Filtrate reducer as well as preparation method and application thereof

Abstract

The invention relates to a filtrate reducer as well as a preparation method and application thereof. The filtrate reducer is prepared from the following raw materials: a combination of a polymeric monomer and a cross-linking agent, the polymeric monomer comprises a combination of alkenyl amide, alkenyl sulfonic acid, a rigid monomer and an alkenyl cationic monomer; the cross-linking agent has a structure as shown in a formula I; according to the invention, the raw materials for preparing the filtrate reducer are designed, so that the obtained filtrate reducer has high temperature resistance and salt resistance, also has better rheological property and filtrate reduction property, and can meet the requirements of technical development of high-temperature-resistant and salt-resistant drilling fluids.

Description

Technical Field

[0001] The invention belongs to the technical field of oilfield chemical industry, and in particular relates to a fluid loss reducer and a preparation method and application thereof. Background Art

[0002] As my country's energy demand continues to rise, its dependence on foreign oil continues to increase, and the energy situation is severe, deep and ultra-deep oil and gas have become the focus of development. As an important part of drilling engineering, the performance of drilling fluid directly affects the drilling cost and drilling cycle of deep and ultra-deep wells. At present, the bottom temperature of deep wells in my country can reach above 200°C. There are also many salt-containing formations in deep formations. The high temperature and high salt environment of deep wells can easily lead to the deterioration of drilling fluid performance, making it difficult to meet the needs of safe drilling. Therefore, temperature-resistant and salt-resistant drilling fluid is a key technology for deep formation drilling, and it plays an irreplaceable and important role in the exploration and development of deep and ultra-deep oil and gas resources.

[0003] During the drilling process, the intrusion of drilling fluid filtrate into the formation will cause hydration and expansion of shale, resulting in reservoir damage and even complicated downhole accidents such as wellbore instability. Among them, fluid loss reducers are the core treatment agents to ensure the stability of drilling fluid performance. The action mechanism of fluid loss reducers is generally as follows: (1) The fluid loss reducer is adsorbed on the surface of clay particles to prevent clay particles from flocculating and turn clay into fine particles, which is conducive to the formation of a denser mud cake and reduces water loss; (2) The hydration group of the fluid loss reducer can thicken the hydration film of clay particles and reduce the permeability of the mud cake; (3) The fine particles of the fluid loss reducer can enter the gaps of the mud cake, block the microporous cracks of the mud cake, and make the mud cake thin and dense; (4) The fluid loss reducer can appropriately increase the viscosity of the drilling fluid, making it difficult for the filtrate to penetrate through the mud cake and reducing the permeability.

[0004] At present, the main type of high temperature resistant fluid loss reducers is synthetic polymer fluid loss reducers. The related products have certain temperature and salt resistance. However, with the development of deep well drilling, the actual bottom hole working temperature continues to rise, and the probability of encountering complex formations increases, resulting in unsatisfactory performance of fluid loss reducers in deep well drilling. Its temperature and salt resistance still cannot meet the actual needs. Therefore, it is very urgent to develop new polymer fluid loss reducers with better performance. Traditional polymer fluid loss reducers are generally based on 2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS), N-vinyl pyrrolidone (NVP) and other monomers, and are prepared by aqueous solution polymerization. These polymers are all linear polymers with limited high temperature resistance, and have the disadvantages of high viscosity and easy chain scission at high temperature. They have weak anti-degradation ability and are difficult to meet the requirements of drilling fluid rheology and fluid loss control under high temperature and high salt conditions in deep wells. Therefore, polymer fluid loss reducers with non-linear branched and cross-linked structures have gradually become a research hotspot.

[0005] CN114773539A discloses a high temperature and high salt resistant micro-crosslinked hydrophobic associating viscosity increasing and fluid loss reducing agent for water-based drilling fluid and a preparation method thereof; the viscosity increasing and fluid loss reducing agent is prepared by copolymerizing a comonomer, a crosslinking agent, a cosolvent and an initiator in water; the comonomer includes a vinyl monomer, sodium styrene sulfonate, maleic anhydride and a long hydrophobic chain ester monomer; the fluid loss reducing agent effectively reduces the drilling fluid loss, increases the drilling fluid viscosity and maintains the rheological stability of the drilling fluid under high temperature and high salt conditions, and can be applied to oil and gas drilling in deep high-salt formations.

[0006] CN111285964A discloses a temperature-resistant and salt-resistant micro-crosslinked fluid loss reducer for drilling fluid and a preparation method thereof. The micro-crosslinked fluid loss reducer is generated by reaction using an appropriate amount of a crosslinking agent and a chain transfer agent. The micro-crosslinked fluid loss reducer has the following advantages: it contains a crosslinked microsphere structure and can effectively reduce the fluid loss of drilling fluid; it contains a variety of temperature-resistant and adsorbent groups and has excellent temperature and salt resistance; and it has a low molecular weight and has little effect on the rheological properties of the drilling fluid.

[0007] CN116063623A discloses a method for preparing a hyperbranched polymer for drilling fluid, wherein an organic acid monomer, an organic amide monomer, a first branching agent, a second branching agent and a chain transfer agent are copolymerized under the action of a pH regulator and a chain transfer agent to obtain a hyperbranched polymer for drilling fluid; the invention provides a reversible addition fragmentation chain transfer (RAFT) polymerization method, which adopts a rapid polymerization process, uses diene monomers, a branching agent and a chain transfer agent, and prepares a water-soluble snowflake-shaped hyperbranched polymer fluid loss reducer at a high polymerization rate and high conversion in an aqueous solution system, wherein the water-soluble snowflake-shaped hyperbranched polymer fluid loss reducer has a double-layer branched structure, good solubility, high rheology, no cross-linking, a large number of branched end groups, a narrow molecular weight distribution, good temperature resistance, and a low viscosity effect.

[0008] The prior art generally prepares nonlinear fluid loss reducers by introducing functional monomers into fluid loss reducer molecules or using cross-linking agents. In order to avoid excessive viscosity-increasing effect of fluid loss reducers, additives or chain transfer agents are often used in the polymerization process, and the preparation process is complicated and the cost is high. Therefore, it is necessary to design the raw materials for preparing fluid loss reducers, so as to obtain fluid loss reducers for high temperature and salt water-resistant drilling fluids with micro-cross-linked structures but without affecting the viscosity effect of fluid loss reducers through simple preparation raw materials, so as to meet the needs of the current development of high temperature and salt-resistant drilling fluid technology. Summary of the invention

[0009] In view of the deficiencies in the prior art, the object of the present invention is to provide a fluid loss reducer and a preparation method and application thereof. The present invention designs the raw materials for preparing the fluid loss reducer so that the obtained fluid loss reducer has high temperature resistance and salt resistance, and at the same time has good rheological properties and fluid loss reduction performance, which can meet the needs of the development of high temperature and salt resistance drilling fluid technology.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a fluid loss reducer, wherein the raw materials for preparing the fluid loss reducer include a combination of a polymerizable monomer and a cross-linking agent; the polymerizable monomer includes a combination of alkenyl amide, alkenyl sulfonic acid, a rigid monomer and an alkenyl cationic monomer; and the cross-linking agent has a structure as shown in Formula I:

[0012]

[0013] Wherein, R1, R2, and R3 are each independently selected from any one of C2-C6 straight-chain alkylene groups.

[0014] The fluid loss reducer provided by the present invention is an ultra-high temperature and salt resistant low gel polymer fluid loss reducer, which has excellent high temperature and salt resistance, simple preparation raw materials, is suitable for deep well and ultra-deep well drilling, and can effectively improve the rheological properties of slurry and reduce fluid loss during use.

[0015] The fluid loss reducer provided by the present invention is a micro-crosslinked copolymer prepared by four organic monomers, namely alkenyl amide, alkenyl sulfonic acid, rigid monomer and alkenyl cationic monomer, and a water-soluble acrylamide crosslinking agent having a structure shown in Formula I; the rigid monomer can not only improve the adsorption capacity with clay, but also improve the temperature resistance of the fluid loss reducer; the sulfonic acid group of the alkenyl sulfonic acid can play a good hydration role, so that the fluid loss reducer has a good salt resistance and enhances the dispersion stability of clay; the alkenyl cationic monomer can produce a strong adsorption effect with clay, not only can adsorb clay, but also can improve the salt resistance of the fluid loss reducer; the micro-crosslinked structure formed by the water-soluble acrylamide crosslinking agent significantly improves the rigidity of the fluid loss reducer, improves the temperature and salt resistance of the fluid loss reducer, and at the same time ensures the fluidity of the molecular chain of the fluid loss reducer.

[0016] In the present invention, the C2-C6 may be C3, C4, or C5.

[0017] The C2-C6 straight-chain alkylene group includes ethylene, propylene, butylene, n-pentylene or n-hexylene.

[0018] In the present invention, the cross-linking agent can be purchased. For example, the cross-linking agent N-[tris(3-acrylamidepropylmethylether)methyl]acrylamide can be purchased from FUJIFILM Wako.

[0019] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.

[0020] As a preferred technical solution, the alkenyl amide includes any one of acrylamide, N,N-dimethylacrylamide or N,N-diethylacrylamide, or a combination of at least two thereof.

[0021] Preferably, the olefin sulfonic acid comprises 2-acrylamido-2-methyl-1-propane sulfonic acid.

[0022] Preferably, the rigid monomer includes any one of N-vinyl pyrrolidone, N-vinyl caprolactam or N-acryloylmorpholine or a combination of at least two thereof; the heterocyclic group contained in the rigid monomer can not only improve the adsorption capacity with clay, but also the larger steric hindrance can further improve the temperature resistance of the fluid loss reducer.

[0023] Preferably, the alkenyl cationic monomer includes dimethyldiallyl ammonium chloride and / or dodecyldimethylallyl ammonium chloride; the quaternary ammonium salt cationic group contained in the alkenyl cationic monomer can produce a strong adsorption effect with clay, which can not only adsorb clay but also improve the salt resistance of the fluid loss reducer.

[0024] Preferably, the molar ratio of the alkenyl amide to the alkenyl sulfonic acid is (2-4):1, for example, it can be 2.1:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 3.9:1, etc.

[0025] Preferably, the molar ratio of the alkenyl amide to the rigid monomer is (3-8):1, for example, 3.1:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, 4.2:1, 4.4:1, 4.6:1, 4.8:1, 5:1, 5.2:1, 5.4:1, 5.6:1, 5.8:1, 6:1, 6.2:1, 6.4:1, 6.6:1, 6.8:1, 7:1, 7.2:1, 7.4:1, 7.6:1, 7.8:1, etc.

[0026] Preferably, the molar ratio of the alkenyl amide to the alkenyl cationic monomer is (6-16):1, for example, 6.2:1, 6.5:1, 6.8:1, 7:1, 7.2:1, 7.5:1, 7.8:1, 8:1, 8.2:1, 8.5:1, 8.8:1, 9:1, 9.2:1, 9.5:1, 9.8:1, 10:1, 10.2:1, 10.5:1, 1 0.8:1, 11:1, 11.2:1, 11.5:1, 11.8:1, 12:1, 12.2:1, 12.5:1, 12.8:1, 13:1, 13.2:1, 13.5:1, 13.8:1, 14:1, 14.2:1, 14.5:1, 14.8:1, 15:1, 15.2:1, 15.5:1, 15.8:1, 16:1, etc.

[0027] Preferably, the cross-linking agent comprises N-[tris(3-acrylamidopropylmethylether)methyl]acrylamide and / or N-[tris(4-acrylamidobutylmethylether)methyl]acrylamide.

[0028] Preferably, the mass ratio of the polymerized monomer to the cross-linking agent is (100-400):1, for example, it can be 120:1, 140:1, 160:1, 180:1, 200:1, 220:1, 240:1, 260:1, 280:1, 300:1, 320:1, 340:1, 360:1, 380:1, etc.

[0029] Preferably, the raw materials for preparing the fluid loss reducer also include an initiator.

[0030] Preferably, the initiator includes any one of a persulfate initiator, a redox initiator or an azo initiator, or a combination of at least two of them.

[0031] Preferably, the persulfate initiator includes potassium persulfate and / or ammonium persulfate.

[0032] Preferably, the redox initiator comprises ammonium persulfate-sodium bisulfite.

[0033] Preferably, the azo initiator includes azobisisobutyronitrile and / or azobisisobutylimidazoline hydrochloride.

[0034] Preferably, the mass ratio of the polymerization monomer to the initiator is (100-300):1, for example, it can be 120:1, 140:1, 160:1, 180:1, 200:1, 220:1, 240:1, 260:1, 280:1, 300:1, etc.

[0035] Preferably, the raw materials for preparing the fluid loss reducer also include a neutralizer.

[0036] Preferably, the neutralizing agent comprises sodium hydroxide.

[0037] Preferably, the raw material for preparing the fluid loss reducer also includes water.

[0038] Preferably, the mass percentage of the polymerized monomer in the raw material for preparing the fluid loss reducer is 15-30%, for example, it can be 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 19.5%, 20%, 20.5%, 21%, 21.5%, 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5% and the like.

[0039] Preferably, the weight average molecular weight of the fluid loss reducer is 260,000-400,000, for example, 260,000, 270,000, 280,000, 290,000, 300,000, 310,000, 320,000, 330,000, 340,000, 350,000, 360,000, 370,000, 380,000, 390,000, 400,000, etc.

[0040] In a second aspect, the present invention provides a method for preparing the fluid loss reducer as described in the first aspect, the preparation method comprising:

[0041] The filtrate reducer is obtained by reacting olefinic amide, olefinic sulfonic acid, rigid monomer, olefinic cationic monomer and crosslinking agent.

[0042] The fluid loss reducer provided by the invention is prepared by free radical copolymerization, and the preparation method is simple and the cost is low.

[0043] Preferably, the olefin sulfonic acid is used in the form of an olefin sulfonic acid aqueous solution.

[0044] Preferably, the aqueous olefin sulfonic acid solution is neutralized to neutrality using a neutralizer before use.

[0045] Preferably, the neutralizing agent is used in the form of an aqueous neutralizing agent solution.

[0046] Preferably, the mass percentage of the neutralizer in the neutralizer aqueous solution is 40-60%, for example, it can be 42%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, etc.

[0047] Preferably, the alkenyl cationic monomer is used in the form of an alkenyl cationic monomer aqueous solution.

[0048] Preferably, the mass percentage of the alkenyl cationic monomer in the aqueous solution of the alkenyl cationic monomer is 50-60%, for example, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, etc.

[0049] Preferably, the crosslinking agent is used in the form of an aqueous crosslinking agent solution.

[0050] Preferably, the mass percentage of the crosslinking agent in the crosslinking agent aqueous solution is 1-2%, for example, it can be 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, etc.

[0051] Preferably, the reaction is carried out in the presence of an initiator.

[0052] Preferably, the reaction temperature is 40-60°C, for example, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc.

[0053] Preferably, the reaction time is 2-4 h, for example, it can be 2 h, 2.2 h, 2.4 h, 2.6 h, 2.8 h, 3 h, 3.2 h, 3.4 h, 3.6 h, 3.8 h, 4 h, etc.

[0054] Preferably, the reaction is carried out under a nitrogen atmosphere.

[0055] Preferably, after the reaction is completed, the steps of washing, drying and crushing are further performed in sequence.

[0056] Preferably, the preparation method specifically comprises the following steps:

[0057] (1) neutralizing the olefin sulfonic acid aqueous solution with a neutralizing agent aqueous solution until it is neutral;

[0058] (2) mixing the solution obtained in step (1), alkenyl amide, rigid monomer, and aqueous solution of alkenyl cationic monomer to obtain a mixed solution;

[0059] (3) The mixed solution, the crosslinking agent aqueous solution and the initiator react to obtain the fluid loss reducer.

[0060] In a third aspect, the present invention provides a drilling fluid, the components of which include the fluid loss reducer as described in the first aspect.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] (1) The rigid monomer used in the present invention has good chemical stability and strong resistance to temperature and salt. The alkenyl cationic monomer can still maintain its adsorption effect on clay even at high temperatures, thus preventing the clay from precipitating and condensing at high temperatures;

[0063] (2) The cross-linking agent used in the present invention is a water-soluble acrylamide cross-linking agent. The micro-cross-linked structure formed significantly improves the rigidity of the fluid loss reducer and improves its temperature and salt resistance. The cross-linked structure can also achieve the physical plugging and fluid loss reduction effect of the fluid loss reducer;

[0064] (3) Compared with commonly used diene-based crosslinking agents (such as N,N-methylenebisacrylamide, etc.), the crosslinking agent used in the present invention has more vinyl groups on each molecule, more crosslinking points per unit space scale, and the crosslinked network structure formed by the reaction is more stable;

[0065] (4) The cross-linking agent used in the present invention has a relatively long molecular branch chain, which can form a cross-linked network structure while still ensuring the fluidity of the fluid loss reducer molecular chain and avoiding excessive viscosity increase of the drilling fluid;

[0066] (5) The fluid loss reducer provided by the present invention has good rheological properties, temperature and salt resistance, and especially good fluid loss reduction performance; the freshwater test slurry using the fluid loss reducer provided by the present invention is aged at 240°C for 16 hours, and the FL of the freshwater test slurry is API The FL of the brine test slurry is 6-15.2 mL, the apparent viscosity is 50-98 mPa·s, the plastic viscosity is 38-57 mPa·s, and the dynamic shear force is 10-41 Pa. The brine test slurry using the fluid loss reducer provided by the present invention is aged at 240°C for 16 hours. API The apparent viscosity is 33-58 mPa·s, the plastic viscosity is 23-45 mPa·s, and the dynamic shear force is 5-19 Pa. DETAILED DESCRIPTION

[0067] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0068] The sources of some components in the embodiments and comparative examples are as follows:

[0069] (1) 2-Acrylamido-2-methyl-1-propanesulfonic acid: purchased from Aladdin;

[0070] (2) N-[Tris(3-acrylamidopropylmethylether)methyl]acrylamide: purchased from FUJIFILM Wako.

[0071] The weight average molecular weight of the fluid loss reducers provided in the following examples and comparative examples was measured by gel permeation chromatography (Tosoh HLC-8420GPC).

[0072] Example 1

[0073] A fluid loss reducer, wherein the raw materials for preparing the fluid loss reducer include acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyldiallylammonium chloride, N-vinyl pyrrolidone, sodium hydroxide, ammonium persulfate-sodium bisulfite, N-[tris(3-acrylamidopropylmethyl ether)methyl]acrylamide and water;

[0074] The preparation method of the fluid loss reducer comprises the following steps:

[0075] (1) 16.6 g of 2-acrylamido-2-methyl-1-propanesulfonic acid was added to 150 mL of deionized water, the pH was adjusted to neutral with 40% NaOH solution, and then the mixture was transferred to a 250 mL three-necked flask;

[0076] (2) adding 17.2 g of acrylamide, 10.8 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride and 4.4 g of N-vinylpyrrolidone to the solution obtained in step (1), and stirring thoroughly to obtain a uniform mixed solution;

[0077] (3) Sufficient nitrogen is charged into the mixed solution obtained in step (2) to exclude oxygen, and the mixture is heated to 40° C. while stirring, and 200 mg of ammonium persulfate-sodium bisulfite (the mass ratio of ammonium persulfate to sodium bisulfite is 1:1) is added; 200 mg of N-[tri(3-acrylamide propyl methyl ether) methyl] acrylamide is dissolved in 10 mL of distilled water, and the mixture is added dropwise under stirring and the reaction is continued for 3 hours. After the reaction is completed, a pale yellow gel-like crude product is obtained, which is fully washed with anhydrous ethanol, dried, and crushed to obtain the filtrate reducer, and the weight average molecular weight of the filtrate reducer is about 400,000.

[0078] Example 2

[0079] A fluid loss reducer, wherein the raw materials for preparing the fluid loss reducer include N,N-dimethylacrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyldiallylammonium chloride, N-vinylpyrrolidone, sodium hydroxide, azobisisobutyronitrile, N-[tris(3-acrylamidopropylmethyl ether)methyl]acrylamide and water;

[0080] The preparation method of the fluid loss reducer comprises the following steps:

[0081] (1) 13 g of 2-acrylamido-2-methyl-1-propanesulfonic acid was added to 150 mL of deionized water, the pH was adjusted to neutral with 40% NaOH solution, and then the mixture was transferred to a 250 mL three-necked flask;

[0082] (2) adding 22.1 g of N,N-dimethylacrylamide, 5.5 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride and 6.4 g of N-vinylpyrrolidone to the solution obtained in step (1), and stirring thoroughly to obtain a uniform mixed solution;

[0083] (3) Sufficient nitrogen was charged into the mixed solution obtained in step (2) to exclude oxygen, and the solution was heated to 40° C. while stirring, and 200 mg of azobisisobutyronitrile was added, and 200 mg of N-[tris(3-acrylamidepropylmethylether)methyl]acrylamide was dissolved in 10 mL of distilled water, and the mixture was added dropwise under stirring and the reaction was continued for 3 hours. After the reaction, a pale yellow gel-like crude product was obtained, which was fully washed with anhydrous ethanol, dried, and crushed to obtain the filtrate reducer, and the weight average molecular weight of the filtrate reducer was about 300,000.

[0084] Example 3

[0085] A fluid loss reducer, wherein the raw materials for preparing the fluid loss reducer include N,N-dimethylacrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyldiallylammonium chloride, N-vinylcaprolactam, sodium hydroxide, azobisisobutyronitrile, N-[tris(3-acrylamidopropylmethyl ether)methyl]acrylamide and water;

[0086] The preparation method of the fluid loss reducer comprises the following steps:

[0087] (1) 13.6 g of 2-acrylamido-2-methyl-1-propanesulfonic acid was added to 150 mL of deionized water, the pH was adjusted to neutral with 40% NaOH solution, and then the mixture was transferred to a 250 mL three-necked flask;

[0088] (2) adding 17.7 g of N,N-dimethylacrylamide, 7.7 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride and 3.5 g of N-vinylcaprolactam to the solution obtained in step (1), and stirring thoroughly to obtain a uniform mixed solution;

[0089] (3) Sufficient nitrogen was introduced into the mixed solution obtained in step (2) to exclude oxygen, and the solution was heated to 40° C. while stirring, and 200 mg of azobisisobutyronitrile was added; 200 mg of N-[tri(3-acrylamidepropylmethylether)methyl]acrylamide was dissolved in 10 mL of distilled water, and the mixture was added dropwise under stirring and the mixture was stirred for 3 h. After the reaction, a pale yellow gel-like crude product was obtained, which was fully washed with anhydrous ethanol, dried, and crushed to obtain the filtrate reducer, and the weight average molecular weight of the filtrate reducer was about 260,000.

[0090] Example 4

[0091] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of 2-acrylamide-2-methyl-1-propane sulfonic acid used is 30 g, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 240,000.

[0092] Example 5

[0093] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of 2-acrylamide-2-methyl-1-propane sulfonic acid used is 11 g, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 350,000.

[0094] Example 6

[0095] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of N-vinyl pyrrolidone used is 10.7 g, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 220,000.

[0096] Example 7

[0097] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of N-vinyl pyrrolidone used is 2.7 g, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 360,000.

[0098] Example 8

[0099] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of a 60wt% dimethyldiallylammonium chloride aqueous solution is 15g, and the remaining raw materials, process parameters and steps are the same as those of Example 1. The weight average molecular weight of the fluid loss reducer is about 210,000.

[0100] Example 9

[0101] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of a 60wt% dimethyldiallylammonium chloride aqueous solution is 2.2g, and the remaining raw materials, process parameters and steps are the same as those of Example 1. The weight average molecular weight of the fluid loss reducer is about 420,000.

[0102] Example 10

[0103] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the amount of N-[tris(3-acrylamidepropylmethylether)methyl]acrylamide is 0.5 g, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 650,000.

[0104] Comparative Example 1

[0105] A fluid loss reducer, wherein the raw materials for preparing the fluid loss reducer include acrylamide, 2-acrylamido-2-methyl-1-propane sulfonic acid, dimethyldiallylammonium chloride, N-vinyl pyrrolidone, sodium hydroxide, ammonium persulfate-sodium bisulfite and water;

[0106] The preparation method of the fluid loss reducer comprises the following steps:

[0107] (1) 16.6 g of 2-acrylamido-2-methyl-1-propanesulfonic acid was added to 150 mL of deionized water, the pH was adjusted to neutral with 40% NaOH solution, and then the mixture was transferred to a 250 mL three-necked flask;

[0108] (2) adding 17.2 g of acrylamide, 10.8 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride and 4.4 g of N-vinylpyrrolidone to the solution obtained in step (1), and stirring thoroughly to obtain a uniform mixed solution;

[0109] (3) Sufficient nitrogen was charged into the mixed solution obtained in step (2) to exclude oxygen, and the mixture was heated to 40° C. while stirring, and 200 mg of ammonium persulfate-sodium bisulfite (the mass ratio of ammonium persulfate to sodium bisulfite was 1:1) was added, and the reaction was continued with stirring for 4 hours. After the reaction was completed, a pale yellow gel-like crude product was obtained, which was fully washed with anhydrous ethanol, dried, and crushed to obtain the filtrate reducer, and the weight average molecular weight of the filtrate reducer was about 160,000.

[0110] Comparative Example 2

[0111] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that N-[tris(3-acrylamidepropylmethylether)methyl]acrylamide is replaced with N,N-methylenebisacrylamide, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 380,000.

[0112] Comparative Example 3

[0113] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the raw materials include 19.1 g of acrylamide, 18.5 g of 2-acrylamido-2-methyl-1-propane sulfonic acid, 12.1 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride, and 0 g of N-vinylpyrrolidone, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 400,000.

[0114] Comparative Example 4

[0115] A fluid loss reducer and a preparation method thereof, which differs from Example 1 only in that the raw materials include 20.1 g of acrylamide, 19.5 g of 2-acrylamido-2-methyl-1-propane sulfonic acid, 5.2 g of N-vinyl pyrrolidone, and 0 g of a 60 wt% aqueous solution of dimethyldiallylammonium chloride, and the remaining raw materials, process parameters and steps are the same as those in Example 1. The weight average molecular weight of the fluid loss reducer is about 360,000.

[0116] Performance Testing

[0117] The fluid loss reducers provided in Examples 1-10 and Comparative Examples 1-4, and the fluid loss reducer Driscal D (purchased from ChevronPhillips Chemical, Driscal D Polymer) were sequentially prepared into freshwater test slurries and saltwater test slurries, and their rheological properties and fluid loss reduction performance in the freshwater test slurries and saltwater test slurries were tested;

[0118] 1. Test in fresh water test slurry, the preparation method of the fresh water test slurry is as follows:

[0119] Add 400 mL of tap water to a high-stirring cup, quantitatively add 16 g of bentonite and 0.56 g of anhydrous sodium carbonate under constant stirring, stir for 20 min, stop at least twice during the process to scrape off the clay adhering to the container wall, and cure in a sealed container for 24 h to obtain a freshwater base slurry; mix and dissolve 8 g of a fluid loss agent with 400 mL of the freshwater base slurry, and stir at high speed for 20 min to obtain the freshwater experimental slurry;

[0120] After the freshwater test pulp was aged at 240° C. for 16 h, the properties of the freshwater test pulp before and after aging were tested according to the following method. The test results are shown in Table 1.

[0121] (1) Apparent viscosity (AV): measured in accordance with GB / T16783.1-2014 Drilling Fluid Field Test using a six-speed viscometer (Qingdao Haitongda Special Instrument Co., Ltd., ZNN-D6);

[0122] (2) Plastic viscosity (PV): measured in accordance with GB / T16783.1-2014 Drilling Fluid Field Test using a six-speed viscometer (Qingdao Haitongda Special Instrument Co., Ltd., ZNN-D6);

[0123] (3) Dynamic shear force (YP): measured in accordance with GB / T16783.1-2014 Drilling fluid field test using a six-speed viscometer (Qingdao Haitongda Special Instrument Co., Ltd., ZNN-D6);

[0124] (4) API filtration loss (FL) API ): According to GB / T16783.1-2014 Drilling Fluid Field Test, the medium-pressure filtration loss of each freshwater experimental slurry before and after aging was measured using an API filtration tester (Qingdao Haitongda Special Instrument Co., Ltd., ZNS-2A);

[0125] Table 1

[0126]

[0127]

[0128]

[0129] It can be seen from the test data in Table 1 that adding the fluid loss reducer provided by the present invention to the freshwater test slurry can maintain the apparent viscosity and plastic viscosity of the freshwater test slurry before aging at a good level, and can still maintain a certain viscosity after aging at high temperature of 240°C for 16 hours, indicating that the fluid loss reducer provided by the present invention has a moderate viscosity-increasing effect and good temperature resistance; and the FL after high temperature aging API The minimum can reach 6mL, which has a good effect in reducing filtration loss.

[0130] From the comparison of freshwater test slurry 1 and freshwater test slurries 4-9, it can be seen that the freshwater test slurry 1 has lower filtration loss before and after aging and has better temperature resistance, and the freshwater test slurry 1 has higher dynamic shear force after aging, indicating that controlling the molar ratio of each monomer within an appropriate range can make the filtration loss reducer have good rheological properties, filtration loss reduction performance and temperature resistance.

[0131] From the comparison between freshwater test slurry 1 and freshwater test slurry 10, it can be seen that the filtration loss of freshwater test slurry 1 before and after aging is lower than that of freshwater test slurry 10, and it has better temperature resistance. However, the apparent viscosity and dynamic shear force of freshwater test slurry 10 before and after aging are too high, which is not conducive to flow. Too much cross-linking agent will deteriorate the rheological properties and filtration loss reduction performance of the filtration reducer.

[0132] From the comparison between freshwater test pulp 1 and freshwater test pulp 11, it can be seen that the filtration loss of freshwater test pulp 1 is lower before and after aging, and its temperature resistance is significantly better than that of freshwater test pulp 11. The introduction of cross-linking agent is beneficial to improving the temperature resistance of the filtration loss reducer.

[0133] From the comparison between freshwater test pulp 1 and freshwater test pulp 12, it can be seen that the filtration loss of freshwater test pulp 1 is lower before and after aging, and its temperature resistance is significantly better than that of freshwater test pulp 12. Compared with N,N-methylenebisacrylamide, the introduction of cross-linking agent N-[tri(3-acrylamidopropylmethylether)methyl]acrylamide is beneficial to improving the temperature resistance of the filtration loss reducer.

[0134] From the comparison between freshwater test slurry 1 and freshwater test slurry 13, it can be seen that the filtration loss of freshwater test slurry 1 is lower before and after aging, and its temperature resistance is significantly better than that of freshwater test slurry 13. The introduction of rigid monomer is conducive to improving the temperature resistance of the filtrate reducer.

[0135] From the comparison between freshwater test pulp 1 and freshwater test pulp 14, it can be seen that the filtration loss of freshwater test pulp 1 is lower before and after aging, and its temperature resistance is significantly better than that of freshwater test pulp 14. The introduction of olefinic cationic monomer is beneficial to improving the temperature resistance of the filtrate reducer.

[0136] From the comparison between the freshwater test pulp 1 and the freshwater test pulp 15, it can be seen that the freshwater test pulp 1 has lower filtration loss before and after aging, and its temperature resistance is significantly better than that of the freshwater test pulp 15. Compared with the filtration loss reducer Driscal D, the filtration loss reducer provided by the present invention has better temperature resistance.

[0137] 2. Test in a salt water test slurry, the preparation method of the salt water test slurry is as follows:

[0138] Add 400 mL of tap water to a high-stirring cup, quantitatively add 16 g of bentonite, 0.56 g of anhydrous sodium carbonate and 60 g of sodium chloride under constant stirring, stir for 20 min, stop at least twice during the process to scrape off the clay adhering to the container wall, and cure in a sealed container for 24 h to obtain a salt water base slurry; mix and dissolve 12 g of a fluid loss reducer with 400 mL of the salt water base slurry, stir at high speed for 20 min, and leave for 24 h to obtain the salt water experimental slurry;

[0139] After the brine test slurry was hot rolled and aged at 240°C for 16 hours, the apparent viscosity, plastic viscosity, dynamic shear force and API filtration loss of the brine test slurry before and after aging were tested according to the above method. The test results are shown in Table 2:

[0140] Table 2

[0141]

[0142]

[0143] From the test data in Table 2, it can be seen that the brine test slurry prepared with the filtration reducer provided by the present invention has a small filtration loss value before and after hot rolling aging at 240°C for 16 hours, has good filtration loss reduction performance, excellent temperature and salt resistance, and before and after aging, the rheological properties are maintained at a good level, and the high temperature stability is better.

[0144] From the comparison of salt water test slurry 1 and salt water test slurries 4-9, it can be seen that the filtration loss of salt water test slurry 1 is lower before and after aging, and it has better temperature and salt resistance. In addition, the salt water test slurry 1 has a higher dynamic shear force after aging, indicating that controlling the molar ratio of each monomer within an appropriate range can make the filtration loss reducer have good rheological properties, filtration loss reduction performance and temperature and salt resistance.

[0145] From the comparison between salt water test slurry 1 and salt water test slurry 10, it can be seen that the filtration loss of salt water test slurry 1 before and after aging is lower than that of salt water test slurry 10, and it has better temperature and salt resistance. However, the apparent viscosity and dynamic shear force of salt water test slurry 10 before and after aging are too high, which is not conducive to flow. Too much cross-linking agent will deteriorate the rheological properties and filtration loss reduction performance of the filtration reducer.

[0146] From the comparison between salt water test pulp 1 and salt water test pulp 11, it can be seen that the filtration loss of salt water test pulp 1 is lower before and after aging, and its temperature and salt resistance are significantly better than those of salt water test pulp 11. The introduction of cross-linking agent is beneficial to improving the temperature and salt resistance of the filtration loss reducer.

[0147] From the comparison between salt water test pulp 1 and salt water test pulp 12, it can be seen that the filtration loss of salt water test pulp 1 is lower before and after aging, and its temperature and salt resistance are significantly better than those of salt water test pulp 12. Compared with N,N-methylenebisacrylamide, the introduction of cross-linking agent N-[tri(3-acrylamidopropylmethylether)methyl]acrylamide is beneficial to improving the temperature and salt resistance of the filtration loss reducer.

[0148] From the comparison between salt water test pulp 1 and salt water test pulp 13, it can be seen that the filtration loss of salt water test pulp 1 is lower before and after aging, and its temperature and salt resistance are significantly better than those of salt water test pulp 13. The introduction of rigid monomer is conducive to improving the temperature and salt resistance of the filtrate reducer.

[0149] From the comparison between salt water test pulp 1 and salt water test pulp 14, it can be seen that the filtration loss of salt water test pulp 1 is lower before and after aging, and its temperature and salt resistance are significantly better than those of salt water test pulp 14. The introduction of olefinic cationic monomers is beneficial to improving the temperature and salt resistance of the filtrate reducer.

[0150] From the comparison between the salt water test pulp 1 and the salt water test pulp 15, it can be seen that the salt water test pulp 1 has lower filtration loss before and after aging, and its temperature and salt resistance are significantly better than those of the salt water test pulp 15. Compared with the filtration loss reducer Driscal D, the filtration loss reducer provided by the present invention has better temperature and salt resistance.

[0151] The above test results show that the fluid loss reducer provided by the present invention improves the adsorption capacity with bentonite by introducing rigid monomers, and improves the temperature resistance of the fluid loss reducer; the sulfonic acid group can play a good hydration role, has a good salt resistance and enhances the dispersion stability of bentonite; by introducing alkenyl cationic monomers, it can not only adsorb bentonite, but also improve the salt resistance of the fluid loss reducer; the micro-cross-linked structure formed by the introduced water-soluble acrylamide cross-linking agent significantly improves the rigidity of the fluid loss reducer, improves the temperature and salt resistance of the fluid loss reducer, and can also ensure the fluidity of the molecular chain of the fluid loss reducer. Therefore, the freshwater test slurry and salt water test slurry using the fluid loss reducer provided by the present invention have good rheological properties and fluid loss reduction effects, and the performance remains stable after hot rolling aging at 240°C for 16 hours, which is significantly better than the similar fluid loss reducer Driscal D.

[0152] The applicant declares that the present invention illustrates the fluid loss reducer and its preparation method and application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A fluid loss reducer, characterized in that: The raw materials for preparing the fluid loss reducer include a combination of a polymerizable monomer and a cross-linking agent; The polymerizable monomers include a combination of alkenyl amides, alkenyl sulfonic acids, rigid monomers, and alkenyl cationic monomers; The cross-linking agent has a structure as shown in Formula I: Wherein, R1, R2, and R3 are each independently selected from any one of C2-C6 straight-chain alkylene groups.

2. The fluid loss reducer according to claim 1, characterized in that: The alkenyl amide includes any one of acrylamide, N,N-dimethylacrylamide or N,N-diethylacrylamide, or a combination of at least two thereof.

3. The fluid loss reducer according to claim 1 or 2, characterized in that: The alkenyl sulfonic acid includes 2-acrylamido-2-methyl-1-propane sulfonic acid.

4. The fluid loss reducer according to any one of claims 1 to 3, characterized in that: The rigid monomer includes any one of N-vinyl pyrrolidone, N-vinyl caprolactam or N-acryloylmorpholine or a combination of at least two thereof.

5. The fluid loss reducer according to any one of claims 1 to 4, characterized in that: The alkenyl cationic monomer includes dimethyldiallylammonium chloride and / or dodecyldimethylallylammonium chloride.

6. The fluid loss reducer according to any one of claims 1 to 5, characterized in that: The molar ratio of the alkenyl amide to the alkenyl sulfonic acid is (2-4):1; Preferably, the molar ratio of the alkenyl amide to the rigid monomer is (3-8):1; Preferably, the molar ratio of the alkenyl amide to the alkenyl cationic monomer is (6-16):1; Preferably, the cross-linking agent comprises N-[tri(3-acrylamide propyl methyl ether) methyl] acrylamide and / or N-[tri(4-acrylamide butyl methyl ether) methyl] acrylamide; Preferably, the mass ratio of the polymerizable monomer to the cross-linking agent is (100-400):

1.

7. The fluid loss reducer according to any one of claims 1 to 6, characterized in that: The raw materials for preparing the fluid loss reducer also include an initiator; Preferably, the initiator comprises any one or a combination of at least two of a persulfate initiator, a redox initiator or an azo initiator; Preferably, the persulfate initiator comprises potassium persulfate and / or ammonium persulfate; Preferably, the redox initiator comprises ammonium persulfate-sodium bisulfite; Preferably, the azo initiator includes azobisisobutyronitrile and / or azobisisobutylimidazoline hydrochloride; Preferably, the mass ratio of the polymerization monomer to the initiator is (100-300):1; Preferably, the raw materials for preparing the fluid loss reducer further include a neutralizing agent; Preferably, the neutralizing agent comprises sodium hydroxide; Preferably, the raw material for preparing the fluid loss reducer further includes water; Preferably, the mass percentage of the polymerized monomer in the raw material for preparing the fluid loss reducer is 15-30%; Preferably, the weight average molecular weight of the fluid loss reducer is 260,000-400,000.

8. A method for preparing a fluid loss reducer according to any one of claims 1 to 7, characterized in that: The preparation method comprises: The filtrate reducer is obtained by reacting olefinic amide, olefinic sulfonic acid, rigid monomer, olefinic cationic monomer and crosslinking agent.

9. The preparation method according to claim 8, characterized in that: The alkenyl sulfonic acid is used in the form of an aqueous solution of alkenyl sulfonic acid; Preferably, the aqueous olefin sulfonic acid solution is first neutralized to neutrality using a neutralizing agent before use; Preferably, the neutralizing agent is used in the form of an aqueous neutralizing agent solution; Preferably, the mass percentage of the neutralizer in the neutralizer aqueous solution is 40-60%; Preferably, the alkenyl cationic monomer is used in the form of an aqueous solution of the alkenyl cationic monomer; Preferably, the mass percentage of the alkenyl cationic monomer in the aqueous solution of the alkenyl cationic monomer is 50-60%; Preferably, the cross-linking agent is used in the form of a cross-linking agent aqueous solution; Preferably, the mass percentage of the crosslinking agent in the crosslinking agent aqueous solution is 1-2%; Preferably, the reaction is carried out in the presence of an initiator; Preferably, the reaction temperature is 40-60°C; Preferably, the reaction time is 2-4h; Preferably, the reaction is carried out under a nitrogen atmosphere; Preferably, after the reaction is completed, the steps of washing, drying and crushing are further performed in sequence.

10. A drilling fluid, characterized in that: The components of the drilling fluid include the fluid loss reducer as described in any one of claims 1-7.

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