Shale oil reservoir classification evaluation method

Abstract

The invention relates to a shale oil reservoir classification evaluation method, and belongs to the technical field of shale oil and gas resource evaluation. The method comprises the following specific steps: obtaining sample pyrolytic hydrocarbon S1, total organic carbon TOC, movable oil content OMob and quantitative fluorescence QGF-E of extract liquor; obtaining pore volumes in different pore diameter ranges of the sample; drawing intersection curves of pore volumes in different pore diameter ranges and S1, TOC, OMob and QGF-E, and determining intersection points of the intersection curves; and classifying the shale oil reservoirs according to the S1, TOC, OMob and QGF-E. The S1, TOC, OMob and QGF-E correspond to the intersection points. According to the method, different types of pore volumes and shale oiliness master control parameters are brought into a shale oil reservoir classification evaluation scheme for the first time, the shale oil reservoir microscopic heterogeneity and the influence on the oiliness thereof are comprehensively and accurately represented, and the method has good applicability to the shale oil reservoir with a complex pore structure; and scientific guidance can be provided for shale oil dessert optimization and development scheme compilation.

Description

Technical Field

[0001] The present invention relates to a method for classifying and evaluating shale oil reservoirs, belonging to the technical field of shale oil and gas resource evaluation. Background Art

[0002] Reservoir classification and evaluation is an important part of shale oil exploration and development, and is of great significance for scientifically guiding the optimization of shale oil "sweet spots". The micro-pore structure of shale oil reservoirs is very complex, resulting in strong heterogeneity in the oil-bearing property of shale reservoirs, which poses great challenges to the classification and evaluation of shale oil reservoirs.

[0003] Zhou Yan, Wang Changsheng, Lin Weichuan et al. published the "Logging Evaluation Method and Application of Geochemical Parameters of Shale Oil Source Rocks" in Logging Technology on June 20, 2022. Taking the Chang 73 shale in the Longdong area of the Ordos Basin as the research object, using the logging evaluation parameter system of source rocks, based on a variety of geochemical parameters, including organic carbon content, hydrocarbon generation potential, chloroform bitumen "A" and vitrinite reflectance, a comprehensive evaluation index P of source rocks was constructed, and a classification and evaluation standard for shale oil reservoirs was established, realizing the continuous and rapid evaluation of shale oil resource quality; Lei Haiyan, Guo Pei, Meng Ying et al. published the "Pore Structure and Classification Evaluation of Permian Fengcheng Formation Shale Oil Reservoirs in Mahu Sag" in Lithologic Reservoirs on March 29, 2022. In this paper, the high-pressure mercury injection experiment was used to conduct a detailed study and classification evaluation on the pore structure of the Fengcheng Formation shale oil reservoir in Well Maye 1 in the Junggar Basin;

[0004] The invention patent with the authorization announcement number CN105334149B provides a method for evaluating the micro-pore structure of tight reservoirs and classifying reservoirs. This method analyzes sedimentary facies, petrological characteristics, diagenesis, micro-pore structure parameters and reservoir physical property characteristics, and selects parameters to classify reservoirs; the invention patent with the authorization announcement number CN111027818B provides a method for classifying and evaluating shale oil. This method accurately classifies the quality of shale oil through six steps: selecting sweetness evaluation parameters representing the characteristics of shale oil reservoirs, obtaining the parameter values of sweetness evaluation parameters, determining the weight of each single sweetness evaluation parameter, calculating the sweetness evaluation index, classifying shale oil, and selecting favorable target areas for shale oil.

[0005] In summary, although the above methods give classification and evaluation schemes for shale oil / tight oil reservoirs from various angles, they do not provide a method that can both describe the heterogeneity of the micro-pore structure of shale oil reservoirs and characterize the oil-bearing characteristics of shale due to the strong heterogeneity of shale oil reservoirs. Therefore, it is necessary to seek a new method for classifying and evaluating shale oil reservoirs, and incorporate the heterogeneity of the micro-pore structure of shale oil reservoirs and its relationship with shale oil-bearing property into the reservoir classification and evaluation scheme, so as to scientifically guide the efficient development of shale oil. Summary of the Invention

[0006] The present invention discloses a classification and evaluation method for shale oil reservoirs, providing scientific guidance for shale oil resource evaluation and sweet spot optimization.

[0007] The technical solution adopted by the present invention is as follows: a classification and evaluation method for shale oil reservoirs, and the specific steps are as follows:

[0008] Step 1: Conduct a rock pyrolysis experiment on the shale oil sample to obtain the pyrolysis hydrocarbon S of the sample 1 ;

[0009] Step 2: Conduct a total organic carbon content determination experiment on the shale oil sample to obtain the total organic carbon TOC of the sample;

[0010] Step 3: Conduct a two-dimensional nuclear magnetic resonance experiment on the shale oil sample to obtain the movable oil content O of the sample Mob ;

[0011] Step 4: Conduct a quantitative fluorescence experiment on the shale oil sample to obtain the quantitative fluorescence Q of the sample extract GF-E ;

[0012] Step 5: Conduct a high-pressure mercury injection experiment on the shale oil sample to obtain the pore volume in different pore size ranges of the sample;

[0013] Step 6: Make cross curves of the pore volume in different pore size ranges with S 1 , TOC, O Mob and Q GF-E to determine the intersection points of the cross curves;

[0014] Step 7: Classify the shale oil reservoir according to S 1 , TOC, O Mob and Q GF-E corresponding at the intersection points.

[0015] Furthermore, before the rock pyrolysis experiment in Step 1, the shale sample needs to be sealed and stored.

[0016] Furthermore, during the rock pyrolysis experiment in Step 1, the pyrolysis hydrocarbon S1 is collected at 300 °C.

[0017] Furthermore, before the total organic carbon content determination experiment in Step 2, the shale sample needs to be pretreated, and the specific process is as follows:

[0018] (1) Grind the shale sample into 100-mesh powder using an agate mortar;

[0019] (2) Add the shale powder to dilute hydrochloric acid and react for 2 hours to completely remove inorganic minerals;

[0020] (3) Rinse the shale sample treated with dilute hydrochloric acid with distilled water for 10 minutes until neutral;

[0021] (4) Place the powdered shale sample in a constant temperature drying oven and dry it at 60 °C for 24 hours.

[0022] Further, before the two-dimensional nuclear magnetic resonance experiment in step 3, the sample needs to be processed into a columnar plug with a diameter of 2.5 cm and a length of 3 cm.

[0023] Further, before the quantitative fluorescence experiment in step 4, use an agate mortar to grind the shale sample into a powder with a mesh size of 60 - 80, and use dichloromethane to extract the free hydrocarbons on the particle surface of the powdered shale sample.

[0024] Further, before the high-pressure mercury injection experiment in step 5, the sample needs to be pretreated, and the specific process is as follows:

[0025] (1) After cleaning the surface of the shale sample, process the sample into a columnar plug with a diameter of 2.5 cm and a length of 3 cm;

[0026] (2) Wash the columnar plug shale sample with oil, and the organic solvent for washing oil is chloroform;

[0027] (3) Dry the washed columnar plug shale sample, the temperature is 105 °C, and the time is 24 h.

[0028] Further, in step 5, the pore volumes in different pore size ranges of the sample are obtained, and the different pore sizes respectively refer to: micropores (r < 25 nm), mesopores (25 < r < 100 nm), and macropores (r > 100 nm).

[0029] The present invention discloses a classification and evaluation method for shale oil reservoirs. Its beneficial effect is that compared with the prior art, this method first incorporates different types of pore volumes and the main controlling parameters of shale oil content into the classification and evaluation scheme for shale oil reservoirs, comprehensively and accurately characterizing the microscopic heterogeneity of shale oil reservoirs and its influence on oil content, having good applicability to shale oil reservoirs with complex pore structures, and can provide scientific guidance for the optimization of shale oil sweet spots and the preparation of development plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 Shown is the crossplot of pyrolysis hydrocarbon S1 and pore volumes in different pore size ranges;

[0032] Figure 2 Shown is the crossplot curve of total organic carbon (TOC) and pore volume in different pore size ranges;

[0033] Figure 3 Shown is the movable oil content O Mob and the crossplot curve of pore volume in different pore size ranges;

[0034] Figure 4 Shown is the crossplot curve of quantitative fluorescence Q of the extract GF-E and the pore volume in different pore size ranges.

[0035] Specific implementation method

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0037] The following description of at least one exemplary embodiment is merely illustrative in nature and in no way serves as a limitation to the present invention or its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0038] Embodiment 1

[0039] In this embodiment, 64 shale oil samples are taken from the Qingshankou Formation in the Changling Fault Depression in the southern Songliao Basin. A method for classifying and evaluating shale oil reservoirs comprises the following specific steps:

[0040] Step 1: Conduct a rock pyrolysis experiment on the shale oil samples to obtain the pyrolysis hydrocarbon S of the samples 1 ;

[0041] The model of the rock pyrolysis experiment instrument is: Rock-Eval-6 Plus source rock analyzer;

[0042] Before the rock pyrolysis experiment, the shale samples need to be sealed and stored;

[0043] Before the rock pyrolysis experiment, use an agate mortar to grind the shale samples into powders with a mesh size of 80 - 100;

[0044] During the rock pyrolysis experiment, collect the pyrolysis hydrocarbon S at 300 °C 1 ;

[0045] Step 2: Conduct an experiment on measuring the total organic carbon content of the shale oil samples to obtain the total organic carbon TOC of the samples;

[0046] The model of the instrument for measuring the total organic carbon content is: CS744 carbon and sulfur analyzer;

[0047] Before the total organic carbon content determination experiment, the shale samples need to be pretreated. The specific process is as follows:

[0048] (1) Grind the shale samples into 100-mesh powder using an agate mortar;

[0049] (2) Add the shale powder to dilute hydrochloric acid and react for 2 hours to completely remove inorganic minerals;

[0050] (3) Rinse the shale samples treated with dilute hydrochloric acid with distilled water for 10 minutes until neutral;

[0051] (4) Place the powdered shale samples in a constant-temperature drying oven and dry at 60 °C for 24 hours.

[0052] Weigh 5 g of the shale powder sample and place it in a dried porcelain crucible. Add 1 g of iron filings flux and 1 g of tungsten grains flux, input the mass of the sample to be measured, and measure the TOC content of the sample on the machine.

[0053] Step 3: Conduct a two-dimensional nuclear magnetic resonance experiment on the shale oil sample to obtain the movable oil content O of the sample Mob ;

[0054] The model of the two-dimensional nuclear magnetic resonance experiment instrument is: MR Cores-XX high-precision bench-top nuclear magnetic resonance unconventional core analyzer;

[0055] Before the two-dimensional nuclear magnetic resonance experiment, the sample needs to be processed into a cylindrical plug with a diameter of 2.5 cm and a length of 3 cm;

[0056] The two-dimensional nuclear magnetic resonance experiment includes the following steps:

[0057] (1) Conduct a detection and calibration of the content of 1 H compounds on the two-dimensional nuclear magnetic resonance experiment instrument;

[0058] (2) Conduct a nuclear magnetic T 2 detection to obtain the total amount of 1 H compounds in the shale sample;

[0059] (3) Conduct a T 1 -T 2 two-dimensional nuclear magnetic detection to obtain a two-dimensional spectrum;

[0060] (4) Divide the two-dimensional spectrum, quantitatively calculate the contents of different compounds in the shale, and obtain the movable oil content O of the shale Mob .

[0061] Step 4: Conduct a quantitative fluorescence experiment on the shale oil sample to obtain the quantitative fluorescence Q of the sample extract GF-E ;

[0062] The model of the quantitative fluorescence experiment instrument is: Agilent Cary Eclipse fluorescence spectrophotometer from the United States;

[0063] Before the quantitative fluorescence experiment, use an agate mortar to grind the shale sample into a powder with a mesh size of 60 - 80;

[0064] Use dichloromethane to extract the free hydrocarbons on the surface of the powder shale sample;

[0065] Weigh 2 g of the shale powder sample with a balance and put it into a beaker, add 20 mL of dichloromethane, and ultrasonically oscillate for 10 min;

[0066] Replace the detection software of the fluorescence spectrophotometer with a liquid fluorescence detection accessory;

[0067] Open the computer control software of the fluorescence spectrophotometer and set the Q GF-E detection parameters;

[0068] Before testing the sample, a dichloromethane blank sample should be made first, and the background Q GF-E maximum intensity does not exceed 10 pc;

[0069] Pour the free hydrocarbon extraction solution into a 3.5 mL quartz cuvette and detect the Q GF-E spectrum and save the file.

[0070] Step 5: Conduct a high-pressure mercury intrusion experiment on the shale oil sample to obtain the pore volume in different pore size ranges of the sample;

[0071] The model of the high-pressure mercury intrusion experiment instrument is: AutoPore Ⅳ 9505 pore analyzer;

[0072] The maximum mercury injection pressure of the experimental instrument is 200 MPa, and the minimum mercury injection pore radius is 3.7 nm;

[0073] The environment of the high-pressure mercury intrusion experiment is: temperature: 22.1 - 25.8 °C, relative humidity: 18 - 22%;

[0074] Before the high-pressure mercury intrusion experiment, the sample needs to be pretreated, and the specific process is as follows:

[0075] (1) After cleaning the surface of the shale sample, process the sample into a columnar plug with a diameter of 2.5 cm and a length of 3 cm;

[0076] (2) Wash the oil of the columnar plug shale sample, and the organic solvent for washing oil is chloroform;

[0077] (3) Dry the washed columnar plug shale sample, the temperature is 105 °C, and the time is 24 h;

[0078] The different pore size ranges refer to: micropores (r < 25 nm), mesopores (25 < r < 100 nm), and macropores (r > 100 nm).

[0079] Step 6: Plot the curves of pore volume in different pore size ranges against S 1 , TOC, O Mob and Q GF-E to determine the intersection points of the intersection curves;

[0080] As Figures 1 to 4 shown, they are the intersection curves of S 1 , TOC, O Mob and Q GF-E with the pore volume in different pore size ranges respectively;

[0081] Taking Figure 1 as an example, there are two intersection points on the intersection curve. The X-axis is the pyrolysis hydrocarbon S1, and the Y-axis is the pore volume. Among them, the red line represents micropores, the yellow line represents mesopores, and the blue line represents macropores;

[0082] Red: y = -0.0036x + 0.0131, correlation coefficient R 2 = 0.9573 (1)

[0083] Yellow: y = 0.0024x + 0.0078, R 2 = 0.9652 (2)

[0084] Blue: y = 0.0022x + 0.0014, R 2 = 0.9017 (3)

[0085] The intersection point 1 is calculated by simultaneously solving equations (1) and (2), and the intersection point 2 is calculated by simultaneously solving equations (1) and (3); the intersection point 1 is S1 = 0.88 mg / g; the intersection point 2 is S1 = 2.02 mg / g;

[0086] Similarly, the intersection points of the intersection curve in Figures 2 to 4 can be calculated;

[0087] Figure 2 The two intersection points in

[0088] Figure 3 are TOC = 1.07% and TOC = 2.68% respectively; Mob The two intersection points in Mob are O

[0089] Figure 4 = 1.79 mg / g and O GF-E = 9.6×10 4 and Q GF-E = 22.6×104 ;

[0090] Step 7: Classify the shale oil reservoir according to S 1 , TOC, O Mob and Q GF-E corresponding to the intersection point.

[0091] According to the values of S 1 , TOC, O Mob and Q GF-E calculated in Step 6, the reservoir can be divided into 3 categories;

[0092] The specific classification criteria are shown in Table 1;

[0093] Table 1

[0094]

[0095] When there are contradictions in classifying the shale oil reservoir using the above 4 parameters, classify the shale oil reservoir according to the following principles;

[0096] For a specific shale sample, assign scores to the 4 parameters S 1 , TOC, O Mob and Q GF-E corresponding to the sample respectively, and calculate the average value after scoring the sample. Determine the type of the shale sample according to the average score;

[0097] Class I, Class II and Class III are assigned scores of 1, 2 and 3 respectively;

[0098] Taking sample A as an example, the S 1 , TOC, O Mob and Q GF-E of this sample are S 1 = 1.8 mg / g, TOC = 2.7%, O Mob = 1.75 mg / g, Q GF-E = 23.5×10 4 ;

[0099] Then, according to S 1 , TOC, O Mob and Q GF-E these 4 parameters, the types to which sample A belongs after classification are Class II, Class I, Class III and Class I respectively, and the corresponding scored values are 2, 1, 3, 1, and the average value is 7 / 4 = 1.75;

[0100] According to the rounding principle, the average value 1.75 is approximately taken as 2, that is, sample A belongs to Class II.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for classifying and evaluating shale oil reservoirs, characterized in that, it includes the following steps: Step 1: Conduct a rock pyrolysis experiment on the shale oil sample to obtain the pyrolysis hydrocarbon S of the sample 1 ; Step 2: Conduct an experiment to measure the total organic carbon content of the shale oil sample to obtain the total organic carbon TOC of the sample; Step 3: Conduct two-dimensional nuclear magnetic resonance experiments on the shale oil sample to obtain the movable oil content O of the sample Mob ; Step 4: Conduct a quantitative fluorescence experiment on the shale oil sample to obtain the quantitative fluorescence Q of the sample extract GF-E ; Step 5: Conduct a high-pressure mercury injection experiment on the shale oil sample to obtain the pore volume in different pore size ranges of the sample; Step 6: Make the intersection curves of the pore volume with different pore size ranges and S 1 , TOC, O Mob and Q GF-E , and determine the intersection points of the intersection curves; Step 7: Classify the shale oil reservoir according to S 1 , TOC, O Mob and Q GF-E corresponding to the intersection point.

2. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, before the rock pyrolysis experiment in Step 1, the shale sample needs to be sealed and stored.

3. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, during the rock pyrolysis experiment in Step 1, pyrolysis hydrocarbons S1 are collected under the condition of 300°C.

4. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, before the total organic carbon content measurement experiment in Step 2, the shale sample needs to be pretreated, and the specific process is as follows: Step 2.1: Use an agate mortar to grind the shale sample into a powder with a mesh size of 100; Step 2.2: Add the shale powder to dilute hydrochloric acid and react for 2 hours to completely remove inorganic minerals; Step 2.3: Rinse the shale sample treated with dilute hydrochloric acid with distilled water for 10 minutes until it is neutral; Step 2.4: Place the powdered shale sample in a constant temperature drying oven and dry it at 60°C for 24 hours.

5. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, before the two-dimensional nuclear magnetic resonance experiment in Step 3, the sample needs to be processed into a cylindrical plug with a diameter of 2.5 cm and a length of 3 cm.

6. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, before the quantitative fluorescence experiment in Step 4, use an agate mortar to grind the shale sample into a powder with a mesh size of 60 - 80, and use dichloromethane to extract the free hydrocarbons on the particle surface of the powdered shale sample.

7. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, before the high-pressure mercury injection experiment in Step 5, the sample needs to be pretreated, and the specific process is as follows: Step 5.1: After cleaning the surface of the shale sample, process the sample into a cylindrical plug with a diameter of 2.5 cm and a length of 3 cm; Step 5.2: Conduct an oil washing treatment on the cylindrical plug shale sample, and the organic solvent for oil washing is chloroform; Step 5.3: Conduct a drying treatment on the oil-washed cylindrical plug shale sample at a temperature of 105°C for 24 hours.

8. The method for classifying and evaluating shale oil reservoirs according to claim 1, characterized in that, when obtaining the pore volume in different pore size ranges of the sample in Step 5, the different pore sizes respectively refer to: micropores (r < 25 nm), mesopores (25 < r < 100 nm), and macropores (r > 100 nm).

9. The method for classifying and evaluating shale oil reservoirs according to any one of claims 1 - 8, characterized in that, In step 7, classify the shale oil reservoir according to S 1 , TOC, O Mob and Q GF-E ; specifically S calculated according to Step 6 1 , TOC, O Mob and Q GF-E values, the reservoir can be classified into three categories; the specific classification criteria are shown in Table 1; Table 1 When there are contradictions in classifying the shale oil reservoir using the above 4 parameters, classify the shale oil reservoir according to the following principles; For a specific shale sample, four parameters S 1 , TOC, O Mob and Q GF-E corresponding to the sample are scored respectively, and the average value after scoring for the sample is calculated. The type of the shale sample is judged according to the average score. Class I, Class II, and Class III are respectively assigned scores of 1, 2, and 3.

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