Preparation method and application of environment-friendly rare earth tracer

Abstract

The application discloses a preparation method and application of an environment-friendly rare earth tracer, relates to the technical field of oil and gas exploitation, and discloses a rare earth element complex tracer which comprises a rare earth element complex formed by tetrasodium iminodisuccinate (IDS) and a rare earth element nitrate; the rare earth element complex or the rare earth element complex tracer can be applied to oil and gas exploration and development as a tracer. IDS has good solubility and very strong complexing capacity for rare earth elements. The stable rare earth element complex formed by taking IDS as a complexing agent has strong solubility in water, is not easily adsorbed by a core and crude oil when used as a tracer, and has good salt resistance and fracturing fluid compatibility; the application has good application value in oil and gas exploration and development.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploitation, in particular to a preparation method and application of an environment-friendly rare earth tracer. BACKGROUND

[0002] In the development of tight oil and gas, multi-stage fracturing is widely used, and monitoring the fracturing fluid flowback volume and oil and gas production of different fracturing layers has become an important means to improve the effectiveness of measures and reduce development costs. In field practice, the accurate description of the post-fracturing fracture network has become a difficulty in the development of tight oil reservoirs, and to some extent, determines the accuracy of fracturing effect evaluation and production dynamic prediction. The commonly used methods for describing the post-fracturing fracture network are microseismic event monitoring, production dynamic analysis, and fracturing tracer flowback analysis. In actual construction, tracer injection and flowback technology is often used. Because the tracer flows in different fracture systems after fracturing, the flowback curves of the flowback tracers are different, so analyzing the flowback curves of the tracers can determine the shape of the fractures after fracturing and obtain the related parameters of the fractures. At the same time, it can be used to evaluate different fracturing parameters, guide reservoir evaluation, geological design, fracturing design, and work system design.

[0003] As the key carrier of interwell tracer monitoring technology, tracers have been applied very deeply in the field. The commonly used tracers can be divided into the following four categories: chemical, radioactive isotope, stable isotope, and trace substance tracers. A good performance tracer should have the following performances: low background concentration, small injection volume, good stability, less loss in the reservoir, few interference factors, simple detection method, high sensitivity, environmental safety, and low cost. Among the above tracers, the chemical tracer has a large injection volume, high cost, and because of long-term use, the formation accumulates high concentration, and the detection sensitivity is reduced; the radioactive isotope tracer is not environmentally friendly and has high danger; the detection cost and difficulty of the stable isotope tracer are high. The trace substance tracer has small injection volume, low cost, high detection sensitivity, and clean product, and has no pollution to the reservoir, which is the main research and development direction of future tracers.

[0004] Chinese patent CN116574498A discloses a method for measuring the oil production of different reservoirs, using ethylenediaminetetraacetic acid (EDTA) as a complexing agent and a rare earth metal salt to carry out a complexing reaction to obtain a rare earth metal complex as a tracer. However, this technical solution has the following technical defects: first, traditional chelating agents such as EDTA have a slow environmental degradation rate, can chelate harmful heavy metal ions in the environment and increase their activity, leading to these heavy metal ions more easily entering the biological circulation system, posing a threat to human health and environmental safety, and are banned or restricted from use in the textile, washing and other industries by the European Union; second, the flow of the tracer and the injection fluid in the formation is affected by adsorption and desorption in the formation and diffusion and dispersion, which may cause the tracer and the injection fluid to be out of sync in flow time, which will interfere with the accuracy of the monitoring technology. SUMMARY

[0005] (1) Technical problems to be solved

[0006] EDTA has the property of slow degradation, it accumulates in groundwater, surface water and soil. In soil, EDTA, as an acid, lowers the pH value, promotes the desorption of harmful heavy metals (copper, zinc, cadmium, chromium), converting them into soluble forms, making them available to plants, which helps them to be further transferred along the food chain. In addition, EDTA has been shown to disrupt the outer membrane of some soil bacteria. In a recent study, EDTA was found to have cytotoxic and slight genotoxic properties at high concentrations reached due to environmental accumulation. EDTA can be transferred from surface water to humans and animals, having adverse effects on the reproductive function and development of animals. Therefore, according to the World Health Organization, the concentration of EDTA in drinking water should not exceed 600 μg / L.

[0007] As an alternative to EDTA, the present application selects amino polycarboxylate related complexing agents of natural origin. The advantage of iminodisuccinic acid (IDS) is that they form low-toxicity complexes with metals of comparable chelating ability. Its unique degradability has won wide application in many fields. Within the existing technical scope, the degradable performance of IDS is widely used in the technical field of environmental remediation, which helps the soil to restore health and reduce pollution through its degradation. However, there are few reports on the application of IDS in the technical field of oil field tracer. The present application uses IDS as a complexing agent to prepare a new type of water-soluble rare earth tracer by substitution reaction. Through reference to the industry standard "SY / T5925-2012 Selection Method of Oilfield Water Injection Chemical Tracer", the developed tracer is evaluated by indoor experiment, covering a number of tests such as resistance to core and crude oil adsorption, salt tolerance, and compatibility with fracturing fluid, to ensure that the tracer can work effectively in complex environments while meeting the requirements of environmental protection. Such invention and development not only have important significance for improving the efficiency of oilfield exploitation, but also have a positive effect on promoting environmental protection and sustainable development.

[0008] (II) Technical content

[0009] In order to achieve the above technical purpose, solve the technical problems existing in the background art, the present application provides the following solutions:

[0010] The first aspect of the present application provides an environmentally friendly rare earth tracer, specifically an iminodisuccinic acid rare earth complex.

[0011] In the second aspect of the present application, the preparation method of the rare earth element complex tracer provided by the present application, wherein the rare earth element of the rare earth element complex is any one or more than one of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, scandium Sc, yttrium Y, ytterbium Yb and lutetium Lu.

[0012] Preferably, the rare earth element of the rare earth element complex is any one or more than one of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, scandium Sc, yttrium Y, ytterbium Yb and lutetium Lu.

[0013] More preferably, the rare earth element of the rare earth element complex is any one or more than one of lanthanum La, cerium Ce and praseodymium Pr.

[0014] The rare earth element complex tracer provided by the present application, wherein the chemical structure of the rare earth element complex is as follows:

[0015]

[0016] In chemical structure, Ln represents a rare earth element.

[0017] In a second aspect, the present invention provides a method for preparing a rare earth element complex, comprising the following steps:

[0018] (1) providing an aqueous solution of tetrasodium iminodisuccinate as a complexing agent;

[0019] (2) Adding a rare earth element tracer to an aqueous solution of a complexing agent and mixing the mixture to obtain a rare earth element complex solution.

[0020] Preferably, the step (1) is to add a certain amount of the complexing agent tetrasodium iminodisuccinate into water and stir to completely dissolve it.

[0021] Preferably, the step (2) is to slowly add the soluble salt of the rare earth element to the aqueous solution of the complexing agent while stirring until the transparency of the solution no longer changes.

[0022] Preferably, the molar ratio of the rare earth element tracer to the complexing agent is 1:(1-4) calculated as the rare earth element, and the rare earth complex of lanthanum La, cerium Ce, and praseodymium Pr is preferably 1:3.

[0023] The rare earth element tracer is a soluble salt of a rare earth element, including nitrate, chloride, sulfate, etc.

[0024] A third aspect of the present invention provides an application of an environmentally friendly rare earth tracer, wherein a lanthanum iminodisuccinate complex is used as a tracer in oilfield multi-stage fracturing technology. Preferably, the rare earth element complex or a rare earth element complex tracer comprising the rare earth element complex is used as a tracer in oil and gas exploration and development, including in the exploration and development of natural gas, shale gas, coalbed methane, or tight gas. Furthermore, during the fracturing process, the tracer enters the formation simultaneously with the fracturing fluid. During fracturing flowback, the flowback fluid is sampled and tested at regular intervals to obtain a tracer flowback curve. By interpreting the tracer flowback curve, the reservoir fracturing effect can be analyzed, the fracture development can be judged, and a basic basis for the optimization of subsequent fracturing process design can be provided.

[0025] (3) Beneficial effects

[0026] (1) The present invention uses IDS as a chelating agent and is applied in the technical field of field tracers. The degradability of IDS can avoid the use of traditional chelating agents such as EDTA, thereby preventing EDTA from chelating harmful heavy metal ions in the environment and increasing their activity, which makes it easier for these heavy metal ions to enter the biological circulation system and pose a threat to human health and environmental safety.

[0027] (2) The application prepares a new water-soluble rare earth tracer by a substitution reaction method, and through a plurality of tests such as crude oil and core adsorption tests, formation water compatibility, fracturing fluid compatibility and the like. The loss rates of the iminodisuccinic acid lanthanide complex tracers in static adsorption are controlled at a low level. They have good compatibility with formation water and fracturing fluid, meet the standard of "SY / T 5925-2012 Selection Method of Oilfield Water Injection Chemical Tracer", and are suitable for field use. BRIEF DESCRIPTION OF DRAWINGS

[0028] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0029] Figure 1 Retention rate of rare earth element tracer La-IDS, Ce-IDS and Pr-IDS in core adsorption performance evaluation experiment;

[0030] Figure 2 Retention rate of rare earth element tracer La-IDS, Ce-IDS and Pr-IDS in crude oil adsorption performance evaluation experiment;

[0031] Figure 3 Retention rate of rare earth element tracer La-IDS, Ce-IDS and Pr-IDS in anti-interference performance evaluation experiment;

[0032] Figure 4 Retention rate of rare earth element tracer La-IDS, Ce-IDS and Pr-IDS in fracturing fluid; DETAILED DESCRIPTION

[0033] The preferred embodiments of the environment-friendly rare earth tracer and application thereof will be described in detail below with reference to the accompanying drawings.

[0034] Example 1: Preparation of iminodisuccinic acid lanthanum tracer

[0035] An appropriate amount of IDS is weighed in a suitable container, and a sufficient amount of solvent (such as distilled water) is added, and stirred until completely dissolved. After cooling, the solution is transferred to a container with a suitable volume, and is diluted to the required volume to obtain an IDS solution with a certain concentration. Then, an appropriate amount of lanthanum nitrate hexahydrate (La(NO3)3·6H2O) is weighed, and an appropriate amount of solvent is added, and stirred until completely dissolved. After cooling, the solution is transferred to a container with a suitable volume, and is diluted to the required volume to obtain a La(NO3)3 solution with a certain concentration.

[0036] The prepared La(N03)3 solution is mixed with the IDS solution in a molar ratio of 1 :3 and stirred uniformly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (for example, 20-50°C), and stirring is performed for a sufficient time to ensure that the reaction is complete, thereby obtaining a La-IDS solution with a target concentration.

[0037] Finally, the solution is removed from the heating device, placed in a drying device, and set to an appropriate temperature (for example, 60-80°C) for drying to a constant weight, thereby obtaining a La-IDS complex crystal.

[0038] Example 2: Preparation of Cerium Imidosuccinate Tracer

[0039] An appropriate amount of IDS is weighed into a suitable container, and a sufficient amount of solvent (for example, distilled water) is added and stirred until completely dissolved. After cooling, the solution is transferred to a container with an appropriate volume, and the volume is adjusted to the desired volume, thereby obtaining an IDS solution with a certain concentration. Next, an appropriate amount of cerium nitrate hexahydrate (Ce(N03)3-6H20) is weighed, an appropriate amount of solvent is added, and stirring is performed until complete dissolution. After cooling, the solution is transferred to a container with an appropriate volume, and the volume is adjusted to the desired volume, thereby obtaining a Ce(N03)3 solution with a certain concentration.

[0040] The prepared Ce(N03)3 solution is mixed with the IDS solution in a molar ratio of 1 :3 and stirred uniformly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (for example, 20-50°C), and stirring is performed for a sufficient time to ensure that the reaction is complete, thereby obtaining a Ce-IDS solution with a target concentration.

[0041] Finally, the solution is removed from the heating device, placed in a drying device, and set to an appropriate temperature (for example, 60-80°C) for drying to a constant weight, thereby obtaining a Ce-IDS complex crystal.

[0042] Example 3: Preparation of Praseodymium Imidosuccinate Tracer

[0043] An appropriate amount of IDS is weighed into a suitable container, and a sufficient amount of solvent (for example, distilled water) is added and stirred until completely dissolved. After cooling, the solution is transferred to a container with an appropriate volume, and the volume is adjusted to the desired volume, thereby obtaining an IDS solution with a certain concentration. Next, an appropriate amount of praseodymium nitrate hexahydrate (Pr(N03)3-6H20) is weighed, an appropriate amount of solvent is added, and stirring is performed until complete dissolution. After cooling, the solution is transferred to a container with an appropriate volume, and the volume is adjusted to the desired volume, thereby obtaining a Pr(N03)3 solution with a certain concentration.

[0044] The prepared Pr(NO3)3 solution and the IDS solution are mixed in a molar ratio of 1:3 and stirred uniformly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (for example, 20-50°C), and the solution is stirred for a sufficient time to ensure that the reaction is complete, and a Pr-IDS solution with a target concentration is obtained.

[0045] Finally, the solution is taken out of the heating device and placed in a drying device, an appropriate temperature (for example, 60-80°C) is set, and drying is performed to a constant weight to obtain a Pr-IDS complex crystal.

[0046] Application Example

[0047] In order to verify that the rare earth element complex introduced in the present application can work effectively as a tracer in the complex environment of oilfield fracturing exploitation, the developed tracer is comprehensively evaluated in laboratory experiments by referring to the industry standard “SY / T 5925 Selection Method of Oilfield Water Injection Chemical Tracer”. The following tests are carried out by the present applicant:

[0048] Example 4: Example 4 is an evaluation experiment of the anti-core adsorption performance of the tracers prepared in Examples 1-3

[0049] An appropriate amount of core sample is weighed, ground and sieved as appropriate, and samples within a specific particle size range are retained and placed in a container. Then a certain volume and concentration of Ln-IDS solution is added. The container is placed in a suitable stirring device or oscillation device and subjected to oscillation treatment at a constant temperature for a certain period of time. During the oscillation process, the treated solution is periodically analyzed, for example by inductively coupled plasma mass spectrometry (ICP-MS) method, to measure the retention rate of Ln-IDS in the solution. In this way, the ability of the solution to resist rock adsorption can be evaluated, and the experimental evaluation results are shown in Table 1. Figure 1

[0050] The loss rates of the mixed solutions of the three rare earth tracers and core powder after oscillation at formation temperature for 6 days are all less than 5%, and the retention rates of La-IDS, Ce-IDS and Pr-IDS are 94.65%, 94.52% and 94.13% respectively, which meet the standard of “SY / T 5925-2012 Selection Method of Oilfield Water Injection Chemical Tracer”.

[0051] Example 5: Example 5 is an evaluation test of the anti-oil adsorption performance of the tracers prepared in Examples 1-3

[0052] ​Prepare multiple containers and mix crude oil with Ln-IDS solution of certain concentration in appropriate proportion to configure multiple test samples. Place these samples in appropriate oscillation equipment and perform oscillation treatment at constant temperature for a certain period of time. During the oscillation process, periodically analyze the treated Ln-IDS solution, for example, by inductively coupled plasma mass spectrometry, to determine the retention rate of Ln-IDS. Evaluate the performance of Ln-IDS in resisting adsorption of crude oil by this method, and the experimental evaluation results are shown in Table 1. Figure 2

[0053] The loss rates of the mixed solutions of the three rare earth tracers and crude oil are all less than 5% after oscillation at formation temperature for 6 days, and the retention rates of La-IDS, Ce-IDS and Pr-IDS are 94.55%, 94.49% and 94.05% respectively, indicating that the anti-adsorption performance is good and meets the standard of SY / T 5925-2012 Selection Method of Oilfield Water Injection Chemical Tracer.

[0054] Example 6: Example 6 is a formation water compatibility test of the tracers prepared in Examples 1-3

[0055] Weigh an appropriate amount of formation water sample to prepare solutions of La-IDS, Ce-IDS and Pr-IDS of certain concentration, and observe the compatibility of rare earth element tracers in formation water after oscillation at formation temperature for 7 days. The experimental evaluation results are shown in Table 2. The retention rates of La-IDS, Ce-IDS and Pr-IDS are 99.05%, 98.92% and 98.76% respectively, which meets the standard of SY / T 5925-2012 Selection Method of Oilfield Water Injection Chemical Tracer. In the high salinity environment of formation water, the strong coordination between rare earth elements and complexing agents can effectively resist the interference of salt ions and maintain the stability of the tracer. Figure 3

[0056] Example 7: Example 7 is a fracturing fluid compatibility test of the tracers prepared in Examples 1-3

[0057] Use a pipette to take an appropriate amount of Ln-IDS solution and transfer it to a container with appropriate volume, then dilute it to the required volume with fracturing fluid to prepare an Ln-IDS fracturing fluid mixed solution of a certain concentration.

[0058] ​​Next, an appropriate amount of Ln-IDS fracturing fluid solution is accurately taken out and transferred to multiple test tubes. These test tubes are placed in a constant temperature oscillation device, adjusted to an appropriate temperature and oscillation frequency, and kept at a constant temperature for a period of time. During the experiment, the Ln-IDS fracturing fluid solution is regularly tested, for example, using the ICP-MS method to evaluate the retention rate of the Ln-IDS rare earth tracer in the fracturing fluid. This process reflects the compatibility of the Ln-IDS solution with the fracturing fluid. The experimental evaluation results are as follows: Figure 4 shown.

[0059] According to experimental results, after 72 hours of continuous shaking, the fluid containing the three tracers remained transparent, showing no signs of turbidity or precipitation. This study demonstrated extremely high retention rates of these tracers, reaching 99.26%, 99.17%, and 98.97%, respectively. Furthermore, the loss rate of these tracers in a specific fracturing fluid was very low, not exceeding 1.5%. This result demonstrates the excellent compatibility of Ln-IDS with fracturing fluids.

[0060] The above are only preferred embodiments of the present invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

[0061] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The description of the present invention by the embodiments should be understood as the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it is not intended that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An application of a rare earth tracer, characterized in that: The tracer is an iminodisuccinate rare earth element complex, the application is the application of the complex in oil and gas exploration and development, and the rare earth element of the rare earth element complex is one or more of lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, scandium Sc, yttrium Y, ytterbium Yb, and lutetium Lu.

2. The use according to claim 1, characterized in that: The oil and gas include natural gas, shale gas, coalbed methane and tight gas.

3. The use according to claim 1, characterized in that Including application in shale horizontal well connectivity detection.

4. The use according to any one of claims 1 to 3, characterized in that The rare earth element of the rare earth element complex is any one or more of lanthanum La, cerium Ce, and praseodymium Pr.

5. The use according to any one of claims 1 to 3, characterized in that The preparation method of the rare earth element complex comprises the following steps: (1) providing an aqueous solution of tetrasodium iminodisuccinate complexing agent; (2) Adding nitrate of a rare earth element to an aqueous solution of a complexing agent and mixing the mixture to obtain a rare earth element complex solution.

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