Treatment agents for oilfield produced fluid and their application in oilfield development

Abstract

The present invention provides a treatment agent for oilfield produced fluid and its application in oilfield development. The treatment agent for oilfield produced fluid includes a decalcifying agent, which includes 5 to 10 parts of soluble magnesium salt, 10 to 20 parts of soluble metaaluminate, 5 to 10 parts of soluble carbonate and 10 to 15 parts of chelating agent by weight. The soluble metaaluminate can inhibit the hydrolysis of bicarbonate ions and promote the ionization of bicarbonate ions. The soluble carbonate can combine with calcium ions in the produced fluid to generate calcium carbonate precipitation, which is adsorbed and removed by aluminum hydroxide colloid produced by the hydrolysis of metaaluminate, and the chelating agent can also capture calcium ions, and the synergistic effect of the two improves the stability of water quality. The soluble magnesium salt can adjust the ionic strength of the decalcifying agent system. The chelating agent can further improve the adsorption of calcium carbonate by the decalcifying agent, remove calcium carbonate scaling, and improve the stability of water quality. The treatment agent for oilfield produced fluid can also reduce the cost of sewage treatment.

Description

Technical Field

[0001] The invention relates to the technical field of scaling treatment of oilfield water injection systems, and in particular to a treatment agent for oilfield produced fluid and application thereof in oilfield development. Background Art

[0002] As the water content of produced fluid increases in oil fields, the problem of carbonate scaling becomes more prominent. The scaling of treatment station equipment and the scaling of injection systems caused by injection water quality have seriously affected oil field production. The calcium carbonate scaling problem encountered in oil field production can be roughly divided into two situations: (1) mixing with each other to produce precipitation, thereby causing scaling; (2) scaling caused by changes in temperature, pressure and other conditions. In response to the serious problem of calcium carbonate scaling in oil field production, researchers have proposed the following solutions: water softening treatment, addition of scale inhibitors, pH control and magnetization treatment.

[0003] The common method to inhibit calcium carbonate scaling is to soften the water, that is, to remove the Ca 2+ and HCO3 - or HCO 3- , but this method is suitable for circulating water systems. For oil field water injection systems with unidirectional water flow, the investment cost is relatively high.

[0004] Adding antiscalant and magnetizing water can change the form of scale so that it does not form hard scale that is difficult to remove. However, when water quality conditions change, such as the decrease in antiscalant concentration (loss of antiscalant and structural changes caused by hydrolysis at high temperature, etc.) or magnetized water after a long time, scale will still form. More importantly, the calcium carbonate crystals still existing in the water will damage the injection layer.

[0005] There are many reports on the use of ultrasonic treatment and the addition of scale inhibitors to inhibit the scaling tendency of calcium carbonate, but there is still a problem that calcium carbonate scaling cannot be completely eliminated.

[0006] On this basis, it is of great significance to develop a low-cost treatment agent that can completely solve the problem of calcium carbonate scaling. Summary of the invention

[0007] The main purpose of the present invention is to provide an oilfield produced fluid treatment agent and its application in oilfield development, so as to solve the problems of serious calcium carbonate scaling and high scaling treatment cost in the oilfield water injection system in the prior art.

[0008] In order to achieve the above-mentioned purpose, the present invention provides a treatment agent for oilfield produced fluid on one hand, the treatment agent for oilfield produced fluid includes a decalcifying agent, which includes 5 to 10 parts of a soluble magnesium salt, 10 to 20 parts of a soluble aluminate, 5 to 10 parts of a soluble carbonate and 10 to 15 parts of a chelating agent by weight.

[0009] Further, the chelating agent is selected from one or more of the group consisting of polyphosphate compounds, aminocarboxylic acid compounds, hydroxycarboxylic acid compounds, 1,3-diketone compounds and polyamine compounds; preferably, the polyphosphate compound is selected from sodium tripolyphosphate; the aminocarboxylic acid compound is selected from ethylenediaminetetraacetic acid and / or aminotriacetic acid; the hydroxycarboxylic acid compound is selected from dihydroxysuccinic acid and / or citric acid; the 1,3-diketone compound is selected from one or more of the group consisting of 2-amido-1,3-cyclohexanedione compounds, 2-alkyl-1,3-cyclohexanedione compounds and 2-alkylaryl-1,3-cyclohexanedione compounds; the polyamine compound is selected from aminobenzoic acid.

[0010] Furthermore, the decalcifying agent further comprises 1 to 5 parts by weight of a viscosity regulator.

[0011] Furthermore, the viscosity modifier is selected from sodium carboxymethyl cellulose; preferably, the molecular weight of sodium carboxymethyl cellulose is ≤10,000.

[0012] Furthermore, the treatment agent for oilfield produced fluid also includes a water purifier, which includes a first water purifier and / or a second water purifier; wherein, by weight, the first water purifier includes 30 to 50 parts of an inorganic polymer coagulant, 10 to 15 parts of a soluble zinc salt, 5 to 10 parts of a soluble magnesium salt and 1 to 5 parts of a cationic flocculant, and the pH of the first water purifier is 9 to 10; by weight, the second water purifier includes 70 to 75 parts of anionic polyacrylamide, 10 to 15 parts of an alkali metal inorganic salt and 5 to 10 parts of a solubilizer.

[0013] Furthermore, the inorganic polymer coagulant is selected from iron-containing polymer hydrochloride and / or aluminum-containing polymer hydrochloride, and the basicity of the inorganic polymer coagulant is 80-85%.

[0014] Furthermore, the cationic flocculant is selected from one or more of the group consisting of polydimethyldiallyl ammonium chloride, dimethyldiallyl ammonium chloride copolymer and chitosan; and the solubilizer is selected from urea.

[0015] Furthermore, the first water purifier further comprises 10 to 20 parts by weight of a complexing enhancer; preferably, the complexing enhancer is selected from aluminum oxide and / or ferric oxide.

[0016] Furthermore, the average viscosity average molecular weight of the anionic polyacrylamide is 7 to 8 million, and the alkali metal inorganic salt is selected from sodium chloride and / or potassium chloride.

[0017] In order to achieve the above-mentioned object, another aspect of the present invention further provides the use of the above-mentioned treatment agent for oilfield produced fluid in oilfield development.

[0018] By applying the technical solution of the present invention, since the above-mentioned decalcifying agent contains soluble aluminate, it can hydrolyze to produce hydroxide ions, thereby inhibiting the hydrolysis of bicarbonate ions, increasing the concentration of bicarbonate ions, and promoting the ionization of bicarbonate ions; at the same time, the above-mentioned decalcifying agent contains soluble carbonate, which can combine with calcium ions in the produced fluid to generate calcium carbonate precipitation, which is adsorbed and removed by aluminum hydroxide colloid produced by the hydrolysis of aluminate, and the chelating agent can also capture calcium ions in the produced fluid, and the synergistic effect of the two improves the stability of water quality. The use of soluble magnesium salt can adjust the ionic strength of the decalcifying agent system, neutralize the negative charge in the system, and make the entire decalcifying agent system electrically neutral. The use of chelating agent is also conducive to further improving the adsorption of calcium carbonate by the decalcifying agent, thereby removing calcium carbonate scaling in oilfield produced fluid, and thus improving water quality stability. In addition, the above-mentioned treatment agent for oilfield produced fluid can greatly reduce the cost of sewage treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 , Figure 2 and Figure 3 The ScaleChem scaling software is used in Example 1 to investigate the change in scaling amount before and after decalcification, and the predicted trend of scaling amount with changes in temperature and pressure; and

[0021] Figure 4 , Figure 5 and Figure 6 The ScaleChem scaling software used in Example 2 is used to examine the change in scaling amount before and after decalcification, as well as the predicted trend of scaling amount with changes in temperature and pressure. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0023] As described in the background technology, the existing oilfield water injection system has serious scaling problems of calcium carbonate and calcium sulfate. In order to solve the above technical problems, the present application provides a treatment agent for oilfield produced fluid, the treatment agent for oilfield produced fluid includes a decalcifying agent, and the decalcifying agent includes 5 to 10 parts of soluble magnesium salt, 10 to 20 parts of soluble aluminate, 5 to 10 parts of soluble carbonate and 10 to 15 parts of chelating agent by weight.

[0024] Since the above-mentioned decalcifying agent contains soluble aluminate, it can hydrolyze to produce hydroxide ions, thereby inhibiting the hydrolysis of bicarbonate ions, increasing the concentration of bicarbonate ions, and promoting the ionization of bicarbonate ions; at the same time, the above-mentioned decalcifying agent contains soluble carbonate, which can combine with calcium ions in the produced fluid to form calcium carbonate precipitation, which is adsorbed and removed by aluminum hydroxide colloid produced by the hydrolysis of aluminate, and the chelating agent can also capture calcium ions in the produced fluid. The synergistic effect of the two improves the stability of water quality. The use of soluble magnesium salt can adjust the ionic strength of the decalcifying agent system, neutralize the negative charge in the system, and make the entire decalcifying agent system electrically neutral. The use of chelating agents is also conducive to further improving the adsorption of calcium carbonate by the decalcifying agent, thereby removing calcium carbonate scaling in oilfield produced fluid, thereby improving water quality stability. In addition, the above-mentioned treatment agent for oilfield produced fluid can greatly reduce the cost of sewage treatment.

[0025] The ionic reaction equations involved in the above decalcification agents include:

[0026] Hydrolysis equilibrium of aluminate: AlO2 - +H2O→Al(OH)3(colloid)+OH -

[0027] Hydrolysis equilibrium of bicarbonate: HCO3 - +H2O→H2CO3+OH -

[0028] Ionization equilibrium of bicarbonate: HCO3 - →H + +CO3 2-

[0029] The addition of chelating agents can capture calcium ions in the produced fluid. In a preferred embodiment, the chelating agents include, but are not limited to, one or more of the group consisting of polyphosphate compounds, aminocarboxylic acid compounds, hydroxycarboxylic acid compounds, 1,3-diketone compounds and polyamine compounds. In order to further capture calcium ions in the produced fluid and reduce the concentration of calcium ions, preferably, polyphosphate compounds include, but are not limited to, sodium tripolyphosphate; aminocarboxylic acid compounds include, but are not limited to, ethylenediaminetetraacetic acid and / or aminotriacetic acid; hydroxycarboxylic acid compounds include, but are not limited to, dihydroxysuccinic acid and / or citric acid; 1,3-diketone compounds include, but are not limited to, one or more of the group consisting of 2-amido-1,3-cyclohexanedione compounds, 2-alkyl-1,3-cyclohexanedione compounds and 2-alkylaryl-1,3-cyclohexanedione compounds; polyamine compounds include, but are not limited to, aminobenzoic acid.

[0030] The viscosity modifier can adjust the viscosity of the decalcifying agent within a suitable range and improve the fluidity of the decalcifying agent. In a preferred embodiment, the decalcifying agent further comprises 1 to 5 parts of the viscosity modifier by weight. The use of the above-mentioned viscosity modifier in parts by weight can further increase the fluidity of the decalcifying agent.

[0031] In order to further improve the fluidity of the decalcifying agent and improve the removal rate of calcium carbonate scale, in a preferred embodiment, the viscosity modifier includes but is not limited to sodium carboxymethyl cellulose. In order to further adjust the viscosity of the decalcifying agent within a suitable range, thereby improving the fluidity of the decalcifying agent, preferably, the molecular weight of sodium carboxymethyl cellulose is ≤10000.

[0032] In a preferred embodiment, the treatment agent for the oilfield produced fluid also includes a water purifier, and the water purifier includes a first water purifier; wherein, by weight, the first water purifier includes 30 to 50 parts of an inorganic polymer coagulant, 10 to 15 parts of a soluble zinc salt, 5 to 10 parts of a soluble magnesium salt and 1 to 5 parts of a cationic flocculant, and the pH of the first water purifier is 9 to 10. By combining the decalcifying agent with the water purifier, the calcium carbonate scale and the suspended particles in the sewage can be quickly flocculated and settled together, and the scaling products and sludge can be removed, thereby shortening the sewage treatment cycle; at the same time, hydrogen sulfide can also be removed to achieve efficient desulfurization.

[0033] Among them, the addition of inorganic polymer coagulant can adsorb calcium carbonate precipitation, thereby removing calcium carbonate scaling in oilfield produced fluid, thereby improving water quality stability. The addition of soluble zinc salt can remove corrosive hydrogen sulfide contained in oilfield produced fluid and achieve sulfur removal. The addition of soluble magnesium salt can adjust the ionic strength of the water purifier system and neutralize the negative charge in the system. The addition of cationic flocculant can synergize with the inorganic polymer coagulant to further play the adsorption effect on calcium carbonate precipitation and reduce the scaling amount of calcium carbonate. Limiting the amount of inorganic polymer coagulant, soluble zinc salt, soluble magnesium salt and optional cationic flocculant to the above range, on the one hand, is conducive to adjusting the ionic strength of the first water purifier system within a suitable range, and at the same time, they work together to improve the adsorption effect on calcium carbonate precipitation and reduce the scaling amount of calcium carbonate; on the other hand, it is conducive to play the role of removing hydrogen sulfide, achieving sulfur removal and reducing the corrosiveness of produced fluid.

[0034] Limiting the pH of the first water purifier to the above range can enable the first water purifier to better adsorb and settle with the calcium carbonate precipitate, thereby reducing the amount of calcium carbonate scaling and improving water quality.

[0035] In a preferred embodiment, the treatment agent for the oilfield produced fluid also includes a water purifier, and the water purifier includes a second water purifier; by weight, the second water purifier includes 70-75 parts of anionic polyacrylamide, 10-15 parts of alkali metal inorganic salts and 5-10 parts of solubilizers. By combining the decalcifying agent with the water purifier, calcium carbonate scaling and suspended particles in sewage can be quickly flocculated and settled together, scaling products and sludge can be removed, thereby shortening the sewage treatment cycle; at the same time, hydrogen sulfide can also be removed to achieve efficient desulfurization.

[0036] Anionic polyacrylamide is a water-soluble high molecular polymer. Since its molecular chain contains polar amide groups, it can adsorb calcium carbonate precipitation particles suspended in water, causing the precipitation particles to condense into large flocs, thereby accelerating sedimentation and playing a role in purifying water quality. The addition of a solubilizer can make anionic polyacrylamide better dissolved in the second water purifier system, thereby enabling anionic polyacrylamide to play a role in purifying water quality. Limiting the amount of anionic polyacrylamide, alkali metal inorganic salt and solubilizer to the above range is, on the one hand, conducive to adjusting the ionic strength of the second water purifier within a suitable range, while allowing anionic polyacrylamide to be better dissolved therein; on the other hand, it is conducive to the flocculation and sedimentation of the calcium carbonate precipitation particles by the second water purifier, which is conducive to reducing the amount of calcium carbonate scaling and purifying water quality at the same time.

[0037] In a preferred embodiment, the inorganic polymer coagulant includes but is not limited to iron-containing polyhydrochloride and / or aluminum-containing polyhydrochloride, and the basicity of the inorganic polymer coagulant is 80-85%. Iron-containing polyhydrochloride and / or aluminum-containing polyhydrochloride can produce a variety of high-valent and multi-nuclear ions in water, which can electrolytically neutralize the colloidal particles suspended in the water to achieve the effect of purifying water.

[0038] Basicity is an indicator of the hydroxide ions in aluminum chloride, which is defined as the equivalent percentage of hydroxyl to aluminum in iron-containing polyhydrochloride or the equivalent percentage of hydroxyl to iron in aluminum-containing polyhydrochloride. Compared with other ranges, limiting the basicity of inorganic polymer coagulants to the above range is conducive to improving the flocculation and precipitation effect of inorganic polymer coagulants on calcium carbonate precipitation, thereby helping to reduce the amount of calcium carbonate scaling while purifying water quality.

[0039] In a preferred embodiment, the cationic flocculant includes, but is not limited to, one or more of the group consisting of polydimethyldiallyl ammonium chloride, dimethyldiallyl ammonium chloride copolymer and chitosan. The use of the above-mentioned cationic flocculants is beneficial to further exert the adsorption effect on calcium carbonate precipitation, and synergistically act with the inorganic polymer coagulant to reduce the scaling amount of calcium carbonate.

[0040] In a preferred embodiment, the solubilizer includes but is not limited to urea. The above-mentioned solubilizer has an amide group or an amino group. According to the principle of like dissolves like, the use of the above-mentioned solubilizer can further promote the dissolution of anionic polyacrylamide in the second water purifier system, thereby further facilitating the anionic polyacrylamide to purify water quality.

[0041] In a preferred embodiment, the first water purifier further comprises 10 to 20 parts by weight of a complexing enhancer. The use of a complexing enhancer can make the chelating agent have a stronger chelating effect, thereby improving the stability of the product. In order to further improve the stability of the product, preferably, the complexing enhancer includes but is not limited to aluminum oxide and / or ferric oxide.

[0042] In a preferred embodiment, the average viscosity average molecular weight of the anionic polyacrylamide is 7 to 8 million, and the alkali metal inorganic salt includes but is not limited to sodium chloride and / or potassium chloride. Limiting the average molecular weight of the anionic polyacrylamide to the above range is conducive to further playing the role of purifying water quality.

[0043] The second aspect of the present application also provides an application of the above-mentioned treatment agent for oilfield produced fluid in oilfield development. The use of a decalcifying agent can form a calcium carbonate precipitate and capture calcium ions in the produced fluid, thereby improving the stability of the water quality. By combining the decalcifying agent with a water purifier, the calcium carbonate scale and suspended particles in the sewage can be quickly flocculated and settled together, and the scaling products and sludge can be removed, thereby shortening the sewage treatment cycle; at the same time, hydrogen sulfide can also be removed to achieve efficient desulfurization. In addition, the application of the above-mentioned treatment agent for oilfield produced fluid in oilfield development can greatly reduce the cost of sewage treatment.

[0044] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0045] Example 1

[0046] This product formula is suitable for low concentration Ca 2+ (<300mg / L), high concentration of HCO3 - (>1000mg / L) of oily wastewater scale control. Among them, by weight, the decalcifying agent includes 5 parts of industrial grade magnesium chloride (Xinrui Advanced Chemicals), 10 parts of sodium aluminate, 10 parts of sodium carbonate, 1 part of sodium carboxymethyl cellulose (molecular weight of 10000), 5 parts of chelating agent (wherein, the weight ratio of ethylenediaminetetraacetic acid and aminotriacetic acid is 2:1), and the remaining 69 parts are water, and the pH value regulator is used to control the pH of the decalcifying agent to 10.5; by weight, the first water purifier includes 40 parts of polyaluminium chloride PAC (basicity 82%), 2 parts of polydimethyldiallyl ammonium chloride, 10 parts of zinc chloride, and the remaining 48 parts are water, and the pH of the first water purifier is 9.5; by weight, the second water purifier includes 1 part of anionic polyacrylamide, 5 parts of sodium chloride, 5 parts of urea, and the remaining 89 parts are water.

[0047] (1) Preparation of decalcifying agent: 10 parts of aluminate and 10 parts of carbonate were stirred with water at 30°C for 30 minutes until they were uniformly mixed to obtain a mixed solution; the mixed solution was uniformly stirred with 5 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), and then aged for 4 hours; the mixed solution obtained after aging was mixed with sodium carboxymethyl cellulose to finally obtain a decalcifying agent.

[0048] (2) Preparation of the first water purifier: PAC and a pH regulator were mixed and subjected to a homogenization polymerization reaction for 1 hour to obtain a homogenized polymerization product; 10 parts of zinc chloride were then added and stirred for 0.5 hours to react; 2 parts of polydimethyldiallylammonium chloride were then added and subjected to a composite reaction to obtain the first water purifier.

[0049] (3) Preparation of the second water purifier: Disperse 1 part of anionic polyacrylamide in water to form a 1% dispersion, and mature it for 24 hours. Mix 5 parts of sodium chloride and 5 parts of urea with the matured anionic polyacrylamide dispersion, and stir until uniform to obtain the second water purifier.

[0050] (4) The beaker test method was used to investigate the change in the amount of scale before and after decalcification. In a beaker containing 1000 mL of oily wastewater, 100 mg / L or 200 mg / L of decalcifying agent was first added, and the impeller was stirred evenly for about 30 minutes. Then, under rapid stirring conditions (the speed gradient G value was 200 s -1 ) Add 200 mg / L of the first water purifier and react for 3 minutes, then add 10 mg / L of the second water purifier and continue to react for 3 minutes under stirring, stop stirring, let it stand for 30 minutes, and obtain a supernatant. Take the supernatant for analysis.

[0051] like Figure 1 , Figure 2 and Figure 3 As shown in the figure, ScaleChem scaling software is used to investigate the change of scaling amount before and after decalcification, as well as the predicted trend of scaling amount with changes in temperature and pressure. Figure 1 It is the oilfield produced fluid without adding decalcifying agent. Figure 2 The oilfield produced fluid was treated with 100mg / L decalcifying agent. Figure 3 It is the oilfield produced fluid treated with 200 mg / L decalcifying agent. Figure 1 The middle curve (a1) represents the CaCO3 scaling content, the curve (b1) represents the CaCO3 scaling trend, the curve (c1) represents the CaSO4·2H2O scaling trend, and the curve (d1) represents the CaSO4 scaling trend; Figure 2 The middle curve (a2) indicates the CaCO3 scaling content, curve (b2) indicates the scaling trend of CaSO4·2H2O, curve (c2) the scaling trend of CaSO4, and curve (d2) the scaling trend of CaCO3; Figure 3 The middle curve (a3) ​​represents the CaCO3 scaling content, the curve (b3) represents the CaCO3 scaling trend, the curve (c3) represents the CaSO4·2H2O scaling trend, and the curve (d3) represents the CaSO4 scaling trend. The results show that: after treatment, Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 60%.

[0052] Example 2

[0053] The difference from Example 1 is that, by weight, the decalcifying agent includes 5 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), 15 parts of sodium aluminate, 10 parts of sodium carbonate, 2 parts of sodium carboxymethyl cellulose (molecular weight of 10,000), 5 parts of chelating agent (the weight ratio of ethylenediaminetetraacetic acid to aminotriacetic acid is 2:1), and the remaining 53 parts are water, and the pH of the decalcifying agent is controlled to be 10.5 by a pH regulator; by weight, the first water purifier includes 40 parts of polyaluminium chloride PAC (basicity 82%), 1 part of polydimethyldiallylammonium chloride, 10 parts of zinc chloride, and the remaining 48 parts are water, and the pH of the first water purifier is 10; by weight, the second water purifier includes 1 part of anionic polyacrylamide, 7 parts of sodium chloride, 5 parts of urea, and the remaining 88 parts are water.

[0054] like Figure 4 , Figure 5 and Figure 6 As shown in the figure, ScaleChem scaling software is used to investigate the change of scaling amount before and after decalcification, as well as the predicted trend of scaling amount with changes in temperature and pressure. Figure 4 The carbonate scaling trend of the incoming liquid from the oil field field treatment station, Figure 5 The produced fluid was treated with 100mg / L decalcifying agent and the injection pressure was 16MPa. Figure 6 The produced fluid is treated with 200mg / L decalcifying agent and the injection pressure is 19MPa; and Figure 4 The middle curve (a4) represents the CaCO3 scaling content, curve (b4) represents the CaCO3 scaling trend, curve (c4) represents the CaSO4·2H2O scaling trend, and curve (d4) represents the CaSO4 scaling trend; Figure 5 The middle curve (a5) indicates the CaCO3 scaling content, curve (b5) indicates the scaling trend of CaSO4·2H2O, curve (c5) the scaling trend of CaSO4, and curve (d5) the scaling trend of CaCO3; Figure 6 The middle curve (a6) represents the CaCO3 scaling content, the curve (b6) represents the CaCO3 scaling trend, the curve (c6) represents the CaSO4·2H2O scaling trend, and the curve (d6) represents the CaSO4 scaling trend.

[0055] Scaling trend of purified water in on-site water injection system Figure 4 In comparison, after adding 200 mg / L of the above decalcifying agent, the calcium carbonate scaling amount in the water was reduced by 210 mg / L and 215 mg / L respectively under the conditions of injection pressure of 16 MPa and 19 MPa and formation temperature of about 70°C, and the calcium carbonate removal rate was 59% and 61% respectively.

[0056] Example 3

[0057] The difference from Example 1 is that, by weight, the decalcifying agent includes 10 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), 20 parts of sodium aluminate, 5 parts of sodium carbonate, 10 parts of chelating agent (the weight ratio of ethylenediaminetetraacetic acid to aminotriacetic acid is 2:1), and the remaining 55 parts are water.

[0058] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 55%.

[0059] Example 4

[0060] The difference from Example 1 is that, by weight, the decalcifying agent includes 10 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), 20 parts of sodium aluminate, 5 parts of sodium carbonate, 15 parts of chelating agent (the weight ratio of ethylenediaminetetraacetic acid to aminotriacetic acid is 2:1), and the remaining 55 parts are water.

[0061] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 57%.

[0062] Example 5

[0063] The difference from Example 1 is that, by weight, the decalcifying agent includes 10 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), 20 parts of sodium aluminate, 5 parts of sodium carbonate, 20 parts of chelating agent (the weight ratio of ethylenediaminetetraacetic acid to aminotriacetic acid is 2:1), and the remaining 55 parts are water.

[0064] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 52%.

[0065] Example 6

[0066] The difference from Example 1 is that, by weight, the decalcifying agent includes 5 parts of industrial-grade magnesium chloride (Xinrui Advanced Chemicals), 10 parts of sodium aluminate, 10 parts of sodium carbonate, 5 parts of sodium carboxymethyl cellulose, and the remaining 70 parts are water.

[0067] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 56%.

[0068] Example 7

[0069] The difference from Example 1 is that sodium carboxymethyl cellulose is not added.

[0070] The results showed that the treated water had Ca 2+and HCO3 - The ion content was reduced and the decalcification rate was 52%.

[0071] Example 8

[0072] The difference from Example 1 is that the molecular weight of sodium carboxymethyl cellulose is 30,000.

[0073] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 56%.

[0074] Example 9

[0075] The difference from Example 1 is that, by weight, the first water purifier includes 30 parts of polyaluminium chloride PAC, 10 parts of zinc chloride, 10 parts of soluble magnesium chloride, 1 part of polydimethyldiallyl ammonium chloride, and the remaining 39 parts are water, and the pH of the first water purifier is 10.

[0076] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 58%.

[0077] Example 10

[0078] The difference from Example 1 is that, by weight, the first water purifier includes 50 parts of polyaluminium chloride PAC, 10 parts of zinc chloride, 5 parts of soluble magnesium chloride, 5 parts of polydimethyldiallyl ammonium chloride, and the remaining 30 parts are water, and the pH of the first water purifier is 10.

[0079] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 60%.

[0080] Embodiment 11

[0081] The difference from Example 1 is that, by weight, the first water purifier includes 20 parts of polyaluminium chloride PAC, 15 parts of zinc chloride, 15 parts of soluble magnesium chloride, 10 parts of polydimethyldiallyl ammonium chloride, and the remaining 40 parts are water, and the pH of the first water purifier is 5.

[0082] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 56%.

[0083] Example 12

[0084] The difference from Example 1 is that, by weight, the second water purifier includes 70 parts of anionic polyacrylamide, 10 parts of sodium chloride, 10 parts of urea, and the remaining 10 parts are water.

[0085] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 59%.

[0086] Example 13

[0087] The difference from Example 1 is that, by weight, the second water purifier includes 75 parts of anionic polyacrylamide, 15 parts of sodium chloride, 5 parts of urea, and the remaining 5 parts are water.

[0088] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 59%.

[0089] Embodiment 14

[0090] The difference from Example 1 is that, by weight, the second water purifier includes 50 parts of anionic polyacrylamide, 1 part of sodium chloride, 1 part of urea, and the remaining 48 parts are water.

[0091] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 58%.

[0092] Embodiment 15

[0093] The difference from Example 1 is that the basicity of the inorganic polymer coagulant polyaluminium chloride is 80%.

[0094] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 60%.

[0095] Example 16

[0096] The difference from Example 1 is that the basicity of the inorganic polymer coagulant polyaluminium chloride is 85%.

[0097] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 61%.

[0098] Embodiment 17

[0099] The difference from Example 1 is that the basicity of the inorganic polymer coagulant polyaluminium chloride is 40%.

[0100] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 45%.

[0101] Embodiment 18

[0102] The difference from Example 1 is that the inorganic polymer coagulant is ferrous polymer hydrochloride.

[0103] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 56%.

[0104] Embodiment 19

[0105] The difference from Example 1 is that the chelating agent is ethylenediaminetetraacetic acid.

[0106] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 59%.

[0107] Embodiment 20

[0108] The difference from Example 1 is that the first water purifier also includes 10 parts of a complexing enhancer, aluminum oxide.

[0109] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 58%.

[0110] Embodiment 21

[0111] The difference from Example 1 is that the first water purifier also includes 20 parts of a complexing enhancer, aluminum oxide.

[0112] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 58%.

[0113] Embodiment 22

[0114] The difference from Example 1 is that the average viscosity average molecular weight of the anionic polyacrylamide is 7 million.

[0115] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 59%.

[0116] Embodiment 23

[0117] The difference from Example 1 is that the average viscosity average molecular weight of the anionic polyacrylamide is 8 million.

[0118] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 58%.

[0119] Embodiment 24

[0120] The difference from Example 1 is that the average viscosity average molecular weight of the anionic polyacrylamide is 3 million.

[0121] The results showed that the treated water had Ca 2+ and HCO3 - The ion content was significantly reduced, and the decalcification rate was 40%.

[0122] Comparative Example 1

[0123] The difference from Example 1 is that a scale inhibitor is added. The performance test results of different scaling control technologies in Comparative Example 1 and the Example are shown in Table 1.

[0124] Table 1

[0125]

[0126] Comparative Example 2

[0127] The difference from Example 1 is that no soluble magnesium salt and soluble metaaluminate are added.

[0128] The results showed that the decalcification rate was 40.5%.

[0129] Comparative Example 3

[0130] The difference from Example 1 is that no chelating agent and soluble carbonate are added.

[0131] The results showed that the decalcification rate was 45.6%.

[0132] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0133] Comparing Examples 1 to 5 and Comparative Examples 1 to 3, it can be seen that the technical solution of the present application is adopted, because the above-mentioned decalcifying agent contains soluble aluminate, which can be hydrolyzed to produce hydroxide ions, thereby inhibiting the hydrolysis of bicarbonate ions, increasing the concentration of bicarbonate ions, and promoting the ionization of bicarbonate ions; at the same time, the above-mentioned decalcifying agent contains soluble carbonate, which can combine with calcium ions in the produced fluid to form calcium carbonate precipitation, thereby being adsorbed and removed by aluminum hydroxide colloid produced by the hydrolysis of aluminate, and the chelating agent can also capture calcium ions in the produced fluid, and the synergistic effect of the two improves the water quality stability together. The use of soluble magnesium salt can adjust the ionic strength of the decalcifying agent system, neutralize the negative charge in the system, and make the entire decalcifying agent system electrically neutral. The use of a chelating agent is also conducive to further improving the adsorption of calcium carbonate by the decalcifying agent, thereby removing calcium carbonate scaling in the oilfield produced fluid, and thus improving the water quality stability.

[0134] Comparison of Examples 1, 6 and 7 shows that limiting the amount of the viscosity modifier to within the preferred range of the present application can further increase the fluidity of the decalcifying agent.

[0135] Comparing Examples 1 and 8, it can be seen that the molecular weight of sodium carboxymethyl cellulose is limited to the preferred range of the present application, and the viscosity of the decalcifying agent is further adjusted to a suitable range, thereby improving the fluidity of the decalcifying agent.

[0136] By comparing Examples 1, 9 to 11, it can be seen that limiting the dosage of the inorganic polymer coagulant, the soluble zinc salt, the soluble magnesium salt and the optional cationic flocculant within the above range is, on the one hand, beneficial for adjusting the ionic strength of the first water purifier system within an appropriate range, while working together to enhance the adsorption of calcium carbonate precipitation and reduce the amount of calcium carbonate scaling; on the other hand, it is beneficial for removing hydrogen sulfide, achieving sulfur removal and reducing the corrosiveness of the produced fluid.

[0137] By comparing Examples 1, 12 to 14, it can be seen that limiting the amounts of anionic polyacrylamide, alkali metal inorganic salt and solubilizer to the above range is, on the one hand, beneficial for adjusting the ionic strength of the second water purifier within an appropriate range while allowing the anionic polyacrylamide to be better dissolved therein; on the other hand, it is beneficial for the second water purifier to have a flocculation and sedimentation effect on the calcium carbonate precipitate particles, which is beneficial for reducing the amount of calcium carbonate scaling while purifying the water quality.

[0138] By comparing Examples 1 and 15 to 17, it can be seen that, compared with other ranges, limiting the basicity of the inorganic polymer coagulant within the preferred range of the present application is beneficial to improving the flocculation and precipitation effects of the inorganic polymer coagulant on calcium carbonate precipitation, thereby helping to reduce the amount of calcium carbonate scaling while purifying water quality.

[0139] By comparing Examples 1 and 18, it can be seen that iron-containing polyhydrochloride and / or aluminum-containing polyhydrochloride can generate a variety of high-valent and polynuclear ions in water, and these ions can electrolytically neutralize the colloidal particles suspended in the water to achieve the effect of purifying water.

[0140] Comparing Examples 1 and 19, it can be seen that the use of the preferred type of chelating agent in the present application is beneficial to further capture calcium ions in the produced fluid and reduce the calcium ion concentration.

[0141] Comparison of Examples 1, 20 and 21 shows that the use of the preferred types and dosage ranges of the complexing enhancer in the present application is beneficial to improving the stability and decalcification effect of the product.

[0142] Comparing Examples 1 and 22 to 24, it can be seen that limiting the average viscosity-average molecular weight of anionic polyacrylamide to the preferred range of the present application is beneficial to further exerting the water purification effect of anionic polyacrylamide.

[0143] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those described herein, for example.

[0144] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A treatment agent for oilfield produced fluid, characterized in that: The treatment agent for the oilfield produced fluid includes a decalcifying agent, which includes 5 to 10 parts of a soluble magnesium salt, 10 to 20 parts of a soluble aluminate, 5 to 10 parts of a soluble carbonate and 10 to 15 parts of a chelating agent in parts by weight; the treatment agent for the oilfield produced fluid also includes a water purifying agent, which includes a first water purifying agent and / or a second water purifying agent; wherein, in parts by weight, the first water purifying agent includes 30 to 50 parts of an inorganic polymer coagulant, 10 to 15 parts of a soluble zinc salt, 5 to 10 parts of a soluble magnesium salt and 1 to 5 parts of cationic flocculant, the pH of the first water purifier is 9-10; by weight, the second water purifier includes 70-75 parts of anionic polyacrylamide, 10-15 parts of alkali metal inorganic salt and 5-10 parts of solubilizer; the average viscosity-average molecular weight of the anionic polyacrylamide is 7-8 million, and the alkali metal inorganic salt is selected from sodium chloride and / or potassium chloride; by weight, the decalcifying agent also includes 1-5 parts of viscosity regulator; by weight, the first water purifier also includes 10-20 parts of complexing enhancer.

2. The treatment agent for oilfield produced fluid according to claim 1, wherein the chelating agent is selected from one or more of the group consisting of polyphosphate compounds, aminocarboxylic acid compounds, hydroxycarboxylic acid compounds, 1,3-diketone compounds and polyamine compounds; The polyphosphate compound is selected from sodium tripolyphosphate; The aminocarboxylic acid compound is selected from ethylenediaminetetraacetic acid and / or aminotriacetic acid; The hydroxycarboxylic acid compound is selected from dihydroxysuccinic acid and / or citric acid; The 1,3-diketone compound is selected from one or more of the group consisting of 2-amido-1,3-cyclohexanedione compounds, 2-alkyl-1,3-cyclohexanedione compounds and 2-alkylaryl-1,3-cyclohexanedione compounds; The polyamine compound is selected from aminobenzoic acid.

3. The treatment agent for oilfield produced fluid according to claim 1, characterized in that: The viscosity modifier is selected from sodium carboxymethyl cellulose; the molecular weight of the sodium carboxymethyl cellulose is ≤10000.

4. The treatment agent for oilfield produced fluid according to claim 1, characterized in that: The inorganic polymer coagulant is selected from iron-containing polymer hydrochloride and / or aluminum-containing polymer hydrochloride, and the basicity of the inorganic polymer coagulant is 80-85%.

5. The treatment agent for oilfield produced fluid according to claim 1, characterized in that: The cationic flocculant is selected from one or more of the group consisting of polydimethyldiallylammonium chloride, dimethyldiallylammonium chloride copolymer and chitosan; and the solubilizer is selected from urea.

6. The treatment agent for oilfield produced fluid according to claim 1, characterized in that: The complexing enhancer is selected from aluminum oxide and / or ferric oxide.

7. Use of the treatment agent for oilfield produced fluid according to any one of claims 1 to 6 in oilfield development.

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