Acid gas triggered tracer sustained-release gel material and preparation method and application thereof

Abstract

Acid gas triggered tracer slow-release gel material and its preparation method and application. The present invention belongs to the field of tracer controlled-release materials in hydraulic fracturing processes. The present invention is to solve the technical problems that acid gas accompanying petroleum gas endangers construction safety, causes air pollution and greenhouse effect, and lacks tracer slow-release materials that can effectively monitor hydraulic fracturing conditions. The material of the present invention is prepared by first initiating polymerization of acrylamide monomers, N-vinylalkylamide monomers, acrylonitrile and tracers, and then hydrolyzing them at high temperature in a hydrochloric acid solution. The gel material of the present invention can effectively capture acid gas and release the tracer, thereby achieving the purpose of transmitting changes in underground oil, gas and acid gas. And as needed, the mechanical strength and release performance of the gel material can be controlled by changing the hydrolysis time and temperature, hydrochloric acid concentration and the proportion of N-vinylalkylamide monomers in the gel.

Description

Technical Field

[0001] The invention belongs to the field of tracer controlled-release materials in hydraulic fracturing processes, and particularly relates to an acid gas-triggered tracer slow-release gel material, a preparation method thereof, and applications thereof. Background Art

[0002] During the development of horizontal wells, in order to quickly discover high-quality oil reservoirs and increase the reservoir drilling rate, it is necessary to frequently control and adjust the horizontal wellbore trajectory. However, the actual operation often requires a lot of manpower and machinery costs, which is difficult to control and will also cause huge hidden dangers to subsequent construction.

[0003] The characterization of fractures has always been a key issue in the horizontal well fracturing development process of oil and gas reservoirs. How to better obtain the information transmitted by the underground reservoir has become a key focus for researchers. In order to study the complex fractures formed in the corresponding fracture layer after horizontal well fracturing, different tracers can be selected according to the actual application environment and the fracture tracer technology can be used to qualitatively and quantitatively analyze the flowback fluid conditions and contribution rates of each fracture layer at different times after horizontal well staged fracturing. It can also be used to evaluate the fracturing effect and provide data for improving the fracturing process. Currently, there are few reports on the application of slow-release tracers in unconventional reservoir fracturing, and it is still in its infancy.

[0004] Associated petroleum gases such as H2S and CO2, produced during coalbed methane extraction and mine construction, have long been considered byproducts of oil and gas production. Their presence accelerates cement erosion, posing a significant threat to underground operations and compromising construction safety. The emission of these toxic gases also contributes to air pollution and the greenhouse effect. Consequently, effectively utilizing these toxic acidic gases while simultaneously enabling effective monitoring of underground oil and gas levels remains a pressing technical challenge in this field. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention provides an acid gas triggered tracer sustained-release gel material and a preparation method and application thereof.

[0006] The purpose of the present invention is to achieve through the following technical solutions:

[0007] One of the objectives of the present invention is to provide an acid gas triggered tracer sustained release gel material, the gel material comprising a gel matrix and a tracer coated therein, the gel matrix being polymerized from acrylamide monomers, N-vinylalkylamide monomers and / or acrylonitrile.

[0008] It is further defined that the mass ratio of acrylamide monomers, N-vinyl alkylamide monomers and acrylonitrile is (1-8):(1-4):(0-4), and the mass of the tracer is 5-50% of the total mass of the monomers.

[0009] It is further defined that the acrylamide monomers include one or more of acrylamide, methacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

[0010] It is further defined that the N-vinyl alkylamide monomers include one or more of N-vinyl-N-methylacetamide, N-vinyl acetamide, N-vinyl formamide, and N-[3-[3-(dimethylamino)acryloyl]phenyl]-N-ethylacetamide.

[0011] It is further defined that the tracer includes one or more of rare earth oxides, halogenated hydrocarbons, aromatic hydrocarbons, fluorescent dyes, halides, and nitrates.

[0012] It is further defined that the acid gas includes one or more of carbon dioxide, hydrogen sulfide, and sulfur dioxide.

[0013] A second object of the present invention is to provide a method for preparing the above-mentioned acid gas triggered tracer sustained-release gel material, the preparation method being carried out according to the following steps:

[0014] S1: adding acrylamide monomers, N-vinylalkylamide monomers and / or acrylonitrile to water, then adding a tracer and a cross-linking agent, and initiating polymerization under the action of an initiator to obtain a tracer-loaded hydrogel;

[0015] S2: placing the tracer-loaded hydrogel in a hydrochloric acid solution, hydrolyzing it and then drying it to obtain a tracer sustained-release gel material.

[0016] It is further defined that the crosslinking agent in S1 includes one of N,N'-methylenebisacrylamide (MBA), polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, divinylbenzene, diisocyanate, and 2-ethyl-4-methylimidazole.

[0017] It is further defined that the mass of the cross-linking agent in S1 is 0.05-0.5% of the total mass of the monomers.

[0018] It is further defined that the initiator in S1 includes peroxides, azo initiators and photoinitiators.

[0019] Furthermore, the peroxide initiator includes ammonium persulfate (APS) and potassium persulfate.

[0020] Furthermore, the azo initiators include azobisisobutylamidine hydrochloride (V-50) and azobisisobutylimidazoline hydrochloride (VA-044).

[0021] It is further defined that the photoinitiator includes one of o-chlorohexaarylbisimidazole, benzoin dimethyl ether, 1-hydroxycyclohexyl phenyl ketone, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

[0022] It is further defined that the conditions for initiating polymerization in S1 are 30-60° C. or ultraviolet irradiation, and polymerization for 4-24 hours.

[0023] It is further defined that the concentration of the hydrochloric acid solution in S2 is 0.5-5.0 M. The increase in the ion concentration in the hydrolysis solution increases the osmotic pressure inside and outside the gel, thereby preventing the release of the tracer in the gel.

[0024] It is further defined that the hydrolysis temperature is 50-150° C. and the time is 1-48 h.

[0025] A third object of the present invention is to provide an application of the above-mentioned acid gas triggered tracer sustained-release gel material in detecting acid gas.

[0026] A fourth object of the present invention is to provide an application of the above-mentioned acid gas triggered tracer slow-release gel material in monitoring hydraulic fracturing conditions.

[0027] Compared with the prior art, the present invention has the following significant effects:

[0028] (1) The present invention provides a gel material with intelligent response function to acid gas. When the gel material is applied in the field of hydraulic fracturing, it can effectively capture the acid gas accompanying petroleum gas, release the tracer, and return it to the ground with the return fluid, thereby achieving the purpose of transmitting information on the changes in underground oil, gas and acid gas concentrations as the formation storage conditions change.

[0029] (2) During the preparation process, the gel material of the present invention is first hydrolyzed in a hydrochloric acid solution. By regulating the ion concentration in the hydrolysis solution, the purpose of regulating the osmotic pressure inside and outside the gel is achieved, thereby avoiding the release of tracers in the gel when the fracturing fluid is pumped into the ground, and improving the accuracy of the tracer in transmitting underground fracturing crack information.

[0030] (3) The gel material of the present invention can achieve controllable adjustment of the mechanical strength and release performance of the gel material by changing the hydrolysis time, hydrolysis temperature, hydrochloric acid concentration and the proportion of N-vinylalkylamide monomers in the gel according to application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The tensile stress-strain curves of the gel materials obtained in Examples 1-4 and Comparative Example 1;

[0032] Figure 2 This is the swelling kinetics curve of the gel material obtained in Example 1;

[0033] Figure 3 The standard curve of absorbance at 404 nm and concentration of Sm2O3 solution with different concentrations;

[0034] Figure 4 The tracer release kinetic curve of the gel material obtained in Example 1 before and after CO2 is introduced;

[0035] Figure 5 The swelling curves of the gel materials obtained in Examples 5-8 and Comparative Example 2 at different pH values ​​are shown. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods, and instruments used are conventional in the art and can be obtained commercially by those skilled in the art unless otherwise specified.

[0038] As used in the following examples, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0039] When amount, concentration or other value or parameter are represented with the range of scope, preferred range or a series of upper preferred value and lower preferred value limit, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope "1 to 5", described scope should be interpreted as including scope "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within the scope.In this application specification and claims, range limitation can be combined and / or interchanged, and if these ranges are not otherwise stated, include all subranges contained therein.

[0040] The indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirement (i.e. the number of times they appear). Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the quantity clearly refers to only the singular form.

[0041] The term "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it necessarily refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0042] The endpoints of the ranges and any values ​​disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0043] Example 1

[0044] The preparation method of the acid gas triggered tracer sustained-release gel material of this embodiment is carried out by the following steps:

[0045] S1: 28 g of methacrylamide, 12 g of N-vinyl-N-methylacetamide, 0.2 g of MBA, and 5 g of Sm2O3 were added to 160 g of deionized water. After sonication for 10 min, a uniform pre-solution was obtained. Then, under nitrogen protection, 0.1 g of V-50 initiator was added and polymerization was carried out at 45°C for 24 h to obtain a tracer-loaded hydrogel.

[0046] S2: The hydrogel is placed in a 1 M hydrochloric acid solution, hydrolyzed at 60° C. for 8 h, and then dried at 80° C. to obtain a high-strength acidic gas-triggered tracer sustained-release gel material.

[0047] Example 2

[0048] The difference between this embodiment and embodiment 1 is that the hydrolysis time in S2 is 2 hours. Other steps and parameters are the same as those in embodiment 1.

[0049] Example 3

[0050] The difference between this embodiment and embodiment 1 is that the hydrolysis time in S2 is 4 hours. Other steps and parameters are the same as those in embodiment 1.

[0051] Example 4

[0052] The difference between this embodiment and embodiment 1 is that the hydrolysis time in S2 is 6 hours. Other steps and parameters are the same as those in embodiment 1.

[0053] Comparative Example 1

[0054] The difference between this comparative example and Example 1 is that the hydrolysis time in S2 is 0 h. The other steps and parameters are the same as those in Example 1.

[0055] Example 5

[0056] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 37 g acrylamide and 3 g N-vinyl acetamide. The other steps and parameters are the same as those in embodiment 1.

[0057] Example 6

[0058] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 34 g acrylamide and 6 g N-vinyl acetamide. The other steps and parameters are the same as those in embodiment 1.

[0059] Example 7

[0060] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 31 g acrylamide and 9 g N-vinyl acetamide. The other steps and parameters are the same as those in embodiment 1.

[0061] Example 8

[0062] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 28 g acrylamide and 12 g N-vinyl acetamide. The other steps and parameters are the same as those in embodiment 1.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that N-vinyl-N-methylacetamide is omitted in S1, and only one monomer, acrylamide, is used in an amount of 40 g. The other steps and parameters are the same as those in Example 1.

[0065] Example 9

[0066] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 28 g acrylamide, 4 g acrylonitrile and 8 g N-vinyl formamide. The other steps and parameters are the same as those in embodiment 1.

[0067] Example 10

[0068] The difference between this embodiment and embodiment 1 is that the monomers in S1 are 28g N-hydroxymethyl acrylamide, 4g acrylonitrile and 8g N-vinyl formamide. The other steps and parameters are the same as those in embodiment 1.

[0069] Example 11

[0070] The difference between this embodiment and embodiment 1 is that the tracer in S1 is tetraethyl rhodamine. Other steps and parameters are the same as those in embodiment 1.

[0071] Example 12

[0072] The difference between this embodiment and embodiment 1 is that the tracer in S1 is cerium oxide. The other steps and parameters are the same as those in embodiment 1.

[0073] Example 13

[0074] The difference between this embodiment and embodiment 1 is that the tracer in S1 is fluorescein isothiocyanate. Other steps and parameters are the same as those in embodiment 1.

[0075] Detection test (I)

[0076] The mechanical properties of the gel materials obtained in Examples 1-4 and Comparative Example 1 were tested. The specific test method is as follows: the gel material was made into a long strip with a width of 3 mm and a length of 30 mm. The test results are as follows: Figure 1 As shown, from Figure 1 It can be seen that its fracture stress and fracture strain are 1.17MPa and 1050% respectively.At the same time, with the extension of hydrolysis time, the fracture stress and fracture strain increase accordingly.

[0077] Detection test (II)

[0078] The gel material obtained in Example 1 was formed into small discs with a diameter of 5 mm. After drying, the gel material was subjected to swelling kinetics testing in deionized water with and without CO2 bubbling. The specific testing method was as follows: after drying, the gel material was weighed and then soaked for a sufficient time until swelling equilibrium was reached, and the weight was measured again.

[0079] Among them, the swelling ratio calculation formula is shown in 1-1:

[0080]

[0081] Where W d and W s represent the weight of the dry gel material and the weight of the gel material after swelling equilibrium, respectively.

[0082] The test results are as follows Figure 2 As shown, from Figure 2 It can be seen that under the condition of CO2 introduction, the final equilibrium hydrogel swelling ratio is 7 times the hydrogel swelling ratio under the condition of no CO2 introduction.

[0083] Detection test (3)

[0084] The gel material obtained in Example 1 was subjected to a release kinetics experiment. The specific test method is as follows: the gel material sample containing the tracer was placed in 100 mL of deionized water at room temperature of 30°C for release. 3 mL of the solution was taken out from the upper solution at regular intervals, and the ultraviolet absorption peak at 404 nm was detected. After 15 hours of release, CO2 was introduced into the deionized water, and 3 mL of the solution was taken out from the upper solution at regular intervals, and the absorption peak at 404 nm was detected. According to the standard curve of the absorbance value of the prepared Sm2O3 solution with different concentrations at 404 nm and the concentration (such as Figure 3 As shown) to obtain the Sm2O3 concentration, and thus draw the release curve. The test results are as follows Figure 4 As shown by Figure 4 It can be seen that before CO2 was introduced, the release amount of the hydrogel reached equilibrium at about 7% before 15 hours. After CO2 was introduced 15 hours later, the volume of the hydrogel changed and release occurred again, and the final release amount could reach about 80%.

[0085] Detection test (IV)

[0086] Using CO2 as the response gas, the swelling properties of the gel materials obtained in Examples 5-8, 11-13 and Comparative Example 2 at different pH values ​​and the tracer release kinetics were tested. The test results are shown in Figure 2. Figure 5 and as shown in Table 1.

[0087] Detection test (V)

[0088] Using H2S as the response gas, the tracer release kinetics in the gel material obtained in Examples 9-10 was tested. The test results are shown in Table 1.

[0089] Table 1 Tracer release from gel

[0090]

[0091] The foregoing are merely preferred embodiments of the present invention. These embodiments are all different implementations based on the overall concept of the present invention. The scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An acid gas-triggered tracer sustained-release gel material, comprising a gel matrix and a tracer encapsulated therein, characterized in that: The gel matrix is ​​polymerized from acrylamide monomers, N-vinyl alkylamide monomers and acrylonitrile; The preparation method of the acid gas triggered tracer sustained-release gel material is carried out according to the following steps: S1: adding acrylamide monomers, N-vinyl alkylamide monomers, and acrylonitrile to water, and then adding a tracer and a cross-linking agent, and initiating polymerization under the action of an initiator to obtain a tracer-loaded hydrogel; S2: placing the tracer-loaded hydrogel in a hydrochloric acid solution, hydrolyzing it and then drying it to obtain a tracer sustained-release gel material.

2. The gel material according to claim 1, characterized in that The mass ratio of acrylamide monomers, N-vinyl alkylamide monomers and acrylonitrile is (1-8): (1-4): (0-4), and the mass of the tracer is 5-50% of the total mass of the monomers.

3. The gel material according to claim 1, wherein Acrylamide monomers include one or more of acrylamide, methacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide; N-vinylalkylamide monomers include one or more of N-vinyl-N-methylacetamide, N-vinylacetamide, and N-[3-[3-(dimethylamino)acryloyl]phenyl]-N-ethylacetamide; and tracers include one or more of rare earth oxides, halogenated hydrocarbons, aromatic hydrocarbons, fluorescent dyes, and nitrates.

4. The gel material according to claim 1, wherein Acidic gases include one or more of carbon dioxide, hydrogen sulfide, and sulfur dioxide.

5. The method for preparing the acid gas triggered tracer sustained-release gel material according to any one of claims 1 to 4, characterized in that: Follow these steps: S1: adding acrylamide monomers, N-vinyl alkylamide monomers, and acrylonitrile to water, and then adding a tracer and a cross-linking agent, and initiating polymerization under the action of an initiator to obtain a tracer-loaded hydrogel; S2: placing the tracer-loaded hydrogel in a hydrochloric acid solution, hydrolyzing it and then drying it to obtain a tracer sustained-release gel material.

6. The method according to claim 5, characterized in that The crosslinking agent in S1 includes one of N,N'-methylenebisacrylamide (MBA), polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, and divinylbenzene. The mass of the crosslinking agent is 0.05-0.5% of the total mass of the monomers. The initiator includes peroxides, azo initiators, and photoinitiators.

7. The method according to claim 6, characterized in that Peroxide initiators include ammonium persulfate (APS) and potassium persulfate; azo initiators include azobisisobutylamidine hydrochloride (V-50) and azobisisobutylimidazoline hydrochloride (VA-044); and photoinitiators include one of o-chlorohexaarylbisimidazole, benzoin dimethyl ether, 1-hydroxycyclohexylphenyl ketone, and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

8. The method according to claim 5, characterized in that The polymerization initiation conditions in S1 are 30-60° C. or ultraviolet irradiation, and the polymerization takes 4-24 hours. The concentration of the hydrochloric acid solution in S2 is 0.5-5.0 M, the hydrolysis temperature is 50-150° C., and the time is 1-48 hours.

9. Use of the acid gas triggered tracer sustained-release gel material according to any one of claims 1 to 4 in detecting acid gas.

10. Use of the acid gas triggered tracer slow-release gel material according to any one of claims 1 to 4 in monitoring hydraulic fracturing conditions.

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