CN113429959B - Preparation method of trace substance tracing proppant and application of trace substance tracing proppant in fracture monitoring - Google Patents
Preparation method of trace substance tracing proppant and application of trace substance tracing proppant in fracture monitoring Download PDFInfo
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- CN113429959B CN113429959B CN202110889430.3A CN202110889430A CN113429959B CN 113429959 B CN113429959 B CN 113429959B CN 202110889430 A CN202110889430 A CN 202110889430A CN 113429959 B CN113429959 B CN 113429959B
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
- C09K8/805—Coated proppants
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
Abstract
The invention discloses a preparation method of trace substance tracer propping agent and application thereof in crack monitoring, wherein trace substance tracer is embedded on traditional propping agent-quartz sand to obtain a novel trace substance tracer functionalized propping agent, and controllable release of the tracer in practical application is realized, the method for estimating the position of the propping agent by using the tracer flowback curve is established by controlling the controllable release of the tracer from the propping agent and the influence of the position and the flow rate of the propping agent on the tracer flowback curve, the defects of small amount of tracer, large dosage, low sensitivity, large environmental toxicity and the like in the prior art are overcome, the obtained propping agent has the advantages of high detection sensitivity, no pollution, low adsorption, high chemical biological stability, capability of realizing the control of releasing a long-term monitoring output profile, wide use temperature range, no influence on the body health of well site workers and the like, is beneficial to the practical application and popularization of the well site.
Description
Technical Field
The invention relates to the field of preparation of functional proppants, in particular to a preparation method of a trace substance tracing proppant and application of the trace substance tracing proppant in fracture monitoring.
Background
The fracturing technology is the core technology of the current unconventional oil and gas reservoir production increase transformation. Fracturing is an important technical means for artificially fracturing a stratum to increase the yield of an oil well, playing an important role in improving the flow condition of the oil layer and realizing stable yield and yield increase of an oil-gas field. The fracturing technology can be mainly divided into several development stages of explosive fracturing, high-energy nuclear explosive fracturing, acid fracturing, hydraulic fracturing, anhydrous fracturing and the like. The hydraulic fracturing technology is most widely applied at present based on the consideration of safety, economy, environmental protection and the like.
The proppant has very important function in hydraulic fracturing, and is related to the diversion effect of the propped fracture and even the success or failure of the whole hydraulic fracturing construction. Only the fracture that is effectively propped is an important fluid passage in the hydrocarbon production process. Along with the improvement of the fracturing process requirement and the continuous complex construction problem on the site, a large number of different functionalized proppants are continuously researched, the traditional supporting and guiding effect is completed, and meanwhile, a new thought and a new scheme are provided for the engineering problem in a large class of fracturing operation, so that the method becomes the hotspot research content in the current petrochemical field.
Proppant is a fine particulate solid material whose primary function is to maintain the formed fractures after fracturing. Unsupported fractures are easily closed and potential hydrocarbon flow can be restricted. The proppant is generally divided into natural quartz sand, ceramsite, film-coated proppant and the like.
Due to the diversity of geological conditions, simple proppants cannot meet the diversified requirements of the fracturing construction which is emerging continuously. In order to overcome the technical challenges in oil reservoirs and meet the production requirements under various geological conditions, a series of distinctive functional proppants are derived from common proppants.
The detection of the propped fracture is the key of the fracturing construction effect, and the tracing functional proppant has the advantage of distinguishing the propped fracture from the non-propped fracture. The tracing functional proppant is divided into two types, one type is that radioactive substances, stable isotopes, magnetic substances, conductive substances and the like are added into the proppant as markers, the markers do not separate from the proppant when in use, and the proppant and the markers loaded in the proppant are used as a whole and are matched with logging equipment in a stratum; another type does not require logging equipment and the tracer is carried on the proppant surface through a polymer membrane, and in use the tracer is released from the polymer and returns to the surface with the fracturing fluid. Monitoring the content of the tracer in the fracturing fluid, drawing a flowback curve, and performing simulation analysis on the flowback curve to obtain information of the fracture.
The monitoring of the fracturing fracture is the key content of evaluating the construction effect and comprehensively adjusting the construction scheme, the position monitoring of the propping fracture is particularly important in the fracturing monitoring, and the position of the propping fracture can be indicated through the position of the propping agent. Tracer functionalized proppants provide an effective technical means for proppant location indication in a fracture. At present, the most common staged fracturing interval of the horizontal well is 20-30 intervals, and during fracturing construction, each interval is expected to have a unique tracer so as to meet the requirement of finely monitoring the staged fracturing fracture. However, the research in this aspect is still in the beginning and trying stage, and the disadvantages of small amount of tracer, large dosage, low sensitivity, high environmental toxicity and the like exist, which are not beneficial to the practical application and popularization of the well site.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, discloses a preparation method of trace substance tracer proppant and application thereof in fracture monitoring, wherein trace substance tracer is embedded on the traditional proppant-quartz sand to obtain a novel trace substance tracer functionalized proppant, the controllable release of the tracer in practical application is realized, the method for estimating the position of the proppant by using the tracer flowback curve is established by controlling the controllable release of the tracer from the proppant and the influence of the position and the flow rate of the proppant on the tracer flowback curve, the defects of small quantity of the tracer, large dosage, low sensitivity, high environmental toxicity and the like in the prior art are overcome, the obtained proppant has the advantages of high detection sensitivity, no pollution, low adsorption, high chemical and biological stability, and capability of realizing the control release of monitoring a production profile for a long time, The application temperature range is wide, the body health of well site workers cannot be influenced, and the like, and the practical application and popularization of the well site are facilitated.
In order to achieve the purpose, the technical scheme adopted by the application is as follows:
a preparation method of trace substance tracing proppant comprises the following steps:
step S1: preparing HCl solution, adding a proper amount of HCl solution into the rare earth oxide powder, and reacting while stirring; heating to evaporate the solution after the powder solid completely disappears, removing redundant HCl, adding deionized water, and if precipitates exist, continuously adding HCl for dissolving; repeating the steps for a plurality of times until no precipitate is generated after deionized water is added, and obtaining an intermediate solution;
step S2: preparing EDTA-Na according to a certain proportion4Adding the concentrated solution into the intermediate solution obtained in the step S1, evaporating, crystallizing, filtering, washing a filter cake with an ethanol solution for multiple times, drying the filter cake in an oven, adding water to dissolve the obtained product, and recrystallizing and purifying to obtain a trace substance tracer;
step S3: preparing a solvent, and adding the trace substance tracer obtained in the step S2 to fully and uniformly mix; adding the coated polymer into the acetone solution, and continuously stirring until the polymer solid is completely dissolved; and (3) putting the proppant into the polymer solution, fully mixing, draining the polymer solution, completely evaporating acetone, and dispersing and screening to obtain the trace substance tracer functionalized proppant.
Further, when the rare earth oxide powder in the step S1 is replaced with a rare earth salt, the step S1 is: weighing rare earth salt, adding deionized water to completely dissolve the rare earth salt, and filtering the solution by using a filter membrane to obtain an intermediate solution.
Further, the concentration of the HCl solution in the step S1 is 1 mol/L.
Further, the method for adding the appropriate amount of HCl solution to the rare earth oxide powder in step S1 is to wet the rare earth oxide with a small amount of deionized water before adding the HCl solution, so as to prevent the rare earth oxide from reacting with the acid solution to generate a large amount of heat and causing liquid splashing.
Further, the concentration of the solvent solution in the step S2 is 95%.
Further, the concentration of the acetone solution in the step S3 is 95%; the mesh number of the trace substance tracer functionalized proppant obtained in the step S3 is 20-40 meshes.
Further, in the step S3, the coating polymer is ammonium polymethacrylate, and the concentration of the coating polymer is 2.5% to 15.0%.
Further, in the step S3, the solvent is one or more of methanol, ethanol, acetone, and isopropanol.
Further, the trace substance tracer in the step S2 is one of LaEDTA-Na, smeta-Na, and ndeta-Na.
Further, use of the tracer functionalized proppant of any one of claims 1-9 in fracture monitoring.
The invention has the beneficial effects that:
the invention discloses a preparation method of trace substance tracer propping agent and application thereof in crack monitoring, wherein trace substance tracer is embedded on traditional propping agent-quartz sand to obtain a novel trace substance tracer functionalized propping agent, and controllable release of the tracer in practical application is realized, the method for estimating the position of the propping agent by using the tracer flowback curve is established by controlling the controllable release of the tracer from the propping agent and the influence of the position and the flow rate of the propping agent on the tracer flowback curve, the defects of small amount of tracer, large dosage, low sensitivity, large environmental toxicity and the like in the prior art are overcome, the obtained propping agent has the advantages of high detection sensitivity, no pollution, low adsorption, high chemical biological stability, capability of realizing the control of releasing a long-term monitoring output profile, wide use temperature range, no influence on the body health of well site workers and the like, is beneficial to the practical application and popularization of the well site.
The functional tracer proppant developed by taking the trace substance tracer as the core can be conveniently used for monitoring fracturing fractures of oil and gas wells, combines the advantages of various tracer technologies, can optimize the core technology of current fracture monitoring and evaluation, and has the advantages of high sensitivity, small influence on environment, good matching with the existing logging equipment, easy popularization in well sites and construction sites and the like. The formed series products are various in types, and the actual requirements of multiple tracer substances needed by staged fracturing can be met.
Drawings
FIG. 1 is a schematic diagram of the structure of a trace species tagged proppant of the present application;
FIG. 2 is an infrared image of a trace species tracer in an example of the present application;
a, EDTA, among others; B. LaEDTA-Na; c, SmEDTA-Na; D. NdEDTA-Na; E. EDTA-Na 4;
FIG. 3 is an XRD pattern of NdEDTA-Na in examples of the present application;
FIG. 4 is a comparison of the surface topography of a proppant functionalized with quartz sand and trace species tracer in an embodiment of the present application;
wherein, a1 quartz sand; a2 quartz sand local enlarged view; b1 trace species tracer functionalized proppant; b2 partial magnification of trace species tracer functionalized proppant;
FIG. 5 is an infrared analysis spectrum of quartz sand and a sample in an embodiment of the present application;
FIG. 6 is EDS analysis (La element distribution) of a sample in the present example;
FIG. 7 is a flow chart of an experiment for simulating the release of tracer in a fracture in an example of the application;
FIG. 8 is a graph of tracer concentration as a function of liquid outflow volume for an embodiment of the present application;
FIG. 9 is a flowback graph of a simulated staged fracture monitoring in an embodiment of the present application.
Detailed Description
The invention will be further described with reference to the accompanying drawings, without limiting the scope of the invention to the following:
example 1: synthesis of
Selecting La2O3、Nd2O3、Sm(NO3)3·6H2O is taken as raw material and EDTA-Na4Trace substance tracers are prepared in a matching way, and three trace substance tracers of LaEDTA-Na, NdEDTA-Na and SmEDTA-Na are obtained.
1. Synthesizing a trace substance tracer agent:
(1) a1 mol/L HCl solution was prepared (9 ml of 36% HCl in 100ml volumetric flask, 100ml with deionized water). Adding appropriate amount of HCl solution into rare earth oxide (La)2O3、Nd2O3) In the powder, stirring oneSide reaction (adding HCl solution before using a small amount of deionized water to react with rare earth oxide (La)2O3、Nd2O3) Wetting to prevent the liquid from splashing due to a large amount of heat generated by the reaction of the acid solution with the water solution);
(2) when the powder solid completely disappeared, the solution was heated to dryness to remove excess HCl, and then 100ml of deionized water was added, and if any precipitate was present, HCl was added to dissolve. Repeating for multiple times until no precipitate is generated after adding deionized water;
(3) weighing EDTA-Na according to proportion4And preparing a concentrated solution (adding a small amount of deionized water for dissolution), and then adding the solution into the treated solution. Evaporating, crystallizing, filtering, washing the filter cake with 95% ethanol solution for several times, and oven drying the filter cake. Dissolving the obtained product in water, and recrystallizing and purifying to obtain product (LaEDTA-Na, NdEDTA-Na).
Rare earth salts (Sm (NO) other than rare earth oxides3)3·6H2O) can also be used as a raw material for synthesizing the complex.
(1) Weighing rare earth salt, adding deionized water to completely dissolve the rare earth salt, and filtering the solution by using a 0.45 mu m water system filter membrane. Weighing EDTA-Na according to proportion4Dissolving in deionized water, mixing with the solution of rare earth salt, and evaporating for crystallization.
(2) And after the crystals are completely separated out, carrying out vacuum filtration, washing a filter cake with 95% ethanol solution, drying to obtain a crude tracer product, adding deionized water to dissolve the crude tracer product, and recrystallizing to obtain the purified trace substance tracer (SmEDTA-Na).
2. Trace substance tracer functionalized proppant synthesis
The method is characterized in that quartz sand is used as a proppant substrate material, polymethacrylic acid ammonium ester is used as a coating polymer, trace substance tracers (LaEDTA-Na, NdEDTA-Na and SmEDTA-Na) are used as markers, and the trace substance tracer functionalized proppant is synthesized by a solvent evaporation method.
Firstly, preparing 95% acetone solution (95% acetone and 5% deionized water), respectively adding trace substance tracers (LaEDTA-Na, NdEDTA-Na and SmEDTA-Na) to be fully and uniformly mixed, then adding the polymer solid into the acetone solution while stirring, and continuously stirring until the polymer solid is completely dissolved; putting the proppant into a polymer solution, fully mixing, draining the polymer solution to leave the proppant and liquid captured around the proppant, and finally putting the proppant into a fume hood with good ventilation for acetone volatilization; after the acetone is completely evaporated, a layer of coating film is formed on the surface of the quartz sand by the polymer, and trace substance tracers are captured in the coating; obtaining 20/40-mesh trace substance tracer functionalized proppant (LaEDTA-Na, NdEDTA-Na and SmEDTA-Na) after dispersion and screening, wherein the structural schematic diagram of the trace substance tracer functionalized proppant is shown in figure 1.
Example 2: trace substance tracer characterization
The infrared spectrum analysis of the product is carried out by KBr tablet method, and FT-IR of three trace substance tracers and main raw material is shown in figure 2. The infrared spectrum of EDTA in the presence of acid, complex and tetrasodium salt is shown in the figure.
In the figure A is the IR curve of EDTA, 1693cm-1The vibration absorption of the carboxyl group can be assigned as vibration absorption peak of non-coordinated carboxyl group, 3016cm-1Can be assigned as the N-H shock absorption peak. B. C, D are respectively the infrared spectra of La, Nd, Sm and EDTA complex, wherein the free carboxyl absorption peak of EDTA 1693cm-1The vibration absorption of (2) was completely disappeared at 1571cm each-1、1596cm-1、1594cm-1appears-COO-The antisymmetric stretching vibration absorption peak of (1); at 1398cm-1、1409cm-1、1412cm-1The absorption peaks of the three trace substance tracers are respectively-COO-The symmetric stretching vibration absorption peak; 3200-3400 cm-1The broad absorption peak between the two is the absorption peak of water, which proves that the product contains crystal water. E is EDTA-Na41588cm in the infrared spectrum of-1Is represented by-COO-Has an antisymmetric stretching vibration peak of 1420cm-1is-COO-The symmetric stretching vibration absorption peak; 1670cm-1Is EDTA-Na4Impurity H in (1)2EDTA-Na2Carbonyl absorption peak of (2). Three trace substance tracer molecules-COO-The antisymmetric vibration absorption peak and the symmetric vibration absorption peak of the compound and the raw material EDTA-Na4The comparison is shifted, which indicates that the rare earth element successfully generates a complex with EDTA.
The formation and dissociation of the complex in the coordination reaction is in dynamic equilibrium, and the equilibrium constant of this reaction is expressed as a stability constant (or formation constant). The stability constants of LaEDTA-Na and SmEDTA-Na are respectively 15.5, 16.61 and 17.14, and the larger the stability constant is, the more stable the complex is. The stability of the three trace substance tracers shows that the smaller the ionic radius of the central element, the complex-COO-The higher the peak frequency of the antisymmetric stretching vibration absorption, the more covalent the metal-ligand bond increases with decreasing ionic radius, minimizing the carboxylic acid resonance, resulting in an increase in the frequency of the antisymmetric carboxystretching band.
Further, the structures of the three trace substance tracers were confirmed by X-Ray powder Diffraction (XRD) (the radiation source Cu target K α, step width, scanning speed, 2 °/min, and current, 30 mA).
The angle of the NdEDTA-Na main diffraction peak 2 theta is 8.95 degrees, 10.00 degrees, 11.36 degrees, 13.44 degrees, 28.68 degrees and 44.41 degrees; the angle 2 theta of the main diffraction peak of SmEDTA-N is 8.83 degrees, 9.83 degrees, 11.27 degrees, 13.34 degrees and 28.78 degrees; the LaEDTA-Na has main diffraction peak 2 theta angles of 9.63 degrees, 10.24 degrees and 12.10 degrees. XRD pattern of NdEDTA-Na and standard card PDF 00-010-10H12N2O8The diffraction peaks of Nd-Na (ICDD, 1957) have good consistency, and as shown in FIG. 3, the synthesized product is proved to be Nd and EDTA formed a complex.
Example 3: trace species tracer functionalized proppant characterization
(1) Scanning Electron Microscopy (SEM)
SEM analysis is carried out on the quartz sand aggregate and the trace substance tracer functionalized proppant so as to observe the change of the surface appearance of the proppant after the proppant is coated with the polymer. The results obtained are shown in FIG. 4.
Wherein a1 and a2 are quartz sand aggregate particles and a partial enlarged view respectively; b1 and b2 are respectively trace substance labeled proppant and a partial enlarged view thereof. From FIG. 4, it can be observed that the surface of the silica sand particles is relatively uniform, while the surface of the trace species tracer functionalized proppant has some protrusions; the unevenness of the surface of the quartz sand can be observed by continuously amplifying the surfaces of the two particles, and the surface of the polymer-coated proppant is relatively smooth. SEM results show that the surface of the coated proppant sample is smoother.
(2) Infrared spectroscopic analysis
Respectively grinding quartz sand and a trace substance tracer functionalized proppant into powder, and carrying out infrared analysis on a sample by using a KBr tabletting method. FIG. 5 is an infrared analysis of quartz sand and polymer coated samples.
FIG. 5 shows that the infrared spectra of the trace species tracer functionalized proppant are very similar to those of the quartz sand proppant, and the infrared spectra of the tracer functionalized proppant and the quartz sand are 1430cm-1The absorption peak of (A) is a transverse and longitudinal symmetric contraction vibration peak of Si-O, 880cm-1The absorption peak of (A) is that the infrared spectrum of the Si-O symmetrical contraction vibration peak tracer functionalized proppant is at 1724cm-1The position of the ester carbonyl group is added with an absorption peak with weaker intensity, and the absorption peak can be assigned as an absorption peak generated by ester carbonyl group stretching vibration. The polymer used in the synthesis of the trace substance tracer is ammonium polymethacrylate, so that the absorption peak of ester carbonyl groups added on an infrared spectrum of a synthesized proppant sample comes from the polymer coated on the surface of the proppant sample. The results show that the surface of the proppant sample was successfully coated with ammonium polymethacrylate.
(3) Energy Dispersive X-ray Spectroscopy (EDS)
And (3) analyzing the synthesized trace substance tracer functionalized proppant sample by using EDS (electronic Desorption System), and detecting the distribution condition of the trace substance tracer on the surface of the sample. The element content of a single sample is analyzed by energy spectrum analysis, the central element La of trace substance tracer LaEDTA-Na is taken as a detection target, and the test result is shown in figure 6.
Trace element tracer LaEDTA-The La element is distributed on most positions of the surface of the proppant, and the La element is distributed sparsely on few positions of the surface of the proppant particles. But from the part of its bright field map with tracer and the part without tracer distributionThe surface states of the parts have no obvious difference, which indicates that the polymer forms a complete coating layer on the surface of the quartz sand. The lack of distribution of La element at some sites should be the reason why LaEDTA-Na is not uniformly distributed in the polymer solution. The trace substance tracer LaEDTA-Na is a water-soluble substance, the prepared polymer solution takes acetone as a solvent, and the trace substance tracer cannot be uniformly mixed in an organic solvent, so that the trace substance tracer is not distributed at the part of the functionalized proppant.
Example 4: trace tracer functionalized proppant application profiling-fracture location monitoring
The trace substance tracer functionalized proppant adopted in the embodiment is NdEDTA-Na.
1. Investigating trace substance tracer release
A small sand column filled with trace substance tracer functionalized proppant is manufactured, and NaCl and deionized water are alternately injected into the small sand column. And (3) taking the solution flowing out of the sand column, digesting the flowing sample, testing the content of the tracer in the sample by using an ultraviolet-visible spectrophotometer, and inspecting the release rule of the trace substance tracer to obtain the release rules of different NaCl concentrations and different temperatures.
2. Release kinetics model fitting
And (4) performing dynamic model fitting on the release curve of the salinity and temperature experiment. And obtaining the most consistent release kinetics equation by fitting different kinetics models, analyzing variance and comparing.
3. Simulated crack release experiment
As shown in fig. 7, a flowback test of trace species tracers in a fracture system was simulated. The fracture system was simulated using a chromatographic column with a diameter of 1cm and a length of 20 cm. The column is packed with silica sand as proppant and the total void volume between proppants is the fracture volume (Fv), which can be determined by the mass or volume of fluid driven into the column. According to the mass estimation, quartz sand and a sample are respectively filled at preset positions, then the mass of the chromatographic column filled with the quartz sand is weighed, the fluid is driven until the sand column is filled with the liquid, then the mass of the chromatographic column is weighed again, and the difference between the front and the back of the mass is the mass of the driven fluid, so that the corresponding volume can be obtained according to the density of the fluid. According to the fluid volume estimation, the sand column is required to be filled firstly, liquid with known volume is prepared and is driven into the chromatographic column until the chromatographic column is filled with the liquid, and the fracture volume in the chromatographic column can be obtained according to the change of the prepared liquid volume. In the experiment, the two methods are simultaneously adopted to estimate the fracture volume, and the obtained results are basically consistent. The fracture volumes of experiments 1, 2, and 3 were 7.99mL, 7.68mL, and 8.44mL, respectively.
In a simulated fracture flowback test, a certain amount of trace species tracer functionalized proppant is placed at a specific position of a fracture, and the rest part is covered with quartz sand. Injecting a section of NaCl with the concentration of 0.1% (determined by the size of the fracture space) to trigger the release of the tracer in the tracer; after injection, the flow of brine is stopped for 12h to simulate field shut-in, so that enough time is allowed for completing tracer release; finally, deionized water is injected from the opposite direction to simulate the flowback process of the fracturing fluid, and the experimental flow is shown in fig. 7. And (4) carrying out tracer concentration analysis on the effluent solution and drawing a flowback curve.
The method specifically comprises the following steps:
and (3) injecting 0.1% NaCl into the crack system by using 5.0mL/min, driving out the 0.1% NaCl solution injected into the crack system by using different displacement flow rates in the flowback stage, and optimizing an outflow curve to obtain the optimal displacement speed.
In the experiment, the proppant functionalized by the trace substance tracer is respectively paved on the front section, the middle section and the rear section of the crack. When 0.1% NaCl solution is injected into the crack, the flow rate of the solution is 5 mL/min; in the reflux phase three sets of experiments, the flow rate of the fluid was 1 mL/min. One unit of measure was 0.5mL when the solution refluxed from the fracture was taken.
And (3) digesting the received solution sample, and detecting the content of trace substance tracer in the solution by using an ultraviolet spectrophotometry. The specific experimental set-up and results are shown in table 1, and the graphs of the three experiments are plotted in fig. 8. And (3) normalizing the abscissa during drawing, and converting the outflow volume into the crack volume corresponding to each group of experiments. The method for calculating the position of the trace substance tracer functionalized proppant in the fracture system based on the outflow time corresponding to the peak value of the flowback curve comprises the following steps:
wherein:
l: the placement position of the trace substance tracing functionalized proppant is cm;
v: reflux rate, mL/min;
t: the peak value of the tracer flow-back curve corresponds to time min;
L0: simulating the length of a crack system in cm;
v: total volume of the fracture system, cm3。
TABLE 1 simulated Release test parameters
In experiment 1, experiment 2 and experiment 3, the positions of the tracer concentration peak values are respectively 0.31FV, 0.58FV and 1.00FV corresponding to the positions of the trace substance tracer functionalized proppant in the fracture, the deviation values are respectively 1cm, 0.85cm and 0.25cm, and the positions calculated by the tracer flowback curve peak values have certain deviation compared with the placement positions of the tracer functionalized proppant. But the maximum deviation of the test value is only 5% for the length of the whole fracture system, which shows that the peak information of the flowback curve tracer can be used for judging the position of the proppant in the fracture.
Example 4: proppant application profile-staged fracture location monitoring for trace species tracer functionalization
The trace substance tracer functionalized proppant adopted in the embodiment is LaEDTA-Na, NdEDTA-Na and SmEDTA-Na.
In shale gas development, a horizontal well staged fracturing technology is generally adopted. Currently, the most common staged fracturing intervals for horizontal wells are 20 to 30 intervals. As the shale gas enters the stage of encryption development, the number of intervals of the layered fracturing is continuously increased. If the same tracer is used in each interval, it is difficult to distinguish from which fractured interval the tracer concentration peak on the flowback curve is contributing from, and if multiple tracer peaks overlap on the flowback curve, it is difficult to arrive at a single complete tracer peak. It is desirable to have a unique tracer for each interval during the fracturing operation to achieve fine monitoring of the fracture zonal segmentation.
The trace substance tracer functionalized proppant synthesized by the method can also be used for monitoring staged fracturing fractures of horizontal wells. In a conventional proppant injection process, a section of trace species tracer functionalized proppant is injected, with each interval containing a different tagged tracer proppant. Each tracer agent carries information of fracturing fractures of corresponding intervals, and the reconstruction condition of each fracturing interval can be obtained through monitoring various markers in the flow-back fluid, so that more accurate guidance is provided for subsequent mining work.
Simulation experiments are designed in a laboratory to explore the feasibility of the trace substance tracer functionalized proppant synthesized in the research for staged fracturing fracture monitoring. Respectively paving a section of trace substance tracer agent functionalized proppant at the front, middle and rear parts of the chromatographic column, wherein markers carried by each section of proppant are different, and filling common quartz sand proppant at the rest positions. A 20cm long, 1cm diameter chromatography column was used with the Nd tracer-carrying proppant at 4.9cm from the outlet, the Sm tracer-carrying proppant at 10.8cm from the outlet, and the La tracer-carrying proppant at 14.9cm from the outlet. The subsequent experiment steps are the same as the previous section, and the ICP-MS is used for detecting the content of the three markers in the reflux liquid because the specific concentrations of the three trace substances in the solution cannot be distinguished by using the spectrophotometry for detecting the solution.
In the simulation staged fracturing experiment, the flowback curves of the three trace substance tracers are shown in figure 9. As can be seen from the experimental results, the outflow order of the several tracers is consistent with the placement order of each trace species tracer functionalized proppant at the time of experimental design. The sample placed in the middle section is closer to the sample placed in the rear section, and the flowback curve of the sample placed in the middle section is also closer to the flowback curve of the sample placed in the rear section. The relative positions of the peaks of the three flowback curves are consistent with the relative positions of the three trace material marking proppants.
The peaks of each flowback curve were similar for the tracer at the same permeability for each fracture. Under the condition that the permeability of each section of fracture is different, the outflow curve peak shape of the tracer is mainly influenced by the permeability of each section, and the condition of fracturing fracture of each section can be shown in the peak shape of the flowback curve. The proppant functionalized by a plurality of trace substance tracers is used in a fracture system at the same time, and a plurality of tracer information can be obtained from the reflux liquid at the same time. And (3) independently analyzing each flowback curve to obtain the fracture information of the interval corresponding to the trace substance tracer functionalized proppant.
In conclusion, the invention discloses a preparation method of trace substance tracer proppant and application thereof in fracture monitoring, wherein trace substance tracer is embedded on traditional proppant-quartz sand to obtain a novel trace substance tracer functionalized proppant, the controllable release of the tracer in practical application is realized, the method for estimating the position of the proppant by using the tracer flowback curve is established by controlling the controllable release of the tracer from the proppant and the influence of the position and the flow rate of the proppant on the tracer flowback curve, the defects of small quantity of the tracer, large dosage, low sensitivity, large environmental toxicity and the like in the prior art are overcome, the obtained proppant has the advantages of high detection sensitivity, no pollution, low adsorption, high chemical biological stability, capability of realizing long-term monitoring of release, wide range of use temperature, no influence on the body health of well site workers and the like, is favorable for the practical application and popularization of well sites
Thus, it will be appreciated by those skilled in the art that while embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications can be made which conform to the principles of the invention, as may be directly determined or derived from the disclosure herein, without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (9)
1. A preparation method of trace substance tracing proppant is characterized by comprising the following steps:
step S1: preparing HCl solution, adding a proper amount of HCl solution into the rare earth oxide powder, and reacting while stirring; when the powder solid completely disappears, heating to evaporate the solution to dryness, removing redundant HCl, adding deionized water, and if precipitates are formed, continuously adding HCl for dissolving; repeating the steps for a plurality of times until no precipitate is generated after deionized water is added, and obtaining an intermediate solution;
step S2: preparing EDTA-Na according to a certain proportion4Adding the concentrated solution into the intermediate solution obtained in the step S1, evaporating, crystallizing, filtering, washing the filter cake with an ethanol solution for multiple times, drying the filter cake in an oven, dissolving the obtained product in water, recrystallizing and purifying to obtain a trace substance tracer, wherein the trace substance tracer is one of LaEDTA-Na, SmEDTA-Na and NdEDTA-Na;
step S3: preparing a solvent, and adding the trace substance tracer obtained in the step S2 to fully and uniformly mix; adding the coated polymer ammonium polymethacrylate into an acetone solution, and continuously stirring until the polymer solid is completely dissolved; and (3) putting the proppant into the polymer solution, fully mixing, draining the polymer solution, completely evaporating acetone, and dispersing and screening to obtain the trace substance tracer functionalized proppant.
2. The method of claim 1, wherein when the rare earth oxide powder is replaced with a rare earth salt in the step S1, the step S1 is: weighing rare earth salt, adding deionized water to completely dissolve the rare earth salt, and filtering the solution by using a filter membrane to obtain an intermediate solution.
3. The method of claim 1, wherein the concentration of HCl solution in step S1 is 1 mol/L.
4. The method for preparing a trace species tracing proppant as set forth in claim 1, wherein the adding of the appropriate amount of HCl solution to the rare earth oxide powder in step S1 is carried out by wetting the rare earth oxide with a small amount of deionized water prior to adding the HCl solution to prevent splashing of the rare earth oxide due to the large exothermic reaction with the acid solution.
5. The method of claim 1, wherein the solvent solution concentration in step S2 is 95%.
6. The method of claim 1, wherein the concentration of the acetone solution in step S3 is 95%; the mesh number of the trace substance tracer functionalized proppant obtained in the step S3 is 20-40 meshes.
7. The method of claim 1, wherein the concentration of ammonium polymethacrylate in step S3 is 2.5% -15.0%.
8. The method as claimed in claim 1, wherein the solvent in step S3 is one or more selected from methanol, ethanol, acetone, and isopropanol.
9. Use of a tracer functionalized proppant in fracture monitoring, wherein the tracer functionalized proppant is prepared by the method for preparing a tracer functionalized proppant according to any one of claims 1 to 8 in fracture monitoring.
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| CN115851255B (en) * | 2023-02-28 | 2023-05-02 | 成都理工大学 | Magnetic nano catalytic proppant and preparation method and application thereof |
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