Anti-calcium nano-porous filtrate reducer for water-based drilling fluid and preparation method of anti-calcium nano-porous filtrate reducer

Abstract

The invention relates to the technical field of oilfield chemical drilling fluid treatment agents, in particular to an anti-calcium nano-porous filtrate reducer for water-based drilling fluid and a preparation method thereof.The anti-calcium nano-porous filtrate reducer for the water-based drilling fluid is prepared from 40-60 parts of sodium p-styrenesulfonate, 25-35 parts of phosphonic acid monomer, 8-15 parts of zwitterionic monomer and 1.5-3 parts of cross-linking agent. Dissolving and pre-emulsifying the monomer; and carrying out four-stage heating polymerization and pressure relief collection. According to the invention, monomers are subjected to four-order heating free radical polymerization reaction in supercritical CO2 to obtain a product with quadruple functions of high calcium chelation, high temperature stabilization, shale inhibition and low viscosity increasing, the API filter loss is less than or equal to 5mL, the HTHP filter loss is less than or equal to 12mL and the shale recovery rate is more than or equal to 90% under the conditions that Ca < 2 + > is more than or equal to 10000 mg / L and the temperature is 180 DEG C, the compatibility with a water-based drilling fluid is excellent, and the viscosity is not obviously increased.

Description

Technical Field

[0001] This invention relates to the field of oilfield chemical drilling fluid treatment agents, specifically an anti-calcium nanoporous filtration loss reducer for water-based drilling fluids and its preparation method. Background Technology

[0002] Anti-calcium nanoporous filtration reducer is mainly used in drilling fluids. It achieves dual functions through the special structure of nanoparticles: physical sealing and chemical adsorption, while also having anti-calcium properties.

[0003] Physical plugging works by nanoparticles (such as calcium carbonate) physically filling and blocking the micropores in the drilling fluid, forming a dense mud cake and reducing the filtrate permeation rate. When the nanoparticle size matches the pore diameter (dc>dp), it can directly block the pore inlet, effectively reducing filtrate loss. Chemical adsorption also works by nanoparticles (such as calcium carbonate) physically filling and blocking the micropores in the drilling fluid, forming a dense mud cake and reducing the filtrate permeation rate. This filtrate loss reducer typically uses a highly acid-soluble composite formula containing calcium carbonate and other components. In acidic environments (such as HCl immersion), inorganic components such as calcium carbonate can quickly dissolve and release active substances, enhancing the plugging effect. This calcium-resistant design makes it more stable in calcium ion-containing environments, avoiding performance degradation caused by calcium ion interference.

[0004] Anti-calcium nanoporous filtration loss reducer can be applied to high-temperature deep wells and complex geological conditions. The high thermal stability of nanoparticles (applicable temperature 30℃ to 180℃) ensures effective plugging in complex well sections. Through the synergistic effect of physical and chemical mechanisms, it effectively addresses complex geological conditions such as microcracks and micropores.

[0005] Chinese patent document CN119912914A discloses a method for preparing a filtration loss reducer, comprising the following steps: 2-acrylamido-2-methylpropanesulfonic acid solution is neutralized, mixed with acrylamide and sodium styrene sulfonate, and then polymerized under an anaerobic atmosphere and with an initiator to obtain a polymer; a uniformly dispersed nanomaterial suspension is added to the polymer, aged to form a gel, and then pulverized, dried, washed, dried again, and pulverized again to obtain the filtration loss reducer. However, this method mainly meets the needs of ultra-high temperature deep wells.

[0006] Chinese patent document CN116462810A discloses a filtration loss reducer, its preparation method, drilling fluids containing the same, and their applications. This invention uses cellulose derivatives, styrene sulfonates, diallyl ammonium salts, acrylamide monomers, and 2-acrylamido-2-methylpropanesulfonic acid as raw materials to prepare a polymeric framework matrix with certain high-temperature resistance, which is then grafted onto modified silica nanomaterials to synthesize the filtration loss reducer. However, its filtration loss at room temperature and pressure, its filtration loss at high temperature and pressure, and its calcium resistance still cannot meet the requirements for filtration loss control and shale suppression in extreme environments such as some deep wells, ultra-deep wells, and high-calcium formations.

[0007] Chinese patent document CN118702877A discloses a sulfonate filtration reducer for drilling fluids and its preparation method. By mass, it comprises 3-4 parts of nano-silica, 40-60 parts of 2-acrylamide-2-methylpropanesulfonic acid, 40-50 parts of sodium p-styrene sulfonate, 5-7 parts of modified halloysite nanotubes, and 1-2 parts of initiator. However, this technical solution improves molecular rigidity by grafting modified halloysite nanotubes onto the main chain and significantly increases the number of benzene ring structures. The benzene ring structure promotes a denser and thicker hydration film formed by the polymer molecules on the clay surface, effectively hindering the invasion of metal cations and protecting clay particles in high-salt, high-calcium environments, thus improving their resistance to salt and calcium intrusion.

[0008] With the widespread drilling of deep wells, ultra-deep wells, and high-calcium formations, water-based drilling fluids often face the challenge of calcium content. 2+ Extreme environments with concentrations ≥5000mg / L to 10000mg / L and temperatures ≥180℃. Existing filtration loss reducers mainly have the following problems: (1) The lignite-sulfonated phenolic resin compound system reacts with Ca in a high-calcium environment 2+ Complexation saturation, API filtration loss >60mL; (2) Acrylamide polymers coil their molecular chains under high mineralization, resulting in a sharp drop in filtration loss reduction performance; (3) After aging at 180℃ for 16 hours, the HTHP filtration loss of commercially available DriscalD is >50mL, and the shale recovery rate is <45%; (4) Although the nano-SiO2 composite system can reduce the filtration loss, it greatly increases the plastic viscosity, leading to the deterioration of rheology.

[0009] Therefore, there is an urgent need for a nanoporous filtration reducer that is "single-component, high-calcium chelated, high-temperature stable, and low-viscosity-increase" to meet the filtration control and shale suppression requirements of water-based drilling fluids in high-calcium and high-temperature environments. Summary of the Invention

[0010] This invention provides a calcium-resistant nanoporous filtration loss reducer for water-based drilling fluids and its preparation method, overcoming the shortcomings of the prior art. It can effectively solve the problem that existing water-based drilling fluids cannot meet the requirements for filtration loss control and shale inhibition under high calcium and high temperature environments.

[0011] One of the technical solutions of the present invention is achieved through the following measures: a water-based drilling fluid anti-calcium nanoporous filtration loss reducer, wherein the raw materials, by mass parts, include 40 to 60 parts of sodium styrene sulfonate, 25 to 35 parts of phosphonic acid monomer, 8 to 15 parts of zwitterionic monomer, 1.5 to 3 parts of crosslinking agent, and 1 to 2 parts of emulsifier, wherein the zwitterionic monomer is N-(3-methacrylamidopropyl)-N,N-dimethylammonium-N-propanesulfonic acid inner salt.

[0012] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The above-mentioned raw materials also include an initiator, the mass of which is 0.3% to 0.5% of the total mass of phosphonic acid monomer and zwitterionic monomer, and the initiator is dicyclohexyl peroxide or ammonium persulfate.

[0013] The phosphonic acid monomer mentioned above is an alkylphosphonic acid functional monomer with 12 to 14 carbon atoms, the crosslinking agent is N,N′-1,3-phenylenebismaleimide, and the emulsifier is emulsifier of type OP-10.

[0014] The above was prepared according to the following steps: S1, Preparation of the supercritical CO2 medium: Supercritical CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of supercritical CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

[0015] In step S1 above, the temperature of the reaction vessel is 37°C to 43°C and the pressure is 10.5 MPa to 11.5 MPa.

[0016] In step S2 above, the pre-emulsification temperature is 20℃ to 25℃, the pre-emulsification time is 20min to 40min, the stirring speed is 200rpm to 1000rpm, and the nitrogen gas introduction time is 10min.

[0017] In step S3 above, the four-stage heating process includes: heating to 43°C to 47°C and holding for 1 hour, heating to 63°C to 67°C and holding for 3 hours, heating to 83°C to 87°C and holding for 2 hours, and heating to 103°C to 107°C and holding for 1 hour.

[0018] In step S4 above, the pressure relief rate is 0.8 ± 0.1 MPa / s.

[0019] The second technical solution of the present invention is achieved through the following measures: a method for preparing a calcium-resistant nanoporous filtration loss reducer for water-based drilling fluid, comprising the following steps: S1, Preparation of the supercritical CO2 medium: CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

[0020] The following are further optimizations and / or improvements to the second technical solution of the above invention: In step S1 above, the temperature of the reaction vessel is 37°C to 43°C and the pressure is 10.5 MPa to 11.5 MPa.

[0021] In step S2 above, the pre-emulsification temperature is 20℃ to 25℃, the pre-emulsification time is 20min to 40min, the stirring speed is 200rpm to 1000rpm, and the nitrogen gas introduction time is 10min.

[0022] In step S3 above, the four-stage heating process includes: heating to 43°C to 47°C and holding for 1 hour, heating to 63°C to 67°C and holding for 3 hours, heating to 83°C to 87°C and holding for 2 hours, and heating to 103°C to 107°C and holding for 1 hour.

[0023] In step S4 above, the pressure relief rate is 0.8 ± 0.1 MPa / s.

[0024] This invention obtains a product with four functions—high calcium chelation, high-temperature stability, shale inhibition, and low viscosity increase—through a free radical polymerization reaction of monomers in supercritical CO2 with four stages of temperature increase. 2+ At ≥10000mg / L and 180℃, the API filtration loss is ≤5mL, the HTHP filtration loss is ≤12mL, the shale recovery rate is ≥90%, and it has excellent compatibility with water-based drilling fluids without significant viscosity increase. Detailed Implementation

[0025] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0026] The present invention will be further described below with reference to embodiments: Example 1: The water-based drilling fluid anti-calcium nanoporous filtration loss reducer contains the following raw materials by mass: 40 to 60 parts sodium styrene sulfonate, 25 to 35 parts phosphonic acid monomer, 8 to 15 parts zwitterionic monomer, 1.5 to 3 parts crosslinking agent, and 1 to 2 parts emulsifier. The zwitterionic monomer is N-(3-methacrylamidopropyl)-N,N-dimethylammonium-N-propanesulfonic acid inner salt.

[0027] Example 2: As an optimization of the above example, the raw materials also include an initiator, the mass of which is 0.3% to 0.5% of the total mass of the phosphonic acid monomer and the zwitterionic monomer, and the initiator is dicyclohexyl peroxide or ammonium persulfate.

[0028] Example 3: As an optimization of the above example, the phosphonic acid monomer is an alkylphosphonic acid functional monomer with 12 to 14 carbon atoms, the crosslinking agent is N,N′-1,3-phenylenebismaleimide, and the emulsifier is an emulsifier of type OP-10.

[0029] In the raw materials of this invention, sodium styrene sulfonate can provide a high density of negative charge, electrostatically repelling Ca. 2+ Prevent Ca 2+ Bridging; the phosphonic acid group can react with Ca 2+ Formation of stable six-membered ring chelates reduces free Ca. 2+ The concentration of zwitterionic groups can form a hydration layer on the clay surface, inhibiting shale hydration and expansion; the star-shaped cross-linking network after adding cross-linking agent can improve thermal stability at 180℃, preventing high-temperature degradation and particle size growth; the nanoporous structure of the obtained water-based drilling fluid anti-calcium nanoporous filtration loss reducer can quickly adsorb water molecules to form a dense filter cake, significantly reducing filtration loss, while having good pore connectivity and not significantly increasing viscosity.

[0030] In this invention, the method for preparing water-based drilling fluids involves adding 0.5 wt% to 2.0 wt% of a water-based drilling fluid anti-calcium nanoporous filtration loss reducer to conventional freshwater, brine, or saturated brine drilling fluids, followed by high-speed stirring for 20 minutes. No additional viscosifiers or shale inhibitors are required. The system exhibits an API filtration loss ≤10 mL, an HTHP filtration loss ≤20 mL (180℃ / 3.5 MPa), and a plastic viscosity increase of <15%.

[0031] Example 4: As an optimization of the above examples, the following steps were followed to prepare the following: S1, Preparation of the supercritical CO2 medium: Supercritical CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of supercritical CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

[0032] Example 5: As an optimization of the above example, in step S1, the temperature of the reaction vessel is 37°C to 43°C and the pressure is 10.5 MPa to 11.5 MPa.

[0033] Example 6: As an optimization of the above example, in step S2, the pre-emulsification temperature is 20°C to 25°C, the pre-emulsification time is 20 min to 40 min, the stirring speed is 200 rpm to 1000 rpm, and the nitrogen gas introduction time is 10 min.

[0034] Example 7: As an optimization of the above example, in step S3, the four-stage heating process includes: heating to 43°C to 47°C and holding for 1 hour, heating to 63°C to 67°C and holding for 3 hours, heating to 83°C to 87°C and holding for 2 hours, and heating to 103°C to 107°C and holding for 1 hour.

[0035] Example 8: As an optimization of the above example, in step S4, the pressure relief rate is 0.8 ± 0.1 MPa / s.

[0036] Example 9: The preparation method of this water-based drilling fluid anti-calcium nanoporous filtration loss reducer is carried out according to the following steps: S1, Preparation of the supercritical CO2 medium: CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

[0037] Example 10: The water-based drilling fluid uses an anti-calcium nanoporous filtration loss reducer. The raw materials, by mass fraction, include 55 parts sodium styrene sulfonate and 14 carbon atoms (i.e., C...). 14 The product contains 30 parts of alkylphosphonic acid functional monomer, 12 parts of N-(3-methacrylamidopropyl)-N,N-dimethylammonium-N-propanesulfonic acid inner salt, 2.2 parts of N,N′-1,3-phenylene bismaleimide, 0.3 parts of ammonium persulfate, and 1.2 parts of OP-10 emulsifier.

[0038] The water-based drilling fluid filtration loss reducer with calcium-resistant nanoporous material is obtained according to the following method: S1, Preparation of the supercritical CO2 medium: Supercritical CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of supercritical CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: Mix 55 parts sodium styrene sulfonate and 30 parts C 14 The alkylphosphonic acid functional monomer, 12 parts of N-(3-methacrylamidopropyl)-N,N-dimethylammonium-N-propanesulfonic acid inner salt, 2.2 parts of N,N′-1,3-phenylene bismaleimide, 0.3 parts of ammonium persulfate, and 1.2 parts of OP-10 emulsifier were added to a 500 mL three-necked flask. After pre-emulsification at 25 °C and 1000 rpm for 30 min, nitrogen gas was bubbled through the flask for 30 min to remove oxygen, and then the mixture was stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was reacted at a rate of 2±0.2℃ / min from 45℃ for 1 h, then heated to 65℃ for 3 h, then heated to 85℃ for 2 h, and finally heated to 105℃ for 1 h to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel was depressurized to atmospheric pressure at a constant rate of 0.8 ± 0.1 MPa / s. During depressurization, CO2 carried away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel was collected to obtain the anti-calcium nanoporous filtration loss reducer for water-based drilling fluid.

[0039] The performance of the water-based drilling fluid obtained in Example 10 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 4.3 mL, HTHP filtration loss: 9.6 mL, shale recovery rate: 92.8%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0040] Example 11: The difference from Example 10 is that C is... 14 The alkylphosphonic acid functional monomer is replaced with an equal part by mass of C 12 The alkylphosphonic acid functional monomer was prepared under the same conditions and methods as in Example 10.

[0041] The performance of the water-based drilling fluid obtained in Example 11 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 5.1 mL, HTHP filtration loss: 11.8 mL, shale recovery rate: 91%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0042] Example 12: The difference from Example 10 is that C is... 14 The alkylphosphonic acid functional monomer is replaced with an equal part by mass of C 13 The alkylphosphonic acid functional monomer was prepared under the same conditions and methods as in Example 10.

[0043] The performance of the water-based drilling fluid obtained in Example 12 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 4.7 mL, HTHP filtration loss: 10.4 mL, shale recovery rate: 92%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0044] Example 13: The difference from Example 10 is that the crosslinking agent N,N′-1,3-phenylene bismaleimide is 1.5 parts, and the other conditions and preparation methods are the same as in Example 10.

[0045] The performance of the water-based drilling fluid obtained in Example 13 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 4.9 mL, HTHP filtration loss: 11.2 mL, shale recovery rate: 90%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0046] Example 14: The difference from Example 10 is that the crosslinking agent N,N′-1,3-phenylenebismaleimide is 3.0 parts, and the other conditions and preparation methods are the same as in Example 10.

[0047] The performance of the water-based drilling fluid obtained in Example 14 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 4.2 mL, HTHP filtration loss: 9.1 mL, shale recovery rate: 93%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0048] Example 15: The difference from Example 10 is that the formula ratio is scaled up and carried out in a 10L stainless steel reactor with anchor stirring at 200rpm. The preparation method is the same as that in Example 10.

[0049] The performance of the water-based drilling fluid obtained in Example 15 was tested using an anti-calcium nanoporous filtration loss reducer. In Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 4.2 mL, HTHP filtration loss: 9.1 mL, shale recovery rate: 93%, AV increase: +2.1 mPa·s (base slurry from 6.5 mPa·s to 8.6 mPa·s).

[0050] The water-based drilling fluid anti-calcium nanoporous filtration loss reducer obtained in Example 15 had a yield of 94%, a particle size of 108±12 nm, and a BET of 191 μm. 2 / g; performance deviation from Example 10 <5%.

[0051] Example 16: Take Ca from a certain oil field 2+ 350 mL of 12300 mg / L, 1.25 g / cm³ water-based drilling fluid was mixed with 1.2% (w / w) of the anti-calcium nanoporous filtration reducer for water-based drilling fluid obtained in Example 10. The mixture was then hot-rolled at 180°C for 16 hours. API filtration loss: 4.2 mL (8.8 mL for raw pulp), HTHP filtration loss: 9.8 mL (20.4 mL for raw pulp), shale recovery rate: 93% (88% for raw pulp), AV increase: from 29 mPa·s to 33 mPa·s, PV increase: from 25 mPa·s to 28 mPa·s, YP remains basically unchanged.

[0052] Comparative Example 1: Commercially available sulfonated phenolic resin SMF was used as a filtration loss reducer. Under the same base slurry and test conditions as in Example 10, 2% by mass of SMF was added.

[0053] Performance tests were conducted on Comparative Example 1 at Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 47 mL, HTHP filtration loss: 63 mL, shale recovery rate: 51%, results significantly below standard.

[0054] Comparative Example 2: No filtration loss reducer added.

[0055] Performance tests were conducted on Comparative Example 2 at Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 78 mL, HTHP filtration loss: 96 mL, shale recovery rate: 42%, results significantly below standard.

[0056] Comparative Example 3: Using AM / AMPS binary copolymer as a filtration loss reducer, 2% by mass of AM / AMPS binary copolymer (AM70% + AMPS30% molecular weight 8 million to 10 million, conventional aqueous solution polymerization) was added under the same base slurry and test conditions as in Example 10.

[0057] Performance tests were conducted on Comparative Example 3, in Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 38 mL, HTHP filtration loss: 55 mL, shale recovery rate: 48%, and viscosity decreased by 65% ​​after aging.

[0058] Comparative Example 4: Commercially available lignite resin SPNH was used as a filtration loss reducer. Under the same base slurry and test conditions as in Example 10, 2% by mass of commercially available SPNH was added.

[0059] Performance tests were conducted on Comparative Example 4, in Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 42 mL, HTHP filtration loss: 62 mL, shale recovery rate: 52%, filter cake is thick and loose.

[0060] Comparative Example 5: Carboxymethyl starch (CMS) was used as a filtration loss reducer. Under the same base slurry and test conditions as in Example 10, 2% by mass of carboxymethyl starch (CMS) was added.

[0061] Performance tests were conducted on Comparative Example 5, in Ca... 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 35 mL, HTHP filtration loss: 49 mL, shale recovery rate: 45%, complete gelatinization and inactivation at 180℃.

[0062] Comparative Example 6: A nano-SiO2 composite system was used as a filtration loss reducer. Under the same base slurry and test conditions as in Example 10, 2% by mass of nano-SiO2 (20nm) + 0.5% by mass of dispersant was added.

[0063] Performance tests were conducted on Comparative Example 6 at Ca2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 28 mL, HTHP filtration loss: 38 mL, shale recovery rate: 50%, plastic viscosity increased from 6.5 mPa·s to 16.8 mPa·s, and rheological properties deteriorated.

[0064] Comparative Example 7: Using the foreign anti-calcium filtration loss reducer Driscal-D as the filtration loss reducer, under the same base slurry and test conditions as Example 10, 2% by mass of the foreign anti-calcium filtration loss reducer Driscal-D was added.

[0065] Performance tests were conducted on Comparative Example 7 at Ca 2+ Under the conditions of 10000 mg / L and hot rolling at 180℃ for 16 hours: API filtration loss: 31 mL, HTHP filtration loss: 46 mL, shale recovery rate: 61%, particle size increased by 230% after aging, and filter cake permeability increased.

[0066] Therefore, it can be seen that the anti-calcium nanoporous filtration loss reducer for water-based drilling fluids obtained in Examples 10 to 16 of the present invention all satisfy the requirement of "Ca". 2+ The revised indicators are "≥10000mg / L, API≤5mL, HTHP≤12mL at 180℃, and shale recovery rate≥90%", and the process is simple, reproducible, and suitable for industrial production and field application.

[0067] Test Example: Test Method The drilling fluid testing procedure was performed according to SY / T5621-2017. The base fluid formulation was: 4% bentonite + 0.2% Na2CO3 + water. After curing for 24 hours, 0.5%, 1.0%, 1.5%, and 2.0% (mass fraction) of the anti-calcium nanoporous filtration loss reducer for water-based drilling fluid of this invention were added respectively, along with CaCl2 to adjust the Ca content. 2+ =10000mg / L. Performance was measured after hot rolling at 180℃ for 16h, and the results are shown in Table 1. In Table 1, the HTHP conditions were: 180℃, 3.5MPa, 30min.

[0068] Table 1 .

[0069] As shown in Table 1, when the dosage of the anti-calcium nanoporous filtration loss reducer for the water-based drilling fluid of the present invention is 1.0% to 1.5%, the API filtration loss is ≤5mL, the HTHP filtration loss is ≤12mL, the shale recovery rate is ≥90%, and the increase in the plastic viscosity of the drilling fluid is <20%, which meets the requirements of on-site construction.

[0070] The beneficial effects of this invention are as follows: (1) The single component of the present invention can be used in Ca 2+ API filtration loss ≤5mL and HTHP filtration loss ≤12mL under conditions of ≥10000mg / L; (2) The performance retention rate of this invention after aging at 180℃ for 72h is >95%; (3) Shale rolling recovery rate ≥ 90%; (4) It has little impact on the rheological properties of drilling fluid, with an increase in plastic viscosity of <15%; (5) Raw material costs are ≥30% lower than those of imported products; (6) The process of this invention is free of organic solvents and is green and environmentally friendly.

[0071] The water-based drilling fluid obtained in this invention was characterized using an anti-calcium nanoporous filtration loss reducer. The data are as follows: TEM: particle size 102±15nm, clear porous structure; BET: specific surface area 192m². 2 / g, pore size 5nm to 15nm; XPS: phosphorus content 4.8wt%; TGA: weight loss at 300℃ <5%.

[0072] In summary, this invention obtains a product with four functions—high calcium chelation, high-temperature stability, shale inhibition, and low viscosity increase—through a free radical polymerization reaction of monomers in supercritical CO2 with four stages of temperature increase. 2+ With an API filtration loss of ≤5mL and an HTHP filtration loss of ≤12mL at ≥10000mg / L and 180℃, the shale recovery rate is ≥90%. Moreover, the process is green and low-cost, has excellent compatibility with water-based drilling fluids, does not significantly increase viscosity, and has good prospects for industrialization.

[0073] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A calcium-resistant nanoporous filtration loss reducer for water-based drilling fluids, characterized in that... The raw materials, by mass parts, include 40 to 60 parts of sodium styrene sulfonate, 25 to 35 parts of phosphonic acid monomer, 8 to 15 parts of zwitterionic monomer, 1.5 to 3 parts of crosslinking agent, and 1 to 2 parts of emulsifier, wherein the zwitterionic monomer is N-(3-methacrylamidopropyl)-N,N-dimethylammonium-N-propanesulfonic acid inner salt.

2. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 1, characterized in that... The raw materials also include an initiator, the mass of which is 0.3% to 0.5% of the total mass of the phosphonic acid monomer and the zwitterionic monomer. The initiator is dicyclohexyl peroxide or ammonium persulfate.

3. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 1 or 2, characterized in that... The phosphonic acid monomer is an alkylphosphonic acid functional monomer with 12 to 14 carbon atoms, the crosslinking agent is N,N′-1,3-phenylenebismaleimide, and the emulsifier is emulsifier with model number OP-10.

4. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 3, characterized in that... It is prepared according to the following steps: S1, Preparation of the supercritical CO2 medium: Supercritical CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of supercritical CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

5. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 4, characterized in that... In step S1, the temperature of the reaction vessel is 37°C to 43°C and the pressure is 10.5 MPa to 11.5 MPa.

6. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 5, characterized in that... In step S2, the pre-emulsification temperature is 20°C to 25°C, the pre-emulsification time is 20 min to 40 min, the stirring speed is 200 rpm to 1000 rpm, and the nitrogen gas is introduced for 10 min.

7. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 6, characterized in that... In step S3, the four-stage heating process includes: heating to 43°C to 47°C and holding for 1 hour, heating to 63°C to 67°C and holding for 3 hours, heating to 83°C to 87°C and holding for 2 hours, and heating to 103°C to 107°C and holding for 1 hour.

8. The anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 6 or 7, characterized in that... In step S4, the pressure relief rate is 0.8 ± 0.1 MPa / s.

9. A method for preparing the anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 3, characterized in that... Follow these steps: S1, Preparation of the supercritical CO2 medium: CO2 was introduced into the reaction vessel, and the temperature and pressure of the reaction vessel were adjusted to make the density of CO2 0.75 g / cm³. 3 Up to 0.85 g / cm 3 ; S2, monomer dissolution and pre-emulsification: The required amounts of sodium styrene sulfonate, phosphonic acid monomer, zwitterionic monomer, crosslinking agent, initiator and emulsifier are added to the reaction vessel for pre-emulsification, and then nitrogen gas is introduced and stirred to obtain the first mixture. S3, fourth-stage heated polymerization: The first mixture was subjected to a polymerization reaction by increasing the temperature in four stages at a rate of 2±0.2℃ / min to obtain the polymer. S4, pressure relief collection: The polymer in the reaction vessel is depressurized to atmospheric pressure at a constant rate. During depressurization, CO2 carries away the residual monomers and oligomers in the reaction vessel. The white powder in the reaction vessel is collected to obtain a calcium-resistant nanoporous filtration reducer for water-based drilling fluid.

10. The preparation method of the anti-calcium nanoporous filtration loss reducer for water-based drilling fluid according to claim 9, characterized in that... In step S1, the temperature of the reaction vessel is 37°C to 43°C and the pressure is 10.5 MPa to 11.5 MPa; or / and in step S2, the pre-emulsification temperature is 20°C to 25°C, the pre-emulsification time is 20 min to 40 min, the stirring rate is 200 rpm to 1000 rpm, and the nitrogen gas is introduced for 10 min; or / and in step S3, the four-stage heating process includes: heating to 43°C to 47°C and holding for 1 h, heating to 63°C to 67°C and holding for 3 h, heating to 83°C to 87°C and holding for 2 h, and heating to 103°C to 107°C and holding for 1 h; or / and the depressurization rate is 0.8 ± 0.1 MPa / s.