Environment-friendly slurry suitable for deep coal seam and preparation method thereof

Abstract

The invention relates to the technical field of drilling fluid, and discloses environment-friendly slurry suitable for a deep coal seam, which comprises an anti-collapse agent HB-PA-S, a filtrate reducer DAADS, a tackifier GZN, a lubricant MPA, a nano plugging agent AR / SiO2 and a reservoir protective agent. The invention further discloses a preparation method of the environment-friendly slurry suitable for the deep coal seam. The salt resistance, temperature resistance and environmental protection performance of the drilling fluid are improved, the drilling fluid has high sealing property, water can be prevented or delayed from entering well wall rock pores from a well hole in 200 DEG C and saturated salt water, the bonding force among mineral particles in rock is increased, and meanwhile, the surface property of a soil layer is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of drilling fluids, and particularly to an environment-friendly mud suitable for deep coal seams and a preparation method thereof. Background Art

[0002] The problem of wellbore instability frequently occurs. Especially for the complex environment of deep coal seams, the soil layer is relatively soft. The primary reason for wellbore instability is the diffusion of pore pressure, that is, due to the drilling fluid filtrate entering the rock pores, the pore pressure increases, the effective bonding force between mineral particles decreases accordingly, and the rock strength also decreases. Secondly, the bonding force of non-chemical cementation such as hydrogen bonds between mineral particles such as formation clay is damaged by water, such as: clay hydration swelling and dispersion, anhydrite absorbing water and swelling into gypsum dihydrate, dissolution of water-soluble salt rock, etc.

[0003] These chemical factors causing wellbore instability all take effect on the premise that water enters the wellbore rock formation from the wellbore. Therefore, the effective ways for a collapse prevention agent used to maintain the stability of the wellbore in easily collapsible formations mainly have two aspects: one is to prevent or delay water from entering the wellbore rock pores, that is, to eliminate or reduce the driving force of water migration and increase the resistance of water migration; the other is to increase the bonding force between mineral particles in the rock. Therefore, an effective drilling fluid should effectively prevent or slow down water from entering the wellbore rock pores and increase the bonding force between mineral particles in the rock.

[0004] However, with the increase in the number of high-temperature deep wells and the increase in the probability of drilling through complex formations, more stringent requirements are put forward for the temperature resistance and salt resistance of drilling fluid treatment agents. When the temperature is too high or salt invasion occurs due to a sharp increase in the salt concentration in the drilling fluid, if the drilling fluid is easily decomposed at high temperatures or the treatment agent has insufficient salt invasion resistance, serious accidents such as wellbore enlargement and wellbore collapse will occur.

[0005] At the same time, for treatment agent drilling fluids, most of the currently widely used high-temperature and high-salt water-based drilling fluid treatment agents cannot meet both engineering needs and environmental protection requirements. For example, there is a lack of a filtrate reducer that can meet both high-temperature and high-salt resistance and environmental protection requirements: the currently widely used sulfonated drilling fluid filtrate reducer can withstand relatively high temperatures, but its environmental performance is poor. The existing polymer filtrate reducers at home and abroad have low toxicity, but their temperature resistance is <180°C and their biodegradability is poor. Asphalt-based plugging agents have good plugging effects, but they have high toxicity, are difficult to degrade, and have a relatively dark color, and their environmental performance is poor.

[0006] It can be seen that there is a lack of drilling fluids in the prior art that can meet both high-temperature and high-salt resistance and environmental protection requirements. Therefore, there is an urgent need to study new high-temperature and high-salt resistant and environment-friendly materials. Summary of the Invention

[0007] The object of the present invention is to provide an environmentally friendly mud suitable for deep coal seams and a preparation method thereof, so as to solve the technical problem that the drilling fluid in the prior art is difficult to simultaneously meet the requirements of high temperature and salt resistance and environmental protection.

[0008] To solve the above technical problems, the present invention specifically provides the following technical solutions:

[0009] The present invention provides an environmentally friendly mud suitable for deep coal seams, including a sloughing prevention agent HB-PA-S, a filtration loss reducer DAADS, a viscosifier GZN, a lubricant MPA, a nano plugging agent AR / SiO2, and a reservoir protection agent; wherein, the sloughing prevention agent HB-PA-S is a modified nano-silica hyperbranched polymer with a main chain of C-C and C-N bonds and a terminal functional group of sulfonic acid group, and the structural formula of the sloughing prevention agent HB-PA-S is as Figure 1 shown; the filtration loss reducer DAADS is a polymer containing C-C, C-N, and C-S bonds in the main chain and functional groups such as carbonyl group, imino group, sulfonic acid group, and quaternary ammonium group; the viscosifier GZN is a polymer containing an amide group in the main chain, an EO group in the long side chain, and a sulfonic acid group functional group; the lubricant MPA is a saturated alkane with an S element content of up to 35.49% and an N element content of up to 2.59%; the molecular structural formula of the nano plugging agent AR / SiO2 is as Figure 12 shown; the reservoir protection agent is a polymer with a branched structure, containing heat-resistant sulfonic acid groups, Si-C and other groups.

[0010] As a preferred scheme of the present invention, by mass percentage, the content of the sloughing prevention agent HB-PA-S is 1.0-5.0%; the content of the filtration loss reducer DAADS is 1.0-3.0%; the content of the viscosifier GZN is 0.1-1.0%; the content of the lubricant MPA is 2.0-3.0%; the content of the nano plugging agent AR / SiO2 is 1.0-3.0%; the content of the reservoir protection agent is 0.1-0.5%.

[0011] The present invention provides a preparation method of an environmentally friendly mud suitable for deep coal seams, including the following steps:

[0012] Add the sloughing prevention agent HB-PA-S, the filtration loss reducer DAADS, the viscosifier GZN, the lubricant MPA, the nano plugging agent AR / SiO2, and the reservoir protection agent into water, and mix evenly to obtain the environmentally friendly mud.

[0013] As a preferred scheme of the present invention, it further includes a preparation method of the sloughing prevention agent HB-PA-S, and the steps are as follows:

[0014] Graft hyperbranched polyamide on the surface of nano-silica to obtain a product;

[0015] Modify the groups at the ends of the product with aminoethanesulfonic acid to obtain the anti-collapse agent HB-PA-S.

[0016] As a preferred embodiment of the present invention, it further includes a preparation method of the filtrate reducer DAADS, and the steps are as follows:

[0017] Weigh AMPS and dissolve it in water, and successively add AM, DMAM, SAS, DMDAAC, and MBA, and stir until completely dissolved to obtain a mixed solution;

[0018] Adjust the pH of the mixed solution with 30% NaOH, heat the mixed solution to a set temperature, add an initiator, and carry out the reaction under nitrogen protection to obtain a viscous liquid product;

[0019] Purify the liquid product repeatedly with acetone, and dry and crush it at 103 °C to obtain the powdery filtrate reducer DAADS.

[0020] As a preferred embodiment of the present invention, it further includes a preparation method of the viscosifier GZN, and the steps are as follows:

[0021] Mix Span 80, white oil and a redox initiator system of sodium sulfite, introduce nitrogen protection for 20 min, heat to 40 °C, stir to fully emulsify, and at the same time add acrylamide, acrylic acid, sodium styrenesulfonate, anionic monomers, cationic monomers and ammonium persulfate solution, and adjust the pH value of the system to 10 with NaOH solution to obtain a product solution;

[0022] Add absolute ethanol to the product solution to obtain white precipitates, rinse them with water repeatedly 2-3 times and then soak them in absolute ethanol for 24 h to remove unreacted monomers;

[0023] Take out the white precipitates and dry them to constant weight in an oven at 100 °C, and crush them to 20-40 mesh to obtain the copolymer product viscosifier GZN.

[0024] As a preferred embodiment of the present invention, it further includes a preparation method of the lubricant MPA, and the steps are as follows:

[0025] React an alkyl alcohol with a sulfide, and then react the reaction product with an aqueous NaOH solution. Slowly add the resulting reaction product to a chloride solution under stirring, stand, separate, and dry to obtain the lubricant MPA in the form of a bright yellow transparent liquid.

[0026] As a preferred embodiment of the present invention, it further includes a preparation method of the reservoir protection agent, and the steps are as follows:

[0027] Add unsaturated siloxane to hydrochloric acid, and hydrolyze the siloxane at 65 °C to generate polyol-based unsaturated silane; then add a metal ion catalyst and carry out an alcohol group condensation reaction at 70 °C to generate long-chain unsaturated polysiloxane; then add a monomer with a high-temperature protection group and a radical initiator, and carry out an addition reaction at 65 °C to introduce a high-temperature protection group into the side chain; after extraction and purification, the reservoir protection agent is obtained.

[0028] The present invention has the following beneficial effects compared with the prior art:

[0029] The present invention provides a high-temperature and salt-resistant environmental protection mud. In particular, its composition components such as the anti-collapse agent HB-PA-S, the filtration reducer DAADS, the viscosifier GZN, the lubricant MPA, the nano-sealing agent AR / SiO2, and the reservoir protection agent all have the characteristics of high-temperature and salt resistance and environmental protection. This mud can withstand a temperature of up to 220 °C, resist saturated NaCl, and salts with calcium / magnesium ≥ 1.0%, and is pollution-free and easily decomposable;

[0030] The anti-collapse agent HB-PA-S, the filtration reducer DAADS, the viscosifier GZN, the lubricant MPA, the nano-sealing agent AR / SiO2, and the reservoir protection agent provided by the present invention are all beneficial to adsorb on the clay surface and have a sealing property. During the construction process, they can penetrate deep into the soil layer, prevent or delay water from entering the pore spaces of the wellbore rock from the wellbore, and at the same time can increase the bonding force between mineral particles in the rock and improve the surface properties of the soil layer;

[0031] The preparation processes of the anti-collapse agent HB-PA-S, the filtration reducer DAADS, the viscosifier GZN, the lubricant MPA, the nano-sealing agent AR / SiO2, and the reservoir protection agent provided by the present invention are simple and easy to implement. Brief Description of the Drawings

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained according to the provided drawings.

[0033] Figure 1 It is a schematic diagram of the molecular structure of the anti-collapse agent HB-PA-S in Example 1 of the present invention;

[0034] Figure 2 It is a particle size distribution diagram of the anti-collapse agent HB-PA-S in Example 1 of the present invention;

[0035] Figure 3 It is a TGA diagram of the anti-collapse agent HB-PA-S in Example 1 of the present invention;

[0036] Figure 4 It is the filtration loss graph of the plugging fluid system of the anti-collapse agent HB-PA-S in Example 1 of the present invention;

[0037] Figure 5 It is the infrared spectrum diagram of the filtration loss reducer DAADS in Example 2 of the present invention;

[0038] Figure 6 It is the thermogravimetric analysis graph of the filtration loss reducer DAADS in Example 2 of the present invention;

[0039] Figure 7 It is the evaluation result of the filtration loss reduction effect of different filtration loss reducers in the drilling fluid base slurry in Example 2 of the present invention;

[0040] Figure 8 It is the relationship graph between the reaction temperature and the yield of the viscosifier GZN in Example 3 of the present invention;

[0041] Figure 9 It is the infrared spectrum diagram of the viscosifier GZN in Example 3 of the present invention;

[0042] Figure 10 It is the nuclear magnetic resonance hydrogen spectrum of the lubricant MPA in Example 4 of the present invention;

[0043] Figure 11 It is the relationship between the extreme pressure property and the addition amount of organic sulfur in Example 4 of the present invention (modified vegetable oil-based base oil);

[0044] Figure 12 It is the schematic diagram of the molecular structure of the nano-plugging agent AR / SiO2 in Example 5 of the present invention;

[0045] Figure 13 It is the infrared spectrum of the reservoir protection agent in Example 6 of the present invention;

[0046] Figure 14 It is the surface tension measurement chart of the reservoir protection agent under high temperature and alkaline conditions in Example 6 of the present invention;

[0047] Figure 15 It is the physical measurement diagram of the contact angle between the drilling fluid filtrate and the on-site core before adding the reservoir protection agent in Example 6 of the present invention;

[0048] Figure 16 It is the physical measurement diagram of the contact angle between the drilling fluid filtrate and the on-site core after adding a small sample of the reservoir protection agent in Example 6 of the present invention. Detailed implementation manners

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] The present invention provides an environmentally friendly mud suitable for deep coal seams. This mud is used as drilling fluid during the drilling process. The mud contains high-temperature and salt-resistant water-based drilling fluid treatment agents, and the treatment agents are selected from any one or more of a sloughing inhibitor HB-PA-S, a filtration reducer DAADS, a viscosifier GZN, a lubricant MPA, a nano-sealing agent AR / SiO2, and a reservoir protection agent.

[0051] The present invention reveals the internal law between the molecular structure of the drilling fluid treatment agent and the environmental protection performance. Among them, in the molecular structure of the drilling fluid treatment agent, it mainly includes a main chain structure and a branched chain structure; the main chain structure of the treatment agent is a carbon chain structure, and preferably has a benzene ring structure; a branched chain is introduced on the main chain; rigid groups such as "-C-C-", "-C-N-", "-C-S-" are introduced on the main chain or straight chain of the molecule; a cationic group quaternary ammonium group; non-ionic groups amide group, amino group, imino group, carbonyl group; anionic groups sulfonic acid group, carboxylic acid group, lactam group.

[0052] Among them, when the main chain structure of the treatment agent is a carbon chain structure and preferably has a benzene ring structure, the treatment agent has better temperature resistance. Introducing a branched chain on the main chain and increasing the degree of branching of the molecule can increase the movement resistance of the molecule, thereby improving the adsorption stability of the roots at high temperatures. When rigid groups such as "-C-C-", "-C-N-", "-C-S-" are introduced on the main chain or straight chain of the molecule, the energy required to break them is relatively large. For example, the average bond energy of a carbon-carbon bond is 347.3 KJ / mol, and the bond energy is large and uniform. Therefore, introducing groups with greater rigidity can improve the thermal stability of the molecular treatment agent. In addition, the carbon-carbon bond also has high stability in high-temperature and strong alkali environments, is not easily oxidized and hydrolyzed, so under high-temperature conditions, the possibility of the molecular structure being damaged is smaller, and the temperature resistance performance is better.

[0053] Meanwhile, the S-O (π bond) in the sulfonic acid group can enhance the ability to attract electrons from the hydroxyl group, making the sulfonic acid group in a relatively stable state. The -SO3- conjugate system is stable, and when a positive ion enters, the free energy of the system must be increased. Therefore, positive ions are not easily introduced into the hydration layer of the -SO3- conjugate system. The sulfomethyl group has strong hydration ability and can form a relatively thick hydration film. Therefore, when the molecule contains a sulfonic acid group, it has good salt resistance. When there are groups with good hydration performance such as -COOH, -OH, -OCH3, etc. in the molecular structure, they can adsorb on the surface of clay minerals to form a hydration layer, increase the ζ potential of clay particles, enhance the mechanical resistance and electrostatic repulsion of particle coalescence, improve the coalescence stability of clay minerals, and improve the salt resistance ability.

[0054] After mixing the anti-collapse agent HB-PA-S, the filtrate reducer DAADS, the viscosifier GZN, the lubricant MPA, the nano plugging agent AR / SiO2, and the reservoir protection agent, it can withstand a temperature of up to 220 °C, resist saturated NaCl, and salts containing calcium / magnesium ≥ 1.0%, and is pollution-free and easy to decompose.

[0055] The following identifies the components in the mud through multiple examples:

[0056] Example 1: Anti-collapse agent HB-PA-S

[0057] 1. Preparation of anti-collapse agent HB-PA-S

[0058] By grafting hyperbranched polyamide on the surface of nano-silica and modifying the terminal groups with aminoethanesulfonic acid, nano-silica grafted hyperbranched polyamide with sulfonic acid groups as terminal groups is obtained, named HB-PA-S.

[0059] 2. Specific structure

[0060] The molecular structure was characterized by Fourier transform infrared spectrometer (FT-IR); elemental analysis was carried out using X-ray photoelectron spectrometer; particle size analysis of HB-PA-S was carried out using a laser scattering particle size analyzer. It can be seen that the structural formula of HB-PA-S is shown in Figure 1 as follows.

[0061] 3. Particle size analysis of HB-PA-S

[0062] The particle size distribution curve of HB-PA-S is as shown in Figure 2 as follows, and the average particle size of HB-PA-S is 178.4 nm.

[0063] 4. Thermogravimetric test of HB-PA-S

[0064] The thermogravimetric test of HB-PA-S is as shown in Figure 3 as follows. From Figure 3As can be seen from the results shown, the curve of the nano-SiO2 sample continuously and slowly decreases during the process of increasing from 30 °C to 800 °C. The nano-SiO2 is in a state of mass change during this process, with a weight loss of about 17.34%, and the temperature at which the maximum reaction rate is reached is 61.33 °C, indicating that its temperature resistance effect is not ideal.

[0065] For HB-PA-S, the initial thermal decomposition temperature rises to 166.56 °C, and the mass loss therein is about 14.03%. When the temperature is 359.56 °C, the decrease in the TGA curve corresponds to the degradation of the sulfonic acid group, resulting in a mass loss of 41.38%. This indicates that HB-PA-S has excellent thermal stability compared to the nano-SiO2 sample.

[0066] 5. Testing the plugging performance of HB-PA-S

[0067] The synthesized anti-collapse agent was evaluated for its plugging effect by the mud cake simulation evaluation method.

[0068] Anti-collapse agent HB-PA-S with 1%, 3%, and 5% was added to the base slurry respectively, and the HTHP water loss of the system and the plugging effect of the simulated mud cake were measured after hot rolling at 105 °C for 16 h. The results are shown in Figure 4 .

[0069] From Figure 4 it can be seen that the permeability of the mud cake is 4.32×10 -4 mD, which can be used to simulate the shale formation. After adding clear water, the permeability of the mud cake decreases to 4.08×10 -4 mD, and the permeability reduction rate is 5.56%. After adding nanomaterials to the base slurry, the permeability reduction rate has increased significantly. As the dosage of nanomaterials increases, the HTHP water loss of the drilling fluid gradually decreases, and the greater the dosage, the more obvious the effect. When the dosage is 3%, the permeability reduction rate of the mud cake reaches 47.48%, and the permeability at this time is 1.28×10 -5 mD. Therefore, a dosage of 3% was selected.

[0070] During the formation of the mud cake, the plugging agent HB-PA-S enters the small pores of the mud cake relying on its small size and deformability characteristics, thereby reducing the permeability of the mud cake and reducing the water loss.

[0071] 6. Testing the inhibition performance of HB-PA-S

[0072] Shale rolling recovery rate test

[0073] The inhibition performance of the inhibition liquid system of HB-PA-S is shown in Table 1. As can be seen from Table 1, the recovery rate of clear water is relatively low, with the primary recovery rate being 18.5% and the secondary recovery rate being 12.7%. The rolling recovery rate of the drilling fluid system has been greatly improved compared to clear water, and both the primary and secondary recovery rates are higher than 90%. Among them, the primary recovery rate of the 1% polymer solution is 95.8%, and the secondary recovery rate is 93.88%. The rolling recovery rate of the 3% polymer solution system is slightly higher than that of the 1% polymer solution, with the primary and secondary recovery rates being 97.58% and 95.08% respectively. The rolling recovery rate of the 5% polymer solution system is slightly higher than that of the 3% polymer solution, with the primary and secondary recovery rates being 97.72% and 96.66% respectively. In summary, the polyamide nanomaterial HB-PA-S has excellent inhibition performance.

[0074] Table 1

[0075]

[0076] 7. Collapse prevention performance test of HB-PA-S

[0077] Salt resistance performance test

[0078] The mud prepared with 6% bentonite will be used as the base mud. After pre-hydrating for 24 hours, 3% by mass of HB-PA-S is added, and then different mass fractions of NaCl are added. First, it is aged at 180 °C for 16 hours, and then a static filtration loss experiment is carried out at a temperature of 180 °C and a differential pressure of 3.5 MPa. The results obtained are shown in Table 2.

[0079] Table 2

[0080]

[0081]

[0082] As can be seen from the results shown in Table 2, the apparent viscosity, plastic viscosity, dynamic shear force, and filtration loss of the base mud have changed greatly after adding NaCl. The viscosity of the base mud suddenly decreases with the addition of 6% NaCl, and then gradually increases with the addition of 8% NaCl and 10% NaCl. The filtration loss of the base mud suddenly increases with the addition of 6% NaCl, and then gradually increases with the addition of 8% NaCl and 10% NaCl.

[0083] At the optimal temperature of 180 °C for HB-PA-S, when 3% of HB-PA-S and NaCl were added, the apparent viscosity, plastic viscosity, and yield point decreased suddenly with the addition of 6% NaCl, and then gradually increased with the addition of 8% NaCl and 10% NaCl. The fluid loss of the drilling fluid increased suddenly with the addition of 6% NaCl, and then gradually increased with the addition of 8% NaCl and 10% NaCl. However, it can be seen from the increase in the fluid loss relative to the base mud that HB-PA-S still has good fluid loss reduction performance in the saltwater drilling fluid with 10% NaCl, indicating that HB-PA-S has good salt tolerance.

[0084] 8. Environmental performance test of HB-PA-S

[0085] (1) Biodegradability analysis of HB-PA-S anti-collapse agent

[0086] The chemical oxygen demand COD of the HB-PA-S anti-collapse agent was determined by the potassium dichromate method, and the biochemical oxygen demand BOD of the HB-PA-S anti-collapse agent was determined by the dilution and inoculation method. Finally, it was calculated that BOD5 / CODcr of the HB-PA-S anti-collapse agent = 0.6739 > 0.4, indicating that HB-PA-S is easily biodegradable.

[0087] (2) Biological toxicity analysis of HB-PA-S anti-collapse agent

[0088] The biological toxicity of the HB-PA-S anti-collapse agent was determined by the luminescent bacteria method, and it was calculated that EC50 of the HB-PA-S anti-collapse agent > 40000, meeting the national emission standards.

[0089] Thus, in Example 1, in order to improve the temperature and salt resistance and environmental performance of the mud, a modified nano-silica hyperbranched polymer HB-PA-S with a main chain of C-C and C-N bonds and a terminal functional group of sulfonic acid group was added as an anti-collapse agent to the mud. When the dosage of HB-PA-S was 3%, the reduction rate of the mud cake permeability reached 47.48%. 5% of HB-PA-S could increase the compressive strength of the core from 28.9 MPa to 95.5 MPa, improve the compressive strength of the core, and HB-PA-S could enhance the bearing capacity of the shale formation, that is, reduce the increment of the collapse stress of the formation. It showed good temperature and salt resistance in the temperature detection and salt resistance performance detection, and was non-toxic and easily biodegradable, meeting the national environmental protection requirements.

[0090] Example 2: Filtration reducer DAADS

[0091] 1. Preparation:

[0092] Weigh a certain amount of AMPS and dissolve it in tap water. Then, add a certain mass of AM, DMAM, SAS, DMDAAC, and MBA in sequence and continue stirring until completely dissolved. Adjust the pH of the solution with 30% NaOH. Heat up to the set temperature, add the initiator, and react for a period of time under nitrogen protection to obtain a viscous liquid product. Repeatedly purify the obtained product with acetone, and dry and crush it at 103 °C to obtain a powdery fluid loss reducer.

[0093] The optimal synthesis conditions of the high-temperature and high-salt resistant environmentally friendly fluid loss reducer DAADS are shown in Table 3:

[0094] Table 3

[0095]

[0096] 2. Molecular structure

[0097] Use a Fourier transform infrared spectrometer to test the infrared spectrum of the synthesized product. As Figure 5 shown, from Figure 5 it can be seen that: the stretching vibration absorption peak of C-H in the copolymer is at 3442 cm -1 ; the stretching vibration peak of -CH2- in the main chain is at 2929 cm -1 ; the vibration absorption peak of C=O in DMAA and AM is at 1632 cm -1 ; the vibration absorption peak of N-H in the structures of DMAA and DMDAAC is at 1498 cm -1 ; the vibration absorption peak of C-N in DMDAAC and AM is at 1445 cm -1 ; the vibration absorption peaks of -SO3- in AMPS and SAS are at 1220 cm -1 and 1038 cm -1 ; the absorption characteristic peak of N-Cl in the quaternary ammonium group of DMDAAC is at 792 cm -1 ; the absorption peak of C-S in AMPS is at 623 cm -1 .

[0098] 3. Thermogravimetric analysis

[0099] The thermal stability of the synthesized product was studied using a thermogravimetric synchronous analyzer. The results are as Figure 6 . From Figure 6It can be seen that the polymer filtrate reducer experiences a small amount of weight loss before 236°C, which is mainly caused by the volatilization of a small amount of water molecules in the sample. Between 136°C and 267°C, the bound water absorbed by strong hydrophilic groups such as amide groups and sulfonic acid groups in the molecular sample begins to volatilize due to heat. Between 267°C and 336°C, the thermogravimetric curve drops steeply, and this process is due to the decomposition and volatilization of amide groups in the molecular structure. Between 336°C and 473°C, the sulfonic acid groups in the copolymer molecule begin to decompose rapidly, and at the same time, the main chain and side chains of the copolymer molecule also begin to break. This indicates that the polymer filtrate reducer DAADS has good stability before 267°C to 336°C and has good thermal stability.

[0100] 4. Determination of DAADS addition amount

[0101] Add different masses of the polymerization product DAADS to the fresh water base slurry, and measure the rheology, API filtration loss volume, and high temperature and high pressure filtration loss volume before and after aging at 200°C. The experimental results are shown in Table 4.

[0102] Table 4

[0103]

[0104] As can be seen from Table 4, as the addition amount of the filtrate reducer increases, the viscosity of the base slurry gradually increases, and the filtration loss volume gradually decreases. When the addition amount is 2.0%, the apparent viscosity before aging increases from 14.5 mPa·s to 62.75 mPa·s, the API filtration loss volume decreases from 25.2 mL to 4.4 mL, the apparent viscosity after aging increases from 4 mPa·s to 24 mPa·s, the API filtration loss volume decreases from 42 mL to 6.4 mL, and the HTHP filtration loss volume is 25 mL. This shows that the filtrate reducer has good viscosity increasing and filtration loss reducing effects, and good temperature resistance. This is mainly because the molecular chain of the polymerization product contains a large number of hydrophilic groups, which can adsorb on the clay surface to form a dense membrane structure, thereby reducing the filtration loss volume.

[0105] 5. Detection of DAADS temperature resistance

[0106] Add 2% of the polymerization product DAADS to the fresh water base slurry, age it for 16 h at different temperatures, and measure its rheology, API filtration loss volume, and high temperature and high pressure filtration loss volume. The experimental results are shown in Table 5.

[0107] Table 5

[0108]

[0109] As can be seen from Table 5, with the increase of the aging temperature, the viscosity of the base slurry gradually decreases, and the filtration loss gradually increases. However, even after aging at 200 °C, the base slurry still has good rheological properties, and the filtration loss after aging is 6.4 mL, and the high-temperature high-pressure filtration volume is only 25 mL, still maintaining at a relatively low level. This indicates that the synthesized product has good temperature resistance, and the temperature resistance reaches 200 °C. This is because the molecular chain of the polymerization product contains hydrophilic groups such as amide groups and sulfonic acid groups, which can adsorb on the clay surface to form a dense film structure, and the electrostatic interaction between the quaternary amine groups and the clay particles is strong, making the polymer not easy to desorb under high-temperature conditions and can effectively prevent the clay from dehydrating at high temperature. Therefore, the polymer DAADS has good high-temperature resistance.

[0110] 6. Detection of the salt resistance of DAADS

[0111] Add different masses of NaCl to the 2% DAADS / fresh water base slurry, and measure its rheology, API filtration loss and high-temperature high-pressure filtration loss before and after aging. The experimental results are shown in Table 6.

[0112] Table 6

[0113]

[0114]

[0115] As can be seen from Table 6, the viscosity of the base slurry containing 2% polymer filtration reducer gradually decreases with the increase of the NaCl content. This is mainly because the presence of NaCl makes the high-temperature coalescence effect between the copolymer and the clay particles more obvious. The synthesized product has good temperature and salt resistance. Under the condition of 200 °C, the salt resistance ability reaches 15%. Due to the strong rigidity of the product molecular chain, high temperature and inorganic electrolytes enhance the polarity of the solvent water, making the hydrophobic effect of the product correspondingly enhanced, which is beneficial to improving the temperature resistance and salt resistance of the mud product.

[0116] 7. Environmental protection performance test of DAADS

[0117] The environmental protection performance analysis of DAADS, and the experimental results are shown in Table 7

[0118] Table 7

[0119]

[0120] From Table 7 and the structural analysis, it can be seen that the copolymer DAADS has a large molecular weight, and at the same time, sulfonic acid groups are introduced into the molecular chain, making its water solubility and ionization degree increase, fat solubility decrease, toxicity decrease, and it is easy to degrade, thus meeting the environmental protection standards.

[0121] 8. Performance comparison between DAADS and other filtration reducers

[0122] To better verify the performance of the synthesized product, the Driscal filtration reducer was selected, and the filtration loss after aging at 200 °C for 16 h was used as the comparison index for performance comparison. Among them, the Driscal filtration reducer is a commonly used filtration reducer in foreign oilfields. The results are as Figure 7 shown.

[0123] It can be seen from Figure 7 that after aging at 200 °C for 16 h, in the fresh water base mud, the API filtration loss of the base mud with 2% Driscal added is 15.6 mL, and the API filtration loss of the base mud with 2% polymer filtration reducer DAADS added is 6.4 mL, and the filtration loss is about two-fifths of the former.

[0124] In the saturated salt water base mud, the API filtration loss of the base mud with 2% Driscal added is 26.2 mL, and the API filtration loss of the base mud with 2% polymer filtration reducer DAADS added is 15.6 mL, and the filtration loss is about two-fifths of the former.

[0125] In the base mud containing 1% calcium chloride, the API filtration loss of the base mud with 2% Driscal added is 19.6 mL, and the API filtration loss of the base mud with 2% polymer filtration reducer DAADS added is 6.8 mL, and the filtration loss is about two-fifths of the former.

[0126] In the composite salt water base mud, the API filtration loss of the base mud with 2% Driscal added is 24 mL, and the API filtration loss of the base mud with 2% polymer filtration reducer DAADS added is 10.2 mL, and the filtration loss is about one-half of the former. The results show that the copolymerization filtration reducer has significantly better filtration reduction effect in various base muds than the above-mentioned similar products, indicating that the copolymerization filtration reducer DAADS has good high temperature and salt resistance performance.

[0127] Thus, in Example 2, in order to improve the high temperature and salt resistance and environmental protection performance of the mud, the environmentally friendly high temperature and salt resistant filtration reducer DAADS of AM / AMPS / DMDAAC / DMAM / SAS was first synthesized by aqueous solution copolymerization. After adding DAADS to the mud, the synthesized filtration reducer has a high temperature resistance of 200 °C and a salt resistance of 15%. When the dosage of the filtration reducer is 2%, the filtration loss of the base mud after aging at 200 °C for 16 h is 6.4 mL, and the high temperature and high pressure filtration loss is only 25 mL, indicating that the filtration reducer DAADS has good high temperature and salt resistance performance, and its filtration loss after high temperature aging is better than that of the similar treatment agent Driscal. At the same time, the EC 50 of the high temperature and salt resistant filtration reducer DAADS ≥ 30000 ppm, BOD5 / CODCr ≥ 25%, and the environmental protection performance meets the standard. The molecular weight of the filtration reducer is large, and a sulfonic acid group is introduced into the molecular chain, increasing its water solubility and ionization degree, reducing its fat solubility, reducing its toxicity, and being easily degraded, thus meeting the environmental protection standard.

[0128] Example 3: Tackifier GZN

[0129] 1. Preparation of GZN

[0130] (1) Materials and Instruments

[0131] Materials: Acrylic acid, potassium hydroxide, sodium styrene sulfonate (SSS), span 80, deionized water, and white oil are all industrial products. Ammonium persulfate, sodium sulfite, and ethanol are all analytical reagents. The above reagents are all provided by Sinopharm Chemical Reagent Co., Ltd. Cationic monomers and anionic monomers are prepared in the laboratory.

[0132] Instruments: Constant temperature bath CS501, temperature indicating and controlling instrument WMZK - 01, electric mixer speed regulator D40 - 2F, electric mixer D60, rotary vane vacuum pump 2LZ - 2, voltage regulating transformer HCD - 1, AB104 - N type electronic balance, 101A - OD type electrothermal blast drying oven, ZNS type water loss instrument.

[0133] (2) Synthesis Method

[0134] Add span 80, white oil, and sodium sulfite redox initiator system into a four - necked flask equipped with a constant pressure dropping funnel, stirring paddle, thermometer, and condensation reflux device. Introduce nitrogen for protection for 20 min, heat to 40 °C, and stir to fully emulsify. At the same time, add acrylamide, acrylic acid, sodium styrene sulfonate, anionic monomers, cationic monomers, and ammonium persulfate solution with a certain ratio in the feeder. Adjust the pH value to about 10 with NaOH solution.

[0135] Add absolute ethanol to the product solution to obtain white precipitates, and rinse repeatedly 2 - 3 times and then soak in absolute ethanol for 24 h to remove unreacted monomers. After taking out the white precipitates, dry them to constant weight in an oven at 100 °C, and crush them with a pulverizer through 20 - 40 meshes to obtain the copolymer product GZN.

[0136]

[0137] (3) Determination of Optimal Synthesis Conditions

[0138] The experiment uses the L16(45) table, that is, 16 groups of experiments, 5 factors, and 4 levels for each factor for orthogonal test synthesis. Measure the yield and corresponding dynamic - plastic ratio of the synthesized products to screen the optimal synthesis conditions.

[0139] Among them, the molar ratio of acrylamide∶acrylic acid∶sodium styrene sulfonate∶anionic monomer∶cationic monomer is n1∶n2∶n3∶n4∶n5. The polymer synthesis conditions and orthogonal test results are shown in Table 8.

[0140] Table 8

[0141]

[0142]

[0143] When the monomer concentration is 20%, the initiator is 0.5%, the chain transfer agent is 0.05%, and the monomer molar ratio is n1∶n2∶n3∶n4∶n5 = 5∶4∶0.5∶1∶1, three temperatures are selected for comparative experiments, and the synthesized polymer is formulated into a 1% aqueous solution, and the corresponding yield stress-plastic viscosity ratio is calculated. The experimental results are shown in Table 9, Figure 8 As shown, under the condition that other conditions remain unchanged, the higher the reaction temperature, the faster the reaction rate, which conforms to the Arrhenius law of exothermic reactions. However, this reaction is an exothermic reaction. When the reaction starts, heat will be slowly released. If the temperature is too high at this time, it will cause the polymerization reaction to be too fast, the reaction is incomplete, and the yield is relatively low. At the same time, if the reaction temperature is too low, the monomers of free radical polymerization have not fully formed active centers - free radicals, and then the free radicals are not sufficient to fully initiate the monomers, thus blocking the polymerization reaction.

[0144] From Figure 8 it can be seen that when the temperature is 54 °C, the yield is much larger than that at 49 °C or 58 °C. Therefore, it is more appropriate to select the reaction temperature at 54 °C. In addition, it can also be seen from the figure that the polymer conversion rate gradually increases during the period from 0.5 hour to 1.5 hours. As the reaction time prolongs, the influence on the conversion rate is not obvious. Therefore, the optimal reaction time is 2 hours.

[0145] Table 9

[0146]

[0147] 2. Molecular structure

[0148] (1) Molecular weight

[0149] The viscosity of GZN obtained by the Ubbelohde viscometer method is between 700,000 and 1.3 million, meeting the requirements of the molecular structure design of this treatment agent. Adding it to the drilling fluid can appropriately increase the viscosity of the system, but will not increase significantly anymore.

[0150] (2) Infrared spectroscopy (IR) analysis

[0151] The dried polymer (7 # ) was made into a sample with a KBr tablet, and a Nicolet 170SX infrared spectrometer from the United States was used to measure the characteristic absorption peaks of this polymer. The infrared spectrum was obtained Figure 9 .

[0152] The spectral characterization of GZN by IR is as follows: 3433 cm -1 is the absorption peak of -NH; 2934 cm-1 is the stretching absorption peak of -CH3, 1681.97 cm -1 is the stretching vibration absorption peak of -C=O, 1454 cm -1 is the bending vibration absorption peak of -CH2-, 1377 cm -1 is the stretching vibration absorption peak of quaternary ammonium salt -CN bond, 1042 cm -1 is the stretching vibration absorption peak of -SO3-. In addition, it is also found from the figure that there is no vibration absorption peak of C=C of allyl monomer at 1750 - 1640 cm -1

[0153] It is found through infrared spectroscopy characterization that the polymer GZN contains both quaternary ammonium salt cationic groups and sulfate anion groups, and the monomers have fully reacted.

[0154] 3. Performance identification of GZN

[0155] ① Influence of the addition amount of GZN on the performance of fresh - water drilling fluid

[0156] After adding the viscosifier GZN to the fresh - water base mud, its rheological properties and filtration loss reduction properties after aging at room temperature of 25℃ for 16 h and at 200℃ for 16 h were measured, and the results are shown in Table 10.

[0157] Table 10

[0158]

[0159] It can be seen from Table 10 that the apparent viscosity and dynamic shear force of the fresh - water base mud with added GZN increase significantly, and the filtration loss decreases, indicating that GZN has good viscosity - increasing and filtration loss reduction effects; the viscosity and dynamic shear force of the drilling fluid change little before and after hot rolling at 200℃, indicating that GZN has good temperature resistance.

[0160] With the increase of the addition amount of GZN, the apparent viscosity and plastic viscosity of the fresh - water drilling fluid system increase, which is beneficial to reducing the fluidity of the filtrate and increasing the filtration resistance of the filter cake, thus reducing the filtration loss. The dynamic shear force increases with the increase of the GZN concentration, indicating that a network structure is formed in the drilling fluid system, which is beneficial to increasing the viscosity of the drilling fluid system and also helps to reduce the filtration loss; the change of the dynamic shear force after high - temperature aging is small, indicating that a good drilling fluid network structure is maintained in the drilling fluid system, which is beneficial to maintaining the good viscosity - increasing and filtration loss reduction effect of GZN at high temperature.

[0161] 3. Temperature resistance identification of GZN

[0162] After adding GZN to the 15% brine base mud, its rheological properties and filtration loss reduction properties after aging at room temperature of 25℃ and at 200℃ were measured, and the results are shown in Table 11.

[0163] Table 11 ​

[0164]

[0165] As can be seen from Table 11, with the increase of the dosage of GZN, the apparent viscosity, plastic viscosity and dynamic shear force of the drilling fluid increase, and the filtration loss decreases. There is little change in rheology and filtration loss before and after hot rolling at 200 °C. Especially when the dosage of GZN is 1%, the apparent viscosity after high-temperature aging of saturated brine increases from 4.25 mPa·s to 40.5 mPa·s, and the API filtration loss decreases from 220 mL to 8.8 mL, and good viscosity and dynamic shear force are maintained, indicating that GZN has strong viscosity-increasing and filtration-loss-reducing effects and thermal stability in brine-based drilling fluids.

[0166] 4. Detection of the salt resistance performance of GZN and comparison of its performance with other viscosifiers

[0167] In order to further evaluate the viscosity-increasing and filtration-loss-reducing effects of the polymer GZN in 15% salt-based mud, it was compared with the foreign product polymer product Dirscal D, as shown in Table 12.

[0168] Table 12

[0169]

[0170]

[0171] Table 12 shows the temperature resistance performance of GZN and Driscal D in 15% brine-based mud. As can be seen from the table, after adding the filtration-loss reducer, the filtration loss decreases significantly; after aging at 200 °C / 16 h and 220 °C / 16 h, GZN still has good apparent viscosity retention and filtration-loss reduction performance in brine, and the effect is better than that of Driscal D type filtration-loss reducer, indicating that it has good salt resistance performance.

[0172] The viscosity-increasing and filtration-loss-reducing mechanism of the viscosifier GZN in Example 3 is summarized as follows:

[0173] (1) The amide groups in the main chain and the long side chain EO groups of the GZN molecule have multi-point adsorption with clay particles, forming a cross-linked network structure. The formation of this structure will wrap a large amount of free water in the drilling fluid, making it unable to flow freely. On the one hand, it increases the viscosity of the drilling fluid, and on the other hand, it is also beneficial to reduce the filtration loss.

[0174] (2) The sulfonic acid groups in the molecular chain are strong hydrated negative ion groups. Adsorbing on the surface of clay particles thickens the hydration film on its surface, increases the Zeta negative potential of the double electric layer on the clay surface, and the salt has weak dehydration ability for it. That is, in the saturated anti-salt brine-based drilling fluid system, it can still increase the Zeta negative potential of the double electric layer on the surface of clay particles, thereby improving the coagulation stability of clay particles and maintaining the stability of the drilling fluid system.

[0175] (3) In addition to interacting with clay, some polymer particles are dispersed in the system. Due to their comb-shaped conformation and high molecular weight, these free polymer particles can encapsulate more water molecules, reducing the free water molecules in the system and contributing to the increase in the viscosity of the drilling fluid and the decrease in the filtration loss. Additionally, due to the mutual repulsion of these free polymer particles caused by their negative charge, their conformation is relatively extended, which also contributes to the viscosity of the drilling fluid. The presence of free polymer particles is equivalent to increasing the content of colloidal particles in the system, which can plug the pores of the filter cake. The long chains of the free polymer particles wedge into the pores of the filter cake, and the long side chains also have a certain effect of blocking the pores in the filter cake, making the filter cake thin and dense, thereby reducing the filtration loss.

[0176] (4) The thermal decomposition temperature of the viscosifier GZN is about 400 °C, showing excellent thermal stability.

[0177] In summary, in Example 3 of the present invention, after adding the viscosifier GZN to the mud, due to the excellent thermal stability of the viscosifier GZN itself, the strong intermolecular structure formed between it and the clay particles, and the relatively thick double electric layer on the surface of the clay particles, the polymer drilling fluid system maintains good viscosity-increasing and filtration-loss-reducing performance under high-temperature and high-salt conditions.

[0178] To improve the high-temperature and salt resistance of the drilling fluid, in this example, a new comb-shaped temperature- and salt-resistant copolymer GZN is added to the mud. Its thermal degradation temperature is as high as 400 °C. In the NaCl solution, GZN can still maintain a certain comb-shaped structural morphology, indicating its good salt resistance. Different dosages of GZN show good viscosity-increasing and filtration-loss-reducing performance before and after high-temperature aging in fresh water drilling fluid and saturated salt water-based drilling fluid; under the condition of 200 °C saturated salt, its filtration-loss-reducing performance is better than that of DriscalD, and it also has good rheological properties.

[0179] Example 4: Lubricant MPA

[0180] 1. Preparation of Lubricant MPA

[0181] Under appropriate conditions, after the alkyl alcohol reacts with the sulfide and then reacts with the NaOH aqueous solution, the resulting reactant is slowly added to a certain chloride solution under stirring, and then left standing, separated, and dried to obtain a bright yellow transparent liquid.

[0182] Among them, to meet the environmental protection requirements, the base oil for preparing the extreme pressure and anti-wear lubricant for water-based drilling fluid uses vegetable oil that has no environmental toxicity and side effects and is easily biodegradable. At the same time, to avoid the saponification or esterification reaction of vegetable oil in the high-temperature and alkaline drilling operation environment, which affects the stability of vegetable oil, the vegetable oil is subjected to a catalytic reaction at 200 °C to form modified vegetable oil.

[0183] This embodiment is optimized and formulated by adding components such as modified vegetable oil, anionic surfactant, non-ionic surfactant, fatty acid, and self-made organic sulfur extreme pressure and anti-wear agent. The product is a yellow transparent liquid.

[0184] 2. Molecular Structure

[0185] (1) 1H NMR Analysis

[0186] The extreme pressure and anti-wear agent sample uses deuterated chloroform CDCl3 as the solvent and tetramethylsilane as the internal standard. The 1H NMR spectrum has the following absorption peaks (see Figure 10 ).

[0187] From Figure 10 it can be seen that the chemical shift of the solvent is 7.26, and the chemical shifts of the characteristic peaks of the extreme pressure and anti-wear lubricant MPA sample are distributed in the range of 1-2, in the high field region, proving that the extreme pressure and anti-wear agent belongs to saturated alkanes and does not contain unsaturated alkanes, aromatic compounds, etc. Therefore, the extreme pressure and anti-wear lubricant MPA has low fluorescence or no fluorescence.

[0188] (2) Organic Element Analysis

[0189] The VarioELcube model elemental analyzer is used to analyze the elements of the extreme pressure and anti-wear agent. The element types and the contents of each element are shown in Table 13.

[0190] Table 13

[0191]

[0192] It can be seen from the table that the main elements of the extreme pressure and anti-wear agent are C, S, H, and N, among which the S element content is as high as 35.49%, and the N element content is 2.59%. Since the extreme pressure and anti-wear additive contains active elements such as S and N at the same time, it can effectively improve the extreme pressure, anti-wear, and friction reduction performance of the base oil.

[0193] 3. Evaluation of the Anti-wear Performance of Lubricant MPA

[0194] The MRS-10A four-ball friction testing machine is used to measure the extreme pressure of the synthesized organic sulfur sample. The sintering load of the modified vegetable oil is 1525 N, indicating that the molecules in the modified vegetable oil can form an adsorption film on the metal surface, but can only withstand a load below 1525 N; after adding 0.5%, 1.0%, 2.0%, and 3.0% of the organic sulfur sample to the modified vegetable oil, its sintering load increases with the increase of the additive dosage, increasing to 2510 N, 3182 N, 4015 N, and 4956 N respectively. The experimental results are shown in Figure 11 .

[0195] The experimental results show that the organic sulfur sample has good extreme pressure and anti-wear properties. When the dosage is 2%, its seizure load is as high as 4015 N. It is recommended that when preparing lubricants, the dosage of this sulfur-based extreme pressure and anti-wear agent should be no less than 2%.

[0196] During the test, after the oil film formed by the medium molecules in the modified vegetable oil ruptured, direct metal-to-metal contact occurred, generating a large amount of heat, which caused the decomposition of the organic sulfur additive. Reactive sulfur with higher activity was produced and chemically reacted with the metal surface to form a chemical reaction film such as iron sulfide with low melting point and easy shearing, preventing direct metal-to-metal contact. When the concentration of the organic sulfur additive in the modified vegetable oil is low, the speed of forming the chemical reaction film is slow and the quantity is small, so the load it can bear is light. As the dosage of the organic sulfur sample in the modified vegetable oil increases, the seizure load increases, indicating that the formed reaction film has a strong load-bearing capacity.

[0197] 4. Lubrication performance evaluation of lubricant MPA

[0198] Prepare a 4% bentonite base slurry, add 1 wt% lubricant, and after hot rolling at 180 °C for 16 h, test the extreme pressure lubrication coefficients of different systems. The test results are shown in Table 14.

[0199] Table 14

[0200]

[0201] It can be seen from the test results of adding 1% of different lubricants to the 4% bentonite base slurry in the above table that after the developed extreme pressure lubricant MPA is added to the base slurry, its extreme pressure lubrication coefficient is less than 0.1, and the percentage of reduction in the lubrication coefficient is similar to that of the foreign UltraFree product.

[0202] To further evaluate the lubrication performance of MPA, 1% of different lubricants were added to the following water-based drilling fluid systems for comparative evaluation. The test results are shown in Table 15.

[0203] Table 15

[0204]

[0205] Drilling fluid system:

[0206] 2% bentonite slurry + 0.2 sodium carbonate + 0.2% NaOH + 1% SP-8 + 10% NaCl + 0.5% FA367 + 2% SIAT (density 1.2 g / cm 3 )

[0207] The evaluation results of the lubrication effect after adding 1% of different lubricants to the above drilling fluid system show that the developed MPA has the best lubrication effect, good compatibility with the treatment agents in the drilling fluid system, and can be completely dispersed in the system. Among them, the foreign UltraFree product has poor compatibility in this system, and its reduction of the lubrication effect of the system is not very obvious.

[0208] In terms of foaming property, when the two products of lubricant MPA and UltraFree are added to the base slurry or drilling fluid system, there is no foaming situation whether at normal temperature or after hot rolling, while the other three lubricants have foaming to varying degrees.

[0209] 5. Influence of the addition of MPA on the properties of drilling fluid

[0210] Compare the drilling fluid properties of two groups of drilling fluid systems with different densities before and after adding MPA, and the test results are shown in Table 16.

[0211] Table 16

[0212]

[0213] Formula 1#:

[0214] 2%Bentonite + 0.4%NaOH + 0.8%DR-1 + 0.3%PAC-LV + 3%HCOOK + 0.3%EM P + 1%SIAT + Barite

[0215] Formula 2#: Formula 10# + 2%MPA

[0216] Formula 3#: 2%Bentonite + 0.4%NaOH + 0.8%DR-1 + 0.3%PAC-LV + 3%KCl + 0.3%FA367 + Barite

[0217] Formula 4#: Formula 3# + 2%MPA

[0218] From the test results of the properties, it can be seen that after adding MPA to the two groups of drilling fluid systems with different densities, the API filtration loss and HTHP filtration loss decrease, and the initial filtrate outflow time is significantly delayed. The addition of MPA improves the filtration reduction performance of the original drilling fluid system. Analyzing the reason, it is that MPA can be dispersed into nano / micro emulsions in the water-based system, which can effectively block the nano / micro pores and cracks of the mud cake, improve the quality of the mud cake, and the formed mud cake is more dense and delicate. Therefore, adding MPA to the system can significantly reduce the filtration loss of the system.

[0219] Similarly, after adding MPA to the two groups of drilling fluid systems with different densities, their extreme pressure lubrication coefficients are significantly reduced, indicating that MPA has strong lubricity, can significantly enhance the lubrication effect of the water-based drilling fluid system, and play a good role in lubrication and drag reduction.

[0220] As can be seen from the above, this embodiment provides an organic sulfur type extreme pressure and anti-wear lubricant MPA with a sulfur content as high as 35.49%. The nuclear magnetic resonance 1H spectrum analysis shows that the synthesized organic sulfide belongs to saturated alkanes. The organic sulfur type extreme pressure and anti-wear lubricant MPA has good extreme pressure and anti-wear properties. When preparing the lubricant for drilling fluid, the addition amount of this organic sulfur type extreme pressure and anti-wear agent is not less than 2%; and this lubricant has good compatibility, can be completely dispersed in fresh water or water-based drilling fluid system, can optimize the performance of water-based drilling fluid, has excellent lubrication performance, simultaneously improves the filtration loss reduction performance of the original drilling fluid system, and has a small fluorescence intensity, showing good environmental protection performance.

[0221] Example 5: Nano-sealing agent AR / SiO2

[0222] 1. Preparation of nano-sealing agent AR / SiO2

[0223] (1) Preparation of acrylic resin nano-silica composite material (AR / SiO2)

[0224] Use semi-continuous emulsion polymerization method to prepare acrylic nano-emulsion. The first step: add 32.5 g of St, 16 g of MMA, 1 g of AA, 0.5 g of HEMA and 2.5 g of modified silica into a 250 ml beaker; the second step, dissolve 0.34 g of OP-10 and 0.17 g of SDBS in 20 ml of distilled water, then add it to the monomer mixture in the first step, and shear and emulsify for 5 min to form a pre-emulsion; the third step, add 15 ml of 2 wt% PVA solution and one-fourth volume of the pre-emulsion into a 250 ml four-necked round-bottom flask; the fourth step, protect with nitrogen, set the stirring speed at 300 r / min, immerse the flask in a water bath at 71 °C for 10 minutes, and then quickly raise the water bath temperature to 81 °C; the fifth step, use two dropping funnels to separately drip the remaining three-fourths of the pre-emulsion and 15 ml of 1 wt% KPS into the flask, and finish dripping in about two hours; the sixth step, continue to react for 1 hour, cool to 40 °C, and then add 25 wt% ammonia water to adjust the pH to 7.

[0225] (2) Preparation of the solid powder of the sealing agent

[0226] Wash the above emulsion with ethanol and deionized water successively, and continuously centrifuge at a set speed of 10000 r / min. Finally, dry the washed sample at 105 °C to obtain pure and dry powder, that is, the above nano-sealing agent AR / SiO2.

[0227] 2. Molecular structure

[0228] The molecular structure of the nano-sealing agent AR / SiO2 is shown in Figure 12 as follows.

[0229] 3. Detection of the high-temperature resistance performance of the nano-sealing agent AR / SiO2

[0230] The nano-sealing agent was added to the bentonite slurry, and its filtration loss under aging at 200 °C for 16 h was tested to evaluate its high-temperature resistance performance. The experimental results are shown in Table 17.

[0231] Table 17

[0232]

[0233] As can be seen from Table 17 above, when the nano-sealing agent was added to the bentonite slurry, there was a significant decrease in the filtration loss before and after addition, indicating that the sealing agent played a role in sealing the micro-cracks and pores in the filter cake, effectively preventing the further invasion of the drilling fluid into the sealing medium, and further proving that the nano-sealing agent has good high-temperature stability and a high-temperature resistance ability of 200 °C.

[0234] 4. Detection of the salt resistance performance of the nano-sealing agent AR / SiO2

[0235] The concentration of DG1 was 3%, the time was 30 min, the pressure was 3.5 MPa, and the temperature was 110 °C. In the experiment, the salinity was adjusted by NaCl, and the added NaCl was 1#-0, 2#-5%, 3#-10%, 4#-15%, and 5#-20% respectively. The specific experimental test results are shown in Table 18 below.

[0236] Table 18

[0237]

[0238] As can be seen from Table 4.34 above, when the NaCl concentration was 5%, the reduction rate of permeability increased slightly, indicating that the addition of a small amount of NaCl promoted the sealing effect. The reason is that when the NaCl solution concentration was at a certain level, due to the existence of the common ion effect and osmotic hydration effect, the hydration dispersion, swelling, and migration ability of the formation shale were reduced, thereby reducing the entry of substances in the drilling fluid into the sealing medium. After that, as the NaCl concentration gradually increased, because there were hydrophobic chains in the polymer and the hydrophobic chains were less sensitive to salt, the polymer could maintain the stability of the particle size at a certain salinity and was not prone to agglomeration, so it could achieve the sealing of the filter cake at a certain salinity.

[0239] 5. Detection of the environmental protection performance of the nano-sealing agent AR / SiO2

[0240] The experimental results of the toxicity and biodegradability of different concentrations of the sealing agent are shown in Table 19.

[0241] Table 19

[0242]

[0243] As can be seen from Table 19, for the nano-sealing agent with a concentration of 1-3%, the EC 50 is greater than 30000 ppm, indicating that the nano-sealing agent is non-toxic. The BOD5 / COD Cr is greater than 25%, belonging to easily degradable materials.

[0244] The high-temperature resistant nano-sealing agent AR / SiO2 with a core-shell structure provided in this embodiment has an average particle size of 98 nanometers, a glass transition temperature of 109.1 °C. AR / SiO2 can resist high temperatures of 200 °C, the salt resistance is greater than 15%, and the plugging rate > 90%; the mechanism of plugging shale pores is determined by its particle size at the nano level, the rigid core-flexible shell structure, and hydrogen bond interaction. This material can effectively improve the plugging efficiency and reduce the invasion of filtrate into shale. At the same time, the addition of AR / SiO2 can improve the quality of the filter cake, thereby reducing the filtration loss of water-based drilling fluids, and it is non-toxic and easily degradable.

[0245] Example 6: Reservoir protection agent

[0246] 1. Preparation of reservoir protection agent

[0247] (1) In 10 parts of unsaturated siloxane, 0.2 parts of hydrochloric acid is added as a catalyst, and the siloxane undergoes a hydrolysis reaction at 65 °C to form polyol-based unsaturated silane.

[0248] (2) 0.1 part of metal ion catalyst is added, and an alcohol group condensation reaction occurs at 70 °C to form long-chain unsaturated polysiloxane.

[0249] (3) Then 1 part of monomer with a high-temperature protection group and 0.2 part of free radical initiator are added, and an addition reaction occurs at 65 °C to introduce a high-temperature protection group into the side chain and improve the temperature resistance of the reaction product.

[0250] (4) Finally, through extraction and purification, an environmentally friendly high-temperature resistant and liquid-lock preventing reservoir protection agent can be obtained.

[0251] 2. Molecular structure

[0252] The sample is prepared by the KBr tablet pressing method and characterized by infrared spectroscopy. In the Figure 13 shown infrared spectrum diagram, the stretching vibration peaks of C-F bonds (1245 cm -1 , 1210 cm -1 , 1150 cm -1 ), the rocking vibration absorption peaks of -CF2 (705 cm -1 , 657 cm -1 ), the characteristic absorption peak of Si-H (2150 cm -1 ), and the characteristic absorption peak of Si-CH3 (1267 cm -1), the absorption peak of asymmetric stretching vibration of Si-O (1010 - 1123 cm -1 ).

[0253] It can be seen that the reservoir protection agent has a branched structure and contains temperature-resistant sulfonic acid groups and Si-C.

[0254] 3. Performance Detection of Reservoir Protection Agent

[0255] (1) Surface Tension Detection

[0256] The pH of the water-blocking agent was adjusted to 9 - 10 with a 10% NaOH solution and aged at 200°C for 16 h. The surface tension of the sample was measured. After aging at 200°C, γ of the aqueous solution < 25 mN / m, and γ of the filtrate of the base mud after aging at 200°C < 25 mN / m. Figure 14 It shows that the environmentally friendly high-temperature resistant and liquid-lock preventing reservoir protection agent has a low surface tension in high-temperature alkaline drilling fluids, can resist temperatures above 150°C, has good water dispersibility, and can reach 25 mN / m when the dosage is greater than 0.10%.

[0257] (2) Improvement Ability of Oligomeric Organosilicon on the Contact Angle between the Filtrate of Water-Based Drilling Fluid and Rock

[0258] The core was soaked in a solution at 200°C and pH = 9 - 10 for 16 h, dried at 200°C, and cooled to room temperature. The contact angle was calculated by the five-point fitting method. The experimental results show that the contact angle between the water-based drilling fluid and the rock is 26.71° - 36.35°, with an average of 31.41°. After adding the indoor synthesized sample of the environmentally friendly high-temperature resistant and liquid-lock preventing reservoir protection agent, the contact angle is 105.95° - 108.53°. After adding the industrially scaled-up sample, the contact angle is 125.59°. The contact angle measurement results are shown in Figure 15 and Figure 16 . The results show that adding the water-blocking agent can increase the contact angle between the filtrate of the drilling fluid and the rock surface. The increase in the contact angle reduces the flow resistance during the backflow process of the filtrate of the drilling fluid, helps to improve the backflow rate of the filtrate of the drilling fluid, and reduces the water-lock damage of the drilling fluid to the reservoir.

[0259] (3) Improvement of the Contact Angle between the Filtrate of Oil-Based Drilling Fluid and Rock by Oligomeric Organosilicon

[0260] The core was immersed in diesel or a solution of diesel + 0.2% oligomeric organosilicon at 200 °C for 16 h, dried at 200 °C and cooled to room temperature, and the contact angle was calculated by the five-point fitting method. The experimental results show that the contact angles of the oil-based drilling fluid with the rock immersed in diesel and the rock immersed in the diesel + 0.2% oligomeric organosilicon solution are both close to 0°. The contact angle between distilled water and the rock immersed in diesel is 101.7°, and the contact angle between distilled water and the rock immersed in the diesel + 0.2% oligomeric organosilicon solution is 92.0°. The contact angle measurement results indicate that after adding the water-blocking inhibitor, the oil-wetting degree of the oil-wet surface can be reduced, the rock interface can be changed from oil-wetting to gas-wetting (intermediate wetting), the purpose of making the rock interface water-oil repellent can be achieved, the phase trapping damage caused by the oil-based drilling fluid and the subsequent water-based reservoir stimulation fluid can be reduced, and the gas reservoir productivity can be protected to the greatest extent.

[0261] (4) Evaluation of reservoir protection performance

[0262] In formation water, the water saturation of the core reached 72% after 25 minutes of spontaneous imbibition, and the final water saturation was 83%. After treating the core with 0.2% liquid-blocking inhibitor, the core was spontaneously imbibed for 60 minutes, the water saturation reached 66%, and the final water saturation was 71%. The environmental protection liquid-blocking inhibitor can reduce the imbibition rate and decrease the spontaneous imbibition water saturation of the core by 14.45%, which is beneficial to reducing the degree of reservoir phase trapping damage.

[0263] After sufficient backflow under a certain pressure condition, the irreducible water saturation of the untreated core was 40%. After treating the core with 0.2% liquid-blocking inhibitor, the irreducible water saturation of the core was 31%, a decrease of 22.5%, which proves that the environmental protection liquid-blocking inhibitor can significantly improve the relative permeability of oil and gas resources in the reservoir and is beneficial to reducing the degree of reservoir phase trapping damage.

[0264] After the core spontaneously imbibed formation water, after backflow at 0.03 MPa, the permeability recovery value was 54%. After backflow at 0.06 MPa, the permeability recovery value was 63%. After adding 0.2% liquid-blocking inhibitor to the core during spontaneous imbibition, after backflow at 0.03 MPa, the permeability recovery value was 77%. After backflow at 0.06 MPa, the permeability recovery value was 91%. The permeability recovery value increased by 36.5%, which proves that the environmental protection liquid-blocking inhibitor can significantly improve the relative permeability of oil and gas resources in the reservoir and improve productivity.

[0265] Example 6 provided by the present invention can resist temperatures above 200°C. When the dosage is 0.3%, the surface tension can be reduced to 20 mN / m. After the environmentally friendly high-temperature resistant and liquid-lock preventing reservoir protection agent modifies the core surface, the contact angle between the rock and the aqueous phase can be maintained in a neutral wetting state of 90 - 110°. At the same time, through its ultra-low interfacial tension and surface modification ability, the self-imbibed water saturation of the core can be decreased by 14.45%, the irreducible water saturation can be decreased by 22.5%, and the permeability recovery value can reach 91%. It can effectively reduce the liquid-phase trapping damage caused by the wellbore working fluid to the reservoir, significantly improve the relative permeability of oil and gas resources in the reservoir, and increase the production capacity.

[0266] In the above Examples 1 - 6, the fluid loss reducer: can resist temperatures of 200°C, resist salts of 15%, and the fluid loss at high temperature and high pressure is 25 mL; the shale stabilizer: can resist temperatures of 200°C, resist salts of 15%, and the shale stabilizing time (complete disintegration time) is 24 h; the viscosifier: can resist temperatures of 200°C, resist salts of 15%, and the apparent viscosity after hot rolling is 32 mPa·S; the inhibitor: can resist temperatures of 200°C, resist salts of 15%, and the inhibition rate is 92%; the lubricant: can resist temperatures of 200°C, resist salts of 15%, and the extreme pressure lubrication coefficient is 0.0649; the plugging agent: can resist temperatures of 200°C, resist salts of 15%, and the plugging efficiency is 90%; the reservoir protection agent: can resist temperatures of 200°C, resist salts of 15%, and the reservoir permeability recovery value is 91%.

[0267] The above examples are only exemplary examples of the present application and are not used to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions within the essence and protection scope of the present application, and such modifications or equivalent substitutions should also be regarded as falling within the protection scope of the present application.

Claims

1. An environmentally friendly mud suitable for deep coal seams, including an anti-collapse agent HB-PA-S, a fluid loss reducer DAADS, a viscosity enhancer GZN, a lubricant MPA, a nano plugging agent AR / SiO2, and a reservoir protective agent; in, The anti-collapse agent HB-PA-S is a modified nano-silica hyperbranched polymer with CC and CN bonds as the main chain and a sulfonic acid group as the terminal functional group. The structural formula of the anti-collapse agent HB-PA-S is shown in FIG1 ; The fluid loss reducer DAADS is a polymer containing CC, CN, CS bonds in the main chain and functional groups such as carbonyl, imino, sulfonic acid, and quaternary ammonium groups; The tackifier GZN is a polymer having an amide group in the main chain, an EO group in the long side chain, and a sulfonic acid functional group; The lubricant MPA is a saturated alkane with an S element content of up to 35.49% and an N element content of up to 2.59%; The molecular structure formula of the nano plugging agent AR / SiO2 is shown in FIG12 ; The reservoir protective agent is a polymer with a branched structure and containing temperature-resistant sulfonic acid groups, Si-C and other groups.

2. The environmentally friendly mud suitable for deep coal seams according to claim 1, characterized in that: Calculated by mass percentage, the content of the anti-collapse agent HB-PA-S is 1.0-5.0%; the content of the filtration reducer DAADS is 1.0-3.0%; the content of the viscosity enhancer GZN is 0.1-1.0%; the content of the lubricant MPA is 2.0-3.0%; the content of the nano plugging agent AR / SiO2 is 1.0-3.0%; and the content of the reservoir protection agent is 0.1-0.5%.

3. A method for preparing an environmentally friendly mud suitable for deep coal seams, used for preparing the environmentally friendly mud suitable for deep coal seams as claimed in any one of claims 1 to 2, characterized in that: The steps include: The anti-collapse agent HB-PA-S, the filtrate reducer DAADS, the viscosity enhancer GZN, the lubricant MPA, the nano plugging agent AR / SiO2 and the reservoir protective agent are added into water and mixed evenly to obtain the environmentally friendly mud.

4. The method for preparing environmentally friendly mud suitable for deep coal seams according to claim 3, characterized in that: The invention also includes a preparation method of the anti-collapse agent HB-PA-S, the steps of which are as follows: Grafting hyperbranched polyamide on the surface of nano-silicon dioxide to obtain a product; The terminal group of the product is modified with aminoethanesulfonic acid to obtain the anti-collapse agent HB-PA-S.

5. The method for preparing environmentally friendly mud suitable for deep coal seams according to claim 3, characterized in that: It also includes a method for preparing the fluid loss reducer DAADS, the steps of which are as follows: Weigh AMPS and dissolve it in water, then add AM, DMAM, SAS, DMDAAC, and MBA in sequence, and stir until completely dissolved to obtain a mixed solution; The pH of the mixed solution is adjusted with 30% NaOH, the mixed solution is heated to a set temperature, an initiator is added, and the mixture is reacted under nitrogen protection to obtain a viscous liquid product; The liquid product is repeatedly purified with acetone, and dried and crushed at 103° C. to obtain a powdered fluid loss reducer DAADS.

6. The method for preparing environmentally friendly mud suitable for deep coal seams according to claim 3, characterized in that: It also includes a preparation method of the tackifier GZN, the steps are as follows: Span 80, white oil and sodium sulfite redox initiator system were mixed, nitrogen was introduced for protection for 20 minutes, heated to 40°C, stirred and fully emulsified, acrylamide, acrylic acid, sodium styrene sulfonate, anionic monomer, cationic monomer and ammonium persulfate solution were added at the same time, and the pH value of the system was adjusted to 10 with NaOH solution to obtain a product solution; Anhydrous ethanol was added to the product solution to obtain a white precipitate, which was repeatedly washed with water for 2-3 times and then immersed in anhydrous ethanol for 24 hours to remove unreacted monomers; The white precipitate was taken out and dried in an oven at 100° C. to constant weight, and then crushed into 20-40 meshes to obtain the copolymer product tackifier GZN.

7. The method for preparing environmentally friendly mud suitable for deep coal seams according to claim 3, characterized in that: It also includes a method for preparing the lubricant MPA, the steps of which are as follows: The alkyl alcohol is reacted with the sulfide, and the reactants are then reacted with a NaOH aqueous solution. The generated reactants are slowly added to a chloride solution under stirring, allowed to stand, separated, and dried to obtain the lubricant MPA in a bright yellow transparent liquid state.

8. The method for preparing environmentally friendly mud suitable for deep coal seams according to claim 3, characterized in that: It also includes a preparation method of the reservoir protective agent, the steps of which are as follows: Unsaturated siloxane is added to hydrochloric acid, and the siloxane is hydrolyzed at 65°C to generate polyol-based unsaturated silane; a metal ion catalyst is then added to generate an alcohol condensation reaction at 70°C to generate a long-chain unsaturated polysiloxane; a monomer with a high-temperature protection group and a free radical initiator are then added to generate an addition reaction at 65°C to introduce a high-temperature resistant protection group into the side chain; and the reservoir protective agent is obtained through extraction and purification.

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