Filtrate reducer for water-based drilling fluid as well as preparation method and application of filtrate reducer

Abstract

The invention relates to a filtrate reducer for water-based drilling fluid as well as a preparation method and application of the filtrate reducer. The filtrate reducer is formed by polymerizing N, N-diethyl acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, dimethyl diallyl ammonium chloride, N-vinyl caprolactam and allyl alcohol polyoxyethylene ether, can effectively reduce water loss in fresh water drilling fluid, saline water drilling fluid and saturated saline water drilling fluid, and has small influence on rheological properties of the drilling fluid; and the drilling fluid can resist 2% of divalent salt in a drilling fluid basic system, is particularly suitable for high-temperature deep wells and ultra-deep wells, and can meet the requirements of the drilling fluid for the high-temperature deep wells and ultra-deep wells.

Description

Technical Field

[0001] The present application relates to the technical field of drilling fluid treatment agents for petroleum exploration and development, and in particular to a fluid loss reducer for water-based drilling fluid, a preparation method thereof, and an application thereof. Background Art

[0002] Deep formations have the characteristics of high temperature, high pressure and complex geological conditions, which put forward higher requirements on the performance and maintenance of drilling fluids. Temperature resistance and salt resistance have become huge challenges for drilling fluids. Drilling fluid treatment agents will undergo high-temperature degradation, cross-linking, desorption and other effects at high temperatures, resulting in a serious decline in the performance of drilling fluids. The failure of drilling fluids can easily lead to serious safety accidents such as stuck pipe, leakage, and blowout, increase drilling costs, damage oil and gas reservoirs, and have a significant impact on deep oil and gas development. Oil-based drilling fluids have been proven to be the preferred drilling fluids for deep and ultra-deep wells due to their excellent thermal stability, salt resistance and lubricity. However, oil-based drilling fluids have the disadvantages of high drilling costs and high risks. Therefore, in order to overcome the adverse effects of high temperature and salt pollution on the performance of deep and ultra-deep well drilling fluids, it is imperative to develop new high-temperature and salt-resistant fluid loss reducers. Although existing fluid loss reducers have good high-temperature resistance, they have poor salt resistance and cannot adapt to salt-saturated environments. Summary of the invention

[0003] The present application provides a fluid loss reducer for water-based drilling fluid and a preparation method and application thereof, so as to solve the problem of failure of the fluid loss reducer in a high-temperature salt-saturated environment in the related art.

[0004] Based on the above findings, this application provides the following technical solutions:

[0005] In a first aspect, the present application provides a fluid loss reducer for water-based drilling fluid, having the following structural formula:

[0006]

[0007] Among them, m is 60-90, n is 30-60, x is 30-45, y is 23-30, z is 1-3, k is 10-60, and the weight average molecular weight of the fluid loss reducer is 2.34×10 5 ~5.76×10 5 .

[0008] In a second aspect, the present application provides a method for preparing a fluid loss reducer for water-based drilling fluid, comprising a free radical micelle polymerization step, in which the following monomers are polymerized in an aqueous solution: N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, N-vinyl caprolactam, allyl alcohol polyoxyethylene ether, an initiator, and an inorganic base; wherein the molar ratio of the N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, and N-vinyl caprolactam monomers is (4-6): (2-4): (2-3): (1.5-2), and the allyl alcohol polyoxyethylene ether is 0.5 mol% to 2 mol% of the total monomer amount.

[0009] In combination with the second aspect of the present application, in some embodiments, the free radical micelle polymerization step includes: dissolving 2-acrylamido-2-methylpropanesulfonic acid in water and adjusting the pH to neutral or alkaline; then adding N,N-diethylacrylamide, dimethyldiallylammonium chloride, N-vinyl caprolactam, and allyl alcohol polyoxyethylene ether in sequence, mixing evenly and heating, then adding an initiator, reacting under anaerobic conditions, and purifying to obtain a fluid loss reducer for water-based drilling fluid.

[0010] In conjunction with the second aspect of the present application, in some embodiments, the temperature of the free radical micelle polymerization step is 55-68°C.

[0011] In conjunction with the second aspect of the present application, in some embodiments, the total concentration of the monomers is 30 wt%±2 wt%, and the concentration of the initiator is 0.6 wt%±0.02 wt%. Preferably, the initiator is azobisisobutyronitrile.

[0012] In conjunction with the second aspect of the present application, in some embodiments, the pH of the aqueous solution is 7 to 10, and the polymerization reaction time is 4 to 6 hours.

[0013] In a third aspect, the present application provides the application of the above-mentioned fluid loss reducer for water-based drilling fluid in the field of water-based drilling fluid.

[0014] In a fourth aspect, the present application provides a water-based drilling fluid, comprising the above-mentioned filtrate reducer for water-based drilling fluid.

[0015] In conjunction with the fourth aspect of the present application, in some embodiments, the water-based drilling fluid also includes: 0wt% to 36wt% NaCl, and / or, 1wt% to 3wt% CaCl2.

[0016] In conjunction with the fourth aspect of the present application, in some embodiments, the water-based drilling fluid further comprises one or more of bentonite, a flow pattern regulator, a high-temperature plugging agent, a lubricant, potassium chloride, nano-silica, and barite.

[0017] Compared with the prior art, this application has at least the following beneficial effects:

[0018] (1) The N,N-diethylacrylamide in the fluid loss reducer molecule provided by the present application contains a carbon-carbon double bond and an amide group, which is easy to undergo polymerization reaction to form a hydrolysis-resistant, high-performance polymer. Under the promotion of the two ethyl groups, a hyperconjugated system is formed between nitrogen, carbonyl and double bonds, which has good thermal stability; the strong anionic sulfonic acid group has good temperature resistance, salt resistance and divalent ion tolerance, and the amide group makes it hydrolytically stable; the quaternary ammonium salt provides a cationic group with strong and stable adsorption capacity, which copolymerizes to form a strong and stable five-membered cyclic intramolecular bond, enhances the rigidity of the molecular chain, and improves the temperature resistance; the introduction of a new type of temperature-resistant group lactam ring, with strong hydrophilicity, can be adsorbed on the surface of clay particles to form a thick and tough hydration film, thereby reducing the fluid loss; the present application also introduces a side chain macromolecular alcohol polyoxyethylene ether monomer to give full play to its steric hindrance and further improve the fluid loss reduction effect.

[0019] (2) The fluid loss reducer provided in the present application has a main chain in which the quaternary ammonium cationic group and the nonionic amide group have strong adsorption and hydration properties, the sulfonic acid group has good temperature and salt resistance, the seven-membered lactam ring and the generated five-membered ring improve the rigidity of the molecule; the comb-like polymer of the macromolecular side chain can significantly improve the fluidity and fluid loss reduction of the cement slurry by inducing better steric hindrance, the multi-functional groups synergistically enhance the effect, the temperature resistance is high in a saturated salt environment, and the fluid loss reduction effect is obvious.

[0020] (3) The water-based drilling fluid provided by the present application can resist salt to salt saturation at 220°C, and the effect is better than the existing similar water-based drilling fluid. The fluid loss reducer of the present application can effectively reduce water loss in freshwater drilling fluid, salt water drilling fluid and saturated salt water drilling fluid, and has little effect on the rheological properties of the drilling fluid, and can resist 2% divalent salt in the drilling fluid base system, and is particularly suitable for high-temperature deep wells and ultra-deep wells, and can meet the needs of high-temperature deep wells and ultra-deep wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 : Schematic diagram of the preparation of the filtrate reducer of the embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0024] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unclearly recorded range; and any lower limit can be combined with other lower limits to form an unclearly recorded range. Similarly, any upper limit can be combined with any other upper limit to form an unclearly recorded range. In addition, although not clearly recorded, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unclearly recorded range.

[0025] It should be noted that, in the description of the present application, unless otherwise specified, "above", "below" are inclusive numbers, and the meaning of "multiple" in "one or more" is two or more. Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also includes other elements that are not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0026] In the description of the present application, the description with reference to the terms "any embodiment / method", "one embodiment / method", "some embodiments / methods", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment / method or example are included in at least one embodiment / method or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment / method or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments / methods or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments / methods or examples described in this specification and the features of the different embodiments / methods or examples, unless they are contradictory.

[0027] In this application, according to the provisions of GB / T 16783.1-2014 "Field Testing of Drilling Fluids in the Petroleum and Natural Gas Industry Part 1: Water-Based Drilling Fluids" and the American Petroleum Institute (API) (APIRP13B1, 2009) standard, the test methods for the following terms are:

[0028] API filtration loss measurement: API filtration loss meter was used to collect the filtrate of drilling fluid seepage for 30 minutes under low temperature (room temperature) and low pressure (AP = 0.69 MPa) to obtain the API filtration loss of drilling fluid (FL API ), unit is mL.

[0029] High-temperature and high-pressure filtration loss: refers to the filtration loss of drilling fluid under specific high temperature and high pressure. After the drilling fluid is aged, the high-temperature and high-pressure filtration loss (FL) of the drilling fluid is measured under high temperature (set temperature) and high pressure (set pressure) conditions using a high-temperature and high-pressure filtration loss instrument. HTHP ), the test time is 30 minutes, and the final filtration loss is 30 minutes multiplied by 2, in mL.

[0030] Apparent viscosity: also known as effective viscosity or apparent viscosity, it is the ratio of shear stress to velocity gradient of drilling fluid under a certain velocity gradient, expressed as "AV" and the unit is mPa·s (milliPascal second).

[0031] Plastic viscosity: When the drilling fluid is in laminar flow, the sum of various internal frictions between solid particles, between solid particles and liquid molecules, and between liquid molecules in the drilling fluid is called the plastic viscosity of the drilling fluid, expressed as "PV", and the unit is m Pa·s (milliPascal·second) or cP (centipoise), 1m Pa·s=lcP.

[0032] Dynamic shear stress: The dynamic shear stress of drilling fluid reflects the magnitude of the interaction force between clay particles and polymer molecules when the drilling fluid is in laminar flow, that is, the strength of the network structure formed inside the drilling fluid. It is expressed as "YP" or "T" and the unit is Pa (Pascal).

[0033] in:

[0034] AV=1 / 2×Φ 600

[0035] PV=Φ 600 -Φ 300

[0036] YP=1 / 2×(Φ 300 -PV)

[0037] Drilling fluid aging treatment: The drilling fluid samples were subjected to aging treatment at temperatures of 180°C, 200°C, and 220°C for 16 hours.

[0038] Performance test after aging: After aging, cool to room temperature, stir at 10000-12000r / min for 30min, and measure the filtration loss.

[0039] The above invention summary of the present application is not intended to describe each disclosed embodiment or each implementation in the present application. The following description more specifically illustrates exemplary embodiments. These embodiments can be used in various combinations. In each example, the enumeration is only used as a representative group and should not be interpreted as exhaustive.

[0040] Fluid loss reducer:

[0041] The fluid loss reducer for water-based drilling fluid provided in the present application has the following structural formula:

[0042]

[0043] Among them, m is 60-90, n is 30-60, x is 30-45, y is 23-30, z is 1-3, k is 10-60, and the weight average molecular weight of the fluid loss reducer is 2.34×10 5 ~5.76×10 5 .

[0044] Preparation method:

[0045] The method for preparing a fluid loss reducer for water-based drilling fluid provided in the present application comprises a free radical micelle polymerization step, in which the following monomers are polymerized in an aqueous solution: N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, N-vinyl caprolactam, allyl alcohol polyoxyethylene ether, an initiator, and an inorganic base; wherein the molar ratio of the monomers of N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, and N-vinyl caprolactam is (4-6): (2-4): (2-3): (1.5-2), and the allyl alcohol polyoxyethylene ether accounts for 0.5 mol% to 2 mol% of the total amount of the monomers.

[0046] In some embodiments, the free radical micelle polymerization step includes: dissolving 2-acrylamido-2-methylpropanesulfonic acid in water and adjusting the pH to neutral or alkaline; then adding N,N-diethylacrylamide, dimethyldiallyl ammonium chloride, N-vinyl caprolactam, and allyl alcohol polyoxyethylene ether in sequence, mixing evenly and heating, then adding an initiator, reacting under anaerobic conditions, and purifying to obtain a fluid loss reducer for water-based drilling fluid.

[0047] In some embodiments, the total concentration of the monomers is 30 wt %±2 wt %, and the concentration of the initiator is 0.6 wt %±0.02 wt %.

[0048] In some embodiments, the pH of the aqueous solution is 7 to 10, and the polymerization reaction time is 4 to 6 hours.

[0049] In some embodiments, after purification, the mixture is dried under vacuum at 80° C. for 24 h.

[0050] application:

[0051] The above-mentioned fluid loss reducer is suitable for preparing water-based drilling fluid. The present application provides a water-based drilling fluid, including the above-mentioned fluid loss reducer for water-based drilling fluid.

[0052] In some embodiments, the water-based drilling fluid further includes: 0wt% to 36wt% NaCl, and / or, 1wt% to 3wt% CaCl2.

[0053] In some embodiments of the present application, the water-based drilling fluid further comprises one or more of bentonite, a flow pattern regulator, a high-temperature plugging agent, a lubricant, potassium chloride, nano-silicon dioxide, and barite.

[0054] The water-based drilling fluid is suitable for drilling construction in high-temperature and high-salt environments, especially in saturated salt environments with a temperature of 220°C.

[0055] Example

[0056] The technical solution of the present application is described in detail below through examples. If the manufacturer's brand or preparation method is not specified, the raw materials, equipment or solvents used are all common raw materials, equipment or solvents on the market. Unless otherwise specified, the raw materials of the same name used in the following examples and comparative examples are the same raw materials. Flow type regulator, high temperature plugging agent, and barite were purchased from PetroChina Engineering Technology Research Institute, Huaian soil was purchased from Xinyuan Chemical (bentonite) Co., Ltd., Huaian County, Hebei Province, lubricants, nano-silicon dioxide sodium chloride were purchased from Shandong Deshunyuan, and monovalent / divalent salts were purchased from Sinopharm Group.

[0057] The method for preparing a fluid loss reducer in this embodiment comprises the following steps:

[0058] Embodiment 1:

[0059] 9.60 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 7 with a 20 mol / L NaOH solution; 11.79 g of N,N-diethylacrylamide, 7.55 g of dimethyldiallylammonium chloride, 4.84 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 60° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A1.

[0060] Embodiment 2:

[0061] 11.70 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 8 with a 20 mol / L NaOH solution; 11.97 g of N,N-diethylacrylamide, 6.09 g of dimethyldiallylammonium chloride, 5.24 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 65° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A2.

[0062] Embodiment 3:

[0063] 9.39 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 9 with a 20 mol / L NaOH solution; 11.52 g of N, N-diethylacrylamide, 4.88 g of dimethyldiallylammonium chloride, 4.20 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 60° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A3.

[0064] Embodiment 4:

[0065] 14.11 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 9 with a 20 mol / L NaOH solution; 8.66 g of N,N-diethylacrylamide, 5.50 g of dimethyldiallylammonium chloride, 4.74 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 55° C., an initiator was added, and the reaction was continued for 6 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A4.

[0066] Embodiment 5:

[0067] 13.44 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 7 with a 20 mol / L NaOH solution; 10.31 g of N,N-diethylacrylamide, 7.86 g of dimethyldiallylammonium chloride, 3.39 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, then heated to 60° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A5.

[0068] Embodiment 6:

[0069] 7.97 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 8 with a 20 mol / L NaOH solution; 14.67 g of N, N-diethylacrylamide, 9.33 g of dimethyldiallylammonium chloride, 4.01 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 65° C., an initiator was added, and the reaction was continued for 4 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer A6.

[0070] Comparative Example 1:

[0071] 20.85 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 7 with a 20 mol / L NaOH solution; 6.39 g of N,N-diethylacrylamide, 5.42 g of dimethyldiallylammonium chloride, 2.33 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, then heated to 60° C., an initiator was added, and the reaction was continued for 4 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer B1.

[0072] Comparative Example 2:

[0073] 8.64 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 8 with a 20 mol / L NaOH solution; 7.07 g of N,N-diethylacrylamide, 13.48 g of dimethyldiallylammonium chloride, 5.80 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, then heated to 55° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer B2.

[0074] Comparative Example 3:

[0075] 16.02 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 9 with a 20 mol / L NaOH solution; 9.83 g of N,N-diethylacrylamide, 4.99 g of dimethyldiallylammonium chloride, 2.15 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, and then heated to 60° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer B3.

[0076] Comparative Example 4:

[0077] 9.60 g of 2-acrylamide-2-methylpropanesulfonic acid monomer was weighed and dissolved in deionized water, and the pH of the solution was adjusted to 11 with a 20 mol / L NaOH solution; 11.79 g of N,N-diethylacrylamide, 7.55 g of dimethyldiallylammonium chloride, 4.84 g of N-vinylcaprolactam, and 1 mol% of allyl alcohol polyoxyethylene ether were added to the solution in sequence, and the mixture was poured into a three-necked flask after being stirred evenly, and stirred for 30 min at 30° C. under nitrogen, then heated to 65° C., an initiator was added, and the reaction was continued for 5 h; after the reaction was completed, the mixture was washed, precipitated, and filtered with anhydrous ethanol-acetone, and vacuum dried at 80° C. for 24 h and then crushed to obtain a filtrate reducer B4.

[0078] Verification Example 1: Drilling Fluid Preparation

[0079] Preparation of base slurry: Slowly add 16 g of bentonite and 0.56 g of sodium carbonate into 400 mL of distilled water, stir thoroughly, and age at room temperature for 24 hours to prepare base slurry.

[0080] Preparation of freshwater drilling fluid: Add filtrate reducer to 400 mL of base slurry and stir at 10,000-12,000 r / min for 20 min to obtain freshwater drilling fluid.

[0081] Brine drilling fluid: add 0-36wt% NaCl to 400mL base slurry, add 4g filtrate reducer after complete dissolution, stir at 10000-12000r / min for 20min to obtain brine drilling fluid.

[0082] Drilling fluid basic system: 2% base slurry + 1.5% fluid loss reducer + 2% flow pattern regulator + 3% KCl + 2% high temperature plugging agent + 2% nano calcium carbonate + 3% lubricant + barite.

[0083] Verification Example 2: Evaluation of the Effect of Fluid Loss Reducer

[0084] The fluid loss reducers prepared in the examples and comparative examples were added into the base slurry at 2 wt % to obtain freshwater drilling fluid. The API fluid loss results of the freshwater drilling fluid before and after aging are shown in Table 1.

[0085] Table 1

[0086]

[0087] According to the experimental results, the filtrate reducer prepared in the embodiment of the present application has a good filtrate reduction effect. After the prepared freshwater drilling fluid is aged at 180°C for 16 hours, the API filtration loss is less than 5mL; while the filtrate reducer prepared in the comparative example shows a poor filtrate reduction effect. The API filtration loss of the prepared freshwater drilling fluid after aging is greater than 12mL.

[0088] Verification Example 3: Temperature resistance test of fluid loss reducer

[0089] This verification example is represented by the fluid loss reducer A2 prepared in Example 2 of the present application, which is added to the base slurry at an addition amount of 1wt% to prepare a freshwater drilling fluid to evaluate the temperature resistance of the fluid loss reducer prepared in the present application. The rheological and fluid loss test results of the freshwater drilling fluid before and after aging are shown in Table 2.

[0090] Table 2

[0091]

[0092]

[0093] As shown in Table 2, the freshwater drilling fluid still maintains a good fluid loss reduction effect after aging at 220°C. This is because the amide group and strong anionic sulfonic acid group contained in the polymer molecule have excellent temperature resistance. At the same time, the copolymerization produces a stable five-membered cyclic internal bond to enhance the rigidity of the molecular chain, and the synergistic effect further improves the temperature resistance; the cationic group and the lactam ring have strong and stable adsorption capacity, which adsorb on the surface of clay particles to form a thick and tough hydration film, reducing the fluid loss amount, and the side chain macromolecular monomer fully exerts its steric hindrance to further improve the fluid loss reduction effect.

[0094] Verification Example 4: Test on Salt Resistance of Fluid Loss Reducer

[0095] This verification example is represented by the fluid loss reducer A2 prepared in Example 2 of the present application, which is added to the base slurry at an addition amount of 1wt%, and a certain amount of sodium chloride is added to prepare a brine drilling fluid to evaluate the temperature and salt resistance of the fluid loss reducer prepared in the present application. The rheological and fluid loss test results of the brine drilling fluid before and after aging are shown in Table 3.

[0096] Table 3

[0097]

[0098]

[0099] As shown in Table 3, the brine drilling fluid still maintains a good filtration reduction effect after aging at 220°C. With the increase of salt concentration, the apparent viscosity of the drilling fluid shows a downward trend, and the apparent viscosity is still >20mPa·s when it is saturated with salt; the API filtration loss shows an upward trend with the increase of salt concentration, which is because the addition of salt will destroy the filtration reduction effect of the polymer, but the filtration loss in the saturated salt environment is <10mL.

[0100] In summary, the fluid loss reducer prepared in the examples of the present application has excellent resistance to saturated salt. This is because the polymer molecules contain strong anionic sulfonic acid groups, which improve salt resistance and divalent ion tolerance; the polymer contains quaternary ammonium cationic groups and anionic sulfonic acid groups at the same time, and the presence of zwitterions makes it have salt response characteristics. With the addition of electrolyte salts, the molecular chains stretch and the fluid mechanical size increases, forming a regular and dense spatial network structure, which further improves the salt resistance and fluid loss reduction effect.

[0101] Verification Example 5: Compatibility Test of Fluid Loss Control Agent System

[0102] This verification example is represented by the fluid loss reducer A2 prepared in Example 2 of the present application, and a drilling fluid base system is prepared at an addition amount of 1wt% to evaluate the temperature resistance, saturated salt resistance, and 2wt% divalent salt resistance of the fluid loss reducer prepared in the present application. The rheological and fluid loss test results of the drilling fluid base system before and after aging are shown in Table 4.

[0103] Table 4

[0104]

[0105]

[0106] The experimental results show that the fluid loss reducer prepared in the embodiment of the present application has good compatibility in the basic system of drilling fluid, and has good effects of resistance to temperature, resistance to saturated salt, and resistance to 2wt% divalent salt, and has broad application prospects.

[0107] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A fluid loss reducer for water-based drilling fluid, characterized in that: It has the following structural formula: Among them, m is 60-90, n is 30-60, x is 30-45, y is 23-30, z is 1-3, k is 10-60, and the weight average molecular weight of the fluid loss reducer is 2.34×10 5 ~5.76×10 5 .

2. A method for preparing the fluid loss reducer for water-based drilling fluid according to claim 1, characterized in that: The invention comprises a free radical micelle polymerization step, in which the following monomers are polymerized in an aqueous solution: N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride, N-vinyl caprolactam, allyl alcohol polyoxyethylene ether, an initiator and an inorganic base; wherein the molar ratio of the monomers of N,N-diethylacrylamide, 2-acrylamide-2-methylpropanesulfonic acid, dimethyldiallyl ammonium chloride and N-vinyl caprolactam is (4-6): (2-4): (2-3): (1.5-2), and the allyl alcohol polyoxyethylene ether accounts for 0.5 mol% to 2 mol% of the total amount of the monomers.

3. The method for preparing a fluid loss reducer for water-based drilling fluid according to claim 2, characterized in that: The free radical micelle polymerization step comprises: dissolving 2-acrylamido-2-methylpropanesulfonic acid in water, adjusting the pH to neutral or alkaline; then sequentially adding N,N-diethylacrylamide, dimethyldiallyl ammonium chloride, N-vinyl caprolactam, and allyl alcohol polyoxyethylene ether, mixing evenly, heating, adding an initiator, reacting under anaerobic conditions, purifying, and obtaining a fluid loss reducer for water-based drilling fluid.

4. The method for preparing a fluid loss reducer for water-based drilling fluid according to claim 2, characterized in that: The temperature of the free radical micelle polymerization step is 55-68°C.

5. The method for preparing a fluid loss reducer for water-based drilling fluid according to claim 2, characterized in that: The total monomer concentration is 30 wt%±2 wt%, and the initiator concentration is 0.6 wt%±0.02 wt%.

6. The method for preparing a fluid loss reducer for water-based drilling fluid according to claim 2, characterized in that: The pH of the aqueous solution is 7 to 10, and the polymerization reaction time is 4 to 6 hours.

7. Use of the fluid loss reducer for water-based drilling fluid according to claim 1 in the field of water-based drilling fluid.

8. A water-based drilling fluid, comprising the fluid loss reducer for water-based drilling fluid according to claim 1.

9. The water-based drilling fluid according to claim 8, characterized in that: The water-based drilling fluid also includes: 0wt% to 36wt% NaCl, and / or, 1wt% to 3wt% CaCl2.

10. The water-based drilling fluid according to claim 8, characterized in that: The water-based drilling fluid further comprises one or more of bentonite, a flow pattern regulator, a high-temperature plugging agent, a lubricant, potassium chloride, nano-silicon dioxide, and barite.

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