RU2193910C1 - Method of gathering and treatment of oil and gas wells products - Google Patents

Abstract

FIELD: oil producing industry. SUBSTANCE: method includes multistage degassing of gas-oil mixture with supply of gas from gas well through heat exchanger to pipeline of gathering of oil wells products prior to entering into the first stage separator. In this case, created in pipeline are plug-emulsion or film dispersed conditions of gas-oil mixture flow. After separation from mixture gas is compressed and cooled with cold produced by throttling the gas of gas well. EFFECT: higher degree of recovery of hydrocarbon components from natural gas for increasing the amount of stock-tank oil and improvement of its quality. 2 dwg, 2 tbl

Description

 The invention relates to the oil industry and can be used in field preparation of crude oil, in particular in oil fields having extensive gas caps from which natural gas is taken.

 There is a method of preparing crude oil, used in the Baronyan-Vezirov well production system, which provides for the stepwise separation of oil for high and low pressure wells, compression of the separated low-pressure gas and its supply to a gas processing plant (GPP) or gas lift wells [1].

 The disadvantage of this method is the large ablation with a separated gas of light oil fractions.

 There is also known a method for the preparation of crude oil, including multi-stage separation of oil by several streams and consisting in the fact that the compressed gas of one stream is fed to the separation stages of other streams [2].

The disadvantage of this method is the low degree of extraction from gas and conversion into oil of valuable hydrocarbon components C ₃ , C ₄ , C ₅ , C _{6 + c} (propane, butane, pentane, hexane + higher), which are the raw material for the production of marketable products in the future oil refining (propane-butane fraction, stable condensate, gasolines, etc.), as well as high material and energy costs associated with gas compression.

 The objective of the invention is to increase the degree of extraction from natural gas and the transfer into the liquid phase of hydrocarbon components, providing an increase in the yield of salable oil and improving its quality, as well as reducing material and energy costs.

 The problem is solved in that in a method for collecting and preparing oil and gas well products, including multi-stage degassing of a gas-oil mixture with compression of the separated gas, according to the invention, gas from a gas well is throttled, after which it is introduced through a heat exchanger into a pipeline for collecting oil wells before entering in the separator of the first stage, while in the pipeline create a cork-emulsion or film-dispersed flow regime of the gas-oil mixture.

The gas supply from the gas well and its throttling in front of the heat exchanger mounted on the compressor discharge provides deep cooling of the compressed separated gas, due to which a significant amount of liquid hydrocarbons is released from it, which are supplied to the oil. This eliminates the need for the construction of special propane refrigeration units and eliminates additional energy costs for their operation, since cooling is carried out due to the energy of the compressed formation gas. The supply of gas from a gas cap, enriched with valuable hydrocarbon fractions (C ₃ -C _{6 + c} ), to the oil well production pipeline with maintaining a certain hydrodynamic regime ensuring the achievement of phase equilibrium between gas and oil, leads to the transfer from gas to oil with their direct contact with the hydrocarbon components C ₃ -C _{6 +} B, increasing the volume and quality of marketable oil.

Figure 1 presents the technological scheme of the method;
figure 2 shows a graph of the dependence of the increase in oil yield on the amount of gas supplied to the gas cap.

 The technological scheme includes an oil well 1, a gas well 2, an injection well 3, a pipeline for collecting oil wells 4, a separator of the first stage 5, a separator of the second stage 6, a separator of the third stage 7, a pipeline of a gas well 8, a gas pipeline of a separator of the first stage 9, a gas pipeline of a separator second stage 10, gas pipeline of the separator of the third stage 11, condensate nipple 12, oil pump 13, gas nipple 14, compressor station 15, heat exchanger 16, pipeline for supplying gas to oil wells 17, gas condensate separator 18, a pipeline for supplying condensate to a consumer 19, a pipeline for supplying condensate to an oil 20, a pipeline for supplying gas to a consumer 21, a pipeline for supplying gas to a formation 22, a booster compressor station 23, a gas reservoir 24, an oil reservoir 25.

 The method is implemented as follows.

 The production of oil wells 1 through a collection pipe 4 enters sequentially in the separators of the first 5, second 6, third 7 stages of separation. The gas degassed by pump 13 is pumped to an oil stabilization unit to obtain the target products in the form of a propane-butane fraction and stable gas condensate or to an oil refinery to produce propane-butane fractions, gasoline, diesel fuel, heating oil, etc.

 The separated gas from all stages of separation through gas pipelines 9, 10 and 11 is fed to the inlet of the compressor station 15. After compression and cooling in the heat exchanger 16, the separated gas is supplied to the gas condensate separator 18, in which gas condensate formed as a result of compression and cooling is released. The condensate that has separated out through a pipe 20 through a nozzle 12 is fed into the inlet pipe of a third stage separator 7 or (and) is sent to a consumer through a pipe 19. Compressed and separated from the condensate "dry" gas is supplied through the pipeline 21 to the consumer (thermal power station, state district power station) or (and) through the pipeline 22 is sent to the booster compressor station 23 and then is pumped through the injection well 3 into the upper part of the gas reservoir 24.

At the boundary of the gas 24 and oil 25 deposits, natural gas enriched in propane-butane and gasoline fractions is taken through a gas well 2. This gas rises to the surface under high pressure (10-15 MPa or more). At fitting 14, natural gas is throttled. Due to a sharp decrease in pressure (from 10-15 MPa to 0.6-0.8 MPa), natural gas is cooled to a negative temperature (to minus 30-40 ^o C). The cooled natural gas is fed into the annular space of the heat exchanger 16, in which the separated gas heated up as a result of compression at the compressor station 15 is directed into the annular space. A variant is possible when the cooled natural gas is supplied into the in-pipe space, and the separated gas heated up as a result of compression is sent to the annular space of the heat exchanger. The cooling of the separated and compressed gas in the heat exchanger contributes to a more complete extraction of heavy components (C ₃ -C _{6 + c} ) from it, which can be sent to the consumer in the form of condensate or added to oil. It does not require additional capital and energy costs for cooling the separated gas, for example, using propane refrigeration units, since the reservoir energy of compressed natural gas is used for this.

After the heat exchanger 16, natural gas, heated to positive temperatures (plus 10-15 ^o C), is fed into the pipeline for collecting oil wells 4 at a calculated distance L from the entrance to the separator of the first stage 5. The distance from the gas supply point to the entrance to the separator of the first the stages and flow regime of the gas-oil mixture are selected so that the most complete mass transfer between natural gas and oil is realized.

 Effective mass transfer is obtained during cork-emulsion or film-dispersed flow regimes of the gas-oil mixture in the pipeline, i.e., when they are intensively mixed together. These flow regimes correspond to the speed of the gas-oil mixture in the range from 4 to 10 m / s at a gas flow rate (ratio of gas flow to total gas-oil mixture flow in the pipeline) from 0.4 to 0.98 in pipelines with a diameter of 0.3-0.5 m

Based on the data of an experimental study of the mass transfer process, the time of joint movement of oil and gas in the pipeline should be at least 1 minute. Thus, the estimated distance L from the point of gas supply to the pipeline to the entrance of the gas-oil mixture into the first stage separator for these conditions will be
- at a gas-oil mixture speed of 4 m / s L = 4 m / s • 60 s = 240 m;
- at a gas-oil mixture speed of 10 m / s L = 10 m / s • 60 s = 600 m.

Under the above conditions, the most valuable fractions (C ₃ -C _{6 + c} ) pass from natural gas to reservoir oil, which, upon further degassing due to the effect of multi-stage separation, remain in the commercial oil, increasing its gasoline potential.

 The closed cycle of extraction of natural gas enriched in propane-butane and gasoline fractions from the bottom of the gas reservoir and injection of stripped gas to the top of the gas reservoir allows the use of huge resources of hydrocarbon feedstocks that are not used at all in some cases (gas wells are in conservation), or flared (for example, in the case of a gas breakthrough into the production casing of an oil well and the absence of a gas consumer). The technological effectiveness of the method is evaluated as follows.

Based on the equations of the phase state using equilibrium constants, a program for calculating on a PC a process of stepwise oil separation has been compiled. As an example, below are the calculation results for the Gubkinskoye field, formation BP ₉ , Rosneft-Purneftegaz OJSC. The three-stage separation of reservoir oil without the supply of natural gas of a gas cap at pressure and temperature at the separation stages, respectively, is taken as the basic version: 1 stage P ₁ = 0.8 MPa, T ₁ = 20 ^o С; 2 stage P ₂ = 0.35 MPa, T _{2 =} 40 ^o C; 3 stage P ₃ = 0.105 MPa, T ₃ = 40 ^o C.

In the proposed solution, the separation of reservoir oil is carried out with the supply of a different amount of gas of the gas cap Qg = 300, 600, 900 m ³ per 1 ton of oil at the same pressure and temperature at the separation stages.

 The initial component compositions of reservoir oil and gas cap gas are given in table 1.

The calculation results are illustrated by the graph shown in figure 2, from which it can be seen that the increase in the output of salable oil is directly proportional to the amount of gas cap supplied to the formation oil. With a gas quantity of 900 m ³ / t, the increase is 34%.

The increase in the yield of salable oil was obtained due to the conversion of components C ₃ -C _{6 +} b to oil (table 2), which are the feedstock for the desired products (propane-butane fraction, stable condensate, gasoline, diesel fuel) during further oil refining.

Thus, the proposed method for collecting and preparing oil and gas well products can significantly increase the quantity and quality of salable oil by extracting hydrocarbon fractions C ₃ -C _{6 + c} from natural gas and converting them to oil, as well as reducing material and energy costs due to the use of reservoir energy of compressed gas.

Sources of information
1. Marinin NS, Savvateev Yu. N. Gas degassing and preliminary dehydration in collection systems. M., "Nedra", 1982, p. 5-6.

 2. A. S. USSR 923567, class. - 01 D 19/00, 1982 Prototype.

Claims (1)

 A method of collecting and preparing oil and gas well products, including multi-stage degassing of the gas-oil mixture with compression of the separated gas, characterized in that the gas from the gas well is throttled, after which it is introduced through the heat exchanger into the oil production pipe before entering the first stage separator, while in the pipeline create a cork-emulsion or film-dispersed flow regime of the gas-oil mixture.

Images