in the separator, commercial oil is produced with a reduced lung content.

55 hydrocarbon components and hydrogen sulfide.

A plausible confirmation of the possibility of achieving a positive effect only with the proposed value

volumetric gas content are the results of laboratory tests of the process on the model mixture shown in FIG. 2 (curve S). The logarithmic dependence of the degree of extraction of the gaseous component (if) on the gas content of the stream illustrates the high volatility of the process in the gas content interval of 0-3, in which the process efficiency varies more than 30 times. In this interval, the process practically cannot be implemented in the field preparation of oil, since maintaining constant efficiency with unavoidable changes in oil consumption coming from wells, becomes a difficult task and with the help of modern instrumentation and automation is simply impossible. From the graph should also.

that with a gas content of more than 30, the degree of extraction of the gaseous component is constant and does not depend on the value of the true volumetric gas content. Consequently, in this interval the process becomes non-refillable and, as a method, cannot be applied. A positive effect can be achieved only in the gas content interval 3-30, in which the process efficiency changes by a factor of 2, which, when changing the flow and thermodynamic parameters, makes it possible to maintain the required degree of component recovery by changing the flow rate of the feed gas, and, consequently, o (,

The table presents the results of industrial tests of the oil separation plant.

A comparative analysis of the results obtained for the depth of oil purification from hydrogen sulphide using known and proposed methods showed that when oil is mixed with gas in an upward gas-liquid flow, the efficiency of extracting gaseous components from oil can be increased by 27-33% compared to the option of mixing in a horizontal pipeline,

Claims (2)

1. A method of treating oil by means of its multi-stage separation, including supplying gas for mixing with oil in a low pressure separation stage, characterized in that, in order to increase the efficiency of extracting gaseous components from oil, including hydrogen sulfide. The oil is mixed with gas in an upward gas-liquid flow with a true volume gas content of oil of 3-30 and interaction time not less determined by the formula 0 ° ill2-l f, - D (0.888, "- vg) 0 where C is the time of interaction of oil with gas, K 4,2-7,8 - empirical coefficient; 5 D is the diameter of the stream с - true volumetric gas content e is the base of the natural logarithm. 0 2. A method according to claim 1, characterized in that a pegent demulsifier is fed into the oil before mixing the oil with gas.      -f f