A high-temperature resistant organic clay for drilling fluid and its preparation method

Abstract

This invention relates to an organic clay for high-temperature drilling fluids and its preparation method. The organic clay, by weight, comprises the following raw material components: 30-50 parts purified sodium-based montmorillonite, 10-30 parts attapulgite, 1-10 parts modifier, and 10-30 parts intercalating agent. This invention uses montmorillonite as a base material and employs long-chain quaternary ammonium salts to increase the interlayer spacing of montmorillonite, thereby improving the dispersibility and rheological properties of the organic clay in oil-based drilling fluids. The attapulgite is modified using hydroxyl acids. The modified attapulgite surface contains suspended hydroxyl and carboxyl groups, which can further react with montmorillonite to form chemical bonds for secondary stabilization, greatly improving the temperature resistance of the organic clay. Even at 260℃, it still exhibits a high colloidal content and good viscosity-enhancing and shear-lifting effects, meeting the drilling application requirements of deep wells, ultra-deep wells, and complex wells.

Description

Technical Field

[0001] This invention belongs to the field of drilling fluid technology, specifically, it relates to an organic clay for high-temperature drilling fluid and its preparation method. Background Technology

[0002] The increasing number of deep, ultra-deep, and complex wells worldwide places higher demands on drilling fluid technology. Ultra-deep well drilling faces bottom-hole temperatures exceeding 200°C, requiring drilling fluids to possess "three highs and one long," namely, high temperature resistance, high density, high salinity resistance, and long-term performance stability. Otherwise, it is difficult to guarantee the rheological properties and wellbore stability of the drilling fluid. Organoclase is the most widely used rheology control agent in oil-based drilling fluids. Due to its good oleophilicity and large interlayer spacing, organoclase can control the rheological behavior of oil-based drilling fluids by dispersing and swelling in base oil. However, at high temperatures, organoclase modifiers are prone to desorption and dissociation, and emulsifiers are prone to demulsification. Existing drilling fluid treatment agents and drilling fluid systems can no longer fully meet the needs of ultra-deep well drilling technology. Therefore, the development of organoclase for high-temperature resistant oil-based drilling fluids is extremely urgent.

[0003] Drilling fluid organic clay is an oleophilic colloidal material obtained by modifying montmorillonite with organic modifiers. The basic structural unit of montmorillonite consists of two layers of tetrahedral silica sheets sandwiching a layer of octahedral silica sheets, making it a typical layered silicate clay mineral. Due to isomorphic substitution, the crystal layers of montmorillonite carry a certain amount of structural negative charge. To maintain electroneutrality, an equal amount of cations can be adsorbed between the layers. Conventional organic clay is generally modified from montmorillonite through a single intercalation and adsorption of long-chain quaternary ammonium salts. The quaternary ammonium salt and montmorillonite layers are mainly connected through charge interactions. Under high-temperature conditions, the adsorbed long-chain quaternary ammonium salt modifier is easily dispersed and desorbed, leading to the failure of the organic clay.

[0004] Invention patents CN102827591A, CN103773324B, CN104017549B, and CN114539992A all disclose schemes for modifying montmorillonite into synthesized organic clays using long-chain quaternary ammonium salts as modifiers. These organic clays exhibit high colloid content and good shearing and thickening effects when evaluated below 150℃, but their performance deteriorates significantly above 180℃. Chinese patent CN113336238A provides an organic clay for high-temperature resistant water-in-oil drilling fluids and its preparation method, using 1-octadecenetrimethylammonium chloride as an intercalating agent and simultaneously introducing a chelating agent. The resulting organic clay exhibits good thickening and shearing effects at high temperatures, but its rheological properties fail to meet usage requirements after hot rolling at 260℃. Summary of the Invention

[0005] The purpose of this invention is to solve the problem of poor temperature resistance of existing organic soils for drilling fluids, and to provide a high-temperature resistant organic soil for drilling fluids with high colloid content and good viscosity-enhancing and shearing effects at high temperatures, as well as its preparation method. The temperature resistance of this organic soil can reach 260℃.

[0006] The high-temperature resistant drilling fluid organic clay of the present invention comprises, by weight, the following raw material components: 30-50 parts purified sodium montmorillonite, 10-30 parts attapulgite, 1-10 parts modifier, and 10-30 parts intercalating agent.

[0007] The purified sodium montmorillonite is obtained by purifying sodium montmorillonite through hydrocyclone separation. The parameters of the purified sodium montmorillonite are: cation exchange capacity 125-135 mmol / g, expansion capacity 90-100 mL / g, gel value >500 mL / (15g), and montmorillonite content 90-95% by weight; preferably, the cation exchange capacity is 130 mmol / g, the expansion capacity is 94 mL / g, the gel value is >500 mL / (15g), and the montmorillonite content is 92.5% by weight.

[0008] It should be noted that the volume of the gel formed by mixing sodium bentonite and water in a certain proportion and adding an appropriate amount of magnesium oxide is called the gel valence. It is expressed in milliliters as the volume of gel formed from 15 grams of sample.

[0009] Furthermore, the modifier is β-hydroxypropionic acid or β-hydroxybutyric acid.

[0010] Furthermore, the intercalating agent is one of n-alkyltrimethylammonium chloride or n-alkyltrimethylammonium bromide, wherein n = 12, 14, 16, or 18.

[0011] The high-temperature resistant drilling fluid organic clay described in this invention is prepared by the following method:

[0012] 1) Mix 30-50 parts of purified sodium montmorillonite and 1000 parts of water and stir evenly. Then add the intercalating agent, adjust the pH of the mixture to 7-8 and stir evenly to obtain the intercalating mixture.

[0013] 2) Mix 10-30 parts of attapulgite, 100 parts of water and 100 parts of ethanol and stir well. Then add the modifier, adjust the pH of the mixture to 2-3, and stir well to obtain the modified attapulgite mixture.

[0014] 3) Mix the intercalation mixture obtained in step 1) and the attapulgite modified mixture obtained in step 2), stir evenly at 75-80℃, then cool, filter, wash, dry, crush and sieve to obtain organic clay for oil-based drilling fluid.

[0015] Further, in step 1), the purified sodium montmorillonite is mixed with 1000 parts of water and stirred at 75-80°C for 30 minutes; a modifier is added and the pH is adjusted to 2-3, and stirring is continued for 2 hours.

[0016] Further, in step 1), the attapulgite clay, water and 1% ethanol are mixed and stirred at 70-75°C for 10 minutes; a modifier is added and the pH is adjusted to 2-3, and stirring is continued for 2 hours.

[0017] Furthermore, in steps 1) and 2), the pH is adjusted using a 0.01–0.1 mol / L hydrochloric acid or sodium hydroxide solution.

[0018] Further, in step 3), the above intercalation mixture and attapulgite modified mixture are mixed and stirred at 75-80°C for 2 hours; the mixture is repeatedly washed with deionized water to remove Br- and Cl-, and the clear supernatant is tested with silver nitrate until no white precipitate is produced.

[0019] Further, in step 3), the product is dried in an oven at 100–105°C for 16–18 hours, and then pulverized and passed through a 200-mesh sieve.

[0020] The outstanding effects of this invention are:

[0021] The high-temperature resistant organic clay for drilling fluids prepared by the method of this invention still exhibits good viscosity-enhancing and shear-lifting effects at 260℃. Long-chain quaternary ammonium salts, acting as intercalating agents, can effectively penetrate the interlayer of montmorillonite, increasing the interlayer spacing to a certain extent and improving the dispersibility and rheological properties of the organic clay in oil-based drilling fluids. Modification of attapulgite with β-hydroxypropionic acid or β-hydroxybutyric acid allows its hydroxyl and carboxyl groups to selectively react with the oxygen bonds on the surface of attapulgite. The modified attapulgite surface contains suspended hydroxyl and carboxyl groups, which can further react with montmorillonite to form chemical bonds. The different layers of attapulgite and montmorillonite are connected by chemical bonds and physically overlapped, making the interlayer of montmorillonite more stable, thereby significantly improving its temperature resistance. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0023] Example 1

[0024] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of dodecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #1.

[0025] Example 2

[0026] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of tetradecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #2.

[0027] Example 3

[0028] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of hexadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #3.

[0029] Example 4

[0030] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of hexadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 10g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #4.

[0031] Example 5

[0032] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 15g of hexadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #5.

[0033] Example 6

[0034] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of hexadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxybutyric acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. -The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #6.

[0035] Example 7

[0036] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of octadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxypropionic acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #7.

[0037] Example 8

[0038] Weigh 50g of sodium montmorillonite, add 1000mL of deionized water, stir at 75-80℃ for 30min, add 20g of octadecyltrimethylammonium chloride, adjust the pH to 7-8 with hydrochloric acid, and continue stirring for 2h to obtain the intercalation mixture. Weigh 20g of attapulgite, add 100mL of ethanol and 100mL of water, stir at 70-75℃ for 10min, add 5g of β-hydroxybutyric acid, adjust the pH to 2-3, and continue stirring for 2h to obtain the attapulgite-modified mixture. Mix the intercalation mixture and the attapulgite-modified mixture, stir at 75-80℃ for 2h, then cool to room temperature, and repeatedly wash and filter with deionized water to remove Cl. - The supernatant was tested with silver nitrate until no white precipitate was formed. It was then dried at 100–105°C for 16–18 hours, followed by pulverization through a 200-mesh sieve to obtain organic soil #8.

[0039] The samples prepared in the above embodiments were subjected to performance testing and compared with similar products on the market:

[0040] Method for determining the colloidal content at room temperature: Add 200 mL of No. 0 diesel oil to a high-speed stirring cup, place it in a water bath, and bring the temperature to 30℃±1℃. While stirring at 11000 r / min, add 4.0 g (accurate to 0.01 g) of organic soil sample and stir at high speed for 10 min to obtain organic soil test solution. Pour the organic soil test solution into a stoppered graduated cylinder to 100 mL, and start a stopwatch to record the volume V of the free oil in the upper part after 90 min.

[0041] Calculate the colloid content J, % using the following formula:

[0042]

[0043] Method for determining the colloid content after aging: The above organic soil test solution was poured into a high-temperature aging tank and aged at 180℃ and 260℃ for 16 hours. After aging, it was cooled to room temperature and stirred at high speed at 11000r / min for 10 minutes. Then it was poured into a stoppered graduated cylinder to 100mL. At the same time, a stopwatch was started to record the volume V of the free oil in the upper part at 90 minutes. The colloid ratio was calculated according to formula (1).

[0044]

[0045] The colloidal content data from different embodiments and comparative examples show that the colloidal content of the organic soil prepared in the embodiments of the present invention in diesel oil at room temperature is higher than that of commercially available organic soil, and the overall gelation effect is very good. The results after aging at 180℃ and 260℃ show that the colloidal content of the organic soil prepared in the examples decreases slightly, and its temperature resistance is better than that of commercially available samples.

[0046] Methods for determining the properties of organic soil suspensions:

[0047] Add 340 mL of No. 0 diesel oil and 12.0 g of Span 80 (accurate to 0.01 g, the same below) to a high-speed stirring cup. Stir at 11000 r / min for 10 min, then add 60 mL of water and continue stirring for 10 min. While stirring, add 16.0 g of organic soil sample and stir at high speed for 20 min. During the stirring process, ensure that no sample adheres to the cup wall and keep the temperature of the test solution between 25℃ and 30℃. After stirring, use a six-speed rotational viscometer to measure the stable readings of the viscometer at 600 r / min, 300 r / min and 3 r / min at 50℃±1℃, and calculate the apparent viscosity, plastic viscosity and dynamic shear force.

[0048] The prepared test solution was placed in a high-temperature aging tank and then placed in a roller heating furnace. After aging at 260°C for 16 hours, it was taken out and stirred at 11000 r / min for 20 minutes. After stirring, the apparent viscosity, plastic viscosity, and dynamic shear force were measured and calculated.

[0049]

[0050]

[0051] As can be seen from the table above, the organic soil synthesized in the examples exhibits good suspension ability in oil-based systems and a temperature resistance of up to 260℃. Its overall performance is significantly superior to commercially available products.

[0052] In summary, this invention first uses long-chain quaternary ammonium salts to intercalate and modify purified sodium-based soil, and then uses hydroxy acid-modified attapulgite to perform secondary stabilization, thus developing a high-temperature resistant organic soil for oil-based drilling fluids that can meet the drilling application requirements of deep wells, ultra-deep wells, and complex wells.

Claims

1. A type of organic soil for high-temperature drilling fluid, characterized in that, By weight, it includes the following raw material components: 30-50 parts purified sodium montmorillonite, 10-30 parts attapulgite, 1-10 parts modifier, and 10-30 parts intercalating agent.

2. The organic soil according to claim 1, characterized in that, The purified sodium montmorillonite is obtained by purifying sodium montmorillonite through hydrocyclone separation. The parameters of the purified sodium montmorillonite are: cation exchange capacity 125-135 mmol / g, expansion capacity 90-100 mL / g, gel value >500 mL / (15g), and montmorillonite content 90-95% by weight; preferably, the cation exchange capacity is 130 mmol / g, the expansion capacity is 94 mL / g, the gel value is >500 mL / (15g), and the montmorillonite content is 92.5% by weight.

3. The organic soil according to claim 1, characterized in that, The modifier is β-hydroxypropionic acid or β-hydroxybutyric acid.

4. The organic soil according to claim 1, characterized in that, The intercalating agent is one of n-alkyltrimethylammonium chloride or n-alkyltrimethylammonium bromide, wherein n = 12, 14, 16 or 18.

5. The organic soil according to any one of claims 1 to 4, characterized in that... It is prepared by the following method: 1) Mix 30-50 parts of purified sodium montmorillonite and 1000 parts of water and stir evenly. Then add the intercalating agent, adjust the pH of the mixture to 7-8 and stir evenly to obtain the intercalating mixture. 2) Mix 10-30 parts of attapulgite, 100 parts of water and 100 parts of ethanol and stir well. Then add the modifier, adjust the pH of the mixture to 2-3, and stir well to obtain the modified attapulgite mixture. 3) Mix the intercalation mixture obtained in step 1) and the attapulgite modified mixture obtained in step 2), stir evenly at 75-80℃, then cool, filter, wash, dry, crush and sieve to obtain organic clay for oil-based drilling fluid.

6. The preparation method according to claim 5, characterized in that, In step 1), the purified sodium montmorillonite is mixed with 1000 parts of water and stirred at 75-80℃ for 30 minutes; after adding the modifier and adjusting the pH to 2-3, stirring is continued for 2 hours.

7. The preparation method according to claim 5, characterized in that, In step 1), attapulgite, water and 1% ethanol are mixed and stirred at 70-75°C for 10 minutes; a modifier is added and the pH is adjusted to 2-3, and stirring is continued for 2 hours.

8. The preparation method according to claim 5, characterized in that, In steps 1) and 2), the pH is adjusted using a 0.01–0.1 mol / L hydrochloric acid or sodium hydroxide solution.

9. The preparation method according to claim 5, characterized in that, Step 3) Mix the above intercalation mixture and attapulgite modified mixture and stir at 75-80℃ for 2 hours; wash repeatedly with deionized water to remove Br- and Cl-, and test the clear supernatant with silver nitrate until no white precipitate is produced.

10. The preparation method according to claim 5, characterized in that, Dry in an oven at 100–105°C for 16–18 hours, then pulverize and pass through a 200-mesh sieve.

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