A purification device and purification method for oilfield reinjection water

Abstract

This invention relates to a purification device and method for oilfield reinjection water, specifically in the field of water treatment technology. The purification device includes: a gas-liquid separator, an inertization reaction device, a crystallization separation device, a solid-liquid separation device, and a slurry storage device connected in sequence; the inlet of the gas-liquid separator is connected to the oilfield reinjection water supply end; the inertization reaction device is equipped with a pH adjuster inlet, a scale inhibitor inlet, and an oxidant inlet; the gas outlet of the crystallization separation device is connected in sequence to a steam compressor, a condenser, and a water tank; the slurry storage device is connected to the water tank. This invention's oilfield reinjection water purification device can achieve oxidation and scale removal of high-temperature, high-salinity reinjection water. By utilizing the coupled treatment effect between the various devices, it improves the treatment efficiency and effect of the reinjection water, realizes the integrated assembly of the system, reduces the difficulty of on-site installation and maintenance, and supports the development and production increase of oilfields with mixed clean and polluted water injection and low-permeability oilfields.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a purification device and method for oilfield reinjection water, and more particularly to an oxidation and descaling device and method for high-temperature, high-salinity oilfield reinjection water. Background Technology

[0002] Currently, the proportion of water injection in oilfield production is on the rise. Water injection can replenish losses caused by formation fluid production, restore formation pressure, and ensure smooth production. In some water-scarce areas, it is necessary to use a mixed injection method involving clean and polluted water. However, due to differences in water quality from different sources, chemical reactions often occur after mixing, producing precipitates or scaling substances that are difficult to remove, thereby damaging the reservoir and reducing reservoir permeability.

[0003] Before mixing water, a compatibility analysis is first conducted to determine the incompatible factors and the composition of the precipitates. Typically, the scaling substances are calcium carbonate, calcium sulfate, strontium sulfate, barium sulfate, ferrous sulfide, etc. However, because the dissolved oxygen in the clean water is high and it contains some microorganisms such as sulfate-reducing bacteria, while the extracted water has extremely high levels of chloride ions and sulfate ions, mixing them will increase the risk of corrosion.

[0004] Currently, the main method to solve the scaling and corrosion problems in mixed reinjection water is to pretreat the clean water and wastewater separately. The main purpose is to remove oil and suspended matter. After the clean water and wastewater are mixed separately, scale inhibitors, corrosion inhibitors, bactericides, oxygen removers and other agents are added to solve the scaling and corrosion problems in the reinjection process.

[0005] Traditionally, the main process for treating wastewater (produced water) is based on oil separation-coagulation (flotation)-filtration. For clean water, sand removal-filtration is generally used. However, due to the high temperature and extremely high mineralization of produced water and source well water, it is difficult to remove scaling ions using traditional chemical dosing flocculation sedimentation methods. Therefore, a large amount of chemicals is added at the outlet to prevent scaling. This method has the following problems:

[0006] 1) Due to the salt effect in the water, the dosage of the chemical is much greater than the theoretical dosage, and the chemical composition is complex, mostly organic polymers, which damages the reservoir.

[0007] 2) Although the addition of scale inhibitors avoids homogeneous crystallization, it is difficult to avoid heterogeneous crystallization. In the complex flow field environment of the formation, scaling is still difficult to avoid.

[0008] 3) The dosage is difficult to control, and it needs to be determined by repeated tests when the water quality and quantity change;

[0009] 4) The treatment effect is unstable.

[0010] In summary, current reinjection water treatment methods still suffer from poor treatment effects, the treated reinjection water can still harm the reservoir, and scaling still occurs during use. Therefore, there is an urgent need to develop an environmentally friendly water treatment process to solve the problem of scale removal in the treatment of mixed clean and contaminated reinjection water, and to provide technical support for increasing and stabilizing production in oilfields with mixed clean and contaminated injection. Summary of the Invention

[0011] In view of the problems existing in the prior art, the purpose of the present invention is to provide a purification device and purification method for oilfield reinjection water, so as to solve the problem of scale removal in the treatment of mixed clean and dirty reinjection water, and provide technical support for increasing and stabilizing production in oilfields with mixed clean and dirty water injection.

[0012] To achieve this objective, the present invention adopts the following technical solution:

[0013] In a first aspect, the present invention provides a purification device for oilfield reinjection water, the purification device comprising:

[0014] The equipment consists of a gas-liquid separation unit, an inertization reaction unit, a crystallization separation unit, a solid-liquid separation unit, and a slurry storage unit connected in sequence.

[0015] The inlet of the gas-water separator is connected to the oilfield reinjection water supply end;

[0016] The inertization reaction equipment is equipped with a pH adjuster inlet, a scale inhibitor inlet, and an oxidant inlet;

[0017] The outlet of the crystallization separation equipment is connected in sequence to a steam compression device, a condenser, and a water tank;

[0018] The slurry storage device is connected to the water tank.

[0019] The purification device for oilfield reinjection water in this invention can achieve oxidation and descaling of high-temperature and high-salt reinjection water. By utilizing the coupled treatment effects of gas-water separation equipment, inertization reaction equipment, crystallization separation equipment, and solid-liquid separation equipment, the treatment efficiency and effect of reinjection water are improved. The integrated assembly of the system reduces the difficulty of on-site installation and maintenance, and supports the development and production increase of oilfields with mixed clean and dirty water injection and low-permeability oilfields.

[0020] As a preferred embodiment of the present invention, the liquid outlet of the gas-liquid separation device is connected to the feed port of the inertization reaction device;

[0021] Preferably, the outlet of the inertization reaction equipment is connected to the inlet of the crystallization separation equipment;

[0022] Preferably, the outlet of the crystallization separation device is connected to the inlet of the solid-liquid separation device;

[0023] Preferably, the outlet of the solid-liquid separation device is connected to the inlet of the slurry storage device.

[0024] As a preferred technical solution of the present invention, the connection channel between the inertization reaction equipment and the crystallization separation equipment is equipped with a temperature detection device and a heating device;

[0025] Preferably, the slurry storage device is connected to the electrolysis unit;

[0026] Preferably, the material outlet of the electrolysis unit is connected to the oxidant inlet.

[0027] Secondly, the present invention provides a method for purifying oilfield reinjection water, the purification method comprising:

[0028] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0029] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0030] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0031] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0032] The condensate and slurry are mixed to obtain reinjection water.

[0033] As a preferred technical solution of the present invention, the temperature of the oilfield reinjection water is 50-100℃.

[0034] Preferably, the oilfield reinjection water is CaCl2-NaCl type reinjection water with a chloride ion content of 20-150 g / L and Ca... 2+ Content mmol / L > SO 2 4 - Content in mmol / L.

[0035] As a preferred embodiment of the present invention, the oxidant used in the inertization treatment includes sodium hypochlorite solution.

[0036] Preferably, the pH of the solution is controlled to be 9-11 after the inertization treatment with the addition of an oxidant.

[0037] Preferably, a scale inhibitor is added during the inertization treatment.

[0038] Preferably, the concentration of the scale inhibitor in the liquid phase during the inertization treatment is 2-4 ppm.

[0039] As a preferred technical solution of the present invention, the temperature of the material fed in the crystallization separation is ≥80℃.

[0040] Preferably, seed crystals are added during the crystallization separation.

[0041] Preferably, the seed crystals used in the crystallization separation include one or a combination of at least two of calcium sulfate, calcite, or iron oxide.

[0042] Preferably, the amount of seed crystals added in the crystallization separation is 2-10 g / L.

[0043] As a preferred technical solution of the present invention, the crystallization separation operation temperature is 105-120℃.

[0044] Preferably, the concentration factor in the crystallization separation is: Concentration factor Among them, Q i Q is the influent flow rate, m³ / h; R Q is the reflux slurry flow rate, m³ / h; R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i m 3 / h; C is the sulfate ion concentration in the slurry, mg / L.

[0045] As a preferred embodiment of the present invention, the concentration of chloride ions in the slurry is ≥100g / L.

[0046] Preferably, the slurry is divided into a first slurry and a second slurry, and the first slurry is mixed with condensate as reinjection water.

[0047] As a preferred embodiment of the present invention, the second slurry is electrolyzed.

[0048] Preferably, the voltage of the electrolysis is 3-4V.

[0049] Preferably, the current density of the electrolysis is 280-350 A / m. 2 .

[0050] Compared with existing technical solutions, the present invention has the following beneficial effects:

[0051] (1) The present invention provides a solution that, through the design of a treatment device for oilfield reinjection water, can achieve deoxygenation and sterilization effects while removing scale-forming ions, thus greatly solving the problem of incompatibility between clean and wastewater reinjection. Through the cooperation of various devices, the heat and salinity of the incoming water are fully utilized, reducing the addition of chemicals, improving treatment efficiency and effect, and possessing environmentally friendly advantages, which is conducive to the development and production increase of oilfields with mixed clean and wastewater injection.

[0052] (2) The processing method of the present invention is applicable to treating high temperature (50-100℃) and high salt (chloride ion content 20-150g / L, Ca) conditions.2+ Content mmol / L > SO 2 4 - This treatment process utilizes the inherent thermal energy and salinity of groundwater in the CaCl2-NaCl type produced water or source water within the concentration range of mmol / L. By extracting steam to create a slight negative pressure and concentrating the slurry through electrolysis, a self-oxidizing and self-evaporating crystallization system is formed, greatly reducing the consumption of steam heat source and reagents. At the same time, considering the extremely high sulfate and calcium ion content of produced water and source water, seed crystals are added in the evaporation crystallization unit to cause scale-forming substances to crystallize heterogeneously, thereby reducing the risk of scale blockage in water injection equipment pipelines and reservoirs.

[0053] (3) Most of the salt in the reinjected water after treatment is removed, and the oxygen content in the water is ≤0.05mg / L, which greatly reduces the corrosion rate and reduces the addition of scale inhibitors, corrosion inhibitors and oxygen removers. It is an environmentally friendly treatment process. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of a purification device for oilfield reinjection water provided in an embodiment of the present invention.

[0055] In the diagram: 1-Gas-water separation equipment, 1.1-Oilfield reinjection water supply end, 1.2-Separated gas output end, 2-Inertization reaction equipment, 2.1-pH adjuster inlet end, 2.2-Scale inhibitor inlet end, 2.3-Oxidant inlet end, 3-Crystallization separation equipment, 3.1-Heating equipment, 3.2-Steam compression equipment, 3.3-Condensation equipment, 4-Solid-liquid separation equipment, 4.1-Solid salt output end, 5-Slurry storage equipment, 5.1-Water tank, 5.2-Electrolysis unit.

[0056] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0057] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0058] This embodiment provides a purification device for oilfield reinjection water, such as... Figure 1 As shown, the purification device includes:

[0059] The following components are connected in sequence: gas-liquid separation equipment 1, inertization reaction equipment 2, crystallization separation equipment 3, solid-liquid separation equipment 4, and slurry storage equipment 5.

[0060] The inlet of the gas-water separation device 1 is connected to the oilfield reinjection water supply end 1.1;

[0061] The inertization reaction equipment 2 is equipped with a pH adjuster inlet 2.1, a scale inhibitor inlet 2.2, and an oxidant inlet 2.3;

[0062] The outlet of the crystallization separation device 3 is connected in sequence to the steam compression device 3.2, the condenser 3.3 and the water tank 5.1;

[0063] The slurry storage device 5 is connected to the water tank 5.1.

[0064] The liquid outlet of the gas-liquid separation device 1 is connected to the feed port of the inertization reaction device 2.

[0065] In this invention, the reinjected water refers to water that is reinjected into the oilfield, such as produced water from the oilfield, or source well water, or a mixture of both, etc., that meets the treatment requirements, specifically high temperature (50-100℃) and high salinity (chloride ion content 20-150g / L, Ca... 2+ Content mmol / L > SO 2 4 - Aqueous solution with a concentration of mmol / L.

[0066] In this invention, the gas obtained from the gas output end 1.2 of the gas-water separation device 1 can be fed into other processes through pipelines for reasonable utilization based on the gas properties.

[0067] In this invention, after the reinjected water is separated by the gas-water separation device 1, gases that affect the subsequent treatment process, such as combustible gases and carbon dioxide in the water, can be removed, thereby ensuring the smooth progress of the subsequent reaction. This is because the presence of non-condensable gases and carbon dioxide can affect the boiling point of the liquid and cause corrosion and scaling problems in the equipment, which would prevent the purification process of this invention from achieving the desired effect.

[0068] In this invention, the water enters the inertization reaction device 2, where, under the combined action of the pH adjuster, oxidant, and scale inhibitor, the ferrous ions in the water are oxidized to Fe. 3+ The ions also act as bactericides, expand the metastable region of calcium sulfate, and prevent slightly soluble substances such as calcium sulfate in water from forming homogeneous crystals, which would otherwise cause scaling on the surface of equipment and pipelines, affecting thermal efficiency and causing blockages.

[0069] In this invention, the water after the oxidation reaction is fed into the crystallization separation device 3. Steam in the crystallization separation device 3 is extracted by a steam compressor or heat pump, creating a slight negative pressure in the separator chamber, such as a saturated steam pressure ≥80 kPa. Part of the extracted steam enters the front-end heating device 3.1, such as a heat exchanger, to heat the incoming water, while the remaining steam is sent to the condenser 3.3. Seed crystals are added to the crystallization separation device 3. During the circulating evaporation process, slightly soluble substances such as calcium sulfate and strontium sulfate in the water precipitate on the surface of the seed crystals, forming whiskers, thus preventing scale buildup from adhering to the equipment and pipe walls. As the water evaporates, the crystals gradually grow, creating a binding and precipitation effect on colloidal substances such as Fe(OH)3 and Mg(OH)2 in the water. The bound crystalline salts and colloidal substances are discharged with the concentrated slurry to the solid-liquid separation device 4.

[0070] In this invention, after separation by the solid-liquid separation device 4, solid salt is output from the solid salt output end 4.1, and after processing, it can be used in other processes.

[0071] The outlet of the inertization reaction device 2 is connected to the inlet of the crystallization separation device 3.

[0072] The outlet of the crystallization separation device 3 is connected to the inlet of the solid-liquid separation device 4.

[0073] The liquid outlet of the solid-liquid separation device 4 is connected to the feed inlet of the slurry storage device 5.

[0074] The connection channel between the inertization reaction device 2 and the crystallization separation device 3 is equipped with a temperature detection device and a heating device 3.1 to ensure the temperature of the material fed into the crystallization separation device 3. The heating device 3.1 can be a direct heating device or a heat exchange heating device. The heat source for the heat exchange heating device can be the hot gas produced by the crystallization separation device 3 after being compressed by the steam compression device 3.2. If the liquid phase temperature after treatment by the inertization reaction device 2 is ≥80℃, it can be directly fed into the crystallization separation device 3, i.e., without heating.

[0075] The slurry storage device 5 is connected to the electrolysis unit 5.2.

[0076] The material outlet of the electrolysis unit 5.2 is connected to the oxidant inlet 2.3.

[0077] In this invention, a portion of the slurry storage device 5 enters the electrolysis unit 5.2, and the remaining portion is mixed with the condensate in the water tank 5.1 and used as oilfield reinjection water. The amount of slurry fed into the electrolysis unit 5.2 is designed based on the concentration of divalent iron in the reinjection water and the theoretical usage of oxidant.

[0078] In this invention, after the slurry in the slurry storage device 5 is fed into the electrolysis unit 5.2, the slurry is electrolyzed to generate oxidizing substances such as active chlorine and hydroxyl radicals, which are then fed into the inertization reaction device 2 by the oxidant feed end 2.3 as oxidant raw materials for use, thus reducing the consumption of reagents.

[0079] Furthermore, the present invention provides a method for purifying oilfield reinjection water, the purification method comprising:

[0080] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0081] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0082] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0083] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0084] The condensate and slurry are mixed to obtain reinjection water.

[0085] The temperature of the oilfield reinjection water is 50-100℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃ or 100℃, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0086] The oilfield reinjection water is of the CaCl2-NaCl type, with a chloride ion content of 20-150 g / L. 2+ Content mmol / L > SO 2 4 - Content in mmol / L.

[0087] In this invention, the chloride ion content in the oilfield reinjection water is 20-150 g / L, for example, it can be 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0088] The oxidant used in the inertization treatment includes sodium hypochlorite solution.

[0089] The sodium hypochlorite solution used can be replaced by the material after electrolysis in electrolysis unit 5.2 of this invention, thereby realizing the recycling of materials.

[0090] The amount of oxidant added in the inertization treatment is determined based on the content of ferrous ions in the reinjection water to ensure complete oxidation of ferrous ions in the reinjection water.

[0091] In this process, after adding the oxidant, the pH value of the solution is controlled to be 9-11. For example, it can be 9, 9.2, 9.4, 9.6, 9.8, 10, 10.2, 10.4, 10.6, 10.8 or 11, but it is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0092] The inertization process includes the addition of a scale inhibitor.

[0093] The scale inhibitor can be any commercially available scale inhibitor commonly used in the field.

[0094] The concentration of the scale inhibitor in the liquid phase during the inertization treatment is 2-4 ppm, for example, it can be 2 ppm, 2.2 ppm, 2.4 ppm, 2.6 ppm, 2.8 ppm, 3 ppm, 3.2 ppm, 3.4 ppm, 3.6 ppm, 3.8 ppm or 4 ppm, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0095] The temperature of the material fed into the crystallization separation process is ≥80℃, for example, it can be 80℃, 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃, 98℃ or 100℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0096] Seed crystals are added during the crystallization separation process.

[0097] The seed crystals used in the crystallization separation include one or a combination of at least two of calcium sulfate, calcite, or iron oxide.

[0098] The amount of seed crystals added in the crystallization separation is 2-10 g / L, for example, it can be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0099] The crystallization separation operation temperature is 105-120℃, for example, it can be 105℃, 106℃, 107℃, 108℃, 109℃, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃ or 120℃, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0100] The concentration factor in the crystallization separation is: Concentration factor Among them, Q i Q represents the influent flow rate. R Q is the reflux slurry flow rate. R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i C represents the sulfate ion concentration in the slurry.

[0101] In this invention, controlling the concentration factor ensures the electrolysis efficiency during the self-oxidation of the slurry, thereby ensuring the concentration of oxidation products and thus allowing the oxidation feed water to be recycled.

[0102] In this invention, the amount of oxidant added in the concentration factor calculation is the theoretical amount of oxidant (NaClO), which can be obtained in advance through beaker experiments.

[0103] The concentration of chloride ions in the slurry is ≥100g / L, for example, it can be 100g / L, 120g / L, 140g / L, 160g / L, 180g / L, 200g / L, 220g / L, 240g / L, 260g / L, 280g / L or 300g / L, etc., but is not limited to the listed values. Other unlisted values ​​within this range also meet the requirements.

[0104] The slurry is divided into a first slurry and a second slurry. The first slurry is mixed with condensate water to serve as reinjection water.

[0105] The second slurry is electrolyzed.

[0106] The electrolysis voltage is 3-4V, for example, it can be 3V, 3.1V, 3.2V, 3.3V, 3.4V, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V or 4V, but is not limited to the listed values. Other unlisted values ​​within this range are also acceptable.

[0107] The current density of the electrolysis is 280-350 A / m. 2 For example, it could be 280A / m 2 285A / m 2 290A / m 2 295A / m 2 300A / m 2 305A / m 2 310A / m 2 315A / m 2 320A / m 2 325A / m 2 330A / m2 335A / m 2 340A / m 2 345A / m 2 Or 350A / m 2 The values ​​may include, but are not limited to, the listed values; other unlisted values ​​within this range also meet the requirements.

[0108] In this invention, the electrolyte solution obtained after electrolysis is returned to the inertization process and used as an oxidant and pH adjuster, replacing sodium hypochlorite solution and pH adjuster. The amount of electrolyte returned is determined based on the concentration of divalent iron in the oilfield reinjection water.

[0109] The slurry used in electrolysis mainly consists of saturated sodium chloride and a small amount of calcium chloride, and undergoes the following reaction upon electrolysis:

[0110] NaCl + H₂O → NaClO + H₂↑

[0111] CaCl2+2H2O→Ca(OH)2+Cl2↑+H2↑

[0112] The reaction produces sodium hypochlorite and calcium hydroxide, which are then returned to the inertization process and added as an oxidant and pH adjuster.

[0113] In this invention, the purification method for oilfield reinjection water preferably uses the oilfield reinjection water purification device provided above, which is beneficial for the good matching of the process and the device, so that the purification process can be carried out stably and efficiently. However, it is not excluded that other devices in the art can be used to carry out the purification method of the invention or other methods in the art can be used to utilize the device of the invention.

[0114] Furthermore, to illustrate the effects that the reinjected water obtained by the purification device and method provided by the present invention can achieve, a practical example is used for explanation, as follows:

[0115] In the following examples, the reinjection water to be purified is reinjection water from an oilfield in the Middle East. It contains ferrous ions, and when mixed with production water, it produces black ferrous sulfide precipitate, failing to meet the requirements for reinjection water. Simultaneously, the water has extremely high mineralization, exhibiting a severe tendency for CaSO4 and SrSO4 scaling, and Cl... - The concentration is extremely high, which affects the coagulation and sedimentation effect. The main ion concentrations are shown in Table 1 below.

[0116] Table 1

[0117]

[0118]

[0119] Example 1

[0120] This embodiment provides a method for purifying oilfield reinjection water, the purification method comprising:

[0121] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0122] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0123] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0124] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0125] The condensate and slurry are mixed to obtain reinjection water.

[0126] The oxidant used in the inertization treatment is sodium hypochlorite solution; the pH value of the solution is controlled at 10.5 after the oxidant is added in the inertization treatment; a scale inhibitor is added in the inertization treatment; the scale inhibitor is Luv-4005 corrosion and scale inhibitor, purchased from Shandong Youwei Environmental Protection Technology Co., Ltd.; the concentration of the scale inhibitor in the liquid phase in the inertization treatment is 3 ppm.

[0127] The temperature of the material fed into the crystallization separation is 90℃; seed crystals are added in the crystallization separation; the seed crystals used in the crystallization separation are calcium sulfate; the amount of seed crystals added in the crystallization separation is 8g / L;

[0128] The crystallization separation process is carried out at a temperature of 115°C; the concentration factor during the crystallization separation is... Concentration factor Q i Q represents the influent flow rate. R Q is the reflux slurry flow rate. R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i C is the concentration of sulfate ions in the slurry, and the calculated concentration factor is 2.

[0129] The chloride ion concentration in the slurry is 120 g / L; the slurry is divided into a first slurry and a second slurry, the first slurry is mixed with condensate as reinjection water; the second slurry is electrolyzed; the electrolysis voltage is 3.8 V; the electrolysis current density is 300 A / m 2 The electrolyzed material is returned to inertization treatment and used as an oxidant.

[0130] The dissolved oxygen in the purified condensate is 0.02 mg / L. When mixed with slurry and used as reinjection water, no deoxygenating agent needs to be added, achieving good purification and separation of oilfield reinjection water and significantly improving the utilization effect of oilfield reinjection water.

[0131] Example 2

[0132] This embodiment provides a method for purifying oilfield reinjection water, the purification method comprising:

[0133] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0134] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0135] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0136] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0137] The condensate and slurry are mixed to obtain reinjection water.

[0138] The oxidant used in the inertization treatment is sodium hypochlorite solution; the pH value of the solution is controlled at 10 after the oxidant is added in the inertization treatment; a scale inhibitor is added in the inertization treatment; the scale inhibitor is X-101 general-purpose corrosion and scale inhibitor, purchased from Qingdao Xinyuyuan Water Treatment Technology Co., Ltd.; the concentration of the scale inhibitor in the liquid phase in the inertization treatment is 2.5 ppm;

[0139] The temperature of the material fed into the crystallization separation is 80℃; seed crystals are added in the crystallization separation; the seed crystals used in the crystallization separation are calcium sulfate; the amount of seed crystals added in the crystallization separation is 5g / L;

[0140] The crystallization separation process is carried out at a temperature of 110°C; the concentration factor during the crystallization separation is... Concentration factor Q i Q represents the influent flow rate. R Q is the reflux slurry flow rate. R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i C is the concentration of sulfate ions in the slurry, and the calculated concentration factor is 2.

[0141] The chloride ion concentration in the slurry is 100 g / L; the slurry is divided into a first slurry and a second slurry, the first slurry is mixed with condensate as reinjection water; the second slurry is electrolyzed; the electrolysis voltage is 3.5 V; the electrolysis current density is 325 A / m. 2 The electrolyzed material is returned to inertization treatment and used as an oxidant.

[0142] The dissolved oxygen in the purified condensate is 0.01 mg / L. When mixed with slurry and used as reinjection water, no deoxygenating agent needs to be added, achieving good purification and separation of oilfield reinjection water and significantly improving the utilization effect of oilfield reinjection water.

[0143] Example 3

[0144] This embodiment provides a method for purifying oilfield reinjection water, the purification method comprising:

[0145] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0146] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0147] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0148] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0149] The condensate and slurry are mixed to obtain reinjection water.

[0150] The oxidant used in the inertization treatment is sodium hypochlorite solution; the pH value of the solution is controlled at 11 after the oxidant is added in the inertization treatment; a scale inhibitor is added in the inertization treatment; the scale inhibitor is X-101 general-purpose corrosion and scale inhibitor, purchased from Qingdao Xinyuyuan Water Treatment Technology Co., Ltd.; the concentration of the scale inhibitor in the liquid phase in the inertization treatment is 2 ppm;

[0151] The temperature of the material fed into the crystallization separation is 95℃; seed crystals are added in the crystallization separation; the seed crystals used in the crystallization separation are calcium sulfate; the amount of seed crystals added in the crystallization separation is 2g / L;

[0152] The crystallization separation process is carried out at a temperature of 120°C; the concentration factor during the crystallization separation is... Concentration factor Q i Q represents the influent flow rate. R Q is the reflux slurry flow rate. R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i C is the concentration of sulfate ions in the slurry, and the calculated concentration factor is 2.

[0153] The chloride ion concentration in the slurry is 150 g / L; the slurry is divided into a first slurry and a second slurry, the first slurry is mixed with condensate as reinjection water; the second slurry is electrolyzed; the electrolysis voltage is 4V; the electrolysis current density is 280 A / m 2The electrolyzed material is returned to inertization treatment and used as an oxidant.

[0154] The relevant indicators of the aqueous phase obtained in each step of the purification process are detailed in Table 2.

[0155] The dissolved oxygen in the purified condensate is 0.012 mg / L. When mixed with slurry and used as reinjection water, no deoxygenating agent needs to be added, achieving good purification and separation of oilfield reinjection water and significantly improving the utilization effect of oilfield reinjection water.

[0156] Example 4

[0157] This embodiment provides a method for purifying oilfield reinjection water, the purification method comprising:

[0158] The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution;

[0159] The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry;

[0160] The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt;

[0161] The steam generated during the crystallization separation is compressed and condensed to obtain condensate.

[0162] The condensate and slurry are mixed to obtain reinjection water.

[0163] The oxidant used in the inertization treatment is sodium hypochlorite solution; the pH value of the solution is controlled to be 9 after the oxidant is added in the inertization treatment; a scale inhibitor is added in the inertization treatment; the scale inhibitor is Luv-4005 corrosion and scale inhibitor, purchased from Shandong Youwei Environmental Protection Technology Co., Ltd.; the concentration of the scale inhibitor in the liquid phase in the inertization treatment is 4 ppm.

[0164] The temperature of the material fed into the crystallization separation is 85℃; seed crystals are added in the crystallization separation; the seed crystals used in the crystallization separation are calcium sulfate; the amount of seed crystals added in the crystallization separation is 10g / L;

[0165] The crystallization separation process is carried out at a temperature of 105°C; the concentration factor during the crystallization separation is... Concentration factor Q i Q represents the influent flow rate. R Q is the reflux slurry flow rate. R =Oxidant dosage × (1.252 - 5) × 10 -4 ×Q i C is the concentration of sulfate ions in the slurry, and the calculated concentration factor is 2.

[0166] The chloride ion concentration in the slurry is 120 g / L; the slurry is divided into a first slurry and a second slurry, the first slurry is mixed with condensate as reinjection water; the second slurry is electrolyzed; the electrolysis voltage is 3V; the electrolysis current density is 350 A / m. 2 The electrolyzed material is returned to inertization treatment and used as an oxidant.

[0167] The dissolved oxygen in the purified condensate is 0.015 mg / L. When mixed with slurry and used as reinjection water, no deoxygenating agent needs to be added, achieving good purification and separation of oilfield reinjection water and significantly improving the utilization effect of oilfield reinjection water.

[0168] In the above embodiments, the amount of oxidant added is determined based on the content of ferrous ions in the oilfield reinjection water according to the redox reaction equation, ensuring the oxidation of ferrous ions. It is hereby declared that the above embodiments illustrate the detailed structural features of the present invention, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0169] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0170] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0171] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A purification device for oilfield reinjection water, characterized in that, The purification device includes: The equipment consists of a gas-liquid separation unit, an inertization reaction unit, a crystallization separation unit, a solid-liquid separation unit, and a slurry storage unit connected in sequence. The inlet of the gas-water separator is connected to the oilfield reinjection water supply end; The inertization reaction equipment is equipped with a pH adjuster inlet, a scale inhibitor inlet, and an oxidant inlet; The outlet of the crystallization separation equipment is connected in sequence to a steam compression device, a condenser, and a water tank; The slurry storage device is connected to the water tank; The connection channel between the inertization reaction equipment and the crystallization separation equipment is equipped with a temperature detection device and a heating device; The slurry storage device is connected to the electrolysis unit; The material outlet of the electrolysis unit is connected to the oxidant inlet.

2. The purification device as described in claim 1, characterized in that, The liquid outlet of the gas-liquid separator is connected to the feed inlet of the inertization reaction device.

3. The purification device as described in claim 1, characterized in that, The outlet of the inertization reaction equipment is connected to the inlet of the crystallization separation equipment.

4. The purification device as described in claim 1, characterized in that, The discharge port of the crystallization separation device is connected to the inlet of the solid-liquid separation device.

5. The purification device as described in claim 1, characterized in that, The outlet of the solid-liquid separation device is connected to the inlet of the slurry storage device.

6. A method for purifying oilfield reinjection water, based on the oilfield reinjection water purification device according to any one of claims 1-5, characterized in that, The purification method includes: The oilfield reinjection water is subjected to gas-liquid separation to obtain a water-liquid solution; The resulting aqueous solution was subjected to inertization and crystallization separation in sequence to obtain a slurry; The obtained slurry was subjected to solid-liquid separation to obtain slurry and solid salt; The steam generated during the crystallization separation is compressed and condensed to obtain condensate. The condensate and slurry are mixed to obtain reinjection water.

7. The purification method as described in claim 6, characterized in that, The temperature of the reinjected water in the oilfield is 50-100℃.

8. The purification method as described in claim 6, characterized in that, The oilfield reinjection water is of the CaCl2-NaCl type, with a chloride ion content of 20-150 g / L. 2+ Content in mmol / L > Content in mmol / L.

9. The purification method as described in claim 6, characterized in that, The oxidant used in the inertization process includes sodium hypochlorite solution.

10. The purification method as described in claim 6, characterized in that, After the inertization treatment, the pH of the solution is controlled to be 9-11 after the addition of an oxidant.

11. The purification method as described in claim 6, characterized in that, The inertization process includes the addition of a scale inhibitor.

12. The purification method as described in claim 11, characterized in that, The concentration of the scale inhibitor in the liquid phase during the inertization treatment is 2-4 ppm.

13. The purification method as described in claim 6, characterized in that, The temperature of the material fed into the crystallization separation process is ≥80℃.

14. The purification method as described in claim 6, characterized in that, Seed crystals are added during the crystallization separation process.

15. The purification method as described in claim 14, characterized in that, The seed crystals used in the crystallization separation include one or a combination of at least two of calcium sulfate, calcite, or iron oxide.

16. The purification method as described in claim 14, characterized in that, The amount of seed crystals added in the crystallization separation is 2-10 g / L.

17. The purification method as described in claim 6, characterized in that, The crystallization separation operation temperature is 105-120℃.

18. The purification method as described in claim 6, characterized in that, The concentration of chloride ions in the slurry is ≥100g / L.

19. The purification method as described in claim 6, characterized in that, The slurry is divided into a first slurry and a second slurry. The first slurry is mixed with condensate water as reinjection water.

20. The purification method as described in claim 19, characterized in that, The second slurry is then electrolyzed.

21. The purification method as described in claim 20, characterized in that, The electrolysis voltage is 3-4V.

22. The purification method as described in claim 20, characterized in that, The current density of the electrolysis is 280-350 A / m. 2 .

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