Tracer and fracturing implementation effect evaluation device based on tracer

Abstract

The present invention provides a tracer and a fracturing implementation effect evaluation device based on the tracer. The tracer comprises: a rare earth element compound, a composite complexing agent, and a compatibility additive, wherein the composite complexing agent comprises a phenanthroline-based compound and ethylenediaminetetraacetic acid. The device comprises: a tracer preparation apparatus; a pumping apparatus connected to the tracer preparation apparatus and used for putting the prepared tracer into a stratum; a tracer detection apparatus comprising a flowback fluid treatment apparatus for receiving and treating flowback fluid and an analysis instrument for detecting and analyzing the tracer in the flowback fluid; and a central control apparatus connected to and controlling the tracer preparation apparatus, the pumping apparatus, and the tracer detection apparatus, wherein the central control apparatus obtains fracturing implementation effect data on the basis of an analysis result of the analysis instrument.

Description

Tracer and device for evaluating fracturing effect using tracer

[0001] This application claims priority to Chinese patent application CN 202310855402.9, filed on July 12, 2023, entitled “A tracer and an integrated device and method for its preparation, pumping and monitoring,” and the entire contents of CN 202310855402.9 are incorporated herein by reference. Technical Field

[0002] The invention relates to a tracer and equipment for evaluating the effect of fracturing by using the tracer, and belongs to the technical field of shale oil and gas exploration and development. Background Art

[0003] Chemical, radioisotope, non-radioisotope, and rare earth element (REE) tracers are widely used in interwell tracing technology in oil and gas fields. Chemical tracers, primarily represented by various inorganic salts, dyes, halogenated hydrocarbons, and alcohols, are gradually being phased out due to their high dosage, high cost, poor adaptability, and low test accuracy. Radioisotope tracers require less dosage and offer high accuracy, but their deployment and detection require specialized personnel and departments and present potential radioactive hazards, limiting their application. Non-radioisotope tracers share the advantages of radioisotope tracers without the potential radioactive hazards, but require reactor activation, so their detection still requires specialized personnel. Rare earth element (REE) tracer technology is the latest tracing technology, primarily utilizing trace elements present in the formation as test tracers. It offers advantages such as safety, stability, a wide variety, low dosage, and high accuracy, and holds broad application prospects. However, for the fluid tracing technology required in the current unconventional oil and gas exploration and development process, the existing rare earth element tracer technology is not applicable due to differences in geological characteristics and exploration and development technology. The specific reasons are: (1) Compared with the geological characteristics of conventional oil and gas reservoirs, shale oil and gas reservoirs have the characteristics of low porosity, low permeability, high organic matter content and high clay mineral content, which leads to a significant increase in the adsorption capacity of the formation for fluids and tracers, so that trace amounts of rare earth element tracers may be adsorbed by the underground rock formation and cannot be detected; (2) Compared with conventional oil and gas reservoir development technology, shale oil and gas reservoir development also requires horizontal well drilling and supporting hydraulic fracturing technology. On the one hand, it is necessary to avoid the reaction between the tracer and the components of the fracturing fluid, and on the other hand, it is also necessary to consider the dilution effect of the fracturing fluid itself on the tracer concentration.

[0004] Using complexing agents to form complexes with rare earth elements is an effective method for protecting them from adsorption by formations. However, existing rare earth element complexing agents, when used as tracers in oil and gas exploration, suffer from poor solubility, insufficient complexing capacity, and susceptibility to formation adsorption, which compromises the accuracy of tracer applications.

[0005] Considering the above, existing tracers fail to effectively account for the low-porosity, low-permeability, and dense formation characteristics of shale oil and gas reservoirs, as well as the complexity and specificity of fracturing fluid composition. In practical applications, they are prone to numerous issues, such as being heavily adsorbed by the formation, making it impossible to monitor and affect the performance of the original fracturing fluid, significantly impacting implementation effectiveness. Therefore, it is necessary to develop new tracers tailored to the specific characteristics of shale oil and gas exploration and development.

[0006] Summary of the Invention

[0007] In response to the above-mentioned technical problems existing in the prior art, the present invention proposes a tracer and a device for evaluating the effectiveness of fracturing implementation using the tracer. The tracer is more suitable for shale oil and gas exploration and development. Combined with the device, the tracer preparation, pumping, collection, processing and monitoring can be integrated and automated, providing scientific data for optimizing shale oil and gas exploration and development plans and horizontal well deployment decisions.

[0008] According to a first aspect of the present invention, a tracer is provided, comprising a rare earth element compound, a composite complexing agent and a compatible additive, wherein the composite complexing agent comprises a phenanthroline compound and ethylenediaminetetraacetic acid.

[0009] A further improvement of the present invention is that the mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive is 1:(0.5-1):(0.01-0.1); and / or

[0010] The mass ratio of the ethylenediaminetetraacetic acid to the phenanthroline compound is 1:(0.01-0.5).

[0011] A further improvement of the present invention is that the mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive is 1:(0.8-1):(0.01-0.05).

[0012] A further improvement of the present invention is that the phenanthroline compound has a structure as shown in Formula I:

[0013] wherein R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, halogen, CN, NO2, C1-C8 alkyl, halogenated C1-C8 alkyl, C1-C8 alkoxy, halogenated C1-C8 alkoxy, C1-C8 alkylthio, halogenated C1-C8 alkylthio, C1-C8 alkylsulfinyl, halogenated C1-C8 alkylsulfinyl, C1-C8 alkylsulfonyl, halogenated C1-C8 alkylsulfonyl, aryl, halogenated sulfoaryl, carboxyl, C1-C8 alkylcarboxyl, halogenated C1-C8 alkylcarboxyl, C1-C8 alkyl-substituted C1-C8 alkylcarboxyl-substituted amino.

[0014] A further improvement of the present invention is that, in Formula I, R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, phenyl, chlorosulfonylphenyl, carboxyl and -CH2N(CH2COOH)2.

[0015] A further improvement of the present invention is that the phenanthroline compound is selected from at least one of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline), 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline and 4,7-dichlorosulfonylbenzene-2,9-dicarboxylic acid-1,10-phenanthroline.

[0016] A further improvement of the present invention is that the rare earth element in the rare earth element compound is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0017] A further improvement of the present invention is that the rare earth element compound is a soluble salt of the rare earth element, preferably at least one of a nitrate, a chloride and a sulfate.

[0018] A further improvement of the present invention is that the compatibility additive is selected from at least one of gum arabic, xanthan gum, natural rubber, casein, casein, casein and sodium alginate.

[0019] The first aspect of the present invention provides the use of the tracer in shale oil and gas exploration and development.

[0020] According to a second aspect of the present invention, a device for evaluating the effect of fracturing by using a tracer is provided. The tracer is the tracer provided in the first aspect of the present invention. The device comprises:

[0021] Tracer preparation device;

[0022] A pumping device connected to the tracer preparation device to inject the prepared tracer into the formation;

[0023] a tracer detection device, comprising a flowback fluid processing device for receiving and processing the flowback fluid and an analysis instrument for detecting and analyzing the tracer in the flowback fluid; and

[0024] a central control device, the central control device being connected to and controlling the tracer preparation device, the pumping device and the tracer monitoring device;

[0025] The central control device obtains the fracturing effect data according to the analysis results of the analysis instrument.

[0026] A further improvement of the present invention is that the tracer preparation device includes a liquid preparation tank, the inlet of the liquid preparation tank is connected to an external water supply source through a liquid inlet pipeline, and the outlet of the liquid preparation tank is connected to a pumping device through a liquid outlet pipeline;

[0027] At least one reagent delivery bin is provided on the upper portion of the liquid preparation bin, wherein the reagent delivery bin contains raw material reagents for preparing the tracer;

[0028] A stirring device is provided inside the liquid preparation bin, and the stirring device is provided below the reagent delivery bin; a filter is provided below the stirring device.

[0029] A further improvement of the present invention is that a weight meter is provided on the reagent delivery bin for detecting the weight information of the reagent delivery bin in real time and transmitting the weight information to the central control device; the central control device controls the opening and closing of the reagent delivery bin according to the weight information;

[0030] The liquid inlet pipeline is provided with a sewage filtering and purifying device, which comprises a tank body, an inlet end of which is provided with a pressure regulating valve; and the interior of the tank body is provided with a filter screen and a particle recovery bin.

[0031] A further improvement of the present invention is that the analytical instrument comprises a portable inductively coupled plasma mass spectrometer; the inlet of the analytical instrument is connected to the outlet of a flowback liquid processing device via a flowback liquid pipeline, and the inlet end of the flowback liquid processing device is externally connected to a manifold fluid separator;

[0032] The flowback liquid treatment device includes a flowback liquid filtration and purification device, and a flowback liquid separation and constant volume device is provided downstream of the flowback liquid filtration and purification device;

[0033] The return liquid separation and volume setting device is connected to the analytical instrument through a return liquid pipeline, and the return liquid separation and volume setting device is also provided with a discharge nozzle.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] In the tracer of the present invention, the phenanthroline compound and ethylenediaminetetraacetic acid in the composite complexing agent synergistically enhance their effectiveness under specific quantitative relationships, and the composite complexing agent and the compatible additive synergistically enhance their effectiveness under specific quantitative relationships, so that the rare earth elements in the tracer can be very effectively protected, the adsorption amount in shale formations is significantly reduced, and a high rare earth element retention rate can be maintained (at room temperature, in a fracturing fluid with a shale content of 20% by weight, the retention rate of the rare earth elements contained in the tracer is higher than 70%, and can reach a maximum of 92.5%). In addition, the tracer has good compatibility with the fracturing fluid, the stability of the tracer in the fracturing fluid is little affected by the components of the fracturing fluid, and its addition has little effect on the viscosity of the fracturing fluid. In addition, the tracer can significantly improve the sedimentation stability of the proppant in the fracturing fluid.

[0036] The tracer exhibits excellent high-temperature performance (at 95°C, the retention rate of the rare earth elements contained in the tracer exceeds 65%, reaching a maximum of 92.8%). Compared to existing tracers, the tracer provided by the present invention is more suitable for shale formations and can continue to perform its monitoring function effectively and continuously in an environment with dual dilution effects from fracturing fluids and formation fluids, meeting the current technical requirements of shale oil and gas exploration and development.

[0037] The tracer provided by the present invention is highly safe and environmentally friendly, and its usage concentration in the fracturing fluid is below 10 ppm, reaching the food-grade industrial dosage standard for rare earth elements, and hardly causes pollution to the underground.

[0038] The device described in the present invention for evaluating the effectiveness of fracturing by using tracers realizes the integration and automation of tracer preparation, pumping, collection, processing and monitoring, and provides scientific data for optimizing shale oil and gas exploration and development plans and horizontal well deployment decisions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, which are not drawn to scale.

[0040] FIG1 is a schematic diagram of an apparatus for evaluating the effect of fracturing by using a tracer according to an embodiment of the present invention. The meanings of the reference numerals in FIG1 are as follows:

[0041] 101. Water supply source; 102. First valve; 103. Sewage filtration and purification device; 104. Second valve; 105. Inlet; 106. Liquid preparation tank; 107. First reagent delivery tank; 108. Second reagent delivery tank; 109. Third reagent delivery tank; 110. Agitation device; 111. Filter screen; 112. Outlet; 113. Third valve; 114. Horizontal flow pump; 115. Fourth valve; 116. Sand blender; 117. Manifold fluid separator; 118. Fourth valve; 119. Return liquid filtration and purification device; 120. Fifth valve; 121. Return liquid separation and constant volume device; 122. Sixth valve; 123. Discharge port; 124. Return liquid pipeline; 125. Inductively coupled plasma mass spectrometer; 126. Central control circuit; 127. Central control device; 128. Central control circuit.

[0042] FIG2 shows the relative position information of wells 10-1HF and 10HF in a shale gas field in Example 15.

[0043] Figure 3 shows the monitoring of rare earth element concentrations in the flowback fluid of Well 10-1HF over a period of 55 days.

[0044] Figure 4 shows the monitoring of rare earth element concentrations in the flowback fluid of Well 10HF over a period of 67 days. DETAILED DESCRIPTION

[0045] To make the technical solutions and advantages of the present invention more clearly understood, exemplary embodiments of the present invention are further described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are only a portion of the embodiments of the present invention, and are not exhaustive. Furthermore, the embodiments and features of the embodiments of the present invention may be combined with each other unless there is a conflict.

[0046] According to one aspect of the present invention, a tracer is provided, comprising a rare earth element compound, a composite complexing agent and a compatible additive, wherein the composite complexing agent comprises a phenanthroline compound and ethylenediaminetetraacetic acid.

[0047] The inventors discovered that there is a synergistic effect between the phenanthroline compound and ethylenediaminetetraacetic acid in the composite complexing agent. Compared with using ethylenediaminetetraacetic acid alone or a phenanthroline compound alone as a complexing agent, the composite complexing agent can better complex rare earth elements, improve the element retention rate of rare earth elements in low-concentration solutions, and at the same time enhance the oil-water amphiphilicity of the tracer, making it more suitable for shale formations and significantly reducing the adsorption of the tracer by the shale formation.

[0048] The inventors also discovered that there is a synergistic effect between the compatibility additive and the composite complexing agent in the tracer, which can enhance the solubility of rare earth element compounds in the fracturing fluid and play a buffering, protective and stabilizing role when the tracer contacts the fracturing fluid, thereby preventing the anionic and cationic drag reducers in the fracturing fluid from reacting extensively with the tracer and causing complexation failure, further improving the element retention rate of rare earth elements in low-concentration solutions, and at the same time improving the high-temperature performance of the tracer, and enabling the tracer to have the function of enhancing the sand-carrying capacity of the fracturing fluid.

[0049] According to the present invention, the mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive is 1:(0.5-1):(0.01-0.1), for example, 1:0.5:0.01, 1:0.8:0.01, 1:0.9:0.1, 1:0.9:0.03, 1:1:0.01, 1:1:0.05; and / or

[0050] The mass ratio of the ethylenediaminetetraacetic acid to the phenanthroline compound is 1:(0.01-0.5), for example, 1:0.01, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5.

[0051] According to the present invention, on the basis of satisfying the above-mentioned quantitative relationship, in order to enable the tracer to obtain better rare earth element retention rate, compatibility with fracturing fluid, high temperature stability and improved comprehensive performance of sand carrying capacity of fracturing fluid, the components of the tracer preferably have a mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive of 1:(0.8-1):(0.01-0.05), for example, 1:0.8:0.01, 1:0.9:0.03, 1:1:0.01, 1:1:0.05.

[0052] According to the present invention, the phenanthroline compound has a structure as shown in Formula I:

[0053] wherein R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, halogen, CN, NO2, C1-C8 alkyl, halogenated C1-C8 alkyl, C1-C8 alkoxy, halogenated C1-C8 alkoxy, C1-C8 alkylthio, halogenated C1-C8 alkylthio, C1-C8 alkylsulfinyl, halogenated C1-C8 alkylsulfinyl, C1-C8 alkylsulfonyl, halogenated C1-C8 alkylsulfonyl, aryl, halogenated sulfoaryl, carboxyl, C1-C8 alkylcarboxyl, halogenated C1-C8 alkylcarboxyl, C1-C8 alkyl-substituted C1-C8 alkylcarboxyl-substituted amino.

[0054] According to a preferred embodiment of the present invention, in Formula I, R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, phenyl, chlorosulfonylphenyl, carboxyl and -CH2N(CH2COOH)2.

[0055] According to a further preferred embodiment of the present invention, the phenanthroline compound is selected from at least one of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline), 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline and 4,7-dichlorosulfonylbenzene-2,9-dicarboxylic acid-1,10-phenanthroline, which can better cooperate with ethylenediaminetetraacetic acid, and better cooperate between the composite complexing agent and the compatible additive, thereby bringing better rare earth element complexation, thereby making the tracer have better rare earth element retention rate, compatibility with fracturing fluid, high temperature performance and improved sand carrying capacity of the fracturing fluid.

[0056] According to the present invention, the rare earth element in the rare earth element compound is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0057] According to the present invention, the rare earth element compound is a soluble salt of the rare earth element, preferably at least one of nitrate, chloride and sulfate.

[0058] According to the present invention, the compatibility additive is selected from at least one of gum arabic, xanthan gum, natural rubber, casein, casein, casein and sodium alginate. Preferably, the compatibility additive is gum arabic and / or sodium alginate.

[0059] Application of the tracer according to the present invention in shale oil and gas exploration and development.

[0060] In the present invention, when the tracer provided contains the above-mentioned specific contents of rare earth element compounds, composite complexing agents, and compatibility additives, and adopts a specific composite complexing agent composition and specific types of compatibility additives, a synergistic effect can be generated between the phenanthroline compound and ethylenediaminetetraacetic acid in the composite complexing agent, and a synergistic effect can also be generated between the composite complexing agent and the compatibility additive; this dual synergistic effect enables the tracer to have low adsorption in shale environments, good compatibility with water-based fracturing fluids, good high-temperature performance, and the ability to improve the sand-carrying capacity of fracturing fluids. Compared with existing tracers, the tracer provided by the present invention has better adaptability to shale oil and gas reservoirs with low porosity, low permeability, high organic matter content, and high clay mineral content, can continuously and effectively perform monitoring functions, and meet the requirements of shale oil and gas exploration and development technology. When it is outside the above-mentioned limited range, the obtained tracer cannot have the comprehensive performance of the tracer provided by the present invention in terms of rare earth element retention rate, compatibility with fracturing fluids, high-temperature performance, and improved sand-carrying capacity of fracturing fluids.

[0061] According to the present invention, the tracer can be prepared by the following method:

[0062] The tracer is prepared by mixing the rare earth element compound, the composite complexing agent and the compatibility additive that meet the above-defined quantitative relationship with water until the precipitation completely disappears.

[0063] According to another aspect of the present invention, a device for evaluating the effectiveness of fracturing by using a tracer is also proposed. The tracer is the tracer provided by the present invention, which realizes the integrated implementation of the entire process of fluid tracer preparation, pumping, collection, processing and monitoring, provides effective support for shale oil and gas fracturing effect evaluation and horizontal well deployment decision-making, and provides an original and applicable experimental device for shale oil and gas exploration and development.

[0064] FIG1 schematically shows an apparatus for evaluating the effect of fracturing by using a tracer according to the present invention, comprising:

[0065] The tracer preparation device is used to automatically prepare the tracer. The inlet 105 of the tracer preparation device is connected to an external water supply 101. A silo containing raw materials can be located within the device to automatically prepare the tracer components as needed. The outlet of the tracer preparation device is connected to a pumping device, which injects the prepared tracer into the formation.

[0066] The tracer monitoring device is used to detect tracers in the flowback fluid. The tracer monitoring device is connected to the flowback fluid. The tracer detection device includes a flowback fluid processing device and an analytical instrument for trace element tracers.

[0067] The apparatus for evaluating the effect of fracturing by using a tracer in this embodiment further includes a central control device 127 , which is connected to the tracer preparation device and the tracer monitoring device;

[0068] The central control device 127 controls the tracer preparation device and the tracer monitoring device in real time, and the central control device 127 performs statistics and analysis on the analysis results of the analysis instrument to obtain fracturing implementation effect data.

[0069] The apparatus for evaluating fracturing effectiveness using tracers, as described in this embodiment, integrates tracer preparation, injection, and monitoring, and achieves full automation through the central control unit 127. Fully automated fluid tracer preparation and dynamic monitoring is of great significance for evaluating shale oil and gas development results. It addresses the on-site need for immediate tracer monitoring data, unifies the overall implementation process, improves work efficiency, and provides applicable experimental equipment and scientific experimental data for shale oil and gas fracturing effectiveness evaluation and horizontal well deployment decision-making.

[0070] In one embodiment, the tracer preparation device includes a liquid preparation tank 106, a cylindrical container with an inlet 105 located at the top and an outlet located at the bottom. As shown in Figure 1, the inlet 105 of the liquid preparation tank 106 is located on the upper side, and the outlet is located on the other side at the bottom. The inlet 105 of the liquid preparation tank 106 is connected to an external water supply source 101 via a liquid inlet pipeline. The water supply source 101 provides the liquid preparation tank 106 with the water required for tracer preparation. The liquid outlet is connected to a liquid outlet pipeline, which is then connected to a pumping device.

[0071] Several reagent delivery bins are located above the liquid preparation bin 106. These contain the raw reagents for preparing the tracer. Multiple reagent delivery bins are located on the top cover of the liquid preparation bin 106 and are arranged side by side. The number of reagent delivery bins is selected based on the raw materials required to prepare the tracer.

[0072] A valve is provided at the lower end of the reagent delivery bin, and the valve can be controlled by the central control device 127 to adjust the opening, thereby controlling the speed and amount of injection of the raw material reagent. In this embodiment, the raw material contained in the reagent delivery bin can be a liquid reagent, or a powdered or granular raw material.

[0073] Water from the water supply 101 enters the liquid preparation tank 106 through the liquid inlet pipeline. Simultaneously, the reagent delivery tank delivers reagent into the liquid preparation tank 106. The central control unit 127 controls the amount of water flowing in and the amount of reagent delivered. The delivered reagent mixes with the water in the liquid preparation tank 106 to form a tracer. The prepared tracer flows out of the outlet.

[0074] In a preferred embodiment, the reagent delivery bin is equipped with a real-time weight meter, which is connected to the central control device 127. The central control device 127 adjusts the valve of the actual delivery bin according to the changes of the real-time weight meter, and controls the amount of reagent delivered in combination with the valve.

[0075] In one embodiment, a stirring device 110 is provided inside the liquid preparation bin 106 , a filter screen 111 is provided at the lower portion of the liquid preparation bin 106 , and the stirring device 110 is provided between the reagent delivery bin and the filter screen 111 .

[0076] Preferably, the stirring device 110 includes a vertically arranged rotating shaft and a plurality of blades arranged horizontally on the rotating shaft. The rotation of the rotating shaft drives the blades to rotate, thereby mixing the raw material reagents into the water, and the preparation is completed after filtering.

[0077] The stirring device 110 can be provided to fully mix the water and the reagent. After being fully mixed, the impurities are filtered out through the filter and then discharged.

[0078] Preferably, the filter 111 is a 40-mesh filter 111 to prevent particulate matter in the reagent from passing through.

[0079] In one embodiment, a sewage filtration and purification device is provided on the liquid inlet pipeline of the liquid preparation tank 106. In this embodiment, the external water supply source 101 for preparing the tracer can be recycled water or sewage, which is purified by the sewage filtration and purification device and then used to prepare the tracer, thereby saving costs.

[0080] The sewage filtration and purification device 103 comprises a tank; a pressure regulating valve is installed at the tank inlet 105, and a filter and particle recovery bin are located within the tank. The pressure regulating valve regulates the incoming water pressure, ensuring a stable and appropriate level of pressure. The filter filters particles and other impurities, directing the filtered particles and other impurities into the particle recovery bin. The filter is a 40-mesh filter 111.

[0081] In one embodiment, the pumping device includes a horizontal flow pump 114 disposed on the liquid outlet pipeline. The horizontal flow pump 114 is connected to a sand blender 116, through which the prepared tracer is injected into the wellbore. The sand blender 116 is a key component of oilfield fracturing and sand control operations, primarily used to mix, stir, and transport the sand, fluid, and other media required for fracturing operations. The prepared tracer is injected into the wellbore via the sand blender 116.

[0082] In one embodiment, the analytical instrument includes a portable inductively coupled plasma mass spectrometer 125 ; the inlet 105 of the analytical instrument is connected to a flowback liquid processing device via a flowback liquid pipeline 124 , and the inlet end of the flowback liquid processing device is connected to an external manifold fluid separator 117 .

[0083] The Inductively Coupled Plasma Mass Spectrometer 125 is an analytical instrument used to determine the mass fractions of various elements in a sample. Based on plasma technology, the sample is inductively coupled to a high-frequency electromagnetic field, ionizing the atoms in the sample and generating energy during the ionization process. After ionization, these ions are accelerated and focused in a high-frequency electromagnetic field to form a transient plasma beam. By measuring the velocity and density of the plasma beam, the mass fractions of various elements in the sample can be determined.

[0084] In this embodiment, the inductively coupled plasma mass spectrometer preferably adopts a portable inductively coupled plasma mass spectrometer 125, which can be installed on an instrument vehicle to carry out ICP-MS testing outdoors (here it is used as an analytical instrument for trace element tracers, and other analytical instruments can also be expanded), and then the return fluid data of different periods are statistically processed and analyzed through the central control device 127.

[0085] In one embodiment, the flowback liquid processing device includes a flowback liquid filtration and purification device 119, with a flowback liquid separation and volume control device 121 disposed downstream of the flowback liquid filtration and purification device 119. The flowback liquid filtration and purification device 119 may have the same or different structures as the wastewater filtration and purification device. In this embodiment, the flowback liquid filtration and purification device 119 preferably has a structure that is somewhat different from that of the wastewater filtration and purification device.

[0086] The flowback liquid filtration and purification device 119 comprises a tank body; a pressure regulating valve is installed at the tank inlet 105. Inside the tank body, a filter screen 111, an activated carbon layer, a sponge layer, and a particle recovery bin are installed. The filter screen 111 is a 200-mesh filter screen. The activated carbon layer and sponge layer adsorb impurities. The pressure regulating valve regulates the incoming water pressure to maintain a stable and appropriate level. The filter screen filters particles and other impurities, directing the filtered particles and other impurities into the particle recovery bin.

[0087] In one embodiment, the flowback liquid separation and volume control device 121 is connected to the analytical instrument via a flowback liquid pipeline 124 , and a discharge nozzle 123 is further provided on the flowback liquid separation and volume control device 121 .

[0088] Preferably, a first valve 102 and a second valve 104 are provided on the liquid inlet pipeline, the first valve 102 is provided upstream of the sewage filtration and purification device 103, and the second valve 104 is provided downstream of the sewage filtration and purification device 103, and a flow meter is also provided at the position of the second valve 104 for measuring the water entering the liquid distribution tank 106.

[0089] A third valve 113 and a fourth valve 115 are provided on the liquid outlet pipeline. The third valve 113 is provided upstream of the horizontal flow pump 114, and the fourth valve 115 is provided downstream of the horizontal flow pump 114. A flow meter is provided at the position of the fourth valve 115 to measure the flow rate of the tracer injected into the sand blender 116.

[0090] A fifth valve 118, a sixth valve 120, and a seventh valve 122 are installed on the flowback liquid pipeline 124. The fifth valve 118 is located upstream of the flowback liquid filtration and purification device 119, and the sixth valve 120 is located between the flowback liquid filtration and purification device 119 and the flowback liquid separation and volume control device 121. The seventh valve 122 is located at the discharge port 123. A flowmeter is installed at the location of the fifth valve 118 to measure the flow rate of the flowback liquid.

[0091] The first valve 102 , the second valve 104 , the third valve 113 , the fourth valve 115 , the fifth valve 118 , the sixth valve 120 and the seventh valve 122 are all connected to the central control device 127 , which controls the opening and closing of the valves and adjusts the opening degrees of the valves.

[0092] The central control device 127 is also connected to the reagent delivery bin to control the speed and amount of the reagent delivered by the reagent delivery bin.

[0093] The flow meter is connected to the central control device 127 and feeds back the flow in the pipeline to the central control device 127, thereby facilitating the central control device 127 to adjust each valve.

[0094] In addition, the central control device 127 is also connected to the stirring device 110 to control the stirring speed, and is also connected to the horizontal flow pump 114. The pumping flow rate of the horizontal flow pump 114 can be adjusted to control the pumping rate.

[0095] According to another aspect of the present invention, a method is provided, which is a method for using a device for evaluating the effect of fracturing by using a tracer, comprising:

[0096] Debug the device at the development well site to ensure proper operation of all electronic equipment and sensors, and to ensure proper control of the central control unit 127. Assemble the tracer preparation device and the tracer monitoring device.

[0097] The inlet 105 of the liquid mixing tank 106 is connected to the water supply source 101, the outlet is connected to the sand blender 116, the tracer monitoring device is connected to the tracer monitoring target well manifold fluid separator 117, and the return liquid separation and constant volume device 121 is connected to the return liquid discharge nozzle 123.

[0098] Prepare tracer preparation reagents A, B, and C in the reagent delivery chamber and place them inside the three reagent delivery chambers.

[0099] Open the first valve 102 and the second valve 104. The central control device 127 monitors the flow rate at the second valve 104 and controls the dosage of reagents A, B, and C. The stirring device 110 is activated to complete the preparation of the tracer. The first and second valves 102 and 104 are then closed. The third and fourth valves 113 and 115 are opened. The tracer is then uniformly dispensed into the sand blender 116 via the central control device 127. After the dosage is complete, the third and fourth valves 113 and 115 are closed.

[0100] Clean the sediment at the filter screen of the sewage filtering and purification device 103, and clean the sediment and insoluble matter at the filter screen 111 in the liquid mixing tank 106.

[0101] After the fracturing operation is completed, when the tracer monitoring target well is opened, the fifth valve 118 and the sixth valve 120 are opened, and the pressure regulating valve of the return fluid filtration and purification device 119 is adjusted by the central control device 127 until the tank is filled with return fluid, and the fifth valve 118 is closed.

[0102] After the return liquid in the return liquid filtration and purification device 119 is filtered and purified, the sixth valve 120 is opened to receive the return liquid into the return liquid separation and constant volume device 121. The return liquid collected by the oil-water separator enters the constant volume pipe and is constant volume to 10 ml of liquid.

[0103] Close the sixth valve 120, open the seventh valve 122 to discharge the remaining flowback liquid from the discharge port 123, and then close the seventh valve 122.

[0104] The return liquid in the constant volume tube is extracted by an automatic sampler and sent to the inductively coupled plasma mass spectrometer 125 for ICP-MS analysis, and the analysis results are transmitted to the central control device 127.

[0105] The central control device 127 is used to collect statistics and analyze the analysis results to evaluate the effect of the fracturing implementation.

[0106] After the analysis is completed, shut down all equipment and clean up the sediment and impurities in the return liquid filtration and purification device.

[0107] The method described in this embodiment enables an integrated approach to the preparation, injection, collection, processing, and monitoring of fluid tracers at shale oil and gas well development sites. This meets the on-site demand for timely tracer monitoring data, unifies the overall workflow of tracer monitoring technology, improves efficiency, and significantly enhances the comparability of tracer monitoring data and results for different target wells and target intervals. This provides a practical experimental device and scientific experimental data for evaluating shale oil and gas fracturing effectiveness and making decisions about horizontal well deployment.

[0108] According to the present invention, preferably, the application includes: using the tracer described in the first aspect above to: determine the connectivity relationship between the shale gas development well and the adjacent wells, calculate the fracturing fluid return rate of the tracer injection section, and determine the migration direction of the fracturing fluid in the formation and calculate the migration rate.

[0109] According to the present invention, in the application, by understanding the connectivity relationship between the development well and the adjacent production wells during the fracturing process, the effect of the fracturing construction can be effectively evaluated (generally, connectivity will lead to poor fracturing effect). Furthermore, the rationality of the well spacing setting can be evaluated (for example, if it is determined to be connected, it is necessary to consider increasing the spacing setting of other wells in the area to avoid connectivity between other wells), which is beneficial to the optimization of the development plan.

[0110] According to the present invention, in the application described above, calculating the flowback rate of a single fracturing stage can be used to determine the fracturing effect (it is generally believed that a fracturing stage with a high flowback rate corresponds to a poor fracturing effect). In addition, the flowback rate can be used to calculate the water production of a single fracturing stage, estimate the gas production, and the remaining recoverable volume. These parameters help to more rationally regulate the later stages of shale gas production and development cycle.

[0111] According to the present invention, in the application described above, by determining the migration direction of the fracturing fluid in the formation and calculating the migration rate, it is possible to obtain information about the migration of the fracturing fluid in the formation. This provides key evidence for the high flowback characteristics of nearby development wells during production (the characteristic of well flowback volume exceeding the fracturing fluid volume during shale gas production), confirming whether the high flowback rate is caused by fracturing fluid migration. In addition, it also has certain guiding significance for correctly understanding the effects of formation stress and the migration patterns of formation fluids.

[0112] According to the present invention, in the application, the actual usage of the tracer is determined by detecting the concentration of rare earth elements in the initial flowback fluid of the formation and combining the concentration of rare earth elements in the initial flowback fluid of the formation and the amount of fracturing fluid in the shale gas development well.

[0113] Preferably, the concentration of rare earth elements in the initial flowback fluid from the formation is detected by an inductively coupled plasma mass spectrometer.

[0114] The use of the tracer provided by the present invention in shale oil and gas exploration and development can more continuously and effectively monitor the connectivity between layers or horizontal sections in real time, quantitatively analyze the return rate of single-stage fracturing fluid, determine the migration direction of fracturing fluid in the formation and calculate the migration rate. It can be well used to qualitatively evaluate the implementation effect of horizontal well fracturing and optimize the fracturing construction deployment in the target area.

[0115] The present invention will be described in detail below through examples. In the following examples and comparative examples, unless otherwise specified, all materials used are common commercially available products.

[0116] Complex complexing agents and tracers

[0117] Example 1

[0118] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.3;

[0119] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (gum arabic), and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S1);

[0120] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.03.

[0121] Comparative Example 1

[0122] The composite complexing agent provided in this comparative example is the same as that in Example 1;

[0123] The tracer provided in this comparative example follows the method of Example 1, except that no compatibility additive is used. Other conditions are the same as in Example 1. Specifically, a certain amount of a complexing agent and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate disappears, yielding a uniform, transparent tracer solution (denoted as D1).

[0124] Wherein, the weight ratio of the rare earth element compound to the complexing agent is 1:0.9.

[0125] Comparative Example 2

[0126] The tracer provided in this comparative example follows the method of Example 1, except that no complexing agent is used. Other conditions are the same as those of Example 1. Specifically, a certain amount of a compatibility additive (gum arabic) and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate is not completely dissolved, thereby obtaining a tracer solution (denoted as D2).

[0127] The weight ratio of the rare earth element compound to the compatible additive is 1:0.03.

[0128] Comparative Example 3

[0129] The complexing agent provided in this comparative example is as follows: the ethylenediaminetetraacetic acid in the composite complexing agent provided in Example 1 is replaced by an equal weight of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline);

[0130] The tracer provided in this comparative example was: the composite complexing agent in Example 1 was replaced with the complexing agent provided in this comparative example. Other conditions were the same as those in Example 1. A uniform and transparent tracer solution (denoted as D3) was obtained.

[0131] Comparative Example 4

[0132] The composite complexing agent provided in this comparative example is as follows: the ethylenediaminetetraacetic acid in the composite complexing agent provided in Example 1 is replaced by an equal weight of dipyridinecarboxylic acid;

[0133] The tracer provided in this comparative example was: the composite complexing agent in Example 1 was replaced with the composite complexing agent provided in this comparative example. Other conditions were the same as those in Example 1. A uniform and transparent tracer solution (denoted as D4) was obtained.

[0134] Comparative Example 5

[0135] The complexing agent provided in this comparative example is as follows: 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in the composite complexing agent provided in Example 1 is replaced with an equal weight of ethylenediaminetetraacetic acid;

[0136] The tracer provided in this comparative example was: the composite complexing agent in Example 1 was replaced with the complexing agent provided in this comparative example. Other conditions were the same as those in Example 1. A uniform and transparent tracer solution (denoted as D5) was obtained.

[0137] Comparative Example 6

[0138] The composite complexing agent provided in this comparative example is the same as that in Example 1;

[0139] The tracer provided in this comparative example follows the method of Example 1, except that the ratio of the complexing agent is changed. Other conditions remain the same as in Example 1. Specifically, a certain amount of the complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (gum arabic), and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as D6).

[0140] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.1:0.03.

[0141] Comparative Example 7

[0142] The composite complexing agent provided in this comparative example is the same as that in Example 1;

[0143] The tracer provided in this comparative example follows the method of Example 1, except that the ratio of the compatibility additives is changed. Other conditions are the same as those in Example 1. Specifically, a certain amount of complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, obtaining a uniform, transparent tracer solution (denoted as D7).

[0144] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.005.

[0145] Comparative Example 8

[0146] The tracer provided in this comparative example follows the method of Example 1, except that no complexing agent or compatibility additive is added. All other conditions are the same as in Example 1. Specifically, a certain amount of a rare earth element compound (praseodymium nitrate) is weighed and slowly added to water with uniform stirring until the precipitate disappears, yielding a homogeneous, transparent tracer solution (denoted as D8).

[0147] The concentration of the rare earth element (calculated by weight of the rare earth element) in the tracer is the same as that in Example 1.

[0148] Comparative Example 9

[0149] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.6;

[0150] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as D9);

[0151] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.03.

[0152] Comparative Example 10

[0153] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.001;

[0154] The tracer provided in this example was prepared by slowly adding a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (praseodymium nitrate) to water and stirring until the precipitate completely disappeared, thereby obtaining a uniform and transparent tracer solution (denoted as D10).

[0155] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.03.

[0156] Example 2

[0157] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.2;

[0158] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (ytterbium nitrate) are slowly added to water and stirred until the precipitate disappears completely, thereby obtaining a uniform and transparent tracer solution (denoted as S2);

[0159] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:1:0.01.

[0160] Example 3

[0161] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 4,7-dichlorosulfonylbenzene-2,9-dicarboxylic acid-1,10-phenanthroline at a weight ratio of 1:0.3;

[0162] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 4,7-dichlorosulfonylbenzene-2,9-dicarboxylic acid-1,10-phenanthroline), a compatible additive (sodium alginate), and a rare earth element compound (samarium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S3);

[0163] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:1:0.05.

[0164] Example 4

[0165] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0166] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (yttrium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S4);

[0167] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.5:0.01.

[0168] Example 5

[0169] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0170] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (casein), and a rare earth element compound (lanthanum nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S5);

[0171] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.5:0.01.

[0172] Example 6

[0173] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0174] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (natural rubber), and a rare earth element compound (cerium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S6);

[0175] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.5:0.01.

[0176] Example 7

[0177] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0178] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (sodium alginate), and a rare earth element compound (neodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S7);

[0179] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.5:0.01.

[0180] Example 8

[0181] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0182] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (terbium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S8);

[0183] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.8:0.01.

[0184] Example 9

[0185] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0186] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (xanthan gum), and a rare earth element compound (erbium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S9);

[0187] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.8:0.01.

[0188] Example 10

[0189] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1;

[0190] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatible additive (casein), and a rare earth element compound (lutetium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S10);

[0191] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.8:0.01.

[0192] Example 11

[0193] The composite complexing agent provided in this embodiment is the same as the composite complexing agent in Example 10 except that 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) is replaced by 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline;

[0194] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline), a compatible additive (casein), and a rare earth element compound (lutetium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S11);

[0195] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.8:0.01.

[0196] Example 12

[0197] The composite complexing agent provided in this embodiment is obtained by mixing ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline at a weight ratio of 1:0.01;

[0198] The tracer provided in this embodiment: The method of Example 11 is followed, except that the composite complexing agent is the composite complexing agent provided in this embodiment, and other conditions are the same as those in Example 11. A uniform and transparent tracer solution (denoted as S12) is obtained;

[0199] The weight ratio of the rare earth element compound: the complexing agent: the compatible additive is 1:0.8:0.01.

[0200] Example 13

[0201] The composite complexing agent provided in this embodiment is the same as that in Example 1;

[0202] The tracer provided in this embodiment follows the method of Example 1, except that gum arabic is replaced with an equal weight of casein. Other conditions are the same as those of Example 1. A uniform and transparent tracer solution (denoted as S13) is obtained.

[0203] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.03.

[0204] Example 14

[0205] The composite complexing agent provided in this embodiment is the same as that in Example 1;

[0206] The tracer provided in this example is as follows: a certain amount of a complexing agent (ethylenediaminetetraacetic acid, 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline)), a compatibility additive (gum arabic), and a rare earth element compound (praseodymium nitrate) are slowly added to water and stirred until the precipitate completely disappears, thereby obtaining a uniform and transparent tracer solution (denoted as S14);

[0207] The weight ratio of the rare earth element compound: the composite complexing agent: the compatible additive is 1:0.9:0.1.

[0208] The following describes in detail the technical effect of the tracer provided by the present invention in improving the retention rate of rare earth elements through Test Examples 1 and 2; it should be noted that the "contributed rare earth element retention rate" referred to in Test Examples 1 and 2 specifically refers to "the amount of rare earth element retention rate increased after adding phenanthroline compounds and / or ethylenediaminetetraacetic acid to the tracers S1, tracer D3, and tracer D5 provided in Example 1, Comparative Example 3, and Comparative Example 5, compared with the rare earth element retention rate of the tracer D2 provided in Comparative Example 2 in the fracturing fluid A" or "the amount of rare earth element retention rate increased after adding the composite complexing agent and / or compatible additive to the tracers S1, tracer D1, and tracer D2 provided in Example 1, Comparative Example 1, and Comparative Example 2, compared with the rare earth element retention rate of the tracer D8 provided in Comparative Example 8 in the fracturing fluid A".

[0209] Test Example 1 - Element Retention Test of Tracer in Shale-Containing Fracturing Fluid

[0210] iPrepare fracturing fluid A:

[0211] Fracturing fluid A was prepared according to the formula: "98% water + 1% potassium chloride + 0.5% dilute hydrochloric acid + 0.5% carboxymethyl cellulose", wherein the content of each component is based on the total weight of fracturing fluid A;

[0212] ii. The tracers S1-S14 and D1-D10 prepared in Examples 1 to 14 and Comparative Examples 1 to 10 were respectively added to the fracturing fluid A so that the concentration of rare earth elements (based on the weight of the rare earth elements) in the fracturing fluid A was 1 mg / L. Then, shale powder was added (the amount of shale powder added was 20% by weight of the fracturing fluid A, and the shale powder was black shale powder collected from the Longmaxi Formation in the Qijiang area of ​​the Sichuan Basin, with a particle size of 50-100 mesh). After stirring for 24 hours, the element retention rate was tested using an inductively coupled plasma mass spectrometer at room temperature and pressure. The results are shown in Table 1.

[0213] Table 1. Element retention rates of tracers S1-S14 and D1-D10

[0214] As can be seen from Table 1, the tracers S1-S14 provided by the present invention have the advantage of low adsorption in a shale environment. Specifically, when used at room temperature in a fracturing fluid with a shale content of 20% by weight, the rare earth element retention rates are all above 70%, with the highest reaching 92.5%, which are all higher than those of tracers D1-D10. Therefore, they are more suitable for shale formations. The higher rare earth element retention rate enables the tracer to perform a more sustained and effective monitoring function.

[0215] Furthermore, by analyzing the rare earth element retention rates of tracers S1, D2, D3 and D5 in combination with the formula of the four tracers, it can be seen that: compared with tracer D2, tracer D3 adds 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) as a single-component complexing agent, tracer D5 adds ethylenediaminetetraacetic acid as a single-component complexing agent, and tracer S1 adds 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) and ethylenediaminetetraacetic acid as a composite complexing agent. In terms of rare earth element retention rate, compared with tracer D2, the rare earth element retention rate contributed by the single-component complexing agent in D3 was 15.6%, the rare earth element retention rate contributed by the single-component complexing agent in tracer D5 was 10.4%, and the rare earth element retention rate contributed by the composite complexing agent in tracer S1 was 45.3%, which was higher than the sum of the rare earth retention rates contributed by the two single-component complexing agents in tracers D3 and D5. It can be seen that there is a synergistic effect between the phenanthroline compounds and ethylenediaminetetraacetic acid in the composite complexing agent, which can achieve a better complexing effect on rare earth elements and improve the rare earth element retention rate.

[0216] Furthermore, by combining the formula analysis of tracer S1 and tracers D1, D2 and D8, it can be seen that: compared with tracer D8, tracer D1 adds a composite complexing agent, tracer D2 adds a compatible additive, and tracer S1 adds a composite complexing agent of medium mass to tracer D1 and a compatible additive of medium mass to tracer D2. The performance is as follows: compared with tracer D8, the rare earth element retention rate contributed by the composite complexing agent in tracer D1 is 22.6%, the rare earth element retention rate contributed by the compatible additive in tracer D2 is 4.6%, and the rare earth element retention rate of the composite complexing agent and the compatible additive used simultaneously in tracer S1 is 49.9%, which is higher than the sum of the rare earth element retention rates contributed by the composite complexing agent in tracer D1 and the compatible additive in tracer D2, proving that in the fracturing fluid A with shale powder added, there is an obvious synergistic effect between the composite complexing agent and the compatible additive.

[0217] Tracer D4 uses raw materials outside the scope of the present invention, and the mass ratio of the rare earth element compound, the composite complexing agent, and the compatible additive in tracers D6, D7, D9, and D10, or the mass ratio of ethylenediaminetetraacetic acid and the phenanthroline compound in the composite complexing agent, is outside the scope of the present invention. As a result, at room temperature and pressure, the rare earth element retention rates of tracers D4, D6, D7, D9, and D10 in fracturing fluid A added with shale powder are significantly lower than those of tracer S1, and their complexing and protection capabilities for rare earth elements are poor.

[0218] Test Example 2 - Element Retention Test of Tracer in Fracturing Fluid at Different Temperatures

[0219] i. Preparation of fracturing fluid A: same as test example 1;

[0220] ii. The tracers S1-S14 and D1-D10 prepared in Examples 1 to 14 and Comparative Examples 1 to 10 were respectively added to the fracturing fluid A so that the concentration of the rare earth element (based on the weight of the rare earth element) in the fracturing fluid A was 1 mg / L;

[0221] iii. The temperature of the fracturing fluid with tracer added was controlled by a water bath device to maintain the temperatures at 25°C, 60°C, and 95°C, respectively. After stirring evenly for 24 h, the element retention rate was tested using an inductively coupled plasma mass spectrometer. The results are shown in Table 2.

[0222] Table 2. Element retention rates of tracers S1-S14 and D1-D10 at different temperatures

[0223] As shown in Table 2, the rare earth element retention rate of each tracer in the fracturing fluid decreases to varying degrees with increasing temperature. At 25°C, 60°C, and 95°C, the rare earth element retention rates of tracers S1-S14 provided by the present invention are all higher than those of tracers D1-D10. At 95°C, the rare earth element retention rates of tracers S1-S14 provided by the present invention remain above 65%, reaching a maximum of 92.8%, demonstrating excellent performance and thermal stability at high temperatures. Comparing the performance of S1 with that of S13 and S14 reveals that the selection and proportion of the compatibility additives significantly influence the tracer's performance and thermal stability at high temperatures.

[0224] The following analysis combines the formulas of tracer S1, tracer D1, D2, D3, D5, and D8 and the rare earth retention rate data in Table 2 to analyze the synergistic effect between phenanthroline compounds and ethylenediaminetetraacetic acid in the composite complexing agent at different temperatures and the synergistic effect between the composite complexing agent and the compatible additives.

[0225] On the one hand, compared with tracer D2, tracer D3 with the addition of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) as a single-component complexing agent, tracer D5 with the addition of ethylenediaminetetraacetic acid as a single-component complexing agent, and tracer S1 with the addition of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) and ethylenediaminetetraacetic acid as a composite complexing agent, showed similar results to tracer D2 at 25°C without the addition of shale powder. Compared with the single-component complexing agent in D3, the rare earth element retention rate contributed by the single-component complexing agent in tracer D5 was 15.6%, the rare earth element retention rate contributed by the single-component complexing agent in tracer S1 was 11.3%, and the rare earth element retention rate contributed by the composite complexing agent was 47.6%. The rare earth element retention rate contributed by the composite complexing agent was 20.7% higher than the sum of the rare earth element retention rates contributed by the two single-component complexing agents. Under the condition of 60℃ and without adding shale powder, compared with tracer D2, the rare earth element retention rate contributed by the single-component complexing agent in D3 was 16.7%, the rare earth element retention rate contributed by the composite complexing agent was 47.6%, and the rare earth element retention rate contributed by the composite complexing agent was 47.6%. The rare earth element retention rate contributed by the single-component complexing agent in tracer D5 was 11.6%, and the rare earth element retention rate contributed by the composite complexing agent in tracer S1 was 48.9%. The rare earth element retention rate contributed by the composite complexing agent was 20.6% higher than the sum of the rare earth element retention rates contributed by the two single-component complexing agents. Under the conditions of 95℃ and without adding shale powder, compared with tracer D2, the rare earth element retention rate contributed by the single-component complexing agent in D3 was 17.1%, the rare earth element retention rate contributed by the single-component complexing agent in tracer D5 was 13.2%, and the rare earth element retention rate contributed by the composite complexing agent was 20.6% higher than the sum of the rare earth element retention rates contributed by the two single-component complexing agents. The rare earth retention rate contributed by the composite complexing agent in agent S1 is 52.6%, which is 22.3% higher than the sum of the rare earth element retention rates contributed by the two single-component complexing agents. It can be seen that there is a synergistic effect between the phenanthroline compounds and ethylenediaminetetraacetic acid in the composite complexing agent, and this synergistic effect between the two has good high-temperature stability, is less affected by temperature, and will not weaken with increasing temperature. It can achieve a better complexing effect on rare earth elements at room temperature to 95°C, so that the rare earth element retention rate is maintained at a high level.

[0226] On the other hand, compared with tracer D8, tracer D1 added a complex complexing agent, tracer D2 added a compatibility additive, and tracer S1 added a complex complexing agent of medium mass to tracer D1 and a compatibility additive of medium mass to tracer D2. At 25°C and without adding shale powder, compared with tracer D8, the rare earth element retention rate contributed by the complex complexing agent in tracer D1 was 19.3%, and the rare earth element retention rate contributed by the compatibility additive in tracer D2 was 9.8%. -0.4%, the rare earth element retention rate contributed by the composite complexing agent and the compatibility additive used in tracer S1 was 47.2%, and the rare earth element retention rate contributed by the composite complexing agent and the compatibility additive in tracer S1 was increased by 28.3% compared with the sum of the rare earth element retention rates contributed by the composite complexing agent and the compatibility additive alone; at 60℃ and without adding shale powder, the rare earth element retention rate contributed by the composite complexing agent in tracer D1 was 10 .6%, the rare earth element retention rate contributed by the compatibility additives in tracer D2 was 1.5%, and the rare earth element retention rate contributed by the composite complexing agent and the compatibility additives used simultaneously in tracer S1 was 50.4%. The rare earth element retention rate contributed by the composite complexing agent and the compatibility additives in tracer S1 increased by 38.3% compared with the sum of the rare earth element retention rates contributed by the single composite complexing agent and the single compatibility additive; under the conditions of 95℃ and without adding shale powder, compared with tracer D8, the rare earth element retention rate contributed by the composite complexing agent in tracer D1 was 5.2%, the rare earth element retention rate contributed by the compatibility additives in tracer D2 was 2.9%, and the rare earth element retention rate contributed by the composite complexing agent and the compatibility additives used simultaneously in tracer S1 was 55.5%. The rare earth element retention rate contributed by the composite complexing agent and the compatibility additives in tracer S1 increased by 47.4% compared with the sum of the rare earth element retention rates contributed by the single composite complexing agent and the single compatibility additive. From the above analysis, it can be seen that there is a synergistic effect between the composite complexing agent and the compatible additive, and they have good high-temperature stability. This synergistic effect between the two will increase with the increase of temperature.

[0227] In addition, tracer D4 uses raw materials outside the scope of the present invention, and the mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive in tracers D6, D7, D9, and D10, or the mass ratio of ethylenediaminetetraacetic acid and the phenanthroline compound in the composite complexing agent, is outside the scope of the present invention. As a result, at temperatures of 25 to 95°C, the rare earth element retention rates of tracers D4, D6, D7, D9, and D10 in fracturing fluid A are significantly lower than those of tracer S1, resulting in poor high-temperature stability and poor complexing and protection capabilities for rare earth elements.

[0228] The following describes in detail the technical effects of the tracer provided by the present invention on maintaining the viscosity of the fracturing fluid A and improving the sand carrying performance through test examples 3 and 4.

[0229] Test Example 3 - Effect of Tracer on Viscosity of Fracturing Fluid

[0230] i. Preparation of fracturing fluid A: same as test example 1;

[0231] ii. The tracers S1-S14 and D1-D10 prepared in Examples 1 to 14 and Comparative Examples 1 to 10 were respectively added to the fracturing fluid A so that the concentration of the rare earth element (based on the weight of the rare earth element) in the fracturing fluid A was 1 mg / L;

[0232] iii. Under normal temperature and pressure conditions, the viscosity of the fracturing fluid with added tracer was tested using a viscometer at a shear rate of 75 r / min. The results are shown in Table 3.

[0233] Table 3. Viscosity of Fracturing Fluid A and Fracturing Fluid A with Added Tracer

[0234] As shown in Table 3, compared to fracturing fluid A without tracer addition, the viscosity maintenance rate of fracturing fluid A after adding tracers S1-S14 was above 83%, and the viscosity even occasionally increased. This indicates that the tracers S1-S14 provided by the present invention have a very limited effect on the viscosity reduction of water-based fracturing fluids, demonstrating their excellent compatibility with water-based fracturing fluids.

[0235] Test Example 4 - Effect of Tracer on Sand Carrying Performance of Fracturing Fluid

[0236] i. Preparation of fracturing fluid A: same as test example 1;

[0237] ii. The tracers S1-S14 and D1-D10 prepared in Examples 1 to 14 and Comparative Examples 1 to 10 were respectively added to the fracturing fluid A so that the concentration of the rare earth element (based on the weight of the rare earth element) in the fracturing fluid A was 1 mg / L. Then, a proppant (specifically, quartz sand particles with a particle size of 50 mesh) was added and stirred uniformly so that the content of the proppant in the fracturing fluid A was 0.5 g / mL;

[0238] iii. The proppant particle settling rate was tested under normal temperature and pressure conditions. Specifically, the time it took for most of the proppant particles in Test Example ii to settle to the bottom of the tracer-added fracturing fluid A was recorded. Combined with the liquid level height of the tracer-added fracturing fluid A, the settling rate of the proppant particles in the fracturing fluid A was calculated. The lower the settling rate of the proppant particles, the better the sand-carrying performance of the fracturing fluid. The results are shown in Table 4.

[0239] Table 4. Settling rate of proppant in fracturing fluid A with added tracer

[0240] As shown in Table 4, the addition of tracers S1-S14 to the present invention reduced proppant settling rates by 28% to 52% compared to the proppant settling rate in fracturing fluid A alone, significantly improving the sand-carrying capacity of the water-based drilling fluid. Furthermore, a comparison of the effects of tracer S1 with tracers S13 and S14 demonstrates that the selection and ratio of the tracer additives influences the sand-carrying capacity of the fracturing fluid.

[0241] Based on the results of the above test examples, the tracers provided by the present invention exhibit synergistic effects between the phenanthroline compound and EDTA in the composite complexing agent, as well as between the composite complexing agent and the compatibility additive. This dual synergistic effect gives the tracers provided by the present invention the comprehensive performance advantages of low adsorption in shale environments, good high-temperature performance, good compatibility with water-based fracturing fluids, and enhanced sand-carrying capacity of fracturing fluids. These tracers can continuously and effectively monitor shale formations characterized by low porosity and low permeability, as well as the complexity and specificity of fracturing fluid composition, thus meeting the current requirements of shale oil and gas exploration and development technologies. Tracers outside the scope of the present invention, however, cannot achieve the comprehensive performance of the tracers provided by the present invention in terms of rare earth element retention, compatibility with fracturing fluids, high-temperature performance, and enhanced sand-carrying capacity, and therefore cannot meet the current requirements of shale oil and gas exploration and development technologies.

[0242] To further illustrate the practical application of the tracer provided by the present invention in shale oil and gas exploration and development, a field application example of the tracer is provided herein for the purpose of determining the connectivity between a shale oil and gas development well and an adjacent well, and calculating the flowback rate of the fracturing fluid in the tracer injection section.

[0243] Example 15

[0244] Well 10-1HF in a shale gas field was used as the tracer injection well, and Well 10HF was used as the monitoring well. The horizontal sections of the two wells were arranged in parallel with a spacing of about 300 meters (see Figure 2). By integrating the results of lost circulation locations, dipole acoustic logging interpretation of well sections with developed bedding fractures, and seismic curvature prediction of well sections with abnormal development, fracturing sections (sections 14, 19, 21, and 22) corresponding to areas with poor cementing quality and developed fractures in the formation were selected from the full-well fracturing sections as tracer injection sections. The concentrations of rare earth elements in the initial flowback fluid from Well 10HF were then measured using inductively coupled plasma mass spectrometry. The actual amounts of rare earth element compounds, composite complexing agents, and compatibility additives used were calculated based on the concentrations of rare earth elements in the initial flowback fluid and the fracturing fluid volume of shale gas development wells, as shown in Table 5. The composite complexing agent was a mixture of ethylenediaminetetraacetic acid and 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline) in a weight ratio of 1:0.1, and the compatibility additive was gum arabic.

[0245] Table 5. Practical application of tracers in a shale gas field

[0246] The tracer was prepared as an aqueous solution before fracturing the shale gas development wells. During the fracturing pre-flush phase of Well 10-1HF, the prepared tracer was pumped in at a constant rate of 20 L / min. Following tracer placement, flowback fluids were collected immediately upon drilling in Wells 10-1HF and 10HF, and continuous rare earth element concentration monitoring was performed using an inductively coupled plasma mass spectrometer. The specific results are as follows:

[0247] (1) The concentration of rare earth elements in the return fluid of the 10-1HF well was monitored for 55 days. As shown in Figure 3, the concentrations of the four rare earth elements Ce, La, Yb, and Sm in the original formation were 0.45 ng / g, 0.25 ng / g, 0.02 ng / g, and 0.05 ng / g, respectively. The concentrations of the four rare earth elements increased significantly when the well was first opened, and slowly decreased during the monitoring process. The final concentrations of the four rare earth elements in the return fluid were 0.10 ng / g, 0.32 ng / g, 0.41 ng / g, and 0.06 ng / g, respectively. Since the instrument monitoring accuracy is approximately 0.01-0.1 ng / g, it is believed that the return fluid is basically consistent with the initial formation fluid element concentration, which indicates that the tracer fluid in the horizontal section of the 10-1HF well is basically completely discharged.

[0248] (2) The concentrations of rare earth elements in the flowback fluid of Well 10HF were monitored for 67 days. As shown in Figure 4, the concentrations of the four rare earth elements Ce, La, Yb, and Sm in the original formation were 0.27 ng / g, 2.16 ng / g, 0.12 ng / g, and 0.91 ng / g, respectively. The concentration of Yb increased significantly when the well was first opened, then decreased steadily and slowly, while the concentrations of the other three elements remained basically unchanged. The final concentrations of the four rare earth elements in the flowback fluid were 0.06 ng / g, 0.44 ng / g, 10.31 ng / g, and 0.14 ng / g, respectively. This indicates that the horizontal section of Well 10-1HF was continuously connected to Well 10HF at Section 21.

[0249] The above field application examples show that the tracer provided by the present invention has good applicability and effectiveness in actual field applications in shale oil and gas exploration and development.

[0250] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should extend to equivalent substitutions of these features understood by those skilled in the relevant art. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0251] In the description of the present invention, unless otherwise specified, "plurality" means two or more; terms such as "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," and "tail" indicate positions or relationships based on those shown in the accompanying drawings. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, terms such as "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0252] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integral connection; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediary. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0253] Certain terms are used throughout this specification to refer to specific system components. As those skilled in the art will appreciate, different names can often be used to refer to the same component, and thus this specification does not intend to distinguish between components that differ only in name, not function. References in this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "an embodiment" appearing in various places throughout this specification do not necessarily refer to the same embodiment.

[0254] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

[0255] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and / or modifications that fall within the scope of the present invention, and changes and / or modifications made in accordance with the embodiments of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A tracer comprising a rare earth element compound, a complexing agent and a compatible additive, wherein: The composite complexing agent comprises a phenanthroline compound and ethylenediaminetetraacetic acid.

2. The tracer according to claim 1, characterized in that The mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive is 1:(0.5-1):(0.01-0.1); and / or The mass ratio of the ethylenediaminetetraacetic acid to the phenanthroline compound is 1:(0.01-0.5).

3. The tracer according to claim 2, characterized in that The mass ratio of the rare earth element compound, the composite complexing agent and the compatible additive is 1:(0.8-1):(0.01-0.05).

4. The tracer according to any one of claims 1 to 3, characterized in that The phenanthroline compound has a structure as shown in Formula I: Wherein, R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, halogen, CN, NO2, C1-C8 alkyl, halogenated C1-C8 alkyl, C1-C8 alkoxy, halogenated C1-C8 alkoxy, C1-C8 alkylthio, halogenated C1-C8 alkylthio, C1-C8 alkylsulfinyl, halogenated C1-C8 alkylsulfinyl, C1-C8 alkylsulfonyl, halogenated C1-C8 alkylsulfonyl, aryl, halogenated sulfoaryl, carboxyl, C1-C8 alkylcarboxyl, halogenated C1-C8 alkylcarboxyl, C1-C8 alkyl substituted C1-C8 alkylcarboxyl substituted amino.

5. The tracer according to claim 4, characterized in that In Formula I, R1, R2, R3, R4, R5, R6, R7 and R8 are each independently selected from H, phenyl, chlorosulfonylphenyl, carboxyl and -CH2N(CH2COOH)2.

6. The tracer according to claim 5, characterized in that The phenanthroline compound is selected from at least one of 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-4,7-(phenyl)-1,10-(phenanthroline), 2,9-bis[N,N-bis(carboxymethyl)aminomethyl]-1,10-phenanthroline and 4,7-dichlorosulfonylbenzene-2,9-dicarboxylic acid-1,10-phenanthroline.

7. The tracer according to claim 6, characterized in that The rare earth element in the rare earth element compound is selected from at least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

8. The tracer according to claim 7, characterized in that The rare earth element compound is a soluble salt of the rare earth element, preferably at least one of a nitrate, a chloride and a sulfate.

9. The tracer according to any one of claims 1 to 8, characterized in that The compatibility additive is selected from at least one of gum arabic, xanthan gum, natural rubber, casein, casein, casein and sodium alginate.

10. Use of the tracer according to any one of claims 1 to 9 in shale oil and gas exploration and development.

11. A device for evaluating the effect of fracturing by using a tracer, characterized in that: The tracer is a tracer according to any one of claims 1 to 9; the device comprises: Tracer preparation device; A pumping device connected to the tracer preparation device to inject the prepared tracer into the formation; a tracer detection device, the tracer detection device comprising a flowback fluid processing device for receiving and processing the flowback fluid and an analysis instrument for detecting and analyzing the tracer in the flowback fluid; and A central control device (127), the central control device (127) is connected to and controls the tracer preparation device, the pumping device and the tracer monitoring device; Wherein, the central control device (127) obtains the fracturing implementation effect data according to the analysis results of the analysis instrument.

12. The device for evaluating the effect of fracturing by using a tracer according to claim 11, characterized in that: The tracer preparation device comprises a liquid preparation bin (106), an inlet (105) of the liquid preparation bin (106) is connected to an external water supply source (101) via a liquid inlet pipeline, and an outlet of the liquid preparation bin (106) is connected to a pumping device via a liquid outlet pipeline; At least one reagent delivery bin is provided on the upper part of the liquid preparation bin (106), and the reagent delivery bin contains raw material reagents for preparing the tracer; A stirring device (110) is arranged inside the liquid preparation bin (106), and the stirring device (110) is arranged below the reagent delivery bin; a filter screen is arranged below the stirring device.

13. The device for evaluating the effect of fracturing by using a tracer according to claim 12, characterized in that: The reagent delivery bin is provided with a weight meter for real-time detection of the weight information of the reagent delivery bin and transmission to the central control device (127); the central control device (127) controls the switch of the reagent delivery bin according to the weight information; The liquid inlet pipeline is provided with a sewage filtering and purifying device, which comprises a tank body, and a pressure regulating valve is provided at the inlet end of the tank body; a filter screen and a particle recovery bin are provided inside the tank body.

14. The device for evaluating the effect of fracturing by using a tracer according to claim 13, characterized in that: The analytical instrument comprises a portable inductively coupled plasma mass spectrometer (125); the inlet (105) of the analytical instrument is connected to the outlet of a return liquid processing device via a return liquid pipeline (124); the inlet end of the return liquid processing device is connected to an external manifold fluid separator (117); The return liquid treatment device comprises a return liquid filtering and purifying device (119), and a return liquid separation and volume fixing device (121) is arranged downstream of the return liquid filtering and purifying device (119); The return liquid separation and volume setting device (121) is connected to the analytical instrument via a return liquid pipeline (124), and a discharge nozzle (123) is also provided on the return liquid separation and volume setting device (121).

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