Preparation and Usage Method of Oil Sludge Profile Control Tracer

Abstract

The present application provides a preparation and usage method of a sludge profile control tracer, belonging to the technical field of profile control and water plugging for oil and water wells in oil exploitation. The preparation method includes: mixing sludge with water at 40 - 75 °C, stirring and then standing to obtain an oil-water stratified liquid; separating the floating oil and free water in the oil-water stratified liquid to obtain the target sludge; soaking the target sludge in a cationic surfactant solution for 24 h to obtain a soaking solution; removing part of the water in the soaking solution to make the viscosity of the soaking solution within the first viscosity range to obtain the sludge profile control tracer. This method can enable the cationic surfactant in the cationic surfactant solution to combine with the sludge, so that after the obtained sludge profile control tracer is injected into the formation along with the sludge, it is not easy to separate from the sludge; in this way, the sludge breakthrough parameters can be accurately determined through this sludge profile control tracer, and further the accuracy of predicting the breakthrough situation of the sludge in the beneficiary oil well can be improved.

Description

Technical Field

[0001] This application relates to the technical field of profile control and water plugging for oil and water wells in oil extraction, and particularly relates to a preparation and usage method of an oily sludge profile control tracer. Background Art

[0002] During the production process of an oilfield, generally the oily sludge produced in the oilfield is injected into an injection well as a profile control agent to plug large pore channels in the formation between the injection well and the production well, preventing the injected water in the injection well from flowing into the production well. However, after the oily sludge is injected into the formation through the injection well, the oily sludge is likely to flow into the beneficiary production well corresponding to the injection well. Once a large amount of oily sludge flows into the beneficiary production well, it will block the oil production pump and the oil pipeline of the beneficiary production well, and further affect the normal operation of the beneficiary production well. Therefore, it is necessary to use an oily sludge profile control tracer to predict the outflow situation of the oily sludge in the beneficiary production well.

[0003] In related technologies, the oily sludge profile control tracer is generally a radioactive isotope tracer or a chemical agent tracer. Generally, the oily sludge carries a radioactive isotope tracer or a chemical agent tracer and is injected into the formation through an injection well. Then, by detecting the content of the radioactive isotope tracer or the chemical agent tracer in the produced fluid of the beneficiary production well corresponding to the injection well, the outflow parameters of the oily sludge are determined, and then the outflow situation of the oily sludge in the beneficiary production well is predicted based on the outflow parameters of the oily sludge. Since the radioactive isotope tracer or the chemical agent tracer will dissolve and diffuse in water after encountering the water in the formation and be completely separated from the oily sludge, the detected content of the radioactive isotope tracer or the chemical agent tracer cannot accurately determine the outflow parameters of the oily sludge, thus reducing the accuracy of predicting the outflow situation of the oily sludge in the beneficiary production well. Summary of the Invention

[0004] The embodiments of this application provide a preparation and usage method of an oily sludge profile control tracer, which can improve the accuracy of predicting the outflow situation of the oily sludge in the beneficiary production well. The technical solution is as follows:

[0005] On the one hand, a preparation and usage method of an oily sludge profile control tracer is provided, and the method includes:

[0006] Mix the oily sludge with water at 40 - 75 °C, stir and then let it stand to obtain an oil-water stratified liquid;

[0007] Separate the floating oil and free water in the oil-water stratified liquid to obtain target oily sludge;

[0008] Soak the target oily sludge in a cationic surfactant solution for 24 h to obtain a soaking solution;

[0009] Remove part of the water in the soaking solution to make the viscosity of the soaking solution within a first viscosity range to obtain an oily sludge profile control tracer.

[0010] In a possible implementation, the mass concentration of the cationic surfactant solution is 0.5% to 10%.

[0011] In a possible implementation, the cationic surfactant in the cationic surfactant solution is a quaternary ammonium salt cationic surfactant.

[0012] In a possible implementation, the quaternary ammonium salt cationic surfactant includes at least one of cetyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium bromide, dicetyl dimethyl ammonium chloride, and double cationic surfactants.

[0013] In a possible implementation, the first viscosity range is 40 to 160 s.

[0014] On the other hand, a method for using a sludge profile control tracer is provided, and the method includes:

[0015] Dividing the sludge into 10% to 25% of the pre-sludge and 75% to 90% of the remaining sludge;

[0016] Mixing the pre-sludge with the sludge profile control tracer to obtain a tracer sludge system;

[0017] Sequentially injecting the tracer sludge system and the remaining sludge into an injection well;

[0018] Regularly sampling the produced fluid of the beneficiary oil well to obtain a produced fluid sample, where the beneficiary oil well is the oil well to which the tracer sludge system and the remaining sludge injected into the injection well flow;

[0019] Centrifuging the produced fluid sample, separating the oil, and then filtering the remaining liquid to obtain a filtrate;

[0020] Mixing the filtrate with a cleaning agent to obtain a mixed solution;

[0021] After standing the mixed solution for 6 h, centrifuging the mixed solution to obtain a test solution;

[0022] Detecting the cationic surfactant in the test solution to obtain a sludge breakthrough parameter, where the sludge breakthrough parameter is used to represent the breakthrough situation of the sludge in the beneficiary oil well.

[0023] In a possible implementation, the mass ratio of the pre-sludge to the sludge profile control tracer is 1 to 5:1.

[0024] In a possible implementation, the cleaning agent is an ethanol solvent or a methanol solvent.

[0025] In a possible implementation, the time interval for the regular sampling is 3 to 7 days.

[0026] In a possible implementation, the amount of the produced fluid sample is 200 to 500 ml.

[0027] The beneficial effects of the technical solution provided by the embodiments of the present application at least include:

[0028] The embodiments of the present application provide a preparation method of an oily sludge profile control tracer. After separating the floating oil and free water in the oily sludge, the method immerses the separated oily sludge in a cationic surfactant solution. In this way, the cationic surfactant in the cationic surfactant solution can combine with the oily sludge. Further, after the obtained oily sludge profile control tracer is injected into the formation with the oily sludge, it is not easy to separate from the oily sludge. In this way, the parameters of the oily sludge breakthrough can be accurately determined through the oily sludge profile control tracer, and further, the accuracy of predicting the breakthrough situation of the oily sludge in the beneficiary oil well can be improved. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0030] Figure 1 is a flowchart of a preparation method of an oily sludge profile control tracer provided by the embodiments of the present application;

[0031] Figure 2 is a flowchart of a usage method of an oily sludge profile control tracer provided by the embodiments of the present application. Detailed Embodiments

[0032] To make the objectives, technical solutions, and advantages of the present application clearer, the following will further describe the embodiments of the present application in detail with reference to the drawings.

[0033] The terms "first", "second", "third", and "fourth", etc. in the specification, claims, and drawings of the present application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0034] The embodiments of the present application provide a preparation method of an oily sludge profile control tracer. Refer toFigure 1 , the method includes:

[0035] Step 101: Mix the oily sludge with water at 40 - 75°C, stir and then let it stand to obtain an oil-water stratified liquid.

[0036] Among them, the oily sludge can be oil-bearing mud and sand carried by the produced fluid of oil production wells, oily sludge formed by recovering the spilled crude oil, sediment mud and sand generated by the oilfield gathering and transportation processing system, etc.

[0037] Among them, the oily sludge is added to water at 40 - 75°C for mixing.

[0038] Among them, the water can be tap water or formation reinjected water; the temperature of the water can be 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 54°C, 55°C, 58°C, 60°C, 62°C, 63°C, 65°C, 68°C, 70°C, 73°C, 75°C, etc.

[0039] In the embodiment of the present application, the oily sludge is dissolved in water at a relatively high temperature of 40 - 75°C, which is convenient for floating the oil in the oily sludge, and then obtaining floating oil that is convenient for separation.

[0040] Step 102: Separate the floating oil and free water from the oil-water stratified liquid to obtain the target oily sludge.

[0041] Among them, the top layer of the oil-water stratified liquid is floating oil, the middle layer is free water, and the bottom layer is the target oily sludge; the floating oil in the top layer and the free water in the middle layer are separated from the oil-water stratified liquid to obtain the target oily sludge.

[0042] Step 103: Immerse the target oily sludge in a cationic surfactant solution for 24 hours to obtain an immersion liquid.

[0043] Among them, the mass concentration of the cationic surfactant solution is 0.5% - 10%. For example, the mass concentration of the cationic surfactant solution can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, etc.

[0044] Among them, the cationic surfactant in the cationic surfactant solution is a quaternary ammonium salt cationic surfactant. The quaternary ammonium salt cationic surfactants include at least one of cetyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium bromide, dicetyl dimethyl ammonium chloride, and double cationic surfactants.

[0045] In one possible implementation, the cationic surfactant includes cetyl dimethyl benzyl ammonium chloride and cetyl trimethyl ammonium chloride. In another possible implementation, the cationic surfactant includes cetyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, and dodecyl dimethyl benzyl ammonium chloride. In another possible implementation, the cationic surfactant includes cetyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium bromide, dicetyl dimethyl ammonium chloride, and a double cationic surfactant.

[0046] Among them, the solvent of the cationic surfactant solution is tap water or formation reinjected water; the cationic surfactant is dissolved by tap water or formation reinjected water to obtain the cationic surfactant solution.

[0047] Among them, the salinity of the oilfield reinjected water is less than 5000 ppm. For example, the salinity can be 4800 ppm, 4500 ppm, 4300 ppm, 4000 ppm, 3800 ppm, 3500 ppm, 3300 ppm, 3000 ppm, 2800 ppm, 2500 ppm, 2300 ppm, 2000 ppm, 1800 ppm, 1500 ppm, 1000 ppm, etc.

[0048] In the embodiment of the present application, soaking the target oil sludge in the cationic surfactant solution for 24 h can enable the cationic surfactant to bind to the target oil sludge. And, the target oil sludge is the oil sludge from which floating oil and free water are separated, which makes it easier for the cationic surfactant solution to penetrate into the target oil sludge, and then the cationic surfactant in the cationic surfactant solution binds to the target oil sludge.

[0049] Step 104: Remove part of the water in the soaking solution to make the viscosity of the soaking solution within the first viscosity range to obtain the oil sludge profile control tracer.

[0050] Among them, the first viscosity range is 40 - 160 s, and this viscosity is the MacMichael viscosity. For example, the viscosity can be 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, 90 s, 95 s, 100 s, 105 s, 110 s, 115 s, 120 s, 125 s, 130 s, 135 s, 140 s, 145 s, 150 s, 155 s, 160 s, etc.

[0051] In the embodiment of the present application, making the viscosity of the soaking solution within the first viscosity range enables the obtained oil sludge profile control tracer to have a certain fluidity, which matches the fluidity of the oil sludge. Then, after mixing the oil sludge profile control tracer with the oil sludge, it can flow with the oil sludge in the injection well and the formation.

[0052] An embodiment of the present application provides a method for preparing a sludge profile control tracer. After separating the floating oil and free water in the sludge, the sludge is immersed in a cationic surfactant solution. In this way, the cationic surfactant in the cationic surfactant solution can combine with the sludge, so that the obtained sludge profile control tracer is not easily separated from the sludge after being injected into the formation with the sludge. In this way, the parameters of the sludge breakthrough can be accurately determined through the sludge profile control tracer, and then the accuracy of predicting the breakthrough situation of the sludge in the beneficiary oil well can be improved.

[0053] An embodiment of the present application provides a method for using a sludge profile control tracer. See Figure 2 , and the method includes:

[0054] Step 201: Divide the sludge into 10% - 25% of the pre-sludge and 75% - 90% of the remaining sludge.

[0055] Among them, the sum of the masses of the pre-sludge and the remaining sludge is 100%. For example, the mass fractions of the pre-sludge and the remaining sludge can be 10% and 90%, 15% and 85%, 20% and 80%, 25% and 75%, etc.

[0056] Step 202: Mix the pre-sludge with the sludge profile control tracer to obtain a tracer sludge system.

[0057] Among them, the pre-sludge and the sludge profile control tracer are mixed evenly so that the sludge profile control tracer is evenly dispersed in the pre-sludge.

[0058] Among them, the mass ratio of the pre-sludge to the sludge profile control tracer is 1 - 5:1. For example, the mass ratio of the pre-sludge to the sludge profile control tracer can be 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, and 5:1, etc.

[0059] Step 203: Inject the tracer sludge system and the remaining sludge into the injection well in sequence.

[0060] Among them, the tracer sludge system is injected into the injection well as the pre-slug of the remaining sludge, and then the remaining sludge is continuously injected.

[0061] Step 204: Regularly sample the produced fluid of the beneficiary oil well to obtain a produced fluid sample.

[0062] Among them, the beneficiary oil well is the oil well where the tracer sludge system and the remaining sludge injected into the injection well break through.

[0063] Among them, the beneficiary oil well is the oil well near the injection well, and it is the oil well where the oil recovery rate can be improved after injecting water into the injection well.

[0064] Among them, the time interval for regular sampling is 3 to 7 days; for example, the time interval for sampling can be 3 days, 4 days, 5 days, 6 days, 7 days, etc.

[0065] Among them, the time interval for sampling is set according to the connectivity between the injection well and the beneficiary oil well. For example, if the pore channels in the formation between the injection well and the beneficiary oil well are large and the cross-flow rate of the oil sludge is fast, the time interval for sampling is small. If the pore channels in the formation between the injection well and the beneficiary oil well are small and the cross-flow rate of the oil sludge is slow, the time interval for sampling is small.

[0066] Among them, the time for the first sampling is 12 to 15 days after the tracer oil sludge system is injected into the injection well. For example, the first sampling is carried out 12 days after the tracer oil sludge system is injected into the injection well, and then samples are taken every 7 days. Another example is that the first sampling is carried out 15 days after the tracer oil sludge system is injected into the injection well, and then samples are taken every 5 days.

[0067] Among them, the amount of the produced liquid sample is 200 to 500 mL; for example, it can be 200 ml, 250 ml, 300 ml, 350 ml, 400 ml, 450 ml, 500 ml, etc.

[0068] Step 205: Centrifuge the produced liquid sample. After separating the oil, filter the remaining liquid to obtain a filtrate.

[0069] Among them, the produced liquid sample is centrifuged by a separator to separate the oil.

[0070] Among them, the remaining liquid includes water and solid content. The remaining liquid is filtered through a quantitative filter paper to filter out the water and obtain a filtrate containing only the solid content.

[0071] Among them, if the produced liquid sample contains a cationic surfactant, the cationic surfactant binds to the solid content.

[0072] Step 206: Mix the filtrate with a cleaning agent to obtain a mixed solution.

[0073] Among them, the cleaning agent is an ethanol solvent or a methanol solvent.

[0074] Among them, the filtrate remaining on the quantitative filter paper is cleaned with the cleaning agent to mix the filtrate with the cleaning agent, and then the solid content is dissolved in the cleaning agent to obtain a mixed solution.

[0075] Step 207: After standing the mixed solution for 6 h, centrifuge the mixed solution to obtain a test solution.

[0076] Among them, after the mixed solution stands, the solid content insoluble in the cleaning agent precipitates, thereby improving the centrifugation effect.

[0077] Among them, the mixed solution is centrifuged by a centrifuge to dissolve the cationic surfactant in the solid content in the cleaning agent, and the insoluble solid content in the mixed solution is separated to obtain a transparent cleaning agent, that is, the test solution. If the produced liquid sample contains a cationic surfactant, the test solution contains a cationic surfactant.

[0078] Step 208: Detect the cationic surfactant in the test solution to obtain the sludge breakthrough parameter.

[0079] Among them, the sludge breakthrough parameter is used to represent the breakthrough situation of the sludge in the beneficiary oil well. The sludge breakthrough parameter is the time when the cationic surfactant appears in the beneficiary oil well after the tracer sludge system and the remaining sludge are injected into the injection well.

[0080] Among them, the type and content of the cationic surfactant in the test solution are detected. If the cationic surfactant dissolved in the test solution is consistent with the characteristics of the cationic surfactant in the sludge profile control tracer, it indicates that the tracer sludge system and the remaining sludge have broken through to the beneficiary oil well, and the sludge breakthrough parameter can be obtained; furthermore, by combining the change law of the content of the cationic surfactant measured at different sampling times, the degree and change trend of the sludge breaking through to the beneficiary oil well can be predicted.

[0081] Among them, the detection methods can be ultraviolet spectrophotometry, thin-layer chromatography, high-performance liquid chromatography, two-phase titration, electrochemical sensor analysis, resonance scattering method, capillary electrophoresis, oscillopolarography, etc.

[0082] Among them, the instrument used for ultraviolet spectrophotometry is the UV7 ultraviolet spectrophotometer manufactured in Switzerland.

[0083] The embodiment of the present application provides a method for using a sludge profile control tracer. After mixing the sludge profile control tracer with the pre-sludge and injecting it into the formation, by detecting the cationic surfactant in the produced liquid of the beneficiary oil well, since the cationic surfactant binds to the sludge and is not easily separated, in this way, the sludge breakthrough parameter obtained by detecting the cationic surfactant has high accuracy, thereby improving the accuracy of predicting the breakthrough situation of the sludge in the beneficiary oil well.

[0084] The technical solution of the present invention will be described in detail below through specific embodiments.

[0085] In the following specific embodiments, the operations not specified in terms of conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. The raw materials not specified in terms of the manufacturer and specifications are all conventional products that can be obtained through commercial purchase.

[0086] Example 1

[0087] Taking Well Gang 10X, a water injection well in Dagang Oilfield where sludge profile control is implemented, as an example, the total designed volume of the sludge for profile control is 3000 cubic meters. The corresponding beneficiary oil well, Well Gang 12X, has a liquid production water cut of 95% during normal production. The sludge used for profile control is the sludge in the sludge stacking pond of Gangdong Joint Station. When Well Gang 10X is in normal production, the pipeline injection water is formation reinjection water, with a daily injection of 100 cubic meters. The measured temperature of the formation reinjection water is 45°C, and the salinity of the reinjection water is 3700 ppm. The cationic surfactant is cetyltrimethylammonium bromide, which is an industrial product available on the market.

[0088] The sludge is added to the formation reinjection water at 45°C for mixing. After stirring, it is left standing to obtain an oil-water stratified liquid. The floating oil and free water in the oil-water stratified liquid are separated to obtain the target sludge. The formation reinjection water with a salinity of 3700 ppm from Well Gang 10X is used to dissolve cetyltrimethylammonium bromide to prepare a cetyltrimethylammonium bromide solution with a mass concentration of 5%. The target sludge is soaked in the cetyltrimethylammonium bromide solution for 24 hours to obtain a soaking solution. Part of the water in the soaking solution is removed to make the soaking solution have fluidity, and the viscosity of the soaking solution is 65 s, obtaining the sludge profile control tracer used in this example.

[0089] The 3000 cubic meters of sludge is divided into 10% pre-sludge and 90% remaining sludge, that is, 300 cubic meters of pre-sludge and 2700 cubic meters of remaining sludge. The pre-sludge and the sludge profile control tracer are mixed according to a mass ratio of 1:1 to obtain a 600 cubic meter tracer sludge system. The tracer sludge system is first injected into the tracable sludge system, and then the remaining 2700 cubic meters of remaining sludge is continuously injected. Among them, in order to compare with the conventional tracer, after the tracer sludge system and the remaining sludge are successively injected into Well Gang 10X, formation reinjection water is injected into Well Gang 10X, and the injection rate is 100 cubic meters per day.

[0090] 15 days after the tracer sludge system is injected into Well Gang 10X, the produced liquid of the beneficiary oil well, Well Gang 12X, is sampled to obtain a 300 ml produced liquid sample. The produced liquid sample is centrifuged by a centrifuge to separate the oil, and the remaining liquid is filtered with quantitative filter paper to filter out the water in the remaining liquid, obtaining a filter residue with only solid content remaining. The filter residue remaining on the quantitative filter paper is washed with ethanol solvent to obtain a mixed solution. After the mixed solution is left standing for 6 hours, it is centrifuged by a centrifuge to obtain a test solution.

[0091] An ultraviolet spectrophotometer is used to detect the absorbance intensity of cetyltrimethylammonium bromide in the test solution at a wavelength of 263 nm. It is known that the absorbance intensity of the formation reinjection water of Well Gang 10X itself at a wavelength of 263 nm is 0.0048. After sampling 15 days after the tracer sludge system is injected into Well Gang 10X, the produced liquid of the beneficiary oil well, Well Gang 12X, is sampled every 7 days, and the absorbance of the produced liquid sample is measured 9 times continuously according to the same detection method.

[0092] Among them, the absorbance values measured each time are 0.0048, 0.0047, 0.0048, 0.0052, 0.0051, 0.0048, 0.0048, 0.0154, 0.0625 in sequence. The absorbance increased after the 64th day, indicating that cetyltrimethylammonium bromide appeared in the produced fluid sample, that is, it indicated that the oily sludge flowed into the beneficiary oil well after the 64th day of profile control implementation in Well Gang 10X; moreover, as time went by, the absorbance was even greater after the 71st day, indicating that the oily sludge continuously flowed into the beneficiary oil well over time.

[0093] Comparative Example 1

[0094] 1% ammonium thiocyanate, 1% ultrafine calcium powder and 1% tritiated water were incorporated into the tracer oily sludge system in Example 1. 15 days after injecting the tracer oily sludge system into Well Gang 10X, tritiated water and calcium bisulfate were detected in the produced fluid sample of Well Gang 12X, and the ultrafine calcium powder could not be separated from the minerals in the produced fluid sample.

[0095] It can be seen by comparison that radioactive isotope tracers or chemical agent tracers such as tritiated water and calcium bisulfate, after being injected into the formation, will dissolve and diffuse in the formation water and be completely separated from the oily sludge, and their migration laws cannot represent the migration law of the oily sludge. After tritiated water and calcium bisulfate are separated from the oily sludge, they dissolve in water and are easily transported to the beneficiary oil well with the water. Therefore, their migration laws cannot represent the migration law of the oily sludge. Furthermore, using radioactive isotope tracers or chemical agent tracers as tracers for oily sludge profile control to predict the breakthrough situation of oily sludge in the beneficiary oil well has low accuracy.

[0096] Moreover, using ultrafine powder particles such as ultrafine calcium powder as tracers for oily sludge profile control, the ultrafine powder particles are generally identified by the method of observing the particle morphology downhole. Since the particle sizes of the ultrafine powder particles and the solid-phase particles of the oily sludge itself are basically the same, and the fine particle mineral components in the oily sludge are complex, it is difficult to identify the ultrafine powder particles used as tracers for oily sludge profile control in the produced fluid sample; especially in the initial stage when the oily sludge flows into the beneficiary oil well, it is even more difficult to identify the extremely small amount of ultrafine powder particles in the produced fluid sample.

[0097] Example 2

[0098] Taking Well Gang X-2-1 in Dagang Oilfield where sludge profile control is implemented as an example, the total designed volume of the sludge for profile control is 4,200 cubic meters. The corresponding beneficiary oil well, Well Xi X-2-1-1, has a liquid production water cut of 98% during normal production. The sludge used for profile control is the sludge at the bottom of the oil-water settling tank in the joint station of Oil Production Plant Y. When Well Gang X-2-1 is in normal production, the pipeline injection water is formation reinjection water, with a daily injection of 150 cubic meters. The measured temperature of the formation reinjection water is 50°C, and the salinity of the reinjection water is 4,557 ppm. The cationic surfactant is dodecyl dimethyl benzyl ammonium chloride, which is an industrial product available on the market.

[0099] The sludge is added to the formation reinjection water at 50°C for mixing. After stirring and standing, an oil-water stratified liquid is obtained. The floating oil and free water in the oil-water stratified liquid are separated to obtain the target sludge. The formation reinjection water with a salinity of 4,557 ppm from Well Gang X-2-1 is used to dissolve dodecyl dimethyl benzyl ammonium chloride to prepare a dodecyl dimethyl benzyl ammonium chloride solution with a mass concentration of 10%. The target sludge is soaked in the dodecyl dimethyl benzyl ammonium chloride solution for 24 hours to obtain a soaking solution. Part of the water in the soaking solution is removed to make the soaking solution have fluidity. The viscosity of the soaking solution is 59 s to obtain the sludge profile control tracer used in this example.

[0100] The 4,200 cubic meters of sludge is divided into 12.5% pre-sludge and 87.5% remaining sludge, that is, 525 cubic meters of pre-sludge and 3,675 cubic meters of remaining sludge. The pre-sludge and the sludge profile control tracer are mixed according to a mass ratio of 1:1 to obtain a 630 cubic meter tracer sludge system. The tracer sludge system is first injected into the traceable sludge system, and then the remaining 3,675 cubic meters of remaining sludge is continuously injected. Among them, in order to compare with the conventional tracer, after the tracer sludge system and the remaining sludge are successively injected into Well Gang X-2-1, formation reinjection water is injected into Well Gang X-2-1 at an injection rate of 150 cubic meters per day.

[0101] Twelve days after the tracer sludge system is injected into Well Gang X-2-1, the produced liquid of the beneficiary oil well, Well Xi X-2-1-1, is sampled to obtain a 200 ml produced liquid sample. The produced liquid sample is centrifuged by a centrifuge to separate the oil. The remaining liquid is filtered using quantitative filter paper to filter out the water in the remaining liquid to obtain a filter residue with only solid content. The filter residue remaining on the quantitative filter paper is washed with ethanol solvent to obtain a mixed solution. After the mixed solution stands for 6 hours, the mixed solution is centrifuged by a centrifuge to obtain a test solution.

[0102] The absorbance of the association complex of dodecyldimethylbenzylammonium chloride and the chromogenic reagent dichlorofluorescein in the test solution was detected using an ultraviolet spectrophotometer at a wavelength of 519 nm. It is known that the absorbance of the formation reinjected water of Well Gang X-2-1 itself at a wavelength of 519 nm is 0.0022. After sampling 12 days after injecting the tracer oil sludge system into Well Gang X-2-1, the produced fluid of Beneficiary Well Xi X-2-1-1 was sampled every 7 days, and the absorbance of the produced fluid samples was measured 8 times continuously according to the same detection method.

[0103] Among them, the absorbances measured each time are 0.0022, 0.0024, 0.0023, 0.0022, 0.0022, 0.0023, 0.0133, and 0.0755 in sequence. The absorbance increased after 54 days, indicating that dodecyldimethylbenzylammonium chloride appeared in the produced fluid sample, that is, it indicated that the oil sludge flowed into the beneficiary well 54 days after the profile control was implemented in Well Gang X-2-1; moreover, as time passed, the absorbance was even greater after 61 days, indicating that the oil sludge continuously flowed into the beneficiary well over time.

[0104] Comparative Example 2

[0105] 1% ammonium thiocyanate, 1% ultrafine calcium powder, and 1% tritiated water were incorporated into the tracer oil sludge system in Example 2. 15 days after injecting the tracer oil sludge system into Well Gang X-2-1, tritiated water and calcium bisulfate were detected in the produced fluid sample of Well Xi X-2-1-1, and the ultrafine calcium powder could not be separated from the minerals in the produced fluid sample.

[0106] The embodiment of the present application provides a preparation method of an oil sludge profile control tracer. After separating the floating oil and free water in the oil sludge, it is soaked in a cationic surfactant solution. In this way, the cationic surfactant in the cationic surfactant solution can combine with the oil sludge, and then the obtained oil sludge profile control tracer is not easily separated from the oil sludge after being injected into the formation with the oil sludge; in this way, the oil sludge breakthrough parameters can be accurately determined through this oil sludge profile control tracer, and further the accuracy of predicting the breakthrough situation of the oil sludge in the beneficiary well can be improved.

[0107] The embodiment of the present application provides a usage method of an oil sludge profile control tracer. After mixing the oil sludge profile control tracer with the pre-injected oil sludge and injecting it into the formation, by detecting the cationic surfactant in the produced fluid of the beneficiary well, since the cationic surfactant combines with the oil sludge and is not easily separated, in this way, the accuracy of the oil sludge breakthrough parameters obtained by detecting the cationic surfactant is high, thereby improving the accuracy of predicting the breakthrough situation of the oil sludge in the beneficiary well.

[0108] The above are only optional embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included within the protection scope of the present application.

Claims

1. A method for using a sludge profile control tracer, characterized in that, applying a sludge profile control tracer prepared by the following preparation method, the using method includes: Dividing the sludge into 10% - 25% of the pre - sludge and 75% - 90% of the remaining sludge; Mixing the pre - sludge with the sludge profile control tracer to obtain a tracer sludge system, and the mass ratio of the pre - sludge to the sludge profile control tracer is 1 - 5:1; Injecting the tracer sludge system as the pre - slug of the remaining sludge into the injection well, and then continuously injecting the remaining sludge; Regularly sampling the produced fluid of the beneficiary oil well to obtain a produced fluid sample, where the beneficiary oil well is the oil well into which the tracer sludge system and the remaining sludge injected into the injection well flow; Centrifuging the produced fluid sample, separating the oil, and then filtering the remaining liquid to obtain a filtrate; Mixing the filtrate with a cleaning agent to obtain a mixed solution; After standing the mixed solution for 6 h, centrifuging the mixed solution to obtain a test solution; Detecting the cationic surfactant in the test solution to obtain a sludge breakthrough parameter, and the sludge breakthrough parameter is used to represent the breakthrough situation of the sludge in the beneficiary oil well; Wherein, the preparation method of the sludge profile control tracer includes: Mixing the sludge with water at 40 - 75 °C, stirring and then standing to obtain an oil - water stratified liquid, where the sludge is the oily sludge and sand carried by the produced fluid of the oil production well, the oily sludge formed by recycling the stranded crude oil, or the sediment sludge and sand generated by the oilfield gathering and transportation processing system; Separating the floating oil and free water in the oil - water stratified liquid to obtain a target sludge; Soaking the target sludge in a cationic surfactant solution for 24 h to obtain a soaking solution, where the mass concentration of the cationic surfactant solution is 0.5% - 10%, and the cationic surfactant in the cationic surfactant solution includes at least one of cetyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, dodecyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium bromide, bis - cetyl dimethyl ammonium chloride, and double - cationic surfactants; Removing part of the water in the soaking solution to make the viscosity of the soaking solution within a first viscosity range to obtain a sludge profile control tracer.

2. The method for using a sludge profile control tracer according to claim 1, characterized in that, the cleaning agent is an ethanol solvent or a methanol solvent.

3. The method for using a sludge profile control tracer according to claim 1, characterized in that, the time interval for regular sampling is 3 - 7 days.

4. The method for using a sludge profile control tracer according to claim 1, characterized in that, the amount of the produced fluid sample is 200 - 500 ml.

5. The method for using a sludge profile control tracer according to claim 1, characterized in that, the first viscosity range is 40 - 160 s.

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