Strong-plugging environment-friendly drilling fluid as well as preparation and application thereof

Abstract

The invention discloses a strong-plugging environment-friendly drilling fluid which comprises the following components in parts by weight: 100 parts of water, 2.5-5 parts of bentonite, 0.09-0.18 part of anhydrous sodium carbonate, 0.8-1.2 parts of hydrolyzed polyacrylonitrile composite ammonium salt, 1 part of plant starch, 1.5-3 parts of a plugging agent, 0.8-1.2 parts of an emulsifier, 1.5-2 parts of an anti-collapse agent, 2-3 parts of 600-mesh superfine calcium carbonate, 0.5-0.8 part of an inhibitor and 13-23 parts of barite. The invention also discloses a preparation method and application thereof. The high-plugging environment-friendly drilling fluid provided by the invention can resist the temperature of 150 DEG C, has relatively high plugging capacity, good rheological property, relatively low filter loss, good lubricating property and stable performance, and provides a powerful guarantee for development of environment-sensitive areas.

Description

Technical Field

[0001] The present invention relates to a strong plugging environmental protection drilling fluid and its preparation and application. Background Art

[0002] The problem of wellbore instability has always been a technical problem in oil and gas exploitation. Hard and brittle shale contains many microcracks. Under high confining pressure, these cracks are compressed and closed. When the wellbore is opened, due to the secondary stress distribution, these cracks will open again. The drilling fluid first enters along these cracks, and then causes hydration collapse in the near-wellbore zone. Therefore, it is necessary to improve the plugging performance of the drilling fluid to prevent the intrusion of water in the drilling fluid into the shale and avoid the wellbore instability problem caused thereby.

[0003] Representative foreign environmental protection drilling fluid products include complex aluminum and high-performance water-based drilling fluid of Baker Hughes Company in the United States. The related technologies are relatively mature, the product performance is easy to control, non-toxic and harmless, but the product technical barriers are high and it is not suitable for the current exploitation requirements. Domestic environmental protection drilling fluids include environmental protection polymer drilling fluids, polysilicon-based water-based drilling fluids, and amine-based polymer drilling fluid systems, etc. At present, on-site tests have been carried out in related wells, but the plugging ability is insufficient for the problem of hard and brittle mudstone collapse.

[0004] Therefore, it has become an urgent need to develop a strong plugging environmental protection drilling fluid. Summary of the Invention

[0005] A strong plugging environmental protection drilling fluid, by weight, comprises the following components: 100 parts of water, 2.5 - 5 parts of bentonite, 0.09 - 0.18 parts of anhydrous sodium carbonate, 0.8 - 1.2 parts of hydrolyzed polyacrylonitrile composite ammonium salt, 1 part of plant starch, 1.5 - 3 parts of plugging agent, 0.8 - 1.2 parts of emulsifier, 1.5 - 2 parts of anti-collapse agent, 2 - 3 parts of 600-mesh ultrafine calcium carbonate, 0.5 - 0.8 parts of inhibitor, and 13 - 23 parts of barite.

[0006] In a specific embodiment, the amount of the plugging agent is 2 - 3 parts.

[0007] In a specific embodiment, the plant starch is corn starch and / or cassava starch.

[0008] In a specific embodiment, the plugging agent is castor oil and / or jojoba oil.

[0009] In a specific embodiment, the inhibitor is polyamine salt.

[0010] As another aspect of the present invention, it relates to a method for preparing the above-mentioned strong plugging environmental protection drilling fluid, comprising:

[0011] (1) Mix water, bentonite and anhydrous sodium carbonate under stirring conditions;

[0012] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, plant starch, plugging agent, emulsifier, shale inhibitor, ultra-fine calcium carbonate and inhibitor under stirring conditions, and mix them.

[0013] (3) Add barite under stirring conditions and mix.

[0014] In the above preparation method, in step (1), the conditions for the mixing reaction include: stirring at 11000 r / min for 20 minutes and then curing in a sealed state at 25 °C for 24 h; in step (2), the conditions for the mixing reaction include: stirring at 11000 r / min for 35 - 40 minutes; in step (3), the conditions for the mixing reaction include: stirring at 11000 r / min for 20 - 30 minutes.

[0015] As another aspect of the present invention, it relates to the application of the above-mentioned strong plugging environmental protection drilling fluid in oil and gas exploitation.

[0016] The strong plugging environmental protection drilling fluid provided by the present invention has a temperature resistance performance up to 150 °C, with strong plugging ability, good rheology, low filtration loss, good lubrication performance, and stable performance, providing a strong guarantee for the development of environmentally sensitive areas. Detailed implementation mode

[0017] The following examples are listed to specifically describe the present invention. It should be noted that the following examples are only for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made to the present invention still fall within the protection scope of the present invention.

[0018] The parts mentioned in this application are parts by mass.

[0019] Example 1

[0020] The strong plugging environmental protection drilling fluid I has the following components:

[0021] 100 parts of water, 2.5 parts of bentonite, 0.09 part of anhydrous sodium carbonate, 1 part of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant filtration reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 1 part of corn starch (Jinan Mingrun Chemical Co., Ltd.), 2 parts of jojoba oil (plugging agent, Hubei Xingdongcheng Chemical Co., Ltd.), 1 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 2 parts of white asphalt (shale inhibitor, Beijing Peikang Company, NFA-25), 3 parts of ultra-fine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.5 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 23 parts of barite (Sichuan Haiwo Petroleum Engineering Technology Co., Ltd.).

[0022] The preparation method of the strong plugging environmental protection drilling fluid I is as follows:

[0023] (1) Mix 100 parts of water, 2.5 parts of bentonite, and 0.09 part of anhydrous sodium carbonate under stirring conditions;

[0024] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, corn starch, jojoba oil, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions, and mix;

[0025] (3) Add barite under stirring conditions and mix.

[0026] In the above preparation method, in step (1), the mixing conditions include: stirring at 11000 r / min for 20 minutes and then curing in a sealed manner at 25 °C for 24 h; in step (2), the mixing conditions include: stirring at 11000 r / min for 35 minutes; in step (3), the mixing conditions include: stirring at 11000 r / min for 30 minutes.

[0027] Example 2

[0028] Strong plugging environmental protection drilling fluid II, the components are as follows:

[0029] 100 parts of water, 4 parts of bentonite, 0.14 part of anhydrous sodium carbonate, 1.2 parts of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant filtration reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 1 part of cassava starch (Hebei Danming Biotechnology Co., Ltd.), 2 parts of castor oil (plugging agent, Jinan Qingtian Chemical Technology Co., Ltd.), 1 part of jojoba oil (plugging agent, Hubei Xingdongcheng Chemical Co., Ltd.), 1 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 2 parts of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 2 parts of 600-mesh ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd.), 0.5 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 16 parts of barite (Sichuan Haiwo Petroleum Engineering Co., Ltd.).

[0030] The preparation method of the strong plugging environmental protection drilling fluid II is as follows:

[0031] (1) Mix 100 parts of water, 4 parts of bentonite, and 0.14 part of anhydrous sodium carbonate under stirring conditions;

[0032] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, cassava starch, castor oil, jojoba oil, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions, and mix;

[0033] (3) Add barite under stirring conditions and mix.

[0034] In the above preparation method, in step (1), the conditions for mixing include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25°C for 24 h; in step (2), the conditions for mixing include: stirring at 11000 r / min for 40 minutes; in step (3), the conditions for mixing include: stirring at 11000 r / min for 25 minutes.

[0035] Example 3

[0036] The strong plugging environmental protection drilling fluid III has the following components:

[0037] 100 parts of water, 5 parts of bentonite, 0.18 part of anhydrous sodium carbonate, 1 part of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant filtration reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 1 part of corn starch (Jinan Mingrun Chemical Co., Ltd.), 2 parts of castor oil (plugging agent, Jinan Qingtian Chemical Technology Co., Ltd.), 1.2 parts of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 1.8 parts of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 3 parts of ultra-fine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.8 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 13 parts of barite (Sichuan Haiwo Petroleum Engineering Technology Co., Ltd.).

[0038] The preparation method of the strong plugging environmental protection drilling fluid III is as follows:

[0039] (1) Mix 100 parts of water, 5 parts of bentonite, and 0.18 part of anhydrous sodium carbonate under stirring conditions;

[0040] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, corn starch, castor oil, emulsifier OP-10, white asphalt, ultra-fine calcium carbonate 600 mesh, and polyamine salt under stirring conditions and mix;

[0041] (3) Add barite under stirring conditions and mix;

[0042] In the above preparation method, in step (1), the conditions for mixing include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25°C for 24 h; in step (2), the conditions for mixing include: stirring at 11000 r / min for 35 minutes; in step (3), the conditions for mixing include: stirring at 11000 r / min for 20 minutes.

[0043] Example 4

[0044] The strong plugging environmental protection drilling fluid IV has the following components:

[0045] 100 parts of water, 2.5 parts of bentonite, 0.09 part of anhydrous sodium carbonate, 0.8 part of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant fluid loss reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 1 part of tapioca starch (Hebei Danming Biotechnology Co., Ltd.), 1.5 parts of jojoba oil (plugging agent, Hubei Xingdongcheng Chemical Co., Ltd.), 0.8 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 1.5 parts of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 3 parts of ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.5 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 20 parts of barite (Sichuan Haiwo Petroleum Engineering Co., Ltd.).

[0046] The preparation method of the strong plugging environmental protection drilling fluid IV is as follows:

[0047] (1) Mix 100 parts of water, 2.5 parts of bentonite, and 0.09 part of anhydrous sodium carbonate under stirring conditions;

[0048] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, tapioca starch, jojoba oil, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions and mix;

[0049] (3) Add barite under stirring conditions and mix.

[0050] In the above preparation method, in step (1), the mixing conditions include: stirring at 11000 r / min for 20 minutes and then curing in a sealed state at 25 °C for 24 h; in step (2), the mixing reaction conditions include: stirring at 11000 r / min for 40 minutes; in step (3), the mixing reaction conditions include: stirring at 11000 r / min for 30 minutes.

[0051] Comparative Example 1

[0052] The strong plugging environmental protection drilling fluid V has the following components:

[0053] 100 parts of water, 2.5 parts of bentonite, 0.09 part of anhydrous sodium carbonate, 1 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 2 parts of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 3 parts of ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.5 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 23 parts of barite (Sichuan Haiwo Petroleum Engineering Co., Ltd.).

[0054] The preparation method of the strong plugging environmental protection drilling fluid V is as follows:

[0055] (1) Mix 100 parts of water, 2.5 parts of bentonite, and 0.09 part of anhydrous sodium carbonate under stirring conditions;

[0056] (2) Add emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions, and mix;

[0057] (3) Add barite under stirring conditions.

[0058] In the above preparation method, in step (1), the conditions for mixing include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25 °C for 24 h; in step (2), the conditions for mixing include: stirring at 11000 r / min for 25 minutes; in step (3), the conditions for mixing include: stirring at 11000 r / min for 15 minutes.

[0059] Comparative Example 2

[0060] Strong plugging environmental protection drilling fluid VI has the following components:

[0061] 100 parts of water, 2.5 parts of bentonite, 0.09 part of anhydrous sodium carbonate, 1 part of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant filtration reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 2 parts of composite expansion polymer plugging agent (Bohai Drilling Engineering Technology Research Institute, BH-FDL), 0.8 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 1.5 parts of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 2 parts of ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.5 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 10 parts of barite (Sichuan Haiwo Petroleum Engineering Technology Co., Ltd.).

[0062] The preparation method of this strong plugging environmental protection drilling fluid VI is as follows:

[0063] (1) Mix 100 parts of water, 2.5 parts of bentonite, and 0.09 part of anhydrous sodium carbonate under stirring conditions;

[0064] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, composite expansion polymer plugging agent BH-FDL, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions, and mix;

[0065] (3) Add barite under stirring conditions and mix.

[0066] In the above preparation method, in step (1), the conditions for mixing include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25°C for 24 h; in step (2), the conditions for the mixing reaction include: stirring at 11000 r / min for 40 minutes; in step (3), the conditions for the mixing reaction include: stirring at 11000 r / min for 20 minutes.

[0067] Comparative Example 3

[0068] Strong plugging environmental protection drilling fluid VII, the components are as follows:

[0069] 100 parts of water, 6 parts of bentonite, 0.21 part of anhydrous sodium carbonate, 1.4 parts of hydrolyzed polyacrylonitrile composite ammonium salt (high temperature resistant filtration reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 1.1 parts of corn starch (Jinan Mingrun Chemical Co., Ltd.), 3.5 parts of jojoba oil (plugging agent, Hubei Xingdongcheng Chemical Co., Ltd.), 2 parts of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 3 parts of white asphalt (collapse prevention agent, Beijing Peikang Company, NFA-25), 4 parts of ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 1.5 parts of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 27 parts of barite (Sichuan Haiwo Petroleum Engineering Co., Ltd.).

[0070] The preparation method of the strong plugging environmental protection drilling fluid VII is as follows:

[0071] (1) Mix 100 parts of water, 6 parts of bentonite, and 0.21 part of anhydrous sodium carbonate under stirring conditions;

[0072] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, corn starch, jojoba oil, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions and mix;

[0073] (3) Add barite under stirring conditions and mix.

[0074] In the above preparation method, in step (1), the conditions for mixing include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25°C for 24 h; in step (2), the conditions for the mixing include: stirring at 11000 r / min for 50 minutes; in step (3), the conditions for the mixing include: stirring at 11000 r / min for 40 minutes.

[0075] Comparative Example 4

[0076] Strong plugging environmental protection drilling fluid VIII, the components are as follows:

[0077] 100 parts of water, 1.5 parts of bentonite, 0.05 part of anhydrous sodium carbonate, 0.5 part of hydrolyzed polyacrylonitrile composite ammonium salt (high-temperature resistant fluid loss reducer, Shijiazhuang Hualai Dingsheng Technology Co., Ltd., NH4-HPAN-2), 0.5 part of corn starch (Jinan Mingrun Chemical Co., Ltd.), 0.5 part of jojoba oil (plugging agent, Hubei Xingdongcheng Chemical Co., Ltd.), 0.5 part of emulsifier (Shandong Sanju Chemical Technology Co., Ltd., OP-10), 1 part of white asphalt (anti-collapse agent, Beijing Peikang Company, NFA-25), 1 part of ultrafine calcium carbonate (Shijiazhuang Hualang Mineral Products Co., Ltd., 600 mesh), 0.3 part of polyamine salt (inhibitor, Bohai Drilling Engineering Technology Research Institute, BZ-JAI), 3 parts of barite (Sichuan Haiwo Petroleum Engineering Co., Ltd.).

[0078] The preparation method of the strong plugging environmental protection drilling fluid VIII is as follows:

[0079] (1) Mix 100 parts of water, 1.5 parts of bentonite, and 0.05 part of anhydrous sodium carbonate under stirring conditions;

[0080] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, corn starch, jojoba oil, emulsifier OP-10, white asphalt, 600-mesh ultrafine calcium carbonate, and polyamine salt under stirring conditions, and mix;

[0081] (3) Add barite under stirring conditions and mix.

[0082] In the above preparation method, in step (1), the mixing conditions include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25 °C for 24 h; in step (2), the mixing conditions include: stirring at 11000 r / min for 30 minutes; in step (3), the mixing conditions include: stirring at 11000 r / min for 15 minutes.

[0083] Performance evaluation 1: The drilling fluid used in this example is the product prepared in Example 1.

[0084] High-temperature resistance performance: Test the high-temperature resistance ability of this product. The test method is as follows: Take 4 parts of the strong plugging environmental protection drilling fluid I prepared in Example 1, and conduct density, rheological property, fluid loss reduction property, and adhesion coefficient tests respectively. Among them, 1 part is tested at normal temperature, and the other 3 parts are tested after aging. The aging conditions are 90 °C × 16 h, 120 °C × 16 h, and 150 °C × 16 h respectively.

[0085] The test results are shown in Table 1 below.

[0086] Table 1

[0087]

[0088] As can be seen from the test results in Table 1, after the strong plugging environmental protection drilling fluid I was aged at 90 °C, 120 °C, and 150 °C for 16 h respectively, it had good rheological properties, appropriate viscosity and shear force, and stable water loss reduction performance, indicating that the strong plugging environmental protection drilling fluid I could resist high temperature of 150 °C. The adhesion coefficient was small, indicating that the strong plugging environmental protection drilling fluid I had good lubrication performance.

[0089] Environmental protection performance: Using the EC 50 value to evaluate the biological toxicity of the strong plugging environmental protection drilling fluid I, and using the BOD5 / COD Cr ratio to evaluate the biodegradability of the strong plugging environmental protection drilling fluid I.

[0090] The test results are shown in Table 2 below.

[0091] Table 2

[0092]

[0093]

[0094] As can be seen from Table 2, the strong plugging environmental protection drilling fluid I is non-toxic and easily degradable, meeting the requirements of environmental protection drilling fluid.

[0095] Sand bed plugging performance: Test the sand bed plugging performance of this product. The test method is as follows: Add 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm into the cylinder of the FA type non-permeable drilling fluid filter loss instrument, compact and level it, add 400 mL of the strong plugging environmental protection drilling fluid I, tighten the cup cover, adjust the pressure to 690 kPa, and test the sand bed filter loss volume for 30 minutes. The test result is 0 mL, indicating that the strong plugging environmental protection drilling fluid I has strong plugging performance.

[0096] Performance evaluation 2: The drilling fluid used in this example is the product prepared in Example 2.

[0097] High temperature resistance performance: Test the high temperature resistance ability of this product. The test method is as follows: Take 4 portions of the strong plugging environmental protection drilling fluid II prepared in Example 2, and conduct density, rheological property, water loss reduction property, and adhesion coefficient tests respectively. Among them, 1 portion is tested at normal temperature, and the other 3 portions are tested after aging. The aging conditions are 90 °C × 16 h, 120 °C × 16 h, and 150 °C × 16 h respectively.

[0098] The test results are shown in Table 3 below.

[0099] Table 3

[0100]

[0101] As can be seen from the test results in Table 3, after the strong plugging environmental protection drilling fluid II was aged at 90°C, 120°C, and 150°C for 16 hours respectively, it had good rheological properties, appropriate viscosity and shear force, and stable water loss reduction performance, indicating that the strong plugging environmental protection drilling fluid II could resist high temperatures up to 150°C. The adhesion coefficient was small, indicating that the strong plugging environmental protection drilling fluid II had good lubrication performance.

[0102] Environmental protection performance: The biological toxicity of the strong plugging environmental protection drilling fluid II was evaluated using the EC 50 value, and the biodegradability of the strong plugging environmental protection drilling fluid II was evaluated using the BOD5 / COD Cr ratio.

[0103] The test results are shown in Table 4 below.

[0104] Table 4

[0105] Project Indicator Result <![CDATA[EC 50 (mg.L -1 )]]> ＞20000 <![CDATA[4.8×10 6 > <![CDATA[BOD5 / COD Cr > 0.01≤Y≤0.05 0.02 <![CDATA[Total mercury (mg / kg -1 )]]> ≤15 0.00001 <![CDATA[Total Arsenic (mg.kg -1 )]]> ≤75 0.0624 <![CDATA[Total cadmium (mg.kg -1 )]]> ≤20 0.0125 <![CDATA[Total lead (mg / kg -1 )]]> ≤1000 0.302 <![CDATA[Total chromium (mg / kg -1 )]]> ≤1000 0.285

[0106] As can be seen from Table 4, the strong plugging environmental protection drilling fluid II is non-toxic and easily degradable, meeting the requirements of environmental protection drilling fluid.

[0107] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method was as follows: 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm was added to the cylindrical barrel of the FA type non-permeable drilling fluid filter loss instrument, compacted and leveled, 400 mL of the strong plugging environmental protection drilling fluid II was added, the cup cover was tightened, the pressure was adjusted to 690 kPa, and the sand bed filter loss volume was measured for 30 minutes. The test result was 0 mL, indicating that the strong plugging environmental protection drilling fluid II had strong plugging performance.

[0108] Performance evaluation 3: The drilling fluid used in this example was the product prepared in Example 3.

[0109] High temperature resistance performance: The high temperature resistance ability of this product was tested. The test method was as follows: 4 portions of the strong plugging environmental protection drilling fluid III prepared in Example 3 were taken, and the density, rheological properties, water loss reduction performance, and adhesion coefficient were tested respectively. Among them, 1 portion was tested at room temperature, and the other 3 portions were tested after aging. The aging conditions were 90°C × 16 h, 120°C × 16 h, and 150°C × 16 h respectively.

[0110] The test results are shown in Table 5 below.

[0111] Table 5

[0112]

[0113]

[0114] As can be seen from the test results in Table 5, after the strong plugging environmental protection drilling fluid III was aged at 90 °C, 120 °C, and 150 °C for 16 h respectively, it had good rheological properties, appropriate viscosity and shear force, and stable water loss reduction performance, indicating that the strong plugging environmental protection drilling fluid III could resist high temperature of 150 °C. The adhesion coefficient was small, indicating that the strong plugging environmental protection drilling fluid III had good lubrication performance.

[0115] Environmental protection performance: The EC 50 value was used to evaluate the biological toxicity of the strong plugging environmental protection drilling fluid III, and the BOD5 / COD Cr ratio was used to evaluate the biodegradability of the strong plugging environmental protection drilling fluid III.

[0116] The test results are shown in Table 6 below.

[0117] Table 6

[0118] Project Indicator Result <![CDATA[EC 50 (mg.L -1 )]]> ＞20000 <![CDATA[2.3×10 6 > <![CDATA[BOD5 / COD Cr > 0.01≤Y≤0.05 0.03 <![CDATA[Total mercury (mg.kg -1 )]]> ≤15 0.00001 <![CDATA[Total Arsenic (mg.kg -1 )]]> ≤75 0.1518 <![CDATA[Total cadmium (mg.kg -1 )]]> ≤20 0.0165 <![CDATA[Total Lead (mg.kg -1 )]]> ≤1000 1.630 <![CDATA[Total chromium (mg / kg -1 )]]> ≤1000 1.385

[0119] As can be seen from Table 6, the strong plugging environmental protection drilling fluid III is non-toxic and easily degradable, meeting the requirements of environmentally friendly drilling fluids.

[0120] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method was as follows: 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm was added to the cylindrical barrel of the FA type non-permeable drilling fluid filter loss instrument, compacted and leveled, 400 mL of the strong plugging environmental protection drilling fluid III was added, the cup cover was tightened, the pressure was adjusted to 690 kPa, and the sand bed filter loss volume was measured for 30 minutes. The test result was 0 mL, indicating that the strong plugging environmental protection drilling fluid III had strong plugging performance.

[0121] Performance evaluation 4: The drilling fluid used in this example was the product prepared in Example 4.

[0122] High temperature resistance performance: The high temperature resistance ability of this product was tested. The test method was as follows: 4 portions of the strong plugging environmental protection drilling fluid IV prepared in Example 4 were taken, and the density, rheological properties, water loss reduction performance, and adhesion coefficient were tested respectively. Among them, 1 portion was tested at room temperature, and the other 3 portions were tested after aging. The aging conditions were 90 °C × 16 h, 120 °C × 16 h, and 150 °C × 16 h respectively.

[0123] The test results are shown in Table 7 below.

[0124] Table 7

[0125]

[0126] As can be seen from the test results in Table 7, after the strong plugging environmental protection drilling fluid IV was aged at 90 °C, 120 °C, and 150 °C for 16 h respectively, it had good rheological properties, appropriate viscosity and shear force, and stable water loss reduction performance, indicating that the strong plugging environmental protection drilling fluid IV could resist high temperature of 150 °C. The adhesion coefficient was small, indicating that the strong plugging environmental protection drilling fluid IV had good lubrication performance.

[0127] Environmental protection performance: The EC 50 value was used to evaluate the biological toxicity of the strong plugging environmental protection drilling fluid IV, and the BOD5 / COD Cr ratio was used to evaluate the biodegradability of the strong plugging environmental protection drilling fluid IV.

[0128] The test results are shown in Table 8 below.

[0129] Table 8

[0130] Project Indicator Result <![CDATA[EC 50 (mg.L -1 )]]> ＞20000 <![CDATA[5.2×10 6 > <![CDATA[BOD5 / COD Cr > 0.01≤Y≤0.05 0.03 <![CDATA[Total mercury (mg.kg -1 )]]> ≤15 0.00002 <![CDATA[Total Arsenic (mg.kg -1 )]]> ≤75 0.2605 <![CDATA[Total Cadmium (mg.kg -1 )]]> ≤20 0.3055 <![CDATA[Total lead (mg / kg -1 )]]> ≤1000 1.050 <![CDATA[Total chromium (mg / kg -1 )]]> ≤1000 1.030

[0131] As can be seen from Table 8, the strong plugging environmental protection drilling fluid IV was non-toxic and easily degradable, meeting the requirements of environmental protection drilling fluid.

[0132] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method was as follows: 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm was added to the cylinder of the FA type non-permeable drilling fluid filter loss instrument, compacted and leveled, 400 mL of the strong plugging environmental protection drilling fluid IV was added, the cup cover was tightened, the pressure was adjusted to 690 kPa, and the sand bed filter loss volume was tested for 30 minutes. The test result was 2 mL, indicating that the strong plugging environmental protection drilling fluid IV had strong plugging performance.

[0133] Performance evaluation 5: The drilling fluid used in this example was the product prepared in Comparative Example 1.

[0134] High temperature resistance performance: The high temperature resistance ability of this product was tested. The test method was as follows: 4 portions of the strong plugging environmental protection drilling fluid V prepared in Comparative Example 1 were taken, and the density, rheological properties, water loss reduction performance, and adhesion coefficient were tested respectively. Among them, 1 portion was tested at room temperature, and the other 3 portions were tested after aging. The aging conditions were 90 °C × 16 h, 120 °C × 16 h, and 150 °C × 16 h respectively.

[0135] The test results are shown in Table 9 below.

[0136] Table 9

[0137]

[0138] As can be seen from the test results in Table 9, after the strong plugging environmental protection drilling fluid V was aged at 90°C, 120°C, and 150°C for 16 hours respectively, its rheological properties, viscosity and gel strength, and water loss reduction performance deteriorated, indicating that the strong plugging environmental protection drilling fluid V does not have high temperature resistance. The large adhesion coefficient indicates that the strong plugging environmental protection drilling fluid V has poor lubrication performance.

[0139] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method is as follows: Add 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm into the cylinder of the FA type non-permeable drilling fluid filter loss instrument, compact and level it, add 400 mL of the strong plugging environmental protection drilling fluid V, tighten the cup cover, adjust the pressure to 690 kPa, and test the sand bed filter loss volume for 30 minutes. The test result was 320 mL, indicating that the strong plugging environmental protection drilling fluid V does not have plugging performance.

[0140] Performance evaluation 6: The drilling fluid used in this example is the product prepared in Comparative Example 2.

[0141] High temperature resistance performance: The high temperature resistance ability of this product was tested. The test method is as follows: Take 4 portions of the strong plugging environmental protection drilling fluid VI prepared in Comparative Example 2, and conduct density, rheological properties, water loss reduction performance, and adhesion coefficient tests respectively. One portion was tested at room temperature, and the other 3 portions were tested after aging. The aging conditions were 90°C×16 h, 120°C×16 h, and 150°C×16 h respectively.

[0142] The test results are shown in Table 10 below.

[0143] Table 10

[0144]

[0145] As can be seen from the test results in Table 10, after the strong plugging environmental protection drilling fluid VI was aged at 90°C and 120°C for 16 hours respectively, its rheological properties were good, the viscosity and gel strength were appropriate, and the water loss reduction performance was stable, indicating that the strong plugging environmental protection drilling fluid V can resist high temperature of 120°C. After the strong plugging environmental protection drilling fluid VI was aged at 150°C for 16 hours, its rheological properties, viscosity and gel strength, and water loss reduction performance deteriorated, indicating that the strong plugging environmental protection drilling fluid VI has poor high temperature resistance ability at 150°C. The large adhesion coefficient indicates that the strong plugging environmental protection drilling fluid VI has poor lubrication performance.

[0146] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method is as follows: Add 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm into the cylinder of the FA type non-permeable drilling fluid filter loss instrument, compact and level it, add 400 mL of the strong plugging environmental protection drilling fluid VI, tighten the cup cover, adjust the pressure to 690 kPa, and test the sand bed filter loss volume for 30 minutes. The test result was 280 mL, indicating that the strong plugging environmental protection drilling fluid VI has poor plugging performance.

[0147] Performance evaluation 7: The drilling fluid used in this example is the product prepared in Comparative Example 3.

[0148] Temperature resistance performance: Test the temperature resistance ability of this product. The test method is as follows: Take 4 portions of the strong plugging environmental protection drilling fluid VII prepared in Comparative Example 3, and conduct density, rheological property, filtration loss reduction property, and adhesion coefficient tests respectively. Among them, 1 portion is tested at room temperature, and the other 3 portions are tested after aging. The aging conditions are 90°C × 16 h, 120°C × 16 h, and 150°C × 16 h respectively.

[0149] The test results are shown in Table 11 below.

[0150] Table 11

[0151]

[0152]

[0153] It can be seen from the test results in Table 11 that after the strong plugging environmental protection drilling fluid VII is aged at 90°C for 16 h, its rheological property is good, the viscosity and shear force are appropriate, and the filtration loss reduction property is stable, indicating that the strong plugging environmental protection drilling fluid VII can resist high temperature of 90°C. After the strong plugging environmental protection drilling fluid VII is aged at 120°C and 150°C for 16 h respectively, the rheological property, viscosity and shear force, and filtration loss reduction property become worse, indicating that the strong plugging environmental protection drilling fluid VII has poor ability to resist high temperature of 120°C. The adhesion coefficient is small, indicating that the strong plugging environmental protection drilling fluid VII has good lubrication performance.

[0154] Sand bed plugging performance: Test the sand bed plugging performance of this product. The test method is as follows: Add 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm into the cylinder of the FA type non-permeable drilling fluid filter loss instrument, compact and level it, add 400 mL of the strong plugging environmental protection drilling fluid VII, tighten the cup cover, adjust the pressure to 690 kPa, and test the sand bed filtration loss volume for 30 minutes. The test result is 20 mL, indicating that the strong plugging environmental protection drilling fluid VII has poor plugging performance.

[0155] Performance evaluation 8: The drilling fluid used in this example is the product prepared in Comparative Example 4.

[0156] Temperature resistance performance: Test the temperature resistance ability of this product. The test method is as follows: Take 4 portions of the strong plugging environmental protection drilling fluid VIII prepared in Comparative Example 4, and conduct density, rheological property, filtration loss reduction property, and adhesion coefficient tests respectively. Among them, 1 portion is tested at room temperature, and the other 3 portions are tested after aging. The aging conditions are 90°C × 16 h, 120°C × 16 h, and 150°C × 16 h respectively.

[0157] The test results are shown in Table 12 below.

[0158] Table 12

[0159]

[0160]

[0161] As can be seen from the test results in Table 12, after the strong plugging environmental protection drilling fluid VIII is aged for 16 h at 90 °C, 120 °C and 150 °C respectively, its rheological properties, viscosity and filtration loss reduction properties deteriorate, indicating that the strong plugging environmental protection drilling fluid VIII has poor high-temperature resistance. The adhesion coefficient is relatively large, indicating that the strong plugging environmental protection drilling fluid VIII has poor lubrication performance.

[0162] Sand bed plugging performance: The sand bed plugging performance of this product was tested. The test method was as follows: 300 g of quartz sand with a particle size between 0.45 mm and 0.90 mm was added to the cylindrical barrel of the FA type non-permeable drilling fluid filter loss instrument, compacted and leveled, 400 mL of the strong plugging environmental protection drilling fluid VIII was added, the cup cover was tightened, the pressure was adjusted to 690 kPa, and the sand bed filtration loss volume was measured for 30 minutes. The test result was 120 mL, indicating that the strong plugging environmental protection drilling fluid VIII has poor plugging performance.

[0163] In the above embodiments, as can be seen from Embodiment 1 and Comparative Example 1, the environmental protection drilling fluid added with plugging agent, plant starch and high-temperature resistant filtration loss reducer has good plugging performance and high-temperature resistance, while the environmental protection drilling fluid without adding plugging agent, plant starch and high-temperature resistant filtration loss reducer does not have plugging performance and high-temperature resistance.

[0164] As can be seen from Embodiments 1 to 4 and Comparative Example 2, the plugging agents castor oil and jojoba oil have good sand bed plugging performance, while the sand bed plugging performance of the plugging agent composite expansion polymer type BH-FDL is poor. Moreover, as can be seen from Embodiments 1 to 4 and Comparative Examples 1 to 4, castor oil and jojoba oil also make the drilling fluid have good lubrication performance at the same time. The addition amount of castor oil and / or jojoba oil is preferably 1.5 - 3 parts.

[0165] As can be seen from Embodiments 1 to 4 and Comparative Examples 2 to 3, the compound use of hydrolyzed polyacrylonitrile composite ammonium salt and corn starch or cassava starch has good filtration loss reduction effect, and the compounding ratio is 0.8 - 1.2:1.

[0166] The temperature resistance performance and sand bed plugging performance of the drilling fluid systems in Examples 1 to 4 are significantly better than those in Comparative Examples 3 to 4. It can be seen that 100 parts of water, 2.5 - 5 parts of bentonite, 0.09 - 0.18 parts of anhydrous sodium carbonate, 0.8 - 1.2 parts of hydrolyzed polyacrylonitrile composite ammonium salt, 1 part of plant starch, 1.5 - 3 parts of plugging agent, 0.8 - 1.2 parts of emulsifier, 1.5 - 2 parts of anti-collapse agent, 2 - 3 parts of 600-mesh ultra-fine calcium carbonate, 0.5 - 0.8 parts of inhibitor, and 13 - 23 parts of barite are the preferred reaction conditions. Further, among these preferred examples, the sand bed plugging performance of Examples 1 to 3 is better. Therefore, the addition amount of the plugging agent is further preferably 2 - 3 parts.

[0167] The preparation method of the strong plugging and environmentally friendly drilling fluid of the present invention includes the following steps:

[0168] (1) Mix water, bentonite and anhydrous sodium carbonate under stirring conditions;

[0169] (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, plant starch, plugging agent, emulsifier, anti-collapse agent, ultra-fine calcium carbonate and inhibitor under stirring conditions and mix;

[0170] (3) Add barite under stirring conditions and mix.

[0171] In the above preparation method, in step (1), the conditions of the mixing reaction include: stirring at 11000 r / min for 20 minutes and then curing in a closed state at 25 °C for 24 h; in step (2), the conditions of the mixing reaction include: stirring at 11000 r / min for 35 - 40 minutes; in step (3), the conditions of the mixing reaction include: stirring at 11000 r / min for 20 - 30 minutes.

Claims

1. A strong plugging environmental protection drilling fluid, characterized in that, By weight parts, it comprises the following components: 100 parts of water, 2.5 - 5 parts of bentonite, 0.09 - 0.18 parts of anhydrous sodium carbonate, 0.8 - 1.2 parts of hydrolyzed polyacrylonitrile composite ammonium salt, 1 part of plant starch, 1.5 - 3 parts of plugging agent, 0.8 - 1.2 parts of emulsifier, 1.5 - 2 parts of shale inhibitor, 2 - 3 parts of 600 - mesh ultra - fine calcium carbonate, 0.5 - 0.8 parts of inhibitor, 13 - 23 parts of barite.

2. The strong plugging environmental protection drilling fluid according to claim 1, characterized in that, The amount of the plugging agent is 2 - 3 parts.

3. The strong plugging environmental protection drilling fluid according to claim 1, characterized in that, The plant starch is corn starch and / or tapioca starch.

4. The strong plugging environmental protection drilling fluid according to claim 1, characterized in that, The plugging agent is castor oil and / or jojoba oil.

5. The strong plugging environmental protection drilling fluid according to claim 1, characterized in that The inhibitor is polyamine salt.

6. A method for preparing the strong plugging environmental protection drilling fluid according to any one of claims 1-5, characterized in that, It includes: (1) Mix water, bentonite and anhydrous sodium carbonate under stirring conditions; (2) Add hydrolyzed polyacrylonitrile composite ammonium salt, plant starch, plugging agent, emulsifier, shale inhibitor, ultra - fine calcium carbonate and inhibitor under stirring conditions and mix; (3) Add barite under stirring conditions and mix.

7. The method according to claim 6, characterized in that, In step (1), the conditions of the mixing reaction include: stir at 11000 r / min for 20 minutes and then cure in a sealed state at 25 °C for 24 h.

8. The method according to claim 6, characterized in that, In step (2), the conditions of the mixing reaction include: stir at 11000 r / min for 35 - 40 minutes.

9. The method according to claim 6, wherein In step (3), the conditions of the mixing reaction include: stir at 11000 r / min for 20 - 30 minutes.

10. Application of the strong - plugging environmental - protection drilling fluid according to any one of claims 1 - 5 in oil and gas exploitation.

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