A foam drilling fluid and its application

Abstract

This invention provides a foam drilling fluid and its application. The drilling fluid comprises a high-temperature resistant surfactant, a biodegradable foam stabilizer and thickener, hydrophobic nano-silica, and vegetable oil. The high-temperature resistant surfactant is synthesized by reacting natural rosin resin with diethylenetriaminepentaacetic acid; the biodegradable foam stabilizer and thickener is formed by graft polymerization of cassava starch and polyaspartic acid; the hydrophobic nano-silica is KH-550 modified nano-silica; and the vegetable oil used is rapeseed oil.

Description

Technical Field

[0001] This invention provides a foam drilling fluid, particularly a green and environmentally friendly non-water-based foam drilling fluid. Background Technology

[0002] Currently known water-based foam drilling fluids and oil-based foam drilling fluids have low biodegradability. For example, the diesel or white oil used in the base fluid of conventional oil-based foam drilling fluids has a certain destructive effect on the formation environment and has become a major obstacle to the development of oil-based drilling fluids. Summary of the Invention

[0003] One aspect of the present invention provides a drilling fluid comprising a high-temperature resistant surfactant, a biodegradable foam stabilizer and thickener, hydrophobic nano-silica, and vegetable oil.

[0004] In one specific embodiment, the high-temperature resistant surfactant is synthesized from natural yellow rosin resin and diethylenetriaminepentaacetic acid; the synthesis steps are as follows:

[0005] 1) Heat natural yellow rosin resin until it is completely softened to obtain softened yellow rosin;

[0006] 2) Dissolve softened yellow rosin in a solvent, add diethylenetriaminepentaacetic acid dropwise while stirring, adjust the pH value to 8 to 10, and continue stirring the reaction at 75 to 85°C for 8 to 10 hours. Dry the product to obtain the high-temperature resistant surfactant.

[0007] In one specific embodiment, the mass ratio of the natural yellow rosin resin to the diethylenetriaminepentaacetic acid is 1:0.2 to 1:0.3.

[0008] In one specific embodiment, the solvent is an aqueous solution of ethanol.

[0009] In one specific embodiment, the solvent is a 70 wt% to 80 wt% aqueous ethanol solution, for example, a 75 wt% aqueous ethanol solution.

[0010] In one specific embodiment, the biodegradable foam stabilizer and thickener is synthesized by graft polymerization of cassava starch and polyaspartic acid; the synthesis steps are as follows:

[0011] 1) Mix tapioca starch and water, and heat to obtain tapioca starch paste;

[0012] 2) Cassava starch paste is mixed with polyaspartic acid and ammonium persulfate and reacted to obtain the grafting reactant;

[0013] 3) The grafting reactant is mixed with ethanol to form a precipitate, which is then filtered and dried to obtain the biodegradable foam stabilizer and thickener.

[0014] In one specific embodiment, the mass ratio of cassava starch to water is 1:45 to 1:55.

[0015] In one specific embodiment, the mass ratio of the cassava starch to the polyaspartic acid is 1:3.5 to 1:4.5.

[0016] In one specific embodiment, the total mass of the cassava starch and the polyaspartic acid is taken as 100%, and the amount of ammonium persulfate is 1% to 1.5%.

[0017] In one specific embodiment, in step 1), the cassava starch paste is prepared at 80 to 90°C.

[0018] In one specific embodiment, in step 2), the reaction is carried out at 90 to 95°C for 4 to 6 hours.

[0019] In one specific embodiment, the hydrophobic nano-silica is KH-550 modified nano-silica (KH550-SiO2).

[0020] In one specific embodiment, the vegetable oil is rapeseed oil.

[0021] In one specific embodiment, based on the total mass of the vegetable oil as 100%, the amount of the high-temperature resistant surfactant is 0.2wt% to 0.3wt%, the amount of the biodegradable foam stabilizer and thickener is 0.3wt% to 0.4wt%, and the amount of the modified nano silica is 0.35wt% to 0.5wt%.

[0022] The beneficial effects of this invention are:

[0023] The drilling fluid half-life t of the present invention 1 / 2 It has a high temperature resistance of 180℃ for more than 120 minutes, a core permeability recovery value of more than 84%, a biodegradability of more than 80%, and good salt resistance. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0025] The hydrophobic nano silica was nano silica (KH550-SiO2) modified with coupling agent KH-550, purchased from Beijing Deco Island Gold Technology Co., Ltd., and its trade name was hydrophobic nano silica.

[0026] Preparation of high-temperature resistant surfactants

[0027] Example 1

[0028] 1) Heat the first-grade natural yellow rosin resin in a dry reaction flask at 80°C until it is completely softened to obtain softened yellow rosin;

[0029] 2) Dissolve 10g of softened yellow rosin in a 75wt% ethanol aqueous solution, add 2.5g of diethylenetriaminepentaacetic acid dropwise while stirring, adjust the pH value to 9, and continue stirring at 80℃ for 9h. After drying, high-temperature resistant surfactant 1# is obtained.

[0030] Example 2

[0031] 1) Heat the first-grade natural yellow rosin resin in a dry reaction flask at 75°C until it is completely softened to obtain softened yellow rosin;

[0032] 2) Dissolve 10g of softened yellow rosin in a 75wt% ethanol aqueous solution, add 2.0g of diethylenetriaminepentaacetic acid dropwise while stirring, adjust the pH value to 8, and continue stirring at 75℃ for 8h. After drying, high-temperature resistant surfactant 2# is obtained.

[0033] Example 3

[0034] 1) Heat the first-grade natural yellow rosin resin in a dry reaction flask at 85°C until it is completely softened to obtain softened yellow rosin;

[0035] 2) Dissolve 10g of softened yellow rosin in a 75wt% ethanol aqueous solution, add 3.0g of diethylenetriaminepentaacetic acid dropwise while stirring, adjust the pH value to 10, and continue stirring at 85℃ for 10h. After drying, high-temperature resistant surfactant 3# is obtained.

[0036] Preparation of biodegradable foam stabilizers and thickeners

[0037] Example 4

[0038] 1) Add 1g of tapioca starch to 50g of distilled water and heat to 85℃ to obtain tapioca starch paste;

[0039] 2) Add 4.0g of polyaspartic acid and 0.06g of ammonium persulfate to 51g of cassava starch paste, mix well, and react at 92.5℃ for 5h to obtain the grafted product;

[0040] 3) Mix the grafting reactant with 75g of anhydrous ethanol to form a precipitate, filter, and dry at 90℃ to obtain biodegradable foam stabilizer and thickener 1#.

[0041] Example 5

[0042] 1) Add 1g of tapioca starch to 55g of distilled water and heat to 80℃ to obtain tapioca starch paste;

[0043] 2) Add 3.8g of polyaspartic acid and 0.05g of ammonium persulfate to 56g of cassava starch paste, mix well, and react at 90℃ for 4h;

[0044] 3) Mix the grafting reactant with 50g of anhydrous ethanol to form a precipitate, filter, and dry at 80℃ to obtain biodegradable foam stabilizer and thickener 2#.

[0045] Example 6

[0046] 1) Add 1g of tapioca starch to 45g of distilled water and heat to 90℃ to obtain tapioca starch paste;

[0047] 2) Add 4.5g of polyaspartic acid and 0.0825g of ammonium persulfate to 46g of cassava starch paste, mix well, and react at 95℃ for 6h;

[0048] 3) Mix the grafting reactant with 100g of anhydrous ethanol to form a precipitate, filter, and dry at 100℃ to obtain biodegradable foam stabilizer and thickener 3#.

[0049] Drilling fluid preparation

[0050] Example 7

[0051] (1) Add 1000g of rapeseed oil to the mixer, adjust the speed to 10000r / min, and stir the rapeseed oil at high speed for 18min;

[0052] (2) Add 3.5g of biodegradable foam stabilizer and thickener 1# and 4.2g of modified nano silica, and continue stirring at 10000r / min for 18min to fully mix each component with 1000g of rapeseed oil to obtain an intermediate mixture;

[0053] (3) Add 2.5g of high-temperature resistant surfactant 1# to 1007.7g of intermediate mixture, and stir at 12000r / min for 2min to obtain foam drilling fluid 1#.

[0054] Example 8

[0055] (1) Add 1000g of rapeseed oil to the mixer, adjust the speed to 10000r / min, and stir the rapeseed oil at high speed for 20min;

[0056] (2) Add 4.0g of biodegradable foam stabilizer and thickener 1# and 5.0g of modified nano silica, and continue stirring at 10000r / min for 20min to fully mix each component with 1000g of rapeseed oil to obtain an intermediate mixture;

[0057] (3) Add 3.0g of high-temperature resistant surfactant 1# to 1009.0g of intermediate mixture, and stir at 12000r / min for 3min to obtain foam drilling fluid 2#.

[0058] Example 9

[0059] (1) Add 1000g of rapeseed oil to the mixer, adjust the speed to 10000r / min, and stir the rapeseed oil at high speed for 15min;

[0060] (2) Add 3.0g of biodegradable foam stabilizer and thickener 1# and 3.5g of modified nano silica, and continue stirring at 10000r / min for 15min to fully mix each component with 1000g of rapeseed oil to obtain an intermediate mixture;

[0061] (3) Add 2.0g of high-temperature resistant surfactant 1# to 1006.5g of intermediate mixture, and stir at 12000r / min for 1min to obtain foam drilling fluid 3#.

[0062] Example 10

[0063] (1) Add 1000g of rapeseed oil to the mixer, adjust the speed to 10000r / min, and stir the rapeseed oil at high speed for 18min;

[0064] (2) Add 3.5g of biodegradable foam stabilizer and thickener No. 2 and 4.2g of modified nano silica, and continue stirring at 10000r / min for 18min to fully mix each component with 1000g of rapeseed oil to obtain an intermediate mixture;

[0065] (3) Add 2.5g of high-temperature resistant surfactant 2# to 1007.7g of intermediate mixture, and stir at 12000r / min for 2min to obtain foam drilling fluid 4#.

[0066] Example 11

[0067] (1) Add 1000g of rapeseed oil to the mixer, adjust the speed to 10000r / min, and stir the rapeseed oil at high speed for 18min;

[0068] (2) Add 3.5g of biodegradable foam stabilizer and thickener 3# and 4.2g of modified nano silica, and continue stirring at 10000r / min for 18min to fully mix each component with 1000g of rapeseed oil to obtain an intermediate mixture;

[0069] (3) Add 2.5g of high-temperature resistant surfactant 3# to 1007.7g of intermediate mixture, and stir at 12000r / min for 2min to obtain foam drilling fluid 5#.

[0070] Comparative Example 1

[0071] (1) Add 1000g of white oil to the mixer, adjust the speed to 10000r / min, and stir the white oil at high speed for 18min;

[0072] (2) Add 3.5g of biodegradable foam stabilizer and thickener 1# and 4.2g of modified nano silica, and continue stirring at 10000r / min for 18min to fully mix each component with 1000g of white oil to obtain an intermediate mixture;

[0073] (3) Add 2.5g of high-temperature resistant surfactant 1# to 1007.7g of intermediate mixture, and stir at 12000r / min for 2min to obtain foam drilling fluid 6#.

[0074] Performance testing

[0075] 1. Determination of half-life

[0076] 1) Immediately after preparation, take 1000ml of each foam drilling fluid and pour it into a clean, dry 1000ml graduated cylinder. Start a stopwatch after pouring and observe the height of the foam drilling fluid in the graduated cylinder. When the volume of the precipitated liquid reaches 500ml, stop the stopwatch and record the half-life -t. 1 / 2 The results are shown in Table 1 (0% KCl solution).

[0077] 2) After the foam drilling fluids of Examples 7 to 11 are prepared, take five portions, each 1000 ml, and pour them into clean and dry 1500 ml graduated cylinders. Then, add 200 ml of KCl aqueous solution with concentrations of 2%, 4%, 6%, 8%, and 10% respectively. Stir at 10000 r / min for 2 min. Take 1000 ml of each portion and pour it into a clean and dry 1000 ml graduated cylinder. Start a stopwatch after pouring and observe the height of the foam drilling fluid in the graduated cylinder. When the volume of the precipitated liquid reaches 500 ml, stop the stopwatch and record the half-life -t. 1 / 2 The results are shown in Table 1.

[0078] 3) Take 1500 ml of the foam drilling fluid prepared in Examples 7 to 11 and put it into an aging kettle. After sealing, place it in a high-temperature roller furnace and roll it at 180°C for 20 hours. After taking it out, let it cool naturally to room temperature, pour it into a stirrer, and stir it at a high speed of 10000 r / min for 2 minutes. Then, measure the half-life -t of the foam drilling fluid after high-temperature aging. 1 / 2 The results are shown in Table 2 (0% KCl solution).

[0079] 4) Take 8000 ml of the foam drilling fluid prepared in Examples 7 to 11 respectively and put them into aging kettles. After sealing, place them in a high-temperature roller furnace and roll them at 180°C for 20 hours. After removing them and letting them cool naturally to room temperature, pour them into a stirrer and stir at 10000 r / min for 2 minutes. Then take five portions of aged foam drilling fluid, 1000 ml each, and pour them into clean and dry 1500 ml graduated cylinders. Then add 200 ml of KCl aqueous solution with a mass fraction of 2%, 4%, 6%, 8%, and 10% respectively. Stir at 10000 r / min for 2 minutes. Take 1000 ml of each portion and pour it into a clean and dry 1000 ml graduated cylinder. Start a stopwatch to observe the height of the foam drilling fluid in the graduated cylinder. When the volume of the precipitated liquid is 500 ml, stop the stopwatch and record the half-life after aging -t. 1 / 2 The results are shown in Table 2.

[0080] Table 1 Half-life of foam drilling fluid before aging

[0081]

[0082] Table 2 Half-life of foam drilling fluid after aging at 180℃

[0083]

[0084] According to the data in Tables 1 and 2, the foam drilling fluid of the present invention has good foaming effect and strong foam stability; the foam stability hardly decreases after aging at 180℃; it can resist the erosion of 10% KCl aqueous solution and has good salt resistance.

[0085] 2. Permeability Measurement

[0086] The evaluation criteria for the reservoir protection performance of the foam drilling fluids prepared in Examples 7 to 11 refer to SY / T6540-2002 "Indoor Evaluation Method for Damage to Oil Reservoirs by Drilling Fluids and Completion Fluids".

[0087] A dynamic filtration loss experiment was conducted using an artificial core with a diameter of 2.5 cm and a length of at least 5 cm at 50°C and a pressure of 2.5 MPa. The average permeability K of the core before it was damaged by drilling fluid was measured. o and the average permeability K of the damage od Calculate the recovery value. The formula for calculating the recovery value is as follows:

[0088] Recovery value R d =K od / K o ×100%.

[0089] The results are shown in Table 3.

[0090] Table 3 Core permeability recovery values

[0091] Example <![CDATA[K o / mD]]> <![CDATA[K od / mD]]> <![CDATA[R d / %]]> Example 7 9.16 8.25 90.1 Example 8 9.43 8.32 88.2 Example 9 11.05 10.29 93.1 Example 10 9.72 8.78 90.3 Example 11 10.45 8.79 84.2 Comparative Example 1 10.76 8.41 78.2

[0092] According to the data in Table 3, the foam drilling fluid of the present invention has a good reservoir protection effect and has little impact on the reservoir core permeability.

[0093] 3. Determination of biodegradability

[0094] The biodegradability of the foam drilling fluids prepared in Examples 7 to 11 was tested using the CEC L-33-A-93 method. 20g of the foam drilling fluids from Examples 7 to 11 were added to test bottles with 1g of *Bacillus luminifera* T3 seed powder, and incubated at 25±2℃ for 21 days as the experimental group. Test bottles containing only drilling fluid were used as the blank control group, omitting the incubation process. After incubation, the test bottles were vibrated with ultrasound to ensure uniform dispersion of the substances. Hydrochloric acid was then added to adjust the pH to 3, and the solution was extracted using 1,1,2,trichloroethane. The extracted solution was analyzed using IR spectroscopy, and the CH bond in the CH3-CH2- group was measured at a wavenumber of 2930±10 cm⁻¹. -1 The absorbance at the absorbance point is calculated, with E1 representing the absorbance of the experimental group and E0 representing the absorbance of the blank control group. The biodegradation rate is calculated using the following formula:

[0095] Biodegradation rate B = (E0 - E1) / E0 × 100%.

[0096] The results of the biodegradation rate are shown in Table 4.

[0097] According to the data in Table 4, the foam drilling fluid of the present invention has high biodegradability and can be decomposed under the action of microorganisms, making it green and environmentally friendly with no pollution to the environment.

[0098] Table 4. Biodegradability of Drilling Fluid

[0099] Example Biodegradability / % Example 7 86.6 Example 8 82.7 Example 9 89.7 Example 10 87.2 Example 11 80.2 Comparative Example 1 52.7

Claims

1. A drilling fluid comprising a surfactant, a biodegradable foam stabilizer and thickener, hydrophobic nano-silica, and vegetable oil; The surfactant is synthesized from natural yellow rosin resin and diethylenetriaminepentaacetic acid; The biodegradable foam stabilizer and thickener is formed by graft polymerization of cassava starch and polyaspartic acid.

2. The drilling fluid according to claim 1, characterized in that, The synthesis steps of the surfactant are as follows: 1) Heat natural yellow rosin resin until it is completely softened to obtain softened yellow rosin; 2) Dissolve softened yellow rosin in a solvent, add diethylenetriaminepentaacetic acid dropwise while stirring, adjust the pH value to 8 to 10, and continue stirring the reaction at 75 to 85°C for 8 to 10 hours. Dry the product to obtain the surfactant.

3. The drilling fluid according to claim 2, characterized in that, The mass ratio of the natural yellow rosin resin to the diethylenetriaminepentaacetic acid is 1:0.2 to 1:0.

3.

4. The drilling fluid according to claim 2, characterized in that, The solvent is an aqueous solution of ethanol.

5. The drilling fluid according to claim 4, characterized in that, The solvent is a 70wt% to 80wt% aqueous solution of ethanol.

6. The drilling fluid according to claim 1, characterized in that, The synthesis steps of the biodegradable foam stabilizer and thickener are as follows: 1) Mix tapioca starch and water, and heat to obtain tapioca starch paste; 2) Cassava starch paste is mixed with polyaspartic acid and ammonium persulfate and reacted to obtain the grafted product; 3) The grafting reactant is mixed with ethanol to form a precipitate, which is then filtered and dried to obtain the biodegradable foam stabilizer and thickener.

7. The drilling fluid according to claim 6, characterized in that, The mass ratio of the cassava starch to water is 1:45 to 1:55; and / or The mass ratio of the cassava starch to the polyaspartic acid is 1:3.5 to 1:4.5; and / or The total mass of the cassava starch and the polyaspartic acid is taken as 100%, and the amount of ammonium persulfate is 1% to 1.5%.

8. The drilling fluid according to claim 6, characterized in that, In step 1), the cassava starch paste is prepared at 80 to 90°C; In step 2), the reaction is carried out at 90 to 95°C for 4 to 6 hours.

9. The drilling fluid according to claim 1, characterized in that, The hydrophobic nano-silica is nano-silica modified with KH-550.

10. The drilling fluid according to claim 1, characterized in that, The vegetable oil is rapeseed oil.

11. The drilling fluid according to claim 1, characterized in that, Based on the total mass of the vegetable oil (100%), the amount of surfactant is 0.2wt% to 0.3wt%, the amount of biodegradable foam stabilizer and thickener is 0.3wt% to 0.4wt%, and the amount of hydrophobic nano-silica is 0.35wt% to 0.5wt%.

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