A multi-hydroxyl high-temperature resistant water-blocking agent for gas reservoirs and its preparation method

Abstract

The present invention provides a polyhydroxy high-temperature resistant water blocking agent for gas reservoirs and a preparation method thereof. The polyhydroxy high-temperature resistant water blocking agent of the present invention uses diethanolamine and epichlorohydrin as raw materials to prepare an intermediate T0, and then uses dodecyl dimethyl tertiary amine and intermediate T0 to prepare the polyhydroxy high-temperature resistant water blocking agent D12. The polyhydroxy high-temperature resistant water blocking agent provided by the present invention has 3 hydroxyl groups and 1 amino group in the hydrophilic group. The numerous hydrophilic groups endow the water blocking agent provided by the present invention with excellent high-temperature resistance performance. Thus, the polyhydroxy high-temperature resistant water blocking agent provided by the present invention has excellent surface tension reduction performance and rock wettability change performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and relates to a gas layer protection agent and a preparation method thereof, in particular to a multi-hydroxyl high-temperature resistant water-blocking agent for gas reservoirs and a preparation method thereof. Background Art

[0002] During the processes of drilling, well completion, and fracturing production operations, the phenomenon of water phase retention of external fluids in the porous media of formation rocks will occur. Especially in low-permeability gas reservoirs, low-permeability reservoirs usually have characteristics such as high capillary pressure, fine pore throats, strong hydrophilicity of rocks, low initial water saturation, and high gas flow resistance, and are prone to water-blocking effects and gas layer damage. Water-blocking damage is caused by the invasion of external fluids into the reservoir. Due to the too low initial water saturation in the reservoir, after the pores absorb water, the capillary force is too large, resulting in difficulty in the reverse drainage of water and natural gas in the pores, and reducing the oil-phase permeability. Research shows that water-blocking damage is the main damage form of low-permeability reservoirs, and the damage rate is generally 70%-90%.

[0003] Most of the reservoir rocks in low-permeability gas reservoirs are strongly hydrophilic. After external fluids enter the reservoir, the self-imbibition effect of water will occur, sucking the water in the working fluid near the wellbore into the rock pores, pushing the reservoir natural gas deep into the pores, and forming a capillary force pointing deep into the pores at the gas-water meniscus, resulting in difficulty in the reverse drainage of natural gas and water, reducing the relative permeability of oil and gas, and ultimately leading to a decrease in oil and gas recovery rate.

[0004] Therefore, only by developing a suitable water-blocking agent for low-permeability gas reservoirs can the productivity of gas wells in low-permeability gas reservoirs be effectively improved. The water-blocking agent is usually a surfactant. The principle is that after the surfactant molecules enter the reservoir, the surfactant molecules are adsorbed on the surface of the rocks in the low-permeability gas reservoir through adsorption, forming a molecular film, in which the hydrophobic chains point to the water phase, changing the hydrophilic rock surface into weakly hydrophilic, changing the wettability of the reservoir rocks, and due to the high surface activity characteristics of the surfactant, reducing the surface tension at the gas-water interface, thereby reducing the capillary force and reducing the degree of water-blocking damage. Summary of the Invention

[0005] The present invention provides a multi-hydroxyl high-temperature resistant water-blocking agent and a preparation method thereof in view of the disadvantages of the existing water-blocking agents such as high surface tension and poor temperature resistance. This water-blocking agent has a wide range of raw material sources, a simple synthesis process, low cost, and can effectively reduce the surface tension and increase the contact angle with very little dosage. The surface tension reaches below 21 mN / m and the contact angle reaches 87° at a concentration of 0.35 wt%.

[0006] In order to achieve the above invention, the technical solution adopted by the present invention is as follows:

[0007] A multi-hydroxyl high-temperature resistant water-blocking agent, and its specific structural formula is as follows:

[0008]

[0009] Among them, the specific preparation process reaction formula is as follows:

[0010] (1) Intermediate T0 synthesis reaction:

[0011]

[0012] (2) Surfactant D12 synthesis reaction:

[0013]

[0014] In the formula: R is a saturated hydrocarbon chain of CnH2n+1, where n = 12.

[0015] The specific preparation method of the polyhydroxy high-temperature resistant waterproof locking agent D12 includes the following steps:

[0016] (1) Add diethanolamine dissolved in ethanol (ethanol as the solvent) to a single-necked flask, stir for 10 minutes, slowly drop epichlorohydrin at a molar ratio of 1:1 to 1.3. After the dropping is completed, transfer it to an oil bath, connect a condenser reflux device, and stir and react at 40-70°C for 4-12 hours. After the reaction is completed, filter, remove impurities, perform low-temperature rotary evaporation, and vacuum dry to obtain a transparent paste-like product, which is intermediate T0;

[0017] (2) Dissolve the intermediate T0 obtained in step (1) and dodecyl dimethyl tertiary amine in a single-necked flask equipped with ethanol solvent at a molar ratio of 1:1.1 to 1.4, and place it in an oil bath at 80-90°C for condenser reflux stirring reaction for 12-24 hours. Then use a rotary evaporator to remove the solvent, and then perform recrystallization with acetone and vacuum dry to obtain a pale yellow paste-like product, which is the polyhydroxy high-temperature resistant waterproof locking agent D12.

[0018] Furthermore, the ethanol in step (1) can be isopropanol.

[0019] Furthermore, in a preferred embodiment of the present invention, in step (1), the reaction temperature is 40-60°C and the reaction time is 8-12h.

[0020] Furthermore, in a preferred embodiment of the present invention, in step (1), the reaction temperature is 50°C and the reaction time is 12h.

[0021] Furthermore, the dodecyl dimethyl tertiary amine in step (2) can be any one of tetradecyl dimethyl tertiary amine, hexadecyl dimethyl tertiary amine, and octadecyl dimethyl tertiary amine.

[0022] Further, in a preferred embodiment of the present invention, in step (2), the reaction temperature is 70 - 80 °C, and the reaction time is 12 - 18 h.

[0023] Further, in a preferred embodiment of the present invention, in step (2), the reaction temperature is 80 °C, and the reaction time is 16 h.

[0024] Further, in a preferred embodiment of the present invention, the above preparation method further includes a purification step: dissolving the crude product with acetone at 40 - 50 °C, and then recrystallizing the acetone solution at 0 - 5 °C to remove the unreacted dodecyl dimethyl tertiary amine, obtaining a crystalline product; treating the crystalline product by rotary evaporation to remove acetone, thereby preparing the polyhydroxy high-temperature resistant waterproofing agent.

[0025] The present invention has the following beneficial effects:

[0026] (1) The preparation process of the polyhydroxy high-temperature resistant waterproofing agent of the present invention is simple, raw materials are easily obtained, and all substances in the reaction process belong to the product without any by-products.

[0027] (2) The surface tension of the polyhydroxy high-temperature resistant waterproofing agent of the present invention is relatively low, and the surface tension at a concentration of 0.35 wt% reaches below 21 mN / m.

[0028] (3) The surface contact angle of the quartz sheet treated with the polyhydroxy high-temperature resistant waterproofing agent of the present invention reaches 66 - 87°. Description of the Drawings

[0029] Figure 1 It is a test result diagram of the surface tension of the polyhydroxy high-temperature resistant waterproofing agent at different concentrations.

[0030] Figure 2 It is a nuclear magnetic resonance hydrogen spectrum diagram of the polyhydroxy high-temperature resistant waterproofing agent D12.

[0031] Figure 3 It is a test result diagram of the contact angle of the quartz sheet treated with 0.35 wt% polyhydroxy high-temperature resistant waterproofing agent.

[0032] Figure 4 It is a test result diagram of the contact angle of the quartz sheet treated with 0.3 wt% polyhydroxy high-temperature resistant waterproofing agent.

[0033] Figure 5 It is a test result diagram of the contact angle of the quartz sheet treated with 0.25 wt% polyhydroxy high-temperature resistant waterproofing agent.

[0034] Figure 6 It is a test result diagram of the contact angle of the quartz sheet treated with 0.2 wt% polyhydroxy high-temperature resistant waterproofing agent. Specific Embodiment

[0035] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, the operations are carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments not indicated by the manufacturer can be obtained as conventional products through commercial purchase.

[0036] Example 1:

[0037] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0038] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1. Under magnetic stirring, the reaction temperature was raised to 40 °C, and the reaction was stirred at a constant temperature for 4 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate. An equimolar amount of dodecyldimethyl tertiary amine relative to epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. An appropriate amount of ethanol solvent was added to ensure that the dodecyldimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-neck flask. Under magnetic stirring, the temperature was slowly raised to 80 °C, and the reaction was stirred at a constant temperature for 12 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-1 with a yield of 86.5%.

[0039] Example 2:

[0040] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0041] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1.1. Under magnetic stirring, the reaction temperature was raised to 50 °C, and the reaction was stirred at a constant temperature for 5 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate. An equimolar amount of dodecyldimethyl tertiary amine relative to epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. An appropriate amount of ethanol solvent was added to ensure that the dodecyldimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-neck flask. Under magnetic stirring, the temperature was slowly raised to 85 °C, and the reaction was stirred at a constant temperature for 14 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-2 with a yield of 88.5%.

[0042] Example 3:

[0043] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0044] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1.2. Under magnetic stirring, the reaction temperature was raised to 60 °C, and the reaction was stirred at a constant temperature for 6 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate; An equimolar amount of dodecyl dimethyl tertiary amine as that of epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. The ethanol solvent was appropriately supplemented to ensure that the dodecyl dimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-necked flask. Under magnetic stirring, the temperature was slowly raised to 90 °C, and the reaction was stirred at a constant temperature for 16 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-3 with a yield of 89.5%.

[0045] Example 4:

[0046] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0047] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1.3. Under magnetic stirring, the reaction temperature was raised to 60 °C, and the reaction was stirred at a constant temperature for 8 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate; An equimolar amount of dodecyl dimethyl tertiary amine as that of epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. The ethanol solvent was appropriately supplemented to ensure that the dodecyl dimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-necked flask. Under magnetic stirring, the temperature was slowly raised to 90 °C, and the reaction was stirred at a constant temperature for 18 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-4 with a yield of 90.5%.

[0048] Example 5:

[0049] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0050] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1.4. Under magnetic stirring, the reaction temperature was raised to 60 °C, and the reaction was stirred at a constant temperature for 10 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate; an equimolar amount of dodecyl dimethyl tertiary amine as that of epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. An appropriate amount of ethanol solvent was added to ensure that the dodecyl dimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-necked flask. Under magnetic stirring, the temperature was slowly raised to 90 °C, and the reaction was stirred at a constant temperature for 20 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-5 with a yield of 91.2%.

[0051] Example 6:

[0052] The preparation method of the polyhydroxy high-temperature resistant waterproof locking agent in this example includes:

[0053] Diethanolamine and epichlorohydrin were successively added to an ethanol solution in a molar ratio of 1:1.4. Under magnetic stirring, the reaction temperature was raised to 50 °C, and the reaction was stirred at a constant temperature for 12 h. After cooling to room temperature, an ethanol solution of intermediate TO was obtained. The solvent was removed using a rotary evaporator to obtain the TO intermediate; an equimolar amount of dodecyl dimethyl tertiary amine as that of epichlorohydrin was weighed and added to the ethanol solution of intermediate TO. An appropriate amount of ethanol solvent was added to ensure that the dodecyl dimethyl tertiary amine could be completely dissolved and the solution did not exceed two-thirds of the volume of the single-necked flask. Under magnetic stirring, the temperature was slowly raised to 80 °C, and the reaction was stirred at a constant temperature for 16 h and then cooled to room temperature. The solvent was removed using a rotary evaporator, and then recrystallization was carried out using acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent D12-6 with a yield of 93.5%.

[0054] Example 7:

[0055] This example is a test on the high-temperature resistance performance of the polyhydroxy high-temperature resistant waterproof locking agent, and the test content is as follows:

[0056] The polyhydroxy high-temperature resistant waterproof locking agent D12-6 prepared in Example 6 was respectively filled in a closed container with 0.3 wt% and 0.35 wt% aqueous solutions, and aged at 120 °C for 24 h in a constant-temperature electric heating oven. After aging, the surface tension change was tested according to SY / T5370-2018 "Test Method for Surface and Interfacial Tension". The results are shown in Table 1. It can be seen from the results that at a lower concentration, the aged polyhydroxy high-temperature resistant waterproof locking agent still has high surface activity, and the surface tension is 21.4 mN / m at 0.35 wt%.

[0057] Example 8:

[0058] This example is for the contact angle performance test of the polyhydroxy high-temperature resistant waterproof locking agent, and the test content is as follows:

[0059] The polyhydroxy high-temperature resistant waterproof locking agent D12-6 prepared in Example 6 was dissolved in an aqueous solution at 0.2 wt%, 0.25 wt%, 0.3 wt%, and 0.35 wt% respectively. A quartz wafer was immersed in the solution for 24 h and then taken out and dried. After the treatment, the contact angle between the quartz wafer and clear water was measured. After testing, the contact angle of the 0.2 wt% aqueous solution was 66.375°, the contact angle of the 0.25 wt% aqueous solution was 72.006°, the contact angle of the 0.3 wt% aqueous solution was 82.172°, and the contact angle of the 0.35 wt% aqueous solution was 87.853°

[0060] Table 1 Test results after aging

[0061]

Claims

1. A multi-hydroxy high-temperature resistant water-blocking agent for gas reservoirs, characterized in that It has the following structural formula:

2. The synthesis method of a polyhydroxy high-temperature resistant water blocking agent for gas reservoirs according to claim 1, characterized in that, The polyhydroxy high-temperature resistant waterproof locking agent is prepared from diethanolamine, epichlorohydrin, and dodecyl dimethyl tertiary amine as raw materials.

3. The synthesis method of a polyhydroxy high-temperature resistant water blocking agent for gas reservoirs according to claim 2, characterized in that, It includes: (1) Diethanolamine and epichlorohydrin are sequentially added to an ethanol solution according to a molar ratio of 1:

1. Under magnetic stirring, the reaction temperature is raised to 40 - 70 °C, and the reaction is stirred at a constant temperature for 4 - 12 h. After filtration, impurity removal, low-temperature rotary evaporation, and vacuum drying, a transparent paste intermediate T0 is obtained. The intermediate structure has the following structural characteristics: (2) The intermediate T0 obtained from the reaction and dodecyl dimethyl tertiary amine are dissolved in a single-necked flask containing an ethanol solvent according to a molar ratio of 1:1, and placed in an oil bath pot at 80 - 90 °C for reflux stirring reaction for 12 - 24 hours. Then, the solvent is removed using a rotary evaporator, and then recrystallized with acetone to finally obtain the polyhydroxy high-temperature resistant waterproof locking agent described in claim 1.

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