CN115925204A - Offshore oilfield production water on-site treatment and on-site reinjection system and process - Google Patents
Offshore oilfield production water on-site treatment and on-site reinjection system and process Download PDFInfo
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Abstract
The invention relates to the technical field of oilfield water treatment, and discloses an offshore oilfield produced water on-site treatment and on-site reinjection system and process. By applying the invention, the offshore oilfield production water can stably reach the A2-level standard that the oil content of the production water is less than or equal to 6.0mg/l, the median diameter of suspended particles is less than or equal to 1.5 mu m, and the content of suspended solids is less than or equal to 2.0mg/l, so that the on-site treatment and on-site standard reinjection are realized; by utilizing the pure physical mechanics and the critical characteristics of polar materials, the method discards the dependence on chemical agents, is more environment-friendly, has no regenerative pollution, has small selectivity on pollutants, and has the advantages of high reaction speed, low energy consumption, low cost, stability, reliability and wide application range.
Description
Technical Field
The invention relates to the technical field of oilfield water treatment, in particular to an offshore oilfield production water on-site treatment and on-site reinjection system and process.
Background
Crude oil extracted from oil fields contains 50-95% of water, and the water content is continuously increased. In multiple oil extraction in an oil field, oil and water phases of liquid extracted from an oil well are separated by a separator, the oil phase is conveyed to an oil transfer station, and the water phase is conveyed to a sewage treatment station. The water phase is pretreated in a sewage treatment station by a settling tank and the like to remove floating oil, and then is treated by air flotation and fine filtration processes, and the water reinjected into an oil layer is called oilfield reinjection water. The produced water in the oil field is treated and then used for reinjection, so that the problem of a water source for water injection can be solved, the environment can be protected, and great economic and social benefits are brought to the oil field.
The method has the advantages that the outward discharge concentration and the outward discharge amount of production water are reduced in areas such as oil and gas fields, the production water treatment process is optimized, and the concentration of pollutants such as petroleum is reduced; the produced water reinjection rate is improved and the sewage discharge amount is reduced by measures of shutting down a high water-containing well, increasing reinjection, newly adding a small platform for in-situ reinjection and the like.
In the integral development process of the offshore oil field, the produced water of the production well of the old oil field rises, and the produced water is increased due to the operation of a new wellhead platform. The produced water of the offshore oil field is reinjected into the stratum, so that the produced water can be prevented from being discharged, the marine environment is protected, the stratum pressure can be kept, the water drive direction is changed, and the recovery ratio of petroleum development is improved. Because produced water contains oil, solid-phase particles and other impurities, the produced water cannot be directly reinjected into the stratum, otherwise the stratum is polluted quickly, and the workload and the operation cost for removing the blockage in the future are increased. Therefore, the oil field production water must be treated first and can be reinjected after reaching the standard. The conventional process for treating and reinjecting production water of the existing offshore oil field comprises the steps of firstly carrying out oil-water separation treatment on oil field sewage through a coalescence degreaser, a cyclone, an air floatation device and the like, then carrying out multistage filtration treatment, wherein the multistage filtration treatment comprises a walnut shell filter serving as first-stage filtration, a multi-medium filter or a fiber medium filter serving as second-stage filtration and a superfine filter serving as third-stage filtration, and finally reinjecting water which reaches the reinjection standard.
However, the offshore oil field production water treatment reinjection process route and the technical device in the prior art have the following defects:
1. the pure physical gravity separation equipment has large floor area, high capital investment, poor treatment effect on emulsified oil and long retention time of wastewater;
2. the general centrifugal separation equipment has poor adaptability and separation effect on the oily wastewater with the relative density of crude oil of more than 0.9;
3. the pressure settling equipment has insufficient fluctuation resistance to the fluctuation change of the inflow amount and the change of the physical property of water quality;
4. the conventional medium filter has higher operating cost, large occupied space volume and weight, weak capacity of adapting to load change and easy blockage; moreover, the particle size of the filter material is limited, so that the particle size of the granular material cannot be further reduced to improve the filtering precision and efficiency;
5. in the application process of chemical oxidation, the utilization rate of an oxidant and the efficiency of a generator thereof need to be improved, a catalyst cannot be used repeatedly, and the treatment cost is high;
6. the traditional air floatation separation equipment has large volume and weight, long retention time and low separation efficiency;
7. the general problems of various physical membrane filtration devices in the past are as follows: the equipment investment cost is high, the filter element service cycle is short, the replacement cost is high, the occupied space and the weight of the equipment are large, the energy consumption is high, the membrane flux attenuation is obvious, the equipment is easy to be polluted, the online cleaning is not thorough, and a large amount of new waste water is generated in the cleaning and regeneration process.
The offshore platform is limited by the space problem, the newly added system has strict requirements on the type selection of equipment and higher requirements on the efficiency of related medicaments, the treatment quality of the produced sewage after the newly added system is put into use is unstable, and the phenomenon of non-standard treatment exists, mainly shows that the indexes such as oil content, suspended matters, particles and the like exceed the standard, and the condition of non-compatibility with underground water mixing reinjection exists, so that the treatment capacity of the system cannot reach the design standard, the reinjection amount cannot be improved, the stratum energy recovery is slow, and the produced water which meets the standard cannot be stably treated and reinjected.
Aiming at the characteristics of offshore production platforms and the practical problems faced by water treatment reinjection, the urgent solution is as follows: the method is characterized by comprising the following steps of establishing an optimal process route for on-site treatment and on-site reinjection of production water of an offshore oilfield, matching and designing deep treatment equipment and reinjection equipment of the production water, realizing optimal equipment space size and weight limit and simple and reliable installation mode, solving the technical index problem of reinjection of the production water of an offshore platform, reducing pollution of the production water to the marine environment and obtaining expected environmental and social and economic values.
Disclosure of Invention
Aiming at the problems and the defects in the prior art, the invention is researched and developed by combining the current new material, new process and new technology, is suitable for the environment with narrow and compact installation space, limited bearing weight and dangerous and explosive oil gas of an offshore production platform, designs or selects the technical devices which are more environment-friendly, low in energy consumption, pollution-free, stable and reliable, wide in application range, high in reaction speed, low in cost and small in pollutant selectivity, and combines the technical devices into an optimal on-site treatment and on-site reinjection process route; aiming at various offshore oilfield production water, the indexes of the treated production water reach the A2 requirement (oil content is less than or equal to 6 mg/l, the median of the diameter of suspended particles is less than or equal to 1.5 mu m, and the content of suspended solids is less than or equal to 2 mg/l) of SY/T5329-2012 'recommended water quality index for clastic rock oil reservoir water injection and analysis method' through process means such as oil removal, degassing, desanding, suspended solids removal, sterilization, neutralization and filtration, and finally the production water is injected into a wellhead through a water injection pump, so that zero discharge of wastewater is realized, and the technical problem in the background art is solved.
The technical scheme of the invention is realized as follows:
the offshore oilfield production water on-site treatment and on-site reinjection system comprises seven-stage separation devices, namely a first-stage functional gas-liquid two-phase separation device, a second-stage functional oil-water two-phase hydrocyclone separation device, a third-stage functional oil-water two-phase cyclone centrifugal separation device, a fourth-stage functional oil-water two-phase coalescence demulsification separation device, a fifth-stage functional oil-water two-phase cyclone air flotation separation device, a sixth-stage functional oil-water two-phase fine filtration separation device and a seventh-stage functional oil-water two-phase ultrafiltration separation device, wherein the seven-stage separation devices are sequentially connected through a pipeline, the seven-stage functional oil-water two-phase ultrafiltration separation device is further connected with a water injection buffer tank and a water injection pump, and production incoming liquid of an offshore oilfield enters the first-stage functional gas-liquid two-phase separation device, sequentially passes through the seven-stage separation devices, the water injection buffer tank and the water injection pump and is finally reinjected to a wellhead; the second-stage functional oil-water two-phase hydrocyclone separation device, the third-stage functional oil-water two-phase hydrocyclone centrifugal separation device, the fourth-stage functional oil-water two-phase coalescence demulsification separation device, the fifth-stage functional oil-water two-phase cyclone air-flotation separation device, the sixth-stage functional oil-water two-phase fine filtration separation device and the seventh-stage functional oil-water two-phase ultrafiltration separation device are respectively connected with a sump oil storage tank, the sump oil storage tank is connected with a pressurization oil delivery pump, and the pressurization oil delivery pump is connected with an oil delivery system; the first-stage function gas-liquid two-phase separation device, the fifth-stage function oil-water two-phase cyclone air flotation separation device and the dirty oil storage tank are connected with a gas recovery device.
Further, an inlet of the first-stage function gas-liquid two-phase separation device is connected with a production gas-liquid source input pipeline, an outlet at one end of the first-stage function gas-liquid two-phase separation device is connected with a first-stage separation associated gas output pipeline, and an outlet at the other end of the first-stage function gas-liquid two-phase separation device is connected with a first-stage separation liquid phase output pipeline; the primary separation liquid phase output pipeline is connected with an inlet of the secondary function oil-water two-phase hydrocyclone separation device, an outlet at one end of the secondary function oil-water two-phase hydrocyclone separation device is connected with a secondary separation oil phase output pipeline, and an outlet at the other end of the secondary function oil-water two-phase hydrocyclone separation device is connected with a secondary separation water phase output pipeline.
Further, the second-stage separation water phase output pipeline is connected with an inlet of the third-stage function oil-water two-phase cyclone centrifugal separation device, an outlet at one end of the third-stage function oil-water two-phase cyclone centrifugal separation device is connected with a third-stage separation oil phase output pipeline, and an outlet at the other end of the third-stage function oil-water two-phase cyclone centrifugal separation device is connected with a third-stage separation water phase output pipeline; the three-stage separation water phase output pipeline is connected with an inlet of the four-stage functional oil-water two-phase coalescence demulsification separation device, an outlet at one side of the four-stage functional oil-water two-phase coalescence demulsification separation device is connected with a four-stage separation oil phase output pipeline, and an outlet at the other side of the four-stage functional oil-water two-phase coalescence demulsification separation device is connected with a four-stage separation water phase output pipeline; the four-stage separation water phase output pipeline is connected with an inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device, the five-stage function oil-water two-phase cyclone air-flotation separation device is provided with three outlets of an oil phase, a gas phase and a water phase, the oil phase outlet is connected with the five-stage separation oil phase output pipeline, the gas phase outlet is connected with the five-stage separation associated gas output pipeline, the water phase outlet is connected with the five-stage separation water phase output pipeline, and a five-stage separation associated gas circulating air-flotation pipeline is further connected between the gas phase outlet and the inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device.
Furthermore, the five-stage separation water phase output pipeline is connected with the inlet of the six-stage functional oil-water two-phase fine filtering and separating device, the outlet at one end of the six-stage functional oil-water two-phase fine filtering and separating device is connected with a six-stage separation oil phase output pipeline, and the outlet at the other end of the six-stage functional oil-water two-phase fine filtering and separating device is connected with a six-stage separation water phase output pipeline; the device comprises a six-stage separation water phase output pipeline, a buffer water tank inlet, a buffer water tank liquid phase output pipeline, a pre-ultrafiltration pressurization input pipeline, a seven-stage functional oil-water two-phase ultrafiltration separation device inlet, a first end outlet of the seven-stage functional oil-water two-phase ultrafiltration separation device, a seven-stage separation oil sludge output pipeline, a second end outlet of the seven-stage separation oil-water two-phase ultrafiltration separation device, a circulating filtration return buffer water tank pipeline, a buffer water tank inlet, a seven-stage separation water phase output pipeline, a standard water injection buffer tank inlet, a standard water injection circulation bypass, a standard pre-ultrafiltration pressurization input pipeline, a standard water injection output pipeline, and a water injection pressurization reinjection pipeline.
Furthermore, the primary function gas-liquid two-phase separation device adopts a double-inclined lower inclined cyclone inlet, and a mist cyclone separation pipe is arranged inside the primary function gas-liquid two-phase separation device.
Furthermore, the two-stage function oil-water two-phase hydrocyclone separation device adopts a high-kinetic energy hydrocyclone centrifugal separator to replace the conventional gravity settling separation, and a liquid-liquid hydrocyclone separation conical pipe is arranged in the hydrocyclone separation device.
Furthermore, the three-stage function oil-water two-phase rotational flow centrifugal separation device adopts a radial diversion high-speed rotational flow pipe to replace a conventional tangential rotational flow pipe, and the radial diversion high-speed rotational flow pipe is arranged inside the three-stage function oil-water two-phase rotational flow centrifugal separation device.
Furthermore, the four-stage functional oil-water two-phase coalescence, demulsification and separation device adopts three polarity combined fillers of hydrophilic oleophobic property, oleophilic hydrophobic property and hydrophobic oleophobic property of the nano ceramic home position coating to replace the conventional modified fiber filler or standard series corrugated orifice plate coalescence filler.
Furthermore, the five-stage function oil-water two-phase rotational flow air flotation separation device adopts the combined function of double tangential centrifugal rotational flow and dissolved air pump micro bubble flotation to replace the conventional single jet flow micro bubble flotation or single dissolved precipitation type micro bubble air flotation.
Furthermore, the six-stage functional oil-water two-phase fine filtering and separating device comprises a filter element, a shell, a discharge valve, a differential pressure gauge, a drain valve, a sampling joint and the like, wherein the filter element is a PP spray-melting folding filter element with high flux and large dirt receiving capacity.
Furthermore, the seven-stage functional oil-water two-phase ultrafiltration separation device adopts a hollow plate type ceramic membrane externally coated with a hydrophilic oleophobic nano coating as a core separation internal part, and adopts an external inlet and internal outlet filtering mode and an internal inlet and external outlet backwashing mode to replace a conventional honeycomb tube type ceramic membrane without a modified coating, a conventional internal inlet and external outlet cross-flow filtering mode and a medicament soaking internal circulation cross-flow backwashing mode.
The invention also discloses an offshore oilfield produced water on-site treatment and on-site reinjection process, which comprises a primary separation section process, a high-efficiency separation section process and a fine separation section process: the primary separation section process is completed by a primary function gas-liquid two-phase separation device, a secondary function oil-water two-phase hydrocyclone separation device and matched pipelines thereof, and mainly removes discrete oil and free oil with the oil drop particle size of more than 100 micrometers; the high-efficiency separation section process is completed by a three-stage functional oil-water two-phase cyclone centrifugal separation device, a four-stage functional oil-water two-phase coalescence demulsification separation device, a five-stage functional oil-water two-phase cyclone air flotation separation device and matched pipelines thereof, and mainly removes dispersed oil and emulsified oil with the grain size of 10-100 microns of oil drops; the fine separation section process is completed by a six-stage functional oil-water two-phase fine filtering separation device, a seven-stage functional oil-water two-phase ultrafiltration separation device and matched pipelines thereof, and emulsified oil and dissolved oil with the grain size of 1-10 microns of oil drops are mainly removed; the oil-gas-water three-phase mixed medium at the wellhead of the offshore oil field is sequentially subjected to process treatment of a primary separation section, a high-efficiency separation section and a fine separation section, and finally the standard-reaching reinjection of the produced water treatment is completed.
Further, the primary separation stage process comprises: the oil-gas-water three-phase mixed medium at the well head firstly passes through an input pipeline of a gas production liquid source head of each oil well, passes through a primary functional gas-liquid two-phase separation device, most of separated gas phase passes through a primary separation associated gas output pipeline to a gas system, a small part of associated gas is used as flotation gas of a five-stage functional oil-water two-phase cyclone gas-flotation separation device, and separated liquid phase passes through a primary separation liquid phase output pipeline and enters a secondary functional oil-water two-phase cyclone liquid separation device for primary oil-water separation; the oil and water in the liquid phase are rapidly separated by a centrifugal force of over 1000g in the hydrocyclone oil-water separator, the separated oil phase (the water content is less than 20 percent) is discharged to an oil system through a secondary separated oil phase output pipeline, and the separated oily sewage enters a high-efficiency separation section through a secondary separated water phase output pipeline.
Further, the high efficiency separation stage process comprises: oily sewage (oil content is less than 800ppm and suspended solid is less than 300 ppm) entering a high-efficiency separation section firstly enters a three-stage functional oil-water two-phase cyclone centrifugal separation device, the oily sewage is subjected to oil-water rapid and high-efficiency separation by virtue of a centrifugal force (more than 1500 g), an oil phase in the sewage is discharged to a dirty oil system through a three-stage separation oil phase output pipeline, the sewage enters a four-stage functional oil-water two-phase coalescence demulsification separation device through a three-stage separation water phase output pipeline to treat the oil and the suspended solid, so that small oil drops are coalesced into large oil drops to be conveniently removed, the suspended solid is subjected to condensation treatment by utilizing a nano ceramic polar coating filler, the hydrophobic and oleophobic, hydrophilic and oleophobic and oleophilic hydrophobic mixed combined filler with polar characteristics can be used for physical demulsification and three-phase critical resolution, and favorable separation conditions are created for next-stage high-efficiency cyclone gas flotation treatment, the separated oil phase is discharged to a sump oil system through a four-stage separation oil phase output pipeline, the separated water phase enters a five-stage functional oil-water two-phase cyclone flotation separation device through a four-stage separation water phase output pipeline, the produced water is subjected to deep high-efficiency separation of oil and water and synchronous removal of suspended matters in high-efficiency cyclone flotation under the double actions of cyclone and flotation, the separated oil phase is discharged to the sump oil system through the five-stage separation oil phase output pipeline, the redundant associated gas is discharged to a gas system through the five-stage separation associated gas output pipeline, the five-stage separation associated gas circulating flotation gas pipeline realizes cyclic utilization of most flotation gas, and the separated oily sewage reaches the water quality superior to C3 (can meet the discharge requirement of all sea areas) and then enters a fine separation section through the five-stage separation water phase output pipeline.
Further, the fine separation stage process comprises: the oily sewage (oil content is less than 30ppm and solid suspended matter is less than 10 ppm) entering the fine separation section firstly enters a six-stage functional oil-water two-phase fine filtering separation device, under the action of an activated mesoporous aluminosilicate filter material of a glass structure matrix, oil particles, suspended solids, crystallized salt particles, bacteria and the like in the water are deeply filtered, the filtered oil sludge, salt crystals and bacteria are discharged to an oil system through a six-stage separated oil phase output pipeline, filtered water is discharged into a buffer water tank through a six-stage separated water phase output pipeline, the buffer water tank has certain buffer retention time and can receive unqualified circulating filtered water treated by a seven-stage functional oil-water two-phase ultrafiltration separation device, the filtered water which can keep safe and stable is conveyed to a pre-ultrafiltration pressurization input pipeline through a buffer water tank liquid phase output pipeline to enter a seven-stage functional oil-water two-phase ultrafiltration separation device for final ultrafiltration or separation, the ultrafiltration concentrate generated by ultrafiltration is conveyed to an oil sludge system through a seven-stage separated oil sludge output pipeline, the qualified final qualified water is conveyed to a seven-stage separated water phase output pipeline to an oil sludge buffer tank, part of the water injection bypass circulation bypass is used for standard reaching, and the water injection pressure of the ultrafiltration dilution device, and the water is returned to the oil field.
Compared with the traditional process route and equipment, the beneficial technical effects realized and obtained by the invention comprise:
1. by applying the technical scheme of the invention, the produced water of the offshore oilfield can stably reach the A2-grade standard of the produced water (the oil content is less than or equal to 6.0mg/l, the median of the diameters of suspended particles is less than or equal to 1.5 mu m, the content of suspended solids is less than or equal to 2.0 mg/l) after two-stage deep filtration treatment of fine filtration and ultrafiltration, the A1-grade higher standard of the produced water (the oil content is less than or equal to 5.0mg/l, the median of the diameters of suspended particles is less than or equal to 1.0 mg/l) can be realized under the working condition of high-quality water, and the standard reinjection of the produced water treatment is finally completed.
2. The technical scheme of the invention abandons the traditional gravity settling and filtering separation principle and route, abandons the dependence of the existing reinjection water treatment technology on chemical agents, establishes the principles and routes of cyclone centrifugation and separation of new polar materials, adopts the basic principles of pure physical mechanics and critical characteristics of polar materials, and has the advantages of environmental protection, low energy consumption, no regenerative pollution, stability, reliability, wide application range, high reaction speed, low cost, low selectivity on pollutants and the like.
3. The method has the advantages that the conventional process technology and the conventional equipment device are abandoned, all equipment and units form high-efficiency physical separation equipment and a technical device which adopt a new technology and a new technology, the design and selection of a core device, the matching of the structural functions of internal parts of the core device, the grasping and application of key process technologies in each stage and the cooperative combination of the combination scheme technology can professionally, accurately and efficiently solve the problem of zero emission of water injection of offshore oilfields, and the method is suitable for practical industrial application.
4. The array mode of large occupied area, large volume and large weight of single equipment units is abandoned, the tightening integrated mode of small occupied area, small volume and small weight of standard container equipment integrated is created, and under the same treatment capacity and treatment requirements, the treatment system provided by the invention at least reduces the occupied space size by 1/3 compared with the prior art, reduces the operation weight by more than 1/4, has the advantage of cost performance and price ratio, and only has manpower management cost and little spare part material consumption (the offshore electric energy is self-sufficient and equivalent to free).
5. Compared with the prior art, the treatment system has no chemical agent auxiliary treatment process system and disposable functional devices or internal parts, thereby eliminating the secondary treatment of chemical poison and solid waste.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of an offshore oilfield production water in-situ treatment and in-situ reinjection system;
FIG. 2 is a detailed view of the offshore oilfield produced water in-situ treatment and in-situ reinjection system;
FIG. 3 is a primary separation section structure diagram of an offshore oilfield production water in-situ treatment and in-situ reinjection system;
FIG. 4 is a structural diagram of an efficient separation section of an offshore oilfield production water in-situ treatment and in-situ reinjection system;
FIG. 5 is a diagram of a fine separation section of an offshore oilfield produced water in-situ treatment and in-situ reinjection system;
FIG. 6 is a schematic structural view of a first-stage functional gas-liquid two-phase separation device;
FIG. 7 is a schematic structural view of a two-stage functional oil-water two-phase hydrocyclone separation device;
FIG. 8 is a schematic structural view of a three-stage functional oil-water two-phase cyclone centrifugal separation device;
FIG. 9 is a schematic structural diagram of a four-stage functional oil-water two-phase coalescence demulsification separation device;
FIG. 10 is a schematic structural view of a five-stage functional oil-water two-phase cyclone air-flotation separation device;
FIG. 11 is a schematic structural view of a six-stage functional oil-water two-phase fine filtering and separating device;
FIG. 12 is a schematic structural diagram of a seven-stage functional oil-water two-phase ultrafiltration separation device.
The figures are labeled as follows:
01. a production gas-liquid source input pipeline; 02. a first-stage functional gas-liquid two-phase separation device; 03. a first-stage separation associated gas output pipeline; 04. a first-stage separation liquid phase output pipeline; 05. a second-stage function oil-water two-phase hydrocyclone separation device; 06. a second-stage separated oil phase output pipeline; 07. a second-stage separated water phase output pipeline; 08. a three-stage function oil-water two-phase cyclone centrifugal separation device; 09. a three-stage separated oil phase output pipeline; 10. a three-stage separated water phase output pipeline; 11. a four-stage functional oil-water two-phase coalescence demulsification separation device; 12. a four-stage separated oil phase output pipeline; 13. a four-stage separation water phase output pipeline; 14. a five-stage functional oil-water two-phase cyclone air flotation separation device; 15. a five-stage separated oil phase output pipeline; 16. a five-stage separation associated gas output pipeline; 17. five-stage separation associated gas circulating air flotation pipeline; 18. a five-stage separation water phase output pipeline; 19. a six-stage functional oil-water two-phase fine filtering separation device; 20. six-stage separated oil phase output pipeline; 21. six-stage separated aqueous phase output pipeline; 22. a buffer water tank; 23. a liquid phase output pipeline of the buffer water tank; 24. circularly filtering and returning to a pipeline of the buffer water tank; 25. a pressurization input pipeline before ultrafiltration; 26. a seven-stage functional oil-water two-phase ultrafiltration separation device; 27. a seven-stage separation oil sludge output pipeline; 28. a seven-stage separated water phase output pipeline; 29. a water injection buffer tank reaching the standard; 30. a standard-reaching water injection circulation bypass; 31. a water injection output pipeline reaching the standard; 32. a water injection and pressurization reinjection pipeline reaching the standard; 051. a high kinetic energy cyclone centrifugal separator; 052. an oil core; 053. separating cone; 054. a tail pipe.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
The offshore oilfield production water on-site treatment and on-site reinjection system and process provided by the embodiment of the invention aim to achieve the A2-level standard requirements (oil content is less than or equal to 6.0mg/l, median diameter of suspended particles is less than or equal to 1.5 mu m, and content of solid suspended substances is less than or equal to 2.0 mg/l) of SY/T5329-2012 'clastic rock reservoir water injection water quality recommendation index and analysis method') by using oil removal, degassing, sand removal, suspended substance removal, sterilization, neutralization, filtration and other process means aiming at various offshore oilfield production water, and the offshore oilfield production water is injected into a wellhead through a water injection pump.
As shown in fig. 1, an embodiment of the present invention provides an offshore oilfield produced water in-situ treatment and in-situ reinjection system, which includes seven-stage separation devices, namely, a first-stage functional gas-liquid two-phase separation device, a second-stage functional oil-water two-phase hydrocyclone separation device, a third-stage functional oil-water two-phase hydrocyclone centrifugal separation device, a fourth-stage functional oil-water two-phase coalescence and demulsification separation device, a fifth-stage functional oil-water two-phase cyclone air flotation separation device, a sixth-stage functional oil-water two-phase fine filtration separation device, and a seventh-stage functional oil-water two-phase ultrafiltration separation device, wherein the seven-stage separation devices are sequentially connected through a pipeline, and the seven-stage functional oil-water two-phase ultrafiltration separation device is further connected with a water injection buffer tank and a water injection pump; liquid coming from offshore oilfield production enters a first-stage functional gas-liquid two-phase separation device, sequentially passes through the seven-stage separation device, the water injection buffer tank and the water injection pump, and is finally reinjected to a wellhead; the second-stage functional oil-water two-phase hydrocyclone separation device, the third-stage functional oil-water two-phase hydrocyclone centrifugal separation device, the fourth-stage functional oil-water two-phase coalescence demulsification separation device, the fifth-stage functional oil-water two-phase cyclone air flotation separation device, the sixth-stage functional oil-water two-phase fine filtration separation device and the seventh-stage functional oil-water two-phase ultrafiltration separation device are respectively connected with a sump oil storage tank, the sump oil storage tank is connected with a pressurization oil delivery pump, and the pressurization oil delivery pump is connected with an oil delivery system; the first-stage function gas-liquid two-phase separation device, the fifth-stage function oil-water two-phase cyclone air flotation separation device and the dirty oil storage tank are connected with a gas recovery device.
As shown in fig. 2, the seven-stage separation device of the offshore oilfield production water on-site treatment and on-site reinjection system is a first-stage functional gas-liquid two-phase separation device 02, a second-stage functional oil-water two-phase hydrocyclone separation device 05, a third-stage functional oil-water two-phase hydrocyclone centrifugal separation device 08, a fourth-stage functional oil-water two-phase coalescence and emulsion breaking separation device 11, a fifth-stage functional oil-water two-phase cyclone air flotation separation device 14, a sixth-stage functional oil-water two-phase fine filtration separation device 19 and a seventh-stage functional oil-water two-phase ultrafiltration separation device 26, and the seven-stage separation devices are sequentially connected through a pipeline.
As shown in fig. 2 and fig. 3, an inlet of the first-stage functional gas-liquid two-phase separation device 02 is connected with a production gas-liquid source input pipeline 01, an outlet at one end is connected with a subsequent first-stage separation associated gas output pipeline 03, and an outlet at the other end is connected with a first-stage separation liquid phase output pipeline 04; the primary separation liquid phase output pipeline 04 is connected with an inlet of the secondary function oil-water two-phase hydrocyclone 05, an outlet at one end of the secondary function oil-water two-phase hydrocyclone 05 is connected with a secondary separation oil phase output pipeline 06, and an outlet at the other end of the secondary function oil-water two-phase hydrocyclone 05 is connected with a secondary separation water phase output pipeline 07.
As shown in fig. 2 and fig. 4, the second-stage separation water phase output pipeline 07 is connected to an inlet of the third-stage functional oil-water two-phase cyclone centrifugal separation device 08, an outlet at one end of the third-stage functional oil-water two-phase cyclone centrifugal separation device 08 is connected to a third-stage separation oil phase output pipeline 09, and an outlet at the other end of the third-stage functional oil-water two-phase cyclone centrifugal separation device 08 is connected to a third-stage separation water phase output pipeline 10; the three-stage separation water phase output pipeline 10 is connected with an inlet of the four-stage functional oil-water two-phase coalescence demulsification separation device 11, an outlet at one side of the four-stage functional oil-water two-phase coalescence demulsification separation device 11 is connected with a four-stage separation oil phase output pipeline 12, and an outlet at the other side of the four-stage functional oil-water two-phase coalescence demulsification separation device 11 is connected with a four-stage separation water phase output pipeline 13; the four-stage separation water phase output pipeline 13 is connected with an inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device 14, the five-stage function oil-water two-phase cyclone air-flotation separation device 14 is provided with three outlets of an oil phase, a gas phase and a water phase, the oil phase outlet is connected with a five-stage separation oil phase output pipeline 15, the gas phase outlet is connected with a five-stage separation associated gas output pipeline 16, the water phase outlet is connected with a five-stage separation water phase output pipeline 18, and a five-stage separation associated gas circulation air-flotation pipeline 17 is further connected between the gas phase outlet and the inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device 14.
As shown in fig. 2 and fig. 5, the five-stage separation water phase output pipeline 18 is connected to an inlet of the six-stage functional oil-water two-phase fine filtering and separating device 19, an outlet of one end of the six-stage functional oil-water two-phase fine filtering and separating device 19 is connected to a six-stage separation oil phase output pipeline 20, and an outlet of the other end of the six-stage functional oil-water two-phase fine filtering and separating device is connected to a six-stage separation water phase output pipeline 21; the six-stage separation water phase output pipeline 21 is connected with an inlet of a buffer water tank 22, an outlet of the buffer water tank 22 is connected with a buffer water tank liquid phase output pipeline 23, the buffer water tank liquid phase output pipeline 23 is connected with a pre-ultrafiltration pressurization input pipeline 25, the pre-ultrafiltration pressurization input pipeline 25 is connected with an inlet of a seven-stage functional oil-water two-phase ultrafiltration separation device 26, a first end outlet of the seven-stage functional oil-water two-phase ultrafiltration separation device 26 is connected with a seven-stage separation oil sludge output pipeline 27, a second end outlet of the seven-stage functional oil-water two-phase ultrafiltration separation device is connected with a circulation filtration return buffer water tank pipeline 24, the circulation filtration return buffer water tank pipeline 24 is connected with the inlet of the standard water tank 22, a third end outlet of the seven-stage functional oil-water two-phase ultrafiltration separation device 26 is connected with a seven-stage separation water phase output pipeline 28, the seven-stage separation water phase output pipeline 28 is connected with an inlet of a standard water injection buffer tank 29, one side of an outlet of the standard water buffer tank 29 is connected with a standard water injection circulation bypass 30, the standard water injection circulation bypass 30 is connected with the pre-ultrafiltration input pipeline 25, the other side of the standard water buffer tank 29 is connected with a water injection output pipeline 31, and the standard water injection output pipeline 31 is connected with a standard pressure injection return pipeline 32.
As shown in fig. 6, the primary function gas-liquid two-phase separation device 02 mainly comprises a cylinder, a cyclone separator, a high-efficiency foam breaking net, a blow-down valve and other main components, and adopts a double-inclined lower inclined cyclone inlet, and a mist cyclone separation pipe is arranged inside the device. The separation method adopted is cyclone centrifugal separation and wire mesh packing separation.
The gas-liquid mixture enters the primary functional gas-liquid two-phase separation device from the tangential inlet to form a rotational flow, centrifugal force with the specific gravity being many times higher is generated, the gas-liquid phase density is different, the centrifugal force is very different, and the gas and the liquid are separated under the combined action of gravity, centrifugal force and buoyancy. The liquid is pushed to the outside along the radial direction and is discharged downwards from the liquid outlet; and the gas moves to the center and is discharged upward through the gas outlet.
The first-stage function gas-liquid two-phase separation device in the embodiment adopts the mist cyclone separation pipe in the liquid drop area of the gas outlet section, and can better ensure the particle size of liquid drops at the gas phase outlet and meet the requirement of liquid carrying capacity. The mist cyclone separation pipe consists of a group of cyclone demisting cylinders, the gas generates strong centrifugal force through a cyclone flow deflector, liquid drops in the gas collide with the wall of the cyclone cylinder under the action of the centrifugal force and are gathered, then the liquid drops flow out through gaps of the wall of the cyclone cylinder, and the liquid drops are guided into a liquid collection section of the separator through a downcomer; a part of a small amount of gas also flows out through the gap, and the small amount of gas is sucked by the guide vanes positioned at the bottom of the cyclone cylinder and enters the cylinder body for separation again, so that secondary entrainment is avoided; most of the other gas leaves through the top of the cyclone barrel.
As shown in fig. 7, the two-stage functional oil-water two-phase hydrocyclone separation device 05 adopts a high-kinetic energy hydrocyclone separation device to replace conventional gravity settling separation, and is internally provided with a liquid-liquid hydrocyclone separation tapered tube. The device comprises a separation device tank body, wherein the separation device tank body is provided with an oily sewage inlet, an oil discharge port and a water discharge port, and a plurality of high-kinetic energy rotational flow centrifugal separators 051 are arranged inside the separation device tank body. The high kinetic energy rotational flow centrifugal separator 051 comprises a separation cone 053 and a tail pipe 054, the separation cone 053 is communicated with the tail pipe 054, and an oil core 052 is arranged inside the separation cone 053 and the tail pipe 054.
The core oil-water separation element of the second-stage functional oil-water two-phase hydrocyclone 05, namely the high-kinetic energy hydrocyclone 051, utilizes the centrifugal separation principle, the oily sewage axially enters the hydrocyclone (axial cyclone) from the inlet flow passage, a stable cyclone is formed by blades (the gravity acceleration special design), and the oil phase is separated from the water phase by utilizing the different centrifugal force generated by the high-speed rotation of the liquid in the hydrocyclone by the density difference of two mutually insoluble liquids.
The secondary function oil-water two-phase hydrocyclone separation device provided by the embodiment has the advantages that the effective retention time is within 10s, the separation efficiency is more than 98%, the oil content of incoming liquid can be reduced to less than 1000ppm from 20%, the oil content of incoming liquid can be reduced to less than 800ppm from 10%, and the secondary function oil-water two-phase hydrocyclone separation device has the characteristics of low pressure drop (0.5-0.15 MPa), high efficiency, exquisite layout, compact structure, convenience in installation, easiness in operation, stable performance and the like.
As shown in fig. 8, the three-stage functional oil-water two-phase cyclone centrifugal separation device 08 adopts a radial flow guiding high-speed cyclone tube instead of a conventional tangential cyclone tube, and a radial flow guiding high-speed cyclone tube is arranged inside the device. The adopted radial flow guide high-speed cyclone tube is heterogeneous phase mixture method classification equipment with wide application, and oil-water separation is carried out on oily sewage in an oil field under the action of centrifugal force by utilizing the density difference of oil and water. The principle is that oily sewage enters a cyclone cavity through a radial porous inlet of a cyclone cone pipe, the cyclone guide cyclone blades in the cyclone cavity generate high-speed rotation, under the action of a centrifugal field generated by the high-speed rotation, a water phase in the oily sewage generates centrifugal sedimentation, rotates to a underflow port along the wall surface of the cone pipe and is discharged as underflow: the oil with low density migrates towards the middle, rotates towards the top flow port along the axis and is discharged as top flow, and the oil-water separation is completed in the taper pipe.
The three-stage function oil-water two-phase cyclone centrifugal separation device provided by the embodiment is suitable for the oil-containing sewage with the water inlet pressure not lower than 500kpa g, the oil-water density difference not lower than 50kg/m & lt 3 & gt, the oil-containing sewage with the water inlet content not higher than 2000ppm and the suspended matters not higher than 800 ppm.
As shown in FIG. 9, the four-stage functional oil-water two-phase coalescence demulsification separation device 11 comprises a feeding inlet, an oil outlet and a water outlet, and a plurality of groups of coalescence cores inside the device, wherein three (hydrophilic oleophobic, oleophilic hydrophobic, hydrophobic oleophobic) polarity combination fillers of a nano ceramic home-position coating are adopted to replace the conventional modified fiber fillers or standard series corrugated hole plate coalescence fillers. The four-stage functional oil-water two-phase coalescence demulsification separation device 11 is a pure physical demulsification oil-water separation device which aims at the difficulty in demulsification and separation of highly emulsified oily wastewater. The removal precision of emulsified oil in the equipment can reach 0.1 mu m, and the waste water in the oil and gas field can be treated to be below 10 ppm. The rapid emulsion breaking, gathering and separation of the emulsified oil are realized by adopting the combined action of a special poly-acetate fiber material, a gathering core with a unique structural design and a gathering filler.
In this example, the coalescing core dimensions were 6 "x 56", characteristics: ultrahigh precision coalescence demulsification (up to 0.1 mu m), polar fiber material and CFD structural design, excellent chemical compatibility, no failure caused by the existence of a surfactant, long-term stable online operation, high cross-sectional flow rate, single treatment capacity of 10m & lt 3 & gt/h, high pollutant carrying capacity and strong pollution resistance.
The coalescence principle: the tiny oil drops (emulsified oil) are captured by the special polyacetyl fiber and then absorbed; under the push of the fluid, a plurality of emulsified oil drops gradually move and enrich along the fibers to the cross point; the emulsion sleeve drops which are continuously enriched collide, break emulsion and coalesce at the cross point of the fibers, and are coalesced to grow into larger oil drops; under the action of water flow, larger oil drops fall off from the fiber fork points and continue to move downstream: the larger oil drops repeat the steps of adsorption, enrichment, collision, emulsion breaking, coalescence and the like in a larger opening area, directly grow into larger dispersed oil drops, and then enter a coalescence filler area for rapid separation.
The coalescence filler has the characteristics that: the filler is specially designed, so that the aggregation and coalescence of the small poise drops into large oil drops are quickly realized; the specific surface area is large, the coalescence effect is good, and the separation speed is high; high pollutant-receiving capacity and strong pollution resistance.
As shown in fig. 10, the five-stage functional oil-water two-phase cyclone air-flotation separation device 14 mainly comprises a container tank, a manifold, an instrument valve, a circulating dissolved air pump, a dosing device, a special functional part, a structural part, a prying seat and the like. The combined function of double tangential centrifugal rotational flow and dissolved air pump microbubble flotation is adopted to replace the conventional single jet flow microbubble flotation or single dissolved precipitation type microbubble air flotation.
The principle of the five-stage function oil-water two-phase rotational flow air flotation separation device 14 is that oil-water separation is performed by utilizing the effects of air flotation and rotational flow, oil-containing sewage enters a CFU container through two tangential inlets and generates rotational flow, and oil drops and bubbles are accumulated in the middle of the container and float upwards under the action of centrifugal force. The bubble that the quality is lighter and oil drip are under the effect of centrifugal force, gather and coalesce to CFU centre rapidly, simultaneously because the direction of motion of oil drip, bubble and water is unanimous, all upward movement for bubble and oil drip are under the buoyancy and the drag force combined action of water, and the fast rising shortens bubble and oil drip rise time greatly, has improved separation rate, realizes the high-efficient separation of profit.
As shown in fig. 11, the six-stage functional oil-water two-phase fine filtering and separating device 19 is composed of a filter element, a shell, a discharge valve, a differential pressure gauge, a blowdown valve, a sampling joint and the like, wherein the filter element is a PP spray-melted folded filter element with high flux and high pollutant carrying capacity. The filter medium enters the filter tank body through the inlet pipe and passes through the filter element from outside to inside, oil drops and suspended matters are intercepted, filtered water is discharged from a filter water outlet, the pressure difference of the filter rises along with the accumulation of pollutants on the filter element, and when the pressure difference rises to a set value or set time, automatic back washing is carried out. In the embodiment, a high-flow-rate filter element is adopted, a single filter element can reach the flow of 60T/H, a PP inner framework, a double-layer polyester mesh enclosure and a single-opening type filter element are adopted, and the filter element is composed of more than 5 layers of nanofiber membranes.
As shown in fig. 12, in the seven-stage functional oil-water two-phase ultrafiltration separation device 26, the core separation internal component adopts a hollow plate-type ceramic membrane externally coated with a hydrophilic oleophobic nano coating, and adopts an external-in and external-out filtration mode and an internal-in and external-out backwashing mode), so that the conventional honeycomb tube-type ceramic membrane without a modified coating, the conventional internal-in and external-out cross-flow filtration mode and the medicament soaking internal circulation cross-flow backwashing mode are replaced.
The hollow plate-type ceramic membrane is prepared by inorganic ceramic materials through special process treatment, is in a flat plate type and multi-channel shape, micropores are densely distributed on the four walls of the channel to form a natural membrane, under the action of external pressure and internal suction, stock solution flows on the two sides of the flat plate, small molecular substances (or liquid) permeate the membrane, and large molecular substances (or solid particles and liquid droplets) are intercepted by the membrane, so that the purposes of separation and purification are achieved.
When the ceramic membrane filter works, filtered mother liquor enters from the liquid inlet, passes through the ceramic membrane filter plate under the action of system pressure, and filtered clear liquid flows out from each collecting port to finish the filtering process. And substances such as fine suspended matters, impurities and the like in the liquid are intercepted on the surface of the ceramic membrane filter plate, when the ceramic membrane filter plate works to a certain period, the pressure difference can be increased when the fine suspended matters intercepted by the ceramic membrane filter plate reach a certain thickness, aeration cleaning and back washing are carried out at the moment, dirt attached to the plate wall is washed off by utilizing the action of water flow, water is used for back washing or chemically cleaning the ceramic membrane filter plate, and the regeneration process is finished, so that the aim of long-term use is fulfilled.
The ceramic membrane pore size distribution of the seven-stage functional oil-water two-phase ultrafiltration separation device provided by the embodiment of the invention is 0.1 micron, and the process characteristics comprise: the product quality is improved, the retention effect of the filter is good, the filtered clear liquid is pure, the retention effect on the residual suspended matters after flocculation precipitation can be realized, the retention rate is 99 percent, and various effective components in the solution cannot be changed due to the physical filtration; the production capacity is high, compared with the traditional filtering equipment, the processing capacity of the ceramic membrane filter with the same volume is multiple times of that of the traditional filter with the same effect, so that the equipment layout space can be greatly saved, and meanwhile, favorable conditions are provided for expanding the production scale in the future; the regeneration is convenient, the equipment does not need steam boiling for regeneration, and the regeneration process can be completed only by regular aeration cleaning or back washing and chemical cleaning; the operation is simple, the traditional filtering equipment is complex, the complicated valves and pipelines are reduced, the operation is very simple, and the work efficiency is greatly improved; the method has the advantages of low operation cost, good chemical stability of the ceramic membrane, acid resistance, alkali resistance, high temperature resistance, high pressure resistance, wear resistance, microbial corrosion resistance, no deformation of membrane pores, high filtration precision of 0.1 mu m, strong pollution resistance, long service life of 3-5 years, regular water back flushing or chemical cleaning, no need of replacing the ceramic membrane, good membrane regeneration performance, high membrane separation efficiency, good hydrophilicity and energy consumption saving.
The invention also discloses an offshore oilfield production water on-site treatment and on-site reinjection process, which comprises a primary separation section process, a high-efficiency separation section process and a fine separation section process. The offshore oilfield production water in-situ treatment and in-situ reinjection process is completed by using an offshore oilfield production water in-situ treatment and in-situ reinjection system, the complete process flow is shown in figure 2, and a primary separation section process, a high-efficiency separation section process and a fine separation section process are respectively shown in figures 3, 4 and 5.
Referring to fig. 2-5, the primary separation stage process is completed by a primary function gas-liquid two-phase separation device 02, a secondary function oil-water two-phase hydrocyclone separation device 05 and matched pipelines thereof, and mainly removes discrete oil and free oil with the particle size of oil drops of more than 100 microns; the high-efficiency separation section process is completed by a three-stage functional oil-water two-phase cyclone centrifugal separation device 08, a four-stage functional oil-water two-phase coalescence demulsification separation device 11, a five-stage functional oil-water two-phase cyclone air flotation separation device 14 and matched pipelines thereof, and mainly removes dispersed oil and emulsified oil with the grain size of 10-100 microns of oil drops; the fine separation section process is completed by a six-stage functional oil-water two-phase fine filtering and separating device 19, a seven-stage functional oil-water two-phase ultrafiltration separating device 26 and matched pipelines thereof, and emulsified oil and dissolved oil with the grain size of 1-10 microns are mainly removed; the oil-gas-water three-phase mixed medium at the wellhead of the offshore oil field is sequentially subjected to process treatment of a primary separation section, a high-efficiency separation section and a fine separation section, and finally the standard-reaching reinjection of the produced water treatment is completed.
Referring to fig. 2 and 3, the primary separation stage process comprises: the oil-gas-water three-phase mixed medium at the well head firstly passes through a gas production liquid source head input pipeline 01 of each oil well and passes through a primary functional gas-liquid two-phase separation device 02, most of separated gas phase passes through a primary separation associated gas output pipeline 03 to a gas system, a small part of associated gas is used as flotation gas of a five-stage functional oil-water two-phase cyclone air-flotation separation device 14, and separated liquid phase enters a secondary functional oil-water two-phase cyclone liquid separation device 05 through a primary separation liquid phase output pipeline 04 to carry out primary oil-water separation; the oil and water in the liquid phase are rapidly separated in the hydrocyclone oil-water separator by means of a centrifugal force of over 1000g, the separated oil phase (the water content is less than 20 percent) is discharged to an oil system through a secondary separated oil phase output pipeline 06, and the separated oily sewage enters a high-efficiency separation section through a secondary separated water phase output pipeline 07.
Referring to fig. 2 and 4, the high efficiency separation stage process includes: oily sewage (oil content is less than 800ppm and suspended solid is less than 300 ppm) entering a high-efficiency separation section firstly enters a three-stage functional oil-water two-phase cyclone centrifugal separation device 08, the oily sewage is subjected to oil-water rapid high-efficiency separation by virtue of a centrifugal force (more than 1500 g), an oil phase in the sewage is discharged to a dirty oil system through a three-stage separation oil phase output pipeline 09, the sewage enters a four-stage functional oil-water two-phase coalescence demulsification separation device 11 through a three-stage separation water phase output pipeline 10 to treat the oil and the suspended solid, so that small oil drops are coalesced into large oil drops to be conveniently removed, the suspended solid is subjected to coagulation treatment by utilizing a nano ceramic polar coating filler, the hydrophobic and oleophobic, hydrophilic and oleophobic and oleophilic hydrophobic mixed combined filler with polar characteristics can be used for physical demulsification and three-phase critical resolution, and favorable separation conditions are created for the next-stage high-efficiency cyclone gas treatment, the separated oil phase is discharged to a sump oil system through a four-stage separation oil phase output pipeline 12, the separated water phase enters a five-stage functional oil-water two-phase cyclone air flotation separation device 14 through a four-stage separation water phase output pipeline 13, the produced water is subjected to deep high-efficiency oil-water separation and synchronous suspended matter removal in high-efficiency cyclone air flotation under the double actions of cyclone and air flotation, the separated oil phase is discharged to the sump oil system through a five-stage separation oil phase output pipeline 15, the redundant associated air flotation gas is discharged to a gas system through a five-stage separation associated gas output pipeline 16, the five-stage separation associated gas circulating air flotation pipeline 17 realizes the recycling of most flotation gas, and the separated oil-containing sewage reaches the C3 water quality (can meet the discharge requirement of all domestic sea areas) and then enters a fine separation section through a five-stage separation water phase output pipeline 18.
Referring to fig. 2 and 5, the fine separation stage process includes: oily sewage (the oil content is less than 30ppm and the suspended solid is less than 10 ppm) entering the fine separation section firstly enters a six-stage functional oil-water two-phase fine filtering separation device 19, under the action of an activated mesoporous aluminosilicate filter material of a glass structure matrix, oil particles, suspended solid, crystallized salt particles, bacteria and the like in the water are deeply filtered, the filtered oil sludge, salt crystals and bacteria are discharged to an oil system through a six-stage separated oil phase output pipeline 20, the filtered water is discharged into a buffer water tank 22 through a six-stage separated water phase output pipeline 21, the buffer water tank 22 has certain buffer retention time and can receive unqualified circulating filtered water processed by a seven-stage functional oil-water ultrafiltration two-phase separation device 26, filtered water capable of keeping safety and stability is conveyed to a pre-ultrafiltration pressurization input pipeline 25 through a buffer water tank liquid phase output pipeline 23 to enter a seven-stage functional oil-water two-phase ultrafiltration separation device 26 for final ultrafiltration or nanofiltration separation, concentrated liquid generated by ultrafiltration is conveyed to an oil sludge system through a seven-stage separation oil sludge output pipeline 27, produced final qualified water is conveyed to a standard water injection buffer tank 29 through a seven-stage separation water phase output pipeline 28, partial standard water is used for self-cleaning or reflux dilution of the ultrafiltration separation device through a standard water injection circulation bypass 30, main standard water is conveyed to a standard water injection pressurization reinjection pipeline 32 through a standard water injection output pipeline 31, and the standard water is pressurized to the reinjection water pressure of each oil field and conveyed to a water injection wellhead for ultrahigh pressure reinjection.
The produced water can stably reach the A2 grade standard of the produced water (the oil content is less than 6.0mg/L, the solid suspended matter is less than 2.0mg/L, the median of the suspended matter particle diameter is less than 1.5 mu m) after two-stage deep filtration treatment of fine filtration and ultrafiltration, the A1 grade higher standard of the produced water (the oil content is less than 5.0mg/L, the solid suspended matter is less than 1.0mg/L, and the median of the suspended matter particle diameter is less than 1.0 mu m) can be realized under the high-quality water-based working condition, and the standard reinjection of the produced water treatment is finally completed. Referring to fig. 1, the produced liquid is 20-30% crude oil, the water content is 70-80%, and the material parameters in each treatment link are as follows:
further illustrating possible variations of the inventive solution: if the scheme of the invention is applied to the processing working condition that the gas content of the required separation medium is less, the first-stage function gas-liquid two-phase separation device can be omitted; if the device is applied to a treatment working condition that the oil content of a required separation medium is low, the secondary function oil-water two-phase hydrocyclone separation device or the four-stage function oil-water two-phase coalescence demulsification separation device can be omitted; if the device is applied to the treatment working condition that the required separation medium has more gas content and oil content, the primary function gas-liquid two-phase separation device can be replaced by a GLCC gas-liquid two-phase separator, and the quaternary function oil-water two-phase coalescence, demulsification and separation device can be replaced by an ultrasonic shock flotation separation device. The same effect can be achieved by the above method.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. Offshore oil field production water is handled on spot reinjection system on spot, its characterized in that: the device comprises seven-stage separation devices, namely a first-stage functional gas-liquid two-phase separation device, a second-stage functional oil-water two-phase hydrocyclone separation device, a third-stage functional oil-water two-phase hydrocyclone centrifugal separation device, a fourth-stage functional oil-water two-phase coalescence demulsification separation device, a fifth-stage functional oil-water two-phase cyclone air flotation separation device, a sixth-stage functional oil-water two-phase fine filtration separation device and a seventh-stage functional oil-water two-phase ultrafiltration separation device, wherein the seven-stage separation devices are sequentially connected through a pipeline, the seven-stage functional oil-water two-phase ultrafiltration separation device is further connected with a water injection buffer tank and a water injection pump, and liquid coming from offshore oilfield production enters the first-stage functional gas-liquid two-phase separation device, sequentially passes through the seven-stage separation device, the water injection buffer tank and the water injection pump and is finally injected back to a wellhead; the second-stage functional oil-water two-phase hydrocyclone separation device, the third-stage functional oil-water two-phase hydrocyclone centrifugal separation device, the fourth-stage functional oil-water two-phase coalescence demulsification separation device, the fifth-stage functional oil-water two-phase cyclone air flotation separation device, the sixth-stage functional oil-water two-phase fine filtration separation device and the seventh-stage functional oil-water two-phase ultrafiltration separation device are respectively connected with a sump oil storage tank, the sump oil storage tank is connected with a pressurization oil delivery pump, and the pressurization oil delivery pump is connected with an oil delivery system; the first-stage function gas-liquid two-phase separation device, the fifth-stage function oil-water two-phase cyclone air flotation separation device and the dirty oil storage tank are connected with a gas recovery device.
2. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein:
an inlet of the first-stage function gas-liquid two-phase separation device is connected with a production gas-liquid source input pipeline, an outlet at one end of the first-stage function gas-liquid two-phase separation device is connected with a first-stage separation associated gas output pipeline, and an outlet at the other end of the first-stage function gas-liquid two-phase separation device is connected with a first-stage separation liquid phase output pipeline; the first-stage separation liquid phase output pipeline is connected with an inlet of the second-stage function oil-water two-phase hydrocyclone separation device, an outlet at one end of the second-stage function oil-water two-phase hydrocyclone separation device is connected with a second-stage separation oil phase output pipeline, and an outlet at the other end of the second-stage function oil-water two-phase hydrocyclone separation device is connected with a second-stage separation water phase output pipeline;
the second-stage separation water phase output pipeline is connected with the inlet of the third-stage functional oil-water two-phase cyclone centrifugal separation device, the outlet at one end of the third-stage functional oil-water two-phase cyclone centrifugal separation device is connected with a third-stage separation oil phase output pipeline, and the outlet at the other end of the third-stage functional oil-water two-phase cyclone centrifugal separation device is connected with a third-stage separation water phase output pipeline; the three-stage separation water phase output pipeline is connected with an inlet of the four-stage functional oil-water two-phase coalescence demulsification separation device, an outlet at one side of the four-stage functional oil-water two-phase coalescence demulsification separation device is connected with a four-stage separation oil phase output pipeline, and an outlet at the other side of the four-stage functional oil-water two-phase coalescence demulsification separation device is connected with a four-stage separation water phase output pipeline; the four-stage separation water phase output pipeline is connected with an inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device, the five-stage function oil-water two-phase cyclone air-flotation separation device is provided with three outlets of an oil phase, a gas phase and a water phase, the oil phase outlet is connected with a five-stage separation oil phase output pipeline, the gas phase outlet is connected with a five-stage separation associated gas output pipeline, the water phase outlet is connected with a five-stage separation water phase output pipeline, and a five-stage separation associated gas circulating air-flotation pipeline is also connected between the gas phase outlet and the inlet of the five-stage function oil-water two-phase cyclone air-flotation separation device;
the five-stage separation water phase output pipeline is connected with an inlet of the six-stage functional oil-water two-phase fine filtering and separating device, an outlet at one end of the six-stage functional oil-water two-phase fine filtering and separating device is connected with a six-stage separation oil phase output pipeline, and an outlet at the other end of the six-stage functional oil-water two-phase fine filtering and separating device is connected with a six-stage separation water phase output pipeline; the device comprises a six-stage separation water phase output pipeline, a buffer water tank inlet, a buffer water tank liquid phase output pipeline, a pre-ultrafiltration pressurization input pipeline, a seven-stage functional oil-water two-phase ultrafiltration separation device inlet, a first end outlet of the seven-stage functional oil-water two-phase ultrafiltration separation device, a seven-stage separation oil sludge output pipeline, a second end outlet of the seven-stage separation oil-water two-phase ultrafiltration separation device, a circulating filtration return buffer water tank pipeline, a buffer water tank inlet, a seven-stage separation water phase output pipeline, a standard water injection buffer tank inlet, a standard water injection circulation bypass, a standard pre-ultrafiltration pressurization input pipeline, a standard water injection output pipeline, and a water injection pressurization reinjection pipeline.
3. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: the first-stage function gas-liquid two-phase separation device adopts a double-inclined lower inclined cyclone inlet, and a mist cyclone separation pipe is arranged in the first-stage function gas-liquid two-phase separation device.
4. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: the second-stage function oil-water two-phase hydrocyclone separation device adopts a high-kinetic energy hydrocyclone centrifugal separator, and a liquid-liquid hydrocyclone separation conical pipe is arranged in the cyclone separation device.
5. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: the three-stage function oil-water two-phase cyclone centrifugal separation device adopts a radial flow guiding high-speed cyclone pipe, and a radial flow guiding high-speed cyclone pipe is arranged in the device.
6. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: the four-stage functional oil-water two-phase coalescence demulsification separation device adopts three polarity combined fillers of hydrophilic oleophobic property, oleophilic hydrophobic property and hydrophobic oleophobic property of a nano ceramic home position coating.
7. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: the five-stage functional oil-water two-phase rotational flow air flotation separation device adopts the combination of double tangential centrifugal rotational flow and dissolved air pump micro-bubble flotation.
8. The offshore oilfield production water in-situ treatment and in-situ reinjection system of claim 1, wherein: according to the seven-stage functional oil-water two-phase ultrafiltration separation device, a core separation internal part adopts a hollow plate type ceramic membrane externally coated with a hydrophilic oleophobic nano coating, and adopts a filtering mode of external inlet and internal outlet and a backwashing mode of internal inlet and external outlet.
9. The offshore oilfield production water on-site treatment and on-site reinjection process is characterized in that: the process of the primary separation section is completed by a primary function gas-liquid two-phase separation device, a secondary function oil-water two-phase hydrocyclone separation device and matched pipelines thereof, and mainly removes discrete oil and free oil with the oil drop particle size of more than 100 microns; the high-efficiency separation section process is completed by a three-stage functional oil-water two-phase cyclone centrifugal separation device, a four-stage functional oil-water two-phase coalescence demulsification separation device, a five-stage functional oil-water two-phase cyclone air flotation separation device and matched pipelines thereof, and mainly removes dispersed oil and emulsified oil with the grain size of 10-100 microns of oil drops; the fine separation section process is completed by a six-stage functional oil-water two-phase fine filtering separation device, a seven-stage functional oil-water two-phase ultrafiltration separation device and matched pipelines thereof, and emulsified oil and dissolved oil with the grain size of 1-10 microns of oil drops are mainly removed; the oil-gas-water three-phase mixed medium at the wellhead of the offshore oil field is sequentially subjected to process treatment of a primary separation section, a high-efficiency separation section and a fine separation section, and finally the standard-reaching reinjection of the produced water treatment is completed.
10. The offshore oilfield production water in-situ treatment and in-situ reinjection process of claim 9, wherein:
the primary separation stage process comprises: the oil-gas-water three-phase mixed medium at the well head firstly passes through an input pipeline of a gas production liquid source head of each oil well, passes through a primary functional gas-liquid two-phase separation device, most of separated gas phase passes through a primary separation associated gas output pipeline to a gas system, a small part of associated gas is used as flotation gas of a five-stage functional oil-water two-phase cyclone gas-flotation separation device, and separated liquid phase passes through a primary separation liquid phase output pipeline and enters a secondary functional oil-water two-phase cyclone liquid separation device for primary oil-water separation; the oil and water in the liquid phase are rapidly separated in the hydrocyclone oil-water separator by means of a centrifugal force of over 1000g, the separated oil phase with the water content of less than 20 percent is discharged to an oil system through a secondary separated oil phase output pipeline, and the separated oily sewage enters a high-efficiency separation section through a secondary separated water phase output pipeline;
the high-efficiency separation section process comprises the following steps: the oily sewage which enters the high-efficiency separation section and contains less than 800ppm of oil and less than 300ppm of solid suspended matter firstly enters a three-stage functional oil-water two-phase rotational flow centrifugal separation device, the oily sewage is subjected to oil-water fast and high-efficiency separation by a centrifugal force larger than 1500g, an oil phase in the sewage is discharged to a dirty oil system through a three-stage separation oil phase output pipeline, the sewage enters a four-stage functional oil-water two-phase coalescence demulsification separation device through a three-stage separation water phase output pipeline to treat the oil and the suspended matter, so that small oil drops are coalesced into large oil drops to be conveniently removed, the suspended matter is subjected to coacervation treatment by utilizing a nano ceramic polar coating filler, the hydrophobic and oleophobic, hydrophilic and oleophobic and oleophilic hydrophobic mixed combined filler with polar characteristics can also be subjected to physical demulsification and three-phase critical resolution, creating favorable separation conditions for the next-stage high-efficiency cyclone gas flotation treatment, discharging the separated oil phase to a sump oil system through a fourth-stage separation oil phase output pipeline, discharging the separated water phase into a fifth-stage functional oil-water two-phase cyclone flotation separation device through a fourth-stage separation water phase output pipeline, performing deep high-efficiency oil-water separation and synchronous suspended matter removal on the produced water in the high-efficiency cyclone flotation by means of the dual functions of cyclone and flotation, discharging the separated oil phase to the sump oil system through a fifth-stage separation oil phase output pipeline, discharging the redundant associated flotation gas to a gas system through a fifth-stage separation associated gas output pipeline, realizing cyclic utilization of most flotation gas through the fifth-stage separation associated gas circulating flotation gas pipeline, and enabling the separated oil-containing sewage to reach water quality superior to C3 and then to enter a fine separation section through the fifth-stage separation water phase output pipeline;
the fine separation stage process comprises: the oil-containing sewage with oil content less than 30ppm and suspended solid less than 10ppm entering the fine separation section firstly enters a six-stage functional oil-water two-phase fine filtration separation device, under the action of an activated mesoporous aluminosilicate filter material of a glass structure matrix, oil particles, suspended solid, crystallized salt particles and bacteria in the water are deeply filtered, the filtered oil sludge, salt crystals and bacteria are discharged to an oil system through a six-stage separated oil phase output pipeline, the filtered water is discharged into a buffer water tank through a six-stage separated water phase output pipeline, the buffer water tank has certain buffer retention time, unqualified circulating filtered water processed by a seven-stage functional oil-water two-phase ultrafiltration separation device can be received, the filtered water capable of keeping safety and stability is conveyed to a pre-ultrafiltration pressurization input pipeline through a buffer water tank liquid phase output pipeline to enter a seven-stage functional oil-water two-phase ultrafiltration separation device for final ultrafiltration or ultrafiltration separation, concentrated liquid generated by ultrafiltration is conveyed to an oil sludge output pipeline to an oil sludge system through a seven-water phase separation pipeline, final qualified water is conveyed to a water injection buffer tank through a seven-stage separated water phase output pipeline, partial water separation bypass is used for separating dilution, and is self-cleaned, and returned to an ultrahigh pressure-regulated water injection pipeline, and the oil field pressure-injection water is returned to the oil-injected to reach the standard.
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