Oilfield sewage treatment method

Abstract

The invention relates to an oil field sewage treatment method, which comprises: stirring oil field sewage, and sequentially adding an activator, a pretreatment agent, a coagulant aid and a flocculant into the oil field sewage while stirring to obtain a mixed solution; wherein the activating agent has an oxidation effect, and the pretreating agent has a weighting effect. The activating agent has an oxidation effect, and ferrous ions in the oilfield sewage are oxidized into ferric ions; insoluble substances in the oilfield sewage form small-particle flocs through the coagulant aid; the flocculating agent enables small flocs generated by the coagulant aid to be coagulated and agglomerated into large flocs, the large flocs sink under the weighting effect of the pretreating agent, and the flocculating agent enables ferric ions to be flocculated into precipitates. Through the synergistic effect and the adding sequence of the activating agent, the pretreating agent, the coagulant aid and the flocculating agent, low-cost, simple and efficient treatment of the oilfield sewage is realized.

Description

Technical Field

[0001] The present application relates to the technical field of oil exploration and development, and in particular to a method for treating oilfield wastewater. Background Art

[0002] Injection water quality is an important technical indicator in the process of oil field development, which is directly related to the development level and effect of the oil field.

[0003] At present, the process of treating wastewater is complicated and economical. It is difficult to meet the quality standards of wastewater treatment, which causes serious corrosion and scaling to the back-end water injection system. After the unqualified wastewater is injected back into the ground, it causes serious damage to the production pipes and formations of the water injection wells, directly affecting the long-term stable production and efficient development of the oil field and increasing the mining cost. Summary of the invention

[0004] The present application provides a method for treating oilfield wastewater to solve the technical problem of high cost of existing oilfield wastewater treatment.

[0005] In a first aspect, the present application provides a method for treating oilfield wastewater, the method comprising:

[0006] The oilfield sewage is stirred, and while stirring, an activator, a pretreatment agent, a coagulant aid and a flocculant are sequentially added to the oilfield sewage to obtain a mixed solution; wherein,

[0007] The activator has an oxidizing effect, and the pre-treatment agent has an aggravating effect.

[0008] Optionally, the activator includes one of the following: sodium hypochlorite, ammonium persulfate, sodium perborate, and sodium percarbonate.

[0009] Optionally, the activator is 60 mg to 100 mg relative to 1 L of the oilfield wastewater.

[0010] Optionally, the pretreatment agent includes one of the following: sodium-based bentonite and calcium-based bentonite.

[0011] Optionally, relative to 1L of the oilfield wastewater, the pretreatment agent is 100mg to 200mg.

[0012] Optionally, the coagulant aid includes one of the following: polyaluminium chloride and polyaluminium ferric chloride.

[0013] Optionally, the coagulant aid is 30 mg to 50 mg relative to 1 L of the oilfield wastewater.

[0014] Optionally, the flocculant includes one of the following: anionic polyacrylamide and cationic polyacrylamide.

[0015] Optionally, the flocculant is 5 mg to 10 mg relative to 1 L of the oilfield wastewater.

[0016] Optionally, the mineralization of the oilfield wastewater is 160,000 mg / L to 200,000 mg / L.

[0017] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0018] The method for treating the oilfield sewage provided by the embodiment of the present application is to add the activator, pretreatment agent, coagulant and flocculant to the oilfield sewage in order under stirring; the activator has an oxidizing effect, oxidizing the divalent iron ions in the oilfield sewage into trivalent iron ions; the coagulant forms small particles of flocs from the insoluble matter in the oilfield sewage; the flocculant causes the small flocs produced by the coagulant to condense into large flocs, and sink under the weighting effect of the pretreatment agent, and the flocculant also causes the trivalent iron ions to flocculate into precipitation, and finally to a certain extent, the floc precipitation is completely separated from the water body, and the water body is clear. Through the synergistic effect of the activator, pretreatment agent, coagulant and flocculant and the order of addition, low-cost, simple and efficient treatment of oilfield sewage is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0021] Figure 1 A schematic diagram of a process for treating oilfield wastewater provided in an embodiment of the present application;

[0022] Figure 2 A diagram of an oilfield wastewater treatment process provided in an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0024] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0025] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present specification, the terms "including", "comprising", etc. refer to "including but not limited to". In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of the associated objects, indicating that there may be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A, B can be singular or plural. In this article, "at least one" refers to one or more, and "plural" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c", or "at least one of a, b and c", can both mean: a, b, c, ab (i.e. a and b), ac, bc or abc, where a, b, c can be single or plural, respectively.

[0026] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0027] In the first aspect, the present application provides a method for treating oilfield wastewater, see Figure 1 , the method comprising:

[0028] S1, stirring the oilfield sewage, and while stirring, adding an activator, a pretreatment agent, a coagulant aid and a flocculant to the oilfield sewage in sequence to obtain a mixed solution; wherein,

[0029] The activator has an oxidizing effect, and the pre-treatment agent has an aggravating effect.

[0030] In the present application embodiment, under stirring, activator, pretreatment agent, coagulant and flocculant are added to oilfield sewage in order; activator has oxidation, oxidizes divalent iron ions in oilfield sewage into trivalent iron ions; coagulant forms small particles of insoluble matter in oilfield sewage into floccules; flocculant makes the small flocs produced by coagulant coagulate into large flocs, and sinks under the aggravation of pretreatment agent, and flocculant also makes trivalent iron ions flocculate into precipitation, and finally realizes to a certain extent that floc precipitation is completely separated from water body, and water body is clear. If it is not added in the order of the above-mentioned agents, it may cause poor removal effect of divalent iron ions to a certain extent (because there is a requirement of divalent iron in water quality indicators), and if the order of addition is disrupted, large flocs can not be formed, and flocs can not sink, suspended in water, affecting the water effect. In addition, no air flotation machine is needed in the whole sewage treatment process, and standard water quality can be obtained by sinking of flocs.

[0031] In addition, in the above step S1, the stirring process parameters include: stirring temperature of 50°C to 60°C, stirring time of 0.5min to 2min, and stirring speed of 300r / min to 600r / min. For details, please refer to Figure 2 As shown in the oilfield wastewater treatment process diagram, under the above-mentioned mild stirring process conditions, and in combination with four chemical addition processes, a large number of flocs appeared in the wastewater. After stopping the stirring, the flocs settled rapidly. 60 seconds after stopping the stirring, the flocs and the water body were completely separated to a certain extent, and the water body was clear.

[0032] In some embodiments, the activator includes one of the following: sodium hypochlorite, ammonium persulfate, sodium perborate, sodium percarbonate.

[0033] In some embodiments, the activator is 60 mg to 100 mg relative to 1 L of the oilfield wastewater.

[0034] In the embodiment of the present application, one of sodium hypochlorite, ammonium persulfate, sodium perborate, and sodium percarbonate is selected as an activator, which plays a good oxidation role and oxidizes the divalent iron ions in the sewage into trivalent iron ions, so that the flocculant can flocculate it into precipitation, and a small amount can also play a good oxidation effect, while making the water clear. If other oxidants are used, the water may turn yellow. Preferably, the activator can be sodium percarbonate, and the water is clearer after treatment.

[0035] In the embodiment of the present application, the amount of activator added is controlled, and the divalent iron ions in the sewage are oxidized to trivalent iron ions under the action of an appropriate amount of activator, so that a good oxidation effect can be achieved, and the treatment cost of oilfield sewage can be controlled. If the amount of the activator added is too high, the oxidation effect of the divalent iron ions in the oilfield sewage is saturated to a certain extent, which leads to an increase in treatment cost; if the amount of the activator added is too low, the divalent iron ions in the sewage cannot have a good oxidation effect to a certain extent, and the excess divalent iron ions may cause the rear-end pipeline sulfate-reducing bacteria to grow. Specifically, relative to 1L of the above-mentioned oilfield sewage, the above-mentioned activator can be 60mg, 65mg, 70mg, 75mg, 80mg, 85mg, 90mg, 95mg, 100mg, etc.

[0036] In some embodiments, the pretreatment agent includes one of the following: sodium bentonite and calcium bentonite.

[0037] In some embodiments, the pretreatment agent is 100 mg to 200 mg relative to 1 L of the sewage.

[0038] In the embodiment of the present application, one of sodium bentonite and calcium bentonite is selected as the pretreatment agent, which plays a good weighting role, makes the flocculated flocs sink, and has a stronger oil absorption capacity. In addition, the amount of sodium bentonite or calcium bentonite is low, which can also play a good weighting role and save the processing cost. If the above bentonite is replaced with lime milk, the processing cost will increase significantly, and the amount of lime milk added will increase to 500mg~700mg / L.

[0039] In the embodiment of the present application, the amount of pretreatment agent added is controlled to control the amount of sludge generated, thereby controlling the treatment cost. If the amount of the pretreatment agent added is too high, the amount of sludge generated will be large to a certain extent, and the sludge will also need to be treated, increasing the treatment cost and making the water quality at the outlet turbid; if the amount of the pretreatment agent added is too low, it will be difficult to play a good weighting role to a certain extent, so the flocculated flocs will be difficult to sink and the oil absorption capacity will also decrease. Specifically, relative to 1L of the above-mentioned oilfield sewage, the above-mentioned pretreatment agent can be 100mg, 105mg, 110mg, 115mg, 120mg, 125mg, 130mg, 135mg, 140mg, 145mg, 150mg, 155mg, 160mg, 165mg, 170mg, 175mg, 180mg, 185mg, 190mg, 195mg, 200mg, etc.

[0040] In some embodiments, the coagulant aid includes one of the following: polyaluminium chloride, polyaluminium ferric chloride.

[0041] In some embodiments, the coagulant aid is 30 mg to 50 mg relative to 1 L of the sewage.

[0042] In the embodiment of the present application, one of polyaluminium chloride and polyaluminium ferric chloride is selected as a coagulant aid, which can make the insoluble matter in the sewage form small particle flocs and make the water clear.

[0043] In the embodiment of the present application, the amount of coagulant added is controlled to ensure that the insoluble matter in the sewage forms small particles of flocs, and the flocs sink, while making the water clear. If the amount of the coagulant added is too high, the flocs will float to a certain extent, and the water outlet will carry a large amount of flocs, resulting in substandard water quality; if the amount of the coagulant added is too low, although the flocs sink to a certain extent, the upper part of the water is not clear enough. Specifically, relative to 1L of the above-mentioned oilfield sewage, the above-mentioned coagulant can be 30mg, 32mg, 34mg, 36mg, 38mg, 40mg, 42mg, 44mg, 46mg, 48mg, 50mg, etc.

[0044] In some embodiments, the flocculant includes one of the following: anionic polyacrylamide and cationic polyacrylamide.

[0045] In some embodiments, the amount of the flocculant added is 5 mg to 10 mg relative to 1 L of the sewage.

[0046] In the embodiment of the present application, one of anionic polyacrylamide and cationic polyacrylamide is selected as the flocculant, so that the small flocs produced by the coagulant aid can be condensed and gathered into large flocs, and finally sink down.

[0047] In the embodiment of the present application, the amount of flocculant added is controlled to ensure that the small flocs generated by the coagulant aid are aggregated into large flocs and finally sink, while saving the processing cost. If the amount of the flocculant added is too high, it will increase the processing cost to a certain extent and make the water sticky; if the amount of the flocculant added is too low, to a certain extent, the small flocs generated will not condense tightly, the internal force of the large flocs will be weak, and the flocs will not be able to sink. Specifically, relative to 1L of the above-mentioned oilfield sewage, the above-mentioned flocculant can be 5mg, 5.5mg, 6mg, 6.5mg, 7mg, 7.5mg, 8mg, 8.5mg, 9mg, 9.5mg, 10mg, etc.

[0048] In some embodiments, the mineralization of the oilfield wastewater is 160,000 mg / L to 200,000 mg / L.

[0049] In the embodiment of the present application, the above-mentioned method for treating oilfield sewage can be applied to the sewage treatment of the joint station, and is particularly applicable to the water treatment of high-mineralization sewage of the joint station. The mineralization of the above-mentioned oilfield sewage can be 160000mg / L, 170000mg / L, 180000mg / L, 190000mg / L, 200000mg / L, etc. The oil content of the sewage after the treatment of the joint station can be ≤7mg / L, the organic impurities ≤8mg / L, the total iron ≤1mg / L, and the comprehensive water quality compliance rate is 100%.

[0050] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0051] The present application provides a method for treating oilfield wastewater, the method comprising:

[0052] S11, stirring the oilfield sewage, and while stirring, adding an activator, a pretreatment agent, a coagulant aid and a flocculant to the oilfield sewage in sequence to obtain a mixed solution; wherein,

[0053] The activator has an oxidizing effect, and the pretreatment agent has an aggravating effect. For specific process parameters, please refer to the types of agents shown in Table 1, the mineralization of oilfield wastewater and the amount of agents added shown in Table 2, and the stirring process for oilfield wastewater treatment shown in Table 3.

[0054] Table 1 Types of drugs

[0055]

[0056]

[0057] Table 2 Mineralization of oilfield wastewater and amount of reagent added

[0058]

[0059] Table 3 Mixing process for oilfield wastewater treatment

[0060] Serial number Stirring temperature ℃ Mixing time min Stirring speed r / min Example 1 60 0.5 300 Example 2 60 1 400 Example 3 60 1.5 500 Example 4 60 2 600

[0061] Comparative Example 1

[0062] The difference from Example 1 is that sodium bentonite is added first and then sodium percarbonate is added.

[0063] The mixed solution obtained by the oilfield wastewater treatment method adopted in Examples 1 to 3 and Comparative Example 1 was filtered to obtain a water body, and the water body was tested for water quality. The water quality test results are shown in Table 4.

[0064] Table 4 Water quality test results

[0065]

[0066] In the embodiment of the present application, the four kinds of agents, activator + pretreatment agent + coagulant aid + flocculant, are added in sequence, which has the characteristics of low cost and high performance. Specifically, the water quality test results in Table 1 show that the comprehensive water quality compliance rate is 100%.

[0067] The above-mentioned oilfield sewage treatment method embodiment 1 is applied to the water treatment of high-mineralization sewage at the joint station, and the sewage flocs are allowed to sink to solve the sewage treatment problem at the joint station. The comprehensive water quality compliance rate can reach 100%. For specific test results, please refer to Table 5.

[0068] Table 5 Combined station sewage treatment results

[0069]

[0070] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for treating oilfield wastewater, characterized in that: The method comprises: The oilfield sewage is stirred, and while stirring, an activator, a pretreatment agent, a coagulant aid and a flocculant are sequentially added to the oilfield sewage to obtain a mixed solution; wherein, The activator has an oxidizing effect, and the pre-treatment agent has an aggravating effect.

2. The method according to claim 1, characterized in that The activator includes one of the following: sodium hypochlorite, ammonium persulfate, sodium perborate, and sodium percarbonate.

3. The method according to claim 1 or 2, characterized in that: Relative to 1L of the oilfield wastewater, the activator is 60mg to 100mg.

4. The method according to claim 1, characterized in that: The pretreatment agent includes one of the following: sodium-based bentonite and calcium-based bentonite.

5. The method according to claim 1 or 4, characterized in that: The amount of the pretreatment agent is 100 mg to 200 mg relative to 1 L of the oilfield wastewater.

6. The method according to claim 1, characterized in that The coagulant aid includes one of the following: polyaluminium chloride and polyaluminium ferric chloride.

7. The method according to claim 1 or 6, characterized in that: Relative to 1L of the oilfield wastewater, the coagulant aid is 30mg to 50mg.

8. The method according to claim 1, characterized in that The flocculant includes one of the following: anionic polyacrylamide and cationic polyacrylamide.

9. The method according to claim 1 or 8, characterized in that: The amount of the flocculant is 5 mg to 10 mg relative to 1 L of the oilfield wastewater.

10. The method according to claim 1, characterized in that The mineralization degree of the oilfield wastewater is 160000 mg / L to 200000 mg / L.

Images