JPS5853163B2 - Steam plant for offshore oil fields - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam plant that performs steam injection into an oil field, which is one method for improving the crude oil recovery rate in an offshore oil field.

The steam injection method can be used to great effect especially in oil fields that produce highly viscous oil (usually API degree 22 or less).

Since oil field boilers for this purpose are used as a type of hot water boiler, once-through boilers have been in practical use for some time.

Furthermore, when the steam temperature is 300° C. or lower, the fluidity of crude oil can be sufficiently increased and oil extraction can be facilitated.

However, one of the problems with this method is securing boiler water supply, and in particular, the biggest problem in offshore oil fields is how to economically secure a large amount of boiler water supply.

The present invention eliminates the above-mentioned bottlenecks in the steam injection method and provides a steam plant that enables maximum utilization of the steam injection method for offshore oil fields.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, a boiler 1 heats boiler feed water a supplied from a deaerator 2 by a feed water pump 3 to produce superheated steam.

The boiler fuel C used is natural gas or crude oil, which is produced extremely abundantly in ordinary oil fields 4, and is burned in the burner 5.

Reference numeral 6 denotes a steam desuperheater, in which superheated steam sent from the boiler 1 is cooled by seawater d injected through a seawater injection pump 7, turned into wet saturated steam e, and then injected into the oil field 4.

On the other hand, the superheated steam from the boiler 1 drives the main turbine 8 or the auxiliary turbine 9 to operate the respective generators 10, 11.

The exhaust steam f from both turbines 8 and 9 is sent to the condenser 12, where it is cooled and condensed by the cooling water (seawater) g that passes through it, and is again turned into boiler feed water a and sent to the water supply tank 13. stored.

Further, seawater d is pressurized and supplied to a reverse osmosis membrane type freshwater generation device 15 by a seawater pressure pump 14 to generate freshwater.

Due to the water quality, it is impossible to produce boiler feed water for this plant using only this reverse osmosis membrane water generation device 15.
The water is then supplied to a pure water device 16 using an ion exchange type or the like.

The produced water thus produced is sent to the water supply tank 13 and used as the boiler supply water 2.

The boiler water supply a in the water supply tank 13 is transferred to the transfer pump 17.
A part of the exhaust steam f is also sent to the deaerator 2.

This deaerator 2 is provided because the amount of dissolved oxygen in the produced water may be much greater in this method than in the evaporative freshwater generator.

Reference numeral 18 denotes an oil extraction pump, which is driven by the generator 10 to pump up the crude oil i.

j indicates exhaust, k indicates purge, and 19 to 27 each indicate a valve.

Next, its operation will be explained.

In the plant of the present invention, the steam injection process and the water production and oil extraction process are selected by valve operation. First, steam injection into the oil field 4 is performed for a certain period of time, for example, about 10 days, and then the nearby oil well or steam injection well is At the same time as the oil is extracted, water for water supply to the boiler is generated using the water supply device 15, etc., and the operation is performed by repeating these two types of processes.

FIG. 2 shows the steam injection process, at which time the valves 20, 21, 22 corresponding to the main turbine 8 and the valve 27 corresponding to the water generator 15 are closed, and the remaining valves 19, 23, 24 are closed.
, 25 and 26 are open.

Boiler feed water a supplied from the deaerator 2 via the feed water pump 3 is converted into superheated steam in the boiler 1, and the temperature of the superheated steam is reduced by injecting seawater d in the steam desuperheater 6. , is injected into the oil field 4 as wet saturated steam e.

Furthermore, a part of the superheated steam is supplied to the auxiliary turbine 9,
The generator 11 is operated.

Thereby, power for driving the water supply pump 3, seawater injection pump 7, transfer pump 17, boiler operation, etc. can be secured.

The reason why the auxiliary turbine 9 is provided is because if the main turbine 8 were used for both purposes, the steam injection process would require only a small amount of power, which would reduce the amount of steam and reduce the turbine efficiency, which would be disadvantageous. be.

The reason why the auxiliary turbine 9 is of the back pressure turbine type is because it is difficult to extract air due to the small capacity of the turbine, and it is advantageous to send a part of the turbine outlet steam to the deaerator 2.

FIG. 3 shows the water production and oil extraction process. At this time, valves 23, 24, 25 corresponding to the auxiliary turbine 9 and valves 19, 26 corresponding to the steam attemperator 6 are closed, and the remaining 20
, 21, 22, and 27 are open.

The crude oil i in the oil field 4 whose viscosity has been reduced by the wet saturated steam e injected in the previous step is extracted by the oil extraction pump 18 .

At the same time, the superheated steam generated in the boiler 1 drives the main turbine 8 and operates the generator 10.

Thereby, power for driving the water supply pump 3, seawater pressure pump 14, transfer pump 17, oil extraction pump 18, boiler operation, etc. can be secured.

Furthermore, part of the exhaust steam f from the main turbine 8 is sent to the deaerator 2 for heating, and the remaining majority is condensed in the condenser 12 and stored in the water supply tank 13, where it is returned to the boiler feed water a. used as.

In addition, the seawater d is pressurized and supplied to the reverse osmosis membrane water generation device 15 by the seawater pressurization pump 14 to produce water, which passes through the water purification device 16 to become produced water and is sent to the water supply tank 13. Used as boiler feed water a.

Equipment 1 to 270 shown in Figure 1 is installed on an oil drilling platform, but if a large capacity water tank 13 is required, it is better to float it on the sea instead of installing it on the platform. .

An example of calculation results regarding the plant of the present invention is shown below.

■ Assumption condition 0 Large amount of steam pressure to the oil field...22,800 kg
/hO steam pressure well inlet (desuperheater outlet) steam conditions -----
--100kg/Cr? LG, 80% dryness (3
10℃) 0 Feed water temperature (deaerator inlet)...20℃0 Seawater temperature...20℃0 Boiler steam condition (superheater outlet)...102
kg/c IILG x 520℃ 0 Boiler fuel...Natural gas (lower calorific value 8.
550 Kcal/Nm) 0 Boiler efficiency...90% (lower standard) o Thermal efficiency as a power plant...35% 0 Operating conditions of freshwater generator...30kg/crltG
X 20 'CO injection steam volume/recovered crude oil volume...
←Aishan□〈Rel 0 Oil extraction will be completed within a time equal to the steam injection period.

0 The boiler is always operated at the load at the time of steam injection.

■ Calculation result a Steam injection process 0 Required power: 160KW O boiler evaporation amount: 16.70 ok/h
(Including 500 kg/h of steam for driving the turbine.

)0 Amount of seawater injection for temperature reduction...6.600 K9
/hO Fuel consumption...-1.720 Nm'/hb
Water production and oil extraction process 0 Required power: 690KW (of which 490KW
KW is for water production and water purification equipment) 0 Boiler evaporation amount...16,700kg/hO
Fuel consumption: 1,720Nm'/hO Turbine generator end output: 5,970KW* Therefore, 5,970-690=5,280KW is used as power for various processing plants, etc. can.

Furthermore, in the case of the plant of the present invention, the purpose is not only to inject steam but also to drive a turbine, and the boiler is of a type that always generates superheated steam, so the boiler type does not need to be a once-through boiler.

As described above, the present invention has the following advantages.

(1) Seawater is injected into the steam desuperheater to reduce the temperature of superheated steam, so seawater can be efficiently evaporated and a large amount of wet saturated steam for injection into oil fields can be produced.

Furthermore, equipment such as boilers, turbines, and water pumps are not affected by seawater at all, so there is no need to take corrosion resistance into account, which is advantageous.

(2) Since the plant includes a water generation device, it is possible to inject wet saturated steam into offshore oil fields where it is difficult to obtain boiler supply water.

(3) There are conventional methods of treating seawater or oil field water (which has almost the same composition as seawater) and supplying it to boilers, but in this case, the water treatment equipment is extremely expensive (about the same price as the boiler), and it is not easy to operate. It was difficult to put it into practical use because of the high cost.

In the present invention, water produced by a water production device is used as boiler feed water instead of seawater, so conventional boiler water treatment is sufficient, and the water treatment device can be simplified, which is advantageous.

(4) The water produced by the water generator can be used for various purposes other than boiler supply water, as required by the platform.

(5) The boiler can always be operated with high efficiency and there is no waste in any of the steam injection processes, water permeation processes, and oil extraction processes.

(6) The power obtained by the turbine can be used for various purposes other than this plant, and no additional auxiliary power source is required.

In particular, during the water supply and recruitment process, various processing plants (oil and gas separation, oil-water separation, desalination, etc.) and oil pumps are installed on the platform to process the crude oil following oil extraction. This is extremely advantageous because the required power can be met by the turbine output.

(7) In water pumping and oil extraction processes that require a large amount of power, the turbine can be of the condensing turbine type because steam for water permeation is not required, and it has more power than a type that requires steam for fresh water production. This is advantageous because the efficiency of the plant can be much higher.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram showing an embodiment of the present invention, FIG. 2 is a system diagram for the steam injection process, and FIG. 3 is a system diagram for the water supply and oil extraction processes. 1... Boiler, 2... Deaerator, 4... Oil field, 6...
... Steam desuperheater, 8... Main turbine, 9... Auxiliary turbine, 10.11... Generator, 13... Water supply tank, 15... Reverse osmosis membrane type water generator, 16. ...Pure water device, a...Boiler feed water, b...Superheated steam, d...Seawater, e...Moist saturated steam.

Claims (1)

[Claims] 1. A boiler that generates superheated steam, a steam desuperheater that produces wet saturated steam for injection into oil fields by injecting seawater or the like into the superheated steam to reduce its temperature, and a turbine driven by the superheated steam, A steam plant for an offshore oil field characterized by having a reverse osmosis membrane water generation device for securing boiler feed water from pressurized seawater.