Preparation method and application of environment-friendly rare earth tracer agent

Abstract

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

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploitation, and in particular to a preparation method and application of an environmentally friendly rare earth tracer. Background Art

[0002] In the development of tight oil and gas, multi-stage fracturing is widely used. Among them, monitoring the flowback volume of fracturing fluid and oil and gas production in different fracturing layers has become an important means to improve the benefits of measures and reduce development costs. In field practice, the accurate description of the fracture network after fracturing has become a difficulty in the development of tight oil reservoirs, and to a certain extent determines the accuracy of fracturing effect evaluation and production dynamic prediction. The commonly used methods for describing the fracture network after fracturing are generally microseismic event monitoring, production dynamic analysis, and fracturing tracer flowback analysis. In actual on-site construction, tracer injection and flowback technology is often used. Since the tracer seeps in different fracture systems after fracturing, the flowback curves of the discharged tracer are also different. Therefore, by analyzing the tracer flowback curve, the morphology of the fracture after fracturing can be determined and the fracture-related parameters can be obtained. At the same time, it can be used to evaluate different fracturing parameters and guide reservoir evaluation, geological design, fracturing design, and work system design.

[0003] As the key carrier of inter-well tracer monitoring technology, tracers have been deeply applied in the field. Commonly used tracers can be mainly divided into the following four categories: chemical, radioisotope, stable isotope, and trace substance tracers. Excellent tracers should have the following properties: low background concentration, small injection amount, good stability, less loss in the reservoir, fewer interference factors, simple detection method, high sensitivity, environmental protection and safety, and low cost. Among the above types of tracers, chemical tracers have large injection amounts and high costs, and due to long-term use, the accumulated concentration in the formation is too high, and the detection sensitivity is reduced; radioisotope tracers have certain radioactivity and are not environmentally friendly, and are more dangerous; the detection cost and difficulty of stable isotope tracers are relatively high. Trace substance tracers, with small injection amounts, low costs, high detection sensitivity, clean products and no pollution to the reservoir, are the main research and development direction of tracers in the future.

[0004] Chinese patent CN116574498A discloses a method for measuring the oil production of different reservoirs, using ethylenediaminetetraacetic acid (EDTA) as a chelating agent and rare earth metal salts for complexing reaction, and obtaining rare earth metal complexes as tracers. However, this technical solution has the following technical defects: first, traditional chelating agents such as EDTA can chelate harmful heavy metal ions in the environment and increase their activity due to their slow environmental degradation rate, making these heavy metal ions more likely to enter the biological circulation system, posing a threat to human health and environmental safety, and are banned or restricted by the European Union in the textile, detergent and other industries; second, the flow of the tracer and the injected fluid in the formation will be affected by formation adsorption and desorption as well as diffusion and dispersion, and these factors may cause the tracer and the injected fluid to be out of sync in flow time, which will interfere with the accuracy of the monitoring technology. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] EDTA has the property of slow degradation, and it accumulates in groundwater, surface water, and soil. In soil, EDTA acts as an acid, lowering the pH value and promoting the desorption of harmful heavy metals (copper, zinc, cadmium, chromium), converting them into soluble forms, making them available for plant absorption, which facilitates their further transfer along the trophic chain. In addition, EDTA has been shown to be able to destroy the outer membrane of some soil bacteria. In recent studies, it was found that when high concentrations are reached due to environmental accumulation, EDTA is even cytotoxic and slightly genotoxic. EDTA may be transferred from surface water to humans and animals, adversely affecting the reproductive function and development of animals. Therefore, according to the World Health Organization, the concentration of EDTA in drinking water should not exceed 600μg / L.

[0007] As a substitute for EDTA, the present invention selects a complexing agent related to amino polycarboxylates of natural origin. The advantage of iminodisuccinic acid (IDS) is that it forms low-toxic complexes with metals with comparable chelating ability. Its unique degradability has won it a wide range of applications in many fields. Within the existing technical scope, the degradable performance of IDS is widely used in the technical field of environmental remediation. Through its degradation effect, it helps the soil to restore health and reduce pollution. However, in the technical field of oilfield tracers, the application of IDS is rarely reported. The present invention uses IDS as a complexing agent and uses a substitution reaction method to prepare a new water-soluble rare earth tracer. By referring to the industry standard "SY / T5925-2012 Selection Method of Oilfield Water Injection Chemical Tracers", the developed tracer is evaluated by indoor experiments, covering multiple tests of resistance to core and crude oil adsorption, salt resistance, and compatibility with fracturing fluids, to ensure that the tracer can work effectively in a complex environment while meeting the requirements of environmental protection. Such inventions and developments are not only of great significance to improving oil field extraction efficiency, but also play a positive role in promoting environmental protection and sustainable development.

[0008] (II) Technical content

[0009] In order to achieve the above technical objectives and solve the technical problems existing in the background technology, the present invention provides the following solutions:

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

[0011] In a second aspect of the present invention, a method for preparing a rare earth element complex tracer is provided according to the present invention, wherein the rare earth element of the rare earth element complex is any 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.

[0012] Preferably, the rare earth element of the rare earth element complex is any 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.

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

[0014] According to the rare earth element complex tracer provided by the present invention, 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, mixing the mixture, and obtaining 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 into 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) based on 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 and the like.

[0024] The third aspect of the present invention is to provide an application of an environmentally friendly rare earth tracer, and the lanthanum iminodisuccinate complex is used as a tracer in the multi-stage fracturing technology of oil fields. Preferably, the rare earth element complex or the rare earth element complex tracer including 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. Further, during the fracturing process, it enters the formation synchronously with the fracturing fluid. When the fracturing is returned, the return fluid is sampled and tested intensively at a certain interval to obtain a tracer return curve. By interpreting the tracer return curve, the reservoir fracturing effect can be analyzed, the fracture development can be judged, and a basic basis can be provided for the optimization of the later fracturing process design.

[0025] (III) 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, posing a threat to human health and environmental safety.

[0027] (2) The present invention uses a substitution reaction method to prepare a new type of water-soluble rare earth tracer, which passes a number of tests such as crude oil and core adsorption tests, formation water compatibility, and fracturing fluid compatibility. The loss rate of the lanthanum iminodisuccinate complex tracer in terms of static adsorption is controlled at a low level. They have good compatibility with formation water and fracturing fluid, meet the standards of "SY / T 5925-2012 Selection Method of Oilfield Water Injection Chemical Tracers", and are suitable for field use. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

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

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

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

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

[0033] The preferred embodiments of the environmentally friendly rare earth tracer and its application of the present invention are described in detail below with reference to the accompanying drawings.

[0034] Example 1: Preparation of lanthanum iminodisuccinate tracer

[0035] Weigh an appropriate amount of IDS into a suitable container, add sufficient solvent (such as distilled water), and stir until completely dissolved. After cooling, transfer the solution to a container of appropriate volume and dilute to the required volume to obtain an IDS solution of a certain concentration. Next, weigh an appropriate amount of lanthanum nitrate hexahydrate (La(NO 3 ) 3 6H 2 O), add an appropriate amount of solvent and stir until completely dissolved. After cooling, transfer the solution to a container of appropriate volume and dilute to the required volume to obtain a certain concentration of La(NO 3 ) 3 Solution.

[0036] The prepared La(NO 3 ) 3The solution is mixed with the IDS solution at a molar ratio of 1:3 and stirred evenly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (e.g., 20-50° C.), and stirred for a sufficient time to ensure sufficient reaction to obtain a La-IDS solution of the target concentration.

[0037] Finally, the solution is taken out from the heating device, placed in a drying device, set at a suitable temperature (such as 60-80° C.), and dried to a constant weight to obtain La-IDS complex crystals.

[0038] Example 2: Preparation of cerium iminodisuccinate tracer

[0039] Weigh an appropriate amount of IDS into a suitable container, add sufficient solvent (such as distilled water), and stir until completely dissolved. After cooling, transfer the solution to a container of suitable volume and dilute to the required volume to obtain an IDS solution of a certain concentration. Next, weigh an appropriate amount of cerium nitrate hexahydrate (Ce(NO 3 ) 3 6H 2 O), add an appropriate amount of solvent and stir until completely dissolved. After cooling, transfer the solution to a container of suitable volume and dilute to the required volume to obtain a certain concentration of Ce(NO 3 ) 3 Solution.

[0040] The prepared Ce(NO 3 ) 3 The solution is mixed with the IDS solution at a molar ratio of 1:3 and stirred evenly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (e.g., 20-50° C.), and stirred for a sufficient time to ensure sufficient reaction, thereby obtaining a Ce-IDS solution of the target concentration.

[0041] Finally, the solution is taken out from the heating device, placed in a drying device, set at a suitable temperature (eg, 60-80° C.), and dried to a constant weight to obtain Ce-IDS complex crystals.

[0042] Example 3: Preparation of praseodymium iminodisuccinate tracer

[0043] Weigh an appropriate amount of IDS into a suitable container, add sufficient solvent (such as distilled water), and stir until completely dissolved. After cooling, transfer the solution to a container of appropriate volume and dilute to the required volume to obtain an IDS solution of a certain concentration. Next, weigh an appropriate amount of praseodymium nitrate hexahydrate (Pr(NO 3 ) 3 6H 2O), add an appropriate amount of solvent and stir until completely dissolved. After cooling, transfer the solution to a container of appropriate volume and dilute to the required volume to obtain a certain concentration of Pr(NO 3 ) 3 Solution.

[0044] The prepared Pr(NO 3 ) 3 The solution is mixed with the IDS solution at a molar ratio of 1:3 and stirred evenly. Then, the mixed solution is placed in a heating and stirring device, the temperature is adjusted to an appropriate range (e.g., 20-50° C.), and stirred for a sufficient time to ensure sufficient reaction to obtain a Pr-IDS solution of the target concentration.

[0045] Finally, the solution is taken out from the heating device, placed in a drying device, set at a suitable temperature (such as 60-80° C.), and dried to a constant weight to obtain Pr-IDS complex crystals.

[0046] Application Examples

[0047] In order to verify that the rare earth element complex introduced in this application can work effectively as a tracer in the complex environment of oilfield fracturing and exploitation, the developed tracer was comprehensively evaluated in indoor experiments by referring to the industry standard "SY / T 5925 Selection Method of Oilfield Water Injection Chemical Tracers". The applicant conducted the following experiments:

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

[0049] Weigh an appropriate amount of core sample, grind and sieve appropriately, retain samples within a specific particle size range, and place them in a container. Then add a certain volume and concentration of Ln-IDS solution. Place the container in an appropriate stirring device or oscillating device and oscillate it at a constant temperature for a certain period of time. During the oscillation process, the treated solution is analyzed regularly, for example, by inductively coupled plasma mass spectrometry (ICP-MS) 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. The experimental evaluation results are as follows: Figure 1 shown.

[0050] After oscillating for 6 days at formation temperature, the loss rate of the mixed solution of three rare earth tracers and core powder was less than 5%. The retention rates of La-IDS, Ce-IDS and Pr-IDS were 94.65%, 94.52% and 94.13%, respectively, which met the standards of "SY / T5925-2012 Selection Method of Chemical Tracers for Oilfield Water Injection".

[0051] Example 5: Example 5 is to test the antigen oil adsorption performance of the tracer prepared in Examples 1-3

[0052] Prepare multiple containers, and mix crude oil with a certain concentration of Ln-IDS solution in an appropriate ratio to prepare multiple test samples. Place these samples in an appropriate oscillating device and oscillate them at a constant temperature for a certain period of time. During the oscillation process, the treated Ln-IDS solution is regularly analyzed, for example, by inductively coupled plasma mass spectrometry to determine the retention rate of Ln-IDS. This method is used to evaluate the performance of Ln-IDS in resisting crude oil adsorption. The experimental evaluation results are as follows: Figure 2 shown.

[0053] After oscillating for 6 days at formation temperature, the loss rate of the mixed solution of the three rare earth tracers and crude oil was less than 5%. The retention rates of the three tracers, La-IDS, Ce-IDS and Pr-IDS, were 94.55%, 94.49% and 94.05%, respectively, indicating that they have good anti-adsorption properties and meet the standards of "SY / T 5925-2012 Selection Method of Chemical Tracers for Oilfield Water Injection".

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

[0055] Weigh appropriate amounts of formation water samples to prepare solutions of La-IDS, Ce-IDS and Pr-IDS of certain concentrations, and after oscillating at formation temperature for 7 days, observe the compatibility of rare earth element tracers in formation water. Figure 3 As shown. The retention rates of La-IDS, Ce-IDS and Pr-IDS are 99.05%, 98.92% and 98.76% respectively, which meet the standards of "SY / T5925-2012 Selection Method of Chemical Tracers for Oilfield Water Injection". In the high salinity environment of formation water, the strong coordination effect between rare earth elements and complexing agents can effectively resist the interference of salt ions and maintain the stability of the tracer.

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

[0057] Use a pipette to take an appropriate amount of Ln-IDS solution and transfer it to a container of appropriate volume, then dilute it with fracturing fluid to the required volume to prepare a Ln-IDS fracturing fluid mixed solution of a specific 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 the experimental results, after 72 hours of continuous oscillation, the liquid containing the three tracers remained transparent without any turbidity or precipitation. This study found that the retention rates of these tracers were extremely high, reaching 99.26%, 99.17% and 98.97% respectively. Moreover, in a specific fracturing fluid, the loss rate of these tracers was very low, not exceeding 1.5%. This result shows that Ln-IDS has good compatibility with fracturing fluid.

[0060] The above are only preferred embodiments of the present invention. It should be pointed out that a person 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 protection scope 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 does not mean 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 functions.

Claims

1. An environmentally friendly rare earth tracer, characterized in that: The tracer is the application of lanthanum iminodisuccinate complex in oil and gas exploration and development.

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 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.

5. The use according to any one of claims 1 to 4, 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.

6. The use according to any one of claims 1 to 5, 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 a rare earth element tracer to an aqueous solution of a complexing agent, mixing the mixture, and obtaining a rare earth element complex solution.

7. The use according to claim 6, characterized in that: The molar ratio of the rare earth element tracer to the complexing agent is 1:(1-4) based on the rare earth element; and / or the rare earth element tracer is a water-soluble complex of the rare earth element.

8. A rare earth element complex tracer, characterized in that: The rare earth element complex tracer includes a rare earth element complex formed by tetrasodium iminodisuccinate and a rare earth element tracer; the rare earth element of the rare earth element complex tracer is any 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.

9. The rare earth element complex tracer according to claim 8, characterized in that: The rare earth element of the rare earth element complex tracer is any one or more of lanthanum La, cerium Ce, and praseodymium Pr.

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