阅读说明：本技术 一种酸化解堵体系及其制备方法 (Acidizing blockage removal system and preparation method thereof ) 是由 荣新明 张洪菁 王春林 李翔 奎智斌 冯浦涌 杜勋 丁文刚 童志能 吴广 刘洋 于 2021-08-31 设计创作，主要内容包括：一种酸化解堵体系及其制备方法,所述酸化解堵体系为W/O/W型多重乳状液,由W/O型初相和外水相组成,所述W/O型初相包括体积比为(5-2):(5-8)的油相和内水相,所述内水相包括,以所述内水相的总质量计,质量百分比为5％-20％的酸、0.5％-2％的缓蚀剂和0.5％-2％的螯合剂；所述油相包括,以所述油相的总质量计,质量百分比为0.3％-3％的疏水纳米二氧化硅颗粒、1％-3％的表面活性剂和余量油；所述外水相包括,以所述外水相的总质量计,质量百分比为0.1％-0.5％的水溶性乳化剂。本申请可降低地层原油黏度,提高分流效率,对非均质储层有更好的解堵效果,降低油相用量和成本,有利于提高分流解堵效果。(An acidification plug removal system and a preparation method thereof, wherein the acidification plug removal system is a W/O/W type multiple emulsion and consists of a W/O type initial phase and an external water phase, the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of (5-2) to (5-8), and the internal water phase comprises, by mass, 5-20% of acid, 0.5-2% of corrosion inhibitor and 0.5-2% of chelating agent based on the total mass of the internal water phase; the oil phase comprises, by mass, 0.3% -3% of hydrophobic nano silica particles, 1% -3% of a surfactant and the balance oil; the external water phase comprises, by mass, 0.1% to 0.5% of a water-soluble emulsifier, based on the total mass of the external water phase. The method can reduce the viscosity of crude oil in the stratum, improve the flow distribution efficiency, have better blockage removing effect on the heterogeneous reservoir, reduce the oil phase consumption and the cost, and be favorable for improving the flow distribution blockage removing effect.)

1. An acidification deblocking system, wherein the acidification deblocking system is a W/O/W type multiple emulsion, and the volume ratio of the acidification deblocking system to the W/O/W type multiple emulsion is (5-1): (5-9) a W/O type primary phase and an external aqueous phase, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of (5-2) to (5-8), wherein:

the inner water phase is acid liquid and comprises, by mass, 5% -20% of acid, 0.5% -2% of corrosion inhibitor, 0.5% -2% of chelating agent and the balance of water, based on the total mass of the inner water phase;

the oil phase comprises, by mass, 0.3% -3% of hydrophobic nano silica particles, 1% -3% of a surfactant and the balance oil, based on the total mass of the oil phase;

the external water phase comprises, by mass, 0.1-0.5% of a water-soluble emulsifier and the balance of water, wherein the water-soluble emulsifier is a combination of alkanolamide and dodecyl dimethyl amine oxide;

the particle size of the hydrophobic nano silicon dioxide particles is 20-50 nm.

2. The acidizing unplugging system of claim 1, the hydrophobic nano silica particles having a particle size of 30 nm.

3. The acidizing plug removal system according to claim 2, which consists of a W/O type primary phase and an outer water phase in a volume ratio of 4:6, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of 3:7, wherein:

the inner water phase is acid liquid, and comprises 15% of acid, 1% of corrosion inhibitor, 1% of chelating agent and the balance of water by mass percent based on the total mass of the inner water phase;

the oil phase comprises 3% of hydrophobic nano silica particles, 2% of surfactant and the balance oil by mass percentage based on the total mass of the obtained oil phase;

the outer water phase comprises 0.3% of water-soluble emulsifier and the balance of water by mass percent based on the total mass of the obtained outer water phase, the water-soluble emulsifier is the combination of alkanolamide and dodecyl dimethyl amine oxide, and the mass ratio of the alkanolamide to the dodecyl dimethyl amine oxide is 8: 2.

4. The acidizing unplugging system of any of claims 1-3, the surfactant is an oil-soluble surfactant that is a Span-based surfactant, preferably Span 60.

5. The acidizing unplugging system of any of claims 1-3, the oil being a styrene tar.

6. The acidizing unplugging system of any of claims 1-3, the acid being hydrochloric acid.

7. The acidizing unblocking system according to any one of claims 1-3, wherein the corrosion inhibitor is a commercially available Mannich base, and the Mannich base is copolymerized by n-hexylamine, acetophenone and paraformaldehyde.

8. The acidizing unplugging system of any of claims 1-3, the chelating agent is hydroxyethylidene diphosphonic acid.

9. A method of making an acidizing unplugging system according to any of claims 1 to 8, the method comprising the steps of:

(1) preparing an oil phase: ultrasonically dispersing hydrophobic nano silicon dioxide particles and a surfactant in oil to obtain an oil phase;

(2) preparing an internal water phase: dissolving acid, a corrosion inhibitor and a chelating agent in water to obtain an internal water phase;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of (5-2): (5-8) homogenizing, stirring and mixing at a high speed to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving a water-soluble emulsifier in water to obtain an external water phase;

(5) and (3) mixing the W/O type initial phase in the step (3) with the external water phase in the step (4) according to the volume ratio of (5-1): and (5-9) homogenizing, stirring and mixing at a high speed to obtain a W/O/W type multiple emulsion acidification blockage removal system.

10. The method for preparing an acidification and blockage relieving system as claimed in claim 9, wherein the high-speed homogeneous stirring rotation speed in step (3) is 7000-9000r/min, and the time is 6-10 min.

11. The method for preparing an acidification and blockage relieving system as claimed in claim 9, wherein in the step (5), the high-speed homogeneous stirring rotation speed is 2000-4000r/min, and the time is 8-15 min.

Technical Field

The invention relates to a W/O/W type multiple emulsion acidizing and plug removing system and a preparation method thereof, belonging to the technical field of oil field production increase.

Background

In the multiple acidification treatment measures adopted in the same well layer, due to the difference of the permeability of the reservoir, a large amount of acid liquid enters the high-permeability layer, so that the low-permeability reservoir cannot be subjected to acidification treatment, the heterogeneity of the reservoir is enhanced, and the crude oil in the low-permeability reservoir is difficult to extract. Therefore, the key of successful repeated acidification is to realize the diversion of the acid liquor to the low-permeability layer and improve the blockage removal efficiency of the low-permeability layer.

The emulsion acid is an emulsion system prepared based on acid liquor, a W/O type emulsion is mainly used, the emulsion is used for wrapping the acid liquor to realize the slow release of the acid liquor, but the traditional W/O type emulsion has overhigh viscosity and overlarge ground injection pressure and has higher requirements on ground equipment.

Aiming at the defects of the prior art, a W/O/W type multiple emulsion acidification blockage removal system and a preparation method of the W/O/W type multiple emulsion acidification blockage removal system are urgently needed in the field.

Disclosure of Invention

The acidification deblocking system is a W/O/W type multiple emulsion, and is a water-in-oil-in-water type multiple emulsion formed by a surfactant, hydrophobic nano silica particles, oil, an acid solution and the like, the system can improve the distribution efficiency of the deblocking system by means of the Jamin effect of the multiple emulsion, plays a role in uniformly distributing acid, effectively overcomes the defects of the acid solution deblocking system in the prior art, has better reformation performance on a hypotonic reservoir in a reservoir with larger range of difference, and can realize deep acidification deblocking of a stratum by means of the action of slowly releasing the acid solution by means of the multiple emulsion. Compared with an oil-in-water emulsion system or a water-in-oil system in the prior art, the acidification blockage removing system can greatly reduce the using amount of an oil phase and the cost of the blockage removing system, and meanwhile, due to the fact that multiple interfaces exist in the blockage removing system, the Jamin effect of the acidification blockage removing system is greatly improved, and the acidification blockage removing system is more beneficial to improving the blockage removing efficiency of the blockage removing system.

In order to achieve the purpose of the application, the application provides an acidification deblocking system, wherein the acidification deblocking system is a W/O/W type multiple emulsion, and the acidification deblocking system is composed of a W/O/W type multiple emulsion with a volume ratio of (5-1): (5-9) a W/O type primary phase and an external aqueous phase, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of (5-2) to (5-8), wherein:

the inner water phase is acid liquid and comprises, by mass, 5% -20% of acid, 0.5% -2% of corrosion inhibitor, 0.5% -2% of chelating agent and the balance of water, based on the total mass of the inner water phase;

the oil phase comprises, by mass, 0.3% -3% of hydrophobic nano silica particles, 1% -3% of a surfactant and the balance oil, based on the total mass of the oil phase;

the external water phase comprises 0.1-0.5% of water-soluble emulsifier and the balance of water by mass percent based on the total mass of the obtained external water phase, wherein the water-soluble emulsifier is the combination of alkanolamide and dodecyl dimethyl amine oxide; the particle size of the hydrophobic nano silicon dioxide particles is 20-50nm, and preferably, the particle size of the hydrophobic nano silicon dioxide particles is 30 nm.

In an exemplary embodiment, the mass ratio of the alkanolamide to the dodecyldimethylamine oxide is 8: 2.

In an exemplary embodiment, the acidizing unplugging system consists of a W/O type primary phase and an external water phase in a volume ratio of 4:6, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of 3:7, wherein:

the inner water phase is acid liquid, and comprises 15% of acid, 1% of corrosion inhibitor, 1% of chelating agent and the balance of water by mass percent based on the total mass of the inner water phase;

the oil phase comprises 3% of hydrophobic nano silica particles, 2% of surfactant and the balance oil by mass percentage based on the total mass of the obtained oil phase;

the outer water phase comprises 0.3% of water-soluble emulsifier and the balance of water by mass percent based on the total mass of the obtained outer water phase, the water-soluble emulsifier is a combination of alkanolamide and dodecyl dimethyl amine oxide, and the mass ratio of the alkanolamide to the dodecyl dimethyl amine oxide is 8: 2.

In an exemplary embodiment, in the oil phase, the surfactant is an oil soluble surfactant, preferably a Span-type surfactant, in particular Span 60; the oil is styrene tar.

In an exemplary embodiment, the acid is hydrochloric acid diluted with 38% by mass of analytically pure hydrochloric acid in the internal aqueous phase; the corrosion inhibitor is a commercially available Mannich base, and the Mannich base is synthesized by n-hexylamine, acetophenone and paraformaldehyde in a copolymerization manner; the chelating agent is hydroxyethylidene diphosphonic acid.

In an exemplary embodiment, in the external aqueous phase, the alkanolamide is coconut fatty acid diethanolamide, i.e., detergent-6501.

The application provides a preparation method of an acidification de-blocking system, wherein the acidification de-blocking system is a W/O/W type multiple emulsion, and the method comprises the following steps:

(1) preparing an oil phase: ultrasonically dispersing hydrophobic nano silicon dioxide particles and a surfactant in oil to obtain an oil phase;

(2) preparing an internal water phase: dissolving acid, a corrosion inhibitor and a chelating agent in water to obtain an internal water phase;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of (5-2): (5-8) homogenizing, stirring and mixing at a high speed to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving a water-soluble emulsifier in water to obtain an external water phase;

(5) and (3) mixing the W/O type initial phase in the step (3) with the external water phase in the step (4) according to the volume ratio of (5-1): and (5-9) homogenizing, stirring and mixing at a high speed to obtain a W/O/W type multiple emulsion acidification blockage removal system.

In an exemplary embodiment, the high-speed homogenizing and stirring speed in step (3) is 7000-9000r/min, and the time is 6-10 min.

In an exemplary embodiment, in step (5), the high-speed homogenizing and stirring speed is 2000-4000r/min, and the time is 8-15 min.

Compared with the prior art, the invention has the following advantages:

1. the outer water phase of the W/O/W type multiple emulsion acidification blockage removal system is water, the outer water phase contains a water-soluble emulsifier which is a combination of an emulsifier alkanolamide and dodecyl dimethyl amine oxide, the water-soluble emulsifier is short-chain micromolecules, the water phase and the oil phase cannot be sheared and damaged, in addition, the viscosity of the emulsion is not high, so that the shearing action has no influence on viscosity loss of the emulsion, and meanwhile, the shearing action generated by high flow rate is beneficial to dispersion and stabilization of the emulsion, so the system disclosed by the invention overcomes the problem that the injection pressure of water-in-oil type emulsified acid is too high in the injection process; the multiple emulsion has low viscosity, can reduce the viscosity at high shear rate and is easy to inject, and the multiple emulsion has a Jamin effect, so that the seepage resistance in a high-permeability layer can be increased, the acid liquor can be favorably diverted to a medium-low permeability layer, and the flow distribution efficiency of a subsequent blockage removal system can be improved.

2. The efficiency of the traditional oil-in-water emulsion or water-in-oil emulsion is greatly reduced after the emulsion breaking in the stratum, and the W/O/W type multiple emulsion in the system has higher flow dividing capacity after being converted into the oil-in-water emulsion or the water-in-oil emulsion.

3. The water-soluble emulsifiers, namely alkanolamide and dodecyl dimethyl amine oxide, contained in the external water phase of the W/O/W type multiple emulsion plugging removal system can improve the stability of the W/O/W type multiple emulsion, has excellent interfacial properties, can reduce the interfacial tension between the plugging removal system and the crude oil in the stratum, cleans the crude oil attached to the surface of the rock, and realizes the effective reaction of acid liquor and the rock.

4. The W/O/W type multiple emulsion blockage relieving system has the advantages that the oil-water interface is a multiple interface, the water-in-oil emulsion exists after the multiple emulsion is demulsified and separated, a certain shunting effect is still achieved, meanwhile, the internal water phase of the water-in-oil emulsion is acid liquid, the system can enter the deep part of a stratum for demulsification, the deep part acidification is achieved, the reaction rate of the acid liquid and rock in a near-wellbore area is reduced, and the deep blockage relieving acidification is achieved.

Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the application. Other advantages of the present application may be realized and attained by the instrumentalities and methods described in the specification.

Detailed Description

The present application describes embodiments, but the description is illustrative rather than limiting and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the embodiments described herein.

The application provides an acidification de-plugging system, which is a W/O/W type multiple emulsion and comprises the following components in volume ratio of (5-1): (5-9) a W/O type primary phase and an external aqueous phase, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of (5-2) to (5-8), wherein:

the inner water phase is acid liquid and comprises, by mass, 5% -20% of acid, 0.5% -2% of corrosion inhibitor, 0.5% -2% of chelating agent and the balance of water, based on the total mass of the inner water phase;

the oil phase comprises, by mass, 0.3% -3% of hydrophobic nano silica particles, 1% -3% of a surfactant and the balance oil, based on the total mass of the oil phase; the particle size of the hydrophobic nano silicon dioxide particles is 20-50nm, and preferably, the particle size of the hydrophobic nano silicon dioxide particles is 30 nm;

the external water phase comprises, by mass, 0.1-0.5% of a water-soluble emulsifier and the balance of water, wherein the water-soluble emulsifier is a combination of alkanolamide and dodecyl dimethyl amine oxide.

In an exemplary embodiment, the mass ratio of the alkanolamide to the dodecyldimethylamine oxide is 8: 2.

In an exemplary embodiment, the acidizing unplugging system consists of a W/O type primary phase and an external water phase in a volume ratio of 4:6, wherein:

the W/O type initial phase comprises an oil phase and an internal water phase in a volume ratio of 3:7, wherein:

the inner water phase is acid liquid, and comprises 15% of acid, 1% of corrosion inhibitor, 1% of chelating agent and the balance of water by mass percent based on the total mass of the inner water phase;

the oil phase comprises 3% of hydrophobic nano silicon dioxide particles, 2% of surfactant and the balance of oil by mass percentage, wherein the optimal particle size of the hydrophobic nano silicon dioxide particles is 30 nm;

the outer water phase comprises 0.3% of water-soluble emulsifier and the balance of water by mass percent based on the total mass of the obtained outer water phase, the water-soluble emulsifier is a combination of alkanolamide and dodecyl dimethyl amine oxide, and the mass ratio of the alkanolamide to the dodecyl dimethyl amine oxide is 8: 2;

in an exemplary embodiment, in the oil phase, the surfactant is an oil soluble surfactant, preferably a Span-type surfactant, in particular Span 60; the oil is styrene tar.

In an exemplary embodiment, the acid is hydrochloric acid and the hydrochloric acid is made diluted with 38% by mass of analytically pure hydrochloric acid in the internal aqueous phase; the corrosion inhibitor is a commercially available Mannich base, and the Mannich base is synthesized by n-hexylamine, acetophenone and paraformaldehyde in a copolymerization manner; the chelating agent is hydroxyethylidene diphosphonic acid.

In an exemplary embodiment, in the external aqueous phase, the alkanolamide is coconut fatty acid diethanolamide, i.e., detergent-6501.

The application provides a preparation method of an acidification de-blocking system, wherein the acidification de-blocking system is a W/O/W type multiple emulsion, and the method comprises the following steps:

(1) preparing an oil phase: ultrasonically dispersing hydrophobic nano silicon dioxide particles and a surfactant in oil to obtain an oil phase;

(2) preparing an internal water phase: dissolving acid, a corrosion inhibitor and a chelating agent in water to obtain an internal water phase;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of (5-2): (5-8) homogenizing, stirring and mixing at a high speed to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving a water-soluble emulsifier in water to obtain an external water phase;

(5) and (3) mixing the W/O type initial phase in the step (3) with the external water phase in the step (4) according to the volume ratio of (5-1): and (5-9) homogenizing, stirring and mixing at a high speed to obtain a W/O/W type multiple emulsion acidification blockage removal system.

In an exemplary embodiment, the high-speed homogenizing and stirring speed in step (3) is 7000-9000r/min, and the time is 6-10 min.

In an exemplary embodiment, in step (5), the high-speed homogenizing and stirring speed is 2000-4000r/min, and the time is 8-15 min.

The present invention is further illustrated by, but is not limited to, the following specific examples.

The starting materials used in the examples are conventional and commercially available, wherein the Mannich bases are available from Kyodo Petroleum science and technology development Inc., type: SA 1-3; the hydrophobic nano silica particle product brand: degussa, characteristics: drainage, type: R812S. The methods are prior art unless otherwise specified.

Example 1.

The preparation method of the W/O/W type multiple emulsion acidification de-plugging system comprises the following steps:

(1) preparing an oil phase: dissolving surfactant Span60 and hydrophobic nano silicon dioxide particles in oil through ultrasonic dispersion to obtain an oil phase; wherein, based on the total mass of the obtained oil phase, the mass fraction of Span60 is 3%, the mass fraction of the hydrophobic nano-silica particles is 0.3%, and the particle size of the hydrophobic nano-silica particles is 30 nm; the oil is styrene tar;

(2) preparing an internal water phase: based on the total mass of the obtained internal water phase, dissolving hydrochloric acid with the mass fraction of 20%, corrosion inhibitor with the mass fraction of 0.5% and hydroxyethylidene diphosphonic acid with the mass fraction of 0.5% in water to obtain the internal water phase; the hydrochloric acid is prepared by diluting 38% of analytically pure hydrochloric acid, the corrosion inhibitor is a commercially available Mannich base, and the Mannich base is synthesized by n-hexylamine, acetophenone and paraformaldehyde in a copolymerization manner;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of 5: 5, placing the mixture in a beaker, and homogenizing and stirring the mixture for 10min at the rotating speed of 7000r/min to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving alkanolamide and dodecyl dimethyl amine oxide in a mass ratio of 8:2 in water to obtain an external water phase, wherein the mass fraction of the combination of the alkanolamide and the dodecyl dimethyl amine oxide in the external water phase is 0.1% based on the total mass of the obtained external water phase;

(5) and homogenizing and stirring the W/O type primary phase and the external water phase at the volume ratio of 1:9 for 8min at the rotating speed of 4000r/min to obtain the W/O/W type multiple emulsion unblocking system.

Example 2.

The preparation method of the W/O/W type multiple emulsion acidification de-plugging system comprises the following steps:

(1) preparing an oil phase: dissolving surfactant Span60 and hydrophobic nano silicon dioxide particles in oil through ultrasonic dispersion to obtain an oil phase; wherein, based on the total mass of the obtained oil phase, the mass fraction of Span60 is 1%, the mass fraction of hydrophobic nano silica particles is 0.3%, and the particle size of the hydrophobic nano silica particles is 30 nm; the oil is styrene tar;

(2) preparing an internal water phase: dissolving 5% of hydrochloric acid, 2% of corrosion inhibitor and 2% of hydroxyethylidene diphosphonic acid in water by mass percent based on the total mass of the obtained internal water phase to obtain the internal water phase, wherein the hydrochloric acid is prepared by diluting 38% of analytically pure hydrochloric acid, the corrosion inhibitor is commercially available Mannich base, and the Mannich base is copolymerized and synthesized by n-hexylamine, acetophenone and paraformaldehyde;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of 2: 8, placing the mixture in a beaker, and homogenizing and stirring the mixture for 6min at the rotating speed of 9000r/min to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving alkanolamide and dodecyl dimethyl amine oxide in a mass ratio of 8:2 in water to obtain an external water phase; wherein, the mass fraction of the alkanolamide and the dodecyl dimethyl amine oxide in the external water phase is 0.5 percent based on the total mass of the obtained external water phase;

(5) mixing the W/O type initial phase and the external water phase according to the volume ratio of 5: 5 is homogenized and stirred for 15min at the rotating speed of 2000r/min to obtain the W/O/W type multiple emulsion unblocking system.

Example 3.

The preparation method of the W/O/W type multiple emulsion acidification de-plugging system comprises the following steps:

(1) preparing an oil phase: dissolving surfactant Span60 and hydrophobic nano silicon dioxide particles in oil through ultrasonic dispersion to obtain an oil phase; wherein, based on the total mass of the obtained oil phase, the mass fraction of Span60 is 2%, the mass fraction of the hydrophobic nano silica particles is 3%, and the particle size of the hydrophobic nano silica particles is 30 nm; the oil is styrene tar;

(2) preparing an internal water phase: dissolving 15% of hydrochloric acid, 1% of corrosion inhibitor and 1% of hydroxyethylidene diphosphonic acid in water by mass percent based on the total mass of the obtained internal water phase to obtain the internal water phase, wherein the hydrochloric acid is prepared by diluting 38% of analytically pure hydrochloric acid, the corrosion inhibitor is commercially available Mannich base, and the Mannich base is copolymerized by n-hexylamine, acetophenone and paraformaldehyde;

(3) preparation of W/O type initial phase: mixing the oil phase in the step (1) and the internal water phase in the step (2) according to a volume ratio of 3:7, placing the mixture in a beaker, and homogenizing and stirring the mixture for 8min at the rotating speed of 8000r/min to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving alkanolamide and dodecyl dimethyl amine oxide in a mass ratio of 8:2 in water to obtain an external water phase; wherein, the mass fraction of the alkanolamide and the dodecyl dimethyl amine oxide in the external water phase is 0.3 percent based on the total mass of the obtained external water phase;

(5) mixing the W/O type initial phase and the external water phase according to the volume ratio of 4: and 6, homogenizing and stirring for 10min at the rotating speed of 3000r/min to obtain the W/O/W type multiple emulsion unblocking system.

Comparative example 1.

The preparation method of the W/O/W type multiple emulsion acidification de-plugging system comprises the following steps:

(1) preparing an oil phase: dissolving surfactant Span60 and hydrophobic nano silicon dioxide particles in oil through ultrasonic dispersion to obtain an oil phase; wherein, based on the total mass of the obtained oil phase, the Span60 accounts for 0.5 percent, the hydrophobic nano silicon dioxide particles account for 0.1 percent, and the particle size is 30 nm; the oil is styrene tar;

(2) preparing an internal water phase: dissolving 15% of hydrochloric acid, 1% of corrosion inhibitor and 1% of hydroxyethylidene diphosphonic acid in water by mass percent based on the total mass of the obtained internal water phase to obtain an internal water phase; the hydrochloric acid is prepared by diluting 38% of analytically pure hydrochloric acid, the corrosion inhibitor is a commercially available Mannich base, and the Mannich base is synthesized by n-hexylamine, acetophenone and paraformaldehyde in a copolymerization manner;

(3) preparation of W/O type initial phase: mixing the oil phase and the internal water phase in the step (1) according to a volume ratio of 3:7, placing the mixture in a beaker, and homogenizing and stirring the mixture for 8min at the rotating speed of 9000r/min to obtain a W/O type initial phase;

(4) preparing an external water phase: dissolving alkanolamide and dodecyl dimethyl amine oxide in a mass ratio of 8:2 in water to obtain an external water phase; wherein, the mass fraction of the alkanolamide and the dodecyl dimethyl amine oxide in the external water phase is 0.05 percent based on the total mass of the obtained external water phase;

(5) mixing the W/O type initial phase and the external water phase according to the volume ratio of 4: and 6, homogenizing and stirring for 10min at the rotating speed of 4000r/min to obtain the W/O/W type multiple emulsion unblocking system.

Comparative example 2.

The difference between the preparation method of the W/O/W multiple emulsion acidizing unblocking system described in example 1 is that the emulsifier in the external water phase is cetyl carboxybetaine, the surfactant has a good ability to reduce the interfacial tension of oil and water, and the interfacial tension of the formation crude oil reaches 0.0012mN/m, but the prepared multiple emulsion undergoes oil-water separation at room temperature for 15min, and has poor stability.

Meanwhile, the interfacial tension between the blockage removal system prepared by the composite emulsifier and the crude oil in the embodiments 1-3 is 0.086mN/m, and the blockage removal system has better capability of reducing the interfacial tension and capability of cleaning the crude oil on the surface of the rock (high oil washing efficiency). Meanwhile, the emulsion stability is good, and the water content in 8h is less than 10%.

Comparative example 3.

The same procedure used to prepare the W/O/W multiple emulsion acidizing unblocking system of example 2 was followed, except that the emulsifier for the external aqueous phase was alkanolamide.

The comparative example used a single emulsifier to produce a de-plugging system with a stabilization time of less than 4 hours, while the comparative example produced less than 80% multiple emulsions, and examples 1-3 produced more than 90% multiple emulsions.

Comparative example 4.

The same procedure as in example 2 was followed except that the hydrophobic silica nanoparticles in the oil phase had a particle size of < 20nm or > 50 nm.

Because the particles have an enhancement effect on the stability of the multiple emulsion unblocking system, if the hydrophobic nano-silica particles with the particle size of less than 20nm or more than 50nm are used, the stability of the primary phase of the multiple emulsion unblocking system can not meet the technical requirement, and the water content in 8h is more than 20%.

Experimental example:

1. research on flow-dividing and blockage-removing effect

Shear rate of 7.34s at 20 ℃ as measured by Brookfield viscometer^-1The viscosity of the W/O/W type multiple emulsion acidification and blockage removal systems prepared in the examples 1-3 and the comparative example 1 is determined to be 56.4mPa.s, 44.1mPa.s and 34.0mPa.s respectively, the stability is over 30 days, and the viscosity of the system in the comparative example 1 is 6.2mPa.s, and the system stability is poor.

The flow diversion and blockage removal performance of the system in example 1 is evaluated by using artificial cores with permeability of 58.1mD, 298.8mD, 65.2mD and 308.6mD respectively, the flow diversion and blockage removal performance of the system in example 2 is evaluated by using artificial cores with permeability of 47.8mD, 320.2mD, 55.3mD and 304.1mD respectively, and the flow diversion and blockage removal performance of the system in example 3 is evaluated by using artificial cores with permeability of 57.8mD, 354.1mD, 50.4mD and 301.7mD respectively, and the results are shown in tables 1-3. The plugging removal performance of the system of comparative example 1 was evaluated using artificial cores having permeabilities of 50.7mD, 329.4mD, 64.2mD, and 352.6mD, respectively, and the results are shown in Table 4.

TABLE 1. example 1 diverting and deblocking effect of deblocking system

TABLE 2. example 2 diverting and deblocking effect of deblocking system

TABLE 3. example 3 diverting deblocking effect of deblocking System

TABLE 4 diverting and unblocking effect of unblocking system of comparative example 1

And (4) conclusion: as can be seen from tables 1 to 4, in the improvement rate of the permeability of the low-permeability rock core, the improvement rate of the emulsion acidification deblocking system of example 1 is 14.1% higher than that of the hydrochloric acid deblocking system, the improvement rate of the emulsion acidification deblocking system of example 2 is 13.1% higher than that of the hydrochloric acid deblocking system, the improvement rate of the emulsion acidification deblocking system of example 3 is 17.5% higher than that of the hydrochloric acid deblocking system, and the deblocking effect of the comparative example 1 is not much different from that of the hydrochloric acid system, so that the obvious shunting deblocking effect cannot be achieved.

2. Emulsion stability study

The formation rate and emulsion stability of the deblocking system in examples 1 to 3 and comparative examples 1 to 4 were investigated. The results obtained are shown in Table 5 below.

Wherein, the generation rate refers to the proportion of the water phase in the colostrum preserved in the oil-in-water of the internal phase, and the test method is as follows:

the multiple emulsion was dialyzed in a dialysis membrane because the internal aqueous phase contained chloride ions, the amount of chloride ions transferred was measured by titration, and the formation rate of the multiple emulsion was calculated by the following formula:

A(V₀+V₂+X)＝X×B

a and B are the concentration of chloride ions in the distilled water and the internal aqueous phase, respectively, X is the volume of the internal aqueous phase that has oozed out, V₀、V₁And V₂The volume of the inner aqueous phase, the volume of the outer aqueous phase and the volume of the distilled water, respectively.

The emulsion stability was tested as follows:

the prepared W/O/W emulsion was placed in a measuring cylinder with a stopper, and was thermostated in a water bath at 40 ℃ for 7 days, with different degrees of stratification occurring, and the volume sum of the free water layer and the oil layer was read, and the percentage was calculated according to the following formula, to thereby evaluate the stability of the W/O/W emulsion.

TABLE 5

In conclusion, the stability, viscosity and core permeability improvement rate of the W/O/W type multiple emulsion acidification plugging removal system are tested, and the shear rate is 7.34s at the temperature of 20 DEG C^-1Under the condition, the viscosity of the acidification de-plugging system reaches 32-56mPa.s, the stabilization time exceeds 30 days, high-low permeability parallel displacement is adopted for the artificial core, the rate of the de-plugging system is increased by 17.5% at most compared with the rate of the hydrochloric acid system on the aspect of increasing the permeability of the low permeability core, and the multiple emulsion acidification de-plugging system is proved to be an effective chemical shunt slow de-plugging system.