Preliminary water discharge units are designed for oil degassing, oil-well gas extraction and treating and oilfield water discharge under excessive pressure.
The unit structure is based on the design of oil-n-gas separator with water discharge feature. This is a horizontal vessel equipped with processing nipples and connections for instrumentation.
Internals are: intake section, steadying baffle, coalescence section, knockout drum for gas treating and oil collector.
To provide better separation of oil-n-gas mixture a pulsation bottle is mounted at the inlet to separator; it provides bypass of gas extracted as well as the layer intake of water-oil emulsion and discharged water by the way of separate streams according to their density to the middle and bottom sections of the vessel respectively.
Technical data
| Parameters: | UPSV-500 | UPSV-1000 | UPSV-3000 | UPSV-10000 | ||
| Fluid capacity, t/day, max. |
500 | 1000 | 3000 | 10000 | ||
| Working pressure, MPa (kgf/cm2) |
0,6(6,0);1,0(10,0);1,6(16,0) | |||||
| Emulsion heating | Without heating (for light crude) with built-in heater (for middle crude) with free-standing heater (for heavy crude) |
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| Oil emulsion watering at inlet, % mass., max. | 90 | |||||
| Oil emulsion watering at outlet, % mass., within the range | 5 – 10 (for light crude of density up to 850 kg/m3,approximate expo-sure time up to 20 minutes) 5 – 15 (for middle crude, density: 850-870 kg/m3,approximate expo-sure time up to 40 minutes) 10 – 20 (for heavy crude, density: 870-895 kg/m3,approximate expo-sure time up to 60 minutes) |
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| Oil concentration in outlet water, % mass. | As per customer’s requirements |
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| Outlet concentration of mechanical impurities, % mass. | As per customer’s requirements | |||||
| Vessel capacity, m3 | 25 | 50 | 100 | 200 | ||
Operation
From pulsation bottle gas is fed to the unit through the gas intake connection; then it goes through steadying baffle and coalescence section, where it is separated from liquid. The final gas treating takes place in knockout drum. Water with minor oil content is fed from pulsation bottle to the bottom section inlet. There water is finally separated from oil, it is collected and discharged by the way of water drain connection.
Oil with minor content of gas and water is fed to intake section, where it smoothly spreads over top level of liquid phase. Being non-mixed with water, it goes through steadying baffle to the coalescence section, where residuals of gas and water are removed; then it comes to oil collector and took out of the unit.
Depending on properties of oil-water-gas mixture, the UPSV unit is allowed for supply without pulsation bottle.
In cooperation with Siberian Research Institute, we had developed the preliminary water discharge unit for operation in climate conditions of the West-Siberian area.
The scheme of manufacturing is based on the UPSV-2000 production; the structure of equipment is modified accord-ing to the customer’s requirements.
Besides of the main unit there the following auxiliary equipment is used:
– reagent module with metering pumps, capacity up to 10 l/h,
– piping,
– shutoff valves,
– control elements,
– safety system,
– cables, etc.
Our specialists select the appropriate instrumentation according to the customer’s requirements.
Description of the UPSV technology and equipment package for use in West-Siberian regions
The UPSV technology is based on the survey provided by the SibNIINP for solution of preliminary water discharge at West-Siberian oilfields in gas-saturated state at natural temperature of crude oil. According to the information ob-tained the natural temperature of raw material during the year changes between + 24 and 37 degrees Celsius. If us-ing demulsifier is good for preliminary separation of emulsified oil. If with increase of watering crude oil temperature raises as well, the application of heaters at UPSV unit becomes senseless. It increases safety and faultiness of op-eration and reduces maintenance and operating costs. Besides that is solves the problem of scale due to the heating of highly watered emulsions.
There is no problem with scale that usually occurs at heating of highly watered emulsions. Water phase contains salt-forming ions (calcium, bicarbonate), that is typical for waters of West-Siberian area.
Water can be preliminarily discharged to the booster pump station or to the CPF. Oil is processed at CPF after com-plete degassing and has some advantages.
There are two ways of water discharge in gas-saturated state to the booster pump station:
- Separation of gas, oil and water phases takes place in three-phase separator only. It is used if there are no high requirements to the quality of discharged water, oil and gas and at low capacity of the unit (max. 10 000 m3/day);
- Phase separation takes place by stages in different systems. First, the free gas is separated in separator, and then the fluid is forwarded to the precipitator, where oil and water phases are separated. This method allows producing oil with water concentration at max. 5%, and water with oil products concentration of 30–50 mg/l, at the capacity of 10 000 m3/day and more.
To improve operation effectiveness of the unit it is considered to engage the special technology of demulsifying agents, providing a crude oil treatment, where water concentration exceeds 60 %, i.e. an emulsion of “oil-in-water” type.
The essence of demulsifier metering method is as follows:
- after mud pump discharge to calculation unit the part of oil is returned via separate pipeline to the gas-fluid flow;
- demulsifier is metered by the way of metering pump of chemical feeding plant;
- demulsifier dissolves in the returned oil flow and comes to the crude oil as a solution.
An advantage of the above-mentioned technology of demulsifier metering is that feeding of diluted solution if com-pared to concentrated solution feeding allows to provide its fast distribution and effect.
Thus, the process flow of the UPSV has the following advantages:
– Use of existing processing and auxiliary equipment allows to decrease costs of equipment and con-struction;
–the process takes place at natural temperature of crude oil without use of heaters, this increases safety and faultiness of the UPSV unit, decreases maintenance and scale problems;
– separation of oil and water in unsaturated condition at first-stage pressure due to presence of gas dis-solved in oil reduces its density and viscosity, allows to increase a speed of phase separation and qual-ity of produced oil and water;
– phased separation of gas-fluid mixture provides better and proper separation of phases: gas, oil and water;
–use of special technology for demulsifier metering at the unit’s inlet provides complete use of reagent and avoids it from coming to water phase. This is especially important for highly-watered oils, that re-quires separation of emulsion with 60% water content and higher, i.e. the emulsion of “oil-in-water” type;
– there are no long sections of high differential pressure and pumps are not used in the system; this re-moves over-dispersion of processed emulsion and thus provides fast and perfect phase separation; specific coalescence and disperse particles sections in precipitators, made of stainless steel, improve quality of separation of oil and water;
– control system provides automatic control of set operation mode as well as warning and emergency alarm, emergency protection system, automatic event log system.
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Technical Data
| Capacity: m3/day (m3/hour) | 10000 - 15000(416,6 - 625) |
| Liquid residence time, min. |
37,2 - 46,8 |
| Horizontal speed of liquid in coalescence unit, m/s |
1,09 õ 10-2 |
| Water droplets settling time in oil layer in coalescence section in calculated gap between sheets, diameter | d 200 µm – 2,45 min. d 150 µm – 4,35 min. d 100 µm – 9,87 min. |
| Water droplets diameter in oil layer | d 200 µm and larger - 100% d 50 µm -46% |
| Time of ascend of oil droplets in water layer of coalescence section in calculated gap between sheets, diameter: | d 100 µm - 1,1 min. d 50 µm - 4 3 min. d 25 µm - 17,5 min. |
| Oil droplet diameter in water layer |
d 25 µm and larger - 100% d 10 µm -17% |
| Weight of the unit - 1 pcs./200 m3 |
32 500 kg |
