Multi-emulsion with high-precision gas-sensitive fracturing tracing capability as well as preparation method and application of multi-emulsion

Abstract

The invention relates to multiple emulsions with high-precision gas-sensitive fracturing tracer capacity and a preparation method and application thereof, and belongs to the technical field of functional materials. The problems that in the prior art, few reports are reported for gas-phase tracers in unconventional reservoir fracturing effect evaluation, and no W / O / W emulsion with sensitive response characteristics for hydrocarbon gas in stratum oil reservoirs exists, so that efficient monitoring of the underground oil-gas-water three-phase yield is achieved are solved. The invention provides a W / O / W type multiple emulsion which is prepared by taking a solution with small molecule gaseous hydrocarbon sensitivity as an oil phase and utilizing modified starch particles to replace a traditional small molecule surfactant as a stabilizer to stabilize a Pickering emulsion. The multi-emulsion can realize the release of the micromolecular rare earth tracing material in fracturing flow-back fluid and an underground oil-gas body, so that the underground oil-gas-water three-phase yield is efficiently monitored, and the shape of a crack net formed by fracturing construction and the profile of an oil-gas production layer are analyzed.

Description

Technical Field

[0001] The invention belongs to the technical field of functional materials, and in particular relates to a multiple emulsion with high-precision gas-sensitive fracturing tracing capability, and a preparation method and application thereof. Background Art

[0002] At present, the proven amount of unconventional oil and gas resources such as shale oil and gas, tight oil and gas in China has increased year by year, and the development demand for natural gas, shale gas, etc. is huge. Multi-stage hydraulic fracturing has gradually become a common technical means for the development of such oil fields. The characterization of fracturing cracks is an important link in the process of horizontal well fracturing development. At present, the methods for evaluating the fracturing effect are mostly described and predicted based on geological data, numerical simulation methods, and changes in the concentration of certain ions in the return fluid. Most of them are empirical methods or semi-empirical methods, with poor universality and certain limitations. As a means of evaluating the fracturing effect, the fracturing tracer technology can indirectly obtain and analyze the return flow of the fracturing fluid in each layer during the fracturing process, the production capacity of each reservoir at different times, the liquid production profile in the early stage of production, and the liquid production contribution rate of each layer by monitoring the concentration changes of the tracer in the return fluid of each fracturing layer. At the same time, the effect of fracturing measures can be quickly and effectively evaluated, which makes it play an important role in the development of unconventional oil and gas and has great application potential.

[0003] The types of tracers in fracturing tracer technology mainly include water phase tracers, oil phase tracers and gas phase tracers. However, there are few reports on the evaluation of the fracturing effect of gas phase tracers in unconventional reservoirs. As a good carrier for controlled release, the outermost water phase of W / O / W emulsion not only has good compatibility with the cement slurry system, but also can serve as a protective layer to protect the water phase and oil phase tracers wrapped in the inner phase. Therefore, if a W / O / W emulsion with sensitive response characteristics to hydrocarbon gases in formation reservoirs can be developed, the polymer network will be increased, thereby increasing the tracer release rate to achieve the purpose of transmitting information, realizing the efficient monitoring of the three-phase production of oil, gas and water in the well, and the analysis of the fracture network shape formed by fracturing construction and the oil and gas production layer profile, which is of great significance. Summary of the invention

[0004] In order to solve the problems that there are few reports on gas phase tracers in the evaluation of fracturing effects of unconventional reservoirs in the prior art, and there is no W / O / W emulsion with sensitive response characteristics to hydrocarbon gases in formation oil reservoirs to achieve efficient monitoring of downhole oil, gas and water three-phase production, the present invention provides a W / O / W type multiple emulsion prepared by using a material with small molecule gaseous hydrocarbon sensitivity as an oil phase and using modified starch particles instead of traditional small molecule surfactants as a stabilizer to stabilize the Pickering emulsion, so as to achieve the release of small molecule rare earth tracer materials in fracturing return fluid and downhole oil and gas, and to efficiently monitor the downhole oil, gas and water three-phase production, and analyze the shape of the fracture network formed by fracturing construction and the profile of the oil and gas production layer.

[0005] In order to achieve the above technical effects, the present invention provides the following technical solutions:

[0006] The first object of the present invention is to provide a multiple emulsion with gas-sensitive fracturing tracing capability, wherein the multiple emulsion is a W / O / W emulsion, and based on the mass of the W / O / W emulsion being 100%, the W / O / W emulsion is composed of 70-90% of an oil phase and 10-30% of an aqueous phase, wherein the oil phase is a stable water-in-oil emulsion, and the aqueous phase is prepared by dispersing a solid particle surfactant in water; the water-in-oil emulsion is based on the mass of the water-in-oil emulsion being 100%, and is composed of 40-60% of an oil phase and 40-60% of an aqueous phase, wherein the oil phase of the water-in-oil emulsion is made of an oil phase solvent, an oil phase tracer, a rubber-grafted gas-sensitive material and a non-ionic surfactant, and the aqueous phase of the water-in-oil emulsion is made of an aqueous phase tracer and water.

[0007] In one embodiment of the present invention, the solid particle surfactant is any one of modified SiO2, modified cellulose and modified starch.

[0008] In one embodiment of the present invention, the mass fraction of the oil phase tracer in the oil phase of the water-in-oil emulsion is 25%, the mass fraction of the rubber grafted gas sensitive material is 30%, and the mass fraction of the nonionic surfactant is 3%-10%.

[0009] In one embodiment of the present invention, the method for preparing the rubber grafted gas-sensitive material comprises the following steps:

[0010] ① mixing one or a combination of any two or more of an acrylic acid ester monomer, an alkyl acrylate monomer and a styrene monomer with a solvent to obtain a monomer solution;

[0011] ② Swelling the non-polar or weakly polar rubber particles in the monomer solution in step ① to obtain a prepolymer;

[0012] ③ After mixing the prepolymer described in step ② with the isolation agent, a graft polymerization reaction is carried out under initiation polymerization conditions, and the product is dried and crushed to obtain a rubber grafted gas-sensitive material.

[0013] In one embodiment of the present invention, the total mass fraction of monomers in the monomer solution in step ① is 20%-40%, and the solvent is any one of benzene, toluene or xylene.

[0014] In one embodiment of the present invention, the acrylate monomer in step ① can be hexadecyl methacrylate, octadecyl acrylate, methyl methacrylate, etc.

[0015] In one embodiment of the present invention, the alkyl olefinic acid monomer in step ① may be undecylenic acid or the like.

[0016] In one embodiment of the present invention, the rubber particles in step ② are ethylene-propylene rubber particles with a median particle size of 5 mm or isoprene rubber particles with a median particle size of 5 mm, and the swelling time is 6 hours.

[0017] In one embodiment of the present invention, after the non-polar or weakly polar rubber particles are mixed with the monomer solution in step ②, the mass fraction of the non-polar or weakly polar rubber particles is 30%.

[0018] In one embodiment of the present invention, the mass ratio of the prepolymer to the release agent in step ③ is 1:1.

[0019] In one embodiment of the present invention, the release agent in step ③ is white carbon black.

[0020] In one embodiment of the present invention, the polymerization initiation method in step ③ is high-energy electron irradiation at room temperature with an irradiation intensity of 120 kGy.

[0021] In one embodiment of the present invention, the drying condition in step ③ is vacuum drying at 50° C. for 12 hours.

[0022] In one embodiment of the present invention, the oil phase tracer is one or a combination of two or more liquid hydrocarbon compounds.

[0023] In one embodiment of the present invention, the nonionic surfactant is Span 20 or Span 80, or a combination of Span 20 and Span 80.

[0024] In one embodiment of the present invention, the mass fraction of the water phase tracer in the water phase of the water-in-oil emulsion is 25%; the water phase tracer is one or a combination of two or more rare earth salt compounds.

[0025] A second object of the present invention is to provide a method for preparing the above-mentioned multiple emulsion, the preparation method comprising the following steps:

[0026] (1) Preparation of water-in-oil emulsion:

[0027] A) dispersing the rubber-grafted gas-sensitive material, the oil phase tracer and the surfactant in toluene as the oil phase;

[0028] B) dissolving the aqueous phase tracer in water as the aqueous phase;

[0029] C) mixing the oil phase described in step A) and the water phase described in step B) and homogenizing and emulsifying to obtain a water-in-oil emulsion;

[0030] (2) Preparation of water-in-oil-in-water emulsion:

[0031] a) using the water-in-oil emulsion obtained in step (1) as the oil phase;

[0032] b) dispersing solid particles having a water contact angle between 15° and 80° in water as a surfactant as an aqueous phase;

[0033] c) mixing the oil phase in step a) with the water phase in step b), and homogenizing and emulsifying to obtain a water-in-oil-in-water emulsion.

[0034] In one embodiment of the present invention, in step A), the mass fraction of the oil phase tracer in the oil phase is 25%, the mass fraction of the rubber grafted gas sensitive material is 30%, and the mass fraction of the surfactant is 3%-10%.

[0035] In one embodiment of the present invention, the oil phase tracer in step A) is a liquid hydrocarbon compound, specifically a C5-C16 hydrocarbon compound.

[0036] In one embodiment of the present invention, the surfactant in step A) is Span 20 or Span 80.

[0037] In one embodiment of the present invention, the mass fraction of the aqueous phase tracer in the aqueous phase in step B) is 25%.

[0038] In one embodiment of the present invention, the aqueous phase tracer in step B) is a rare earth salt compound, specifically cerium chloride, lanthanum chloride, praseodymium chloride, neodymium chloride, yttrium chloride, samarium chloride, europium chloride, gadolinium chloride, dysprosium chloride, ytterbium chloride, holmium chloride, erbium chloride or terbium chloride.

[0039] In one embodiment of the present invention, the volume ratio of the oil phase to the water phase in step C) is (4:6)-(6:4).

[0040] In one embodiment of the present invention, the homogenization speed in step C) is 15 krpm-20 krpm, and the emulsification time is 2 min.

[0041] In one embodiment of the present invention, the solid particles in step b) are any one of modified SiO2, modified cellulose and modified starch.

[0042] In one embodiment of the present invention, the oil phase and the water phase in step c) are mixed in a volume ratio of (9:1)-(7:3).

[0043] The third object of the present invention is to provide the application of the above-mentioned multiple emulsion or the above-mentioned preparation method in realizing the efficient monitoring of the three-phase production of oil, gas and water in the well, and the analysis of the shape of the fracture network formed by the fracturing construction and the oil and gas production layer profile.

[0044] Beneficial effects of the present invention:

[0045] The invention provides a W / O / W type multiple emulsion prepared by using a solution with small molecule gaseous hydrocarbon sensitivity as an oil phase and using modified starch particles to replace traditional small molecule surfactants as surfactants to stabilize Pickering multiple emulsions. The emulsion type gas phase fracturing tracer material provided by the present invention has good stability; the outermost water phase not only has good compatibility with the cement slurry system, but also can serve as a protective layer to protect the water phase and oil phase tracers wrapped in the inner phase to a certain extent; when the W / O / W emulsion is transported to a specific location underground, according to the responsiveness of the gas sensitive material therein to hydrocarbon gas in the formation oil reservoir, the polymer network is increased so as to increase the tracer release rate, so as to achieve the purpose of transmitting information; the inner layer W / O emulsion has a wider particle size distribution range, and at the same time shows excellent and adjustable tracer release efficiency under the wide particle size distribution; during mine construction and shale gas exploitation, the tracer particles are transported to the wellhead along with the produced fluid, and the underground oil, gas and water three-phase production can be quickly and efficiently monitored through the testing instrument, and the fracture network shape can be evaluated in the fracturing transformation of unconventional reservoirs, so that the underground situation can be truly and effectively reflected. The emulsion-type gas-phase fracturing tracer material provided by the present invention can realize the release of small-molecule rare earth tracer materials in fracturing return fluid and downhole oil and gas, and can efficiently monitor the downhole oil, gas and water three-phase production, and analyze the shape of the crack network formed by fracturing construction and the profile of the oil and gas production layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 The figure is a test result diagram of the tracer release efficiency in the emulsions prepared in Example 1, Example 4 and Example 5; wherein, Figure 1 (a) is a graph showing the detection result of the tracer release efficiency in the emulsion prepared in Example 1. Figure 1 (b) is a graph showing the detection result of the tracer release efficiency in the emulsion prepared in Example 1. Figure 1 (c) is a graph showing the detection result of the tracer release efficiency in the emulsion prepared in Example 1. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific implementation methods and the accompanying drawings of the specification. It should be noted that the embodiments in this application and the features in the embodiments can be combined with each other without conflict. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can also be obtained based on these drawings without paying creative work.

[0048] The experimental methods used in the following examples are all conventional methods unless otherwise specified. If no specific conditions are specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. The materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0049] Embodiment 1:

[0050] Hexadecyl methacrylate, undecylenic acid and styrene are dissolved in xylene to prepare a monomer solution with a total monomer mass concentration of 30wt%, wherein the mass fraction of hexadecyl methacrylate is 20.0%, the mass fraction of undecylenic acid is 7.0%, the mass fraction of styrene is 3.0%, and the rest is xylene. Ethylene-propylene rubber particles with a median particle size of 5mm are subjected to diffusion-controlled swelling in the monomer solution for 6 hours to obtain a prepolymer, wherein the mass fraction of ethylene-propylene rubber particles is 30%. After adding 50wt% of white carbon black to the obtained prepolymer, high-energy electron irradiation is carried out at room temperature to induce the monomer to undergo graft polymerization reaction inside and on the surface of the rubber particles, and the irradiation intensity is 120kGy; then the product is vacuum dried at 50°C for 12 hours and crushed to obtain a rubber grafted gas-sensitive material. Weigh 25g of water phase tracer (neodymium chloride), dissolve it in 75mL of water as water phase, 100mL of toluene solution (containing 25mL of oil phase tracer (pentane), 30mL of the rubber grafted gas sensitive material prepared above, 5mL of Span 80) as oil phase, take 5mL of the water phase and 5mL of the oil phase, mix the two, and emulsify them at 15krpm for 120s with IKA Ultra Turrax T18 homogenizer to prepare W / O emulsion. Take 8mL of the obtained O / W emulsion as oil phase, 2mL, 5wt% modified starch (HBPS) aqueous solution as water phase, mix the two, and emulsify them at 10krpm for 120s with IKA Ultra Turrax T18 homogenizer to prepare W / O / W emulsion.

[0051] Embodiment 2:

[0052] The difference from Example 1 is that, in the process of preparing the rubber grafted gas-sensitive material, hexadecyl methacrylate, undecylenic acid and styrene are dissolved in xylene to prepare a monomer solution with a total monomer mass concentration of 20 wt%, wherein the mass fraction of hexadecyl methacrylate is 14.0%, the mass fraction of undecylenic acid is 4.0%, the mass fraction of styrene is 2.0%, and the balance is xylene.

[0053] Embodiment 3:

[0054] The difference from Example 1 is that, in the process of preparing the rubber grafted gas-sensitive material, hexadecyl methacrylate, undecylenic acid and styrene are dissolved in xylene to prepare a monomer solution with a total monomer mass concentration of 40wt%, wherein the mass fraction of hexadecyl methacrylate is 28.0%, the mass fraction of undecylenic acid is 8.0%, the mass fraction of styrene is 4.0%, and the balance is xylene.

[0055] Embodiment 4:

[0056] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 4 mL of the water phase and 6 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s at 15 krpm using an IKA Ultra Turrax T18 homogenizer to obtain a W / O emulsion.

[0057] Embodiment 5:

[0058] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 6 mL of the water phase and 4 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s at 15 krpm using an IKA Ultra Turrax T18 homogenizer to obtain a W / O emulsion.

[0059] Embodiment 6:

[0060] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 25 g of the aqueous phase tracer was weighed and dissolved in 75 mL of water as the aqueous phase, 100 mL of toluene solution (containing 25 mL of the oil phase tracer, 30 mL of the rubber grafted gas-sensitive material, and 3 mL of Span 80) was used as the oil phase, 5 mL of the aqueous phase and 5 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s at 15 krpm using an IKA Ultra Turrax T18 homogenizer to obtain a W / O emulsion.

[0061] Embodiment 7:

[0062] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 25 g of the aqueous phase tracer was weighed and dissolved in 75 mL of water as the aqueous phase, 100 mL of toluene solution (containing 25 mL of the oil phase tracer, 30 mL of the rubber grafted gas-sensitive material, and 10 mL of Span 80) was used as the oil phase, 5 mL of the aqueous phase and 5 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s at 15 krpm using an IKA Ultra Turrax T18 homogenizer to obtain a W / O emulsion.

[0063] Embodiment 8:

[0064] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 25 g of the aqueous phase tracer was weighed and dissolved in 75 mL of water as the aqueous phase, 100 mL of toluene solution (containing 25 mL of the oil phase tracer, 30 mL of the rubber grafted gas-sensitive material, and 5 mL of Span 80) was used as the oil phase, 5 mL of the aqueous phase and 5 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s using an IKA Ultra Turrax T18 homogenizer at 18 krpm to obtain a W / O emulsion.

[0065] Embodiment 9:

[0066] The difference from Example 1 is that in the process of preparing the water-in-oil (W / O) emulsion, 25 g of the aqueous phase tracer was weighed and dissolved in 75 mL of water as the aqueous phase, 100 mL of toluene solution (containing 25 mL of the oil phase tracer, 30 mL of the rubber grafted gas-sensitive material, and 5 mL of Span 80) was used as the oil phase, 5 mL of the aqueous phase and 5 mL of the oil phase were taken, the two were mixed, and then emulsified for 120 s at 20 krpm using an IKA Ultra Turrax T18 homogenizer to obtain a W / O emulsion.

[0067] Embodiment 10:

[0068] The difference from Example 1 is that in the process of preparing the rubber grafted gas-sensitive material, isoprene rubber particles with a median particle size of 5 mm are selected.

[0069] Embodiment 11:

[0070] The difference from Example 1 is that, in the process of preparing the rubber grafted gas-sensitive material, octadecyl acrylate, methyl methacrylate and styrene are dissolved in xylene to prepare a monomer solution with a total monomer mass concentration of 30 wt%, wherein the mass fraction of octadecyl acrylate is 20.0%, the mass fraction of methyl methacrylate is 7.0%, the mass fraction of styrene is 3.0%, and the rest is xylene.

[0071] Performance Test:

[0072] (1) Stability test: The multiple emulsions prepared in Examples 1-11 were centrifuged at 4000 r for 5 min. After centrifugation, the stratification heights of the multiple emulsions prepared in Examples 1-11 were recorded. The results are shown in Table 1. As shown in Table 1, the emulsions prepared in Examples 1-11 did not stratify after centrifugation, indicating that the multiple emulsions prepared in Examples 1-11 all had good stability and could be placed at room temperature for at least one month.

[0073] (2) Particle size test: The droplet size of the W / O emulsion prepared in Examples 1-11 was tested by light scattering method, and the results are shown in Table 1. As can be seen from the results in Table 1, the particle size of the W / O emulsion droplets decreases with the increase of the amount of Span 80 and the increase of the emulsification speed, which proves the adjustability of the emulsion droplets. Emulsion droplets of different particle sizes also play a certain auxiliary role in adjusting the release rate of the tracer.

[0074] Table 1 The stability of the multiple emulsions prepared in Examples 1-11 and the test results of the W / O emulsion droplet size.

[0075]

[0076] (3) Gas sensitivity test: 1.0 g of the W / O emulsions prepared in Examples 1-3 above (denoted as M 0 ) is placed in a sealed container, sealed and natural gas is added to the container, and the pressure is maintained for 72 hours, then the pressure is released and the sample is taken out and weighed (recorded as Me). The swelling ratio of the sample in natural gas is Qq = (Me-M 0 ) / M 0 ×100%; see Table 2 for test results.

[0077] Table 2 Test results of swelling ratio of W / O emulsions prepared in Examples 1-3 in natural gas

[0078]

[0079] It can be seen from Table 2 that the W / O emulsions prepared in Examples 1-3 swell after contacting the gas, and the greater the swelling ratio, the better the sensitivity to the gas response.

[0080] (4) Tracer release test: The W / O emulsion (using Examples 1-3 as an example) was demulsified by centrifugation at 10,000 r / min for 10 min. The tracer concentrations in the upper and lower oil phases and the water phase were tested by ICP. This concentration was the maximum adsorption amount C of the tracer. 0The W / O emulsion sample was placed in a sealed container, and natural gas was added to the container after sealing. After the pressure was maintained for a period of time (recorded in hours), the tracer concentration Ce in the upper oil phase and the lower water phase was measured by ICP. Tracer release efficiency = (C 0 -C e ) / C 0 ×100%, the test results are as follows Figure 1 And as shown in Table 3.

[0081] Table 3 Tracer release efficiency test results of W / O emulsions prepared in Examples 1-11

[0082]

[0083] It can be seen from Table 3 that the tracer release efficiency in the water phase and the oil phase of the W / O emulsions prepared in Examples 1-11 can achieve relatively ideal results.

[0084] From the above test results, it can be seen that the emulsion type gas phase fracturing tracer material provided by the present invention has good stability. The outermost water phase not only has good compatibility with the cement slurry system, but also can serve as a protective layer to protect the water phase and oil phase tracers wrapped in the inner phase. The inner layer W / O emulsion has a wide particle size distribution range, and at the same time exhibits excellent and adjustable tracer release efficiency under this wide particle size distribution, which can truly and effectively reflect the downhole situation.

[0085] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A multiple emulsion with gas-sensitive fracturing tracing capability, characterized in that: The multiple emulsion is a W / O / W emulsion. Taking the mass of the W / O / W emulsion as 100%, the W / O / W emulsion is composed of 70-90% of an oil phase and 10-30% of an aqueous phase. The oil phase is a stable oil-in-water emulsion, and the aqueous phase is prepared by dispersing a solid particle surfactant in water. The oil-in-water emulsion is composed of 40-60% of an oil phase and 40-60% of an aqueous phase, taking the mass of the oil-in-water emulsion as 100%, and the oil phase of the oil-in-water emulsion is made of an oil phase solvent, an oil phase tracer, a rubber grafted gas-sensitive material and a non-ionic surfactant, and the aqueous phase of the oil-in-water emulsion is made of an aqueous phase tracer and water.

2. The multiple emulsion according to claim 1, characterized in that The solid particle surfactant is any one of modified SiO2, modified cellulose and modified starch.

3. The multiple emulsion according to claim 1, characterized in that The mass fraction of the oil phase tracer in the oil phase of the water-in-oil emulsion is 25%, the mass fraction of the rubber grafted gas sensitive material is 30%, and the mass fraction of the nonionic surfactant is 3%-10%.

4. The multiple emulsion according to claim 3, characterized in that The preparation method of the rubber grafted gas-sensitive material comprises the following steps: ① mixing one or a combination of any two or more of an acrylic acid ester monomer, an alkyl acrylate monomer and a styrene monomer with a solvent to obtain a monomer solution; ② Swelling the non-polar or weakly polar rubber particles in the monomer solution of step ① to obtain a prepolymer; ③ After mixing the prepolymer of step ② with the isolation agent, a graft polymerization reaction is carried out under the initiation polymerization condition, and the product is dried and crushed to obtain a rubber grafted gas-sensitive material.

5. The multiple emulsion according to claim 4, characterized in that In step ①, the total mass fraction of monomers in the monomer solution is 20%-40%, and the solvent is any one of benzene, toluene or xylene; in step ③, the mass ratio of the prepolymer to the isolation agent is 1:

1.

6. The multiple emulsion according to claim 3, characterized in that The oil phase tracer is one or a combination of two or more liquid hydrocarbon compounds.

7. The multiple emulsion according to claim 3, characterized in that The nonionic surfactant is Span 20 or Span 80, or a combination of Span 20 and Span 80.

8. The multiple emulsion according to claim 1, characterized in that The mass fraction of the water phase tracer in the water phase of the water-in-oil emulsion is 25%; the water phase tracer is one or a combination of two or more rare earth salt compounds.

9. A method for preparing the multiple emulsion according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: (1) Preparation of water-in-oil emulsion: A) dispersing the rubber-grafted gas-sensitive material, the oil phase tracer and the surfactant in toluene as the oil phase; B) dissolving the aqueous phase tracer in water as the aqueous phase; C) mixing the oil phase in step A) and the water phase in step B), and homogenizing and emulsifying to obtain a water-in-oil emulsion; (2) Preparation of water-in-oil-in-water emulsion: a) using the water-in-oil emulsion obtained in step (1) as the oil phase; b) dispersing solid particles having a water contact angle between 15° and 80° in water as a surfactant as an aqueous phase; c) mixing the oil phase in step a) with the water phase in step b), and homogenizing and emulsifying to obtain a water-in-oil-in-water emulsion.

10. Use of the multiple emulsion according to any one of claims 1 to 8 in realizing efficient monitoring of the three-phase production of oil, gas and water in a well, and analysis of the shape of the fracture network formed by fracturing construction and the profile of the oil and gas production layer.

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