Foam drilling fluid, preparation method and application

Abstract

The invention provides a foam drilling fluid as well as a preparation method and application thereof. The foam drilling fluid is prepared from the following raw material components in percentage by mass: 0.9%-1.3% of a foaming agent, 0.1%-0.5% of a foam stabilizer, 0.7%-1.2% of an anti-pollution agent, 0.4%-0.8% of an anti-compression agent and 96.2%-97.9% of water, and the total mass percentage of the raw material components is 100%. The foam drilling fluid disclosed by the invention is high in foaming rate, good in foam stability, similar to a scraping cream shape after foaming, high in foam fluid viscosity, moderate in flowability and uniform in distribution; the heat capacity of the foam drilling fluid is higher than that of a gas-phase circulating medium, the foam drilling fluid belongs to a surfactant and is good in lubricating effect, and when the foam drilling fluid is applied to air screw foam drilling of a soft and broken coal seam, rock debris generated in the drilling process can be effectively carried out of a hole, repeated breaking in construction is reduced, and the drilling efficiency is improved; compared with liquid-phase drilling fluid, the foam drilling fluid is small in density, low in circulation speed, small in pressure and scouring effect on hole walls, not prone to causing collapse of the hole walls and capable of effectively blocking holes of soft coal seams.

Description

Technical Field

[0001] This invention belongs to the field of energetic materials preparation technology, specifically relating to a foam drilling fluid, its preparation method, and its application. Background Technology

[0002] Soft coal seams have low mechanical strength and are prone to borehole wall collapse during drilling, leading to stuck drill bits and other problems. Air screw directional drilling technology is an effective solution to these issues. Air screw drills convert the pressure energy of the circulating medium into mechanical energy to drive the drill bit's rotation. However, long-term practice has revealed serious dust pollution and difficulty in carrying coal dust. To effectively reduce dust pollution and improve rock and coal dust carrying capacity, foam drilling fluid with higher viscosity, similar density to air, and minimal scouring and disturbance to the borehole wall can be used as the circulating medium instead of air. However, existing ordinary foam has poor pressure resistance and breaks down significantly under pressure, thus failing to perform its normal function. Therefore, there is an urgent need to develop a foam drilling fluid with high foaming capacity, stable foam, and strong pressure resistance and pollution resistance. Summary of the Invention

[0003] In view of the defects and deficiencies of the existing technology, the purpose of this invention is to provide a foam drilling fluid, a preparation method and an application, so as to solve the technical problem of the lack of a foam drilling fluid suitable for air screw foam drilling in soft and broken coal seams.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A foam drilling fluid comprises, by mass percentage, the following raw material components: 0.9% to 1.3% foaming agent, 0.1% to 0.5% foam stabilizer, 0.7% to 1.2% anti-foaming agent, 0.4% to 0.8% anti-pressure agent, and 96.2% to 97.9% water, wherein the total mass percentage of each raw material component is 100%.

[0006] The present invention also has the following technical features:

[0007] Specifically, the foaming agent is selected from one or more of sodium alkylbenzene sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium chloride.

[0008] Furthermore, the foam stabilizer is selected from one or more of xanthan gum, polyvinyl alcohol, and polyacrylamide;

[0009] Furthermore, the antifouling agent is selected from one or more of fatty alcohol polyoxyethylene ether, octamethyltrisiloxane, and sodium α-alkenylsulfonate.

[0010] Furthermore, the anti-compression agent is selected from one or more of broad bean gum, lignocellulose, and tianqing gum.

[0011] Furthermore, it includes the following raw material components: 1.3% sodium alkylbenzene sulfonate, 0.5% xanthan gum, 0.9% fatty alcohol polyoxyethylene ether, 0.6% fava bean gum, and 96.7% water.

[0012] This invention also protects a method for preparing foam drilling fluid, comprising the following steps:

[0013] Step 1: Add the foaming agent to water and stir at 600-800 rpm for 2-10 minutes to obtain solution A;

[0014] Step 2: Add a foam stabilizer to solution A and stir at 600-800 rpm for 8-15 minutes to obtain solution B;

[0015] Step 3: Add anti-fouling agent to solution B and stir at 600-800 rpm for 2-10 minutes to obtain solution C;

[0016] Step 4: Add antifouling agent to solution C, stir at 600-800 rpm for 30-40 minutes to obtain solution D, let stand for 2-3 hours to obtain foam drilling fluid;

[0017] The foam drilling fluid comprises, by mass percentage, the following raw material components: 0.9% to 1.3% foaming agent, 0.1% to 0.5% foam stabilizer, 0.7% to 1.2% anti-fouling agent, 0.4% to 0.8% anti-pressure agent, and the balance being water.

[0018] Preferably, the preparation method specifically includes the following steps:

[0019] Step 1: Add 1.3g of sodium alkylbenzene sulfonate to 96.7g of water and stir at 600-800rpm for 2min to obtain solution A;

[0020] Step 2: Add 0.5g xanthan gum to solution A and stir at 600-800rpm for 10min to obtain solution B;

[0021] Step 3: Add 0.9g of fatty alcohol polyoxyethylene ether to solution B and stir at 600-800 rpm for 3 minutes to obtain solution C;

[0022] Step 4: Add 0.6g of broad bean gum to solution C, stir at 600-800 rpm for 30 minutes to obtain solution D, let stand for 2 hours to obtain foam drilling fluid.

[0023] This invention also protects the application of the above-mentioned foam drilling fluid in air screw foam drilling of soft and broken coal seams.

[0024] Compared with the prior art, the present invention has the following beneficial technical effects:

[0025] (1) The foam drilling fluid provided by the present invention has a high foaming rate, good foam stability, and is similar to a face cream after foaming. The foam fluid has high viscosity, moderate fluidity and uniform distribution. The heat capacity of the foam drilling fluid is higher than that of the gas phase circulation medium. Moreover, the foam drilling fluid is a surfactant and has good lubrication effect.

[0026] (2) The preparation method provided by the present invention is simple and can save on-site preparation time, ensuring that the indoor formula can be accurately applied to the construction site.

[0027] (3) Applying the foam drilling fluid provided by the present invention to air screw foam drilling in soft and broken coal seams can effectively carry the rock cuttings generated during the drilling process out of the hole, reduce repeated crushing during construction, and improve drilling efficiency. Compared with liquid phase drilling fluid, foam drilling fluid has a lower density, slower circulation speed, and less pressure and scouring effect on the hole wall, making it less likely to cause hole wall collapse. At the same time, foam has the Jamin effect, which can effectively seal the pores of soft coal seams, thereby reducing drilling fluid loss.

[0028] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0029] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0030] The technical concept of this invention is as follows: Currently, foam drilling fluids for soft and fractured coal seams suffer from poor foam stability, poor compressive strength, and poor anti-contamination ability, failing to meet application requirements. Therefore, this invention comprehensively considers the performance and cost requirements of foam drilling fluids for soft and fractured coal seams, selecting one or more foaming agents as the main agent, and adding admixtures (foam stabilizers, anti-contamination agents, and anti-compression agents) to improve the stability, compressive strength, and anti-contamination performance of the foam drilling fluid. During the selection process, it is ensured that the various admixtures have a good synergistic effect with the main foaming agent, without excessively affecting the stability of the foam drilling fluid. Even better, some admixtures may further improve the stability of the foam drilling fluid. In particular, the added anti-compression agents improve the stability of the foam drilling fluid while ensuring that the compressive strength of the drilling fluid meets the requirements, thus improving its overall performance.

[0031] This invention protects a foam drilling fluid, comprising, by mass percentage, the following raw material components: 0.9%–1.3% foaming agent, 0.1%–0.5% foam stabilizer, 0.7%–1.2% antifoaming agent, 0.4%–0.8% pressure-resistant agent, and 96.2%–97.9% water, wherein the total mass percentage of each raw material component is 100%.

[0032] Preferably, the foaming agent is selected from one or more of sodium alkylbenzene sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium chloride.

[0033] Preferably, the foam stabilizer is selected from one or more of xanthan gum, polyvinyl alcohol, and polyacrylamide.

[0034] Preferably, the antifouling agent is selected from one or more of fatty alcohol polyoxyethylene ether, octamethyltrisiloxane and sodium α-alkenylsulfonate.

[0035] In this invention, the foam expansion amount test, half-life test and compressive strength test are all conducted using an existing non-permeability filtration instrument, and the foaming is carried out using a six-unit high-speed mixer.

[0036] Unless otherwise specified, all materials used in this invention are commercially available.

[0037] Example 1

[0038] Following the above technical solution, this embodiment discloses a foam drilling fluid, which is prepared by the following method:

[0039] Step 1: Take 97.97g of water and slowly add 0.9g of sodium alkylbenzene sulfonate to it. During the addition process, use a low-speed stirrer to stir at a speed of 600-800rpm for 2 minutes to ensure that the 0.9g of sodium alkylbenzene sulfonate is completely dissolved to obtain solution A.

[0040] Step 2: Add 0.5g xanthan gum to solution A and stir at 600-800rpm for 10min to obtain solution B. Since xanthan gum is hygroscopic and prone to clumping, it is easy to form flocculent aggregates during the addition process. Therefore, it is necessary to stir with a low speed stirrer during the addition process to ensure that it is fully dissolved.

[0041] Step 3: Add 0.9g of fatty alcohol polyoxyethylene ether to solution B and stir at 600-800 rpm for 3 minutes to obtain solution C;

[0042] Step 4: Add 0.6g of broad bean gum to solution C. Broad bean gum solution has similar problems as xanthan gum, such as easy moisture absorption and clumping, and difficulty in dissolving. Therefore, it is necessary to stir with a low speed stirrer during the addition process to make it fully dissolved. In this embodiment, the stirring speed is 600-800 rpm for 30 minutes to obtain solution D. After standing for 2 hours, a brown or light yellow foam drilling fluid is obtained.

[0043] The foam drilling fluid prepared in this embodiment has high viscosity, moderate fluidity, and uniform distribution.

[0044] The foaming amount and half-life of the prepared foam drilling fluid were tested. The foaming amount is related to the performance and dosage of the foaming agent, the performance and dosage of the foam stabilizer, and the influence of other admixtures. The greater the foaming amount, the better the performance of the foam drilling fluid. The longer the half-life of the foam, the better the stability of the foam drilling fluid. The test results are shown in Table 1.

[0045] The foam drilling fluid prepared in this embodiment was subjected to a pressure test using a non-permeability filter. A pressure of 0.8 MPa was applied, and the volume change of the foam fluid before and after pressurization was compared to determine the strength of the foam's pressure resistance. The results are shown in Table 2.

[0046] Anti-pollution tests were conducted on the foam drilling fluid prepared in this embodiment. 3 mL of deep underground brine was added to 97 mL of foam drilling fluid to simulate groundwater pollution. The difference in foaming volume between the groups before and after the addition of groundwater was compared to determine the strength of the anti-pollution ability of the foam drilling fluid. The anti-pollution results are shown in Table 3.

[0047] The foam drilling fluid prepared in this embodiment can be used for air screw foam drilling in soft and broken coal seams.

[0048] Specifically, a coal mine needs to construct horizontal gas extraction boreholes in soft, fractured coal seams (f-value ≤ 0.5). These seams are prone to collapse and significant leakage. Conventional air drilling is prone to jamming, while water drilling exacerbates borehole wall softening. A foam drilling fluid is used in conjunction with an air screw drill for directional drilling, achieving efficient slag removal, wall protection, and cooling. In use, the raw material components of the foaming fluid prepared in this embodiment are mixed evenly in a six-axis high-speed mixer before replacing the existing drilling medium.

[0049] Application results show that the foam drilling fluid provided in this embodiment can effectively carry rock cuttings generated during drilling out of the borehole, reducing repeated breakage during construction and improving drilling efficiency. Because foam drilling fluid has a lower density and slower circulation speed than liquid drilling fluid, it exerts less pressure and scouring on the borehole wall, making it less likely to cause borehole collapse. Simultaneously, the foam exhibits the Jamin effect, effectively sealing the pores of soft coal seams, thereby reducing drilling fluid loss.

[0050] Example 2

[0051] This embodiment discloses a foam drilling fluid, the preparation method of which is the same as that of Example 1, the only difference being the raw material ratio. In this embodiment, the content of each raw material component by mass percentage is: sodium alkylbenzene sulfonate 1.1%, xanthan gum 0.3%, fatty alcohol polyoxyethylene ether 1%, broad bean gum 0.6%, and water 97%. A brown or light yellow foam drilling fluid is finally obtained.

[0052] Finally, a brown or light yellow foam drilling fluid was obtained. The foaming amount and half-life of the obtained foam drilling fluid were tested, and the test results are shown in Table 1.

[0053] The foam drilling fluid prepared in this embodiment was subjected to a pressure test using the test method used in Example 1, and the results are shown in Table 2.

[0054] The anti-contamination test was conducted on the foam drilling fluid prepared in this embodiment using the test method used in Example 1, and the results are shown in Table 3.

[0055] Example 3

[0056] This embodiment discloses a foam drilling fluid, the preparation method of which is the same as that of the raw material composition in Example 1, the only difference being the raw material ratio. In this embodiment, the content of each raw material component is: sodium alkylbenzene sulfonate 0.9%, xanthan gum 0.1%, fatty alcohol polyoxyethylene ether 0.7%, broad bean gum 0.4%, and water 97.9%.

[0057] The final product is a brown or light yellow foam drilling fluid.

[0058] The foaming amount and half-life of the foam drilling fluid prepared in this embodiment were tested, and the test results are shown in Table 1.

[0059] The foam drilling fluid prepared in this embodiment was subjected to a pressure test using the test method used in Example 1, and the results are shown in Table 2.

[0060] The anti-contamination test was conducted on the foam drilling fluid prepared in this embodiment using the test method used in Example 1, and the results are shown in Table 3.

[0061] Example 1 Example 2 Example 3 Foaming volume (mL) 490 500 500 Foam half-life (min) 81 78 70

[0062] Table 1. Property test results of foam drilling fluids in Examples 1-3

[0063] As can be seen from Table 1, the foaming amount of the foam drilling fluids prepared in Examples 1 to 3 is basically stable, indicating that foam drilling fluids can be prepared by the method of the present invention.

[0064] Comparative Example 1

[0065] This comparative example discloses a foam drilling fluid, the preparation method and raw material composition of which are basically the same as those in Example 1, the only difference being that no pressure-resistant agent is added in this comparative example.

[0066] The compressive strength test was conducted on the foam drilling fluid prepared in this comparative example using the compressive strength test method used in Example 1, and the results are shown in Table 2.

[0067] Pressurized to 0.8 MPa Example 1 Example 2 Example 3 Comparative Example 1 Volume before pressurization 500 500 490 520 Volume after pressurization 85 80 75 70 Foam compression ratio 83％ 84％ 84.7％ 86.5％ Foam half-life (min) 57 63 72 45

[0068] Table 2. Results of foam drilling fluid compressive strength tests in Examples 1-3 and Comparative Example 1

[0069] As can be seen from Table 2, the foam compression ratio of the foam drilling fluids prepared in Examples 1-3 is significantly lower than that of the foam drilling fluid prepared in Comparative Example 1, indicating that the foam drilling fluid prepared by the method of the present invention has better compressibility.

[0070] Comparative Example 2

[0071] This comparative example discloses a foam drilling fluid, the preparation method and raw material composition of which are basically the same as those in Example 1, the only difference being that no anti-fouling agent is added in this comparative example.

[0072] The anti-fouling test method used in Example 1 was used to test the anti-fouling properties of the foam drilling fluid prepared in this comparative example. The results are shown in Table 3.

[0073] Add 3mL of deep brine Example 1 Example 2 Example 3 Comparative Example 2 Volume before adding brine 490 500 500 520 Volume after adding brine 450 455 450 300 Foam volume reduction rate 8.1％ 9％ 10％ 42.3％

[0074] Table 3. Results of anti-foaming test of foam drilling fluid in Examples 1-3 and Comparative Example 2

[0075] As can be seen from Table 3, the foam volume reduction rate of the foam drilling fluids prepared in Examples 1 to 3 is much smaller than that of Comparative Example 2 without the addition of anti-pollution agent, indicating that the foam drilling fluid provided by the present invention effectively improves the ability to resist groundwater pollution.

[0076] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0078] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A foam drilling fluid, characterized in that, By mass percentage, it includes the following raw material components: foaming agent 0.9%–1.3%, foam stabilizer 0.1%–0.5%, antifoaming agent 0.7%–1.2%, anticompression agent 0.4%–0.8%, and water 96.2%–97.9%, with the total mass percentage of each raw material component being 100%.

2. The foam drilling fluid as described in claim 1, characterized in that, The foaming agent is selected from one or more of sodium alkylbenzene sulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium chloride.

3. The foam drilling fluid as described in claim 1, characterized in that, The foam stabilizer is selected from one or more of xanthan gum, polyvinyl alcohol, and polyacrylamide.

4. The foam drilling fluid as described in claim 1, characterized in that, The antifouling agent is selected from one or more of fatty alcohol polyoxyethylene ether, octamethyltrisiloxane and sodium α-alkenylsulfonate.

5. The foam drilling fluid as described in claim 1, characterized in that, The anti-compression agent is selected from one or more of broad bean gum, lignocellulose, and Tianqing gum.

6. The foam drilling fluid as described in claim 1, characterized in that, It comprises the following raw material components: sodium alkylbenzene sulfonate 1.3%, xanthan gum 0.5%, fatty alcohol polyoxyethylene ether 0.9%, fava bean gum 0.6%, and water 96.7%.

7. A method for preparing foam drilling fluid, characterized in that, Includes the following steps: Step 1: Add the foaming agent to water and stir at 600-800 rpm for 2-10 minutes to obtain solution A; Step 2: Add a foam stabilizer to solution A and stir at 600-800 rpm for 8-15 minutes to obtain solution B; Step 3: Add anti-fouling agent to solution B and stir at 600-800 rpm for 2-10 minutes to obtain solution C; Step 4: Add antifouling agent to solution C, stir at 600-800 rpm for 30-40 minutes to obtain solution D, let stand for 2-3 hours to obtain foam drilling fluid; The foam drilling fluid comprises, by mass percentage, the following raw material components: 0.9% to 1.3% foaming agent, 0.1% to 0.5% foam stabilizer, 0.7% to 1.2% anti-fouling agent, 0.4% to 0.8% anti-pressure agent, and the balance being water.

8. The method for preparing foam drilling fluid as described in claim 7, characterized in that, Specifically, the following steps are included: Step 1: Add 1.3g of sodium alkylbenzene sulfonate to 96.7g of water and stir at 600-800rpm for 2min to obtain solution A; Step 2: Add 0.5g xanthan gum to solution A and stir at 600-800rpm for 10min to obtain solution B; Step 3: Add 0.9g of fatty alcohol polyoxyethylene ether to solution B and stir at 600-800 rpm for 3 minutes to obtain solution C; Step 4: Add 0.6g of broad bean gum to solution C, stir at 600-800 rpm for 30 minutes to obtain solution D, let stand for 2 hours to obtain foam drilling fluid.

9. The application of the foam drilling fluid as described in any one of claims 1 to 6 in air screw foam drilling of soft and broken coal seams.