High-temperature-resistant filtrate reducer, preparation method and application thereof, and drilling fluid

Abstract

The invention provides a preparation method and application of a high-temperature-resistant filtrate reducer and a drilling fluid, and the preparation method comprises the following steps: mixing water, acrylamide, N, N-dimethylacrylamide, vinyl acetate and sodium carbonate, adding an initiator, and carrying out a copolymerization reaction to obtain the high-temperature-resistant filtrate reducer. Water, acrylamide, N, N-dimethylacrylamide, vinyl acetate and sodium carbonate are adopted as raw materials, a main chain of the prepared high-temperature-resistant filtrate reducer is a carbon-carbon main chain, a side chain group contains a cyclic structure, and groups on a molecular side chain of the high-temperature-resistant filtrate reducer are two adsorption groups and one hydration group. Due to the adsorption groups, filtrate reducer molecules have a very good filtrate reduction effect; the hydrated group enables the water solubility of filtrate reducer molecules to become better, and especially enables the filtrate reducer molecules to be well dissolved in a high-concentration organic salt solution.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield drilling fluid materials, and in particular to a high-temperature resistant fluid loss reducer, a preparation method and application thereof, and drilling fluid. Background Art

[0002] With the continuous advancement of oil and gas exploration and development, drilling operations are gradually extending to complex reservoirs such as deep formations, shale gas, and high-temperature geothermal reservoirs. Downhole temperatures generally exceed 200°C, and even reach over 250°C. This high-temperature environment poses severe challenges to drilling fluid performance. Fluid loss control is one of the core technical challenges in ensuring wellbore stability and preventing formation damage.

[0003] Traditional fluid loss additives (such as sulfonated asphalt, carboxymethyl cellulose, etc.) have obvious defects under high temperature conditions: Insufficient thermal stability: Conventional polymers are prone to molecular chain breakage and group decomposition (such as desulfurization of sulfonic acid groups) above 150°C, resulting in a sharp decline in fluid loss reduction performance.

[0004] Weak salt resistance: High temperature exacerbates the damage of high-valent metal ions to the cross-linked structure of the polymer, causing uncontrolled filtration loss.

[0005] Poor synergistic effect: Under high temperature, the compatibility of traditional treatment agents with other components of drilling fluid (such as clay and plugging agents) deteriorates, and the filter cake formed is loose and porous, resulting in poor fluid loss reduction effect.

[0006] While some existing high-temperature fluid loss additives (such as sulfonated phenolic resins and zwitterionic polymers) can withstand temperatures between 180°C and 200°C, their synthesis processes are complex, rely on toxic cross-linking agents like formaldehyde, and are relatively expensive. Furthermore, at extremely high temperatures (>220°C), existing products still suffer from sudden increases in fluid loss and deterioration in rheological properties, leading to the risk of wellbore instability.

[0007] Therefore, the development of a fluid loss reducer that is both high-temperature stable, environmentally friendly and economical is of great significance for the safe and efficient construction of deep wells, ultra-deep wells and geothermal drilling. Summary of the Invention

[0008] In view of the various deficiencies of the existing technology and in order to solve the above problems, a high-temperature resistant fluid loss reducer, a preparation method and application thereof, and a drilling fluid are proposed, and the following technical solutions are provided: A method for preparing a high-temperature resistant fluid loss reducer comprises the following steps: mixing water, acrylamide, N,N-dimethylacrylamide, vinyl acetate and a pH regulator for adjusting the pH value to alkaline, adding an initiator and causing copolymerization reaction to obtain the high-temperature resistant fluid loss reducer.

[0009] Furthermore, calculated by weight, the water is 100 parts, acrylamide is 8-12 parts, N,N-dimethylacrylamide is 4-6 parts, vinyl acetate is 1-2 parts, pH regulator is 2-7 parts, and initiator is 1-5 parts.

[0010] Furthermore, calculated by weight, the water is 100 parts, acrylamide is 11 parts, N,N-dimethylacrylamide is 6 parts, vinyl acetate is 2 parts, pH regulator is 4 parts, and initiator is 4 parts.

[0011] Furthermore, calculated by weight, the water is 100 parts, acrylamide is 10 parts, N,N-dimethylacrylamide is 5 parts, vinyl acetate is 1 part, pH regulator is 5 parts, and initiator is 2 parts.

[0012] Furthermore, the pH adjuster is soda ash.

[0013] Furthermore, the initiator is a potassium sulfate aqueous solution, and the concentration of the potassium sulfate aqueous solution is 10%.

[0014] In addition, the present invention also provides a high-temperature resistant fluid loss reducer, which is prepared by the above-mentioned preparation method.

[0015] The present invention also provides a use of the high-temperature resistant fluid loss reducer in preparing oilfield drilling fluid.

[0016] The present invention also provides a drilling fluid containing the above-mentioned high-temperature resistant fluid loss reducer.

[0017] Furthermore, the drilling fluid includes water, and the drilling fluid also includes water, and the added amount of the high-temperature resistant fluid loss reducer is water.

[0018] Beneficial effects: 1. The high temperature resistant fluid loss reducer of the present invention has good fluid loss reducing effect and strong temperature resistance, and can withstand high temperatures of 200°C and above.

[0019] 2. The main chain of the high-temperature resistant fluid loss reducer copolymer molecule is a carbon-carbon main chain, and the side chain group contains a ring structure, so it can resist higher temperatures. In addition, the groups on the side chain of the high-temperature resistant fluid loss reducer molecule are two adsorption groups and one hydration group. The adsorption groups make the fluid loss reducer molecule have a good fluid loss reduction effect; the hydration group improves the water solubility of the fluid loss reducer molecule, especially making the fluid loss reducer molecule well soluble in high-concentration organic salt solutions.

[0020] 3. The present invention explores the dosage ratio of each raw material to achieve a moderate ratio of adsorption groups and hydration groups in the high-temperature resistant fluid loss reducer polymer molecules, achieving excellent fluid loss reduction effect. The ratio of two adsorption groups to one hydration group is crucial. If there are too many hydration groups and too few adsorption groups, the fluid loss reducer will weakly bind to the clay, and most of the molecules will dissolve in water, unable to effectively adsorb to the clay, resulting in poor fluid loss reduction effect. If there are too many adsorption groups and too few hydration groups, the water solubility is poor, the fluid loss reducer will not dissolve well in water, and will not effectively reduce fluid loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a comparison chart of the effects of the high-temperature resistant fluid loss reducer prepared in Example 1 in Performance Test 3 of the present invention and other fluid loss reducers. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the embodiments of the present invention. Based on the embodiments in this application, other similar embodiments obtained by ordinary technicians in this field without making any creative work should fall within the scope of protection of this application.

[0023] According to an embodiment of the present invention, a method for preparing a high-temperature resistant fluid loss reducer is provided. The method comprises: mixing water, acrylamide, N,N-dimethylacrylamide, vinyl acetate, and soda ash, and then adding an initiator to cause a copolymerization reaction to obtain the high-temperature resistant fluid loss reducer. The present invention uses water, acrylamide, N,N-dimethylacrylamide, vinyl acetate, and soda ash as raw materials. The main chain of the high-temperature resistant fluid loss reducer prepared by the present invention is a carbon-carbon main chain, and the side chain groups contain a cyclic structure. In addition, the groups on the side chains of the high-temperature resistant fluid loss reducer molecules are two adsorption groups and one hydration group. The adsorption groups give the fluid loss reducer molecules a good fluid loss reduction effect; the hydration groups improve the water solubility of the fluid loss reducer molecules, especially allowing the fluid loss reducer molecules to be well soluble in high-concentration organic salt solutions.

[0024] Specifically, calculated by weight, the composition includes 100 parts water, 8-12 parts acrylamide, 4-6 parts N,N-dimethylacrylamide, 1-2 parts vinyl acetate, and 2-7 parts soda ash. The ratio of two adsorption groups to one hydration group is crucial. If there are too many hydration groups and too few adsorption groups, the fluid loss additive will weakly bind to the clay, with most molecules dissolving in water and unable to effectively adsorb to the clay, resulting in poor fluid loss reduction. If there are too many adsorption groups and too few hydration groups, the water solubility will be poor, and the fluid loss additive will not dissolve well in water and will not effectively reduce fluid loss. Within this ratio range, the ratio of adsorption groups to hydration groups in the high-temperature resistant fluid loss additive polymer molecules is moderate, resulting in excellent fluid loss reduction effectiveness.

[0025] Example 1 Place 100 parts water, 10 parts acrylamide, 5 parts N,N-dimethylacrylamide, 1 part vinyl acetate, and 5 parts soda ash in a mixing container by weight and stir thoroughly to dissolve. Heat to 45-55°C. Stop heating and add 2 parts of a 10% aqueous potassium sulfate solution as an initiator to initiate a polymerization reaction. Raise the system temperature to 80-100°C and maintain for 1 hour. Then, granulate the colloidal copolymer, dry it, and pulverize it to obtain a high-temperature resistant fluid loss reducer.

[0026] Example 2 Place 100 parts water, 8 parts acrylamide, 4 parts N,N-dimethylacrylamide, 1 part vinyl acetate, and 2 parts soda ash in a mixing container by weight and stir thoroughly to dissolve. Heat to 45-55°C. Stop heating and add 1 part initiator, a 10% aqueous potassium sulfate solution, to initiate a polymerization reaction. Raise the system temperature to 80-100°C and maintain for 1 hour. Then, granulate the colloidal copolymer, dry it, and pulverize it to obtain a high-temperature resistant fluid loss reducer.

[0027] Example 3 Place 100 parts water, 12 parts acrylamide, 6 parts N,N-dimethylacrylamide, 2 parts vinyl acetate, and 7 parts soda ash in a mixing container by weight and stir thoroughly to dissolve. Heat to 45-55°C. Stop heating and add 5 parts of a 10% aqueous potassium sulfate solution as an initiator to initiate a polymerization reaction. Raise the system temperature to 80-100°C and maintain for 2 hours. Then, granulate the colloidal copolymer, dry it, and pulverize it to obtain a high-temperature resistant fluid loss reducer.

[0028] Example 4 Place 100 parts water, 9 parts acrylamide, 6 parts N,N-dimethylacrylamide, 2 parts vinyl acetate, and 4 parts soda ash in a mixing container by weight and stir thoroughly to dissolve. Heat to 45-55°C. Stop heating and add 3 parts of a 10% aqueous potassium sulfate solution as an initiator to initiate a polymerization reaction. Raise the system temperature to 80-100°C and maintain this temperature for 1.5 hours. Then, granulate the colloidal copolymer, dry it, and pulverize it to obtain a high-temperature resistant fluid loss reducer.

[0029] Example 5 Place 100 parts water, 11 parts acrylamide, 5 parts N,N-dimethylacrylamide, 2 parts vinyl acetate, and 4 parts soda ash in a mixing container by weight and stir thoroughly to dissolve. Heat to 45-55°C. Stop heating and add 4 parts of a 10% aqueous potassium sulfate solution as an initiator to initiate a polymerization reaction. Raise the system temperature to 80-100°C and maintain for 2 hours. Then, granulate the colloidal copolymer, dry it, and pulverize it to obtain a high-temperature resistant fluid loss reducer.

[0030] Comparative Example 1 Compared with Example 1, vinyl acetate was not added, and other parts were the same as Example 1.

[0031] Comparative Example 2 Compared with Example 1, N,N-dimethylacrylamide was not added, and other parts were the same as Example 1.

[0032] Comparative Example 3 Compared with Example 1, the amount of acrylamide, N,N-dimethylacrylamide, and vinyl acetate is 5 parts, and the other parts are the same as those in Example 1.

[0033] Comparative Example 4 Compared with Example 1, the amount of acrylamide, N,N-dimethylacrylamide, and vinyl acetate is 15 parts, and the other parts are the same as those in Example 1.

[0034] Performance testing: The abbreviations in the present invention represent the following meanings: Visco1: Commercially available drilling fluid shear enhancer modified silicate Visco1; NFA-25: Commercially available drilling fluid inhibitor and anti-collapse agent, non-fluorescent white asphalt NFA-25; PGCS-1: Commercially available solid polyol PGCS-1 for drilling fluids; Weigh2: organic salt Weigh2 of water-soluble weighting inhibitor for commercial drilling fluid; Weigh3: Commercially available drilling fluid water-soluble weighting inhibitor organic salt Weigh3; AV: table viscosity; PV: plastic viscosity; FL API : Medium pressure filtration loss at room temperature; FL HTHP : High temperature and high pressure filtration loss, the test temperature is the corresponding hot rolling temperature, and the pressure is 3.5MPa.

[0035] 1. Test the filtration loss reduction effect of the high temperature resistant filtration reducer prepared in Examples 1-5 in different drilling fluids Freshwater sample slurry: 400mL fresh water + 1.2g NaHCO3 + 16g bentonite for drilling fluid test slurry + 16g evaluation soil for drilling fluid test + 12g high temperature resistant fluid loss reducer.

[0036] 4% brine sample slurry: 400mL fresh water + 1.2g NaHCO3 + 28g bentonite for drilling fluid test slurry + 28g evaluation soil for drilling fluid test + 16g high temperature resistant fluid loss reducer.

[0037] Saturated brine sample slurry: 400mL fresh water + 1.2g NaHCO3 + 28g bentonite for drilling fluid test slurry + 28g evaluation soil for drilling fluid test + 24g high temperature resistant fluid loss reducer.

[0038] Table 1 Performance of high temperature resistant fluid loss reducer after hot rolling at 180℃ in different drilling fluids The data in Table 1 demonstrates that the high-temperature-resistant fluid loss additives prepared in Examples 1-5 exhibit excellent fluid loss reduction performance in freshwater, 4% brine, and saturated brine drilling fluids. After hot rolling at 180°C, the API fluid loss was approximately 5 mL, and the HTHP fluid loss was approximately 20 mL, both meeting drilling operation requirements. In contrast, in the comparative examples, when the ratios of acrylamide, N,N-dimethylacrylamide, and vinyl acetate were outside the protection range, the fluid loss reduction performance was significantly reduced.

[0039] 2. Effect of reducing filtration loss in composite brine Base slurry: 400ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2; Sample slurry 1: 400 ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2 + 0.5% high temperature resistant fluid loss reducer prepared in Example 1; Sample slurry 2: 400 ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2 + 1.0% high temperature resistant fluid loss reducer prepared in Example 1; Sample slurry 3: 400 ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2 + 1.3% high temperature resistant fluid loss reducer prepared in Example 1; Sample slurry 4: 400 ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2 + 1.5% high temperature resistant fluid loss reducer prepared in Example 1; Sample slurry 5: 400 ml fresh water + 10% drilling fluid evaluation soil + 4.5% NaCl + 0.5% CaCl2 + 1.3% MgCl2 + 2.0% high temperature resistant fluid loss reducer prepared in Example 1; Hot rolling conditions: 180℃×16 h Table 2 Fluid loss reduction effect of different dosages of fluid loss reducer in composite brine As can be seen from the data in Table 2 above, the high-temperature and salt-resistant fluid loss additive not only has a good fluid loss reduction effect in sodium chloride brine, but also has a good fluid loss reduction effect in composite brine. Moreover, the fluid loss reduction effect gradually increases with the increase in the addition amount within 0.5-2%.

[0040] 3. Test the fluid loss effect with other fluid loss reducers Test method: Measure 400mL of water, add 0.3% Na2CO3 and 6% bentonite for drilling fluid test, stir at high speed for 20 minutes, then add 1%, 2%, and 3% of the high temperature resistant fluid loss reducer prepared in Example 1, SMP-Ⅱ, SPNH and SMC respectively, stir at high speed for 20 minutes, put into aging tank, roll aging at 180℃×16h, cool to room temperature, stir at high speed for 5min, and measure the water loss at room temperature (20℃~30℃) with a normal temperature medium pressure water loss meter. Specific test results are as follows Figure 1 and as shown in Table 3.

[0041] Base slurry loss after hot rolling: 27.2mL Table 3 Comparison of the fluid loss reduction effect of the high temperature resistant fluid loss reducer prepared in Example 1 and other fluid loss reducers From Table 3 and Figure 1 It can be seen that after rolling aging at 180°C for 16 h, the addition of 1% of the high-temperature resistant fluid loss reducer prepared in Example 1, SMP-Ⅱ, SPNH and SMC can reduce the fluid loss of the base slurry from 27.2 mL to 7.6 mL, 27 mL, 15 mL and 20 mL, respectively, with a decrease of 72%, 0.07%, 45% and 26%, respectively. This shows that the high-temperature resistant fluid loss reducer prepared in Example 1 has the best fluid loss reduction effect, while the other three fluid loss reducers have weak effects.

[0042] In addition, the present invention also provides an oilfield drilling fluid with a density of up to 2.0 g / cm 3 , and can withstand high temperatures of 220°C.

[0043] The drilling fluid formula is: 300mL water + 0.3%Na2CO3 + 0.2%NaOH + 2%Visco1 + 7%high temperature resistant fluid loss reducer + 0.5%NAT20 + 2%NFA-25 + 1%PGCS-1 + 50%Weigh2 + 30%Weigh3 + 180%barite.

[0044] Drilling fluid density: 2.0g / cm 3 Hot rolling temperature: 220℃ The test results are shown in Table 4.

[0045] Table 4 Application effects of high temperature resistant fluid loss reducers of different embodiments in oilfield drilling fluids The high-temperature resistant fluid loss reducers selected in ①-⑤ are those prepared in Examples 1-5, respectively. The data in Table 4 demonstrate that drilling fluid systems prepared using the high-temperature resistant fluid loss reducers and other drilling fluid treatment agents obtained in accordance with the present invention can withstand temperatures up to 220°C. Even after hot rolling for 24 hours, they maintain excellent performance, good rheological properties, and moderate fluid loss, meeting the construction requirements of high-temperature wells, such as deep and ultra-deep wells.

[0046] In addition, the high temperature resistant fluid loss reducer prepared in Example 1 was selected to prepare oilfield drilling fluid, and the addition amounts of the high temperature resistant fluid loss reducer were 1% and 10% of water, respectively.

[0047] Formula 1 is: 300mL water + 0.3%Na2CO3 + 0.2%NaOH + 2%Visco1 +1%high temperature resistant fluid loss reducer + 5%Redu2 + 2%NFA-25 + 1%PGCS-1 + 50%Weigh2.

[0048] Formula 2 is: 300mL water + 0.3%Na2CO3 + 0.2%NaOH + 2%Visco1 + 10%high temperature resistant fluid loss reducer + 0.5%NAT20 + 2%NFA-25 + 1%PGCS-1 + 50%Weigh2 + 10%Weigh3 + 180%barite.

[0049] Then, Formula 1 and Formula 2 were tested. The test results are shown in Table 5.

[0050] Table 5 Test results of formula 1 and formula 2 When the addition amount of high temperature resistant fluid loss reducer is 1% and 10% of water respectively, there is still obvious fluid loss reduction effect and strong temperature resistance.

[0051] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing a high temperature resistant fluid loss reducer, characterized in that: Water, acrylamide, N,N-dimethylacrylamide, vinyl acetate and a pH regulator for adjusting the pH value to alkaline are mixed, and then an initiator is added to carry out copolymerization reaction to obtain a high-temperature resistant fluid loss reducer.

2. The method for preparing the high temperature resistant fluid loss reducer according to claim 1, wherein: Calculated by weight, the water is 100 parts, acrylamide is 8-12 parts, N,N-dimethylacrylamide is 4-6 parts, vinyl acetate is 1-2 parts, pH regulator is 2-7 parts, and initiator is 1-5 parts.

3. The method for preparing the high temperature resistant fluid loss reducer according to claim 2, wherein: Calculated by weight, the water is 100 parts, acrylamide is 11 parts, N,N-dimethylacrylamide is 6 parts, vinyl acetate is 2 parts, pH regulator is 4 parts, and initiator is 4 parts.

4. The method for preparing the high temperature resistant fluid loss reducer according to claim 2, wherein: Calculated by weight, the water is 100 parts, acrylamide is 10 parts, N,N-dimethylacrylamide is 5 parts, vinyl acetate is 1 part, pH regulator is 5 parts, and initiator is 2 parts.

5. The method for preparing the high temperature resistant fluid loss reducer according to claim 1 or 2, wherein: The pH adjuster is soda ash.

6. The method for preparing the high temperature resistant fluid loss reducer according to claim 1, wherein: The initiator is a potassium sulfate aqueous solution, and the concentration of the potassium sulfate aqueous solution is 10%.

7. A high temperature resistant fluid loss reducer, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the high-temperature resistant fluid loss reducer according to claim 7 in preparing oilfield drilling fluid.

9. A drilling fluid, characterized in that: Contains the high temperature resistant fluid loss reducer according to claim 7.

10. The drilling fluid according to claim 9, characterized in that: The drilling fluid also includes water, and the amount of the high-temperature resistant fluid loss reducer added is 1% to 10% of the water.

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