A nitrogen foam cement slurry system and its preparation method and application

Abstract

The present invention belongs to the field of oil production technology, and in particular to a nitrogen foam cement slurry system and its preparation method and application. The preparation method is as follows: 2-aminoethanol hydrogen sulfate, solvent, and 2-bromododecanoic acid are added to the reactor, stirred evenly, heated to reflux, and adjusted and maintained at a pH of 8-9 with sodium hydroxide; vacuum distillation obtains a viscous liquid, which is recrystallized with cyclohexane to obtain a solid, dried, and a foaming agent is obtained; the foaming agent, foam stabilizer, and tap water are stirred evenly in proportion to obtain an aqueous phase; the above-mentioned aqueous phase is added to a foam cement slurry stirring cup, stirred at a low speed in a nitrogen atmosphere, and a strength retainer and G-grade oil well cement are added to obtain a cement slurry; the above-mentioned cement slurry is stirred at a high speed to obtain a nitrogen foam cement slurry system. The nitrogen foam cement slurry system of the present invention 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] Cementing is a critical step in the exploration and development of oil and gas wells. As oil and gas exploration and development progresses into deep, complex formations, and specialized reservoirs, increasingly higher requirements are placed on cementing quality. Traditional cement slurry systems are gradually exposing their limitations under certain special operating conditions. For example, in deep and ultra-deep wells, high-temperature and high-pressure environments can easily lead to deterioration of cement slurry performance, resulting in strength decay and difficulty controlling thickening time. In low-pressure, leaky formations, conventional cement slurry has a relatively high density, which can easily cause leakage from the formation, leading to cement slurry loss. This, in turn, affects the cementing sealing effect, potentially leading to serious consequences such as oil, gas, and water channeling, and reducing the production life and safety of oil and gas wells.

[0003] To address these issues, nitrogen foam cement slurry systems are gaining attention as a new cementing material. Nitrogen, an inert gas, exhibits excellent compressibility and low density. Introducing nitrogen into the cement slurry system in the form of foam significantly reduces the density of the slurry, effectively addressing the cementing challenge in low-pressure, leaky formations. Furthermore, the closed air cavities formed by the nitrogen foam within the cement slurry enhance the thermal resistance and toughness of the cement paste, improving the overall performance of the slurry.

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

[0005] CN103525387B discloses a novel chemically nitrogen-filled foamed cement slurry. The components and weight ratios of the novel chemically nitrogen-filled foamed cement slurry system are as follows: 100 parts oil well cement, 0.5-2.0 parts gas generating agent I, 0.5-2.0 parts gas generating agent II, 0.7-2.5 parts foam stabilizer, 1.0-10 parts fluid loss additive, 0.1-0.5 parts dispersant, 0.3-1.0 parts retarder, 1.0-4.0 parts early strength agent, and 48-70 parts water. However, the foamed cement slurry of this invention has poor stability, and the resulting cement paste has low strength.

[0006] CN109400205A discloses a cement slurry comprising cement, a fluid loss additive, a dispersant, a foaming agent, a foam stabilizer, an accelerator, and water, wherein the foaming agent comprises a protein-based foaming agent. The invention also provides a foamed cement slurry system based on the cement slurry and a method for applying the cement slurry. The cement slurry provided by the present invention is filled with bubbles, which enhances the stability of the introduced bubbles. The foamed cement stone formed after solidification exhibits higher strength and improved elasticity and plasticity. However, the compressive strength of the cement slurry formed by this invention is only approximately 10 MPa, resulting in relatively low strength. Summary of the Invention

[0007] The present invention addresses the deficiencies of the above-mentioned prior art and provides a nitrogen foam cement slurry system and its preparation method and application. 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 above 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:

[0009] 0.15-0.3 parts by mass of foaming agent;

[0010] Foam stabilizer 0.1-0.2 parts by mass;

[0011] 2-4 parts by mass of strength retaining agent;

[0012] 230-260 parts by mass of Grade G oil well cement;

[0013] 100 parts by mass of tap water.

[0014] The foam stabilizer is one or more of gelatin, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium α-olefin sulfonate.

[0015] The strength retaining agent is microsilica powder or nano silicon dioxide or a mixture of the two.

[0016] The molecular structural formula of the foaming agent is as follows:

[0017] .

[0018] 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:

[0019] (1) Add 2-aminoethanol hydrogen sulfate, solvent, and 2-bromododecanoic acid into the reactor, stir evenly, heat to reflux, and adjust and maintain the pH at 8-9 with sodium hydroxide;

[0020] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0021] (3) Stir the foaming agent, foam stabilizer and tap water in proportion to obtain a water phase;

[0022] (4) Add the above-mentioned water phase into the 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 to obtain a cement slurry;

[0023] (5) The above cement slurry is stirred at high speed to obtain a nitrogen foam cement slurry system.

[0024] 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.

[0025] More preferably, based on 1 mole of 2-aminoethanol hydrogen sulfate, the amount of 2-bromododecanoic acid used is 1.8-2.2 moles.

[0026] In the present invention, preferably, the organic solvent 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.

[0027] More preferably, the organic solvent is ethanol or isobutanol.

[0028] In the present invention, preferably, the heating reflux time in step (1) is 12-48 hours.

[0029] 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.

[0030] In the present invention, preferably, the high-speed stirring in step (5) is stirring at a speed of 10,000-12,000 r / min for 3-10 min.

[0031] The foaming agent synthesis reaction equation of the present invention is as follows:

[0032] ;

[0033] The third object of the present invention is to disclose the application of the nitrogen foam cement slurry system in oil field cementing.

[0034] The nitrogen foam cement slurry system of the present invention is composed of a foaming agent, a foam stabilizer, water, a strength retaining agent, and oil well cement. The foaming agent is an anionic surfactant with two dodecyl groups as lipophilic groups and two carboxyl groups and a sulfate group as hydrophilic groups. The dodecyl groups point toward the gas inside the bubbles, and the sulfate groups point toward the liquid outside the bubbles, forming a monomolecular or multimolecular membrane with a certain degree of elasticity and toughness. This membrane can effectively prevent the mutual diffusion of the gas inside the bubbles and the external liquid, allowing the bubbles to exist relatively stably. Both the carboxyl groups and the sulfate groups carry a negative charge, and the present invention adsorbed on the bubble membrane wall will cause the bubbles to have the same charge. Based on the principle of like charges repel, electrostatic repulsion is 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 membrane, so that the surfactant molecules are distributed in an orderly manner on the bubble liquid membrane, thereby giving the foam good elasticity and self-repairing ability. The strength retaining agent can enable cement products to achieve higher strength in a shorter period of time and be able to withstand certain external pressures.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] (1) The nitrogen foam cement slurry system of the present invention has the characteristic of small density difference, and the density difference between the upper and lower layers is as small as 0.003 g / cm 3 ;

[0037] (2) The nitrogen foam cement slurry system of the present invention has the characteristic of high foam cement slurry strength. After being mixed with G-grade oil well cement, the strength reaches above 32 MPa. DETAILED DESCRIPTION

[0038] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0039] The technical solution of the present invention is further described below with reference to specific embodiments:

[0040] Example 1

[0041] (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;

[0042] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0043] (3) Mix 0.45 g of foaming agent, 0.3 g of gelatin, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0044] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 6g of microsilica powder and 690g of G-grade oil well cement at a speed of 400 r / min in a nitrogen atmosphere, and stir for 10 minutes to obtain cement slurry;

[0045] (5) The cement slurry was stirred at a speed of 10,000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0046] Example 2

[0047] (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;

[0048] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0049] (3) Mix 0.54 g of foaming agent, 0.45 g of gelatin, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0050] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 6.5g of microsilica powder and 700g of G-grade oil well cement at a speed of 400 r / min in a nitrogen atmosphere, and stir for 10 minutes to obtain cement slurry;

[0051] (5) The above cement slurry was stirred at a speed of 10,000 r / min for 8 min to obtain a nitrogen foam cement slurry system.

[0052] Example 3

[0053] (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;

[0054] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0055] (3) Mix 0.6 g of foaming agent, 0.6 g of carboxymethyl cellulose, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0056] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 7g of microsilica powder and 720g of G-grade oil well cement at a speed of 400 r / min in a nitrogen atmosphere, and stir for 10 minutes to obtain cement slurry;

[0057] (5) The cement slurry was stirred at a speed of 11,000 r / min for 6 min to obtain a nitrogen foam cement slurry system.

[0058] Example 4

[0059] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 400 g of isopropyl alcohol, 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;

[0060] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0061] (3) Mix 0.69 g of foaming agent, 0.54 g of carboxymethyl cellulose, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0062] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 7g of nano-silica and 740g 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;

[0063] (5) The above cement slurry was stirred at a speed of 11000 r / min for 3 min to obtain a nitrogen foam cement slurry system.

[0064] Example 5

[0065] (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;

[0066] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0067] (3) Mix 0.75 g of foaming agent, 0.6 g of hydroxyethyl cellulose, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0068] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 7g of nano-silica and 740g 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;

[0069] (5) The cement slurry was stirred at a speed of 10500 r / min for 5 min to obtain a nitrogen foam cement slurry system.

[0070] Example 6

[0071] (1) Add 0.1 mol of 2-aminoethanol hydrogen sulfate, 382 g of isobutanol, 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;

[0072] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0073] (3) Mix 0.9 g of foaming agent, 0.45 g of sodium α-olefin sulfonate, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0074] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 7g of nano-silica and 760g of G-grade oil well cement at a speed of 450 r / min in a nitrogen atmosphere, and stir for 5 minutes to obtain cement slurry;

[0075] (5) The cement slurry was stirred at a speed of 10500 r / min for 5 min to obtain a nitrogen foam cement slurry system.

[0076] Example 7

[0077] (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;

[0078] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0079] (3) Mix 0.9 g of foaming agent, 0.6 g of sodium α-olefin sulfonate, and 300 g of tap water in appropriate proportions to obtain an aqueous phase;

[0080] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 2g of microsilica powder, 6g of nano-silica, and 780g of G-grade oil well cement at a speed of 450 r / min in a nitrogen atmosphere, and stir for 10 minutes to obtain cement slurry;

[0081] (5) The cement slurry was stirred at a speed of 12000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0082] Example 8

[0083] (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;

[0084] (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with cyclohexane to obtain a solid, and drying to obtain a foaming agent;

[0085] (3) 0.9 g of 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;

[0086] (4) Add the above-mentioned water phase to the foam cement slurry mixing cup, add 4g of microsilica powder, 4g of nano-silica, and 780g of G-grade oil well cement at a speed of 500 r / min in a nitrogen atmosphere, and stir for 5 minutes to obtain cement slurry;

[0087] (5) The cement slurry was stirred at a speed of 12000 r / min for 10 min to obtain a nitrogen foam cement slurry system.

[0088] Comparative Example 1

[0089] 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.

[0090] Comparative Example 2

[0091] The preparation process is the same as step (3) to step (5) of Example 8, except that sodium α-olefin sulfonate is not added.

[0092] Comparative Example 3

[0093] The preparation process is the same as step (3) to step (5) of Example 8, except that microsilica powder and nano-silica are not added.

[0094] Test Example 1 Density Test

[0095] 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 Foam Cement Slurry under Normal Pressure”. The test results are shown in Table 1.

[0096] Test Example 2 Strength Test

[0097] 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.

[0098] The test results are shown in Table 1.

[0099] Table 1 Density and strength test results of foam cement slurry

[0100]

[0101] As can be seen from Table 1:

[0102] (1) The nitrogen foam cement slurry system of the present invention (Examples 1-8) has the characteristic of small density difference, and the density difference between the upper and lower layers is as small as 0.003 g / cm 3 (Examples 7 and 8).

[0103] (2) The nitrogen foam cement slurry system of the present invention (Examples 1-8) has the characteristic of high foam cement slurry strength. The cement slurry strength reaches above 32 MPa, and the highest reaches 35.1 MPa (Example 6).

[0104] (3) The density difference between the upper and lower layers of the nitrogen foam cement slurry system of the present invention (Example 8) is 0.003 g / cm 3 , cement slurry strength is 35MPa;

[0105] ① The density difference between the upper and lower layers of Comparative Example 1 reached 0.018 g / cm 3 The cement slurry strength is 25.6 MPa. 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. This shows 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 shows that the foaming agent of the present invention is significantly better than the foaming agent sodium lauryl polyoxyethylene ether sulfate in Comparative Example 1.

[0106] ②Comparative Example 2: The density difference between the upper and lower layers reaches 0.01g / cm 3 The cement slurry strength is 34.5 MPa. 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. This shows 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.

[0107] ③ The density difference between the upper and lower layers of comparative example 3 reaches 0.003g / 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.

[0108] 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, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0109] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0110] In addition, the 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: 0.15-0.3 parts by mass of foaming agent; Foam stabilizer 0.1-0.2 parts by mass; 2-4 parts by mass of strength retaining agent; 230-260 parts by mass of Grade G 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: ； The specific steps of the preparation method of the nitrogen foam cement slurry system are as follows: (1) Add 2-aminoethanol hydrogen sulfate, solvent, and 2-bromododecanoic acid into the 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 the 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 to obtain a cement slurry; (5) stirring the cement slurry at 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.

2. The nitrogen foam cement slurry system according to claim 1, 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.

3. The nitrogen foam cement slurry system according to claim 1, characterized in that: The solvent in step (1) is one of methanol, ethanol, propanol and butanol, and the weight ratio of the solvent to 2-aminoethanol hydrogen sulfate is 20-40:

1.

4. The nitrogen foam cement slurry system according to claim 3, characterized in that: The solvent is ethanol or isobutanol.

5. The nitrogen foam cement slurry system according to claim 1, characterized in that: The heating reflux time in step (1) is 12-48 hours.

6. The nitrogen foam cement slurry system according to claim 1, 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.

7. The nitrogen foam cement slurry system according to claim 1, characterized in that: The high-speed stirring in step (5) is stirring at a speed of 10,000-12,000 r / min for 3-10 min.

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

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