CN108690573B

CN108690573B - Reversible Pickering emulsion, preparation method thereof and reversible Pickering emulsion type drilling fluid

Info

Publication number: CN108690573B
Application number: CN201810862210.XA
Authority: CN
Inventors: 刘鹭; 蒲晓林; 李方; 王贵; 任妍君; 林燚
Original assignee: Southwest Petroleum University
Current assignee: Southwest Petroleum University
Priority date: 2018-08-01
Filing date: 2018-08-01
Publication date: 2022-01-04
Anticipated expiration: 2038-08-01
Also published as: CN108690573A

Abstract

The invention provides a reversible Pickering emulsion, which comprises an oil phase, a water phase and nano-particles activated in situ by an amino surfactant or an amino derivative surfactant. The nano-particles are lipophilic, hydrophilic or amphiphilic nano-oxides, and the amino surfactant is a primary amine, a secondary amine, a tertiary amine-based surfactant or a derivative thereof. The lipophilic nano-particles are activated in situ by short-chain amino or short-chain amino derivative surfactants; the hydrophilic or amphiphilic nanoparticles are activated in situ with a long chain amino group or long chain amino group derivative surfactant. The drilling fluid containing the emulsion can be used for preparing a soil-free, alkali-free or soil-free alkali-free drilling fluid, the prepared drilling fluid has a wide application range, and the density can be 0.8g/cm³～1.7g/cm³The method is directly adjustable, has better rheological property, suspension stability and filter cake removing property within the range of 100-200 ℃, effectively reduces the using amount and variety of treating agents, is environment-friendly, and can realize the reversion property of water-in-oil emulsion and oil-in-water emulsion for many times after high-temperature aging.

Description

Reversible Pickering emulsion, preparation method thereof and reversible Pickering emulsion type drilling fluid

Technical Field

The invention belongs to the technical field of drilling fluid, and particularly relates to reversible Pickering emulsion, a preparation method thereof and reversible Pickering emulsion type drilling fluid.

Background

Reversible emulsions are emulsions in which the phase behavior of the emulsion is reversible. On the basis of the existing emulsions, the change in the nature of the emulsifier enables a reversible phase inversion between water-in-oil emulsions and oil-in-water emulsions. At present, an emulsifier used for reversible emulsion with pH value response is mainly an organic amine surfactant, and the phase inversion of the emulsion is realized by utilizing the protonation and deprotonation of the organic amine surfactant. Oxidized fatty acids and the like are also used in reversible emulsions because their HLB value can be affected by acid and base. However, emulsions stabilized with surfactants have problems of large surfactant usage, high biotoxicity, high cost, and the like.

Pickering emulsions refer to emulsions stabilized by solid particles of colloidal size, the stabilization mechanism of which is primarily the adsorption of the solid particles at the oil-water interface and the formation of a monolayer/multilayer film of solid particles, thereby stabilizing the emulsion. Conventional emulsions stabilized by surfactants or amphiphilic polymers are thermodynamically unstable systems, whereas emulsions stabilized by surface-active colloidal particles, i.e. emulsions, are hyperstable. Pickering emulsions stabilized with solid particles require the use of only small amounts of surfactant or even no surfactant. In recent years, pickering emulsions have received increasing attention due to their low cost, environmental friendliness, high stability, and the like.

The reversible pickering emulsion is prepared by using nano particles as an emulsifier, changing the hydrophilicity and hydrophobicity of the surfaces of the nano particles by changing the pH of a water phase or the concentration of electrolyte and other influencing factors, and realizing the reversion of water-in-oil drilling fluid and oil-in-water drilling fluid. The domestic Sun German army et al provides an application patent of using Pickering emulsion formed by using carboxylate anionic surfactant and nano solid particles together as drilling fluid lubricant. Abroad MoCosh et al of Schlumberger company has successfully applied Pickering emulsion to oil-based drilling fluid, and the water-in-oil Pickering emulsion drilling fluid (named Slop-mud) formed by the oleophilic solid particles and the surfactant has very good stability and good anti-pollution performance. A. theGarwal et al use two SiO's of different degrees of hydrophobicity₂The W/O emulsified drilling fluid is prepared by using the W/O emulsified oil as a solid particle emulsifier. Shumway et al, haberton corporation, patented the use of pickering emulsions in W/O emulsified drilling fluids. However, the pickering emulsions described above are not reversible.

Liufei et al in the preparation and performance of modified nanoparticle stabilized reversible emulsified drilling fluid utilizes primary amine and tertiary amine surfactants to modify nano-silica, and prepares W/O emulsion breaking voltage with temperature resistance (180 ℃). However, this system has a problem that the preparation process is complicated because solid particles in the nanosilicon dioxide dispersion system containing the primary and tertiary amine surfactants are washed and dried, and then added to the system as an emulsifier. Secondly, the nano particles are not characterized after being dried, and whether the nano particles are nano-sized or not is unknown. Thirdly, the surfactant used is not specified here and the particles are only lipophilic nanosilica particles, which are highly dependent on the nature of the particles. Fourthly, the density of the drilling fluid system is 1.2g/cm³And organic soil and the like are required to be added for suspension stabilization. Fifth, only the lipophilic nanosilica modified by the tertiary amine surfactant in this document has acid-contact and alkali-contact abilities and reversibility, while the lipophilic nanoparticles modified by the primary amine product DUW-1 can prepare an initial water-in-oil emulsion, but after the acid-contact phase is an oil-in-water emulsion, the effective alkali-contact phase is a water-in-oil emulsion, that is, reversibility is not provided.

The conventional oil-based drilling fluid adopts organic soil to provide viscous shear force, and the organic soil is oleophylic clay prepared by modifying hydrophilic bentonite with quaternary ammonium salt cationic surfactant. However, the organic soil has the problems of slow activation, high-temperature thickening tendency, high plastic viscosity, inconvenience for field maintenance and the like. The drilling fluid is easy to cause underground complex accidents such as unsmooth tripping and sticking, and the mechanical drilling speed is low when the drill meets plastic mudstone, so that the development of the soil-free phase oil-based drilling fluid is urgently needed.

Disclosure of Invention

Aiming at the defects of the prior art, the application provides a method for utilizing the surface activity of amine groupThe preparation method comprises the steps of using an agent or an amino derivative surfactant to activate nanoparticles in situ, thereby controlling the surface property of the nanoparticles, preparing stable reversible pickering emulsion, and providing the preparation method of the reversible pickering emulsion; and can be used for preparing the soil-free phase drilling fluid, the alkali-free drilling fluid or the soil-free alkali-free drilling fluid. The prepared reversible Pickering emulsion type drilling fluid has wide application range and the density can be 0.8g/cm³～1.7g/cm³The emulsion is directly adjustable, and has better rheological property, suspension stability, filter cake removing property, filtration loss control property, environment friendliness and reversible properties of water-in-oil emulsion and oil-in-water emulsion within the temperature range of 100-200 ℃.

The invention provides a reversible pickering emulsion, which comprises an oil phase, a water phase and nanoparticles which are used as a stabilizing agent and are activated in situ by an amino surfactant or an amino derivative surfactant.

Wherein the oil phase is one or more of 0# diesel oil, 3# white oil, gassed oil, aviation kerosene, biodiesel, toluene, benzene, n-hexane-docosane or isomers thereof, cyclohexane, methyl myristate, undecanol and isopropyl myristate.

The water phase is pure water, tap water, or an electrolyte solution. Specifically, the electrolyte solution is a sodium carbonate solution, a sodium chloride solution, a calcium chloride solution or a magnesium chloride solution. Preferably, the concentration of the electrolyte solution is 0.01g/mL to 1 g/mL.

The nanoparticles include lipophilic, hydrophilic, or amphiphilic nano-oxide particles. Specifically, the nano-particles are one or more of nano-particles such as nano-silica, nano-alumina, nano-zinc oxide, nano-titanium oxide, nano-zirconium oxide, nano-magnesium oxide, nano-zirconium oxide, nano-ferroferric oxide, nano-tin oxide, nano-manganic oxide and the like. In the present invention, there is no specific requirement for the crystal form of the nanoparticles.

The nanoparticles can be prepared by a gas phase precipitation method or a liquid phase precipitation method which are commercially available. The original particle size of the nano-particles is between 15nm and 200 nm.

The amido has stronger adsorbability, can be effectively adsorbed on the surface of the nano-particles, and is selected as a modifier of the surface property of the nano-particles. In the invention, the self-hydrophily and lipophilicity of the amino surfactant or the amino derivative surfactant are utilized to activate the nano particles in situ, thereby adjusting the hydrophily or lipophilicity of the particle surface.

Specifically, the amino surfactant is a primary amine, a secondary amine or a tertiary amine surfactant, and the amino derivative surfactant is a primary amine, a secondary amine or a tertiary amine derivative surfactant.

Preferred amine-based surfactants or derivatives of amine-based surfactants include, but are not limited to:

1. piperidines;

2. anilines, benzylamines including aniline, o-aniline, p-aniline, benzylamine, phenylenediamine, benzyldiamine, and the like;

3. cyclic amines, pyrrolidinylamines including cyclopentylamine, cyclohexylamine, N, N dicyclohexylamine, and the like;

4. tertiary amines including N-dipropylamine, 2-ethylalkylamine, triisopropylamine, N, N-diisopropylethylamine, triethylamine and the like;

5. alkanolamines, alkyl diethanolamide, poly (dibutylamine) amide, poly (alkyloyl glycol), and the like;

6. amides, including N, N-diethylaminoamide, alkyl-diacetyl-amine, bis (3-dimethylaminopropyl) malonamide, and the like;

7. primary amines;

8. polyamines including N-alkyl tripropyl tetramine (N-alkyl propylenediamine) and the like, alkylamide dimethylamine, alkylamide polyethylene polyamine and the like;

9. hydroxyethylamines including N, N-bis (2-hydroxyethyl amide), N, N-bis (2-hydroxyethyl) alkylamine, and the like.

The most important stabilization mechanism of pickering emulsions is that the interfacial film formed by irreversible adsorption of particles at the emulsion droplet interface inhibits coalescence between the internal phase droplets of the emulsion. The type of emulsion is mainly influenced by the wettability of the solid particles, generally expressed in terms of contact angle. When the contact angle of the particles on the oil-water interface is less than 90 degrees, an O/W emulsion is formed; when the contact angle is greater than 90 °, a W/O emulsion is formed. Stable emulsions cannot be formed when the particles are strongly hydrophilic or lipophilic. In general, all factors that affect the surface properties and contact angle of the particles can affect the properties and stability of the emulsion. The presence of a surfactant will significantly affect the stability of a pickering emulsion if there is an interaction between the surfactant and the particles and changes the surface wettability of the particles.

Because the amido group on the surfactant has stronger adsorbability, the amido group can be effectively adsorbed on the surface of the nano-particles, so that the nano-particles are promoted to form a spatial three-dimensional structure in a dispersed phase, namely a weak gel state, under the action of a nonpolar solvent through the interaction of a hydrophobic bond and a hydrogen bond. The continuous phase in the weak gel state has certain viscoelasticity, so that the migration rate and the migration degree of emulsion droplets can be reduced, and the coalescence of the emulsion droplets is prevented. The principle is shown in fig. 1.

In the invention, the in-situ activation method is adopted to adjust the hydrophilicity and lipophilicity of the surface of the nano-particles, the surface properties of the nano-particles are not limited, and when the properties of the surface of the nano-particles are different, the amino surfactant or the amino derivative surfactant is selected to be matched with the nano-particles according to the following principle:

specifically, when the nanoparticles are lipophilic nanoparticles, short-chain amine-based surfactants or short-chain amine-derivative surfactants are used. In particular, the alkyl chain is C₃～C₆The functional group of the linear alkyl, branched alkyl and amino derivative is one or more of the following: piperidines, anilines, benzylamines, cyclic amines, pyrrolidinylamines, tertiary amines, alkanolamines, amides, polyamines, hydroxyethylamines. In particular to C₃～C₆Alkyl piperidine, C₃～C₆Alkylcyclohexylamino, C₃～C₆Alkyl anilines, C₃～C₆Alkyl o-anilines, C₃～C₆Alkyl para benzeneAmine, C₃～C₆Alkylbenzylamines, C₃～C₆Benzyldiamine, C₃～C₆Alkyl pyrrolidyl amine, cyclopentylamine, C₃～C₆Alkyl 2-ethyl alkylamine, C₃～C₆Alkyl tri (2-dimethylaminoethyl) amine, triisopropylamine, triethylamine, C₃～C₆Alkyl diethanolamide, C₃～C₆Alkyl acyl butanamic acid, C₃～C₆Alkyl acyl ethylene glycol, C₃～C₆Alkylamine (linear or branched), diethylenetriamine, triethylenetetramine, C₃～C₆Acyl polyethylene polyamines, N, N-bis (2-hydroxyethyl amide), N, N-bis (2-hydroxyethyl) alkylamine, and the like.

When the nano particles are hydrophilic nano particles, the amine-based surfactant or the derivative thereof is a long-chain amine-based surfactant or a long-chain amine-based derivative surfactant. In particular, the alkyl chain is C₆～C₃₀The functional group of the oil-based gas-liquid separation catalyst comprises long carbon chains such as straight-chain alkyl, branched-chain alkyl, tallow, coconut oil, oil base and isoalkyloxy, and the amino functional group is one or more of the following groups: piperidines, anilines, benzylamines, cyclic amines, pyrrolidinylamines, tertiary amines, alkanolamines, amides, polyamines, hydroxyethylamines. In particular to C₆～C₃₀Alkyl piperidine, C₆～C₃₀Alkylcyclohexylamino, C₆～C₃₀Alkyl anilines, C₆～C₃₀Alkyl o-anilines, C₆～C₃₀Alkyl p-aniline, C₆～C₃₀Alkylbenzylamines, C₆～C₃₀Alkylbenzyldiamines, C₆～C₃₀Alkyl pyrrolidinylamine, C₆～C₃₀Alkyl cyclopentylamine, C₆～C₃₀Alkyl N-dipropylamine, C₆～C₃₀Alkyl 2-ethyl alkylamine, C₆～C₃₀Alkyl tri (2-dimethylaminoethyl) amine, C₆～C₃₀Alkyl triisopropylamine, C₆～C₃₀Alkyl triethylamine, C₆～C₃₀Alkyl diethanolamide, C₆～C₃₀Alkyl acyl butanamic acids、C₆～C₃₀Alkyl acyl ethylene glycol, C₆～C₃₀Primary amines (linear or branched), C₆～C₃₀Alkyl diethylenetriamine, C₆～C₃₀Alkyl triethylene tetramine, C₆～C₃₀Alkylacylpolyethylene polyamines, C₆～C₃₀Alkyl N, N-bis (2-hydroxyethyl amide), C₆～C₃₀Alkyl N, N-bis (2-hydroxyethyl) alkylamine, and the like.

When the nano particles are amphiphilic nano particles, the contact angle of the interface is 80-120 degrees, and the stable water-in-oil Pickering emulsion can be formed independently. However, the formed emulsion is not reversible because the hydrophile lipophile of the nano particles in the emulsion can not be changed. Therefore, a very small amount of lipophilic amino surfactant needs to be added to realize the reversibility of the pickering emulsion. In this case, the amine-based surfactant or the derivative thereof is a long-chain amine-based surfactant or a long-chain amine derivative surfactant, and similarly, the alkyl chain thereof is C₆～C₃₀The functional group of the oil-based gas-liquid separation catalyst comprises long carbon chains such as straight-chain alkyl, branched-chain alkyl, tallow, coconut oil, oil base and isoalkyloxy, and the amino functional group is one or more of the following groups: piperidines, anilines, benzylamines, cyclic amines, pyrrolidinylamines, tertiary amines, alkanolamines, amides, polyamines, hydroxyethylamines. In particular to C₆～C₃₀Alkyl piperidine, C₆～C₃₀Alkylcyclohexylamino, C₆～C₃₀Alkyl anilines, C₆～C₃₀Alkyl o-anilines, C₆～C₃₀Alkyl p-aniline, C₆～C₃₀Alkylbenzylamines, C₆～C₃₀Alkylbenzyldiamines, C₆～C₃₀Alkyl pyrrolidinylamine, C₆～C₃₀Alkylcyclopentamines, N-dipropylamine, 2-ethylalkylamine, tris (2-dimethylaminoethyl) amine, C₆～C₃₀Alkyl triisopropylamine, C₆～C₃₀Alkyl triethylamine, C₆～C₃₀Alkyl diethanolamide, C₆～C₃₀Alkyl acyl butanamic acid, C₆～C₃₀Alkyl acyl ethylene glycol, C₆～C₃₀Primary amines (linear or branched), C₆～C₃₀Diethylenetriamine, C₆～C₃₀Triethylene tetramine, C₆～C₃₀Alkylacylpolyethylene polyamines, C₆～C₃₀Alkyl N, N-bis (2-hydroxyethyl amide), C₆～C₃₀Alkyl N, N-bis (2-hydroxyethyl) alkylamine, and the like.

The reversible pickering emulsion comprises the following components in percentage by weight: 40-80 parts by mass of an oil phase, 1-4 parts by mass of nanoparticles, 0.01-1 part by mass of an amino surfactant or an amino derivative surfactant, and 20-60 parts by mass of a water phase.

Preferably, the content of each component is as follows: 40-60 parts of oil phase, 1-4 parts of nano particles, 0.1-0.6 part of amino surfactant or amino derivative surfactant and 40-60 parts of water phase.

As a preferable scheme, the oil phase of the reversible pickering emulsion is one or a mixture of more of 0# diesel oil, 3# white oil, gas oil, aviation kerosene and biodiesel; the nano particles are one or more of nano silicon dioxide, nano aluminum oxide, nano zinc oxide and nano titanium oxide; the water phase is pure water or tap water.

The invention provides a preparation method of a reversible pickering emulsion, which comprises the following steps.

Step one, in-situ activation.

Adding amine surfactant or amine derivative surfactant and nanoparticles into the oil phase, and activating in situ to form weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding a water phase into the weak gel state oil phase suspension in the step one, and emulsifying to form the reversible pickering emulsion.

Specifically, in the step one, the in-situ activation method includes magnetic stirring, ball milling, ultrasonic dispersion in-situ activation and the like, and the in-situ activation time is 5 to 24 hours, preferably 12 to 24 hours.

When the activation is carried out by a magnetic stirring method, a straight line can be usedA rotor with the diameter of 1 cm-10 cm, a magnetic stirrer with the power of 100W-300W, stirring for 5-24 hours, preferably 12-24 hours until the weak gel state oil phase suspension is formed after full dispersion (the gel strength is 1-2 g/cm)²) The stirring was stopped.

When the activation is carried out by a ball milling method, the grinding balls made of alumina with the diameter of 5mm, 10mm or 20mm can be used for grinding in a polyethylene ball milling tank for 5 to 24 hours, preferably 12 to 24 hours until the oil phase suspension in the weak gel state is formed after the oil phase suspension is fully dispersed (the gel strength is 1 to 2 g/cm)²) And stopping ball milling.

When ultrasonic dispersion and in-situ activation are carried out, an ultrasonic cell disruption/vibration instrument can be used, the diameter of a vibration head is 3mm, the working frequency is 20KHz/10W, ultrasonic dispersion is carried out for 5 to 24 hours, preferably 12 to 24 hours, and the gel strength is 1 to 2g/cm when weak gel state oil phase suspension is formed after full dispersion (gel strength is 1 to 2 g/cm)²) The sonication was stopped.

In the second step, the emulsifying method comprises stirring and emulsifying by a high-speed stirrer, emulsifying by a homogenizer or ultrasonic emulsifying, wherein the emulsifying time is 5-4 h, preferably 10-30 min.

Specifically, when the high-speed stirrer is used for stirring and emulsifying, stirring is carried out for 5-4 hours, preferably 10-30 minutes, at the rotating speed of 10000-12000 r/min, and stirring is stopped until white emulsion is formed, so that emulsification is completed.

When the homogenizer is adopted for emulsification, the diameter of the metal vibrating rod is 10mm-50mm, the length of the metal vibrating rod is 100mm-450mm, the frequency is 10000-.

When ultrasonic emulsification is adopted, an ultrasonic cell disruption/vibration instrument can be used, the diameter of a vibration head is 3mm, the working frequency is 20KHz/10W, ultrasonic dispersion is carried out for 5min to 4h, preferably 10min to 30min, and the ultrasonic treatment is stopped after white emulsion is formed, so that the emulsification is completed.

Preferably, the gel strength of the weak gel oil phase suspension in the step one is 1-2 g/cm². At this time, the oil phase suspension has a moderate spatial structure and certain viscoelasticity, and the coalescence of the inner phase droplets is hindered. Weak flocculationThe nano particle coalescent body in the state is irreversibly adsorbed on the surface of the liquid drop, and can be effectively adsorbed around the water phase liquid drop to form a certain mechanical barrier, so that the prepared reversible Pickering emulsion has the highest stability.

Since the properties of the nanoparticles are different and the amine-based surfactant or amine-based derivative surfactant activated in situ is different, the following preferred method is employed in order to achieve better dissolution of the amine-based surfactant or amine-based derivative surfactant and the nanoparticles.

When the in-situ activated oleophilic nano-particles are used as a stabilizer to prepare the reversible pickering emulsion, the method comprises the following steps:

step one, adding a short-chain amino surfactant or a short-chain amino derivative surfactant into an oil phase, fully dissolving, then adding lipophilic nanoparticles, performing in-situ activation for 5-24 hours, preferably 12-24 hours, by using a magnetic stirring method, a ball milling method, an ultrasonic dispersion method and other modes until a weak gel state oil phase suspension is formed after full dispersion (the gel strength is 1-2 g/cm)²) And completing in-situ activation to form weak gel state oil phase suspension.

And step two, slowly adding the water phase into the weak gel state oil phase suspension in the step one, and stirring by using a high-speed stirrer, and emulsifying by using ultrasonic waves or a homogenizer.

Preferably, the method is carried out by the following steps:

adding a lipophilic nano material into an oil phase, fully dispersing by means of mechanical stirring, ball milling or ultrasonic waves and the like, then adding a short-chain amino surfactant or a short-chain amino derivative surfactant, and carrying out in-situ activation for 5-24 hours, preferably 12-24 hours by means of magnetic stirring, ball milling, ultrasonic dispersion and the like until a weak gel state oil phase suspension is formed after full dispersion (the gel strength is 1-2 g/cm)²) And completing in-situ activation to form weak gel state oil phase suspension.

The preparation method is adopted, firstly lipophilic nano particles are dispersed in an oil phase, the compatibility of the lipophilic nano particles and the oil phase is good, and then the short-chain amino surfactant or the short-chain amino derivative surfactant is added for in-situ activation, so that a better in-situ activation effect can be realized. The reversible Pickering emulsion using the in-situ activated oleophilic nano-particles prepared by the method as the stabilizer has the action principle shown in the attached figure 2.

The contact angle of the lipophilic nanoparticle interface is larger than 160-180 degrees, and the lipophilic nanoparticle interface is only dissolved in oil and can not form stable pickering emulsion alone. In the in-situ activation process of the step one, the lipophilic nanoparticles and the short-chain amine-based surfactant or the short-chain amine-based derivative surfactant are fully dispersed in a non-polar solvent, and under the action of hydrogen bond adsorption of the short-chain amine-based surfactant or the short-chain amine-based derivative surfactant, the nanoparticles are bridged mutually through the action of hydrophobic bonds and hydrogen bonds, so that the nanoparticles in a weak flocculation state are formed in the non-polar solvent. The nanoparticle agglomerates form a spatial three-dimensional structure in the dispersed phase, i.e., a weak gel state. Suspensions in the weak gel state have certain viscoelastic and shear thinning properties that can hinder coalescence of the internal phase droplets. And step two, in the emulsification process, the nanoparticle coalescent body in the weak flocculation state is irreversibly adsorbed on the surface of the liquid drop. The nano particle agglomeration body has a certain size, can effectively form space obstruction to the internal phase liquid drops and prevent the liquid drops from agglomerating, thereby forming stable pickering emulsion.

The short-chain amine-based surfactant or the short-chain amine derivative surfactant is adsorbed on the surface of the oleophylic nano-particles through amine groups, so that the lipophilicity of the nano-particles is reduced. The interfacial contact angle with the water phase is reduced from 160-180 degrees to 80-120 degrees, and the water-in-oil pickering emulsion formed by the nano material is most stable.

Because N atoms in the amino groups all have lone pair electrons, the amino groups can be protonated and deprotonated along with the change of the pH value, so that the hydrophilicity and lipophilicity of the surface of the nano material are changed. Under acidic conditions, the nanoparticle-stabilized water-in-oil pickering emulsion changes from a water-in-oil state to an oil-in-water state.This is due to the amine group and H⁺The hydrophilicity of the cationic amino group adsorbed on the surface of the nano particle is enhanced, the original oleophylic nano particle forms a hydrophilic nano particle aggregate with weak positive electricity in a nonpolar solvent, the hydrophilicity of the nano particle is further enhanced, and the water-in-oil emulsion is inverted into an oil-in-water emulsion. Under the alkaline condition, the amido is deprotonated, the hydrophobic property of a nanoparticle weak conglomerate formed by the originally oleophilic nanoparticles in a nonpolar solvent is recovered, and the Pickering emulsion is changed into a water-in-oil state from an oil-in-water state.

When the hydrophilic nanoparticles activated in situ are used as a stabilizer to prepare the reversible pickering emulsion, the method preferably comprises the following steps:

adding a long-chain amino surfactant or a long-chain amino derivative surfactant into an oil phase, fully dissolving, then adding hydrophilic nanoparticles, performing in-situ activation for 6-24 hours, preferably 12-24 hours, by using a magnetic stirring method, a ball milling method, an ultrasonic dispersion method and other modes until a weak gel state oil phase suspension is formed after full dispersion (the gel strength is 1-2 g/cm)²) And completing in-situ activation to form weak gel state oil phase suspension.

And step two, slowly adding a water phase into the weak gel state oil phase suspension obtained in the step one, and stirring by using a high-speed stirrer, and emulsifying by using ultrasonic waves or a homogenizer to form the reversible pickering emulsion.

The reversible Pickering emulsion using the in-situ activated hydrophilic nanoparticles prepared by the method as a stabilizer has the action principle shown in figure 3.

The contact angle between the hydrophilic nano-particles and the interface is less than 40 degrees, and the hydrophilic nano-particles are only dissolved in a polar solvent and can not form stable Pickering emulsion alone.

If the hydrophilic nanoparticles are activated in situ for a long time under the action of the long-chain amino surfactant or the long-chain amino derivative surfactant, the hydrophilic nanoparticles can be fully dispersed into the nonpolar solvent. The hydrophilic nano material adsorbs the oil-soluble amine-based surfactant through amine groups, and the lipophilicity is enhanced. The contact angle of the interface between the hydrophilic nano material and the water phase is improved to 80-120 degrees from the original angle less than 40 degrees, and the water-in-oil pickering emulsion formed by the nano material is most stable.

In addition, when the nanoparticles are fully dispersed in the non-polar solvent, the hydrogen bonds of the amino surfactant or the amino derivative surfactant promote the mutual bridging among the nanoparticles through the action of hydrophobic bonds and hydrogen bonds, weak structures are formed among the nanoparticles, and the nanoparticles are aggregated in a weak flocculation state in the non-polar solvent. The nanoparticle agglomerates form a spatial three-dimensional structure in the dispersed phase, forming a weak gel state with certain viscoelasticity and shear dilutability, hindering coalescence of the internal phase droplets. During the emulsification process, the nanoparticle agglomerates irreversibly adsorb to the surface of the internal phase droplets. The nano-particle agglomeration body has a certain size, can effectively form space obstruction to internal phase liquid drops and hinder the coalescence of the liquid drops, thereby forming stable water-in-oil emulsion.

Under alkaline conditions, the long-chain amine-based surfactant shows oil solubility, and the original hydrophilic nano material absorbs the lipophilicity enhancement of the long-chain amine, so that a hydrophobic nano particle aggregate is formed in a nonpolar solvent, and a stable water-in-oil pickering emulsion is formed. Under the acidic condition, the lone pair of the nitrogen atom in the amine group is connected with H⁺Positive charged cationic amino groups are formed, protonation of the amino surfactant forms charged hydrophilic nanoparticle aggregates, and the emulsion is changed from a water-in-oil state to an oil-in-water state.

When the in-situ activated amphiphilic nanoparticles are used as a stabilizer to prepare the reversible pickering emulsion, the method is preferably carried out according to the following steps:

step one, adding a long-chain amine-based surfactant into an oil phase, stirring by using a stirrer or dispersing by ultrasonic waves, mixing until the mixture is dissolved, then adding amphiphilic nanoparticles, activating in situ for 5-24 hours, preferably 12-24 hours, by using a magnetic stirring method, a ball milling method, ultrasonic dispersion and other methods until a weak gel state oil phase suspension is formed after full dispersion (the gel strength is 1-2 g/cm)²) And increasing the lipophilicity of the nano material to 90 degrees of contact angle with an oil phase interface to form a weak gel structure suspension.

And step two, slowly adding a water phase into the weak gel structure suspension obtained in the step one, and stirring by using a high-speed stirrer, and emulsifying by using ultrasonic waves or a homogenizer to form the reversible pickering emulsion.

The contact angle of the interface of the amphiphilic nano particles and the water phase is 80-120 degrees, the Pickering emulsion can be stabilized independently, and the formed emulsion is irreversible. Therefore, a very small amount of lipophilic amino surfactant needs to be added to realize the reversibility of the pickering emulsion.

When the reversible pickering emulsion is prepared by the method, the content of each component is 40-80 parts by mass of the oil phase, 1-4 parts by mass of the nano particles, 0.01-1 part by mass of the amino surfactant or the amino derivative surfactant and 20-60 parts by mass of the water phase.

The invention also provides a phase inversion method of the reversible Pickering emulsion, which comprises the following steps:

the phase inversion method of the reversible Pickering emulsion can utilize acid/base response or CO₂/N₂The stimulation response changes the pH value of the emulsion, so that the hydrophilicity and lipophilicity of the particle surface are adjusted, and the phase state change of the emulsion is realized.

1、CO₂/N₂The operation step of response: introducing 400mL of CO with the flow rate of 100-₂10s-10 min; introducing 400ml of N with the flow rate of 100-₂10s-10min。

CO₂/N₂The principle of the normal stimulation steering is as follows:

introducing CO into the W/O emulsion₂Gas, after fully mixing, the pH value of the solution is reduced to 6.5-4.2, and the skin can be reversedConverting the Kelin emulsion into O/W type; continuously introducing N₂After the gas is fully mixed, the pH value of the solution is raised to 7-10, and the emulsion is converted into W/O type. The process is repeated in this manner.

2. Acid/base response procedure: dropwise adding 1-10 parts of 5-30% by mass of hydrochloric acid aqueous solution, nitric acid aqueous solution, sulfuric acid aqueous solution, formic acid aqueous solution, oxalic acid aqueous solution, acetic acid aqueous solution or citric acid aqueous solution into the reversible Pickering emulsion, and stirring by magnetic force, high-speed stirring, manual shaking and glass rod stirring; dropwise adding 1-10 parts of 5-30% sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide solution, barium hydroxide solution and aluminum hydroxide solution, stirring by magnetic force, stirring at high speed, manually shaking, and stirring by a glass rod;

the acid/base response principle is:

adding acid solution into W/O emulsion to adjust pH to 6.5-2.2, magnetically stirring, high-speed stirring, manually shaking, and stirring with glass rod for 5-10min to convert the emulsion into O/W type; continuously adding alkali solution to make pH value be 6.5-11, and making magnetic stirring, or high-speed stirring, or manual shaking, or glass rod stirring, stirring for 5-10min, and making the emulsion be converted into W/O type.

The process is repeated so that the reversible pickering emulsion can be switched between W/O and O/W types multiple times.

The reversible pickering emulsion of the invention has the following beneficial effects.

The reversible pickering emulsion prepared by the method is a W/O emulsion, the precipitation amount of an oil phase is less than 5%, and the reversible pickering emulsion has the phenomena of no water phase precipitation and emulsion breaking, has the stability time of 2-8 months and has ultrahigh stability. The reversed O/W emulsion is also stable, the precipitation amount of a water phase is less than 5%, and the emulsion breaking phenomenon and oil phase precipitation are avoided, so that the stability time is long and the stability is high.

The reversible pickering emulsion of the invention can utilize acid/base response and CO₂/N₂And (3) stimulating response, and adjusting the hydrophilicity and lipophilicity of the surface of the particles so that the W/O type emulsion and the O/W type emulsion are mutually converted. The conversion can be carried out for many times without loss and emulsion breaking.

The reversible Pickering emulsion prepared by the invention is a W/O emulsion, the demulsification voltage is more than 700V, the conductivity is 0 mu S/cm, the emulsion is not obviously demulsified after being aged at the high temperature of 100-200 ℃, and the emulsion is kept stable. The high-temperature aging does not influence the smooth reversion of the emulsion and the stability of the emulsion. Acid/base response, CO, utilization of aged reversible pickering emulsions₂/N₂Stimulating response, and converting the mixture into O/W emulsion with demulsifying voltage of 0-20V and conductivity of 0.02-100 ms/cm.

The reversible Pickering emulsion W/O emulsion prepared by the invention is milky emulsion in appearance, narrow in particle size distribution, less than 0.2 in polydisperse particle size and 5-40 mu m in average particle size. By acid/base response or CO₂/N₂After the stimulation response, the emulsion is milky white emulsion, the particle size distribution is narrow, the polydisperse particle size is less than 0.2, and the average particle size is 5-40 mu m.

The invention also provides a reversible pickering emulsion type drilling fluid which comprises 100 parts by mass of the pickering emulsion, 0-3 parts by mass of organic soil, 0-4 parts by mass of alkalinity regulator, 1-5 parts by mass of filtrate reducer, 0-7 parts by mass of shear improver, 0-3 parts by mass of wetting agent and 0-77 parts by mass of weighting material.

As a preferable scheme, the drilling fluid comprises 100 parts by mass of Pickering emulsion, 0-3 parts by mass of organic soil, 0-4 parts by mass of alkalinity regulator, 1-5 parts by mass of filtrate reducer, 0-4 parts by mass of shear improver, 0-3 parts by mass of wetting agent and 0-77 parts by mass of weighting material.

Specifically, in the invention, the organic soil is mainly quaternary ammonium salt modified montmorillonite.

The alkalinity regulator is quicklime.

The fluid loss additive is one or a mixture formed by mixing two or more of oxidized asphalt, humic acid amide, organic lignite and the like in any proportion. The organic solvent contains various polar groups such as oil carboxyl, hydroxyl, ether group, amide group, benzyl group and the like.

The cutting-improving agent is a common cutting-improving agent for oil-based drilling fluid, such as a polyacid micromolecule polymer, a polyester cutting-improving agent, propylene carbonate, pentaerythritol oleate and the like.

The wetting agent is plant pine tar, plant oleic acid, lecithin, oleic acid, long chain alkyl polyoxyethylene ether nonionic surfactant, etc.

The weighting agent is one or a mixture of any two or more of barite, iron ore powder, limestone powder and manganese tetraoxide mixed in any ratio.

The reversible Pickering emulsion type drilling fluid is prepared by the following method: adding 0-3 parts by mass of organic soil, 0-4 parts by mass of alkalinity regulator, 1-5 parts by mass of filtrate reducer, 0-7 parts by mass of shear improver and 0-3 parts by mass of wetting agent into 100 parts by mass of reversible pickering emulsion, and adding 0-77 parts by mass of weighting material to enable the drilling fluid to reach the required density, stirring at a high speed of 800-12000r/min during the addition, and stirring at a high speed for 10-30 min after all the treatment agents are added to obtain the reversible pickering emulsion type drilling fluid.

As a preferable scheme, the reversible Pickering emulsion type drilling fluid is prepared by adopting the following method,

adding 0-3 parts by mass of organic soil, 0-4 parts by mass of alkalinity regulator, 1-5 parts by mass of fluid loss additive, 0-4 parts by mass of shear enhancing agent, 0-3 parts by mass of wetting agent, 0-77 parts by mass of weighting material, 1-5 parts by mass of fluid loss additive, 0-7 parts by mass of shear enhancing agent and 0-3 parts by mass of wetting agent into 100 parts by mass of reversible pickering emulsion, and adding 0-77 parts by mass of weighting material to enable the drilling fluid to reach the required density, when the drilling fluid is added, keeping high-speed stirring at 800-12000r/min, and after all the treating agents are added, keeping high-speed stirring for 20min to obtain the reversible pickering emulsion type drilling fluid.

The reversible pickering emulsion prepared by the invention has higher viscosity, stronger shearing dilutability and suspension stability. These advantages determine that organic soil, a tackifier, a shear strength improver and the like can be optionally not used when the drilling fluid is prepared. Furthermore, the reversible pickering emulsions of the present invention may haveThe effective suspending weighting agent can be added to the density of 0.8 to 1.7g/cm³。

Preferably, the soilless reversible pickering emulsion type drilling fluid can be prepared. At this time, the addition amount of the organic soil in the reversible pickering emulsion type drilling fluid is 0 part by mass, and the reversible pickering emulsion type drilling fluid containing no organic soil is prepared. Specifically, the reversible pickering emulsion type drilling fluid comprises 100 parts by mass of the pickering emulsion, 0-4 parts by mass of an alkalinity regulator, 1-5 parts by mass of a filtrate reducer, 0-7 parts by mass of a shear promoter, 0-3 parts by mass of a wetting agent and 0-77 parts by mass of a weighting material.

Conventional oil-based drilling fluids require the addition of organic soils to provide viscous shear. However, the organic soil has the problems of slow activation, high-temperature thickening tendency, high plastic viscosity, inconvenience for field maintenance and the like. Under the condition of high density, the rheological property of the drilling fluid is influenced by the addition of the organic soil, so that the problems of unsmooth tripping of a drill, easy sticking and blockage to cause underground complex accidents, high content of low solid phase, high equivalent circulating density, easy induction of well leakage and low mechanical drilling speed when the drill meets plastic mudstone are caused.

The reversible pickering emulsion has higher viscosity and stronger shearing and diluting performance under lower solid particle concentration. The soilless phase reversible pickering emulsion type drilling fluid system prepared by utilizing the advantage of the rheological property of the pickering emulsion has the advantages of good shearing dilutability, contribution to the transmission of water horsepower of a drill bit, reduction of circulating pressure consumption, low loss amount, low comprehensive cost and the like.

Preferably, the alkali-free reversible pickering emulsion type drilling fluid can be prepared. At this time, the addition amount of the alkalinity regulator in the reversible pickering emulsion type drilling fluid is 0 part by mass, and a reversible pickering emulsion type drilling fluid without alkalinity is prepared. Specifically, the drilling fluid comprises 100 parts by mass of the pickering emulsion, 0-3 parts by mass of organic soil, 1-5 parts by mass of a filtrate reducer, 0-7 parts by mass of a shear improver, 0-3 parts by mass of a wetting agent and 0-77 parts by mass of a weighting material.

In the prior art, most of the emulsifiers are required to form stable emulsion under alkaline condition. The lime being oilBased on the necessary components in the drilling fluid, Ca which it provides²⁺The generation of binary metal soap is facilitated, so that the full exertion of the efficiency of the emulsifier is ensured; the pH value of the oil-based drilling fluid can be maintained in an alkaline range, and the pollution of drilling tools and acid gas to the drilling fluid can be prevented. However, due to lime and CO₂Reaction, which can affect accurate CO measurement and recording₂Content of (A), sometimes determining CO by using logging data during drilling₂The amount of (c) is advantageous. It is therefore necessary to develop an alkali-free water-in-oil drilling fluid system.

The alkalinity-free reversible Pickering emulsion type drilling fluid can adjust the alkalinity without limestone, and has good stability.

The reversible Pickering emulsion type drilling fluid prepared by the invention has the following technical effects.

The reversible Pickering emulsion type drilling fluid prepared by the invention is a Pickering emulsion prepared from an oil phase suspension in a weak gel state, and the nano particle coalescent body is covered in a weak gel space grid structure to prevent coalescence of inner phase droplets. In the emulsification process, the nanoparticle coalescent irreversibly adsorbs to the surface of the inner phase droplet, and can effectively form spatial barrier to the inner phase droplet. Therefore, the pickering drilling fluid has the advantages and characteristics different from the common oil-based drilling fluid in the aspect of rheology:

1. the reversible Pickering emulsion type drilling fluid has the advantages of strong internal structure, high structural viscosity, strong shearing and diluting capability, strong rock carrying and suspending capacity and contribution to purification in large boreholes and horizontal well annular boreholes.

2. Because the internal structure is strong, the drilling fluid is suitable for clay-free phase or low solid phase drilling fluid, the content of submicron particles is low, and the drilling speed is favorably improved.

The reversible Pickering emulsion type drilling fluid prepared by the invention has higher viscosity and stronger shearing dilutability, and organic soil, a tackifier, a shear-improving agent and the like can be selected not to be used; effectively reduces the using amount and the variety of the used treating agent, saves the cost and is convenient to maintain.

And thirdly, the reversible Pickering emulsion type drilling fluid prepared by the invention can realize the reversible drilling fluid without solid phase and/or lime.

The reversible Pickering emulsion drilling fluid can be added with corresponding treating agents according to different working conditions to form Pickering emulsion drilling fluids of different types so as to meet the drilling requirements; the operation and maintenance are simple; no need of additional development of treating agent, convenient use and low cost.

And (IV) the reversible Pickering emulsion type drilling fluid prepared by the invention mainly depends on the nano particles to stabilize the emulsion. The amount of the surfactant used is very small, and is only 0.01 to 1 part by mass. Can greatly reduce the environmental pollution caused by the surfactant, and has the advantages of biodegradability, low cost and easy preparation.

The reversible Pickering emulsion type drilling fluid prepared by the invention has ultrahigh stability, and the continuous phase precipitation amount of the drilling fluid is less than 5% after the emulsion is static for 2-6 months. The demulsification voltage before and after high temperature aging is more than or equal to 700V, the temperature resistance of the drilling fluid can reach 100-200 ℃, and the density can be increased to 0.8-1.7 g/cm³And the high-temperature high-pressure filtration loss is less than or equal to 10 ml. The W/O drilling fluid system has good temperature resistance, small filtration loss and good emulsion stability.

(VI) the reversible Pickering emulsion drilling fluid prepared by the invention can utilize acid/base response or CO2/N₂And (3) stimulating response, and adjusting the hydrophilicity and lipophilicity of the surface of the particles so that the W/O type emulsion and the O/W type emulsion are mutually converted. The conversion can be carried out for many times without loss and emulsion breaking.

The reversible Pickering emulsion type drilling fluid prepared by the invention does not influence the smooth reversion of the emulsion and the stability of the W/O state and the O/W state of the emulsion after high-temperature aging at 100-200 ℃, and can be reversed for many times after high-temperature aging.

(eighthly), the reversible Pickering emulsion drilling fluid prepared by the invention has the performance of water-in-oil drilling fluid, and has good thermal stability, lubricity, anti-collapse inhibition property and reservoir protection property; the oil-in-water drilling fluid is formed by inversion, so that the problems that filter cakes generated by the water-in-oil drilling fluid are difficult to remove, the bonding strength between cement and a stratum is weak, and residual oil, drill cuttings and waste mud of the drill cuttings are difficult to treat can be solved; has the advantages of water-in-oil drilling fluid and oil-in-water drilling fluid.

Drawings

FIG. 1 is a stabilization mechanism for reversible Pickering emulsions stabilized by in situ activated nanoparticles of the invention.

FIG. 2 is the principle of the reversible Pickering emulsion stabilized by the in situ activated lipophilic nanoparticles of the present invention.

FIG. 3 is the principle of the reversible Pickering emulsion stabilized by the in situ activated hydrophilic nanoparticles of the present invention.

FIG. 4 is a graph showing the rheological properties of a weakly gelled oil phase suspension of example 1 of the present invention.

FIG. 5 is a graph showing the rheological properties of a weakly gelled oil phase suspension of example 1 of the present invention.

FIG. 6 is a graph of gel strength of a weak gel state oil phase suspension versus emulsification of a reversible pickering emulsion.

Fig. 7 shows the contact angle of the lipophilic nano-silica particles, and the left and right graphs show the contact angles of the lipophilic nano-silica particles before and after in-situ activation, respectively, in example 1.

FIG. 8 is a graph of the appearance of an acid/base stimulus responsive reversible pickering emulsion of example 1 of the present invention.

FIG. 9 is a graph of the change in conductivity in acid-base stimulation response of the reversible Pickering emulsion of example 1 of the present invention.

FIG. 10 is an appearance diagram of a reversible Pickering emulsion of example 11 of the present invention.

FIG. 11 is a graph of the particle size distribution of the reversible Pickering emulsion of example 11 of the present invention.

FIG. 12 shows CO in example 11 of the present invention₂/N₂Appearance of the responsive reversible pickering emulsion.

FIG. 13 shows a reversible Pickering emulsion CO according to example 11 of the invention₂/N₂Graph of the change in conductivity of the stimulus response.

FIG. 14 is a graph of the change in conductivity during acid contact of the reversible pickering emulsion of example 23 of the present invention.

FIG. 15 is a graph of the change in conductivity during alkaline contact of the reversible pickering emulsion of example 23 of the present invention.

Fig. 16 is a graph of the change in conductivity during acid contact of an amphiphilic nanoparticle stabilized pickering emulsion without in situ activation.

Fig. 17 is a graph of the change in conductivity during base contact of an amphiphilic nanoparticle stabilized pickering emulsion without in situ activation.

FIG. 18 is a graph of the suspending capacity of the reversible Pickering emulsion drilling fluid of example 23 for a solid phase, in order from left to right: sandstone, nano-barite powder, API barite powder, shale, and blank emulsion.

Figure 19 is a graph of the removal capacity of the soil-free, alkali-free reversible pickering emulsion drilling fluid filter cake prepared in example 27, wherein the left graph is before acid treatment and the right graph is after acid treatment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are further described below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Examples 1 to 10 are methods for the preparation of in situ activated lipophilic nanoparticle stabilized reversible pickering emulsions.

Example 1

Step one, in-situ activation.

Taking 100 parts by mass of 0# diesel oil as an oil phase, adding 2 parts by mass of oleophylic nano-silica particles as nano-particles, ball-milling a grinding ball with the diameter of 5mm, 10mm or 20mm in a polyethylene ball-milling tank for 10-20 min, uniformly mixing, adding 0.2 part by mass of n-pentylamine serving as a surfactant, and continuing ball-milling for 5-24 h until the gel strength is 1-2 g/cm²Stopping, and completing the in-situ activation of the nano particles to obtain the weak gel state oil phase suspension.

And step two, emulsification.

And (2) slowly adding 125 parts by mass of deionized water into the weak gel state oil phase suspension obtained in the first step to serve as a water phase, emulsifying by using a homogenizer, wherein the diameter of a metal vibrating rod of the homogenizer is 10-50 mm, the length of the metal vibrating rod is 100-450 mm, the frequency is 10000-13500r/min, and the emulsifying time is 5-4 h, and after the emulsification is finished, cooling to room temperature by ice bath to obtain the reversible Pickering emulsion.

Examples 2 to 7 were prepared in the same manner as in example 1, except that the raw materials selected included components of the oil phase, the ratio of the oil phase, components of the surfactant, the ratio of the surfactant, the type of the nanoparticle, the ratio of the nanoparticle, and components of the aqueous phase and the ratio of the aqueous phase. See table 1 below.

Table 1 raw material components and compounding ratios of examples 2 to 7

Example 8

Step one, in-situ activation.

Taking 60 parts by mass of 0# diesel oil as an oil phase, adding 0.2 part by mass of surfactant diethylenetriamine, magnetically stirring and mixing, using a rotor with the diameter of 1-10 cm and the power of a magnetic stirrer of 100-300W, stirring for 10-30 min, adding 4 parts by mass of oleophylic nano silicon dioxide particles as nano particles, and continuing magnetically stirring for 12-24 h until the gel strength is 1-2 g/cm²Stopping, and completing the in-situ activation of the nano particles to obtain the weak gel state oil phase suspension.

And step two, emulsification.

And (3) slowly adding 40 parts by mass of deionized water serving as a water phase into the weak gel state oil phase suspension obtained in the step one, stirring and emulsifying by using a high-speed stirrer, wherein the stirring speed is 8000-12000r/min, the emulsifying time is 10-20 min, and after the emulsification is finished, cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Example 9

Taking 80 parts by mass of gas-to-liquid oil as an oil phase, adding 2 parts by mass of oleophylic nano magnesium dioxide particles as nano particles,using an ultrasonic cell disruption/vibration instrument, wherein the diameter of a vibration head is 3mm, the working frequency is 20KHz/10W, ultrasonic dispersion is carried out for 10-30 min, the mixture is uniformly mixed, then 0.4 part by mass of amino surfactant N- (2-hydroxyethyl) ethylenediamine is added, ultrasonic dispersion is continuously carried out for 12-24 h until the gel strength is 1-2 g/cm²Stopping, and completing the in-situ activation of the nano particles to obtain the weak gel state oil phase suspension.

And step two, emulsification.

And (3) slowly adding 20 parts by mass of 0.5g/mL calcium chloride aqueous solution serving as a water phase into the weak gel state oil phase suspension obtained in the first step for emulsification, using an ultrasonic cell disruption/vibration instrument, wherein the diameter of a vibration head is 3mm, the working frequency is 20KHz/10W, the emulsification time is 10-30 min, and after emulsification is finished, cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Example 10

Taking 60 parts by mass of gas-to-oil as an oil phase, adding 2 parts by mass of oleophilic nano ferroferric oxide particles as nano particles, magnetically stirring and mixing, using a rotor with the diameter of 1 cm-10 cm, stirring for 10-30 min by using a magnetic stirrer with the power of 100W-300W, uniformly mixing, then adding 1 part by mass of surfactant cyclohexylamine, and magnetically stirring for 12-24 h until the gel strength is 1-2 g/cm²Stopping, and completing the in-situ activation of the nano particles to obtain the weak gel state oil phase suspension.

And step two, emulsification.

And (3) slowly adding 30 parts by mass of a 1g/mL sodium chloride aqueous solution serving as a water phase into the weak gel-state oil phase suspension obtained in the first step, stirring and emulsifying by using a high-speed stirrer at the stirring speed of 8000-12000r/min for 10-30 min, and cooling to room temperature in an ice bath after emulsification is finished to obtain the reversible Pickering emulsion.

Examples 11-22 are methods of preparing in situ activated hydrophilic nanoparticle stabilized reversible pickering emulsions.

Example 11

Step one, in-situ activation.

Taking 100 parts by mass of 0# diesel oil as an oil phase, adding 0.5 part by mass of surfactant oleamide dimethylamine, and magnetically stirringStirring to fully dissolve, adding 2 parts by mass of hydrophilic nano silicon dioxide particles serving as nano particles, and ball-milling for 5-24 hours in a polyethylene ball-milling tank by using milling balls with the diameter of 5mm, 10mm or 20mm until the gel strength is 1-2 g/cm²Stopping, and completing the in-situ activation of the nano particles to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 100 parts by mass of deionized water into the weak gel state oil phase suspension in the step one as a water phase, stirring and emulsifying by using a high-speed stirrer at a stirring speed of 8000-12000r/min for 5-4 h, and cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Examples 12 to 20 were prepared in the same manner as in example 11, except that the raw materials selected for the preparation included components of the oil phase, the compounding ratio of the oil phase, components of the surfactant, the compounding ratio of the surfactant, the kind of the nanoparticles, the compounding ratio of the nanoparticles, and components of the aqueous phase and the compounding ratio of the aqueous phase. See table 2 below.

Table 2 raw material components and compounding ratios of examples 12 to 20

Example 21

Step one, in-situ activation.

Taking 80 parts by mass of 0# diesel oil as an oil phase, adding 0.1 part by mass of surfactant dodecyl cyclopentyl amine into the oil phase, magnetically stirring the mixture until the mixture is fully dissolved, then adding 2 parts by mass of hydrophilic nano aluminum oxide particles as nano particles, and then using an ultrasonic cell disruption/vibration instrument to perform ultrasonic in-situ activation for 12-24 hours until the gel strength is 1-2 g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 20 parts by mass of a calcium chloride solution with the concentration of 0.5g/mL into the weak gel state oil phase suspension liquid obtained in the first step to serve as a water phase, then using an ultrasonic cell disruption/vibration instrument, vibrating a head with the diameter of 3mm, working frequency of 20KHz/10W, performing ultrasonic emulsification, emulsifying for 10-30 min, and cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Example 22

Step one, in-situ activation.

Taking 60 parts by mass of 3# white oil as an oil phase, adding 0.05 part by mass of surfactant oleic acid diethanol amide and 0.15 part by mass of 1-aminododecane into the oil phase, magnetically stirring the mixture until the mixture is fully dissolved, then adding 2 parts by mass of hydrophilic nano manganese tetroxide particles as nano particles, magnetically stirring the nano particles in situ for activation, and using a rotor with the diameter of 1 cm-10 cm, the power of a magnetic stirrer being 100W-300W, magnetically stirring the mixture for 6-24 hours until the gel strength is 1-2 g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 30 parts by mass of a calcium chloride solution with the concentration of 1.0g/mL into the weak gel state oil phase suspension liquid obtained in the first step as a water phase, emulsifying by using a homogenizer, wherein the diameter of a metal vibrating rod of the homogenizer is 10mm, the length of the metal vibrating rod is 100mm, the emulsifying time is 10-30 min, and cooling to room temperature by ice bath to obtain the reversible Pickering emulsion.

Examples 23-26 are methods of preparing reversible pickering emulsions stabilized with in situ activated amphiphilic nanoparticles.

Example 23

Step one, in-situ activation.

Taking 100 parts by mass of 3# white oil as an oil phase, adding 0.2 part by mass of surfactant lauroyl diethylenetriamine into the oil phase, performing magnetic stirring until the oil phase is fully dissolved, then adding 2 parts by mass of amphiphilic silicon dioxide nanoparticles as nanoparticles, performing magnetic stirring in-situ activation, using a rotor with the diameter of 1-10 cm, using a magnetic stirrer with the power of 100-300W, performing magnetic stirring for 5-24 hours until the gel strength is1～2g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 100 parts by mass of deionized water serving as a water phase into the weak gel state oil phase suspension in the first step, stirring and emulsifying at a speed of 8000-12000r/min by using a high-speed stirrer for 5-4 h, and cooling to room temperature by ice bath to obtain the reversible Pickering emulsion.

Example 24

Step one, in-situ activation.

Taking 50 parts by mass of 3# white oil as an oil phase, adding 0.1 part by mass of surfactant oleic acid diethanol amide, magnetically stirring until the oil phase is fully dissolved, then adding 1 part by mass of amphiphilic silica nanoparticles as nanoparticles, and then using an ultrasonic cell disruption/vibration instrument to perform ultrasonic dispersion for 5-24 hours until the gel strength is 1-2 g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 50 parts by mass of deionized water serving as a water phase into the weak gel state oil phase suspension in the first step, stirring and emulsifying at a speed of 8000-12000r/min by using a high-speed stirrer for 5-4 h, and cooling to room temperature by ice bath to obtain the reversible Pickering emulsion.

Example 25

Step one, in-situ activation.

Taking 80 parts by mass of 0# diesel oil as an oil phase, adding 0.4 part by mass of surfactant tetradecylamine into the oil phase, performing magnetic stirring until the mixture is fully dissolved, then adding 4 parts by mass of amphiphilic silica nanoparticles as nanoparticles, performing magnetic stirring in-situ activation, using a rotor with the diameter of 1-10 cm, using the power of a magnetic stirrer of 100-300W, performing magnetic stirring for 5-24 hours until the gel strength is 1-2 g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 1g/mL sodium chloride solution with the concentration of 20 parts by mass into the weak gel state oil phase suspension liquid in the first step as a water phase, then using an ultrasonic cell disruption/vibration instrument, vibrating a head with the diameter of 3mm and the working frequency of 20KHz/10W, performing ultrasonic emulsification for 5min-4h, and then cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Example 26

Step one, in-situ activation.

Taking 40 parts by mass of 0# diesel oil as an oil phase, adding 0.3 part by mass of surfactant lauramide dimethylamine, magnetically stirring until the mixture is fully dissolved, then adding 2 parts by mass of amphiphilic alumina nanoparticles as nanoparticles, and ball-milling for 12-24 hours in a polyethylene ball-milling tank by using a milling ball with the diameter of 5mm, 10mm or 20mm until the gel strength is 1-2 g/cm²Stopping, and completing in-situ activation to obtain the weak gel state oil phase suspension.

And step two, emulsification.

Slowly adding 60 parts by mass of deionized water serving as a water phase into the weak gel state oil phase suspension in the first step, emulsifying by using a homogenizer, wherein the diameter of a metal vibrating rod of the homogenizer is 10-50 mm, the length of the metal vibrating rod is 100-450 mm, the frequency is 10000-13500r/min, and the emulsifying time is 10-30 min, and then cooling to room temperature in an ice bath to obtain the reversible Pickering emulsion.

Examples 27-40 are methods of making reversible pickering emulsion type drilling fluids.

Example 27

A preparation method of a reversible Pickering emulsion type drilling fluid is characterized in that 0 part by mass of quaternary ammonium salt modified montmorillonite serving as organic soil, 0 part by mass of quicklime serving as an alkalinity regulator, 3 parts by mass of oxidized asphalt serving as a filtrate reducer, 1 part by mass of plant pine tar serving as a wetting agent and 3 parts by mass of propylene carbonate serving as a cutting agent are respectively added into 100 parts by mass of the reversible Pickering emulsion prepared in example 11, and then a weighting material barite is added to adjust the density to be 1.6g/cm³During the addition process, 800-12000r/min high-speed stirring is carried out, and after the addition is finished, the high-speed stirring is carried out for 20min, so that the reversible Pickering emulsion type well drilling can be obtainedAnd (4) liquid.

Examples 28 to 40 were prepared in the same manner as in example 27 except that the ingredients of the reversible pickering emulsion, the organic soil, the alkalinity regulator, the fluid loss additive, the wetting agent, the shear promoter and the weighting material were mixed in different proportions.

Examples 27-33 provide a soil-free, alkali-free, reversible pickering emulsion-type drilling fluid.

Examples 34-35 provide a reversible pickering emulsion-type drilling fluid without soil.

Examples 36-38 provide an alkali-free reversible pickering emulsion-type drilling fluid.

Example 39 provides a reversible pickering-free emulsion drilling fluid.

Example 40 provides a reversible pickering emulsion-type drilling fluid without soil.

The ingredients and ratios of examples 28 to 40 are shown in Table 3.

Table 3 raw material components and compounding ratios of examples 28 to 40

Description of the drawings: when the reversible Pickering emulsion type drilling fluid is prepared, the fluid loss additive can also use humic acid amide, organic lignite and the like, and can also be a mixture formed by mixing one or two or more of oxidized asphalt, humic acid amide, organic lignite and the like in any proportion; the cutting-extracting agent can be selected from the cutting-extracting agents for common oil-based drilling fluids such as polyacid micromolecule polymers, polyester cutting-extracting agents, polyamide cutting-extracting agents, propylene carbonate, pentaerythritol oleate and the like; the wetting agent can also adopt vegetable oleic acid, lecithin, oleic acid, long-chain alkyl polyoxyethylene ether nonionic surfactant and the like; similar effects to those of embodiments 27 to 40 can be obtained, and further description is omitted here.

The test results of the examples are as follows.

Experiments are carried out on the reversible pickering emulsion or the reversible pickering emulsion type drilling fluid prepared in the embodiment of the invention, and the experimental method and the experimental results are as follows.

1. Rheology of nanoparticle suspensions.

1mL of the weak gel oil phase suspension obtained in the first step of example 1 was taken out, and the rheological characteristics of the nanoparticle suspension were examined by measuring the viscosity of the nanoparticle suspension at different shear rates by using an HAAKEMARSIII rotational rheometer. The experimental results are shown in figure 4.

From the results in fig. 4, it can be seen that the suspension formed by adding the reversible emulsifier for in-situ activation after the nanoparticles are fully dispersed in the oil phase has strong shear dilutability. It is shown that in the dispersed phase, adjacent nanoparticles form nanoparticle aggregates through mutual hydrogen bonds and hydrophobic bonds, and in a certain concentration range, the nanoparticle aggregates are interconnected to form a spatial three-dimensional structure, which can be considered as a weak gel state. In the weak gel state, a three-dimensional structure formed becomes weak at a high shear rate, and the viscosity is lowered, thereby exhibiting shear thinning properties.

The elastic characteristic of a liquid is expressed by the elastic modulus (G ') and the viscous characteristic is expressed by the viscous modulus (G'). The ratio of viscous modulus to elastic modulus reflects the characteristic of the fluid's energy consumption, also known as the loss angle α, tan α ═ G "/G'. Usually when G ">G', the sample exhibits fluid characteristics; and when G'>G ", the sample exhibits solid character; when G' and G "are comparable, it exhibits semi-solid characteristics. The elastic modulus and viscous modulus parameters of the nanoparticle suspension are measured by using an HAAKEMARSIII rotational rheometer to determine the viscoelastic characteristics of the nanoparticle suspension. The nanoparticle suspension was poured into a sample cup of HAAKEMARS1II rotational rheometer and the shear stress was set at 1Pa and the shear rate was set at 10s^-1And carrying out frequency scanning within the range of 0.1-100 Hz, and recording G 'and G' values under different frequencies. The results of the experiment are shown in FIG. 5. As can be seen from the results in the graph, the nanoparticle suspension prepared in example 1 has a storage modulus G 'greater than a loss modulus G ", and G' and G" are independent of the change in frequency. The liquid is more elastic than viscous, the solid characteristic is shown, and the nanoparticle suspension is in a weak gel state.

2. Gel strength of weak gel state oil phase suspensions

The gelling properties of the weak gel state oil phase suspension mainly comprise gelling time, gelling strength and stability of the weak gel. The gel strength can be simply defined as the ability of the gel to resist external damage, and the oil phase suspension containing the nano-particles resists the external damage by the nano-materials, the chemical bonding force in the surfactant and the Van der Waals force and hydrogen bonds between molecules, and the space network structure can obviously improve the strength of the gel.

Fig. 6 shows the relationship between the gel strength of the weak gel state oil phase suspension and the emulsification of the emulsion at different in-situ activation times (not limited to 5-24 hours) in inventive example 1, and the relationship between the gel strength of the oil phase suspension and the emulsification of the emulsion is examined after the emulsification of the oil phase suspension with a certain gel strength. From left to right, the gel strength is less than 1g/cm²(not emulsified) and the gel strength is 1 to 2g/cm²(emulsification) and gel Strength>2g/cm²Appearance of the (demulsified) emulsion.

A gel strength meter manufactured by SHEEN company, UK was used to examine the gel strength of the suspension. Grace M3600 rheometer was able to determine the static shear stress (G) of a gel_10s/G_10min) To characterize the strength of the gel.

Characterization of gel strength of weak gel state oil phase suspensions.

The gel strength of the oil phase suspension in weak gel state is characterized by taking the formulation and method of example 1 as an example, the remaining components are fixed, only the amount of nanoparticles is changed, and the gel strength of the oil phase suspension is measured by using a gel strength meter manufactured by SHEEN company, UK, see Table 4.

TABLE 4 characterization of gel strength of weak gel state oil phase suspensions

When the addition amount of the nano material is 0 part by mass, the gel strength of the oil phase suspension is less than 0.5 although the n-pentylamine is 0.2 part by mass, which indicates that the spatial structure of the oil phase suspension is weak and cannot form effective mechanical barrier to the aqueous phase droplets. The longer the in-situ activation time is, the better the full dispersion among the nano particles in the oil phase solution, the enhanced interaction force among the nano particles, between the nano particles and the oil phase and between the particles and the surfactant, and the corresponding enhanced gel strength of the oil phase suspension. When the gel strength of the oil phase suspension is 1-2 g/cm²The oil phase suspension liquid has a moderate spatial structure, can be effectively adsorbed around the water phase liquid drop to form a certain mechanical barrier, and the emulsion has the highest stability.

Taking the formulation and method of example 1 as an example, the remaining components were fixed and the gel strength of the oil phase suspension was measured using a gel strength meter manufactured by SHEEN corporation, UK, with varying amounts of n-pentylamine only, as shown in Table 5.

TABLE 5 characterization of gel Strength of Weak gel oil phase suspensions

The amido group has stronger adsorbability and can be effectively adsorbed on the surface of the nano-particles. Therefore, when the addition amount of the amine surfactant is increased, the spatial structure of the oil phase suspension is enhanced, and the formation of gel strength is facilitated. When the amount of the amine-based surfactant added is 0, the gel strength of the oil phase suspension is weak and a stable emulsion cannot be formed. When the addition amount of the amine-based surfactant is too high, the gel strength of the oil phase suspension is too high, the space structure force of the oil phase suspension is too high, and the formed emulsion is easy to break.

3. Contact angle of nanoparticles

Taking 10mL of the suspension of the weak gel state oil phase obtained in the first step in the example 1, fully washing the oil phase, carrying out centrifugal drying, taking 2mg of the nano-particles activated in situ by the amino surfactant, and preparing the nano-particles into slices on a tablet machine. The contact angle of the prepared nanoparticle flakes to a water droplet was measured by a KRUSS DSA30S contact angle measuring instrument, and the change in wettability was examined.

The contact angle of the lipophilic nano-silica particles is shown in figure 9, wherein the left graph is before the treatment with the amino surfactant, and the right graph is after the treatment with the amino surfactant.

As can be seen from FIG. 7, the contact angle of the original lipophilic nano-silica particles is 135.1 degrees, and the contact angle of the lipophilic nano-silica particles is reduced to 90.2 degrees after the lipophilic nano-silica particles are in-situ activated in the oil phase by n-pentylamine, which indicates that the short-chain primary amine-based surfactant is adsorbed on the lipophilic nano-silica to reduce the lipophilicity thereof. The contact angle between the oleophylic nano-particles and the water phase after the treatment of short-chain amino groups is 90.2 degrees, and the wettability of the nano-particles is favorable for forming stable water-in-oil Pickering emulsion.

4. Reversibility of in situ activated lipophilic nanoparticle stabilized pickering emulsions.

Acid/base response.

100mL of the reversible Pickering emulsion in example 1 is taken, 1mol/L HCl solution is slowly added into the reversible Pickering emulsion, and after 5min of magnetic stirring and mixing, the pH value of the emulsion is reduced to about 5, the water-in-oil emulsion is changed into oil-in-water emulsion, and the conductivity is increased. Adding 1mol/L NaOH solution, magnetically stirring, mixing, increasing the pH value of the emulsion to 7.5, changing the oil-in-water emulsion into a water-in-oil emulsion, and reducing the conductivity to 0. This repetition allows for multiple reversals.

FIG. 8 is a graph of the appearance of an acid/base stimulus responsive reversible pickering emulsion of example 1 of the present invention; FIG. 9 is a graph of the change in conductivity of the reversible pickering emulsion acid/base stimulation response of example 1 of the present invention.

As shown in the attached figures 8 and 9, after the oleophylic nano silicon dioxide particles are activated in situ by n-pentylamine, the formed water-in-oil type Pickering emulsion has reversibility, and after the acid liquid is added, the emulsion is changed from a water-in-oil emulsion to an oil-in-water emulsion, so that the conductivity is increased; after addition of the alkali solution, the oil-in-water emulsion becomes a water-in-oil emulsion and the conductivity decreases. The reversible Pickering emulsion formed by the oleophylic nano silicon dioxide particles after in-situ activation by n-pentylamine does not have the demulsification phenomenon, and can be reversed for multiple times by acid contact and alkali contact.

5. In-situ activated hydrophilic nanoparticle stabilized Pickering emulsion W/O emulsion morphology

FIG. 10 is an appearance diagram of the reversible Pickering emulsion of example 11 of the present invention, which can be seen as a milky white emulsion.

FIG. 11 is a particle size distribution diagram of the reversible Pickering emulsion of example 11 of the present invention, which shows that the reversible Pickering emulsion has a narrow particle size distribution, a polydispersity of less than 2, and an average particle size of 5 to 40 μm.

Table 6 shows the particle size distribution data for the reversible pickering emulsion of example 11.

TABLE 6 reversible Pickering emulsion particle size distribution data

D₁₀(μm)	D₅₀(μm)	D₉₀(μm)	Average particle diameter (μm)	Geometric dispersion (. mu.m)²)
					16.3132	32.3132	49.7371	33.0457	1.1065

6. Reversibility of in situ activated hydrophilic nanoparticle stabilized Pickering emulsions

The method comprises the following operation steps: 100mL of the reversible pickering emulsion of example 11 was charged with 100mL of CO per minute ₂1 min; after fully mixing, the pH value of the solution is reduced to 5.5, the water-in-oil emulsion is changed into oil-in-water emulsion, and the conductivity is increased; continuously introducing N with the flow rate of 100ml per minute₂After 1min and thorough mixing, the pH value of the solution is increased to 7.5, the oil-in-water emulsion becomes a water-in-oil emulsion, and the conductivity is reduced to 0. This repetition allows for multiple reversals. FIG. 12 shows CO in example 11 of the present invention₂/N₂An appearance map of the responsive reversible pickering emulsion; FIG. 13 shows a reversible Pickering emulsion CO according to example 11 of the invention₂/N₂Graph of the change in conductivity of the stimulus response.

6. Reversibility of in situ activated amphiphilic nanoparticle stabilized Pickering emulsions

Acid contact/base contact:

100mL of the reversible Pickering emulsion of example 23 was gradually added to 1mol/L HCl solution, and after magnetic stirring and mixing for 5min, the pH of the emulsion was reduced to about 4. Then adding 1mol/L NaOH solution, and after magnetic stirring and mixing, increasing the pH value of the emulsion to 8. FIG. 14 is a graph showing the change in conductivity during acid contact of a reversible pickering emulsion of example 23 of the present invention; FIG. 15 is a graph of the change in conductivity during alkaline contact of the reversible pickering emulsion of example 23 of the present invention.

As can be seen from fig. 14, after the amphiphilic nano-silica particles are activated in situ by the amine-based surfactant, the formed water-in-oil type pickering emulsion can be contacted with acid. When the addition of 1mol of acid liquor is 0.4%, the conductivity of the emulsion is increased, the breaking voltage is reduced, and the Pickering emulsion is changed from water-in-oil emulsion to oil-in-water emulsion. As can be seen from fig. 14, after the amphiphilic nano-silica particles are activated in situ by lauroyl diethylenetriamine, the formed water-in-oil type pickering emulsion can be contacted with alkali. When the addition of 1mol of alkali liquor is 0.8%, the conductivity of the emulsion is reduced, the demulsification voltage is increased, and the voltage is restored to 775V. Therefore, the amphiphilic nano silicon dioxide particles form reversible Pickering emulsion under the action of lauroyl diethylenetriamine, and the lauroyl diethylenetriamine cannot form stable emulsion alone under low concentration.

Because the contact angle between the amphiphilic nano material and the interface is 95 degrees, the water-in-oil Pickering emulsion can be independently stabilized. Thus, as a comparative experiment, the reversibility of a pickering emulsion in which the same amphiphilic nano silica particles are individually stabilized was examined without the addition of a long chain amine-based surfactant. 100 parts of white oil are taken, 2g of amphiphilic nano silicon dioxide particles prepared by a gas method are added, and a magnetic stirrer is used for 12 hours. Slowly adding 100 parts of deionized water, emulsifying by using a high-speed stirrer, emulsifying at 12000r/min for 20min, and cooling to room temperature. Obtaining the Pickering emulsion with the independent and stable amphiphilic nano material.

100mL of the Pickering emulsion with the amphiphilic nano-silica particles stable independently is prepared, 1mol/L of HCl solution is gradually added, and after magnetic stirring and mixing for 5min, the pH value of the emulsion is reduced to about 4. Then adding 1mol/L NaOH solution, and after magnetic stirring and mixing, increasing the pH value of the emulsion to 7. See fig. 16 and 17. FIG. 16 is a graph of the change in conductivity during acid contact of an amphiphilic nanoparticle stabilized Pickering emulsion without in situ activation; fig. 17 is a graph of the change in conductivity during base contact of an amphiphilic nanoparticle stabilized pickering emulsion without in situ activation.

As can be seen from FIG. 16, after the Pickering emulsion stabilized by the amphiphilic nano silica particles alone is added with acid, the demulsification voltage of the water-in-oil emulsion is reduced, and the water-in-oil Pickering emulsion is demulsified. As can be seen from FIG. 17, the stable Pickering emulsion with amphiphilic nano-silica particles alone can not be recovered after demulsification by adding acid and then adding equimolar alkali solution. The demulsification voltage and conductivity are very low. The picryline emulsion stabilized by the amphiphilic nano silica particles alone has no reversibility, which is caused by the fact that the emulsion formed by the nano particles in the emulsion cannot be changed due to the lipophilicity of the nano particles in the emulsion. Therefore, a very small amount of amine-based surfactant needs to be added to realize the reversibility of the pickering emulsion.

7. Soil-phase-free and alkali-free reversible Pickering emulsion type drilling fluid performance

The data for the soil-free, alkali-free reversible pickering emulsion drilling fluid of example 27, before and after being aged 180 ℃/16h reversal, is shown in table 7:

TABLE 7 soil-phase-free, alkali-free reversible Pickering emulsion-type drilling fluid Performance

After the soilless and alkali-free reversible Pickering emulsion type drilling fluid with the density of 1.6 is aged at the high temperature of 180 ℃/16h, acid is added, the water-in-oil drilling fluid can be reversely converted into oil-in-water drilling fluid, and after alkali is added, the oil-in-water drilling fluid can be reversely converted into oil-in-water drilling fluid. No separation and demulsification of barite occurs, the separation amount of the drilling fluid is less than 5% in a water-in-oil state and an oil-in-water state, and the filtration loss is less than 5 mL. The filter cake can be dissolved by acid, which is convenient for removing the filter cake in the later period.

The data for the soil-free, alkali-free reversible pickering emulsion drilling fluid of example 29, before and after being aged at 200 ℃/16h is shown in table 8:

TABLE 8 Earth-phase-free, alkali-free reversible Pickering emulsion-type drilling fluid Performance

When 7% of conventional stripping and cutting agent is adopted, the density of the reversible Pickering emulsion type drilling fluid can reach 1.7g/cm at most³. After high-temperature aging at 200 ℃/16h, the water-in-oil drilling fluid can be converted into an oil-in-water drilling fluid by adding acid, and the oil-in-water drilling fluid can be converted into an oil-in-water drilling fluid by adding alkali, so that the demulsification voltage is not lost. The drilling fluid can be repeatedly used after being contacted with acid and alkali. No separation and demulsification of barite occurs, the separation amount of the drilling fluid is less than 5% in a water-in-oil state and an oil-in-water state, and the filtration loss is less than 10 mL.

8. Reversible pickering emulsion type drilling fluid performance without soil or cutting agent

The data for the reversible pickering emulsion drilling fluid without a soil phase and a shear strength enhancing agent of example 40 before and after aging at 200 ℃/16h is shown in table 9:

TABLE 9 reversible Pickering emulsion drilling fluid Performance without soil phase and shear strength enhancing agent

Under the condition of no soil phase and no shear strength improving agent, the density of the reversible pickering emulsion can reach 1.4g/cm³The suspension of the reversible pickering emulsion is now provided primarily by its internal structure. The Pickering emulsion prepared from the oil phase suspension in the weak gel state has high structural viscosity, strong shearing and diluting capability and strong rock carrying and suspending capacity. After the high temperature of 200 ℃/16h, the drilling fluid can realize the reversion of the water-in-oil state and the oil-in-water state, and no barite precipitation and demulsification phenomena occur in the reversion process.

9. Suspending power of alkali-free reversible pickering emulsion drilling fluid

20g of sandstone (80 mesh), 20g of nano-barite powder, 20g of api barite powder, and 20g of shale (80 mesh) were added to the alkali-free reversible pickering emulsion prepared in example 23, and after mixing uniformly, the mixture was left to stand for 1 month without solid phase precipitation and precipitation. The reversible pickering emulsion type drilling fluid has extremely strong suspended solid phase capacity.

FIG. 18 is a graph of the suspending power of the reversible Pickering emulsion drilling fluid of example 1 on a solid phase, from left to right in the order: sandstone, nano-barite powder, API barite powder, shale, and blank emulsion.

10. Filter cake removal for soil-phase-free, alkali-free reversible pickering emulsion drilling fluids

In the soil-phase-free, alkali-free reversible pickering emulsion-type drilling fluid prepared in example 27, the filter cake taken out at high temperature and high pressure was completely removed after being immersed in 1mol/L hydrochloric acid solution for 10 min. The filter cake of the reversible Pickering emulsion drilling fluid is easy to remove, and the subsequent problem caused by the difficulty in removing the filter cake during well cementation is avoided.

FIG. 19 is a graph of the filter cake removal capacity of a reversible pickering emulsion drilling fluid (left: before acid treatment; right: after acid treatment).

The emphasis of each embodiment in the present specification is on the difference from the other embodiments, and the same and similar parts among the various embodiments may be referred to each other.

The technology provided by the present invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are set forth only to help understand the method and its core ideas of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A reversible pickering emulsion characterized by: comprises an oil phase, a water phase and nano-particles which are activated in situ by an amino surfactant or an amino derivative surfactant and are used as a stabilizing agent;

the nano particle aggregation body is formed by the mutual coalescence of nano particles in an oil phase through the strong adsorption action of amino and the interaction of a hydrophobic bond and a hydrogen bond;

the reversible pickering emulsion is prepared by the following method:

step one, in-situ activation is carried out,

adding an amine surfactant or an amine derivative surfactant and nanoparticles into the oil phase, and activating in situ to form a weak gel state oil phase suspension with the gel strength of 1-2 g/cm²；

Step two, emulsifying,

slowly adding the aqueous phase into the weak gel state oil phase suspension obtained in the first step, and emulsifying to form reversible pickering emulsion;

wherein the in-situ activation method comprises magnetic stirring, ball milling and ultrasonic dispersion in-situ activation, and the in-situ activation time is 5-24 hours;

the emulsifying method comprises stirring and emulsifying by a high-speed stirrer, emulsifying by a homogenizer or ultrasonic emulsifying, wherein the emulsifying time is 5min-4 h;

the reversible pickering emulsion comprises 40-80 parts by mass of an oil phase, 1-4 parts by mass of nanoparticles, 0.01-1 part by mass of an amino surfactant and 20-60 parts by mass of a water phase.

2. The reversible pickering emulsion of claim 1, characterized in that: the oil phase is one or more of 0# diesel oil, 3# white oil, gassed oil, aviation kerosene, biodiesel, toluene, benzene, n-hexane-docosane or isomers thereof, cyclohexane, methyl myristate, undecanol and isopropyl myristate;

the water phase is pure water, tap water or one of sodium carbonate solution, sodium chloride solution, calcium chloride solution and magnesium chloride solution with the concentration of 0.01-1 g/mL;

the nano particles comprise one or more of lipophilic, hydrophilic or amphiphilic nano silicon dioxide, nano aluminum oxide, nano zinc oxide, nano titanium oxide, nano zirconium oxide, nano magnesium oxide, nano ferroferric oxide, nano tin oxide and nano mangano-manganic oxide nano materials;

the amino surfactant is primary amine, secondary amine or tertiary amine surfactant, and the amino derivative surfactant is primary amine, secondary amine, tertiary amine or amino derivative surfactant thereof;

when the nano-particles are lipophilic nano-particles, a short-chain amine-based surfactant or a short-chain amine derivative surfactant is adopted;

when the nano-particles are hydrophilic or amphiphilic nano-particles, the amine-based surfactant or the derivative thereof is a long-chain amine-based surfactant or a long-chain amine-based derivative surfactant;

wherein the alkyl chain of the short-chain amino surfactant or the short-chain amino derivative surfactant is C₃～C₆Straight chainThe functional groups of the alkyl, branched alkyl and amino derivatives are one or more of the following: piperidines, anilines, benzylamines, cyclic amines, pyrrolidinylamines, tertiary amines, alcoholamines, amides, polyamines, hydroxyethyl amines;

the alkyl chain of the long-chain amino surfactant or the long-chain amino derivative surfactant is C₆～C₃₀The functional group of the amino group is one or more of piperidine, aniline, benzylamine, cyclic amine, pyrrolidinylamine, tertiary amine, alcohol amine, amide, polyamine and hydroxyethyl amine.

3. The reversible pickering emulsion of claim 2, characterized in that:

the reversible pickering emulsion is prepared by the following method:

adding a lipophilic nano material into an oil phase, fully dispersing by using mechanical stirring, ball milling or ultrasonic waves, then adding a short-chain amino surfactant or a short-chain amino derivative surfactant, and performing in-situ activation by using magnetic stirring, a ball milling method and ultrasonic dispersion to form a weak gel-state oil phase suspension;

4. The reversible pickering emulsion of claim 2, characterized in that:

the reversible pickering emulsion is prepared by the following method:

adding a long-chain amino surfactant or a long-chain amino derivative surfactant into an oil phase, mixing, then adding hydrophilic nanoparticles or amphiphilic nanoparticles, and dispersing and activating in situ by using a magnetic stirring method, a ball milling method or ultrasonic waves to form a weak gel state oil phase suspension;

5. A reversible Pickering emulsion type drilling fluid is characterized in that: the reversible pickering emulsion comprises 100 parts by mass of the reversible pickering emulsion as claimed in any one of claims 1 to 4, 0 to 3 parts by mass of organic soil, 0 to 4 parts by mass of an alkalinity regulator, 1 to 5 parts by mass of a filtrate reducer, 0 to 7 parts by mass of a shear promoter, 0 to 3 parts by mass of a wetting agent and 0 to 77 parts by mass of a weighting material.

6. The reversible pickering emulsion-type drilling fluid of claim 5, wherein: the content of the organic soil is 0 part by mass, and the content of the alkalinity regulator is 0 part by mass.

7. A phase inversion method of reversible Pickering emulsion or reversible Pickering emulsion type drilling fluid is characterized in that: a reversible Pickering emulsion as claimed in any one of claims 1 to 4 or a reversible Pickering emulsion type drilling fluid as claimed in claim 5 or 6, using acid/base stimulation response or CO₂/N₂And (5) responding to the stimulus, and finishing the interconversion of the W/O type emulsion and the O/W type emulsion.