Method for determining the primary gas threshold of oil cracking gas generated by different types of hydrocarbon source rocks

Abstract

This invention relates to a method for determining the main gas generation threshold of cracked oil from different types of source rocks. The method is as follows: obtaining source rock samples; conducting high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments in a closed system; performing total organic carbon (TOC) content and kerogen vitrinite reflectance measurements on the thermally simulated solid slag samples from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments; plotting a cross-plot of total organic carbon content and kerogen vitrinite reflectance to obtain the maturity threshold of the main gas generation period; plotting the TOC-... T Cross-plots were used to obtain the temperature threshold for the main gas generation period; the maturity threshold and temperature threshold for the main gas generation period were verified using thermal simulation hydrocarbon production rate curves. This invention uses a "forward modeling" approach to study the main gas generation threshold of source rocks and their derived crude oil, overcoming the application drawbacks of previous "backward modeling" research methods that primarily focused on crude oil.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration technology, specifically relating to a method for determining the main gas generation threshold of cracked gas from different types of source rocks. Background Technology

[0002] With the deepening research into the theory of hydrocarbon generation from kerogen pyrolysis, many scholars have recognized that cracked gas from crude oil is also an important way to generate hydrocarbon gases. Research on the genesis of natural gas has also shifted from focusing primarily on "saprophytic, humic, or mixed types" to focusing more on "kerogen cracked gas or crude oil cracked gas." Furthermore, studies have shown that for saprophytic organic matter, the vast majority of natural gas originates from cracked gas generated from crude oil source rocks, with only a portion originating from cracked gas from kerogen. Similar to the process of kerogen pyrolysis generating oil and gas, the essence of crude oil cracking is the process by which crude oil cracks at a certain temperature, generating gaseous hydrocarbons and residues (solid bitumen). Figure 1 Given the importance of oil cracking gas for natural gas accumulation, research on crude oil cracking into gas has received increasing attention. Among these research questions, the main gas generation threshold of crude oil cracking gas is the most critical scientific issue. This is because the main gas generation threshold determines the distribution of effective cracking gas source stoves, thereby determining the resource potential of cracking gas.

[0003] The hydrocarbon generation and expulsion processes in source rocks exhibit distinct stages. Related studies involve determining key thresholds, such as the early-stage hydrocarbon generation threshold, the mid-stage hydrocarbon expulsion threshold, and the late-stage main gas generation threshold from oil cracking. The hydrocarbon generation threshold refers to the temperature and depth at which significant hydrocarbon generation begins in kerogen, typically determined based on vitrinite reflectance. R o The correspondence with depth is determined. The hydrocarbon expulsion threshold is the critical geological condition at which the source rock's hydrocarbon generation capacity is saturated with various forms of retention, including self-adsorption, water dissolution, oil dissolution, and capillary blockage, and begins to be expelled in large quantities as a free phase. It is commonly referred to as the hydrocarbon expulsion threshold. S 1 / TOC - Depth S 1 / ( S 1+ S 2) Determined by depth cross plot method. The main gas generation threshold of oil cracking gas refers to the temperature and maturity at which early-formed oil begins to crack into gas on a large scale at a higher degree of thermal evolution. It can be determined based on the crude oil thermal simulation gas production rate (or gas conversion rate) curve, which is also the most important method used by predecessors.

[0004] The specific method for determining the main gas production threshold of oil cracking gas based on the crude oil thermal simulation gas production rate (or gas conversion rate) curve is as follows: Figure 2 As shown, the temperature / maturity at the start of the main gas generation period (i.e., the main gas generation threshold of oil cracking gas) is the temperature / vitrein reflectance corresponding to the point where the gas production rate (or gas conversion rate) begins to increase rapidly. Ro The temperature at which the main gas production period ends / maturity is the temperature at which the gas production rate (or gas conversion rate) begins to stabilize. R o Value. This method has many shortcomings: firstly, the gas production rate curve (or gas conversion rate curve) is often a smooth curve, and the inflection point is not obvious. Figure 2 First, the threshold values ​​are usually subject to the subjective judgment of researchers, and the resulting errors are unavoidable. Second, this research approach, which takes crude oil as the main research object, uses thermal simulation gas production rate curves as the basis to determine the main gas generation threshold of cracked gas, and then conducts research on gas source stoves in source rocks, belongs to the "reverse reasoning" research approach. For common mixed-source crude oil and unclear oil and gas source rocks, even if the main gas generation threshold of crude oil cracked gas is determined, subsequent research often cannot be carried out.

[0005] Under natural evolutionary conditions, the total organic carbon (TOC) content of the same source rock increases with the vitrinite reflectance (TOC). R o The increase in TOC should show a continuously decreasing trend. However, during the closed-system thermal simulation experiment on Mesozoic lacustrine source rock samples from the Yin'e Basin, it was found that the TOC of the simulated solid slag sample decreased with... R o The increase in the concentration of hydrocarbons exhibits an abnormal phenomenon of first decreasing and then increasing. In-depth analysis suggests that this anomaly is caused by the cracking of crude oil generated from the source rock. Because the thermal simulation system is a closed system, both liquid and gaseous hydrocarbons generated from the source rock accumulate within the reactor during the simulation. With the increase in temperature (equivalent to an increase in maturity), the crude oil begins to crack and generate gas, simultaneously producing asphalt and coke, thus increasing the TOC of the thermal simulation solid slag sample. Figure 1 The large-scale formation of tar pitch is an important indicator of the beginning of large-scale crude oil cracking and gas generation. The inflection point where TOC changes from decreasing to increasing corresponds to the temperature / R o The value represents the temperature at the start of the main life phase. R o The value is the threshold condition for the main gas generation from the cracking of oil from source rocks. Summary of the Invention

[0006] To address the shortcomings of existing methods that primarily focus on crude oil and rely on thermal simulation gas production rate curves to determine the main gas generation threshold of crude oil cracking gas, this invention provides a method for determining the main gas generation threshold of cracked oil from different types of source rocks.

[0007] The technical solution of this invention is as follows:

[0008] The method for determining the main gas generation threshold of cracked gas from different types of source rocks is as follows: Step 1: Obtain source rock samples; their maturity is <0.7%, and their total organic carbon (TOC) content is ≥0.6%;

[0009] Step 2: Conduct high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments in a closed system on source rock samples;

[0010] Step 3: The total organic carbon (TOC) content and vitrinite reflectance of the thermally simulated solid slag samples from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment were analyzed. R o Measurement and analysis;

[0011] Step 4: Draw TOC - R o Intersection diagram, obtain the maturity threshold of the main gas phase. R o门限 ;Draw TOC- T Intersection diagram, obtain the temperature threshold during the main gas phase. T 门限 .

[0012] in,

[0013] In step 4, TOC- R o In the cross plot, the kerogen vitrinite reflectance corresponds to the inflection point where the total organic carbon (TOC) content increases from a decrease. R o Value is the primary threshold for maturity during the anger period. R o门限 TOC- T In the cross plot, the temperature corresponding to the inflection point where the total organic carbon (TOC) content changes from decreasing to increasing is... T Value is the temperature threshold during the main anger period T 门限 .

[0014] Also includes:

[0015] Step 5: Verify the maturity threshold of the main gas generation period using the thermal simulation hydrocarbon production rate curve obtained from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment. R o门限 and the temperature threshold during the main gas phase T 门限 .

[0016] in,

[0017] The specific process of step 5 is as follows:

[0018] Using kerogen vitrinite reflectance respectively R o and temperature T Using Y as the x-axis and total oil production rate as the y-axis.oil and total gas production rate Y gas Plot the total oil production rate curves on the ordinate. R o -Y oil intersection diagram and T -Y oil Cross plot, plot the total gas production rate curve R o -Y gas intersection diagram and T -Y gas Cross plots are used to verify the maturity threshold of the primary energy generation stage. R o门限 and the temperature threshold during the main gas phase T 门限 .

[0019] in,

[0020] The verification of the maturity threshold of the main gas phase R o门限 and the temperature threshold during the main gas phase T 门限 The specific process is as follows:

[0021] If the total oil production rate curve R o -Y oil intersection diagram and T -Y oil In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total oil production rate curve changes from a slow decrease to a rapid decrease, and the total gas production rate curve... R o -Y gas intersection diagram and T -Y gas In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total gas production rate curve changes from a slow increase to a rapid increase, then the maturity threshold of the main gas production period is... R o门限 and the temperature threshold during the main gas phase T 门限 precise.

[0022] in,

[0023] In step 3, the thermally simulated solid slag sample undergoes wash oil pretreatment before the total organic carbon (TOC) content determination and analysis; kerogen vitrinite reflectance... Ro Before analysis, kerogen separation was performed on the thermally simulated solid residue sample; kerogen vitrin reflectance. R o During the measurement and analysis, no fewer than 30 measurement points should be used, and the average value should be taken as the vitrinite reflectance of the thermally simulated solid slag sample. R o .

[0024] in,

[0025] The specific process of step 2 is as follows: after crushing the source rock sample to below 80 mesh and mixing it evenly, a high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is carried out. After the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is completed, gaseous hydrocarbon products, liquid hydrocarbon products and thermal simulation solid slag samples are collected.

[0026] Specifically:

[0027] The source rock sample is pulverized to below 80 mesh and uniformly mixed, then placed in a high-temperature and high-pressure reactor, and distilled water is added at the same time; the mass ratio of source rock sample to distilled water is 5:1; the high-temperature and high-pressure reactor is sealed; and a high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is carried out in a heating furnace.

[0028] The target temperature for the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is 250°-550°C and the number of target temperatures is greater than or equal to 10. The temperature is increased from room temperature to the target temperature at a heating rate of 5°C / min, and the experiment is terminated after holding the temperature for 24 hours.

[0029] After the high-temperature and high-pressure hydrocarbon generation and emission thermal simulation experiment, hydrocarbon products were discharged from the bottom of the high-temperature and high-pressure reactor in one go. Gaseous and liquid hydrocarbon products were separated by electronic refrigeration and condensation. Gaseous hydrocarbon products were collected by water drainage. Liquid hydrocarbon products were cooled with distilled water, and the liquid hydrocarbons in the distilled water were extracted with dichloromethane, which was recorded as the first discharged oil. The inner wall, pipelines and hydrocarbon discharge valve of the high-temperature and high-pressure reactor were cleaned with dichloromethane, and the liquid hydrocarbons were collected, which was recorded as the second discharged oil. The total discharged oil volume was the first discharged oil volume plus the second discharged oil volume.

[0030] The technical advantages of this invention are as follows:

[0031] This invention employs a forward modeling approach to study the main gas generation threshold of source rocks and their derived crude oil, overcoming the limitations of previous backward modeling methods that primarily focused on crude oil. Furthermore, the method provided by this invention is highly operable and applicable, showing promising prospects for wider application in related research. Attached Figure Description

[0032] Figure 1 A conceptual model for the changes in crude oil composition under different degrees of cracking.

[0033] Figure 2 This is a characteristic curve of a typical crude oil gas conversion rate based on a thermal simulation experiment.

[0034] Figure 3 This is a flowchart illustrating the method of the present invention for determining the main gas generation threshold of cracked oil from different types of source rocks.

[0035] Figure 4 The structural zoning and sampling well distribution map (a) and stratigraphic column (b) of the Yingen-Ejin Banner Basin are shown.

[0036] Figure 5 HI-OI organic matter type discrimination diagram (a) and HI- T max Organic matter type discrimination diagram (b).

[0037] Figure 6 TOC- for solid residue samples in thermal simulation experiments R o Intersection diagram (a) and TOC- T Intersection diagram (b).

[0038] Figure 7 Hydrocarbon production rate for source rock thermal simulation - R o Cross plot (a), hydrocarbon production rate - T Intersection diagram (b). Detailed Implementation

[0039] The method for determining the main gas generation threshold of cracked oil from different types of source rocks is as follows.

[0040] Step 1: Obtaining source rock samples;

[0041] The sample should be the main source rock / gas source rock of a certain study block, and should comprehensively reproduce the hydrocarbon generation and expulsion process of the source rock. The sample maturity should be low, and it should be an immature to low-mature source rock with a maturity of <0.7%; and it should be a source rock with medium or higher organic matter abundance, with a total organic carbon content (TOC) of ≥0.6%.

[0042] Step 2: Conduct high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments in a closed system on source rock samples;

[0043] The source rock sample is pulverized to below 80 mesh and uniformly mixed, then placed in a high-temperature and high-pressure reactor, and distilled water is added at the same time; the mass ratio of source rock sample to distilled water is 5:1; the high-temperature and high-pressure reactor is sealed; and a high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is carried out in a heating furnace.

[0044] The target temperature for the high-temperature, high-pressure hydrocarbon generation and expulsion thermal simulation experiment is 250°C-550°C. Setting more target temperatures is beneficial for subsequent analysis, but too many will increase testing and analysis costs. There should be at least 10 target temperatures, and the intervals between them should be equal, or the target temperatures can be appropriately increased for the main hydrocarbon generation period. For example, with 10 target temperatures, the target temperatures could be 250°C, 300°C, 350°C, 375°C, 400°C, 425°C, 450°C, 475°C, 500°C, and 550°C.

[0045] The room temperature was increased to the target temperature at a heating rate of 5℃ / min, and the temperature was held for 24 hours to end the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment. Each target temperature point was equipped with a high-temperature and high-pressure reactor and a 200mg fragment sample to carry out the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment.

[0046] After the high-temperature and high-pressure hydrocarbon generation and emission thermal simulation experiment, hydrocarbon products were discharged from the bottom of the high-temperature and high-pressure reactor in one go. Gaseous and liquid hydrocarbon products were separated by electronic refrigeration and condensation. Gaseous hydrocarbon products were collected by water drainage. Liquid hydrocarbon products were cooled with distilled water, and the liquid hydrocarbons in the distilled water were extracted with dichloromethane, which was recorded as the first discharged oil. The inner wall, pipelines and hydrocarbon discharge valve of the high-temperature and high-pressure reactor were cleaned with dichloromethane, and the liquid hydrocarbons were collected, which was recorded as the second discharged oil. The total discharged oil volume was the first discharged oil volume plus the second discharged oil volume.

[0047] Step 3: The total organic carbon (TOC) content and vitrinite reflectance of the thermally simulated solid slag samples from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment were analyzed. R o Measurement and analysis;

[0048] After the high-temperature and high-pressure reactors cooled down, thermally simulated solid slag samples were collected from the reactors. Each sample was then divided into two equal parts. One part was used for total organic carbon (TOC) analysis, and the other part was used for kerogen vitrinite reflectance analysis. R o Measurement and analysis;

[0049] The specific determination and analysis of total organic carbon (TOC) content are as follows:

[0050] a. Conduct oil washing pretreatment on thermally simulated solid slag samples;

[0051] b. The total organic carbon (TOC) content was determined and analyzed in accordance with GB / T 19145-2022 "Determination of Total Organic Carbon in Sedimentary Rocks";

[0052] kerogen vitrinite reflectance R o The specific measurements and analyses are as follows:

[0053] a. Perform kerogen separation on thermally simulated solid slag samples;

[0054] b. Determine the vitrinite reflectance of kerogen according to GB / T 6948-1998 "Microscopic Determination of Vitrinite Reflectance of Coal". To reduce error, the number of measurement points should be no less than 30, and the average value should be taken as the vitrinite reflectance of the thermally simulated solid slag sample. R o .

[0055] Step 4: Draw TOC - R o Intersection diagram, obtain the maturity threshold of the main gas phase. R o门限 ;Draw TOC- T Intersection diagram, obtain the temperature threshold during the main gas phase. T 门限 ;

[0056] TOC- R o In the cross plot, the total organic carbon (TOC) content changes with the vitrinite reflectance of kerogen. R o The total organic carbon (TOC) content first decreases and then increases, with the inflection point corresponding to the kerogen vitrinite reflectance. R o Value is the primary threshold for maturity during the anger period. R o门限 ;

[0057] TOC- T In the cross plot, the total organic carbon (TOC) content also changes with temperature. T The total organic carbon (TOC) exhibits a trend of first decreasing and then increasing, with the inflection point corresponding to the change from decreasing to increasing temperature. T Value is the temperature threshold during the main anger period T 门限 .

[0058] Step 5: Verify the maturity threshold of the main gas generation period using the thermal simulation hydrocarbon production rate curve obtained from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment. R o门限 and the temperature threshold during the main gas phase T 门限 The specific process is as follows:

[0059] Using kerogen vitrinite reflectance respectively R o and temperature T Using Y as the x-axis and total oil production rate as the y-axis. oil and total gas production rate Y gas Plot the total oil production rate curves on the ordinate. Ro -Y oil intersection diagram and T -Y oil Cross plot, plot the total gas production rate curve R o -Y gas intersection diagram and T -Y gas Intersection diagram;

[0060] If the total oil production rate curve R o -Y oil intersection diagram and T -Y oil In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total oil production rate curve changes from a slow decrease to a rapid decrease, and the total gas production rate curve... R o -Y gas intersection diagram and T -Y gas In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total gas production rate curve changes from a slow increase to a rapid increase, then the maturity threshold of the main gas production period is... R o门限 and the temperature threshold during the main gas phase T 门限 precise.

[0061] Specific experimental examples

[0062] Taking the main source rocks of the second member of the Lower Cretaceous Bayingobi Formation in the Suhongtu Depression of the Yingen-Ejin Banner Basin as an example, based on the closed-system high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment of low-mature source rock samples and related test analysis data, this invention is used to determine the threshold of the main gas generated by the cracking of oil from the source rocks. The specific steps are as follows:

[0063] Step 1: Obtaining source rock samples;

[0064] The Yingen-Ejin Banner Basin, located in Inner Mongolia Autonomous Region in northwestern China, is a Mesozoic rift basin developed on a Precambrian crystalline block and a Paleozoic folded basement. The Suhongtu Depression (longitude 102°05' ~ 106°10', latitude 40°50' ~ 41°50') is located in the north-central part of the Yingen-Ejin Banner Basin and is a secondary tectonic unit within the basin. Figure 4(a)). The sedimentary infill of the Suhongtu Depression includes the Lower Cretaceous Bayingobi Formation (K1b), Suhongtu Formation (K1s), and Yingen Formation (K1y), as well as the Upper Cretaceous Wulansuhai Formation (K2w) and Cenozoic overburden. The Bayingobi Formation can be divided into three sections, from bottom to top: the first section of the Bayingobi Formation (K1b). 1 ), Bayingobi Formation II (K1b) 2 ) and the third segment of the Bayingobi Formation (K1b) 3 () Figure 4 (b) The second member of the Bayingobi Formation was mainly formed in a deep-lake to semi-deep-lake environment, dominated by fine-grained sediments, forming the main source rocks within the basin. The lithology of the source rocks is mainly dark gray to black mudstone. The samples for this experiment were collected from well H2 in the Suhongtu Depression. The lithology of the samples is dark gray mudstone, and the developed stratigraphic position is K1b. 2 ( Figure 4 (b)).

[0065] Preliminary test and analysis data (Table 1) indicate that the total organic carbon (TOC) content of the source rock samples is 6.05%, and the pyrolysis hydrocarbon generation potential is [not specified]. S 1+ S 2 is 14.34 mg / g, and the chloroform pitch "A" content is 0.3355%. Chloroform pitch "A" δ 13 C PDB The oxygen index (OI) is -28.4‰, the hydrogen index (HI) is 32 mg CO2 / g TOC, and the vitrinite reflectance of kerogen is 222 mg HC / g TOC. R o The pyrolysis peak temperature is 0.56%. T max The temperature was 436℃. According to the Chinese standard for evaluating terrestrial source rocks, the source rock sample was a type II2 low-maturity source rock with extremely high organic matter abundance. Figure 5 (a), Figure 5 (b)).

[0066] Table 1 Basic Geochemical Data of Source Rock Samples

[0067]

[0068] Step 2: Conduct high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments in a closed system on source rock samples;

[0069] To ensure a complete hydrocarbon generation reaction, the sample was pulverized to below 80 mesh and mixed thoroughly. For each temperature point, a pulverized source rock sample, weighing 200 mg per sample, was used. This sample was placed in a high-temperature, high-pressure reactor, along with distilled water at a mass ratio of 5:1. The reactor was then sealed, and a high-temperature, high-pressure hydrocarbon generation and emission thermal simulation experiment was conducted in a heating furnace.

[0070] In the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment, 10 target temperatures were set: 250℃, 300℃, 350℃, 375℃, 400℃, 425℃, 450℃, 475℃, 500℃, and 550℃. Each high-temperature and high-pressure reactor was heated from room temperature to the target temperature at a rate of 5℃ / min. After reaching the target temperature and holding at that temperature for 24 hours, the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment was terminated.

[0071] After the high-temperature and high-pressure hydrocarbon generation and emission thermal simulation experiment, hydrocarbon products were discharged from the bottom of the high-temperature and high-pressure reactor in one go. Gaseous and liquid hydrocarbon products were separated by electronic refrigeration and condensation, and the gaseous hydrocarbon products were collected by water drainage. The collected liquid hydrocarbon products were cooled with distilled water, and the liquid hydrocarbons in the distilled water were extracted with dichloromethane, which was recorded as the first discharged oil. After the high-temperature and high-pressure reactor cooled down, the reactor was opened, and thermal simulation solid slag samples were collected. Thermal simulation solid slag samples at different temperatures represented source rock samples with different degrees of thermal evolution. The inner wall, pipelines, and hydrocarbon discharge valve of the high-temperature and high-pressure reactor were cleaned with dichloromethane, and liquid hydrocarbons were collected, which was recorded as the second discharged oil. The total discharged oil volume was the sum of the first discharged oil volume and the second discharged oil volume.

[0072] Step 3: The total organic carbon (TOC) content and vitrinite reflectance of the thermally simulated solid slag samples from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment were analyzed. R o Measurement and analysis;

[0073] After the high-temperature and high-pressure reactor cools down, collect the thermal simulated solid slag samples inside the high-temperature and high-pressure reactor, and divide the thermal simulated solid slag samples in each high-temperature and high-pressure reactor into two equal parts.

[0074] One of the studies conducted a total organic carbon (TOC) analysis, specifically following GB / T19145-2022 "Determination of Total Organic Carbon in Sedimentary Rocks". The test data are shown in Table 2.

[0075] Table 2 TOC Test Data of Solid Residue Samples in Thermal Simulation Experiment

[0076]

[0077] Another study investigated the vitrinite reflectance of kerogen. R o Measurement and analysis;

[0078] For another sample, kerogen preparation was performed. Kerogen was mixed with a binder, solidified, and shaped into a smooth film. After drying, the film was placed under a ZEISS Axio microscope. The measurement system used was a TIDAS PMT IV photometer and MSP200 testing software. The specific testing procedure followed GB / T 6948-1998, "Microscopic Determination of Vitrin Reflectance of Coal". To ensure data accuracy, at least 30 measurement points were taken for each sample, and the average value was used as the vitrin reflectance of the thermally simulated solid slag sample. R o Specific data are shown in Table 3.

[0079] Table 3 Solid residue samples from thermal simulation experiments R o Test data table

[0080]

[0081] Step 4: Draw TOC - R o Intersection diagram, obtain the maturity threshold of the main gas phase. R o门限 ;Draw TOC- T Intersection diagram, obtain the temperature threshold during the main gas phase. T 门限 ;

[0082] Using the test analysis results obtained in step 3, plot the TOC- R o Intersection diagram and TOC T Intersection diagram ( Figure 6 ). In TOC- R o Intersection diagram ( Figure 6 (a) Total organic carbon (TOC) increases with vitrinite reflectance. R o The total organic carbon (TOC) content first decreases and then increases, with the inflection point corresponding to the change in vitrinite reflectance. R o The value is 1.45%, which is the maturity threshold of the main gas generation stage of the cracked gas from the source rocks in this study. R o门限 It is 1.45%; in TOC- T Intersection diagram ( Figure 6 (b) The total organic carbon (TOC) content also increases with temperature. T The total organic carbon (TOC) exhibits a trend of first decreasing and then increasing, with the inflection point corresponding to the change from decreasing to increasing temperature. T The value is 425℃, which is the temperature threshold for the main gas generation period of the cracked gas from the source rocks in this study. T门限 The temperature is 425℃.

[0083] It also includes an experimental verification section:

[0084] Step 5: Verify the maturity threshold of the main gas generation period using the thermal simulation hydrocarbon production rate curve obtained from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment. R o门限 and the temperature threshold during the main gas phase T 门限 ;

[0085] respectively R o and T Using Y as the x-axis and total oil production rate as the y-axis. oil and total gas production rate Y gas Plot the total oil production rate curves on the ordinate. R o -Y oil intersection diagram and T -Y oil Cross plot, plot the total gas production rate curve R o -Y gas intersection diagram and T -Y gas Intersection diagram, see details Figure 7 ;

[0086] Total oil production rate curve R o -Y oil intersection diagram and T -Y oil In the intersection diagram, R o门限 (1.45%) and T 门限 The point corresponding to (425℃) is basically located at the turning point where the total oil production rate curve changes from a slow decrease to a rapid decrease, and the total gas production rate curve... R o -Y gas intersection diagram and T -Y gas In the intersection diagram, R o门限 (1.45%) and T 门限 The point corresponding to (425℃) is also basically located at the turning point where the total gas production rate curve changes from a slow increase to a rapid increase; the above characteristics indicate that the maturity threshold of the main gas production period... R o门限 and the temperature threshold during the main gas phase T 门限 precise.

Claims

1. A method for determining the main gas generation threshold of cracked oil from different types of source rocks, characterized in that: The method is as follows: Step 1: Obtain source rock samples; maturity < 0.7%, total organic carbon (TOC) content ≥ 0.6%; Step 2: Conduct high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiments in a closed system on source rock samples; Step 3: The total organic carbon (TOC) content and vitrinite reflectance of the thermally simulated solid slag samples from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment were analyzed. R o Measurement and analysis; Step 4: Draw TOC - R o Intersection diagram, obtain the maturity threshold of the main gas phase. R o门限 ; Draw TOC- T Intersection diagram, obtain the temperature threshold during the main gas phase. T 门限 ; Among them, TOC- R o In the cross plot, the kerogen vitrinite reflectance corresponds to the inflection point where the total organic carbon (TOC) content increases from a decrease. R o Value is the primary threshold for maturity during the anger period. R o门限 TOC- T In the cross plot, the temperature corresponding to the inflection point where the total organic carbon (TOC) content changes from decreasing to increasing is... T Value is the temperature threshold during the main anger period T 门限 .

2. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 1, the method further includes step 5: verifying the main gas generation maturity threshold using the thermal simulation hydrocarbon production rate curve obtained from the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment. R o门限 and the temperature threshold during the main life phase T 门限 .

3. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 2, characterized in that: The specific process of step 5 is as follows: Using kerogen vitrinite reflectance respectively R o and temperature T Using Y as the x-axis and total oil production rate as the y-axis. oil and total gas production rate Y gas Plot the total oil production rate curves on the ordinate. R o -Y oil intersection diagram and T -Y oil Cross plot, plot the total gas production rate curve R o -Y gas intersection diagram and T -Y gas Cross plots are used to verify the maturity threshold of the primary energy generation stage. R o门限 and the temperature threshold during the main life phase T 门限 .

4. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 3, characterized in that: The verification of the maturity threshold of the main gas phase R o门限 and the temperature threshold during the main life phase T 门限 The specific process is as follows: If the total oil production rate curve R o -Y oil intersection diagram and T -Y oil In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total oil production rate curve changes from a slow decrease to a rapid decrease, and the total gas production rate curve... R o -Y gas intersection diagram and T -Y gas In the intersection diagram, the maturity threshold of the primary growth period R o门限 and the temperature threshold during the main anger period T 门限 The corresponding point is located at the inflection point where the total gas production rate curve changes from a slow increase to a rapid increase, then the maturity threshold of the main gas production period is... R o门限 and the temperature threshold during the main life phase T 门限 precise.

5. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 4, characterized in that: In step 3, the thermally simulated solid slag sample undergoes wash oil pretreatment before the total organic carbon (TOC) content determination and analysis; kerogen vitrinite reflectance... R o Before analysis, kerogen separation was performed on the thermally simulated solid residue sample; kerogen vitrin reflectance. R o During the measurement and analysis, no fewer than 30 measurement points should be used, and the average value should be taken as the vitrinite reflectance of the thermally simulated solid slag sample. R o .

6. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 5, characterized in that: The specific process of step 2 is as follows: after crushing the source rock sample to below 80 mesh and mixing it evenly, a high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is carried out. After the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is completed, gaseous hydrocarbon products, liquid hydrocarbon products and thermal simulation solid slag samples are collected.

7. The method for determining the main gas generation threshold of cracked oil from different types of source rocks according to claim 6, characterized in that: The source rock sample is pulverized to below 80 mesh and uniformly mixed, then placed in a high-temperature and high-pressure reactor, and distilled water is added at the same time; the mass ratio of source rock sample to distilled water is 5:1; the high-temperature and high-pressure reactor is sealed; and a high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is carried out in a heating furnace. The target temperature for the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is 250°-550°C and there are no fewer than 10 target temperatures. The room temperature is heated to the target temperature at a heating rate of 5°C / min and held at the temperature for 24 hours before the high-temperature and high-pressure hydrocarbon generation and expulsion thermal simulation experiment is terminated. After the high-temperature and high-pressure hydrocarbon generation and emission thermal simulation experiment, hydrocarbon products were discharged from the bottom of the high-temperature and high-pressure reactor in one go. Gaseous and liquid hydrocarbon products were separated by electronic refrigeration and condensation. Gaseous hydrocarbon products were collected by water drainage. Liquid hydrocarbon products were cooled with distilled water, and the liquid hydrocarbons in the distilled water were extracted with dichloromethane, which was recorded as the first discharged oil. The inner wall, pipelines and hydrocarbon discharge valve of the high-temperature and high-pressure reactor were cleaned with dichloromethane, and the liquid hydrocarbons were collected, which was recorded as the second discharged oil. The total discharged oil volume was the first discharged oil volume plus the second discharged oil volume.

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