A method for evaluating shale oil reservoir resources

Abstract

The present invention discloses a method for evaluating shale oil reservoir resources, the method comprising: generating first eigenvalues ​​and second eigenvalues ​​corresponding to each order of thermal evolution degree by testing the step-by-step pyrolysis parameters and organic matter abundance of shale samples at different thermal evolution degrees, thereby constructing a multi-level reservoir resource evaluation model, wherein the level boundary value of each level of the evaluation model is the first eigenvalue and second eigenvalue corresponding to the corresponding evolution degree level; using the multi-level reservoir resource evaluation model, the reservoir resource level of the shale to be analyzed is evaluated. The present invention characterizes the resource quality of shale oil reservoirs from two dimensions: geochemical characteristics and oil and gas mobility.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil reservoir exploration and development, and in particular to a method for evaluating shale oil reservoir resources. Background Art

[0002] Compared with conventional oil and gas, shale oil has the characteristics of short migration distance, small oil and gas loss, and great resource potential, and is a key area of ​​future oil and gas exploration. Since my country's shale oil producing layers are mainly continental sedimentary environments, strong heterogeneity is an unavoidable problem in oil and gas exploration. Therefore, clarifying the resource quality of shale oil reservoirs plays an important role in shale oil exploration.

[0003] At present, the resource quality of shale oil reservoirs is evaluated mainly from two aspects: shale oil mobility and geochemical characterization. From the perspective of mobility evaluation, there are two types of oil in shale: 1. Free oil in pores and cracks. This part of oil and gas often has good development potential and is considered to be movable oil; 2. Adsorbed oil in kerogen and on the surface of minerals. Under the conditions of fracturing development, this part of oil is still difficult to be developed and is considered to be immobile oil. Characterization of geochemical characteristics is another evaluation method. Different geochemical characteristics correspond to different resource potentials.

[0004] The existing technology has proposed many evaluation standards and models for the mobility and geochemical characterization of shale oil, including: First, beyond the effect limit is to evaluate the resource quality of shale oil reservoirs from the perspective of oil and gas mobility. By proposing a new evaluation parameter: hydrocarbon index OSI (S1 / TOC×100)>100mg / g TOC, it is believed that shale oil with OSI greater than 100 has industrial mining value. Although this method is simple and easy, when the resource quality is divided from the perspective of mobility alone, due to the low TOC of some strata, the OSI value may be abnormally high, resulting in inaccurate resource rating; second, based on geochemical characteristics, namely total organic matter content (TOC) and oil content index (S1 and asphalt "A"), the oil content of shale is divided into three levels by statistical methods. This method simply considers the geochemical characteristics of shale, but does not consider the mobility of shale oil, and cannot further clarify the industrially favorable sweet spot; third, a four-division method for shale oil resources is proposed, and a Resource evaluation model, which takes the shale oil mobility boundary value as the constraint value for classifying the resource quality of shale reservoirs. However, in the actual evolution of shale, the absorption capacity of hydrocarbons in shale will gradually change, which also means that the oil and gas mobility of shale at different thermal evolution maturity is not the same. Therefore, using a fixed oil and gas mobility boundary value as the constraint of the model may cause misjudgment of resource quality classification; Fourthly, the parameters characterizing thermal evolution maturity are introduced as independent variables for constructing resource quality rating, and a three-dimensional model for shale reservoir resource quality rating is constructed. Specifically, the hydrocarbon index OSI value is calculated based on the pyrolysis and TOC abundance data, and the OSI value and TOC are fitted according to the data model. max The relationship between the OSI value and the shale hydrocarbon expulsion threshold (HET) is established, and the OSI value at and after HET is taken as the oil and gas mobility boundary value OMT. However, this method is mainly used in conventional pyrolysis tests.

[0005] Although conventional pyrolysis data has been widely used in the oil industry, with the deepening of understanding of the storage mechanism of oil in different states in shale, more and more scholars have realized that conventional pyrolysis has two shortcomings: 1. The conventional pyrolysis parameter S1 (free hydrocarbon) does not represent the amount of oil generated in the shale, and therefore cannot accurately characterize the oil content of the shale; 2. Conventional pyrolysis cannot clearly determine the content of oil in different states in the shale, and cannot accurately characterize the mobility of shale oil. Therefore, the accuracy of the model still needs to be further improved.

[0006] Therefore, the prior art needs to provide a solution that can more accurately evaluate the quality of shale oil reservoir resources to solve the above-mentioned problem of shale oil movable oil identification, thereby providing corresponding technical support for shale oil resource evaluation and exploration and development. Summary of the invention

[0007] In order to solve the above technical problems, an embodiment of the present invention provides a method for evaluating shale oil reservoir resources, the method comprising: step 1, by testing the step-by-step pyrolysis parameters and organic matter abundance corresponding to shale samples at different thermal evolution degrees, generating first eigenvalues ​​and second eigenvalues ​​corresponding to each order of thermal evolution degree; step 2, according to the first eigenvalues ​​and second eigenvalues ​​corresponding to each order of thermal evolution degree, constructing a multi-level reservoir resource evaluation model, wherein the level boundary value of each level of the evaluation model is the first eigenvalue and second eigenvalue corresponding to the corresponding evolution degree level; step 3, using the multi-level reservoir resource evaluation model to evaluate the reservoir resource level of the shale to be analyzed.

[0008] Preferably, the first eigenvalue is S 2-1 The second characteristic value is the ratio of the specified sum value to the organic matter abundance, wherein the specified sum value is S 1-2 Value and S 2-1 The sum of values.

[0009] Preferably, the step 2 includes: calculating the total oil content at different degrees of thermal evolution obtained based on the step-by-step pyrolysis test according to the first eigenvalue and the second eigenvalue at different degrees of thermal evolution; using the organic matter abundance and the total oil content as the horizontal and vertical coordinates, respectively constructing single temperature step evaluation models at different degrees of thermal evolution; coupling the first eigenvalue and the second eigenvalue at different degrees of thermal evolution to the corresponding single temperature step evaluation model; and establishing the multi-level reservoir resource evaluation model by superimposing the single temperature step evaluation models of multiple degrees of thermal evolution.

[0010] Preferably, the step 2 further includes: processing the first eigenvalue and the second eigenvalue corresponding to the thermal evolution degree of each order, wherein, according to the first eigenvalue corresponding to each thermal evolution degree, a first expression characterizing the correlation between the first eigenvalue and the thermal evolution degree is formed, and according to the second eigenvalue corresponding to each thermal evolution degree, a second expression characterizing the correlation between the second eigenvalue and the thermal evolution degree is formed, so as to construct the multi-level reservoir resource evaluation model by using the eigenvalues ​​indicated in the first expression and the second expression for the corresponding thermal evolution degree.

[0011] Preferably, the reservoir quality evaluation grade of the shale to be analyzed is divided into invalid resources, inefficient resources, potential resources and enriched resources using the invalid resource boundary value and the dynamic first characteristic value and the dynamic second characteristic value that change with the degree of thermal evolution.

[0012] Preferably, the first expression and the second expression are fitted using the following expression:

[0013]

[0014] Where i represents the eigenvalue number, Mi represents the first eigenvalue or the second eigenvalue calculated based on the measured value of the step-by-step pyrolysis test, and β represents the maximum S 2-1 The degree of thermal evolution corresponding to the value, T max It represents the temperature corresponding to each level of thermal evolution, and μ and θ represent the morphological parameters respectively.

[0015] Preferably, in step three, it includes: performing step-by-step pyrolysis test and organic matter abundance test on the shale sample to be analyzed, calculating the actual step-by-step pyrolysis parameters and actual abundance corresponding to the current actual evolution degree, and based on this, using the multi-level reservoir resource evaluation model to obtain the reservoir quality grade of the current shale sample to be analyzed.

[0016] Preferably, the method further comprises: calculating the actual total oil content according to the step-by-step pyrolysis parameters obtained from the step-by-step pyrolysis test; and calculating the actual movable oil index, and / or the maximum movable oil index, and / or the total oil index of the shale to be analyzed according to the actual total oil content, in combination with the corresponding step-by-step pyrolysis parameters and abundance at the current degree of thermal evolution, so as to evaluate the oil and gas mobility state of the shale.

[0017] Preferably, the method further comprises: performing light hydrocarbon evaporation correction treatment on the shale sample to use the treated sample for testing, or using a cryocoring sample for testing.

[0018] Preferably, the method further comprises:

[0019] The first eigenvalue curve in each single temperature step evaluation model is subjected to surface fitting, and the second eigenvalue curve in each single temperature step evaluation model is subjected to surface fitting.

[0020] Compared with the prior art, one or more embodiments of the above scheme may have the following advantages or beneficial effects:

[0021] The present invention proposes a method for evaluating shale oil reservoir resources. The method establishes a three-dimensional model for evaluating the quality of shale oil reservoir resources based on multi-temperature stage pyrolysis testing, and divides the resource quality from the perspectives of geochemical characteristics and oil and gas mobility. Compared with the traditional shale oil reservoir evaluation model, the three-dimensional shale oil reservoir resource quality evaluation model in the present invention has the following obvious advantages: (1) Characterizing the resource quality of shale oil reservoirs from two dimensions: geochemical characteristics and oil and gas mobility; (2) Introducing the parameter Tmax of thermal evolution maturity as an evaluation parameter for shale oil resource quality; (3) More accurately characterizing the movable shale oil content based on multi-temperature stage pyrolysis test parameters.

[0022] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0024] Figure 1 A diagram showing the steps of a method for evaluating shale oil reservoir resources according to an embodiment of the present application.

[0025] Figure 2 This is a schematic diagram of the correlation between various step-by-step pyrolysis parameters in the method for evaluating shale oil reservoir resources according to an embodiment of the present application.

[0026] Figure 3 This is a schematic diagram of the construction results of a single temperature step evaluation model in the method for evaluating shale oil reservoir resources in an embodiment of the present application.

[0027] Figure 4 It is a schematic diagram of the trend of the first characteristic value and the second characteristic value in the method for evaluating shale oil reservoir resources in an embodiment of the present application, respectively, changing with the degree of thermal evolution.

[0028] Figure 5 This is a schematic diagram of the construction results of the multi-level reservoir resource evaluation model in the method for evaluating shale oil reservoir resources in an embodiment of the present application.

[0029] Figure 6 This is an example diagram of the maturity distribution range of Da'anzhai shale in the prior art.

[0030] Figure 7 This is an example diagram of the trend of the first characteristic value, the second characteristic value and the total oil index corresponding to the method for evaluating shale oil reservoir resources according to an embodiment of the present application being applied to Da'anzhai shale as the degree of thermal evolution changes.

[0031] Figure 8 This is an example diagram of a multi-level reservoir resource evaluation model corresponding to when the method for evaluating shale oil reservoir resources in an embodiment of the present application is applied to Da'anzhai shale. DETAILED DESCRIPTION

[0032] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments of the present invention and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present invention.

[0033] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions. Also, although a logical sequence is shown in the flowchart, in some cases, the steps shown or described can be performed in a sequence different from that here.

[0034] Compared with conventional oil and gas, shale oil has the characteristics of short migration distance, small oil and gas loss, and great resource potential, and is a key area of ​​future oil and gas exploration. Since my country's shale oil producing layers are mainly continental sedimentary environments, strong heterogeneity is an unavoidable problem in oil and gas exploration. Therefore, clarifying the resource quality of shale oil reservoirs plays an important role in shale oil exploration.

[0035] At present, the resource quality of shale oil reservoirs is evaluated mainly from two aspects: shale oil mobility and geochemical characterization. From the perspective of mobility evaluation, there are two types of oil in shale: 1. Free oil in pores and cracks. This part of oil and gas often has good development potential and is considered to be movable oil; 2. Adsorbed oil in kerogen and on the surface of minerals. Under the conditions of fracturing development, this part of oil is still difficult to be developed and is considered to be immobile oil. Characterization of geochemical characteristics is another evaluation method. Different geochemical characteristics correspond to different resource potentials.

[0036] The existing technology has proposed many evaluation standards and models for the mobility and geochemical characterization of shale oil, including: First, beyond the effect limit is to evaluate the resource quality of shale oil reservoirs from the perspective of oil and gas mobility. By proposing a new evaluation parameter: hydrocarbon index OSI (S1 / TOC×100)>100mg / g TOC, it is believed that shale oil with OSI greater than 100 has industrial mining value. Although this method is simple and easy, when the resource quality is divided from the perspective of mobility alone, due to the low TOC of some strata, the OSI value may be abnormally high, resulting in inaccurate resource rating; second, based on geochemical characteristics, namely total organic matter content (TOC) and oil content index (S1 and asphalt "A"), the oil content of shale is divided into three levels by statistical methods. This method simply considers the geochemical characteristics of shale, but does not consider the mobility of shale oil, and cannot further clarify the industrially favorable sweet spot; third, a four-division method for shale oil resources is proposed, and a Resource evaluation model, which takes the shale oil mobility boundary value as the constraint value for classifying the resource quality of shale reservoirs. However, in the actual evolution of shale, the absorption capacity of hydrocarbons in shale will gradually change, which also means that the oil and gas mobility of shale at different thermal evolution maturity is not the same. Therefore, using a fixed oil and gas mobility boundary value as the constraint of the model may cause misjudgment of resource quality classification; Fourthly, the parameters characterizing thermal evolution maturity are introduced as independent variables for constructing resource quality rating, and a three-dimensional model for shale reservoir resource quality rating is constructed. Specifically, the hydrocarbon index OSI value is calculated based on the pyrolysis and TOC abundance data, and the OSI value and TOC are fitted according to the data model. max The relationship between the OSI value and the shale hydrocarbon expulsion threshold (HET) is established, and the OSI value at and after HET is taken as the oil and gas mobility boundary value OMT. However, this method is mainly used in conventional pyrolysis tests.

[0037] Although conventional pyrolysis data has been widely used in the oil industry, with the deepening of understanding of the storage mechanism of oil in different states in shale, more and more scholars have realized that conventional pyrolysis has two shortcomings: 1. The conventional pyrolysis parameter S1 (free hydrocarbon) does not represent the amount of oil generated in the shale, and therefore cannot accurately characterize the oil content of the shale; 2. Conventional pyrolysis cannot clearly determine the content of oil in different states in the shale, and cannot accurately characterize the mobility of shale oil. Therefore, the accuracy of the model still needs to be further improved.

[0038] Therefore, in order to solve one or more of the above technical problems, the embodiment of the present application proposes a method for evaluating shale oil reservoir resources. This method, on the one hand, innovatively updates the existing graded evaluation boundary values ​​of shale oil reservoir resource quality through step-by-step pyrolysis technology, and based on the total oil content obtained by the step-by-step pyrolysis parameters, newly characterizes the movable oil content of the area to be evaluated. In this way, the present invention not only establishes a more accurate shale oil reservoir resource quality evaluation model, but also characterizes the quality of shale oil reservoir resources from two dimensions: geochemical characteristics and oil and gas availability.

[0039] At present, the evaluation of shale oil reservoir resource quality is mainly based on conventional pyrolysis tests, but the accuracy is still insufficient. In order to more accurately characterize the oil content and mobility of shale, existing technologies have developed some new analytical testing methods, such as two-dimensional nuclear magnetic resonance, multi-temperature stage pyrolysis, etc. Among them, multi-temperature stage pyrolysis is widely used in the characterization of shale oil content and oil and gas mobility due to its accurate results and low application cost. The light components in shale that exist in a free state in macropores and connected pore systems can be released at a lower temperature, while the heavy components that exist in organic matter and micropores and unconnected pore systems in an adsorbed-mutually soluble state need to be released at a higher temperature or even at the organic matter cracking temperature. Based on this principle, the occurrence characteristics of shale oil can be clarified through the thermal release hydrocarbon peaks obtained under the constant heating mode, and the shale oil content in different occurrence states can be evaluated. When the temperature reaches 200°C, the thermal release hydrocarbon peak is a light hydrocarbon substance (S 1-1 ), which represents the actual movable oil volume in the shale. 1-2 The value is the medium and heavy components of the free oil released by heat when the temperature reaches 350°C. This part of the oil is not completely movable, that is, part of it is movable and part is immovable. 1-1 and S 1-2 The sum represents the total free oil in the shale (also called the maximum movable oil volume), S 2-1 It indicates the amount of oil stored in the adsorption-miscible state or adsorption state. At the same time, the sum of the three parameters is the amount of oil and gas that has been generated.

[0040] Figure 1 This is a step diagram of the method for evaluating shale oil reservoir resources in the embodiment of the present application. Figure 1 , the method for evaluating shale oil reservoir resources described in an embodiment of the present invention (hereinafter referred to as "resource evaluation method") is explained.

[0041] Step S110 calculates the step-by-step pyrolysis parameters and organic matter abundance of the shale sample at different thermal evolution degrees, and generates the first characteristic value and the second characteristic value corresponding to each thermal evolution degree. It should be noted that the embodiment of the present invention does not specifically limit the interval or step length between different thermal evolution degrees (different temperatures), and those skilled in the art can set it according to actual needs.

[0042] In step S110, a large number of shale oil reservoir samples need to be obtained first, and these samples are subjected to step-by-step pyrolysis test (also called "multi-temperature stage pyrolysis test") and organic matter abundance test.

[0043] It should be noted that in order to improve the fitting accuracy of the following first expression and second expression, the embodiment of the present invention needs to perform light evaporation correction treatment on each shale sample before testing the shale sample, so as to use the treated samples to implement step-by-step pyrolysis test and organic matter abundance test. In the process of sample acquisition and preservation, light hydrocarbon evaporation is an inevitable problem, which affects the accuracy of oil content assessment. Ignoring light hydrocarbon evaporation will lead to underestimation of shale oil content. Therefore, before evaluating the oil content of shale, light hydrocarbon evaporation correction is required. Alternatively, each shale sample is subjected to freeze coring treatment, so as to use the freeze coring samples to implement step-by-step pyrolysis test and organic matter abundance test.

[0044] After completing the above two tests for each sample, the step-by-step pyrolysis parameters and organic matter abundance parameters (TOC: shale organic matter abundance) corresponding to each shale sample at different thermal evolution levels are calculated. The step-by-step pyrolysis parameters include: S 1-1 Value (step-by-step pyrolysis of free hydrocarbons and light hydrocarbons), S 1-2 Value (step-by-step pyrolysis of free hydrocarbons and heavy hydrocarbons) and S 2-1 Value (step-by-step thermal desorption-hydrocarbons adsorbed in a mutually soluble state).

[0045] Since the step-by-step pyrolysis test has the advantage of accurately characterizing the amount of oil in different occurrence states in shale, the embodiment of the present invention uses multi-temperature-step pyrolysis data to construct a new resource quality evaluation model. Compared with the evaluation model established using conventional pyrolysis data, the model established based on multi-temperature-step pyrolysis has two advantages: 1. The TOY parameter can more accurately characterize the amount of generated oil; 2. The multi-temperature-step pyrolysis parameter is selected as the boundary value to quantify the mobility boundary value of shale oil.

[0046] Figure 2 This is a schematic diagram of the correlation between various step-by-step pyrolysis parameters in the method for evaluating shale oil reservoir resources according to an embodiment of the present application. Figure 2 The multi-temperature pyrolysis parameters (S) of the shale samples collected in the embodiment of the present invention are shown. 1-1 , S 1-2 and S 2-1 ), the results show that the three step-by-step pyrolysis parameter values ​​all show a good positive correlation, so there will be no situation where enriched resources with high mobility are misjudged as low-quality resources (for example: samples with high S 1-1 value, but S 1-2and S 2-1 The value is lower, resulting in a lower value of the total oil content TOY of the shale).

[0047] Finally, according to the step-by-step pyrolysis parameters and abundance parameters corresponding to each shale sample at different degrees of thermal evolution, the first eigenvalue M1 and the second eigenvalue M2 corresponding to each shale sample at different degrees of thermal evolution are calculated. 2-1 / TOC value) is S 2-1 The ratio of the value to the organic matter abundance TOC; the second characteristic value ((S 1-2 +S 2-1 ) / TOC value) is the ratio of the specified sum value to the organic matter abundance TOC, wherein the specified sum value is S 1-2 Value and S 2-1 The sum of values.

[0048] For resource quality evaluation, the multi-temperature pyrolysis parameter S 2-1 Value and S 1-2 +S 2-1 The geological meanings of the values ​​are: adsorbed oil (i.e., all immobile oil), all adsorbed oil, and partially movable oil. Therefore, these two values ​​can be used as constraints to clarify the mobility of shale oil. At the same time, considering that organic matter is the main body of shale oil adsorption, the influence of organic matter abundance on the boundary value can be eliminated by normalizing the TOC content. In this way, the embodiment of the present invention uses S 2-1 / TOC value and (S 1-2 +S 2-1 ) / TOC value is used as the boundary value for resource partitioning.

[0049] After the calculation of the first eigenvalue and the second eigenvalue of the shale sample is completed, the process proceeds to step S120. Step S120 constructs a multi-level reservoir resource evaluation model according to the first eigenvalue and the second eigenvalue corresponding to the different thermal evolution degrees obtained in step S110. The level boundary value of each level of the evaluation model is the first eigenvalue and the second eigenvalue corresponding to the corresponding evolution degree level.

[0050] In step S120, before constructing the multi-level reservoir resource evaluation model, it is necessary to process the first eigenvalue and the second eigenvalue corresponding to each thermal evolution degree obtained in step S110, so as to convert the first eigenvalue of each sample at different thermal evolution degrees into a first expression, and convert the second eigenvalue of each sample at different thermal evolution degrees into a second expression, so as to construct the multi-level reservoir evaluation model using the first eigenvalue and the second eigenvalue at different thermal evolution degrees shown in these two expressions.

[0051] As the thermal maturity increases, the adsorption capacity of kerogen for oil gradually decreases. 2-1 / TOC value and S 1-2 +S 2-1 The two boundary values ​​of / TOC value should also change dynamically at different thermal evolution maturity. Figure 4 It is a schematic diagram of the trend of the first characteristic value and the second characteristic value in the method for evaluating shale oil reservoir resources in an embodiment of the present application, respectively, changing with the degree of thermal evolution. Figure 4 The shale maturity is shown in Figure 2. 2-1 / TOC value and S 1-2 +S 2-1 / TOC value change trend. In general, S 2-1 / TOC value and S 1-2 +S 2-1 With the increase of maturity, the TOC value shows a trend of increasing first and then decreasing. Although the trend is the same, the change mechanism is different. 2-1 / TOC value, although the adsorption capacity of organic matter for oil shows a continuous downward trend, in the early stage of kerogen evolution, the amount of oil generated is far from meeting the adsorption capacity of kerogen, so the amount of adsorption shows an increasing state; after the amount of oil and gas generated is greater than the adsorption capacity of kerogen, S 2-1 / TOC value began to show a downward trend.

[0052] Specifically, according to the first eigenvalue corresponding to each sample at different degrees of thermal evolution obtained in step S110, a first expression characterizing the correlation between the first eigenvalue and the degree of thermal evolution is formed (fitted), and according to the second eigenvalue corresponding to each sample at different degrees of thermal evolution, a second expression characterizing the correlation between the second eigenvalue and the degree of thermal evolution is formed (fitted), so as to construct a multi-level reservoir resource evaluation model by using the first eigenvalue and the second eigenvalue at the corresponding degrees of thermal evolution indicated in the first expression and the second expression.

[0053] In this embodiment of the present invention, the first expression and the second expression are fitted using the following expression:

[0054]

[0055] Where i represents the eigenvalue number, Mi represents the first eigenvalue or the second eigenvalue calculated based on the measured value of the step-by-step pyrolysis test (i.e., the first eigenvalue M1 or the second eigenvalue M2 of each sample at different degrees of thermal evolution obtained after the step-by-step pyrolysis test), and β represents the maximum S in each expression. 2-1 The degree of thermal evolution corresponding to the value, T maxIt represents the temperature corresponding to each level of thermal evolution, and μ and θ represent the morphological parameters respectively.

[0056] In this way, after completing the construction of the above two expressions, we can start to build a multi-level reservoir resource evaluation model.

[0057] Specifically, first (step S1201, not shown), according to the first characteristic value at different degrees of thermal evolution indicated in the first expression and the second characteristic value at different degrees of thermal evolution indicated in the second expression, the total oil content (TOY) at different degrees of thermal evolution obtained based on the step-by-step pyrolysis test is calculated. That is, first, according to the fitted first expression, the first characteristic value at different degrees of thermal evolution is obtained, and according to the fitted second expression, the second characteristic value at different degrees of thermal evolution is obtained, and then, according to the first characteristic value and the second characteristic value obtained from the expression fitting curve, the total oil content value calculation formula (TOY=S 1-1 +S 1-2 +S 2-1 ), and the corresponding total oil content values ​​under different thermal evolution degree parameters are obtained. These total oil content values ​​TOY are obtained based on the step-by-step pyrolysis parameters.

[0058] Then, (step S1202, not shown) according to the total oil content values ​​under different thermal evolution degree parameters obtained in the above step S1201, the plane coordinate system of the single temperature step evaluation model under different thermal evolution degree parameters is constructed respectively with the organic matter abundance parameter as the horizontal coordinate and the total oil content as the vertical coordinate. In other words, for each thermal evolution degree parameter, the organic matter abundance parameter corresponding to the current thermal evolution degree parameter is used as the horizontal coordinate, and the total oil content value corresponding to the current thermal evolution degree parameter is used as the vertical coordinate, and the corresponding single temperature step evaluation model (i.e., the two-dimensional evaluation model of shale resources) is constructed for the current thermal evolution degree parameter.

[0059] Next, (step S1203, not shown) the first eigenvalue and the second eigenvalue at different thermal evolution levels are directly coupled to the corresponding single temperature evaluation model plane coordinate system. In other words, for each single temperature evaluation model corresponding to a temperature parameter (maturity or thermal evolution level), the first eigenvalue and the second eigenvalue corresponding to the current thermal evolution level parameter can be coupled to the two-dimensional evaluation model of the corresponding thermal evolution level. Among them, the effective resource level boundary values ​​corresponding to each level of the two-dimensional evaluation model are the first eigenvalue and the second eigenvalue at the corresponding evolution level.

[0060] Figure 3 Schematic diagram of the construction result of a single temperature step evaluation model in the method for evaluating shale oil reservoir resources in the embodiment of the present application. Figure 3As shown, for a two-dimensional evaluation model, the level boundary values ​​are the first eigenvalue and the second eigenvalue corresponding to the corresponding evolution degree level.

[0061] Further, refer to Figure 3 , the embodiment of the present invention uses the invalid resource boundary value, the dynamic first eigenvalue that changes with the degree of thermal evolution, and the dynamic second eigenvalue that changes with the degree of thermal evolution to divide the reservoir quality evaluation level of the shale to be analyzed into invalid resources ④, inefficient resources ③, potential resources ③ and enriched resources ①. That is to say, for each two-dimensional evaluation model under the degree of thermal evolution, the invalid resource boundary value, the first eigenvalue and the second eigenvalue under the corresponding temperature stage are used as the level boundary value of the two-dimensional evaluation model of resource quality at the current temperature stage.

[0062] It should be noted that each two-dimensional evaluation model formed in the embodiment of the present invention uses TOC and total oil content (TOY) to construct a corresponding plane coordinate system, and uses S generated based on the step-by-step pyrolysis parameters. 2-1 / TOC characteristic value and S 1-2 +S 2-1 / TOC characteristic value is used to construct a two-dimensional resource quality evaluation model of the corresponding thermal evolution degree. Among them, the invalid resource boundary value (preferably 1.2 mg HC / g Rock) in the embodiment of the present invention distinguishes invalid resources ④ from valid resources ①~③, and the boundary definition of invalid resources is preferably TOY<1.2 mg HC / g Rock.

[0063] Further, (step S1204, not shown) a multi-level reservoir resource evaluation model is established by superimposing single temperature-step evaluation models of multiple thermal evolution degrees.

[0064] Figure 5 This is a schematic diagram of the construction results of the multi-level reservoir resource evaluation model in the method for evaluating shale oil reservoir resources in the embodiment of the present application. Figure 5 In step S1204, it is necessary to superimpose the two-dimensional resource quality evaluation models at each thermal evolution degree according to the gradual change law of the thermal evolution degree (from large to small or from small to large), and build a multi-level reservoir resource evaluation model (shale reservoir resource quality three-dimensional evaluation model) formed by the single temperature step evaluation model of all thermal evolution degrees, thereby establishing a shale reservoir resource quality three-dimensional evaluation model under the background of different thermal evolution degrees.

[0065] It should be noted that, in the process of superimposing the two-dimensional evaluation models, the embodiment of the present invention can also perform surface fitting on the first eigenvalue curve (straight line) indicated in each two-dimensional evaluation model, and form a first eigenvalue dynamic change surface based on the continuous temperature step change state in the multi-level reservoir resource evaluation model, see Figure 8; and performing surface fitting on the second eigenvalue curve (straight line) indicated in each two-dimensional evaluation model to form a second eigenvalue dynamic change surface based on continuous temperature step change state in the multi-level reservoir resource evaluation model, see Figure 8 .

[0066] In this way, the multi-level reservoir resource evaluation model formed by the embodiment of the present invention is constructed based on TOC and TOY values, and divides shale reservoirs into four levels based on two boundary values ​​and an invalid resource boundary value.

[0067] After the multi-level reservoir resource evaluation model is constructed, the process proceeds to step S130 to evaluate the resource level of the shale that actually needs to be analyzed.

[0068] Step S130 uses the multi-level reservoir resource evaluation model constructed in step S120 to directly evaluate the reservoir resource grade of the shale to be analyzed. In step S130, the shale sample to be analyzed is subjected to a step-by-step pyrolysis test and an organic matter abundance test, and the actual step-by-step pyrolysis parameters and actual abundance corresponding to the current actual evolution degree are calculated. Based on this, the multi-level reservoir resource evaluation model is used to obtain the reservoir quality grade of the current shale sample to be analyzed.

[0069] Specifically, first determine the actual evolution degree of the shale sample to be analyzed that needs to be evaluated; then perform an organic matter abundance test and a step-by-step pyrolysis test based on the current evolution degree on the shale sample to be analyzed, and calculate the actual step-by-step pyrolysis parameters and actual abundance corresponding to the current actual evolution degree; calculate the actual total oil content based on the current actual step-by-step pyrolysis parameters using the above-mentioned total oil content value calculation formula; then, select a two-dimensional evaluation model corresponding to the current evolution degree from the multi-level reservoir resource evaluation model, combine the actual abundance and the actual total oil content, and determine the reservoir quality grade of the shale sample to be analyzed through the reservoir quality grade area where the current calculation result point falls.

[0070] In addition, since the geochemical parameters of different kerogen types vary greatly, which leads to differences in the quality of shale oil reservoirs, in the embodiments of the present invention, it is necessary to classify samples by kerogen type to explore the differences in the geochemical characteristics and resource quality of shale samples.

[0071] However, due to the differences in geochemical parameters, the absolute values ​​of the step-by-step pyrolysis parameters are difficult to reflect the oil content and oil and gas mobility of unit mass of organic matter. Therefore, the present invention proposes three parameters that can characterize the oil content of unit mass of organic matter, specifically including: the actual movable oil index (OSI f =S 1-1 / TOC), Maximum movable oil index (OSI) m =(S 1-1 +S1-2 ) / TOC) and Total Oil Index (OSI t =TOY / TOC).

[0072] Furthermore, after obtaining the step-by-step pyrolysis parameters of the shale sample to be analyzed obtained in the step-by-step pyrolysis test, the embodiment of the present invention will also calculate the actual total oil content according to the step-by-step pyrolysis parameters obtained in the step-by-step pyrolysis test, and calculate the actual total oil content (TOY) of the shale sample to be analyzed. Then, according to the actual total oil content of the shale to be analyzed currently obtained, combined with the actual step-by-step pyrolysis parameters and actual abundance parameters corresponding to the current thermal evolution degree, the actual movable oil index, and / or the maximum movable oil index, and / or the total oil index of the shale to be analyzed are calculated, so as to use these three parameters characterizing the oil content to evaluate the oil and gas mobility state of the current shale to be analyzed.

[0073] Therefore, the embodiment of the present invention more accurately characterizes the movable shale oil content characteristics based on the step-by-step pyrolysis test parameters. Moreover, from the above three parameters characterizing the oil content, it can be seen that the three-dimensional evaluation model constructed by the embodiment of the present invention can characterize the resource quality of shale oil reservoirs from two dimensions: geochemical characteristics and oil and gas mobility.

[0074] Example:

[0075] The Sichuan Basin is located in the northwest of the Yangtze Platform. It is a secondary structural unit extending from the Yangtze Platform to the northwest in a diamond-shaped quadrilateral with a northeast orientation. It covers an area of ​​about 26.0×10 4 km 2 The basin has a continuous sequence of marine and continental stratigraphic sequences from the Precambrian to the Cenozoic. In the early Late Triassic, the uplift of the Yangtze Platform led to a transition from marine carbonate rocks to continental siliceous clastic sediments. The Jurassic is mainly a continental sedimentary assemblage of clastic rocks intercalated with limestone. The strata are widely distributed in the basin, covering an area of ​​about 18×10 4 km 2 The thickness of the formation is 500-4 500m. From bottom to top, the Ziliujing Formation, Lianggaoshan Formation, Shaximiao Formation, Suining Formation and Penglaizhen Formation are developed in sequence. The basin in the Early Jurassic was mainly a lacustrine sedimentary environment. The lake basin area was the largest during the deposition of the Da'anzhai Member, and the thickness of the source rock in the sedimentary center was greater than 50m. The main body of the Da'anzhai Member is a shale formation dominated by fine-grained sediments of semi-deep lake to deep lake phases. It has the characteristics of high organic matter abundance, developed shale formation laminae, high clay content and low porosity. It can be divided into three sub-members from bottom to top, among which black mud shale is concentrated in the middle with a thickness of 30-70m. The shell limestone in the upper and lower sub-members is often interbedded or interlayered with dark mud shale. Recent exploration results show that the Da'anzhai Member of the Ziliujing Formation is the most important oil and gas producing layer in the Jurassic in the Sichuan Basin, with a resource volume of up to 9.78×10 8t, with good exploration potential for tight oil and shale oil. The study area is the Langzhong area in the northern slope zone of the Central Sichuan Uplift, with an area of ​​603.53 km 2 The Da'anzhai section in the study area is characterized by frequent inter- or lateral contact between shell limestone and shale, with a thickness of 75-100 m. Currently, horizontal well fracturing is used to develop the organic-rich shale and carbonate interlayers in Da'anzhai.

[0076] Thermal evolution is an important parameter that determines the resource potential of shale oil reservoirs. max It is one of the most commonly used parameters to evaluate the degree of thermal evolution. Figure 6 This is an example diagram of the maturity distribution range of Daanzhai shale in the prior art. Figure 6 As shown, the shale sample T in the study area max The T max All are greater than 435°C, indicating that the Da'anzhai shale is mainly in the mature stage.

[0077] According to the multi-level reservoir resource evaluation model constructed above, the two boundary values ​​(S 2-1 / TOC value and S 1-2 +S 2-1 / TOC value) and its evolution at different maturity levels are the basis for model establishment. Figure 7 The following is an example of the trend of the first characteristic value, the second characteristic value and the total oil index corresponding to the change of the degree of thermal evolution when the method for evaluating shale oil reservoir resources in the embodiment of the present application is applied to Da'anzhai shale. A large number of Da'anzhai shale samples are subjected to the resource evaluation method described above in the present invention, and the two boundary value change curves and the multi-level reservoir resource evaluation model are constructed, such as Figure 7 As shown in Figure 2, the three parameter values ​​(two boundary values ​​and TOY / TOC values) change with T max The increase of the three parameters shows a trend of increasing first and then decreasing. For Daanzhai shale, the values ​​of the three parameters are all within the range of T max =438℃, reaching the maximum values ​​of 92.6, 173.0 and 225.3 mg HC / g TOC respectively, indicating that the oil and gas adsorption and oil content of shale reached the highest point. After that, the values ​​of the three parameters gradually decreased, indicating that the adsorption of oil by organic matter in shale gradually decreased, and the free oil content gradually decreased due to hydrocarbon expulsion and the deterioration of physical properties in shale. max =460℃, the parameter values ​​are 18.4, 35.9 and 49.1 mg HC / g TOC respectively.

[0078] Figure 8This is an example diagram of a multi-level reservoir resource evaluation model corresponding to the method for evaluating shale oil reservoir resources in the embodiment of the present application being applied to Da'anzhai shale. Based on the statistical model of boundary values ​​and shale geochemical characteristics, the embodiment of the present invention establishes a three-dimensional resource quality evaluation model for Da'anzhai shale in the study area, such as Figure 8 As shown. Based on the invalid resource classification standard, the embodiment of the present invention combines the statistical model of two boundary values, introduces the parameter Tmax characterizing the thermal evolution maturity as an independent variable, and determines the boundary values ​​under different maturity backgrounds, thereby constructing a three-dimensional resource quality evaluation model for shale oil. According to the three-dimensional evaluation model proposed in the embodiment of the present invention, among the 198 valid samples, there are 132 samples belonging to enriched resources, accounting for 66.7%; there are 28 samples belonging to potential resources, accounting for 14.1%; there is 1 sample belonging to inefficient resources, accounting for 0.5%; and there are 37 invalid resources, accounting for 18.7%.

[0079] The geochemical parameters of different kerogen types vary greatly, which leads to differences in the quality of shale oil reservoirs. In this section, we classify samples by kerogen type and explore the differences in their geochemical characteristics and resource quality (Table 1).

[0080] From the data in Table 1, type II1 shale has the best geochemical characteristics, oil content and oil and gas mobility, followed by type II2 shale, and type III shale is the worst. However, due to the differences in geochemical parameters, the absolute values ​​of the step-by-step pyrolysis parameters cannot reflect the oil content and oil and gas mobility of unit mass of organic matter. Therefore, we proposed three parameters to characterize the oil content of unit mass of organic matter: the actual movable oil index (OSI f =S 1-1 / TOC), Maximum movable oil index (OSI) m =(S 1-1 +S 1-2 ) / TOC) and Total Oil Index (OSI t =TOY / TOC).

[0081] Furthermore, the embodiment of the present invention uses three oil content evaluation parameters to classify kerogen shales into three types. Among them, the oil content and oil and gas mobility of unit organic matter of type II1 shale are still the highest, followed by type II2, and type III is the lowest. Although the average values ​​of the three parameters of type II1 shale are the highest, the maximum values ​​of the three parameters of type II2 shale are the highest among all samples, indicating strong heterogeneity. At the same time, compared with type II1 and type II2 shale, the oil content and oil and gas mobility of type III shale are significantly lower, indicating poor exploration potential. The differences in geochemical characteristics, oil content and oil and gas mobility are also reflected in the resource quality evaluation model: Type II1 shale contributes the main enriched resources (52.3%), and the remaining 1 sample point belongs to potential resources; similarly, Type II2 shale also contributes a lot to enriched resources (46.2%), and the remaining samples are mainly potential resources (contributing half of all potential resources), and only 2 samples are classified as invalid resources; while Type III shale has poor exploration potential, more than half of the samples are classified as invalid resources, and the remaining samples are mainly classified as potential resources (accounting for 46.4% of all potential resources), and a small number of samples are enriched and inefficient resources.

[0082] The present invention discloses a method for evaluating shale oil reservoir resources. The method establishes a three-dimensional model for evaluating the quality of shale oil reservoir resources based on multi-temperature stage pyrolysis testing, and divides the resource quality from the perspectives of geochemical characteristics and oil and gas mobility. Compared with the traditional shale oil reservoir evaluation model, the three-dimensional shale oil reservoir resource quality evaluation model in the present invention has the following obvious advantages: (1) characterizing the resource quality of shale oil reservoirs from two dimensions: geochemical characteristics and oil and gas mobility; (2) introducing the parameter T of thermal evolution maturity max As an evaluation parameter for the quality of shale oil resources; (3) Based on multi-temperature stage pyrolysis test parameters, the movable shale oil content can be more accurately characterized.

[0083] The above is only a 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 thought of by any person familiar with the technology within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0084] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0085] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0086] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for evaluating shale oil reservoir resources, characterized in that: The method comprises: Step 1: By testing the step-by-step pyrolysis parameters and organic matter abundance of shale samples at different thermal evolution levels, the first characteristic value and the second characteristic value corresponding to each thermal evolution level are generated. The first characteristic value represents the amount of oil S in the adsorption-miscible state or adsorption state. 2-1 The second characteristic value is the ratio of the specified sum value to the organic matter abundance, wherein the specified sum value is the oil amount S of the medium and heavy components of the free oil. 1-2 Value and S 2-1 The sum of values; Step 2: construct a multi-level reservoir resource evaluation model according to the first eigenvalue and the second eigenvalue corresponding to each order of thermal evolution degree, wherein the level boundary value of each level of the evaluation model is the first eigenvalue and the second eigenvalue corresponding to the corresponding evolution degree level, and the step 2 includes: According to the first characteristic value and the second characteristic value at different thermal evolution degrees, the total oil content at different thermal evolution degrees obtained based on the step-by-step pyrolysis test is calculated; Using the organic matter abundance and the total oil content as horizontal and vertical coordinates, single temperature step evaluation models under different thermal evolution degrees are constructed respectively; coupling the first eigenvalue and the second eigenvalue at different thermal evolution degrees into the corresponding single temperature step evaluation model; Establishing the multi-level reservoir resource evaluation model by superimposing the single temperature-step evaluation models of multiple thermal evolution degrees; Step three: using the multi-level reservoir resource evaluation model to evaluate the reservoir resource level of the shale to be analyzed.

2. The method according to claim 1, characterized in that: In the step 2, it also includes: processing the first eigenvalue and the second eigenvalue corresponding to the thermal evolution degree of each order, wherein: According to the first eigenvalue corresponding to each thermal evolution degree, a first expression characterizing the correlation between the first eigenvalue and the thermal evolution degree is formed, and according to the second eigenvalue corresponding to each thermal evolution degree, a second expression characterizing the correlation between the second eigenvalue and the thermal evolution degree is formed, so as to construct the multi-level reservoir resource evaluation model by using the eigenvalues ​​indicated in the first expression and the second expression for the corresponding thermal evolution degree.

3. The method according to claim 1 or 2, characterized in that: The reservoir quality evaluation grade of the shale to be analyzed is divided into invalid resources, inefficient resources, potential resources and enriched resources by using the invalid resource boundary value and the dynamic first characteristic value and the dynamic second characteristic value that change with the degree of thermal evolution.

4. The method according to claim 2, characterized in that: The first expression and the second expression are fitted using the following expression: Where i represents the eigenvalue number, Mi represents the first eigenvalue or the second eigenvalue calculated based on the measured value of the step-by-step pyrolysis test, and β represents the maximum S 2-1 The degree of thermal evolution corresponding to the value, T max It represents the temperature corresponding to each level of thermal evolution, and μ and θ represent the morphological parameters respectively.

5. The method according to claim 3, characterized in that: In the step three, it includes: The shale samples to be analyzed are subjected to step-by-step pyrolysis tests and organic matter abundance tests, and the actual step-by-step pyrolysis parameters and actual abundance corresponding to the current actual evolution degree are calculated. Based on this, the multi-level reservoir resource evaluation model is used to obtain the reservoir quality grade of the current shale samples to be analyzed.

6. The method according to claim 3, characterized in that The method further comprises: Calculate the actual total oil content according to the step-by-step pyrolysis parameters obtained from the step-by-step pyrolysis test; According to the actual total oil content, combined with the corresponding step-by-step pyrolysis parameters and abundance under the current thermal evolution degree, the actual movable oil index, and / or the maximum movable oil index, and / or the total oil index of the shale to be analyzed are calculated to evaluate the oil and gas mobility state of the shale.

7. The method according to claim 1 or 2, characterized in that: The method further comprises: performing light hydrocarbon evaporation correction treatment on the shale sample to use the treated sample for testing, or using a frozen core sample for testing.

8. The method according to claim 1, characterized in that The method further comprises: The first eigenvalue curve in each single temperature step evaluation model is subjected to surface fitting, and the second eigenvalue curve in each single temperature step evaluation model is subjected to surface fitting.

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