Preparation method and application of dual-repellent temporary plugging agent

Abstract

The present invention proposes a preparation method and application of a dual-repellent temporary plugging agent. The dual-repellent temporary plugging agent uses grafted modified nano-calcium carbonate to change the surface properties of rocks to achieve the purpose of hydrophobicity and oleophobicity, while simultaneously reducing the surface tension of the filtrate to the greatest extent, preventing damage caused by transient filtration loss. In addition, the nano-sized dual-repellent temporary plugging agent can penetrate near the wellbore wall to form a dense plugging layer, reducing the invasion of filtrate into the formation during drilling, thereby protecting low-permeability oil and gas layers.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and in particular to a preparation method and application of a dual-repellent temporary plugging agent. Background Art

[0002] The type and performance of drilling fluid are directly related to the degree of damage to the oil and gas layer. Therefore, the drilling fluid technology for protecting the oil and gas layer is the primary technical link in doing a good job in protecting the oil and gas layer.

[0003] During the drilling process of low and ultra-low permeability oil and gas reservoirs, due to the low permeability of the formation and the small pore throats, the damage caused by solid particles is generally relatively small, while the damage caused by water sensitivity, water lock, and Jiamin is as high as 70% to 90% or more. These damages almost always occur during instantaneous filtration, that is, before the formation of high-quality "inner and outer filter cakes", which seriously affects the production of oil and gas wells. It can be seen that for low and ultra-low permeability oil and gas reservoirs, the most ideal oil and gas layer protection is to change the surface properties of the rock to make it hydrophobic and oleophobic before the mud cake forms, slowing the entry of drilling fluid filtrate into the formation pores, while reducing the surface tension of the drilling fluid filtrate and alleviating water lock and other damages; the mud cake formed has a dense sealing layer, which reduces the intrusion of filtrate into the formation during drilling.

[0004] Currently, in order to prevent damage caused by transient filtration and protect low-permeability oil and gas formations, various temporary plugging agents have emerged, including water-soluble temporary plugging agents, acid-soluble temporary plugging agents, alkali-soluble temporary plugging agents and oil-soluble temporary plugging agents, all of which have been widely developed and applied. However, these conventional temporary plugging agents do not take into account the impact of drilling fluid on the surface properties of the rock, resulting in large transient filtration and serious reservoir damage. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, the present invention proposes a method for preparing and applying a dual-repellent temporary plugging agent. The purpose of the present invention is to overcome the shortcomings of conventional temporary plugging agents and provide a method for preparing and applying a dual-repellent temporary plugging agent for drilling fluid suitable for reservoir protection. The dual-repellent temporary plugging agent can modify the surface properties of the rock to achieve both hydrophobicity and oleophobicity, while minimizing the surface tension of the filtrate and preventing damage caused by transient filtration loss. Furthermore, the nano-sized dual-repellent temporary plugging agent can penetrate near the wellbore wall to form a dense plugging layer, reducing the intrusion of filtrate into the formation during drilling, thereby protecting low-permeability oil and gas layers.

[0006] In a first aspect, the present invention provides a method for preparing a dual-repellent temporary plugging agent, comprising the following steps:

[0007] S1: in a solvent, allowing nano-calcium carbonate and a fluorine-containing silane coupling agent to undergo a first contact reaction to obtain modified nano-calcium carbonate;

[0008] S2: Under the action of an initiator, the solution containing the fluorine-containing acrylate monomer and N-vinyl pyrrolidone is subjected to a second contact reaction with the modified nano-calcium carbonate obtained in step S1.

[0009] As a specific embodiment of the present invention, in step S1, the solvent is ethanol or an ethanol aqueous solution. The volume ratio of ethanol to water in the ethanol aqueous solution is 1:(5-7).

[0010] As a specific embodiment of the present invention, in step S1, the solvent is ethanol or ethanol aqueous solution; the particle size of the nano-calcium carbonate is 10-40 nm; and the volume mass ratio of the solvent to the nano-calcium carbonate is 100 ml: (3-5) g.

[0011] As a specific embodiment of the present invention, in step S1, the fluorine-containing silane coupling agent is one of (3,3,3-trifluoropropyl)trimethoxysilane, trifluoropropyltriethoxysilane and perfluorohexyltriethoxysilane.

[0012] As a specific embodiment of the present invention, in step S1, the mass ratio of nano-calcium carbonate to fluorine-containing silane coupling agent in the first contact reaction is 1:(0.5-0.8).

[0013] As a specific embodiment of the present invention, in step S1, the conditions for the first contact reaction are: a stirring rate of 800 to 1200 rpm / min, a temperature of 60 to 80°C, and a time of 2 to 4 hours. Specifically, the nano-calcium carbonate and the fluorine-containing silane coupling agent can be ultrasonically dispersed for 20 to 40 minutes before the first contact reaction.

[0014] As a specific embodiment of the present invention, in step S2, the fluorine-containing acrylate monomer is trifluoroethyl methacrylate or hexafluorobutyl methacrylate; the mass ratio of the modified nano-calcium carbonate to the fluorine-containing acrylate monomer and N-vinyl pyrrolidone is 1:(0.3-0.5):(0.1-0.3).

[0015] As a specific embodiment of the present invention, in step S2, the dissolving includes dissolving with an emulsifier; the emulsifier is preferably sodium dodecylbenzenesulfonate; and the amount of the emulsifier is 0.1 to 0.2 of the total amount of the monomers used.

[0016] Specifically, sodium dodecylbenzenesulfonate is used as an emulsifier in the form of an emulsifier aqueous solution, wherein the mass ratio of the emulsifier to water is 1:(20-30).

[0017] As a specific embodiment of the present invention, in step S2, the initiator is potassium persulfate, and the amount of the initiator used accounts for 0.02 to 0.04 of the total amount of the monomers used.

[0018] As a specific embodiment of the present invention, in step S2, the conditions for the second contact reaction are: stirring speed of 1200-1800 rpm / min, temperature of 75-85° C., and time of 2-5 h.

[0019] As a specific embodiment of the present invention, the dual-repellent temporary plugging agent can change the surface properties of the rock to achieve the purpose of hydrophobicity and oleophobicity, while minimizing the surface tension of the filtrate and preventing damage caused by transient filtration loss. In addition, the nano-sized dual-repellent temporary plugging agent can penetrate near the wellbore wall to form a dense plugging layer, reducing the intrusion of filtrate into the formation during drilling, thereby protecting the low-permeability oil and gas layer.

[0020] In a second aspect, the present invention provides an application of the dual-repellent temporary plugging agent in the field of drilling fluid.

[0021] As a specific embodiment of the present invention, the mass fraction of the dual-repellent temporary plugging agent in the drilling fluid is 1% to 2%.

[0022] The above raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The dual-repellent nanometer temporary plugging agent for drilling fluid of the present invention can change the surface wettability of the well wall rock by introducing a large number of fluorine atoms, making it hydrophobic and oleophobic, thereby reducing the damage caused by transient filtration loss.

[0025] 2. It can be seen from the embodiments of the present invention that under the action of positive pressure difference, the nano-sized dual-repellent temporary plugging agent for drilling fluid can enter the pore throat of the well wall, improve the strength of the plugging layer, and protect the low-permeability oil and gas layer.

[0026] 3. Compared with conventional temporary plugging agents, the present invention has the characteristics of less dosage and less impact on the environment, and has the effects of acid hydrolysis and environmental microbial degradation. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific examples, but they do not constitute any limitation to the present invention.

[0028] In the various embodiments of the present invention, the reagents used are common reagents in the chemical field, and the present invention does not specifically limit or describe them.

[0029] Example 1

[0030] This embodiment provides a dual-repellent temporary plugging agent and a preparation method thereof, the specific details of which are as follows:

[0031] S1: In a four-necked flask, add 100 mL of a mixed solution (ethanol / water volume ratio of 1:5), add 3 g of nano-calcium carbonate (particle size of 10 nm), and after ultrasonic dispersion for 30 min, add 1.5 g of (3,3,3-trifluoropropyl)trimethoxysilane, stir and mix at 800 rpm / min, heat the water bath to 60 ° C, and react for 2 h to obtain modified nano-calcium carbonate.

[0032] S2: Add 0.12g of sodium dodecyl sulfate and 2.4g of deionized water to a beaker to prepare a sodium dodecyl sulfate aqueous solution. Dissolve 0.9g of trifluoroethyl methacrylate and 0.3g of N-vinyl pyrrolidone in the sodium dodecyl sulfate aqueous solution to obtain a mixed solution. Add the mixed solution to the above four-necked flask and stir at 1200rpm / min. Add 0.036g of potassium persulfate and heat to 75°C in a water bath. Let the mixture react for 3h. The resulting product is a dual-repellent temporary plugging agent.

[0033] Example 2

[0034] This embodiment provides a dual-repellent temporary plugging agent and a preparation method thereof, the specific details of which are as follows:

[0035] S1: In a four-necked flask, add 100 mL of a mixed solution (ethanol / water volume ratio of 1:5), add 3 g of nano-calcium carbonate (particle size of 30 nm), and after ultrasonic dispersion for 30 min, add 1.8 g of trifluoropropyltriethoxysilane, stir and mix at 1000 rpm / min, heat the water bath to 70°C, and react for 3 h to obtain modified nano-calcium carbonate.

[0036] S2: Add 0.27g of sodium dodecylsulfonate and 12g of deionized water to a beaker to prepare a sodium dodecylsulfonate aqueous solution. Dissolve 1.2g of hexafluorobutyl methacrylate and 0.6g of N-vinylpyrrolidone in the sodium dodecylsulfonate aqueous solution to obtain a mixed solution. Add the mixed solution to the above four-necked flask and stir at 1500rpm / min. Add 0.072g of potassium persulfate and heat in a water bath to 80°C. Allow to react for 4h. The resulting product is a dual-repellent temporary plugging agent for drilling fluid.

[0037] Example 3

[0038] This embodiment provides a dual-repellent temporary plugging agent and a preparation method thereof, the specific details of which are as follows:

[0039] S1: In a four-necked flask, add 100 mL of a mixed solution (ethanol / water volume ratio of 1:5), add 3 g of nano-calcium carbonate (particle size of 40 nm), and after ultrasonic dispersion for 30 min, add 2.4 g of perfluorohexyltriethoxysilane, stir and mix at 1200 rpm / min, heat in a water bath to 80°C, and react for 4 h to obtain modified nano-calcium carbonate.

[0040] S2: Add 0.48g of sodium dodecyl sulfate and 24g of deionized water to a beaker to prepare a sodium dodecyl sulfate aqueous solution. Dissolve 1.5g of hexafluorobutyl methacrylate and 0.9g of N-vinyl pyrrolidone in the sodium dodecyl sulfate aqueous solution to obtain a mixed solution. Add the mixed solution to the above four-necked flask and stir at 1800 rpm. Add 0.096g of potassium persulfate and heat in a water bath to 85°C. Allow to react for 5 hours. The resulting product is a dual-repellent temporary plugging agent for drilling fluid.

[0041] Comparative Example 1

[0042] This comparative example provides a temporary plugging agent and a preparation method thereof. The difference from Example 1 is that the mass ratio of nano-calcium carbonate to fluorine-containing silane coupling agent is 1:1. The specific details are as follows:

[0043] S1: In a four-necked flask, add 100 mL of a mixed solution (ethanol / water volume ratio of 1:5), add 3 g of nano-calcium carbonate (particle size of 10 nm), and after ultrasonic dispersion for 30 min, add 3 g of (3,3,3-trifluoropropyl)trimethoxysilane, stir and mix at 800 rpm / min, heat the water bath to 60 ° C, and react for 2 h to obtain modified nano-calcium carbonate.

[0044] S2: Add 0.12g of sodium dodecyl sulfate and 2.4g of deionized water to a beaker to prepare a sodium dodecyl sulfate aqueous solution. Dissolve 0.9g of trifluoroethyl methacrylate and 0.3g of N-vinyl pyrrolidone in the sodium dodecyl sulfate aqueous solution to obtain a mixed solution. Add the mixed solution to the above four-necked flask and stir at 1200rpm / min. Add 0.036g of potassium persulfate and heat to 75°C in a water bath. Let the mixture react for 3h. The resulting product is a dual-repellent temporary plugging agent.

[0045] Comparative Example 2

[0046] This comparative example provides a temporary plugging agent and a preparation method thereof. The difference from Example 3 is that the mass ratio of calcium carbonate, trifluoroethyl methacrylate and N-vinyl pyrrolidone is 1:1:0.5. The specific details are as follows:

[0047] S1: In a four-necked flask, add 100 mL of a mixed solution (ethanol / water volume ratio of 1:5), add 3 g of nano-calcium carbonate (particle size of 40 nm), and after ultrasonic dispersion for 30 min, add 2.4 g of perfluorohexyltriethoxysilane, stir and mix at 1200 rpm / min, heat in a water bath to 80°C, and react for 4 h to obtain modified nano-calcium carbonate.

[0048] S2: Add 0.48g of sodium dodecylsulfonate and 24g of deionized water to a beaker to prepare a sodium dodecylsulfonate aqueous solution. Dissolve 3g of hexafluorobutyl methacrylate and 1.5g of N-vinylpyrrolidone in the sodium dodecylsulfonate aqueous solution to obtain a mixed solution. Add the mixed solution to the above four-necked flask and stir at 1800 rpm. Add 0.096g of potassium persulfate and heat in a water bath to 85°C. Allow to react for 5 hours. The resulting product is a dual-repellent temporary plugging agent for drilling fluids.

[0049] Test Example 1

[0050] Surface tension evaluation: Solutions of Examples 1-3 were prepared in water to form solutions of varying concentrations. The surface tension of the prepared plugging agents of varying concentrations was measured at 25°C using the platinum plate method (see the method described in GB / T18396-2001 for details). The results are shown in Table 1.

[0051] Table 1 Surface tension evaluation data of solutions with different concentrations prepared in water

[0052]

[0053] As can be seen from Table 1, the ambiphobic nano-ultrafine calcium carbonate plugging agent of the present invention has strong surface activity and can effectively reduce the surface tension of water. In particular, in Example 1 at a concentration of 0.3%, the surface tension of water can be reduced to below 12.7 mN / m. Comparative Examples 1-2 have poor ability to reduce surface tension.

[0054] Test Example 2

[0055] Evaluation of hydrophobicity and oleophobicity: 0.3% aqueous solution of Examples 1-3 was prepared respectively, and the artificial rock core was placed therein and soaked at 150°C for 8 hours. The rock core was taken out, cooled and dried, and then the contact angle θ of the oil phase and the water phase on the surface of the rock core was measured by a contact angle meter (model JC2000D3 contact angle meter of Shanghai Zhongchen Digital Technology Equipment Co., Ltd.). o and θ w The results are shown in Table 2, wherein the oil phase is n-hexadecane and the water phase is distilled water.

[0056] Table 2 Hydrophobicity and oleophobicity evaluation data of 0.3% aqueous solution

[0057]

[0058] It can be seen from the data in Table 2 that the temporary plugging agents prepared in Examples 1-3 can make the rock surface have strong hydrophobicity and oleophobicity, achieving a double surface hydrophobicity effect, while the hydrophobicity and oleophobicity effects of Comparative Examples 1-2 are not ideal.

[0059] Test Case

[0060] In this test example, the temporary plugging performance of the dual-repellent temporary plugging agents prepared in Examples 1-3 and Comparative Examples 1-2 was evaluated. The specific details are as follows:

[0061] 2% of the temporary plugging agents prepared in Examples 1-3 and Comparative Examples 1-2 were added to 4% bentonite-based slurry, and the temporary plugging performance of the temporary plugging agents in Examples 1-3 and Comparative Examples in the drilling fluid-based slurry was evaluated using a medium-pressure filter loss meter and a visual sand bed device. The results are shown in Table 3:

[0062] Table 3 Temporary plugging performance evaluation results

[0063]

[0064] From the data in Table 3, it can be seen that the temporary plugging agents of Examples 1-3 have good plugging performance and can effectively plug the filter paper and sand, reduce filtration loss, and reduce the penetration depth of the filtrate.

[0065] In summary, the dual-repellent temporary plugging agent of the present invention can change the surface properties of rocks to achieve the purpose of water repellency and oil repellency, while also minimizing the surface tension of the filtrate and preventing damage caused by transient filtration loss. Moreover, the nano-sized dual-repellent temporary plugging agent can penetrate near the wellbore wall to form a dense plugging layer, reducing the intrusion of filtrate into the formation during drilling, thereby protecting low-permeability oil and gas layers.

[0066] Any numerical value mentioned in the present invention includes all values ​​that increase by one unit each time from the lowest value to the highest value if there is only a gap of two units between any minimum value and any maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, time, etc. is stated to be 50-90, it is meant in this specification to specifically list values ​​such as 51-89, 52-88... and 69-71 and 70-71. For non-integer values, it is appropriate to consider units of 0.1, 0.01, 0.001 or 0.0001. These are just some special examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed lowest value and the listed highest value are considered to have been disclosed.

[0067] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a dual-repellent temporary plugging agent, characterized in that: The following steps are involved: S1: in a solvent, allowing nano-calcium carbonate and a fluorine-containing silane coupling agent to undergo a first contact reaction to obtain modified nano-calcium carbonate; S2: Under the action of an initiator, the solution containing the fluorine-containing acrylate monomer and N-vinyl pyrrolidone is subjected to a second contact reaction with the modified nano-calcium carbonate obtained in step S1; In the step S1, the mass ratio of the nano-calcium carbonate to the fluorine-containing silane coupling agent in the first contact reaction is 1:(0.5-0.8); In step S2, the fluorinated acrylic ester monomer is trifluoroethyl methacrylate or hexafluorobutyl methacrylate; In step S2, the mass ratio of modified nano-calcium carbonate to fluorine-containing acrylic ester monomer and N-vinyl pyrrolidone is 1:(0.3-0.5):(0.1-0.3).

2. The preparation method according to claim 1, characterized in that In step S1, the solvent is ethanol or an ethanol aqueous solution; and / or the particle size of the nano-calcium carbonate is 10-40 nm; and / or the volume mass ratio of the solvent to the nano-calcium carbonate is 100 ml: (3-5) g.

3. The preparation method according to claim 1, characterized in that In the step S1, the fluorine-containing silane coupling agent is one of (3,3,3-trifluoropropyl)trimethoxysilane, (3,3,3-trifluoropropyl)triethoxysilane and perfluorohexyltriethoxysilane.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step S1, the conditions for the first contact reaction include: a stirring rate of 800 to 1200 rpm / min, a temperature of 60 to 80° C., and a time of 2 to 4 hours.

5. The preparation method according to any one of claims 1 to 3, characterized in that In the step S2, the solution contains an emulsifier.

6. The preparation method according to claim 5, characterized in that The emulsifier is sodium dodecylbenzenesulfonate, and / or the amount of the emulsifier is 0.1 to 0.2 of the total mass of the monomers used.

7. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the initiator is potassium persulfate, and the amount of the initiator used accounts for 0.02 to 0.04 of the total mass of the monomers used.

8. The preparation method according to any one of claims 1 to 3, characterized in that In step S2, the conditions for the second contact reaction include: a stirring speed of 1200-1800 rpm / min, a temperature of 75-85° C., and a time of 2-5 hours.

9. Use of the dual-repellent temporary plugging agent prepared by the preparation method according to any one of claims 1 to 8 in the field of drilling fluids.

10. The use according to claim 9, characterized in that The mass fraction of the dual-repellent temporary plugging agent in the drilling fluid is 1% to 2%.

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