Surfactant for drilling fluid as well as preparation method and application of surfactant

Abstract

The invention provides a surfactant for drilling fluid as well as a preparation method and application of the surfactant, and belongs to the technical field of drilling compositions. The preparation method of the surfactant for the drilling fluid comprises the following steps: (1) carrying out ring-opening reaction on dihydric alcohol and maleic anhydride to obtain a first intermediate; (2) carrying out esterification reaction on the first intermediate and a long-chain alcohol compound under the action of a catalyst to obtain a second intermediate; and (3) carrying out sulfonation reaction on the second intermediate, sultone and alkali metal hydride to obtain the product. According to the invention, the surfactant is endowed with excellent salt resistance and high temperature resistance through two functional groups of anion (-OR4SO2M1) and nonionic (-COOR2), the biodegradability is good, and the environmental protection performance is excellent. In addition, the drilling fluid has good compatibility and good inhibition performance in drilling fluid, and is suitable for drilling operation of high-temperature and high-salinity carbonate reservoirs.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling compositions, and in particular relates to a surfactant for drilling fluid and a preparation method and application thereof. Background Art

[0002] Due to its unique amphoteric structure, surfactants have the properties of reducing surface tension, foaming, emulsification, dispersion, wetting, solubilization, etc. With the extensive application of surfactants for drilling fluids in the field of oil and gas exploration and production, many problems encountered during drilling can be solved, which has played a very important role in promoting drilling operations. The research on surfactants for drilling fluids has also received attention from relevant practitioners.

[0003] Carbonate oil reservoirs are generally deep, with high temperature and high pressure. The reservoir depth can reach more than 6000m, and the reservoir temperature can reach 130-150℃. With the increase of carbonate oil reservoir mining depth, the formation temperature rises and the formation water mineralization increases, which puts higher requirements on the temperature resistance and salt resistance of the surfactant used in the drilling fluid.

[0004] CN107312511A discloses a surfactant for drilling fluid and a preparation method thereof. The surfactant is prepared by reacting an alkylphthalene halogen compound with an amino compound under alkaline conditions. The preparation method is simple and has a good sealing effect on the air nucleus in the microbubble. However, since there is only one hydrophobic group and oleophobic group in the surfactant structure, the surface activity is poor. At the same time, the surfactant has insufficient temperature resistance and can only reach 120°C, which is not suitable for high-temperature carbonate oil reservoirs.

[0005] CN107311894A discloses an anionic surfactant for drilling fluid and a preparation method thereof, which is prepared by reacting a polyoxyethylene compound with aminosulfonic acid. The surfactant has good foaming performance, but its temperature resistance is insufficient and can only reach 120°C, which cannot meet the requirement of 130-150°C for the formation temperature of carbonate oil reservoirs.

[0006] CN108441177B discloses a surfactant for drilling fluid and a preparation method thereof, wherein the surfactant is made of the following raw materials: mineral oil, n-butyl oleate, liquid paraffin, methyl silicone oil, emulsifier, and ethyl p-hydroxybenzoate. It still has good performance at high temperatures, but can only resist 10% composite brine and cannot be applied to high-mineralization carbonate reservoirs.

[0007] Therefore, in view of the above problems, it is very necessary to develop a new type of surfactant for drilling fluid that is both temperature-resistant and salt-resistant. Summary of the invention

[0008] In view of the above problems existing in the prior art, one object of the present invention is to provide a temperature-resistant and salt-resistant surfactant for drilling fluid.

[0009] The second object of the present invention is to provide a method for preparing a temperature-resistant and salt-resistant surfactant for drilling fluid.

[0010] To achieve the above-mentioned purpose, the surfactant for drilling fluid of the present invention has the general structural formula of formula I:

[0011]

[0012] In Formula I, R1 is selected from the group consisting of n H 2n -alkyl, n is selected from an integer between 1 and 5; R2 and R3 are selected from the general formula -C m H 2m+1 alkyl, m is selected from an integer between 10 and 15; R4 and R5 are selected from the general formula -C z H 2z+1 An alkyl group, z is selected from an integer between 1 and 5; M1 and M2 are selected from alkali metals.

[0013] In order to make the surfactant obtain better high temperature resistance and salt resistance, adapt to the gradually increasing formation temperature and increased formation water mineralization with the increase of mining depth, and be more suitable for use in drilling fluids of carbonate oil reservoirs, preferably, the general formula -C m H 2m+1 Where m is 12, 13 or 14; the general formula is -C z H 2z+1 Where z is 3 or 4; M1 and M2 are selected from Li, Na, and K respectively.

[0014] The present invention introduces two functional groups, anion (-OR4SO2M1) and nonion (-COOR2), into the surfactant, utilizing the fact that the nonion functional group will not dissociate in the solution and has good salt resistance, and the anion functional group has good temperature resistance, so that the surfactant has both good temperature resistance and salt resistance.

[0015] The technical scheme of the method for preparing the surfactant for drilling fluid of the present invention is:

[0016] A method for preparing a surfactant for drilling fluid comprises the following steps:

[0017] (1) A diol is subjected to a ring-opening reaction with maleic anhydride to obtain a first intermediate having a general structural formula of Formula II:

[0018]

[0019] (2) subjecting the first intermediate described in step (1) to an esterification reaction with a long-chain alcohol compound in the presence of a catalyst to obtain a second intermediate having a general structural formula of formula III:

[0020]

[0021] (3) subjecting the second intermediate described in step (2), sultone and alkali metal hydride to a sulfonation reaction; the sultone has the general structural formula: The general formula of the alkali metal hydride is MH.

[0022] The method for preparing the surfactant for drilling fluid of the present invention has readily available raw materials and simple process, and is suitable for industrial large-scale production.

[0023] In order to ensure that maleic anhydride and diol react fully, preferably, the mass ratio of maleic anhydride to diol in step (1) is 2:1-5:1. More preferably, the mass ratio of maleic anhydride to diol is 2:1-4:1. More preferably, the mass ratio of maleic anhydride to diol is 2:1-3:1.

[0024] In order to allow maleic anhydride and diol to dissolve and fully react, preferably, in step (1), maleic anhydride and diol are dissolved in a solvent to carry out a ring-opening reaction.

[0025] In order to improve the purity of the first intermediate, preferably, the diol in step (1) is selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

[0026] In order to ensure that the first intermediate and the long-chain alcohol compound react fully, preferably, the mass ratio of the first intermediate and the long-chain alcohol compound in step (2) is 1:2-1:5. More preferably, the mass ratio of the first intermediate and the long-chain alcohol compound is 1:2-1:4. More preferably, the mass ratio of the first intermediate and the long-chain alcohol compound is 1:2-1:2.5.

[0027] In order to improve the purity of the second intermediate, preferably, the long-chain alcohol compound in step (2) is selected from one or two of n-dodecanol, n-tridecanol and n-tetradecanol.

[0028] In order to ensure that the second intermediate and sultone react fully, preferably, the mass ratio of the second intermediate and sultone in step (3) is 2:1-4:1. More preferably, the mass ratio of the second intermediate and sultone is 2:1-3:1. More preferably, the mass ratio of the second intermediate and sultone is 2.5:1-3:1.

[0029] Preferably, in step (3), the mass ratio of the second intermediate to the alkali metal hydride is 5: 1-25: 1. More preferably, the mass ratio of the second intermediate to the alkali metal hydride is 10: 1-25: 1. More preferably, the mass ratio of the second intermediate to the alkali metal hydride is 15: 1-20: 1.

[0030] Preferably, the sultone in step (3) is selected from one or both of propane sultone and butane sultone; and the alkali metal hydride is selected from one or both of LiH, NaH and KH.

[0031] The third object of the present invention is to provide an application of a surfactant for drilling fluid in drilling fluid.

[0032] Through the above technical solution, the present invention can achieve the following beneficial effects:

[0033] (1) The surfactant for drilling fluid provided by the present invention has two lipophilic groups (-COOR2) and two hydrophilic groups (-OR4SO2M1), and thus has a lower critical micelle concentration and also has excellent surface activity properties.

[0034] (2) Compared with the prior art, the present invention endows the surfactant with excellent salt resistance and high temperature resistance through two functional groups, anion (-OR4SO2M1) and nonion (-COOR2). The surfactant provided by the present invention can resist 250g / L NaCl solution and 200g / L CaCl2 solution, and still has excellent water solubility in high-salinity water, showing strong salt resistance; at the same time, the surfactant of the present invention can resist high temperature of 150°C, and the surface tension hardly changes at this temperature, so it is suitable for high-temperature and high-mineralization carbonate reservoirs. In addition, the surfactant for drilling fluid provided by the present invention has good biodegradability and excellent environmental performance, and will not pollute the formation during drilling operations.

[0035] (3) The surfactant for drilling fluid provided by the present invention has good compatibility in drilling fluid and can be quickly adsorbed on the surface of the core, so that the wettability of the core changes from hydrophilic to hydrophobic, thereby reducing the affinity for water molecules and having good inhibition performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the Fourier infrared spectrum of Example 1 of the present invention;

[0037] Figure 2 The surface tension of Examples 1 to 6 of the present invention varies with concentration;

[0038] Figure 3 It is a comparison diagram of the zeta potential of Examples 1 to 6 of the present invention and a surfactant solution of sodium dodecyl sulfate (SDS);

[0039] Figure 4 The biodegradation rate variation diagram of Examples 1 to 6 of the present invention and SDS surfactant;

[0040] Figure 5 The cuttings recovery rate of Examples 1 to 6 of the present invention and SDS surfactant when used in drilling fluid. DETAILED DESCRIPTION

[0041] A surfactant for drilling fluid, having the general structural formula of formula I:

[0042]

[0043] In Formula I, R1 is selected from the group consisting of n H 2n -alkyl, n is selected from an integer between 1 and 5; R2 and R3 are selected from the general formula -C m H 2m+1 alkyl, m is selected from an integer between 10 and 15; R4 and R5 are selected from the general formula -C z H 2z+1 An alkyl group, z is selected from an integer between 1 and 5; M1 and M2 are selected from alkali metals.

[0044] In a specific embodiment of the present invention, R2 and R3 may be the same alkyl group or different, depending on the long-chain alcohol compound used in the preparation process; R4 and R5 may be the same alkyl group or different, depending on the sultone used in the preparation process; M1 and M2 may be the same alkali metal or different, preferably, M1 and M2 are the same alkali metal.

[0045] A method for preparing a surfactant for drilling fluid comprises the following steps:

[0046] (1) A diol is subjected to a ring-opening reaction with maleic anhydride to obtain a first intermediate having a general structural formula of Formula II:

[0047]

[0048] (2) subjecting the first intermediate described in step (1) to an esterification reaction with a long-chain alcohol compound in the presence of a catalyst to obtain a second intermediate having a general structural formula of formula III:

[0049]

[0050] (3) subjecting the second intermediate described in step (2), sultone and alkali metal hydride to a sulfonation reaction; the sultone has the general structural formula: The general formula of the alkali metal hydride is MH.

[0051] In a specific embodiment of the present invention, the reaction process of the ring-opening reaction in step (1) is as follows:

[0052]

[0053] wherein R1 is -(CH2)2-, -(CH2)3- or -(CH2)4-;

[0054] The reaction process of the esterification reaction in step (2) is as follows:

[0055]

[0056] Wherein, R2 is -(C 12 H 25 )、-(C 13 H 27 ) or -(C 14 H 29 ) one or both;

[0057] The reaction process of the sulfonation reaction in step (3) is as follows:

[0058]

[0059] Wherein, R3 is one or both of -(CH2)3- and -(CH2)4-, and MH is one or both of LiH, NaH and KH.

[0060] In a specific embodiment of the present invention, the choice of solvent in step (1) is not particularly limited, as long as it can dissolve maleic anhydride and alcohol compounds. Preferably, the solvent is selected from one of methanol, ethanol and acetone. More preferably, the solvent is acetone.

[0061] In a specific embodiment of the present invention, the amount of the solvent acetone used in step (1) is not particularly limited, as long as it can completely dissolve maleic anhydride and alcohol compounds. Preferably, the mass ratio of maleic anhydride to acetone is 1:5-1:20. More preferably, the mass ratio of maleic anhydride to acetone is 1:8-1:15. More preferably, the mass ratio of maleic anhydride to acetone is 1:8-1:12.

[0062] In a specific embodiment of the present invention, the ring-opening reaction in step (1) is carried out in the presence of a catalyst; the catalyst is selected from one of concentrated sulfuric acid, concentrated hydrochloric acid and p-toluenesulfonic acid. Preferably, the catalyst is p-toluenesulfonic acid.

[0063] In a specific embodiment of the present invention, the mass ratio of maleic anhydride to p-toluenesulfonic acid in step (1) is 50:1-100:1. Preferably, the mass ratio of maleic anhydride to p-toluenesulfonic acid is 50:1-80:1. More preferably, the mass ratio of maleic anhydride to p-toluenesulfonic acid is 60:1-70:1.

[0064] In a specific embodiment of the present invention, the product solution obtained by the ring-opening reaction in step (1) is subjected to reduced pressure evaporation to remove the solvent to obtain the first intermediate.

[0065] In a specific embodiment of the present invention, the catalyst in step (2) is selected from one of concentrated sulfuric acid, concentrated hydrochloric acid and toluenesulfonic acid. Preferably, the catalyst is p-toluenesulfonic acid.

[0066] In a specific embodiment of the present invention, the mass ratio of the first intermediate to p-toluenesulfonic acid in step (2) is 50: 1-100: 1. Preferably, the mass ratio of the first intermediate to p-toluenesulfonic acid is 50: 1-80: 1. More preferably, the mass ratio of the first intermediate to p-toluenesulfonic acid is 60: 1-70: 1.

[0067] In a specific embodiment of the present invention, the sulfonation reaction in step (3) is carried out in the presence of tetrahydrofuran, and the surfactant is obtained by purification after sulfonation; preferably, the specific method of step (3) is: dissolving the second intermediate, sultone, and alkali metal hydride in tetrahydrofuran, performing a reflux reaction, mixing the solution obtained after the reflux with ethanol, distilling off the tetrahydrofuran and ethanol solvent under reduced pressure to obtain an oily liquid, and then recrystallizing the oily liquid to obtain the surfactant.

[0068] In a specific embodiment of the present invention, the water content in tetrahydrofuran in step (3) should be less than 1wt%. Tetrahydrofuran can be dehydrated and purified using conventional methods in the art. Preferably, the dehydration and purification process comprises: adding anhydrous CaCl2 to tetrahydrofuran, filtering to obtain reaction solvent I, adding sodium strips to the reaction solvent I, and adding benzophenone after refluxing. If the solution turns blue, it indicates that the water content in tetrahydrofuran meets the above requirements, otherwise, the tetrahydrofuran is not completely dehydrated.

[0069] In a specific embodiment of the present invention, in order to more completely and thoroughly remove the moisture in tetrahydrofuran, the mass ratio of tetrahydrofuran to anhydrous CaCl2 in the dehydration and purification process of tetrahydrofuran is 20:1-50:1. Preferably, the mass ratio of tetrahydrofuran to anhydrous CaCl2 is 20:1-40:1. More preferably, the mass ratio of tetrahydrofuran to anhydrous CaCl2 is 25:1-30:1. The mass ratio of anhydrous CaCl2 to sodium strips is 5:1-1:1. Preferably, the mass ratio of anhydrous CaCl2 to sodium strips is 4:1-1:1. More preferably, the mass ratio of anhydrous CaCl2 to sodium strips is 3:1-2:1.

[0070] In a specific embodiment of the present invention, benzophenone is used as an indicator to show whether the tetrahydrofuran is completely dehydrated, so the amount of benzophenone is not particularly limited; preferably, the mass ratio of benzophenone to tetrahydrofuran is 0.1-0.3:60. More preferably, the mass ratio of benzophenone to tetrahydrofuran is 0.1-0.24:60. More preferably, the mass ratio of benzophenone to tetrahydrofuran is 0.1-0.2:60.

[0071] In a specific embodiment of the present invention, in order to remove the alkali metal hydride in the refluxed solution, the refluxed solution is mixed with ethanol. The amount of the ethanol is not particularly limited, as long as the excess alkali metal hydride in the refluxed solution can be completely removed; preferably, the mass ratio of the ethanol to the alkali metal hydride is 100:3.

[0072] In a specific embodiment of the present invention, the oily liquid in step (3) is recrystallized with n-hexane.

[0073] The invention discloses an application of a surfactant for drilling fluid in drilling fluid.

[0074] In a specific embodiment of the present invention, the specific method for applying the surfactant provided by the present invention in the drilling fluid is: using a conventional method in the art to prepare a water-based drilling fluid, based on the total amount of the drilling fluid, the formula of the water-based drilling fluid is: 4% Huawei sodium soil base slurry + 1% GWJ-1 + 0.4% PAC-LV + 1.5% PF-LUBE + 3.0% FT-1 + 3% NaOH; adding 4 to 6 wt% of the surfactant for drilling fluid provided by the present invention to the basic formula.

[0075] The embodiments of the present invention are further described below in conjunction with specific examples. Maleic anhydride, p-toluenesulfonic acid, tetrahydrofuran, propane sultone and butane sultone involved in the following examples were purchased from Sinopharm Chemical Reagent Co., Ltd.

[0076] 1. Specific embodiments of the method for preparing the surfactant for drilling fluid of the present invention

[0077] Example 1

[0078] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0079] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 4 g of ethylene glycol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0080] (2) Slowly add 16 g of n-dodecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0081] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 3.5 g of propane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0082] Example 2

[0083] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0084] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 4.5 g of 1,3-propylene glycol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0085] (2) Slowly add 16 g of n-dodecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0086] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 3.5 g of propane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0087] Example 3

[0088] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0089] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 5 g of 1,4-butanediol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0090] (2) Slowly add 16 g of n-dodecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0091] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 3.5 g of propane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0092] Example 4

[0093] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0094] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 4 g of ethylene glycol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0095] (2) Slowly add 17.5 g of n-tridecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0096] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 3.5 g of propane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0097] Example 5

[0098] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0099] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 4 g of ethylene glycol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0100] (2) Slowly add 19 g of n-tetradecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0101] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 3.5 g of propane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0102] Example 6

[0103] The method for preparing the surfactant for drilling fluid of the present embodiment comprises the following steps:

[0104] (1) Dissolve 10 g of maleic anhydride in 100 mL of acetone, slowly add 4 g of ethylene glycol to the maleic anhydride solution, and then add 0.15 g of p-toluenesulfonic acid. After reacting at 90° C. for 4 h, evaporate the solvent acetone under reduced pressure to obtain a first intermediate.

[0105] (2) Slowly add 16 g of n-dodecanol to 8 g of the first intermediate obtained in step (1), and then add 0.15 g of p-toluenesulfonic acid, and react at 150° C. for 3 h to obtain a second intermediate.

[0106] (3) 10 g of the second intermediate obtained in step (2) was dissolved in 200 g of tetrahydrofuran (water content less than 1 wt%), and 0.5 g of NaH was added after N2 was introduced, and then 4 g of butane sultone was added. After reflux reaction for 48 h, 10 g of ethanol was added, and when no bubbles were generated, the solvents tetrahydrofuran and ethanol were evaporated under reduced pressure to obtain an oily liquid, which was recrystallized with n-hexane at 3° C. for 4 h. The obtained white solid was a surfactant for drilling fluid.

[0107] 2. Specific embodiments of the surfactant for drilling fluid of the present invention

[0108] A surfactant for drilling fluid, having the general structural formula of formula I:

[0109]

[0110] In Formula I, R1 is selected from the group consisting ofn H 2n -alkyl, n is selected from an integer between 1 and 5; R2 and R3 are selected from the general formula -C m H 2m+1 alkyl, m is selected from an integer between 10 and 15; R4 and R5 are selected from the general formula -C z H 2z+1 An alkyl group, z is selected from an integer between 1 and 5; M1 and M2 are selected from alkali metals.

[0111] The products obtained by the preparation methods of the above-mentioned Examples 1 to 6 are the surfactants for drilling fluids of the present invention.

[0112] In the surfactant of Example 1, R1 is selected from the general formula -C n H 2n -alkyl, n is 2; R2, R3 are selected from the general formula -C m H 2m+1 R2 and R3 are both 12; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is both 3; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0113] In the surfactant of Example 2, R1 is selected from the general formula -C n H 2n -alkyl, n is 3; R2, R3 are selected from the general formula -C m H 2m+1 R2 and R3 are both 12; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is both 3; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0114] In the surfactant of Example 3, R1 is selected from the general formula -C n H 2n -alkyl, n is 4; R2, R3 are selected from the general formula -C m H 2m+1 R2 and R3 are both 12; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is both 3; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0115] In the surfactant of Example 4, R1 is selected from the general formula -C n H 2n -alkyl, n is 2; R2, R3 are selected from the general formula -C m H2m+1 R2 and R3 are both 13; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is both 3; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0116] In the surfactant of Example 5, R1 is selected from the general formula -C n H 2n -alkyl, n is 2; R2, R3 are selected from the general formula -C m H 2m+1 R2 and R3 are both 14; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is both 3; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0117] In the surfactant of Example 6, R1 is selected from the general formula -C n H 2n -alkyl, n is 2; R2, R3 are selected from the general formula -C m H 2m+1 R2 and R3 are both 12; R4 and R5 are selected from the general formula -C z H 2z+1 alkyl, z in R4 and R5 is 4; M1 and M2 are respectively selected from alkali metals, and M1 and M2 are both Na.

[0118] 3. Experimental Examples

[0119] 1) Performance test of surfactants prepared in Examples 1 to 6

[0120] Experimental Example 1 (Infrared Spectroscopy Test)

[0121] In this experimental example, Fourier transform infrared spectrometer was used to test and analyze the surfactant used in the drilling fluid in Example 1. The results are as follows: Figure 1 As shown. Figure 1 The infrared spectrum shows that 1045.03cm -1 The characteristic peak of O=S is at 1167.92cm -1 The asymmetric stretching vibration peak of -C-O-C- is at 1227.77cm -1 The stretching vibration peak of —C—O— is at 1459.18cm -1 The bending vibration peak of -CH3 is at 1736.09cm -1 The stretching vibration peak of carbonyl C=O is at 2925.90cm -1 The antisymmetric stretching vibration peak of -CH2- is at 2945.05cm-1 、2854.08cm -1 The positions are respectively the antisymmetric stretching vibration peak and the symmetric stretching vibration peak of -CH3, which are consistent with the structural characteristics of the surfactant prepared by the present invention.

[0122] Experimental Example 2 (Surface Tension Test)

[0123] The surface tension and critical micelle concentration (CMC) of the surfactants prepared in Examples 1 to 6 were measured by surface tension method. A series of surfactant solutions with concentrations (0.01, 0.02, 0.05, 0.08, 0.1, 0.15, 0.2, 0.3, 0.5, 0.8, 1, 2, 5 and 10 g / L) were prepared, and the surface tension was measured at room temperature using a QBZY fully automatic surface tension meter. Each sample was tested three times and the average value was taken. The test results are shown in Table 1. The surface tension changes with concentration are shown in Table 1. Figure 2 shown.

[0124] Table 1 Surface tension test results

[0125]

[0126] CMC represents the lowest concentration at which surfactant molecules associate to form micelles. When the concentration is higher than this value, the surfactant does not exist in the water as a single molecule, but forms micelles in which the lipophilic groups are aggregated and the hydrophilic groups extend into the solution. At this time, the solubilization effect of the surfactant increases. The CMC value of the surfactant is determined based on the relationship between surface tension and concentration. The CMC is shown as the inflection point where the surface tension no longer decreases in the lgC-γ diagram. Figure 2 It can be seen that when the logarithmic value of the surfactant concentration increases to -1.5, the surface tension of the solution no longer decreases significantly. It can be seen that the CMC of the surfactant is about 32 mg / L, which is much lower than 1.6 g / L of the conventional surfactant sodium dodecyl sulfate (SDS). At the same time, the surfactant prepared by the present invention can reduce the surface tension of the aqueous solution to 32 mN / m, and has excellent surface activity performance.

[0127] Experimental Example 3 (Zeta Potential Test)

[0128] The surfactants and SDS prepared in Examples 1-6 were respectively prepared into 10 g / L solutions, and the Zeta potential of the above solutions was measured using a ZS910 Malvern Zeta potential meter. Each solution was tested three times and the average value was taken. The experimental results are shown in Figure 3 .

[0129] The Zeta potential of a surfactant solution can represent the charge on the surface of its micelle particles. For anionic surfactants, the lower the Zeta potential, the more negative charge there is on the micelle surface. Therefore, the adsorption loss on the electronegative aquifer medium due to electrostatic repulsion is lower.

[0130] from Figure 3 The test results show that the Zeta potentials of both Examples 1 to 6 and SDS are negative, and the absolute value of the Zeta potential of the Examples is larger than that of SDS, indicating that the surfactant prepared by the present invention is less likely to be adsorbed by the aquifer medium during use. A smaller adsorption amount can reduce the amount of material used and reduce the degree of secondary pollution to the environment, which is beneficial to its application in underground environments.

[0131] Experimental Example 4 (Salt Resistance Test)

[0132] 100 mL of 10 g / L aqueous surfactant solution of Examples 1-6 was prepared respectively, and different masses of NaCl and CaCl2 were slowly added at 60°C. After complete dissolution, the state of the surfactant solution was observed as shown in Table 2.

[0133] Table 2 The state of surfactant solution in different concentrations of brine

[0134]

[0135] From the results in Table 2, it can be seen that the surfactants of Examples 1 to 6 can resist 250 g / L NaCl solution and 200 g / L CaCl2 solution, and still have excellent water solubility in high-salinity water, showing strong salt resistance.

[0136] Experimental Example 5 (High Temperature Resistance)

[0137] The surfactants of Examples 1 to 6 were placed in an oven at 150° C. for 7 days, then taken out and cooled to 25° C. to prepare 10 g / L aqueous surfactant solutions, and their surface tensions were measured. The experimental results are shown in Table 3.

[0138] Table 3 Surface tension of surfactant solution before and after being placed in an oven at 150°C for 7 days

[0139]

[0140] From the test results in Table 3, it can be seen that the surface tension of the surfactant increases slightly after being placed in an oven at 150°C for 7 days, with a small change, indicating that the surfactant of the present invention can withstand high temperatures of 150°C.

[0141] Experimental Example 6 (Biodegradation Test)

[0142] The biodegradability of the surfactants and SDS in Examples 1 to 6 was determined according to the "Surfactant Biodegradability Test Method". Specifically, the activated sludge organisms were first domesticated with surfactants, and then a certain amount of domesticated sludge and surfactants were taken for shaking culture, and the reduction of surfactants during the culture cycle was measured to obtain the biodegradability of the surfactants within a certain period of time. The test results of the biodegradability of the surfactants and SDS in Examples 1 to 6 within seven days are shown in the following figure. Figure 4 shown.

[0143] from Figure 4 The test results show that the biodegradability of the surfactants in Examples 1 to 6 reaches 90% after 3 days of degradation, and the initial degradation is completed after 5 days, with a biodegradability of up to 99%, while the biodegradation rate of SDS after 7 days of degradation is 84.8%. It can be seen that the surfactants synthesized in the present invention have good biodegradability and meet the standards of environmentally friendly surfactants.

[0144] 2) Application of the surfactants prepared in Examples 1 to 6 in drilling fluids

[0145] Experimental Example 7 (Performance Test in Drilling Fluid Application)

[0146] The water-based drilling fluid is prepared using conventional methods in the art. Based on the total amount of drilling fluid, the formula of the water-based drilling fluid is: 4% Huawei sodium soil-based slurry + 1% GWJ-1 + 0.4% PAC-LV + 1.5% PF-LUBE + 3.0% FT-1 + 3% NaOH. The water-based drilling fluid is configured according to the order of addition in the above formula. The specific operation process is: adding the treatment agent while homogenizing with a high-speed homogenizer, and the speed of the homogenizer is 10000rpm. The addition interval of each treatment agent is 10min. After all the treatment agents are added, continue stirring for 20min using a high-speed homogenizer at a speed of 10000rpm. The prepared water-based drilling fluid is the basic formula.

[0147] 5wt% of the surfactant and SDS prepared in Examples 1 to 6 were added to the above basic formula. With reference to the standard GB / T 16783.1-2014 "Drilling Fluid Field Test Part 1: Water-based Drilling Fluid", the rheological parameters and filtration loss of the drilling fluid before and after hot rolling at 150°C for 16 hours were measured, and the test results are shown in Table 4. Among them, the rheological parameters were tested by ZNN-D6 six-speed viscometer and Brookfield viscometer, including apparent viscosity AV, plastic viscosity PV and dynamic shear force YP; the filtration loss was tested by ZNS-2 medium-pressure filter loss meter.

[0148] Table 4 Rheological filtration properties of drilling fluid

[0149]

[0150]

[0151] From the rheological filtration performance test results in Table 4, it can be seen that after adding the surfactant prepared by the present invention and SDS to the basic formula, the viscosity and shear force of the drilling fluid added with ZYBH before and after aging at 150°C for 16 hours change less than that of sodium dodecyl sulfate SDS, and the rheological parameters and API filtration loss before and after hot rolling are lower, and the rheological filtration performance is better.

[0152] Experimental Example 8 (Shale Swelling Rate and Recovery Rate Test)

[0153] In this experimental example, the inhibition performance of the surfactant was evaluated by two indicators: shale expansion rate and shale recovery rate.

[0154] (1) Shale expansion experiment: 10 g of sodium bentonite was dried for 4 h, placed in a homemade mold and pressed at a pressure of 10 MPa for 5 min to obtain an artificial core. The linear expansion rate of the artificial core in clean water, a basic drilling fluid formula, and a drilling fluid containing 5 wt % of the surfactants of Examples 1 to 6 and SDS was measured using an intelligent shale expansion instrument. The test results are shown in Table 5.

[0155] Table 5 Linear expansion rate of drilling fluid

[0156]

[0157]

[0158] From the test results of the linear expansion rate in Table 5, it can be seen that the expansion rate of the artificial core in clean water for 500 minutes is 42.86%, and the expansion rate in the basic formula of water-based drilling fluid for 500 minutes is 36.36%. After adding the surfactants of Examples 1 to 6, the expansion rate is only 26.09%-30.43%, while the expansion rate after adding SDS is 33.3%, indicating that the surfactant provided by the present invention has better inhibition performance.

[0159] (2) Shale rolling dispersion experiment: 50 g of Feixianguan Formation mud shale with a particle size of 5-10 mesh was taken and placed in 350 mL of clean water, a basic drilling fluid formula, and a water-based drilling fluid containing surfactants and SDS of Examples 1 to 6. After hot rolling at 150° C. for 16 h, the mixture was passed through a 40-mesh standard sieve. The residue on the sieve was dried at 105° C., and the rock chip recovery rate was measured. The test results are shown in FIG. Figure 5 shown.

[0160] Figure 5 1# is the basic drilling fluid formula, 2#-7# are drilling fluids to which 5wt% of the surfactants of Examples 1 to 6 are added respectively, and 8# is the drilling fluid to which SDS is added. Figure 4 It can be seen that after adding 5wt% of the surfactant of the present invention, the cuttings recovery rate reaches more than 90%, while the cuttings recovery rate of the drilling fluid after adding 5wt% of SDS is 87.59%, indicating that the surfactant of the present invention has a stronger ability to inhibit shale hydration and dispersion.

Claims

1. A surfactant for drilling fluid, characterized in that: It has the general structural formula of formula I: In Formula I, R1 is selected from the group consisting of n H 2n -alkyl, n is selected from an integer between 1 and 5; R2 and R3 are selected from the general formula -C m H 2m+1 alkyl, m is selected from an integer between 10 and 15; R4 and R5 are selected from the general formula -C z H 2z+1 An alkyl group, z is selected from an integer between 1 and 5; M1 and M2 are selected from alkali metals.

2. The surfactant for drilling fluid according to claim 1, characterized in that The general formula-C m H 2m+1 Where m is 12, 13 or 14; the general formula is -C z H 2z+1 Where z is 3 or 4; M1 and M2 are selected from Li, Na, and K respectively.

3. A method for preparing a surfactant for drilling fluid according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) A diol is subjected to a ring-opening reaction with maleic anhydride to obtain a first intermediate having a general structural formula of Formula II: (2) subjecting the first intermediate described in step (1) to an esterification reaction with a long-chain alcohol compound in the presence of a catalyst to obtain a second intermediate having a general structural formula of formula III: (3) subjecting the second intermediate described in step (2), sultone and alkali metal hydride to a sulfonation reaction; the sultone has the general structural formula: The general formula of the alkali metal hydride is MH.

4. The method for preparing a surfactant for drilling fluid according to claim 3, characterized in that: In the step (1), the mass ratio of maleic anhydride to diol is 2:1-5:

1.

5. The method for preparing a surfactant for drilling fluid according to claim 3 or 4, characterized in that: The diol in step (1) is selected from ethylene glycol, 1,3-propylene glycol, and 1,4-butanediol.

6. The method for preparing a surfactant for drilling fluid according to claim 3, characterized in that: The long-chain alcohol compound in step (2) is selected from one or two of n-dodecanol, n-tridecanol and n-tetradecanol.

7. The method for preparing a surfactant for drilling fluid according to claim 3, characterized in that: In the step (3), the mass ratio of the second intermediate to sultone is 2:1-4:1; the mass ratio of the second intermediate to alkali metal hydride is 5:1-25:

1.

8. The method for preparing a surfactant for drilling fluid according to claim 3, characterized in that: The sultone in step (3) is selected from one or two of propane sultone and butane sultone; and the alkali metal hydride is selected from one or two of LiH, NaH, and KH.

9. Use of the surfactant for drilling fluid according to any one of claims 1 to 8 in drilling fluid.

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