Solid slow-release acid for plug removal operation of offshore oilfield and preparation method of solid slow-release acid

Abstract

The invention discloses a solid slow-release acid for offshore oilfield plug removal operation and a preparation method thereof.The preparation method comprises the steps that maleic anhydride, ester monomers, a cross-linking agent, an initiator and an organic solvent are mixed and subjected to a polymerization reaction in the nitrogen atmosphere, and an anhydride polymer is obtained; mixing and fully dissolving the alcohol compound, the polyvinyl alcohol and the anhydride polymer, and adding solid acid into the mixture for reaction to obtain the solid slow-release acid after the reaction is completed. The raw materials are easy to obtain, reaction conditions are mild, the process is simple and safe, and large-scale industrial production can be achieved; the prepared product has good compatibility with a conventional acidification blocking removal auxiliary agent, is convenient to store, transport and use, and meets the requirements of environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemistry, and in particular relates to a solid slow-release acid used for offshore oilfield plugging removal operations and a preparation method thereof. Background Art

[0002] With the rapid growth of the global economy, the demand for oil in various fields is increasing day by day, and it is particularly important to maximize the production of existing oil fields. Due to the complex chemical reactions or interactions between the well fluid and the reservoir fluid or reservoir rock, during the development of the oil field, the reservoir is often blocked by inorganic scaling, clay minerals, various mechanical impurities, asphaltene and colloidal sediments, resulting in reduced seepage capacity of the reservoir, which is not conducive to the efficient development of the oil field. In the development of offshore oil fields, the blockage of the reservoir is particularly serious due to the difficulty of pre-treatment of the well fluid and the large amount of injection. Therefore, it is of great significance to develop a deblocking working fluid suitable for offshore conditions.

[0003] As one of the most important unblocking technologies for offshore oil fields, acid unblocking is achieved by injecting acid into the formation to dissolve the blockage and some rock skeleton particles, so as to clear and improve the seepage channels of the formation. In addition, the acid can also be combined with an oxidant to enhance the effect of oxidative unblocking. At present, the commonly used unblocking acids on site include two types: liquid (hydrochloric acid, hydrofluoric acid, formic acid, etc.) and powder (aminosulfonic acid, chloroacetic acid, etc.). However, the above product forms bring great safety hazards to marine transportation, storage, operation, environmental protection, etc. In addition, the rapid dissolution of the above unblocking acid and the high acid concentration in the working fluid aggravate the corrosion of the pipe column. The above problems can be alleviated to a certain extent by isolating the solid acid from the outside world through the encapsulated acid prepared by the encapsulated material. Commonly used encapsulating materials include two categories, one is polysaccharide compounds such as starch and guar gum, and the other is resin materials such as polyvinyl acetate and polylactic acid. Among them, polysaccharide compounds are easy to carbonize during processing and dissolve too fast, which makes it impossible to achieve good sustained release. The resin materials have poor water solubility, resulting in more product residues.

[0004] Chinese invention patent CN 102533244A discloses a slow-release acid for oil and water well transformation capsule and its preparation method. The slow-release acid is composed of a solid acid capsule core and a slow-release support layer. The slow-release support layer includes a slow-release wall material (organic fatty acid or its derivative), a support wall material (acrylic resin or its derivative) and a binder (water-soluble plant gum or its derivative). The slow-release acid is a spherical particle with a particle size range of 0.15 to 0.25 mm. The slow-release acid can control the consumption of acid radical ions, but the preparation process is complicated, and the spherical particles cannot be added directly, and still need related equipment and devices for auxiliary addition.

[0005] Chinese invention patent CN 110028946A discloses a solid acid rod for water injection wells and its preparation and injection method. The solid acid rod is made of maleic acid-acrylic acid copolymer, ethyl acetate, water-soluble oleic acid imidazoline corrosion inhibitor, sodium α-olefin sulfonate, diethylenetriamine pentaacetic acid iron ammonium salt and polyvinyl acetate emulsion, wherein the weight percentage of each component is: maleic acid-acrylic acid copolymer 25%-35%, ethyl acetate 10%-20%, water-soluble oleic acid imidazoline corrosion inhibitor 10%-18%, sodium α-olefin sulfonate 5%-12%, diethylenetriamine pentaacetic acid iron ammonium salt 20%-30%, polyvinyl acetate emulsion 5%-15%. The solid acid rod is cylindrical and the injection method is simple, but the acid component in the solid acid rod is ethyl acetate, which can be hydrolyzed into acetic acid, the pH is only 3-4, and the ethyl acetate content accounts for only 10%-20%, and the acidification and plugging effect is limited. Summary of the invention

[0006] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a solid slow-release acid for offshore oil field plugging removal operation and a preparation method thereof.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing a solid slow-release acid for offshore oilfield plugging removal operations comprises the following steps:

[0009] (I) Preparation of anhydride polymer

[0010] Maleic anhydride, ester monomer, crosslinking agent, initiator and organic solvent are mixed and polymerized under nitrogen atmosphere to obtain anhydride polymer;

[0011] (II) Preparation of solid slow-release acid

[0012] The alcohol compound, polyvinyl alcohol and the anhydride polymer synthesized in step (I) are mixed and fully dissolved, and a solid acid is added to the mixture for reaction. After the reaction is completed, a solid slow-release acid is obtained.

[0013] In the above technical scheme, the temperature of the polymerization reaction in step (I) is controlled at 30°C to 80°C, preferably, the temperature of the polymerization reaction is controlled at 45°C to 70°C; the polymerization reaction time is 1h to 24h, preferably, the polymerization time is 3h to 15h.

[0014] In the above technical scheme, the mass ratio of maleic anhydride, ester monomer, crosslinking agent and organic solvent in step (I) is 1:(0.01-1):(0.0005-0.05):(1-20); preferably, the mass ratio of maleic anhydride, ester monomer, crosslinking agent and organic solvent is 1:(0.05-0.65):(0.001-0.025):(2-10).

[0015] In the above technical solution, the mass ratio of the organic solvent to the initiator in step (I) is 1:(0.0005-0.02), preferably, the mass ratio of the organic solvent to the initiator is 1:(0.001-0.015).

[0016] In the above technical scheme, the ester monomer in step (I) is any one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate or hexyl methacrylate, or a mixture of two or more thereof.

[0017] In the above technical scheme, the initiator in step (I) is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutylimidazoline hydrochloride or azoisobutylcyanoformamide.

[0018] In the above technical scheme, the organic solvent in step (I) is any one of toluene, xylene, ethyl acetate, acetone, butanone, tetrahydrofuran or cyclohexane, or a mixture of two or more thereof.

[0019] In the above technical solution, the chemical structural formula of the cross-linking agent in step (I) is:

[0020]

[0021] Among them: a is 1 to 30.

[0022] In the above technical scheme, the reaction temperature of step (II) is controlled at 120°C to 200°C, and the reaction time is 0.5h to 12h. Preferably, the reaction temperature is controlled at 120°C to 180°C, and the reaction time is 0.5h to 6h.

[0023] In the above technical scheme, the mass ratio of the alcohol compound, polyvinyl alcohol and the anhydride polymer synthesized in step (I) in step (II) is 1:(0.001-0.35):(0.01-5), preferably, the mass ratio of the alcohol compound, polyvinyl alcohol and the anhydride polymer synthesized in step (I) is 1:(0.005-0.15):(0.05-2).

[0024] In the above technical scheme, in step (II), the mass ratio of the total mass of the alcohol compound, polyvinyl alcohol and acid anhydride polymer to the solid acid is 1:(0.1-8), preferably, the mass ratio of the total mass of the alcohol compound, polyvinyl alcohol and acid anhydride polymer to the solid acid is 1:(0.5-5).

[0025] In the above technical scheme, the alcohol compound in step (II) is any one of n-butanol, n-pentanol, 2-pentanol, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol or glycerol, or a mixture of two or more thereof.

[0026] In the above technical scheme, the solid acid in step (II) is any one of sulfamic acid, oxalic acid, malonic acid, succinic acid, citric acid, diethyltriaminepentaacetic acid, ethylenediaminetetraacetic acid, ethylenediamine hydrochloride, propylenediamine hydrochloride, butylenediamine hydrochloride, alanine hydrochloride, glycine hydrochloride, serine hydrochloride, glutamic acid hydrochloride, hydroxyethylidene diphosphonic acid, hydrazine hydrochloride or hydrazine dihydrochloride, or a mixture of two or more thereof.

[0027] In the above technical scheme, the molecular weight of the polyvinyl alcohol in step (II) is 10000 g / mol to 200000 g / mol, and the alcoholysis degree of the polyvinyl alcohol is 60% to 100%. Preferably, the molecular weight of the polyvinyl alcohol is 20000 g / mol to 120000 g / mol, and the alcoholysis degree of the polyvinyl alcohol is 75% to 100%.

[0028] A solid slow-release acid for offshore oilfield blockage removal operations is prepared by the method.

[0029] The beneficial effects of the present invention are:

[0030] The invention provides a solid slow-release acid for offshore oilfield plugging removal and a preparation method thereof. The raw materials are easily available, the reaction conditions are mild, the process is simple and safe, and large-scale industrial production can be realized. Maleic anhydride and ester monomers are polymerized under the action of a crosslinking agent to prepare an anhydride-containing polymer with an adaptive molecular weight and good solubility, which is used as a crosslinking agent in a subsequent preparation process. All the raw materials have good water solubility, and the raw materials are formed by generating ester groups to realize forming processing, and the prepared slow-release acid has little residue after being dissolved. The ester unit and the vinyl acetate unit are introduced to adjust the content of the hydrophobic unit in the solid acid, so as to realize the control of the acid release speed of the product. The prepared product has good compatibility with a conventional acid plugging removal auxiliary agent. The prepared product is convenient to store, transport and use, and meets the requirements of environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process of the present invention.

[0032] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0034] Example 1

[0035] like Figure 1 As shown, a method for preparing a solid slow-release acid for offshore oilfield plugging removal operation comprises the following steps:

[0036] (I) Preparation of anhydride polymer

[0037] 20 g of maleic anhydride, 6 g of ethyl acrylate, 0.2 g of a crosslinking agent (a is 3), 1.5 g of azobisisobutyronitrile, and 100 g of ethyl acetate were added to a flask equipped with a stirrer, a nitrogen tube, and a thermometer. After stirring until all the raw materials were dissolved, nitrogen was introduced for 30 min. The polymerization temperature was controlled at 55° C. and the polymerization reaction was carried out for 8 h to obtain an anhydride polymer.

[0038] (II) Preparation of solid slow-release acid

[0039] Add 100g of ethylene glycol, 5g of polyvinyl alcohol (molecular weight 53000g / mol, alcoholysis degree 88%), and 95g of anhydride polymer into a beaker with a stirrer and a thermometer, heat and stir until all the raw materials are dissolved, then add 160g of aminosulfonic acid, stir evenly, control the temperature at 140°C, and react for 2h to obtain a solid sustained-release acid.

[0040] Example 2

[0041] As described in Example 1, except that in step (I), the ester monomers are 1 g of methyl acrylate and 2 g of butyl acrylate.

[0042] Example 3

[0043] As described in Example 1, except that the ester monomers in step (I) are 8 g of ethyl acrylate and 2 g of pentyl methacrylate.

[0044] Example 4

[0045] As described in Example 1, except that in step (I), the cross-linking agent a is 15 and the added amount is 0.1 g.

[0046] Example 5

[0047] As described in Example 1, except that in step (I), the cross-linking agent a is 25 and the added amount is 0.35 g.

[0048] Example 6

[0049] As described in Example 1, except that the initiator in step (I) is 0.3 g of azobisisoheptanonitrile and 0.6 g of azobisisobutyramidine hydrochloride.

[0050] Example 7

[0051] As described in Example 1, except that the organic solvent in step (I) is 20 g of xylene and 120 g of butanone.

[0052] Example 8

[0053] As described in Example 1, except that in step (I), the polymerization temperature is 65°C and the polymerization time is 4.5 h.

[0054] Example 9

[0055] As described in Example 1, the difference is that the alcohol compound in step (II) is 20g of n-butanol and 80g of propylene glycol.

[0056] Example 10

[0057] As described in Example 1, the difference is that the alcohol compound in step (II) is 10g of n-pentanol, 50g of diethylene glycol and 40g of propylene glycol.

[0058] Embodiment 11

[0059] As described in Example 1, the difference is that in step (II), the amount of polyvinyl alcohol added is 1.5 g, the molecular weight is 86000 g / mol, and the degree of alcoholysis is 98%.

[0060] Example 12

[0061] As described in Example 1, the difference is that in step (II), the amount of polyvinyl alcohol added is 12 g, the molecular weight is 32000 g / mol, and the degree of alcoholysis is 78%.

[0062] Embodiment 13

[0063] As described in Example 1, except that the amount of anhydride polymer added in step (II) is 40 g.

[0064] Embodiment 14

[0065] As described in Example 1, except that the amount of anhydride polymer added in step (II) is 160 g.

[0066] Embodiment 15

[0067] As described in Example 1, the difference is that the solid acid in step (II) is 150g of aminosulfonic acid, 100g of citric acid and 50g of alanine hydrochloride.

[0068] Example 16

[0069] As described in Example 1, except that in step (II), the reaction temperature is 165°C and the reaction time is 3.5 h.

[0070] The solid sustained-release acid prepared in the above embodiment was evaluated for performance, and the evaluation method specifically included:

[0071] (1) Sample preparation

[0072] Prepare saline solution with a NaCl concentration of 10 g / L. Process the solid slow-release acid into a cylindrical shape (Φ3.5×5 cm) through a mold for later use.

[0073] (2) Sustained release performance test

[0074] The solid slow-release acid cylinder was added into 500 mL of saline, sealed and placed at 80°C for aging for a period of time, 5 mL of the solution was taken out, and the acid concentration in the solution was determined by acid-base titration.

[0075] Solid acid release rate calculation formula:

[0076]

[0077] Where, RS is the release rate of solid sustained-release acid, %;

[0078] C i —Acid concentration of the solution after soaking for i time, mol / L;

[0079] C l —Acid concentration of the solution after 7 days of immersion, mol / L.

[0080] (3) Solubility test

[0081] The mass of the solid sustained-release acid cylinder was weighed, and it was added into 500 mL of saline, and then sealed and placed at 80° C. for aging for 7 days. The system was filtered to obtain the residue, and the mass was weighed after drying.

[0082] Dissolved residual rate calculation formula:

[0083]

[0084] Wherein, RD—solid acid dissolution residual rate, %;

[0085] m l —Mass of solid slow-release acid residue, g;

[0086] mi—mass of solid acid exchange cylinder, g.

[0087] (4) Dissolution test

[0088] Take the acid solution with different dissolution time, measure 200g of acid solution, weigh 5g of rock powder, accurate to 0.0001g, and record it as m2. Slowly add the weighed rock powder into a stoppered conical bottle or a plastic bottle with a lid, place it in a 65℃ constant temperature water bath to react for 4 hours, and after the reaction, use the dried quantitative filter paper for suction filtration, and place the filtered rock powder and quantitative filter paper in a 105℃ constant temperature drying oven to dry to constant weight, weigh its mass, and record it as m3.

[0089] Calculation of dissolution rate η:

[0090] η=[(m1+m2-m3) / m2]×100%

[0091] Where:

[0092] η---dissolution rate of rock powder, expressed as a percentage;

[0093] m1---The mass of the quantitative filter paper after drying, in grams (g);

[0094] m2---The mass of rock powder before dissolution, in grams (g);

[0095] m3---The total mass of rock powder and quantitative filter paper after dissolution, in grams (g).

[0096] It was found in the experiment that after cooling and forming the mold, the solid slow-release acid prepared in all the embodiments can form a cylindrical product with a certain strength, and their slow-release and solubility properties are shown in Table 1. It can be seen from the table that the embodiments all have a good slow-release effect, and the solid acid release rate is below 60% after 1 day of aging; in addition, the solid slow-release acid prepared in all the embodiments has excellent solubility performance, and the dissolution residual rate is below 5% after 7 days of aging, and the pH of the acid solution after the slow-release acid is dissolved is less than 2.

[0097] Table 1 Sustained release and dissolution properties of different samples

[0098]

[0099]

[0100] Preparation principle of the present invention:

[0101] The present invention prepares a polymer with multiple anhydride groups in the molecule by copolymerizing maleic anhydride and ester monomers in an organic solvent. On this basis, an alcohol compound, polyvinyl alcohol and anhydride polymer are reacted at high temperature to generate an organic ester type coating material, and the coating material is mixed with a solid acid to form a solid slow-release acid. The molecular skeleton of polyvinyl alcohol is used to regulate the viscosity and strength of the coating material; the release rate of the slow-release acid is controlled by the hydrophobic strength and anhydride density of the anhydride polymer. Test results show that the solid slow-release acid is simple to mold and process, convenient to store and transport, has excellent slow-release performance, and has excellent solubility under reservoir conditions.

[0102] The solid slow-release acid prepared by the invention has broad application prospects in offshore oil field blockage removal operations.

[0103] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a solid slow-release acid for offshore oilfield unblocking operations, characterized in that: The following steps are involved: (I) Preparation of anhydride polymer Maleic anhydride, ester monomer, crosslinking agent, initiator and organic solvent are mixed and polymerized under nitrogen atmosphere to obtain anhydride polymer; (II) Preparation of solid slow-release acid The alcohol compound, polyvinyl alcohol and the anhydride polymer synthesized in step (I) are mixed and fully dissolved, and a solid acid is added to the mixture for reaction. After the reaction is completed, a solid slow-release acid is obtained.

2. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The polymerization reaction temperature in step (I) is controlled at 30° C. to 80° C., and the polymerization reaction time is 1 h to 24 h.

3. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The mass ratio of maleic anhydride, ester monomer, crosslinking agent and organic solvent in the step (I) is 1:(0.01-1):(0.0005-0.05):(1-20); the mass ratio of organic solvent and initiator in the step (I) is 1:(0.0005-0.02).

4. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The ester monomer in step (I) is any one of methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate or hexyl methacrylate, or a mixture of two or more thereof; The initiator in step (I) is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, azobisisobutylimidazoline hydrochloride or azoisobutylcyanoformamide; The organic solvent in step (I) is any one of toluene, xylene, ethyl acetate, acetone, butanone, tetrahydrofuran or cyclohexane, or a mixture of two or more thereof.

5. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The chemical structural formula of the cross-linking agent in step (I) is: Among them: a is 1 to 30.

6. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The reaction temperature of step (II) is controlled at 120°C to 200°C, and the reaction time is 0.5h to 12h.

7. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The mass ratio of the alcohol compound, polyvinyl alcohol and the anhydride polymer synthesized in step (II) is 1:(0.001-0.35):(0.01-5); the mass ratio of the total mass of the alcohol compound, polyvinyl alcohol and the anhydride polymer to the solid acid in step (II) is 1:(0.1-8).

8. The method for preparing a solid slow-release acid for offshore oilfield unblocking operations according to claim 1, characterized in that: The alcohol compound in step (II) is any one of n-butanol, n-pentanol, 2-pentanol, ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol or glycerol, or a mixture of two or more thereof; The solid acid in step (II) is any one of sulfamic acid, oxalic acid, malonic acid, succinic acid, citric acid, diethyltriaminepentaacetic acid, ethylenediaminetetraacetic acid, ethylenediamine hydrochloride, propylenediamine hydrochloride, butylenediamine hydrochloride, alanine hydrochloride, glycine hydrochloride, serine hydrochloride, glutamic acid hydrochloride, hydroxyethylidene diphosphonic acid, hydrazine hydrochloride or hydrazine dihydrochloride, or a mixture of two or more thereof.

9. The method for preparing a solid slow-release acid for offshore oilfield blockage removal according to claim 1, characterized in that: The molecular weight of the polyvinyl alcohol in the step (II) is 10000 g / mol to 200000 g / mol, and the alcoholysis degree of the polyvinyl alcohol is 60% to 100%.

10. A solid slow-release acid for offshore oilfield blockage removal operations, characterized in that: Prepared by the method according to any one of claims 1 to 9.

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