Method and system for predicting viscosity of crude oil

Abstract

The invention discloses a method and system for predicting viscosity of crude oil, and the method comprises the following steps: heating a plurality of experimental rock samples taken from an oil-bearing reservoir to obtain corresponding products, and measuring the yield data of the corresponding products, the products comprise a first hydrocarbon product of light and medium components and a second hydrocarbon product of heavy components in the oil-bearing reservoir; respectively obtaining the content of light and medium components and the content of heavy components of each experimental rock sample according to the yield data, and calculating the ratio of the content of the light and medium components to the content of the heavy components; respectively carrying out crude oil viscosity measurement on the production oil of the production layer where each experimental rock sample is located, and establishing a correlation between the ratio and the crude oil viscosity according to the measurement result in combination with the ratio data of each experimental rock sample; and obtaining ratio data of a to-be-predicted production layer rock sample in the current oil-bearing reservoir, thereby obtaining the crude oil viscosity of the corresponding production layer by using the correlation. According to the method, the viscosity of the crude oil is rapidly predicted.

Description

Technical Field

[0001] The present invention belongs to the field of measuring the viscosity of crude oil in oil and gas exploration, and particularly relates to a method and a system for predicting the viscosity of crude oil. Background Art

[0002] The viscosity of crude oil is one of the indispensable parameters in the process of oil and gas exploration and development, and is an important factor affecting the oil well production. Timely and accurately predicting the viscosity of crude oil in the oil-bearing reservoir after drilling is beneficial to guiding the on-site production operation and the interpretation and evaluation of oil and gas layers, and can also provide a basis for the subsequent logging, casing running, and test plan formulation.

[0003] In recent years, more and more attention has been paid to the problem of how to master the viscosity of crude oil in the reservoir before casing running, so as to save operation costs and improve the exploration operation efficiency. Since it is difficult to obtain the viscosity data of crude oil in the formation with complex geological conditions and characteristics such as multiple oil layer distribution horizons and long well sections (for example: Dongying Sag) before well testing, at present, the qualitative judgment of the oil quality type mainly depends on observing samples such as cuttings and wall cores, analyzing gas logging gases and geochemical and quantitative fluorescence data. Therefore, there is an urgent need to find a method that can quickly and quantitatively predict the viscosity of crude oil. Summary of the Invention

[0004] To solve the above problems, an embodiment of the present invention provides a method for predicting the viscosity of crude oil, including: heating multiple experimental rock samples taken from an oil-bearing reservoir to obtain corresponding products and measuring the production data of the corresponding products, wherein the products include a first hydrocarbon product of light and medium components and a second hydrocarbon product of heavy components in the oil-bearing reservoir; respectively obtaining the content of light and medium components and the content of heavy components of each experimental rock sample according to the production data, and calculating the ratio of the content of light and medium components to the content of heavy components; respectively measuring the viscosity of the production oil of each production layer where the experimental rock sample is located, and establishing a correlation between the ratio and the viscosity of crude oil according to the measurement results in combination with the ratio data of each experimental rock sample; obtaining the ratio data of the rock sample of the production layer to be predicted in the current oil-bearing reservoir, so as to obtain the viscosity of the corresponding production layer by using the correlation.

[0005] Preferably, in the correlation, when the ratio data is less than 4, the established correlation between the ratio and the viscosity of crude oil is a power function relationship, wherein the independent variable of the power function is the ratio, and the dependent variable is the viscosity of crude oil; when the ratio data is greater than or equal to 4, the viscosity of crude oil is a fixed value.

[0006] Preferably, the correlation is expressed by the following expression:

[0007]

[0008] Among them, y represents the viscosity of crude oil, and x represents the ratio.

[0009] Preferably, in the step of obtaining the corresponding product, it includes: heating each experimental rock sample for the first time according to the heating condition that the heating temperature satisfies the first temperature range to obtain the first hydrocarbon product, where the first temperature range is between the initial temperature and 350°C; heating each experimental rock sample that has completed the first heating currently for the second time according to the heating condition that the heating temperature satisfies the second temperature range to obtain the second hydrocarbon product, where the second temperature range is between 350°C and 600°C.

[0010] Preferably, the first hydrocarbon product includes natural gas product, gasoline product, diesel product and kerosene product, and the second hydrocarbon product includes wax product, heavy oil product, gum product and asphaltene product. Among them, in the process of two consecutive heating processes, the programmed heating method is adopted, and the initial heating temperature is uniformly increased to the target heating temperature at a preset temperature increase rate, so as to complete the consecutive first heating and the second heating. Among them, in the process of the first heating, when the heating temperature satisfies the first temperature sub-range, the current product is used as the natural gas product for the first product extraction, where the first temperature sub-range is between the initial temperature and 90°C; when the heating temperature satisfies the second temperature sub-range, the current product is used as the gasoline product for the second product extraction, where the second temperature sub-range is between 90°C and 200°C; and when the heating temperature satisfies the third temperature sub-range, the current product is used as the diesel product and the kerosene product for the third product extraction, where the third temperature sub-range is between 200°C and 350°C; in the process of the second heating, when the heating temperature satisfies the fourth temperature sub-range, the current product is used as the wax product and the heavy oil product for the fourth product extraction, where the fourth temperature sub-range is between 350°C and 450°C; and when the heating temperature satisfies the fifth temperature sub-range, the current product is used as the gum product and the asphaltene product for the fifth product extraction, where the fifth temperature sub-range is between 450°C and 600°C.

[0011] Preferably, before heating multiple experimental rock samples taken from an oil-bearing reservoir, the method further includes: determining the oil-bearing state of each experimental rock sample, and removing the experimental rock samples with oil-bearing level fluorescence state or without oil according to the determination result, so as to obtain the corresponding product by using the remaining oil-bearing experimental rock samples, where the experimental rock samples with oil-bearing level fluorescence state or without oil are rock samples with a total oil and gas content less than 1 mg / g.

[0012] Preferably, before establishing the correlation between the ratio and the crude oil viscosity based on the measurement results and in combination with the ratio data of each experimental rock sample, the method further includes: calculating the average value and the standard deviation of the ratio of each production layer, and calculating the residual error of each ratio data by using the average value of the ratio; based on Chauvenet's criterion, performing data anomaly verification on each ratio data by using the standard deviation and the residual error, and removing the abnormal ratio data.

[0013] Preferably, in the process of measuring the production data of the corresponding product, it includes: carrying the corresponding product to a flame ionization detector by a carrier gas for concentration measurement, so as to obtain the production data of the corresponding product according to the concentration measurement result.

[0014] On the other hand, the present invention also provides a system for predicting crude oil viscosity, characterized in that the system is used to execute a method for predicting crude oil viscosity, wherein the system includes: a product collection device, which is used to heat multiple experimental rock samples taken from an oil-bearing reservoir to obtain corresponding products and measure the production data of the corresponding products, wherein the products include a first hydrocarbon product of light, medium and heavy components in the oil-bearing reservoir and a second hydrocarbon product of heavy components; a data processing device, which is used to obtain the light, medium and heavy component contents and the heavy component contents of each experimental rock sample respectively according to the production data, and calculate the ratio of the light, medium and heavy component contents to the heavy component contents; a data fitting device, which is used to measure the crude oil viscosity of the production oil of each production layer where each experimental rock sample is located respectively, and establish the correlation between the ratio and the crude oil viscosity according to the measurement results and in combination with the ratio data of each experimental rock sample; a crude oil viscosity acquisition device, which is used to acquire the ratio data of the rock sample of the production layer to be predicted in the current oil-bearing reservoir, so as to obtain the crude oil viscosity of the corresponding production layer by using the correlation.

[0015] Preferably, the product collection device includes: a first heating unit, which is used to perform a first heating on each experimental rock sample according to the heating condition that the heating temperature satisfies the first temperature range to obtain a first hydrocarbon product, wherein the first temperature range is between the initial temperature and 350 °C; a second heating unit, which is used to perform a second heating on each experimental rock sample that has completed the first heating currently according to the heating condition that the heating temperature satisfies the second temperature range to obtain a second hydrocarbon product, wherein the second temperature range is between 350 °C and 600 °C.

[0016] Compared with the prior art, one or more embodiments in the above solutions may have the following advantages or beneficial effects:

[0017] The present invention provides a method and system for predicting crude oil viscosity. This method utilizes data such as rock pyrolysis and well testing data from oil - tested exploration wells in an oil - bearing reservoir to study the quantitative relationship between rock pyrolysis - derived parameters (i.e., the light - to - heavy ratio index) and crude oil viscosity. Based on this quantitative relationship, the crude oil viscosity of the formation to be predicted is then predicted. The present invention innovatively explores a new idea for predicting the crude oil viscosity of an oil reservoir using rock pyrolysis - derived parameters, solving the problem that it is difficult to obtain crude oil viscosity data before the completion of drilling in formations with complex geological conditions, multiple oil - bearing horizons, and long well sections (e.g., Dongying Sag). It realizes the rapid prediction of crude oil viscosity and plays a guiding role in work such as oil - gas layer evaluation, logging method selection, casing program selection, and testing program formulation.

[0018] Other features and advantages of the present invention will be described in the following specification, and will, in part, be obvious from the specification, or can be learned by practicing the present invention. The objectives and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the specification, claims, and drawings. Brief Description of the Drawings

[0019] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0020] Figure 1 It is a step diagram of the method for predicting crude oil viscosity according to an embodiment of the present application.

[0021] Figure 2 It is an example diagram of the crude oil viscosity prediction model of the system for predicting crude oil viscosity according to an embodiment of the present application.

[0022] Figure 3 It is a block diagram of the system for predicting crude oil viscosity according to an embodiment of the present application. Detailed Embodiments

[0023] The following will detail the embodiments of the present invention in conjunction with the drawings and embodiments, so as to fully understand how the present invention uses technical means to solve technical problems and achieve the realization process of technical effects and implement accordingly. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0024] In addition, the steps shown in the flowchart of the drawings can be executed in a computer system such as a set of computer - executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0025] Crude oil viscosity is one of the indispensable parameters in the process of oil and gas exploration and development. It is an important factor affecting the oil well production. Timely and accurately predicting the crude oil viscosity of the oil-bearing reservoir after well completion is conducive to guiding the on-site production operation and the interpretation and evaluation of oil and gas layers, and can also provide a basis for the subsequent logging, casing running, and test plan formulation.

[0026] In recent years, more and more attention has been paid to the problem of how to master the crude oil viscosity of the reservoir before casing running, so as to save operation costs and improve the exploration operation efficiency. Since it is difficult to obtain the crude oil viscosity data of the formation with complex geological conditions, many oil layer distribution horizons, and long well sections (such as Dongying Sag) before well testing, at present, the qualitative judgment of the oil quality type mainly depends on observing samples such as cuttings and wall cores, analyzing gas logging gases and geochemical and quantitative fluorescence data. Therefore, there is an urgent need to find a method that can quickly and quantitatively predict the crude oil viscosity.

[0027] Therefore, to solve the above problems, the embodiments of the present invention propose a method and system for predicting crude oil viscosity. This method uses data such as rock pyrolysis and well testing data of the well-tested exploration wells in the oil-bearing reservoir to study the quantitative relationship between the rock pyrolysis-derived parameter (i.e., the light-to-heavy ratio index) and the crude oil viscosity, and then predicts the crude oil viscosity of the formation to be predicted based on this quantitative relationship. The present invention innovatively explores a new idea for predicting the crude oil viscosity of the oil layer using rock pyrolysis-derived parameters, solves the problem of difficult access to crude oil viscosity data in the formation with complex geological conditions, many oil layer distribution horizons, and long well sections (such as Dongying Sag) before well completion discussion, realizes the rapid prediction of crude oil viscosity, and plays a guiding role in the work of oil and gas layer interpretation and evaluation, logging method selection, casing running plan selection, and test plan formulation.

[0028] Example 1

[0029] The chemical composition of crude oil is the internal cause determining the viscosity level and the main influencing factor of crude oil viscosity. Generally speaking, the larger the molecular weight of crude oil, the higher the viscosity. Among them, the content of heavy components such as macromolecular compounds (such as resins and asphaltenes) has a significant impact on the crude oil viscosity, which will cause an increase in the internal friction of the crude oil liquid layer molecules, thereby increasing the crude oil viscosity, while the increase in light and medium components will reduce the crude oil viscosity. In addition, the crude oil viscosity is also affected by external factors such as temperature and pressure. Under the condition of controlling the external factors to make the temperature and pressure constant, accurately measuring the content of each component in crude oil can make the rapid prediction of crude oil viscosity possible.

[0030] The rock pyrolysis technology has the ability to quantitatively detect the absolute content of each hydrocarbon component in rock samples, and its derived parameter (i.e., the light-to-heavy ratio index) can well reflect the properties of crude oil. Therefore, in this embodiment, the rock pyrolysis technology is used to obtain the rock pyrolysis derived parameter, providing technical support for the prediction of crude oil viscosity.

[0031] Figure 1 It is a step diagram of the method for predicting crude oil viscosity in the embodiment of the present application. The following refers to Figure 1 to illustrate each step of this method.

[0032] As Figure 1 shown, in step S110, multiple experimental rock samples taken from an oil-bearing reservoir are heated to obtain corresponding products and measure the production data of the corresponding products. Since the rock pyrolysis technology can measure the absolute content of thermally evaporated and pyrolyzed hydrocarbons in rocks, in this embodiment, multiple experimental rock samples taken from an oil-bearing reservoir are heated, so that the hydrocarbons and kerogen in each experimental rock sample volatilize and crack at different temperatures. Finally, by collecting and measuring the hydrocarbon products related to volatilization and cracking, the corresponding products and the production data of the corresponding products are obtained. In practical applications, the composition of crude oil includes light, medium and heavy components. Therefore, the products in this embodiment include the first hydrocarbon product of light and medium components and the second hydrocarbon product of heavy components in the oil-bearing reservoir.

[0033] In the step of obtaining the corresponding products, the present invention first heats each experimental rock sample for the first time according to the heating condition that the heating temperature satisfies the first temperature range to obtain the first hydrocarbon product, where the first temperature range is between the initial temperature and 350°C; then, according to the heating condition that the heating temperature satisfies the second temperature range, each experimental rock sample that has completed the first heating is heated for the second time to obtain the second hydrocarbon product, where the second temperature range is between 350°C and 600°C.

[0034] In practical applications, the demarcation temperature at which heating a rock sample causes thermal evaporation and thermal cracking of different types of components (light, medium, and heavy components) in crude oil is 350°C. That is to say, in the products obtained before the heating temperature of the experimental rock sample reaches 350°C, only the hydrocarbon products of light and medium components (i.e., the first hydrocarbon products) are included. When the heating temperature reaches 350°C, all the hydrocarbon products of the light and medium components in the experimental rock sample have been collected. At this time, the products obtained by continuing to heat the experimental rock sample only include the hydrocarbon products of heavy components (i.e., the second hydrocarbon products). Moreover, the completion node of the thermal evaporation and thermal cracking of the experimental rock sample occurs when the heating temperature reaches 600°C. Therefore, in this embodiment, the heating conditions that satisfy the first temperature range are used as the heating conditions for obtaining the first hydrocarbon products. First, according to the heating conditions where the heating temperature is greater than the initial temperature and less than 350°C, each core experimental rock sample is heated for the first time respectively, so as to collect the first hydrocarbon products of each experimental rock sample. Then, the heating conditions that satisfy the second temperature range are used as the heating conditions for obtaining the second hydrocarbon products. According to the heating conditions where the heating temperature is greater than 350°C and less than 600°C, each experimental rock sample that has completed the first heating and the collection of the first hydrocarbon products is continuously heated for the second time, so as to collect the second hydrocarbon products of each experimental rock sample. Accordingly, based on two consecutive heatings, the present invention achieves the purpose of collecting the first hydrocarbon products and the second hydrocarbon products of each experimental rock sample.

[0035] In a specific embodiment of the present application, the first hydrocarbon products include natural gas products, gasoline products, diesel products, and kerosene products, and the second hydrocarbon products include wax products, heavy oil products, gum products, and asphaltene products.

[0036] During the two consecutive heating processes, the programmed temperature rise method is adopted, and the initial heating temperature is uniformly raised to the target heating temperature at a preset temperature rise rate, so as to complete the consecutive first heating and second heating. The first heating process of the experimental rock sample in this embodiment is a continuous process, and moreover, the second heating process is also a continuous process. Accordingly, this embodiment also forms an overall continuous heating process (including the complete first heating process and the complete second heating process) that directly switches from the first heating process to the second heating process based on the demarcation temperature for generating the first hydrocarbon products and the second hydrocarbon products.

[0037] Specifically, in this embodiment, a preset temperature increase rate is set for the overall continuous heating process, and then the heating temperature is steadily increased according to the preset temperature increase rate, so as to uniformly increase the initial heating temperature (i.e., the initial temperature at the start of the first heating process or the initial temperature at the start of the overall continuous heating process) to the target heating temperature (i.e., the heating temperature at the end of the second heating or the heating temperature at the end of the continuous heating process). Thus, the present invention ensures the stability of the overall continuous heating process and effectively improves the production efficiency of the output product. It should be noted that the present invention does not specifically limit the preset temperature increase rate, and those skilled in the art can set it according to the actual heating conditions required.

[0038] Next, during the first heating process, when the heating temperature satisfies the first temperature sub-interval, the current output product is extracted as the natural gas output product for the first time, where the first temperature sub-interval is between the initial temperature and 90°C; when the heating temperature satisfies the second temperature sub-interval, the current output product is extracted as the gasoline output product for the second time, where the second temperature sub-interval is between 90°C and 200°C; and when the heating temperature satisfies the third temperature sub-interval, the current output product is extracted as the diesel output product and the kerosene output product for the third time, where the third temperature sub-interval is between 200°C and 350°C. Then, during the second heating process, when the heating temperature satisfies the fourth temperature sub-interval, the current output product is extracted as the wax output product and the heavy oil output product for the fourth time, where the fourth temperature sub-interval is between 350°C and 450°C; and when the heating temperature satisfies the fifth temperature sub-interval, the current output product is extracted as the gum output product and the asphaltene output product for the fifth time, where the fifth temperature sub-interval is between 450°C and 600°C.

[0039] In this embodiment, each experimental rock sample is placed separately in a specially designed pyrolysis furnace that is airtight and has heating capacity for individual heating, so as to extract the output products belonging to each experimental rock sample. Based on the characteristics that different output products are obtained from experimental rock samples at different heating temperatures, during the process of steadily increasing the heating temperature, the critical temperatures for generating different output products are designated as the extraction nodes for the corresponding types of output products.

[0040] During the first heating process of this embodiment, 90°C is taken as the critical temperature when the natural gas output is completed, 200°C is taken as the critical temperature when the gasoline output is completed, and 300°C is taken as the critical temperature when the diesel output and kerosene output are completed. At this time, this embodiment takes 90°C as the extraction node of the first output. When the heating temperature is 90°C, the output during the process of the heating temperature rising from the initial temperature to 90°C is extracted as the first output, thereby obtaining the natural gas output; 200°C is taken as the extraction node of the second output. When the heating temperature is 200°C, the output during the process of the heating temperature rising from 90°C to 200°C is extracted as the second output, thereby obtaining the gasoline output; and 350°C is taken as the extraction node of the third output. When the heating temperature is 350°C, the output during the process of the heating temperature rising from 200°C to 350°C is extracted as the third output, thereby obtaining the diesel output and kerosene output.

[0041] During the second heating process of this embodiment, 450°C is taken as the critical temperature when the wax output and heavy oil output are completed, and 600°C is taken as the critical temperature when the gum output and asphaltene output are completed. At this time, this embodiment takes 450°C as the extraction node of the fourth output. When the heating temperature is 450°C, the output during the process of the heating temperature rising from the initial temperature of 350°C to 450°C is extracted as the fourth output, thereby obtaining the wax output and heavy oil output; 600°C is taken as the extraction node of the fifth output. When the heating temperature is 600°C, the output during the process of the heating temperature rising from 450°C to 600°C is extracted as the fifth output, thereby obtaining the gum output and asphaltene output.

[0042] During the process of measuring the yield data of the corresponding output, the present invention carries the corresponding output to a hydrogen flame ionization detector by a carrier gas for concentration measurement, so as to obtain the yield data of the corresponding output according to the concentration measurement result. In the embodiment of the present application, when reaching the extraction node of each output, the output at the corresponding time node is transported by a carrier gas, so that the corresponding output is carried to a hydrogen flame ionization detector (FID) by the carrier gas for concentration measurement. Then, the measured concentration data is converted into a corresponding current signal for data transmission. Finally, the current signal carrying the concentration data is subjected to arithmetic processing by a microcomputer to obtain the yield data of each generated output, so as to generate a chromatographic peak area representing the content of the components to which each generated output belongs according to the yield data of each generated output.

[0043] Further, in step S120, the light and medium component content and the heavy component content of each experimental rock sample are obtained according to the production data, and the ratio of the light and medium component content to the heavy component content is calculated. Specifically, first, according to the production data under different heating temperature conditions, the content of the components of the natural gas output, the content of the components of the gasoline output, the content of the components of the diesel output and the kerosene output in the light and medium components, and the content of the components of the wax output and the heavy oil output, the content of the components of the colloid output and the asphaltene output in the heavy components are calculated respectively. Then, the light and medium component content is obtained by calculating the sum of the content of the components of the natural gas output, the content of the components of the gasoline output, the content of the components of the diesel output and the kerosene output, and the heavy component content is obtained by calculating the sum of the content of the components of the wax output and the heavy oil output, the content of the colloid output and the asphaltene output. Finally, the ratio of the light and medium components to the heavy components is calculated using the following expression, and this ratio is used as a derived parameter (i.e., light-heavy ratio index) to reflect the properties of crude oil:

[0044]

[0045] Wherein, Ps represents the ratio, S 0 represents the chromatographic peak area of ​​the components of the natural gas output, S 1 represents the chromatographic peak area of ​​the components of the gasoline output, S 21 represents the chromatographic peak area of ​​the components of diesel output and kerosene output, S 22 represents the chromatographic peak area of ​​the components of wax output and heavy oil output, S 23 Indicates the chromatographic peak area of ​​the components of the colloid output and asphaltene output.

[0046] Before heating multiple experimental rock samples taken from an oil-bearing reservoir, the present invention determines the oil-bearing state of each experimental rock sample, and removes the experimental rock samples with oil-bearing grade fluorescence state and no oil according to the determination result, so as to obtain the corresponding output using the remaining oil-bearing experimental rock samples, wherein the experimental rock samples with oil-bearing grade fluorescence state and no oil are rock samples with a total oil and gas content of less than 1 mg / g. In the embodiment of the present application, firstly, by retrieving the lithology description record of each experimental rock sample, the oil-bearing state of each experimental rock sample is determined, so as to eliminate the oil-bearing grade fluorescence (i.e., less oil content) and oil-free sample rock samples in the experimental rock samples according to the oil-bearing grade discrimination standard of rock pyrolysis reservoir rock. In this way, the corresponding output obtained from the remaining oil-containing experimental rock samples is used to establish the correlation between the ratio and the crude oil viscosity, which effectively avoids the interference of the ratio data of the oil-containing grade fluorescence (i.e., low oil content) and the oil-free sample rock samples on the correlation between the fitted ratio and the crude oil viscosity. Ultimately, the prediction of crude oil viscosity based on the currently established correlation is more consistent with the actual situation.​

[0047] Before establishing the correlation between the ratio and the crude oil viscosity based on the measurement results and combining the ratio data of each experimental rock sample, the present invention first calculates the average value and standard deviation of the ratio for each production layer, and uses the average value of the ratio to calculate the residual error of each ratio data respectively; then, based on Chauvenet's criterion, the standard deviation and the residual error are used to perform data anomaly verification on each ratio data, and the abnormal ratio data are excluded.

[0048] In practical applications, a production layer often corresponds to rock pyrolysis data of wall cores and cores at multiple different depths. However, in the process of establishing the correlation between the ratio and the crude oil viscosity, it can only be "one-to-one", that is: the crude oil viscosity of one production layer corresponds to one ratio. Therefore, before establishing the correlation between the ratio and the crude oil viscosity in this embodiment, the ratio data is preprocessed to meet the needs of subsequent establishment of the correlation between the ratio and the crude oil viscosity. First, the average value of the ratio data belonging to the same production layer is taken and the standard deviation is calculated. After obtaining the average value of the ratio data, the residual error of each ratio data is calculated respectively using the average value of the ratio. Then, based on Chauvenet's criterion, the standard deviation and the residual error are used to perform data anomaly verification on each ratio data, and the ratio data corresponding to the residual error whose absolute value is greater than or equal to the product of Chauvenet's criterion number and the aforementioned standard deviation is taken as the abnormal ratio data and excluded. Finally, the average value of the remaining ratio data belonging to the same production layer is taken again, so that the current new average value of the ratio is used as the ratio data of this production layer.

[0049] In a specific embodiment of the present application, the residual error is calculated using the following expression:

[0050]

[0051] where v i represents the error of the i-th ratio data, x i represents the i-th ratio data, represents the average value of the ratio data.

[0052] Further, in step S130, the crude oil viscosity of the production oil in the pay zone where each experimental rock sample is located is measured respectively. According to the measurement results and combined with the ratio data of each experimental rock sample, the correlation between the ratio and the crude oil viscosity is established. In actual crude oil, the increase in the content of heavy components and the decrease in the content of light components will lead to an increase in the crude oil viscosity. At this time, the ratio will decrease. Therefore, theoretically, there is a negative correlation between the crude oil viscosity and the ratio. In the embodiment of the present application, the conventional crude oil viscosity measurement method is used to measure the crude oil viscosity of the production oil in the pay zone where each experimental rock sample is located respectively, and then the correlation between the ratio and the crude oil viscosity is fitted, so as to obtain the linear correlation between the ratio and the crude oil viscosity, so as to achieve the purpose of establishing the correlation between the ratio and the crude oil viscosity.

[0053] In the embodiment of the present application, when the ratio data is less than 4, the established correlation between the ratio and the crude oil viscosity is a power function relationship, where the independent variable of the power function is the ratio and the dependent variable is the crude oil viscosity; when the ratio data is greater than or equal to 4, the crude oil viscosity is a fixed value. Specifically, when the ratio x≥4, the crude oil viscosity is randomly distributed in the interval [2, 10], that is, it no longer follows the function curve distribution. Therefore, when x≥4, it is more reasonable to take the median 6 of the interval [2, 10] as the fixed value of the crude oil viscosity.

[0054] In a specific embodiment of the present application, the correlation is expressed by the following expression:

[0055]

[0056] Among them, y represents the crude oil viscosity and x represents the ratio.

[0057] Further, in step S140, the ratio data of the rock sample of the pay zone to be predicted in the current oil-bearing reservoir is obtained, so as to obtain the crude oil viscosity of the corresponding pay zone by using the correlation. Specifically, after establishing the correlation between the ratio and the crude oil viscosity, this embodiment uses the established correlation as the Figure 2 shown oil-bearing reservoir crude oil viscosity prediction model. Combining the ratio data of the rock sample of the pay zone to be predicted in the current oil-bearing reservoir, the crude oil viscosity of the corresponding pay zone can be obtained ( Figure 2 is an example diagram of the crude oil viscosity prediction model of the system for predicting crude oil viscosity in the embodiment of the present application). Among them, the rock sample of the pay zone to be predicted is a rock sample that is in the same oil-bearing reservoir as the experimental rock sample and does not belong to the same pay zone.

[0058] In a specific embodiment of the present application, detailed data statistics were carried out in the Dongying Sag, and the ratio data of crude oil viscosity (50°C test viscosity) and corresponding production layers of the wells tested in the Dongying Sag from 2001 to 2020 were obtained. Among them, a total of 402 oil layers in 290 exploration wells in 15 well areas in the Dongying Sag were counted, and 2334 ratios (i.e., light-heavy ratios) were obtained as shown in Table 1.

[0059] Table 1 Statistics of light-heavy ratio

[0060]

[0061]

[0062] After removing the abnormal ratio data, the Dongying Sag oil reservoir weight-weight ratio-crude oil viscosity data, which is composed of the data preprocessing ratio data (i.e., weight-weight ratio) and crude oil viscosity data, is obtained as shown in Table 2.

[0063] Table 2 Light-to-heavy ratio-crude oil viscosity data table

[0064]

[0065] Next, import all the light-heavy ratio-crude oil viscosity data into the data processing software to create a scatter plot. The light-heavy ratio is used as the horizontal coordinate, and a linear scale is used, with the scale range between 0 and 7; the crude oil viscosity is used as the vertical coordinate, and a linear scale is used, with the scale range between 1 and 10000. Afterwards, using the data points in the coordinates, different types of regression calculations such as linear function, exponential function, logarithmic function, power function, and polynomial are performed. By comparison, it is finally found that the power function has the best match with the data distribution characteristics of this embodiment. The correlation between the ratio and crude oil viscosity is preliminarily obtained through derivation calculation:

[0066] y=1016x -4.09 (4)

[0067] Furthermore, by statistically testing the regression equation of the correlation between the ratio and crude oil viscosity obtained initially and correcting the current correlation, the correlation between the ratio and crude oil viscosity consistent with formula (3) was obtained. Among them, the statistical test methods include but are not limited to goodness of fit test, significance test, and outlier test. The goodness of fit R 2 =0.861, which further proves the rationality of the correlation between the ratio and crude oil viscosity established in this example.

[0068] In a specific embodiment of the present application, the established correlation between the ratio and the crude oil viscosity is used to predict the crude oil viscosity of 36 oil layers in 33 exploration wells in different well areas of Dongying Sag from 2021 to 2022. The ratio (i.e., the light-to-heavy ratio) data corresponding to the depth of each oil layer is obtained through rock pyrolysis instrument testing and calculation, and the average value is taken after abnormal data elimination processing, and then substituted into the established correlation between the ratio and the crude oil viscosity, and a comparison data table of the predicted crude oil viscosity and the actual crude oil viscosity as shown in Table 3 is obtained.

[0069] Table 3 Comparison data table of predicted crude oil viscosity and actual crude oil viscosity

[0070]

[0071]

[0072] By referring to the ground crude oil viscosity classification standard as shown in Table 4, the prediction qualification rate of the oil quality type is calculated. The calculation results show that among the 36 oil layers, except for the 5th, 15th, and 18th layers, the predicted viscosities of the remaining 33 layers meet the standard, that is, the prediction qualification rate reaches 92%.

[0073] Table 4 Crude oil viscosity classification standard

[0074] Crude oil viscosity (mPa·s) Type ＜10 Low-viscosity crude oil 10-100 Medium-viscosity crude oil 100-1000 High-viscosity crude oil 1000-10000 Extra-heavy oil ＞10000 Ultra-heavy oil

[0075] Example 2

[0076] Based on the method for predicting crude oil viscosity described in the above-mentioned Embodiment 1, the embodiment of the present invention also provides a system for predicting crude oil viscosity. Figure 3 It is a module block diagram of the system for predicting crude oil viscosity in the embodiment of the present application.

[0077] Such as Figure 3As shown in the figure, the system for predicting crude oil viscosity in the embodiments of the present invention includes: a product collection device 31, a data processing device 32, a data fitting device 33, and a crude oil viscosity acquisition device 34. The product collection device 31 is implemented according to the method described in step S110 above, and is configured to heat multiple experimental rock samples taken from an oil-bearing reservoir, obtain corresponding products, and measure the production data of the corresponding products. Among them, the products include a first hydrocarbon product of light, medium, and heavy components in the oil-bearing reservoir and a second hydrocarbon product of heavy components; the data processing device 32 is implemented according to the method described in step S120 above, and is configured to obtain the content of light, medium, and heavy components and the content of heavy components of each experimental rock sample based on the production data, and calculate the ratio of the content of light, medium, and heavy components to the content of heavy components; the data fitting device 33 is implemented according to the method described in step S130 above, and is configured to measure the crude oil viscosity of the production oil in the production layer where each experimental rock sample is located respectively, and based on the measurement results, combined with the ratio data of each experimental rock sample, establish a correlation between the ratio and the crude oil viscosity; the crude oil viscosity acquisition device 34 is implemented according to the method described in step S140 above, and is configured to obtain the ratio data of the rock sample of the production layer to be predicted in the current oil-bearing reservoir, so as to obtain the crude oil viscosity of the corresponding production layer by using the correlation.

[0078] Further, the product collection device 31 of the present invention includes a first heating unit 311 and a second heating unit 312. The first heating unit 311 is used to perform a first heating on each experimental rock sample according to the heating condition that the heating temperature satisfies the first temperature range, and obtain a first hydrocarbon product, where the first temperature range is between the initial temperature and 350 °C. The second heating unit 312 is used to perform a second heating on each experimental rock sample that has completed the first heating currently according to the heating condition that the heating temperature satisfies the second temperature range, and obtain a second hydrocarbon product, where the second temperature range is between 350 °C and 600 °C.

[0079] The present invention discloses a method and system for predicting crude oil viscosity. This method uses data such as rock pyrolysis and well testing data of the well that has been tested for oil in the oil-bearing reservoir to study the quantitative relationship between the rock pyrolysis-derived parameter (i.e., the light-to-heavy ratio index) and the crude oil viscosity, so as to predict the crude oil viscosity of the production layer to be predicted based on this quantitative relationship. The present invention innovatively explores a new idea for predicting the crude oil viscosity of the oil layer using the rock pyrolysis-derived parameter, solves the problem that it is difficult to obtain crude oil viscosity data before the completion of drilling in formations with complex geological conditions and characteristics such as multiple oil layer distribution horizons and long well sections (for example: Dongying Sag), realizes the rapid prediction of crude oil viscosity, and plays a guiding role in work such as oil and gas layer evaluation, logging method selection, casing program selection, and test program formulation.

[0080] As described above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

[0081] Certainly, the present invention may also have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

[0082] Those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general-purpose computing device. They can be concentrated on a single computing device or distributed on a network composed of multiple computing devices. Optionally, they can be implemented by program codes executable by the computing device, so that they can be stored in a storage device and executed by the computing device, or they can be separately fabricated into individual integrated circuit modules, or multiple modules or steps among them can be fabricated into a single integrated circuit module to be implemented. In this way, the present invention is not limited to any specific combination of hardware and software.

[0083] Although the disclosed embodiments of the present invention are as above, the described content is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains can make any modifications and changes in the form of implementation and details without departing from the spirit and scope disclosed by the present invention. However, the patent protection scope of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for predicting crude oil viscosity, characterized in that: include: Heating a plurality of experimental rock samples taken from an oil-bearing reservoir to obtain corresponding outputs and measure the production data of the corresponding outputs, wherein the outputs include a first hydrocarbon output of a light and medium component and a second hydrocarbon output of a heavy component in the oil-bearing reservoir; According to the production data, the light and medium component content and the heavy component content of each experimental rock sample are obtained respectively, and the ratio of the light and medium component content to the heavy component content is calculated; The produced oil of the production layer where each experimental rock sample is located is measured for crude oil viscosity, and based on the measurement results and the ratio data of each experimental rock sample, the correlation between the ratio and crude oil viscosity is established; The ratio data of the rock sample of the production layer to be predicted in the current oil-bearing reservoir is obtained, so as to obtain the viscosity of the crude oil of the corresponding production layer by using the correlation relationship.

2. The method according to claim 1, characterized in that: In the above correlation, When the ratio data is less than 4, the established correlation between the ratio and the crude oil viscosity is a power function relationship, wherein the independent variable of the power function is the ratio and the dependent variable is the crude oil viscosity; When the ratio data is greater than or equal to 4, the crude oil viscosity is a fixed value.

3. The method according to claim 2, characterized in that The correlation is expressed by the following expression: Among them, y represents the viscosity of crude oil and x represents the ratio.

4. The method according to any one of claims 1 to 3, characterized in that The steps of obtaining the corresponding output include: According to the heating condition that the heating temperature satisfies the first temperature range, each experimental rock sample is heated for the first time to obtain a first hydrocarbon output, wherein the first temperature range is between the initial temperature and 350° C.; According to the heating temperature satisfying the heating condition of the second temperature range, each experimental rock sample that has completed the first heating is heated for the second time to obtain a second hydrocarbon output, wherein the second temperature range is between 350°C and 600°C.

5. The method according to claim 4, characterized in that The first hydrocarbon output includes natural gas output, gasoline output, diesel output and kerosene output, and the second hydrocarbon output includes wax output, heavy oil output, colloid output and asphaltene output, wherein, In the two consecutive heating processes, a programmed temperature increase method is used to uniformly increase the initial heating temperature to the target heating temperature according to a preset temperature increase rate, thereby completing the consecutive first heating and the second heating, wherein: During the first heating process, when the heating temperature satisfies a first temperature sub-interval, the current output is used as the natural gas output for first output extraction, wherein the first temperature sub-interval is between the initial temperature and 90° C.; When the heating temperature satisfies a second temperature sub-interval, extracting the current output as the gasoline output for the second time, wherein the second temperature sub-interval is between 90° C. and 200° C.; and When the heating temperature satisfies the third temperature sub-interval, the current output is used as the diesel output and the kerosene output for a third output extraction, wherein the third temperature sub-interval is between 200° C. and 350° C.; During the second heating, when the heating temperature satisfies a fourth temperature sub-interval, the current output is used as the wax output and the heavy oil output for fourth output extraction, wherein the fourth temperature sub-interval is between 350° C. and 450° C.; and When the heating temperature satisfies the fifth temperature sub-interval, the current output is used as the resin output and the asphaltene output for the fifth output extraction, wherein the fifth temperature sub-interval is between 450°C and 600°C.

6. The method according to any one of claims 1 to 5, characterized in that: Prior to heating the plurality of experimental rock samples taken from the oil-bearing reservoir, the method further comprises: The oil-bearing status of each experimental rock sample is determined, and based on the determination result, the experimental rock samples with oil-bearing grade fluorescent status or without oil are removed, so as to obtain the corresponding output using the remaining oil-bearing experimental rock samples, wherein the experimental rock samples with oil-bearing grade fluorescent status or without oil are rock samples with a total oil and gas content of less than 1 mg / g.

7. The method according to any one of claims 1 to 6, characterized in that: Before establishing the correlation between the ratio and the crude oil viscosity based on the measurement results and in combination with the ratio data of each experimental rock sample, the method further includes: Calculate the ratio mean and standard deviation of each production layer, and use the ratio mean to calculate the residual error of each ratio data; Based on the Chauville criterion, each ratio data is checked for data anomaly using the standard deviation and the residual error, and abnormal ratio data are eliminated.

8. The method according to any one of claims 1 to 7, characterized in that: The process of measuring the output data of the corresponding output includes: The corresponding output is carried to a hydrogen flame ionization detector via a carrier gas for concentration measurement, so as to obtain the yield data of the corresponding output according to the concentration measurement result.

9. A system for predicting crude oil viscosity, characterized in that: The system is used to perform the method according to any one of claims 1 to 8, wherein the system comprises: A product collection device, which is used to heat a plurality of experimental rock samples taken from an oil-bearing reservoir to obtain corresponding outputs and measure the production data of the corresponding outputs, wherein the outputs include a first hydrocarbon output of a light and medium component and a second hydrocarbon output of a heavy component in the oil-bearing reservoir; A data processing device, which is used to obtain the light and medium component content and the heavy component content of each experimental rock sample according to the production data, and calculate the ratio of the light and medium component content to the heavy component content; A data fitting device is used to measure the crude oil viscosity of the produced oil in the production layer where each experimental rock sample is located, and establish a correlation between the ratio and the crude oil viscosity based on the measurement results and the ratio data of each experimental rock sample; The crude oil viscosity acquisition device is used to acquire the ratio data of the rock sample of the production layer to be predicted in the current oil-bearing reservoir, so as to obtain the crude oil viscosity of the corresponding production layer by utilizing the correlation.

10. The crude oil viscosity calculation system according to claim 9, characterized in that: The product collecting device comprises: A first heating unit, which is used to heat each experimental rock sample for the first time according to the heating temperature satisfying the heating condition of the first temperature range to obtain the first hydrocarbon output, wherein the first temperature range is between the initial temperature and 350° C.; The second heating unit is used to heat each experimental rock sample that has completed the first heating for a second time according to the heating temperature meeting the heating conditions of the second temperature range, so as to obtain a second hydrocarbon output. The second temperature range is between 350°C and 600°C.

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