RU2325330C2 - Method of oilfield waters preparation for oilfield layer pressure support system and device for its implementation - Google Patents

Abstract

FIELD: oil production.

SUBSTANCE: oilfield waters are purified from sand grades by sedimentation, filtrated through magnetized granulated ferromagnetic material which forms closed magnetic circuit and is positioned in outer magnetic field, then coagulant is dosed and due to pressure drop the oilfield waters are floated with dissolved gas bubbles at that the floatation is carried out successively in several sections. The dissolved aggressive gases are evacuated by vacuum evaporation and bactericides are dosed. Magnetic separator is regularly flushed at deenergized magnetic field with water backflow. Device comprises sand trap, magnetic separator, vortex mixer, forcing multisection flotator and vacuum degasifier. Magnetic separator housing is made of round cross-section tube in the form of two flat-topped elements filled with ferromagnetic material pellets and joined together forming closed circuit. The flotation plant is divided into n-sections by baffles and purified water successively goes through these sections; in bottom part of every section the expansion device is installed.

EFFECT: increasing of oil-containing waters degree of purification.

8 cl, 2 dwg, 1 tbl

Description

The invention relates to methods and devices for the treatment of oily wastewater, in particular reservoir, commercial and storm sewage of oil fields.

A device for processing oil water containing a flotation chamber, a dispersant of an air mixture, a foam collector, a gas recirculation system, a gas separator / 1 /. The device does not give a sufficiently high effect of oil field water purification.

The closest technical solution to the claimed invention is the construction of treatment of produced and storm water linear pumping gas booster stations / 2 /. The construction contains a sedimentation tank, a flotator, a coalescing-hydrophobic filter, an electrochemical and sorption filter, a reagent farm (coagulant, bactericidal preparation), a collection of oil sludge, sludge and compost sites, and a pumping station.

A known method of purification / 2 / of produced and storm water includes wastewater treatment by sedimentation in the presence of a coagulant, coarsening of finely dispersed oil droplets due to coalescence on the surface of hydrophobic solid materials, extraction of emulsified oil by filtration in a hydrocarbon medium. Purified water is discharged into a pond, in which it is saturated with atmospheric oxygen, then mixed with purified household water, after which it undergoes post-treatment in natural conditions in ponds.

The known method and device for its implementation do not give a sufficiently high effect of water purification from oil, suspended solids, dissolved gases.

The present invention solves the technical problem of increasing the degree of water purification.

This problem is solved by the fact that in the method of preparing formation water for a system for maintaining formation pressure of oil fields, including water purification by sedimentation, flotation in the presence of a coagulant, coarsening of finely dispersed drops of oil due to coalescence on the surface of hydrophobic solid materials, extraction of emulsified oil by filtration in hydrocarbon the medium according to the invention, formation water is purified by sedimentation from sand fractions, followed by filtration in a granular magnetized a ferromagnetic material forming a closed magnetic circuit and located in an external magnetic field, the coagulant is dosed, floated with dissolved gas bubbles due to pressure relief, and flotation is carried out sequentially in several sections, the amount of which is selected depending on the desired cleaning effect according to the formula C = C ₀ / (1 + Kt / ⁿ⁾ n, wherein C and C ₀ - current and initial concentration of oil, respectively, Kt - flotation dimensionless parameter, n - the number of sections dissolved corrosive gases are removed by evacuation, Dozy cosiness is bactericidal preparations, while the magnetic separator is periodically washed with a reverse current of water with the magnetic field turned off, and the washing water and filter sludge are separated into oil products, suspended solids and water, the oil products being supplied to marketable oil, water is returned to the formation water treatment cycle, and drainage water is reused, in addition, gas separation is carried out at a pressure of 0.001 ... 0.005 MPa, the magnetic field strength is maintained in the range of 1 ... 2 kA / m.

This problem is also solved by the fact that the device for producing produced water for the system for maintaining the reservoir pressure of oil fields, comprising a flotation apparatus, reagent farm, a coalescing-hydrophobic filter, a sump, a collection of oil sludge, sludge pads, a pumping station, according to the invention, contains sand trap connected in series, magnetic separator with power supply, vortex mixer, multi-section pressure flotator with oil collecting device, vacuum degasser with vacuum asosome, a reservoir of pure water, and the casing of the magnetic separator is made of coarse round cross-section in the form of two U-shaped elements filled with granules of ferromagnetic material interconnected to form a ring system, electromagnetic coils are placed on the linear part of the lower U-shaped element, and the upper and lower parts of the annular housing are water supply and drain pipes, respectively, in addition, the flotation apparatus is divided into n-sections with the help of partitions, through which rohodit cleaned water, in the bottom of each section is taken by the throttling device into which is fed a certain fraction of cleaned water saturated with dissolved gases, wherein the apparatus comprises recirculation of wash water, comprising wash pump, hydrophobically coalescing filter, settling tank, a collection of sludge.

Figure 1 presents the technological scheme for the treatment of produced water. Figure 2 presents the magnetic separator.

The technological scheme includes a sand trap 1 connected in series, a magnetic separator 2 with a power source 3, a vortex mixer 4, a pressure flotation apparatus 5, a vacuum degasser 6, a clean water tank 7, a pump station 8. A reagent farm 9 is provided for supplying coagulant, a reagent farm 10 - to supply a bactericidal drug.

The wash water system includes a wash water pump 11, a hydrophobic-coalescing filter 12, a sludge collector 13, and a settling tank 14. The settling zones of the sand trap 1 and settling tank 14 are connected to the sludge pad 15.

Magnetic separator 2 is an annular apparatus filled with granular ferromagnetic material 16, forming a closed magnetic circuit. On the body of the apparatus are electromagnetic coils 17.

The construction works as follows. The produced water in a mixture with commercial, storm water and industrial waste is fed to a sand trap 1, in which large suspended solids are separated. Next, water is supplied to the magnetic separator 2, in which the bulk of the suspended matter is extracted under the influence of a magnetic field. A magnetic separator is a filter loaded with ferromagnetic particles, such as steel or cast iron. Iron balls, shavings, or irregularly shaped particles may be used as loading. The particle size is 2 ... 10 mm. When passing current from a source 3 through a winding of electromagnetic coils 17, a magnetic field with a strength of 1 ... 2 kA / m is created in the separator body, the lines of force of which are evenly distributed over the apparatus cross section. Due to the ring-shaped design of the magnetic separator, the magnetic resistance of the circuit is minimized and dissipation currents are eliminated. This external magnetic field magnetizes ferromagnetic particles, while an internal magnetic field arises between the particles, the intensity of which is many times greater than the strength of the external field. Pollutants dispersed in water are either paramagnetic or ferromagnetic. Under the action of an internal magnetic field, magnetic forces act on the particles being extracted, which are several orders of magnitude more than the molecular forces acting in standard grain filters, which leads to an increase in the hydraulic load on the separator with the same water treatment effect.

The body of the magnetic separator is made of a circular pipe in the form of two U-shaped elements filled with granules of ferromagnetic material (balls, shavings, crushed particles), interconnected to form an annular system, electromagnetic coils are placed on the linear part of the lower U-shaped element , and in the upper and lower parts of the housing are pipes for supplying and discharging water, respectively. The upper U-shaped element is equipped with loading hatches used in the process of loading the apparatus with ferromagnetic granules.

It should be noted that an essential requirement for water injected into the formation is the absence of dissolved gases (oxygen, hydrogen sulfide). Oxygen is not only a corrosive agent, but also under formation conditions forms Fe (OH) ₃ hydroxide, which leads to formation clogging. When oxygen dissolved in water interacts with granular iron in a magnetic separator, its oxidation occurs, as a result of which oxygen is extracted from the water.

The coagulant is dosed into previously purified water using a reagent farm 9, the reagent is mixed with water in a vortex mixer 4, the mixture is fed to a pressure three-section flotator 5. The flotation agent is hydrocarbon gas and hydrogen sulfide, which are released from the water when pressure is released from 0.3 .. .0.5 MPa to 0.1 MPa.

The cleaned gas-saturated water is fed through the throttling device to the inlet of the apparatus, and 6 ... 9% of this water is supplied to the throttling devices located in the lower part in each of the three sections in equal shares. This solution allows you to increase the number of gas bubbles in the second and third sections of the apparatus compared to a standard flotator with one inlet throttling device.

Let us compare the effect of treating produced water with a flotator from one section and with three sections with the same dimensions of the apparatus and other equal conditions. The cleaning effect of such devices is determined accordingly:

C ₁ = C ₀ / (1 + Kt); C ₃ = C ₀ / (1 + Kt / 3) ³ ; C _n = C ₀ / (1 + Kt / n) ⁿ ,

where C ₁ , C ₂ , C _n - residual pollution after a single-section, three-section and multisection flotator, respectively;

С ₀ - initial pollution content;

Kt is the dimensionless flotation parameter, the value Kt = 6.6 is experimentally determined;

n is the number of sections.

It follows that C ₁ / C ₃ = 4.3, i.e. A three-section flotator is 4.3 times more efficient. As the number of sections increases, the cleaning effect will increase.

During the flotation process, emulsified oil and small suspended solids remaining in the water are floated to the surface, removed by a foam collecting device and discharged to a hydrophobic-coalescing filter 12 for separation into oil and water.

The extraction of residual dissolved gases (oxygen and hydrogen) occurs in a vacuum degasser 6 with a vacuum pump. While maintaining the pressure in the apparatus of 0.001 ... 0.005 MPa in water, trace concentrations of dissolved gases that meet industry standards (0.5 mg / l) remain.

After the introduction of a bactericidal preparation into the water, using a reagent farm 10, the water is supplied to the clean water tank 7, from where the pumping station 8 is supplied to the reservoir pressure maintenance system.

The washing of the magnetic separator 2 is carried out by the washing pump 11 with the power source 3 turned off. The washing water, together with the flotation slurry, is supplied to the hydrophobic-coalescing filter 12, in which the oil is separated from the water. Oil is removed to the sludge collection tank 13, water to the sump 14. Sludge from the sand trap 1 and sump 14 is removed to the sludge sites for dewatering and disposal, drainage water from the sludge sites is returned to the head of the structure.

The results of a technical and economic comparison of the options are shown in the table.

Pollutants The residual content of pollutants, mg / l According to the prototype According to the invention Oil products 0.05 0.1 Suspended matter 2 one Oxygen twenty 0.5 Hydrogen sulfide one hundred 0.5

From the above data it follows that the prototype achieved a higher effect of purification of oily wastewater from oil products, which is obtained through the use of a sorption filter. In the case of using purified formation water for injection into the formation, such a high degree of water purification is not required, therefore, it makes no sense to use expensive sorbents.

In the case of the prototype, coalescing-hydrophobic and electrochemical filters are used to clean the main water stream, the calculated water flow rate in which is 5 ... 10 m / h. In the present invention, the main water stream is purified in a magnetic separator, the estimated water flow rate in which is 90 ... 110 m / h, which significantly reduces the capital cost of manufacturing equipment.

In the present invention, the amount of wash water is reduced due to the fact that in the magnetic separator, pollution is delayed due to the action of magnetic forces. Contaminants are easily washed out by a reverse current of water when the power source is off, when there is no magnetic field. The flushing time of the magnetic separator is 1 ... 2 min, while the flushing time of granular filters (including electrochemical filters) is 5 ... 6 min (clause 6.110 / 3 /).

Literature

1. A.S. No. 1393796, C02F 1/24. Installation for oilfield water treatment. / Nurutdinov R.G., Markhasin I.L., Nazarov V.D. et al. / B.I. 17, 1988.

2. Nazarov V.D., Rusakovich A.A., Vadulina N.V. Facilities for treatment of commercial and storm water LPPS. / Environmental protection in the oil and gas sector. - No. 7, 2004. - P.24-26.

3. SNiP 2.04.02-84. Water supply. External networks and structures: M., Gosstroy of Russia, 2004.

Claims (8)

1. A method of preparing formation water for a system for maintaining formation pressure of oil fields, including purification of water by sedimentation, flotation in the presence of a coagulant, coarsening of finely dispersed drops of oil due to coalescence on the surface of hydrophobic solid materials, extraction of emulsified oil by filtration in a hydrocarbon medium, characterized in that formation water is sequentially purified by sedimentation from sand fractions, filtered in a magnetized granular ferromagnetic material, finding in a magnetic field, and the ferromagnetic material forms a closed magnetic circuit, the coagulant is dosed, floated with dissolved gas bubbles due to pressure relief, and flotation is carried out sequentially in several sections, the amount of which is selected depending on the desired cleaning effect according to the formula C = C ₀ / ( 1 + Kt / ⁿ⁾ n, wherein C and C ₀ - current and initial concentration of oil, respectively, Kt - flotation dimensionless parameter, n - the number of sections dissolved corrosive gases are removed by evacuation, metered bakteritsi in this case, the magnetic separator is periodically washed with a reverse current of water with the magnetic field turned off, and the washing water and filter sludge are separated into oil products, suspended solids and water, the oil products being supplied to marketable oil, water is returned to the formation water treatment cycle, the sediment is dehydrated, and drainage water is reused. 2. The method according to claim 1, characterized in that the external magnetic field strength is maintained in the range of 1 ... 2 KA / m 3. The method according to claim 1, characterized in that the gas separation is carried out under a pressure of 0.001 ... 0.005 MPa. 4. A device for preparing produced water for a system for maintaining reservoir pressure in oil fields, comprising a flotation apparatus, reagent farm, coalescing-hydrophobic filter, a settling tank, a sludge collector, sludge pits, a pumping station, characterized in that it contains sand trap connected in series, a magnetic separator with power supply, vortex mixer, multi-section pressure flotator with oil collecting device, vacuum degasser with vacuum pump, clean water tank, m the body of the magnetic separator is made of a circular pipe in the form of two U-shaped elements filled with granules of ferromagnetic material interconnected to form a ring system, electromagnetic coils are placed on the linear part of the lower U-shaped element, and in the upper and lower parts of the annular body water inlet and outlet pipes are located, respectively, in addition, the flotation device is divided into n sections with the help of partitions, through which the water to be cleaned passes sequentially, in the lower Asti each section taken throttling device into which is fed a certain fraction of cleaned water saturated with dissolved gases, wherein the apparatus comprises recirculation of wash water, comprising wash pump, hydrophobically coalescing filter, settling tank, a collection of sludge. 5. The device according to claim 4, characterized in that 6 ... 9% of gas-saturated formation water is supplied to the throttling devices in equal shares to each throttle section. 6. The device according to claim 4, characterized in that the number of sections of the flotation apparatus is 3. 7. The device according to claim 4, characterized in that granules made of steel St3 or cast iron are used in the magnetic separator. 8. The device according to claim 4, characterized in that the size of the granules in the magnetic separator is 2 ... 10 mm

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