Nitrogen foam cement slurry system as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a nitrogen foam cement slurry system and a preparation method and application thereof. The preparation method comprises the following steps: adding 2-aminoethanol hydrogen sulfate, a solvent and 2-bromododecanoic acid into a reactor, uniformly stirring, heating and refluxing, and regulating and maintaining the pH value to be 8-9 by using sodium hydroxide; and carrying out reduced pressure distillation to obtain viscous liquid, recrystallizing with cyclohexane to obtain solid, and drying to obtain the foaming agent. Uniformly stirring a foaming agent, a foam stabilizer and tap water in proportion to obtain a water phase; adding the water phase into a foam cement slurry stirring cup, stirring at a low speed in a nitrogen atmosphere, and adding a strength retention agent and G-grade oil well cement to obtain cement slurry; and stirring the cement slurry at a high speed to obtain the nitrogen foam cement slurry system. The nitrogen foam cement slurry system has the characteristics of small density difference and high strength.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a nitrogen foam cement slurry system and a preparation method and application thereof. Background Art

[0002] In the process of oil and gas well exploration and development, cementing is an extremely critical link. With the advancement of oil and gas exploration and development to deep, complex formations and special oil and gas reservoirs, higher and higher requirements are placed on cementing quality. Traditional cement slurry systems have gradually exposed many limitations under some special working conditions. For example, in deep wells and ultra-deep wells, high temperature and high pressure environments can easily lead to deterioration of cement slurry performance, resulting in strength decline and difficulty in controlling thickening time. In low-pressure and leaky formations, conventional cement slurry has a relatively high density and is prone to leaking formations, causing cement slurry leakage, which in turn affects the cementing sealing effect and may lead to serious consequences such as oil, gas and water channeling, reducing the production life and safety of oil and gas wells.

[0003] To solve the above problems, nitrogen foam cement slurry system has gradually attracted attention as a new type of cementing material. Nitrogen, as an inert gas, has good compressibility and low density. Introducing nitrogen into the cement slurry system in the form of foam can significantly reduce the density of the cement slurry, thereby effectively solving the cementing problem of low-pressure and leaky formations. At the same time, the closed air cavity structure formed by nitrogen foam in the cement slurry can improve the temperature resistance and toughness of the cement stone and improve the comprehensive performance of the cement slurry.

[0004] However, the dispersion stability of nitrogen in cement slurry is difficult to control, and foam aggregation and collapse are likely to occur, resulting in uneven cement slurry performance and failure to meet the precise requirements of cementing construction. This requires researchers to use foam technology to improve cement slurry performance. The key point is to improve the quality of the foaming system, among which the foam system composed of foaming agent and foam stabilizer is particularly important.

[0005] CN103525387B discloses a novel chemical nitrogen-filled foamed cement slurry, wherein the components and weight proportions of the novel chemical nitrogen-filled foamed cement slurry system are: 100 parts of oil well cement, 0.5-2.0 parts of gas generating agent I, 0.5-2.0 parts of gas generating agent II, 0.7-2.5 parts of foam stabilizer, 1.0-10 parts of fluid loss reducer, 0.1-0.5 parts of dispersant, 0.3-1.0 parts of retarder, 1.0-4.0 parts of early strength agent, and 48-70 parts of water. However, the foamed cement slurry of the invention has poor stability, and the strength of the cement stone formed is low.

[0006] CN109400205A discloses a cement slurry, comprising: cement, a fluid loss reducer, a dispersant, a foaming agent, a foam stabilizer, an early strength agent and water, wherein the foaming agent comprises a protein foaming agent. The invention also provides a foam cement slurry system based on the cement slurry and an application method of the cement slurry. Based on the air bubbles filled in the cement slurry provided by the present invention, the introduced air bubbles are more stable, and the foamed cement stone formed after solidification has higher strength and better elasticity and plasticity. However, the compressive strength of the cement slurry formed by the invention is only about 10MPa, and the strength is relatively low. Summary of the invention

[0007] The present invention aims to provide a nitrogen foam cement slurry system and its preparation method and application in view of the above-mentioned deficiencies in the prior art. The nitrogen foam cement slurry system of the present invention has the characteristics of small density difference and high strength. The minimum density difference between the upper and lower layers can reach 0.003 g / cm 3 ; After mixing with G-grade oil well cement, the strength reaches over 32MPa.

[0008] One of the purposes of the present invention is to disclose a nitrogen foam cement slurry system, the nitrogen foam cement slurry system comprising: Foaming agent 0.15-0.3 parts by mass; Foam stabilizer 0.1-0.2 parts by mass; 2-4 parts by weight of strength retaining agent; 230-260 parts by mass of G-grade oil well cement; 100 parts by mass of tap water.

[0009] The foam stabilizer is one or more of gelatin, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium α-olefin sulfonate.

[0010] The strength retaining agent is microsilica powder or nano silicon dioxide or a mixture of the two.

[0011] The molecular structural formula of the foaming agent is as follows: .

[0012] Another object of the present invention is to disclose a method for preparing the nitrogen foam cement slurry system. The specific steps of the preparation method are as follows: (1) Add 2-aminoethanol hydrogen sulfate, solvent, and 2-bromododecanoic acid into a reactor, stir evenly, heat to reflux, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) Stir the foaming agent, foam stabilizer and tap water in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry mixing cup, stir at a low speed in a nitrogen atmosphere, add a strength retaining agent and G-grade oil well cement, and obtain a cement slurry; (5) The cement slurry is stirred at high speed to obtain a nitrogen foam cement slurry system.

[0013] In the present invention, preferably, based on 1 mole of 2-aminoethanol hydrogen sulfate, the amount of 2-bromododecanoic acid used is 1.5-2.5 moles.

[0014] More preferably, based on 1 mole of 2-aminoethanol hydrogen sulfate, the amount of 2-bromododecanoic acid used is 1.8-2.2 moles.

[0015] In the present invention, preferably, the organic solvent described in step (1) is one of methanol, ethanol, propanol, isopropanol, butanol and isobutanol, and the weight ratio of the organic solvent to 2-aminoethanol hydrogen sulfate is 20-40:1.

[0016] More preferably, the organic solvent is ethanol or isobutanol.

[0017] In the present invention, preferably, the heating reflux time in step (1) is 12-48 hours.

[0018] In the present invention, preferably, the stirring at a low speed in step (4) is stirring at a rotation speed of 300-500 r / min for 5-20 min.

[0019] In the present invention, preferably, the high-speed stirring in step (5) is stirring at a speed of 10000-12000 r / min for 3-10 min.

[0020] The foaming agent synthesis reaction equation of the present invention is as follows: ; The third object of the present invention is to disclose the application of the nitrogen foam cement slurry system in oil field cementing.

[0021] The nitrogen foam cement slurry system of the present invention is composed of a foaming agent, a foam stabilizer, water, a strength retainer, and oil well cement. The foaming agent is an anionic surfactant, the lipophilic group is two dodecyl groups, and the hydrophilic group is two carboxyl groups and a sulfate group. The dodecyl group points to the gas inside the bubble, and the sulfate group points to the liquid outside the bubble, forming a monomolecular film or a multimolecular film with certain elasticity and toughness. This film can effectively prevent the mutual diffusion of the gas inside the bubble and the external liquid, so that the bubble can exist relatively stably. Both the carboxyl group and the sulfate group carry a negative charge, and the present invention adsorbed on the bubble membrane wall will make the bubble carry the same charge. According to the principle of like repels like, electrostatic repulsion will be generated between the bubbles, thereby inhibiting the merging and rupture of the bubbles and enhancing the stability of the foam. The foam stabilizer can control the structural stability of the bubble liquid film, so that the surfactant molecules are orderly distributed on the bubble liquid film, thereby giving the foam good elasticity and self-repairing ability. The strength retainer can make the cement product reach a higher strength in a shorter time and can resist a certain external pressure.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The nitrogen foam cement slurry system of the present invention has the characteristic of small density difference, and the minimum density difference between the upper and lower layers is 0.003 g / cm 3 ; (2) The nitrogen foam cement slurry system of the present invention has the characteristic of high strength of the foam cement slurry. After being mixed with G-grade oil well cement, the strength reaches above 32 MPa. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] The technical solution of the present invention is further described below in conjunction with specific embodiments: Example 1

[0025] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 282 g of methanol, and 0.15 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.45 g of foaming agent, 0.3 g of gelatin, and 300 g of tap water are mixed uniformly in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 6 g of microsilica powder and 690 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 400 r / min, and stir for 10 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 10000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0026] Example 2

[0027] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 423 g of propanol, and 0.25 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 48 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.54 g of foaming agent, 0.45 g of gelatin, and 300 g of tap water are mixed uniformly in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 6.5 g of microsilica powder and 700 g of G-grade oil well cement at a speed of 400 r / min in a nitrogen atmosphere, and stir for 10 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 10,000 r / min for 8 min to obtain a nitrogen foam cement slurry system.

[0028] Example 3

[0029] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 301 g of ethanol, and 0.16 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 12 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.6 g of foaming agent, 0.6 g of carboxymethyl cellulose, and 300 g of tap water are stirred uniformly in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 7 g of microsilica powder and 720 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 400 r / min, and stir for 10 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 11000 r / min for 6 min to obtain a nitrogen foam cement slurry system.

[0030] Example 4

[0031] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 400 g of isopropanol, and 0.24 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.69 g of a foaming agent, 0.54 g of carboxymethyl cellulose, and 300 g of tap water were mixed uniformly in proportion to obtain an aqueous phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 7 g of nano-silicon dioxide and 740 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 300 r / min, and stir for 20 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 11000 r / min for 3 min to obtain a nitrogen foam cement slurry system.

[0032] Example 5

[0033] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 350 g of butanol, and 0.18 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.75 g of foaming agent, 0.6 g of hydroxyethyl cellulose, and 300 g of tap water were mixed uniformly in proportion to obtain an aqueous phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 7 g of nano-silicon dioxide and 740 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 300 r / min, and stir for 15 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 10500 r / min for 5 min to obtain a nitrogen foam cement slurry system.

[0034] Example 6

[0035] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 382 g of isobutyl alcohol, and 0.22 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 36 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.9 g of a foaming agent, 0.45 g of sodium α-olefin sulfonate, and 300 g of tap water are stirred uniformly in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 7 g of nano-silicon dioxide and 760 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 450 r / min, and stir for 5 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 10500 r / min for 5 min to obtain a nitrogen foam cement slurry system.

[0036] Example 7

[0037] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 412 g of ethanol, and 0.2 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.9 g of a foaming agent, 0.6 g of sodium α-olefin sulfonate, and 300 g of tap water are stirred uniformly in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 2 g of microsilica powder, 6 g of nano-silicon dioxide, and 780 g of G-grade oil well cement at a speed of 450 r / min in a nitrogen atmosphere, and stir for 10 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 12000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0038] Example 8

[0039] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 564 g of methanol, and 0.21 mol of 2-bromododecanoic acid into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) 0.9 g of a foaming agent, 0.45 g of sodium α-olefin sulfonate, 0.15 g of hydroxyethyl cellulose, and 300 g of tap water were mixed uniformly in proportion to obtain an aqueous phase; (4) Add the above-mentioned water phase into a foam cement slurry stirring cup, add 4 g of microsilica powder, 4 g of nano-silicon dioxide, and 780 g of G-grade oil well cement in a nitrogen atmosphere at a speed of 500 r / min, and stir for 5 min to obtain cement slurry; (5) The cement slurry was stirred at a rotation speed of 12000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0040] Comparative Example 1 The preparation process is the same as step (3) to step (5) of Example 8, except that 0.9 g of the foaming agent is replaced with 0.9 g of sodium lauryl polyoxyethylene ether sulfate.

[0041] Comparative Example 2 The preparation process is the same as step (3) to step (5) of Example 8, except that sodium α-olefin sulfonate is not added.

[0042] Comparative Example 3 The preparation process is the same as step (3) to step (5) of Example 8, except that microsilica powder and nano silicon dioxide are not added.

[0043] Test Example 1 Density Test The densities of the upper and lower layers of Examples 1-8 and Comparative Examples 1-3 were tested with reference to the method of GB / T39533-2020 “Preparation and Test Method of Foamed Cement Slurry under Normal Pressure”. The test results are shown in Table 1.

[0044] Test Example 2 Strength Test Examples 1-8 and Comparative Examples 1-3 were placed in a curing mold and cured at 60° C. for 72 hours before testing the compressive strength.

[0045] The test results are shown in Table 1.

[0046] Table 1 Density and strength test results of foam cement slurry

[0047] It can be seen from Table 1 that: (1) The nitrogen foam cement slurry system (Examples 1-8) of the present invention has the characteristic of small density difference, and the minimum density difference between the upper and lower layers is 0.003 g / cm 3 (Examples 7 and 8).

[0048] (2) The nitrogen foam cement slurry system (Examples 1-8) of the present invention has the characteristic of high strength of the foam cement slurry. The strength of the cement slurry reaches above 32 MPa, and the highest reaches 35.1 MPa (Example 6).

[0049] (3) The density difference between the upper and lower layers of the nitrogen foam cement slurry system (Example 8) of the present invention is 0.003 g / cm 3 , cement slurry strength is 35MPa; ①Comparative Example 1: The density difference between the upper and lower layers reaches 0.018 g / cm 3, the cement slurry strength is 25.6MPa. Compared with Example 8, the density difference between the upper and lower layers and the cement slurry strength are significantly higher than those of the present invention. It can be seen that the foaming agent has a great influence on the density difference between the upper and lower layers and the cement slurry strength of the nitrogen foam cement slurry system. At the same time, it is shown that the foaming agent of the present invention is significantly better than the foaming agent sodium lauryl polyoxyethylene ether sulfate in Comparative Example 1; ②Comparative Example 2: The density difference between the upper and lower layers reaches 0.01g / cm 3 , the cement slurry strength is 34.5MPa. Compared with Example 8, the density difference between the upper and lower layers is significantly higher than that of the present invention, while the cement slurry strength does not change significantly. It can be seen that the foam stabilizer mainly affects the density difference between the upper and lower layers of the nitrogen foam cement slurry system, but has little effect on the cement slurry strength. ③Comparative Example 3: The density difference between the upper and lower layers reaches 0.003 g / cm 3 The cement slurry strength is 32.5 MPa. Compared with Example 8, the cement slurry strength is significantly lower than that of the present invention, while the density difference between the upper and lower layers does not change significantly. It can be seen that the strength retaining agent mainly affects the cement slurry strength of the nitrogen foam cement slurry system, but has little effect on the density difference between the upper and lower layers.

[0050] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0051] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0052] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A nitrogen foam cement slurry system, characterized in that: The nitrogen foam cement slurry system comprises: Foaming agent 0.15-0.3 parts by mass; Foam stabilizer 0.1-0.2 parts by mass; 2-4 parts by weight of strength retaining agent; 230-260 parts by mass of G-grade oil well cement; 100 parts by mass of tap water; The foam stabilizer is one or more of gelatin, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium α-olefin sulfonate; The strength retaining agent is microsilica powder or nano silicon dioxide or a mixture of the two; The molecular structural formula of the foaming agent is as follows: 。 2. The method for preparing the nitrogen foam cement slurry system according to claim 1, characterized in that: The specific steps of the preparation method are as follows: (1) Add 2-aminoethanol hydrogen sulfate, solvent, and 2-bromododecanoic acid into a reactor, stir evenly, heat to reflux, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent; (3) Stir the foaming agent, foam stabilizer and tap water in proportion to obtain a water phase; (4) Add the above-mentioned water phase into a foam cement slurry mixing cup, stir at a low speed in a nitrogen atmosphere, add a strength retaining agent and G-grade oil well cement, and obtain a cement slurry; (5) stirring the cement slurry at a high speed to obtain a nitrogen foam cement slurry system; Based on 1 mole of 2-aminoethanol hydrogen sulfate, the amount of 2-bromododecanoic acid used is 1.5-2.5 moles.

3. The preparation method according to claim 2, characterized in that: Based on 1 mole of 2-aminoethanol hydrogen sulfate, the amount of 2-bromododecanoic acid used is 1.8-2.2 moles.

4. The preparation method according to claim 2, characterized in that: The organic solvent described in step (1) is one of methanol, ethanol, propanol, isopropanol, butanol and isobutanol, and the weight ratio of the organic solvent to 2-aminoethanol hydrogen sulfate is 20-40:

1.

5. The preparation method according to claim 4, characterized in that: The organic solvent is ethanol or isobutanol.

6. The preparation method according to claim 2, characterized in that: The heating reflux time in step (1) is 12-48 hours.

7. The preparation method according to claim 2, characterized in that: The stirring at low speed in step (4) is stirring at a speed of 300-500 r / min for 5-20 min.

8. The preparation method according to claim 2, characterized in that: The high-speed stirring in step (5) is stirring at a speed of 10000-12000 r / min for 3-10 min.

9. Use of the nitrogen foam cement slurry system according to claim 1 in oil field cementing.

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