Floating-bead-free low-density oil well cement paste

Abstract

The invention provides floating bead-free low-density oil well cement paste, which is prepared from the following raw materials in percentage by weight: 35 to 45 percent of oil well cement, 15 to 25 percent of organic polymer emulsion, 1 to 3 percent of fluid loss agent, 2 to 4 percent of modified nitrile rubber particles, 0.1 to 0.2 percent of dispersing agent, 0.1 to 0.2 percent of thickening agent, 0.1 to 0.2 percent of defoaming agent and the balance of water. The floating-bead-free low-density oil well cement paste has the advantages of stable chemical performance, acid and alkali corrosion resistance, high early strength, high toughness of cured cement, high crack resistance and the like, and the service life of well cementation cement is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of well cement slurry, and in particular to low-density oil well cement slurry without floating beads. Background Art

[0002] Among the existing general technologies, the most commonly used cementing system for low-pressure and leaky formations is the floating bead low-density cement slurry system, which has the advantages of low density and high compressive strength, but the floating bead is a hollow glass body. Under a certain pressure, water will enter the hollow ball through the pores on the floating bead, which allows liquids containing various chemical admixtures to enter the floating bead, which is easy to increase the slurry density, compress the leaky formation, and reduce the expected cementing effect. Non-floating bead fly ash low-density cement is used to maintain the designed density, but the current domestic fly ash low-density cement has low early strength, poor slurry fluidity, poor stability, and short service life, which cannot meet the requirements of cement performance for cementing in low-pressure formation oil fields.

[0003] Therefore, for oil well cementing, the traditional low-density cement slurry with floating beads is difficult to meet the requirements of reinforcement performance. It is necessary to design a low-density oil well cement slurry without floating beads that can solve the problems of low early strength, poor slurry fluidity, poor stability and short service life of the existing non-floating bead fly ash low-density cement. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a low-density oil well cement slurry without floating beads, which is suitable for cementing oil fields in low-pressure formations and can meet the needs of oil field cementing and later development. Its high strength and resistance to high-temperature decay enable it to maintain stable performance in high-temperature environments, replacing ordinary low-density cement slurry with floating beads, and is suitable for various complex oil well cementing projects.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] The present application discloses a low-density oil well cement slurry without floating beads. The components of the oil well cement slurry include the following raw materials by weight percentage: 35-45% of oil well cement, 15-25% of organic polymer emulsion, 1-3% of fluid loss reducer, 2-4% of modified nitrile rubber particles, 0.1-0.2% of dispersant, 0.1-0.2% of thickener, 0.1-0.2% of defoamer, and the balance is water.

[0007] Preferably, the components of the well cement slurry include the following raw materials by weight percentage: 40% oil well cement, 20% organic polymer emulsion, 2% fluid loss reducer, 3% modified nitrile rubber particles, 0.15% dispersant, 0.15% thickener, 0.15% defoamer, and the balance is water.

[0008] Preferably, the preparation method of the modified nitrile rubber particles is: take nitrile rubber particles, spread them evenly in a glass container, put them into a low-temperature plasma surface treatment instrument, start the power supply and the vacuum pump, adjust the cavity pressure to 10Pa, open the flow valve to allow air to pass, and when the current flow rate is consistent with the set flow rate, turn on the high-frequency power supply for discharge treatment for 3 minutes, turn off the high-frequency power supply, the flow valve and the vacuum pump, and obtain the modified nitrile rubber particles.

[0009] Preferably, the composition of the well cement slurry includes the following raw materials in parts by weight: 2% polypropylene fiber.

[0010] Preferably, the preparation method of low-density oil well cement slurry without floating beads is: mix the fluid loss reducer, organic polymer emulsion and water evenly, stir them under slow stirring conditions for 20 seconds using a cement slurry mixer, add oil well cement, polypropylene fiber, modified nitrile rubber particles, dispersant, thickener and defoamer while stirring, then stir at high speed for 40 seconds, pour the stirred cement slurry into a cubic mold, and then put the mold into the condition of 70°C-75°C for curing for 2 days.

[0011] Preferably, the slow stirring speed is 3500 r / min.

[0012] Preferably, the speed of high-speed stirring is 12000 r / min.

[0013] Preferably, the organic polymer emulsion is at least one of epoxy resin emulsion, phenolic resin emulsion or polyurethane resin emulsion.

[0014] Preferably, the solid content of the organic polymer emulsion is 60%.

[0015] Preferably, the fluid loss agent is at least one of polyvinyl alcohol or PC-G80L.

[0016] The beneficial effects of the present invention are:

[0017] Polypropylene fiber has the advantages of stable chemical properties, non-water absorption, acid and alkali corrosion resistance, and no reaction with other components in cement. The addition of polypropylene fiber can significantly improve the impact resistance of cementing cement. Polypropylene fiber forms a dense network structure in cementing cement slurry, which can shield the stress field at the crack tip of cement defects and improve the fracture toughness of cement.

[0018] After being treated by a low-temperature plasma surface treatment instrument, the wettability of the surface of the nitrile rubber particles is significantly enhanced, the contact angle is reduced, the specific surface area is increased, the surface O / C ratio is increased, and the hydrophilicity is improved. The modified nitrile rubber particles are filled into the cementing cement slurry, and the adhesion with the cement slurry body and the slurry flowability are improved. The particles are filled in the network structure formed by the cement hydrate, which changes the fracture development direction of the cement slurry after solidification, improves the early strength of the low-density oil well cement slurry, the toughness and crack resistance of the cement slurry after solidification, and further extends the stability and service life of the product.

[0019] Organic polymer emulsion will demulsify and evaporate water when exposed to 70℃-75℃ for a long time, but the epoxy groups in the organic polymer emulsion still exist, and no three-dimensional network cross-linking curing reaction occurs, presenting a relatively large gel. The gel wraps the oil well cement particles, reducing the contact area between the cement particles and free water, hindering the migration of ions in the pore solution inside the cement mortar, filling the gaps in the cement molecules, improving the pore structure of the cement, and improving the axial compressive strength and toughness of the oil well cement after solidification, reducing the probability of cement cracking, which is beneficial to extending the service life of the cementing cement. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Embodiment 1:

[0022] The present embodiment discloses a low-density oil well cement slurry without floating beads. The components of the oil well cement slurry include the following raw materials by weight percentage: 35% of oil well cement, 15% of organic polymer emulsion, 1% of fluid loss reducer, 2% of polypropylene fiber, 2% of modified nitrile rubber particles, 0.1% of dispersant, 0.1% of thickener, 0.1% of defoamer, and the balance is water.

[0023] The preparation method of modified nitrile rubber particles is as follows: take nitrile rubber particles, spread them evenly in a glass container, put them into a low-temperature plasma surface treatment instrument, start the power supply and the vacuum pump, adjust the cavity pressure to 10Pa, open the flow valve to allow air to pass, and when the current flow rate is consistent with the set flow rate, turn on the high-frequency power supply for discharge treatment for 3 minutes, turn off the high-frequency power supply, the flow valve and the vacuum pump, and obtain the modified nitrile rubber particles.

[0024] The preparation method of low-density oil well cement slurry without floating beads is as follows: mix the fluid loss reducer, organic polymer emulsion and water evenly, use a cement slurry mixer to slowly stir at a speed of 3500r / min for 20s, add oil well cement, polypropylene fiber, modified nitrile rubber particles, dispersant, thickener and defoamer while stirring, then stir at a high speed of 12000r / min for 40s, pour the stirred cement slurry into a cubic mold, and then put the mold into 70°C for curing for 2 days.

[0025] The organic polymer emulsion is epoxy resin emulsion with a solid content of 60%; and the fluid loss reducer is polyvinyl alcohol.

[0026] Embodiment 2:

[0027] The present embodiment discloses a low-density oil well cement slurry without floating beads. The components of the oil well cement slurry include the following raw materials by weight percentage: 45% of oil well cement, 25% of organic polymer emulsion, 3% of fluid loss reducer, 2% of polypropylene fiber, 4% of modified nitrile rubber particles, 0.2% of dispersant, 0.2% of thickener, 0.2% of defoamer, and the balance is water.

[0028] The preparation method of modified nitrile rubber particles is as follows: take nitrile rubber particles, spread them evenly in a glass container, put them into a low-temperature plasma surface treatment instrument, start the power supply and the vacuum pump, adjust the cavity pressure to 10Pa, open the flow valve to allow air to pass, and when the current flow rate is consistent with the set flow rate, turn on the high-frequency power supply for discharge treatment for 3 minutes, turn off the high-frequency power supply, the flow valve and the vacuum pump, and obtain the modified nitrile rubber particles.

[0029] The preparation method of low-density oil well cement slurry without floating beads is as follows: mix the fluid loss reducer, organic polymer emulsion and water evenly, use a cement slurry mixer to slowly stir at a speed of 3500r / min for 20s, add oil well cement, polypropylene fiber, modified nitrile rubber particles, dispersant, thickener and defoamer while stirring, then stir at a high speed of 12000r / min for 40s, pour the stirred cement slurry into a cubic mold, and then put the mold into 75°C for curing for 2 days.

[0030] The organic polymer emulsion is a phenolic resin emulsion with a solid content of 60%; and the fluid loss agent is PC-G80L.

[0031] Embodiment 3:

[0032] The present embodiment discloses a low-density oil well cement slurry without floating beads. The components of the oil well cement slurry include the following raw materials by weight percentage: 40% oil well cement, 20% organic polymer emulsion, 2% fluid loss additive, 2% polypropylene fiber, 3% modified nitrile rubber particles, 0.15% dispersant, 0.15% thickener, 0.15% defoamer, and the balance is water.

[0033] The preparation method of modified nitrile rubber particles is as follows: take nitrile rubber particles, spread them evenly in a glass container, put them into a low-temperature plasma surface treatment instrument, start the power supply and the vacuum pump, adjust the cavity pressure to 10Pa, open the flow valve to allow air to pass, and when the current flow rate is consistent with the set flow rate, turn on the high-frequency power supply for discharge treatment for 3 minutes, turn off the high-frequency power supply, the flow valve and the vacuum pump, and obtain the modified nitrile rubber particles.

[0034] The preparation method of low-density oil well cement slurry without floating beads is as follows: mix the fluid loss reducer, organic polymer emulsion and water evenly, use a cement slurry mixer to slowly stir at a speed of 3500r / min for 20s, add oil well cement, polypropylene fiber, modified nitrile rubber particles, dispersant, thickener and defoamer while stirring, then stir at a high speed of 12000r / min for 40s, pour the stirred cement slurry into a cubic mold, and then put the mold into 75°C for curing for 2 days.

[0035] The organic polymer emulsion is a polyurethane resin emulsion with a solid content of 60%; and the fluid loss reducer is polyvinyl alcohol.

[0036] Comparative Example 1:

[0037] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that no polyurethane resin emulsion is added.

[0038] Comparative Example 2:

[0039] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that: no modified nitrile rubber particles are added.

[0040] Comparative Example 3:

[0041] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that ordinary nitrile rubber particles are used to replace the modified nitrile rubber particles.

[0042] Comparative Example 4:

[0043] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that no polypropylene fiber is added.

[0044] Comparative Example 5:

[0045] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 20%.

[0046] Comparative Example 6:

[0047] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 30%.

[0048] Comparative Example 7:

[0049] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 40%.

[0050] Comparative Example 8:

[0051] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 50%.

[0052] Comparative Example 9:

[0053] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 70%.

[0054] Comparative Example 10:

[0055] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 80%.

[0056] Comparative Example 11:

[0057] A low-density oil well cement slurry without floating beads, the difference between the oil well cement slurry and Example 3 is that the solid content of the polyurethane resin emulsion is 90%.

[0058] The well cement slurries obtained in the above Examples 1-3 and Comparative Examples 1-11 were subjected to performance tests to measure the comprehensive performance of the well cement slurries. The results are shown in Table 1.

[0059] Table 1 Performance parameters of well cement slurry obtained in Examples 1-3 and Comparative Examples 1-11

[0060]

[0061] In summary, polypropylene fiber has the advantages of stable chemical properties, non-water absorption, acid and alkali corrosion resistance, and no reaction with other components in cement. The addition of polypropylene fiber can significantly improve the impact resistance of cementing cement. Polypropylene fiber forms a dense network structure in cementing cement slurry, which can shield the stress field at the crack tip of cement defects and improve the fracture toughness of cement.

[0062] After being treated by a low-temperature plasma surface treatment instrument, the wettability of the surface of the nitrile rubber particles is significantly enhanced, the contact angle is reduced, the specific surface area is increased, the surface O / C ratio is increased, and the hydrophilicity is improved. The modified nitrile rubber particles are filled into the cementing cement slurry, and the adhesion with the cement slurry body and the slurry flowability are improved. The particles are filled in the network structure formed by the cement hydrate, which changes the fracture development direction of the cement slurry after solidification, improves the early strength of the low-density oil well cement slurry, the toughness and crack resistance of the cement slurry after solidification, and further extends the stability and service life of the product.

[0063] Organic polymer emulsion will demulsify and evaporate water when exposed to 70℃-75℃ for a long time, but the epoxy groups in the organic polymer emulsion still exist, and no three-dimensional network cross-linking curing reaction occurs, presenting a relatively large gel. The gel wraps the oil well cement particles, reducing the contact area between the cement particles and free water, hindering the migration of ions in the pore solution inside the cement mortar, filling the gaps in the cement molecules, improving the pore structure of the cement, and improving the axial compressive strength and toughness of the oil well cement after solidification, reducing the probability of cement cracking, which is beneficial to extending the service life of the cementing cement.

[0064] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-density oil well cement slurry without floating beads, characterized in that: The components of the well cement slurry include the following raw materials by weight percentage: 35-45% of oil well cement, 15-25% of organic polymer emulsion, 1-3% of fluid loss reducer, 2-4% of modified nitrile rubber particles, 0.1-0.2% of dispersant, 0.1-0.2% of thickener, 0.1-0.2% of defoamer, and the balance is water.

2. The low-density oil well cement slurry without floating beads according to claim 1, characterized in that: The components of the well cement slurry include the following raw materials by weight percentage: 40% oil well cement, 20% organic polymer emulsion, 2% fluid loss reducer, 3% modified nitrile rubber particles, 0.15% dispersant, 0.15% thickener, 0.15% defoamer, and the balance is water.

3. The low-density oil well cement slurry without floating beads according to claim 2, characterized in that: The preparation method of the modified nitrile rubber particles is as follows: taking nitrile rubber particles, evenly spreading them in a glass container, putting them in a low-temperature plasma surface treatment instrument, starting a power supply and a vacuum pump, adjusting the cavity pressure to 10Pa, opening a flow valve to allow air to pass, and when the current flow rate is consistent with the set flow rate, turning on a high-frequency power supply for discharge treatment for 3 minutes, and turning off the high-frequency power supply, the flow valve and the vacuum pump to obtain modified nitrile rubber particles.

4. The low-density oil well cement slurry without floating beads according to claim 3, characterized in that: The composition of the well cement slurry includes the following raw materials in parts by weight: 2% polypropylene fiber.

5. The low-density oil well cement slurry without floating beads according to claim 4, characterized in that: The preparation method of low-density oil well cement slurry without floating beads is as follows: mix the fluid loss reducer, organic polymer emulsion and water evenly, stir them for 20 seconds under slow stirring conditions using a cement slurry mixer, add oil well cement, polypropylene fiber, modified nitrile rubber particles, dispersant, thickener and defoamer while stirring, then stir at high speed for 40 seconds, pour the stirred cement slurry into a cubic mold, and then put the mold into the condition of 70℃-75℃ for curing for 2 days to obtain the obtained product.

6. The low-density oil well cement slurry without floating beads according to claim 5, characterized in that: The slow stirring speed is 3500r / min.

7. The low-density oil well cement slurry without floating beads according to claim 5, characterized in that: The speed of high-speed stirring is 12000r / min.

8. The low-density oil well cement slurry without floating beads according to claim 5, characterized in that: The organic polymer emulsion is at least one of epoxy resin emulsion, phenolic resin emulsion or polyurethane resin emulsion.

9. The low-density oil well cement slurry without floating beads according to claim 8, characterized in that: The solid content of the organic polymer emulsion is 60%.

10. The low-density oil well cement slurry without floating beads according to claim 8, characterized in that: The fluid loss additive is at least one of polyvinyl alcohol or PC-G80L.

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