Method for recovering free hydrocarbon content of different lithologic shale

Abstract

The invention provides a method for recovering free hydrocarbon contents of different lithologic shale. The method comprises the following steps: carrying out closed freezing heat release, freezing pyrolysis and freezing multi-temperature-order pyrolysis experiment test analysis on a closed coring well core; performing freezing pyrolysis experiment test analysis on the core of the non-closed coring well; carrying out pyrolysis experiment test analysis on the multi-courtyard core; determining the lithology type of the shale; and recovering the free hydrocarbon content of the shale according to an experimental test analysis result and the lithology type. According to the method, light hydrocarbon loss can be reduced to the greatest extent, the content of free hydrocarbons in different lithology non-closed coring well samples and placed samples is recovered, and the accuracy of shale oiliness evaluation is improved.

Description

Technical Field

[0001] The present invention belongs to the field of unconventional oil and gas exploration and development, and in particular relates to a method for recovering the free hydrocarbon content of shales of different lithologies. Background Art

[0002] Shale oil exists mainly in mud shale in free and adsorbed states. The free oil S1 content determines the oil content and mobility of shale, and is a key parameter for sweet spot evaluation. Currently, pyrolysis, multi-step pyrolysis, solvent extraction and other methods are mostly used to obtain S1. There are three main problems that lead to the inaccuracy of S1 content. First, the loss of light oil cannot be avoided during the sample pretreatment process, resulting in a seriously low free oil content test result. The disposal process after the core is taken out of the wellbore, the sample storage environment, time, and sample preparation process may cause S1 loss; second, since there is no clear physical and chemical boundary between free oil and bound oil in shale, and there is a certain dynamic transformation, it is difficult to define and accurately quantify it; third, conventional experimental testing methods have limitations. On the one hand, the parameter S1 obtained by conventional pyrolysis is not It can fully represent the free oil content. S2 will also contain a small amount of free oil and adsorbed oil. It is impossible to simply use the pyrolysis parameters S1 and S2 to accurately and quantitatively characterize the content of shale oil in different occurrence states. On the other hand, the solvent extraction method uses different extraction solvents. Due to the differences in the properties of the extraction solvents themselves, the shale oil components obtained by extraction are also different, which cannot represent the original oil content of the shale, making it difficult to distinguish between shale free oil and adsorbed oil. Furthermore, the physical model constructed by molecular simulation cannot quantitatively analyze the impact of the strength of heterogeneity on the pore structure and the differences in the adsorption ratio of shale oil by different mineral components. The model also needs to be calibrated with other experimental data.

[0003] A method for correcting light and heavy hydrocarbons in free hydrocarbons / residual hydrocarbons S1 in pyrolyzed rocks (CN103543470B) discloses: a method for correcting light and heavy hydrocarbons in free hydrocarbons / residual hydrocarbons S1 in pyrolyzed rocks, a key parameter for evaluating shale oil resource potential. To address the problem of light and heavy hydrocarbon loss when evaluating shale oil resources using the S1 method, this technology establishes a correction method for the above-mentioned parameter based on experiments, performs compensation correction on S1 in existing oil field data, and thereby corrects the shale oil resource amount evaluated using the S1 method.

[0004] An analytical method for determining the recovery coefficient of shale pyrolysis parameters (CN104949895B) discloses the following steps: Step 1: Grind a core sample while adding liquid nitrogen; Step 2: Weigh the ground sample and place it in a dedicated crucible for a pyrolyzer, which is then placed in liquid nitrogen; Step 3: Remove the dedicated crucible from the liquid nitrogen and place it in the crucible position for pyrolysis analysis using a pyrolyzer; and Step 4: Allow the same sample to stand at room temperature before performing pyrolysis analysis to obtain the hydrocarbon content lost in conventional pyrolysis analysis, which is used to calculate the recovery coefficient. This analytical method for determining the recovery coefficient of shale pyrolysis parameters reduces the loss of natural gas and light hydrocarbons in the sample and, by comparison with conventional pyrolysis analysis, obtains the recovery coefficient of shale pyrolysis parameters.

[0005] A rapid shale oil resource evaluation method (CN109633778B) discloses: Step A, using kerogen swelling experimental simulations to establish an evolutionary chart of source rock generation, expulsion, and residual hydrocarbons, and calculate the total oil generation, residual hydrocarbons, and expulsion of the depression; Step B, selecting effective parameters such as shale area, effective thickness, density, pyrolysis S1 light hydrocarbon recovery coefficient, and shale oil adsorption coefficient, and calculating shale oil resources using mass oil content. This rapid shale oil resource evaluation method is suitable for shale oil resource calculation, providing support for determining shale oil distribution patterns and ranges, improving exploration results, and providing a practical technical method for more objective and accurate evaluation of shale oil resources, particularly for identifying favorable shale oil enrichment areas and clarifying favorable geological conditions in these areas.

[0006] A method for calibrating and recovering the original hydrocarbon content of shale (CN115541645A) discloses the following steps: Step 1: Establishing the relationship between conventional liquid nitrogen pyrolysis and staged liquid nitrogen pyrolysis, and performing heavy hydrocarbon calibration on the S1 value of conventional liquid nitrogen-frozen shale pyrolysis; Step 2: Calibration of heavy hydrocarbons on the S1 value of pyrolysis of frozen shale; Step 3: Calibration of light hydrocarbons on the S1 value of pyrolysis of frozen shale; Step 4: Establishing calibration models for light and heavy hydrocarbons on the S1 value of pyrolysis of frozen shale and staged liquid nitrogen-frozen shale, as well as models for evaluating adsorbed oil, free oil, and movable oil. This allows the pyrolysis parameter S1 of shale wells to objectively characterize the oil content of the shale, saving experimental testing and analysis time and cost.

[0007] A method for evaluating shale oil content based on different shale facies (CN114755256B) discloses the following: shale facies classification; obtaining pyrolysis parameter values ​​S1 and S2 before oil washing and corresponding pyrolysis parameters S1' and S2' after oil washing for different facies; calculating the recovery coefficient K1 and heavy hydrocarbon correction coefficient K2 for each facies S1; obtaining the hydrocarbon loss coefficient Y for each facies and calculating the hydrocarbon loss amount SH for each facies; and calculating the original total oil content Sc for each facies. Pyrolysis hydrocarbons S1 are recovered for light hydrocarbons and corrected for heavy hydrocarbons, taking into account the different loss rates of hydrocarbon components in different facies at different maturity stages. This method improves the deficiencies of existing methods in calculating the hydrocarbon loss amount SH, resulting in more accurate and less error-prone evaluation of shale oil content.

[0008] A method for recovering heavy hydrocarbons from shale oil in complex tectonic zones based on multi-temperature stage pyrolysis (CN117538362A) discloses: multiple rock samples from the study area are selected for pyrolysis experiments to measure the light hydrocarbon content S1 and heavy hydrocarbon content S2; multi-temperature stage segmented pyrolysis experiments are performed to measure the light oil content S 1-1 , light medium oil content S 1-2 , light and heavy hydrocarbon content S 2-1 and kerogen content S 2-2 Based on the measured results, the heavy hydrocarbon recovery coefficient K2 and the free oil correction coefficient K3 are determined to obtain the recovered shale oil heavy hydrocarbon content, residual free oil content, and adsorbed oil content. This method can establish a shale oil heavy hydrocarbon compensation method for complex structural zones, quickly and effectively recover shale oil content, and provide a basis for shale oil resource calculation.

[0009] A method for determining the free oil content in piedmont-transformed volcanic material-containing mixed sedimentary rocks (CN117554397A) discloses the following steps: selecting volcanic material-containing mud shale samples from a target area, determining the volcanic material content in the samples, and classifying the mud shale samples into different types based on the volcanic material content; restoring the free oil content in the volcanic material-containing mud shale samples; plotting a scatter plot of the movable oil recovery coefficient and volcanic material content in mud shale samples with different volcanic material contents, establishing a numerical model for the volcanic rock and movable oil recovery coefficients, and calculating the free oil content of the samples based on the model.

[0010] A method and apparatus for oil content analysis based on light hydrocarbon recovery from shale (CN118116494A) discloses: obtaining oil content and fine component analysis data from core samples within a shale research area; obtaining oil content and fine component analysis data from conventional rocks within the shale research area; comparing and analyzing the oil content and fine component analysis data from the core samples and conventional rocks to obtain an oil content recovery model for the shale reservoir; and analyzing the oil content of the reservoir within the shale research area based on the recovery model. An experimental method and process for pressure-maintained, sealed cores from shale oil wells, including liquid nitrogen freezing, liquid nitrogen frozen cutting into sections for storage and transportation, liquid nitrogen storage for core cutting, liquid nitrogen sample fragmentation, liquid nitrogen frozen block sampling, and simultaneous oil content S1 and fine component analysis, has been established.

[0011] In their article, "Quantitative Characterization Technology and Application of Shale Oil in Different Occurrence States," published in the November 2016 issue of Experimental Petroleum Geology, Jiang Qigui et al. stated that retained oil in shale occurs in various forms, of which only free oil is the most effective contributor to shale oil production under natural elastic energy recovery. However, there are currently no established methods for quantitatively characterizing the free and adsorbed oil contents in shale and clarifying their relationship with the surrounding medium. This article improves existing Rock-Eval pyrolysis and pyrolysis chromatography methods, combines comparative pyrolysis experiments before and after solvent extraction, and comprehensively analyzes different sample types to establish a quantitative pyrolysis method for shale oil in different occurrence states. Experimental analysis of core samples from shale oil exploration wells in the Jiyang Depression using the newly developed method revealed that the adsorbed oil content in shale is proportional to the abundance of organic matter, while the adsorption-miscibility of kerogen decreases with increasing thermal maturity. Furthermore, the free oil / adsorbed oil ratio within the shale system is negatively correlated with the organic carbon content, indicating that kerogen is not the primary reservoir for liquid free hydrocarbons. Therefore, the developed method can serve as a practical tool for studying the occurrence mechanism of shale oil and for rapidly evaluating the oil content of shale.

[0012] Wang Jun et al., in their article "Calibration Method for the Rock Pyrolysis Parameter S1 Value in the Gulong Shale Oil Reservoir," published in Mud Logging Engineering in June 2022, noted that the Gulong shale oil reservoir is characterized by strong heterogeneity, a high gas-oil ratio, and good fluidity. Therefore, oil content evaluation is the most important component in the comprehensive evaluation of the Gulong shale oil reservoir. However, due to the influence of organic solvent contamination in oil-based drilling fluids and the volatilization and escape of light hydrocarbons, the application of this parameter is currently limited to qualitative evaluation, far from being quantitatively applicable for horizontal comparison. Based on the corresponding relationships between the composite parameter (0.083S2 + 0.1S1) and TOC, as well as S1 and TOC, in the TOC calculation formula of GB / T18602-2012 "Rock Pyrolysis Analysis", a contamination correction method for the S1 value of oil-based drilling fluid cuttings was established. The S1 measured value was first calibrated to water-based drilling fluid conditions, and then a light hydrocarbon volatilization correction was performed. Then, a light hydrocarbon volatilization correction formula was established using reservoir maturity, and the S1 value of the cuttings measured in the water-based drilling fluid system was calibrated to the conditions of conventional cores and pressure-maintained cores, respectively. This achieved quantitative application of this data, thereby solving the problem of accurately evaluating the oil content of shale oil reservoirs in this area.

[0013] Dou Yu et al. published an article entitled "Evaluation of movable resources of lacustrine shale oil based on mass oil content - a case study of the second section of Kongdong sag in Cangdong sag, Bohai Bay Basin" in Volume 41, Issue 1 of the Journal of Shenzhen University (Science and Engineering) in January 2024. The article states that hydrocarbon loss and organic matter adsorption are common in shale samples, resulting in inaccurate evaluation of movable shale oil resources. To solve this problem, 45m closed coring of Well G19-25 in the second section of Kongdong sag in Cangdong sag, Bohai Bay Basin, China was used to innovatively design 45 blocks of three types (0h and 24h, closed and open, conventional and multi-temperature stages) of shale pyrolysis comparative experiments and 12 blocks of kerogen swelling experiments, and constructed light hydrocarbon recovery correction coefficients and organic matter adsorption coefficients. Research shows that the average light hydrocarbon loss rate after 24 hours of shale aging is 29.4%, the average light hydrocarbon loss rate of crushed samples under open conditions is 21.0%, the average light hydrocarbon loss rate of conventional pyrolysis is 15.5%, and the combined average loss rate is 47.1%. This indicates that the amount of retained hydrocarbons in the shale under pristine formation conditions is twice the amount of free hydrocarbons released by conventional pyrolysis (the shale oil light hydrocarbon correction factor is 2.0). The amount of hydrocarbons adsorbed per unit of organic matter in shale gradually decreases with increasing vitrinite reflectance (Ro). When Ro is 0.8% to 1.1%, the amount of oil adsorbed by shale organic matter averages 0.1 (mass fraction). This study establishes a new mass oil content method for evaluating shale oil movable resources. It proposes using shale mass oil content to characterize the amount of movable hydrocarbons in shale after removing organic matter-adsorbed hydrocarbons from retained hydrocarbons. The estimated movable shale oil resource in the Kong 2 Member is 6.8×108 t. This research finding provides a reference for shale oil research in similar basins.

[0014] Lu Shuangfang et al., in their article "Evaluation of the Potential for Shale Oil-Rich Resources in the Fourth Member of the Shahejie Formation in the Damintun Sag of the Liaohe Depression," published in Volume 37, Issue 1 of the Journal of Petroleum & Natural Gas Geology in February 2016, noted that shale oil is characterized by high density, high viscosity, low porosity, and low permeability, making it difficult to extract. Therefore, it is crucial to evaluate resources with relatively high abundance and relatively low extraction difficulty. Using the "three-way" relationship between pyrolysis hydrocarbons (S1) and organic carbon content (TOC), they determined that a TOC greater than 4% was the criterion for shale oil-rich resources in the target area. Pyrolysis hydrocarbons (S1) exhibit light and heavy hydrocarbon losses, necessitating recovery of these hydrocarbons before using them for resource evaluation. Comparative analysis revealed that the cracked hydrocarbons (S2) in shale samples generally decreased after extraction, indicating that S2 includes some residual hydrocarbons that were removed during the chloroform extraction process. The difference ΔS2 between S2 before and after extraction is used to recover heavy hydrocarbons from S1. The heavy hydrocarbon recovery coefficient increases with increasing maturity. Assuming that light hydrocarbons and heavy hydrocarbons are discharged in equal proportions during the hydrocarbon expulsion process, the proportion of each hydrocarbon component generated by shale is evaluated using the principle of hydrocarbon generation dynamics. Then, light hydrocarbons are recovered from S1 based on this proportion. The light hydrocarbon recovery coefficient shows a trend of first decreasing and then increasing with increasing maturity. Based on the well logging evaluation of shale organic matter heterogeneity (TOC and S1), the enriched resources are divided, and the light and heavy hydrocarbon recovery results of S1 are used to evaluate the shale oil enriched resources. The shale oil enriched resources in the E2s4(2) subsection of the Damintun Sag in the Liaohe Depression of the Bohai Bay Basin are approximately 2.2×10 8 t.

[0015] In August 2016, Li Jinbu et al. published an article titled "Correction of light and heavy hydrocarbons by the pyrolysis parameter S1 and its significance: A case study of the E2s4(2) segment in the Damintun Sag of the Bohai Bay Basin" in the 4th issue of Vol. 37 of Petroleum & Natural Gas Geology. The article states that when using the pyrolysis parameter S1 (free hydrocarbon content) to evaluate shale oil resources, there is a phenomenon of light and heavy hydrocarbon loss, which leads to an underestimation of the calculated resource volume. Regarding the loss of heavy hydrocarbons, the S2 (pyrolysis content) obtained from the pyrolysis experiments before and after the extraction of the same shale sample was compared, and the difference between the two was the heavy hydrocarbon content lost by S1. To address light hydrocarbon losses, based on Rock-Eval and PY-GC experiments on immature shale samples and gold tube experiments on crude oil, various kinetic parameters were derived according to chemical kinetics. Combined with the EasyRo model, the ratio of C6-1 to C13+ generated at different maturities was calculated. This ratio was used as the residual C6-13 to C13+ ratio in the source rock. Light hydrocarbon recovery was then performed based on the S1 value after heavy hydrocarbon recovery. Using the S1 value before and after light and heavy hydrocarbon recovery as a shale oil resource evaluation parameter results in significant differences in resource calculations.

[0016] Cao Tingting et al., in their article "Key Technologies for Pyrolysis Analysis of Shale Oil Content," published in Volume 44, Issue 2 of the Journal of Petrolei Sinica in February 2023, noted that rapid quantitative characterization of free and bound oil content in shale is essential for evaluating shale oil content and shale oil mobility. However, current experimental testing techniques still face numerous bottlenecks: ① The inevitable loss of light oil during sample pretreatment results in significantly underestimating free oil content; ② The lack of a clear physicochemical boundary between free and bound oil in shale and the presence of dynamic transformations make it difficult to define and accurately characterize them. To address these challenges, they conducted experimental research and application demonstration on three key technologies for pyrolysis analysis: shale core sample preservation, pretreatment, and shale pyrolysis analysis conditions. This method resulted in a comprehensive pyrolysis analysis method for shale oil content. This method established a process for collecting and cryogenically preserving core samples, developed a sealed frozen sample pretreatment technique, and effectively avoided light oil loss. By optimizing the pyrolysis heating program, they achieved scientific and quantitative characterization of shale oil and bound oil. Currently, this method has been applied, verified and promoted in many oil fields.

[0017] Xue Haitao et al., in their article "Selection and Correction of Key Parameters in Quantitative Evaluation of Shale Oil Resources: A Case Study of the Qingshankou Formation in the Northern Songliao Basin," published in Volume 34, Issue 1 of Unconventional Oil and Gas Resources in 2016, documented that the pyrolysis parameter (S1) is often used to reflect oil content in shale oil resource evaluation. Due to experimental limitations, the measured S1 exhibits a loss of both light and heavy hydrocarbons. To more accurately quantitatively evaluate shale oil resources, this paper investigates the hydrocarbon generation dynamics of organic matter and compares pyrolysis parameters before and after sample extraction. S1 is corrected for light and heavy hydrocarbons to derive the total oil content parameter for the shale. The movable oil content parameter (S1 / TOC) is then determined based on the hydrocarbon expulsion threshold of the shale. The research results show that the S1 of the Qingshankou Formation mud shale in the northern Songliao Basin differs by 293 times before and after correction. The hydrocarbon expulsion threshold corresponds to S1 / TOC = 75 mg / gTOC combined with clay mineral content (characterizing fracturing ability), and the favorable areas for shale oil exploration and development are selected: the favorable areas of the Qing Member are mainly concentrated in the central and northern Qijiagulong Depression and the middle of the Longhupao Da'an Terrace, and the Qing Members 2 and 3 are concentrated in the middle of the Longhupao Da'an Terrace and the central and southern Qijiagulong Depression.

[0018] Luo Chao et al. published an article titled "Evaluation of Shale Oil Content Characteristics by Rock-Sealed Pyrolysis Method - Taking the Da'anzhai Member of the Jurassic System in the Sichuan Basin as an Example" in Volume 34, Issue 1 of "Experimental Petroleum Geology" in July 2022. It states: In order to solve the problem that shale oil content evaluation is limited by the evaporation loss of free hydrocarbons, and considering the purpose of shale oil content evaluation and the need for rapid analysis at the well site, a method for quantitatively evaluating the free hydrocarbon content in rocks by using a rock-sealed pyrolysis method was established based on the combination of low-temperature sealed crushing technology at the well site and the improvement of traditional rock pyrolysis methods. A comparative analysis of shale methods in the Da'anzhai Member of the Jurassic Ziliujing Formation in the Sichuan Basin showed that the rock pyrolysis method yielded S0 values ​​of 0.001-0.046 mg / g and S1 values ​​of 0.8165-4.648 mg / g, while the closed pyrolysis method yielded S0 values ​​of 0.026-0.0984 mg / g and S1 values ​​of 0.113-5.989 mg / g. The S1 values ​​obtained by the closed pyrolysis method are essentially equivalent to those obtained by the rock pyrolysis method, while the S0 values ​​are 1-2 orders of magnitude higher. By improving the heating procedure, the closed pyrolysis method at the wellsite can obtain hydrocarbon content per unit mass of rock under unheated conditions, below 90°C, and at temperatures between 90°C and 300°C. This not only provides richer oil content data but also shortens the testing cycle, meeting the needs of rapid analysis at the wellsite. Combining mud gas logging, shale geochemical parameters, and reservoir fluid properties, the oil content sweet spot of the Da'anzhai Member shale in the study well was evaluated.

[0019] Although the above solution solves some problems, it is still subject to certain limitations in the above background technology when applied to recovering the free hydrocarbon content of shales of different lithologies. Summary of the Invention

[0020] The embodiments of the present application provide a method for recovering the free hydrocarbon content of shale with different lithologies, which can minimize the loss of light hydrocarbons, recover the free hydrocarbon content of non-sealed coring well samples and placed samples with different lithologies, and improve the accuracy of shale oil content evaluation.

[0021] The present invention provides a method for recovering the free hydrocarbon content of shales of different lithologies, comprising:

[0022] Conduct closed-core coring well core testing and analysis of closed-core pyrolysis, frozen-core pyrolysis, and frozen-core multi-temperature-stage pyrolysis experiments;

[0023] Conduct cryo-pyrolysis test and analysis on cores from non-sealed coring wells;

[0024] Conduct pyrolysis test and analysis on the cores placed in multiple wells;

[0025] Determine the lithologic type of shale;

[0026] The free hydrocarbon content of shale is restored based on the experimental test analysis results and lithology type.

[0027] In some embodiments, the closed cryo-pyrolysis, cryo-pyrolysis, and cryo-multi-temperature-stage pyrolysis experiments and analyses of the cores from the closed coring well include:

[0028] After the core of the closed coring well is taken out of the barrel, the sample is divided into several parts and placed in a liquid nitrogen frozen sealed insulation tank for transportation and storage before being sent to the laboratory. The multiple samples are subjected to closed frozen pyrolysis, frozen pyrolysis, and frozen multi-temperature stage pyrolysis experimental test and analysis respectively; the parameters obtained by the closed frozen pyrolysis experimental test and analysis are a continuous heating process. The sample transportation, storage, and preparation are all carried out in a closed environment to obtain gaseous hydrocarbon S g , light hydrocarbons S0, light hydrocarbons S 1-1 , medium-light hydrocarbons S 1-2 The parameters obtained by the frozen pyrolysis experiment test analysis are a continuous heating process, and the light hydrocarbon S1 can be obtained; the parameters obtained by the frozen multi-temperature pyrolysis experiment test analysis are a continuous heating process, and the light hydrocarbon S 1-1 ', medium-light hydrocarbon S 1-2 '.

[0029] In some embodiments, performing cryo-pyrolysis test analysis on cores from non-confined coring wells includes:

[0030] The cores of non-sealed coring wells are of the same core interval as those of sealed coring wells. After the cores of non-sealed coring wells are taken out of the barrel, they are sampled and placed in liquid nitrogen frozen sealed insulation tanks for transportation and storage before being sent to the laboratory. Multiple samples are subjected to cryo-pyrolysis test and analysis. The parameters obtained by the cryo-pyrolysis test and analysis are a continuous heating process, which can obtain light hydrocarbon S 1非 .

[0031] In some embodiments, performing pyrolysis test analysis on multiple raisehole cores includes:

[0032] The cores of wells stored for more than a few days are in the same layer as those of sealed coring wells. The cores of wells stored for more than a few days are sampled and sent to the laboratory for pyrolysis test analysis. The parameters obtained by pyrolysis test analysis are a continuous heating process, which can obtain light hydrocarbon S 1放 .

[0033] In some embodiments, based on experimental test analysis results and lithology type, recovering the free hydrocarbon content of shale includes:

[0034] Use the core of the sealed coring well to establish yieS g +S0+S 1-1 +S 1-2 The relationship with x, i.e. S1, is that the first lithology mud shale y = a1x + b1, where a1 is the coefficient and b1 is the constant;

[0035] Use the core of the closed coring well to establish y1, that is, S 1-1 '+S 1-2'Relationship with x, i.e. S1, the first lithology mud shale y1=a2x+b2, a2 ​​is the coefficient, b2 is the constant;

[0036] In some embodiments, based on experimental test analysis results and lithology type, recovering the free hydrocarbon content of shale includes:

[0037] Using the core of the sealed coring well to establish y2i.e. S g +S0+S 1-1 +S 1-2 'The relationship with x, that is, S1, y2 = y + y1 - x, the first lithology shale y2 = (a1 + a2 - 1) x + b1 + b2.

[0038] In some embodiments, based on experimental test analysis results and lithology type, recovering the free hydrocarbon content of shale includes:

[0039] Using the cores from the sealed coring well and the cores from the non-sealed coring well, establish x=S1 and x1=S 1非 The relationship between the first lithology mud shale x=a3x1+b3, establish y2 that is S g +S0+S 1-1 +S 1-2 ' and x1, that is, S 1非 The relationship between the first lithology mud shale is y2=(a1+a2-1)(a3x1+b3)+b1+b2, where a3 is the coefficient and b3 is the constant;

[0040] In some embodiments, based on experimental test analysis results and lithology type, recovering the free hydrocarbon content of shale includes:

[0041] Using cores from non-sealed coring wells and cores from wells stored for more than several days, we can establish x1, which is S 1非 and x2, that is, S 1放 The relationship between the first lithology mud shale x1=a4x2+b4, establish y2, that is, S g +S0+S 1-1 +S 1-2 ' and x2, that is, S 1放 The relationship between the first lithology shale is y2=(a1+a2-1)(a3a4x2+a3b4+b3)+b1+b2, a4 is the coefficient, and b4 is the constant.

[0042] In a second aspect, the present application provides a method for evaluating the oil content of shale, including any of the above methods for recovering the free hydrocarbon content of shale of different lithologies.

[0043] In a third aspect, the present application provides a method for evaluating shale sweet spots, including any of the above methods for recovering the free hydrocarbon content of shale of different lithologies.

[0044] The method for recovering the free hydrocarbon content of shales of different lithologies in the embodiment of the present application has the following beneficial effects:

[0045] This application can minimize the loss of light hydrocarbons, recover the free hydrocarbon content of non-sealed core well samples and placed samples of different lithologies, and improve the accuracy of shale oil content evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of a method for recovering free hydrocarbon content in shales of different lithologies according to an embodiment of the present application;

[0047] Figure 2 Schematic diagram of free hydrocarbon distribution characteristics of samples from different types of core wells;

[0048] Figure 3a is the relationship between y and x for felsic-clay mixed shale;

[0049] Figure 3b is the relationship between y and x for felsic-limestone mixed shale;

[0050] Figure 3c is the relationship between y and x for clayey-lime-dolomitic mixed shale;

[0051] Figure 4a is the relationship between y1 and x for felsic-clay mixed shale;

[0052] Figure 4b is the relationship between y1 and x for the felsic-limestone mixed shale;

[0053] Figure 4c is the relationship between y1 and x for clayey-lime-dolomitic mixed shale;

[0054] Figure 5a is the relationship between x and x1 for felsic-clay mixed shale;

[0055] Figure 5b is the relationship between x and x1 of felsic-limestone mixed shale;

[0056] Figure 5c is the relationship between x and x1 for clayey-lime-doloitic mixed shale;

[0057] Figure 6a The relationship between x1 and x2 is that of felsic-clay mixed shale;

[0058] Figure 6b is the relationship between x1 and x2 of felsic-limestone mixed shale;

[0059] Figure 6c This is the relationship between x1 and x2 of clayey-limestone mixed shale. DETAILED DESCRIPTION

[0060] The present application will be further described below with reference to the accompanying drawings and embodiments.

[0061] In the following introduction, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The following introduction provides multiple embodiments of the present invention, and different embodiments can be replaced or combined, so this application can also be considered to include all possible combinations of the same and / or different embodiments described. Therefore, if one embodiment contains features A, B, and C, and another embodiment contains features B and D, then this application should also be considered to include embodiments containing one or more of all other possible combinations of features A, B, C, and D, even though the embodiment may not be explicitly described in the following text. In this patent, "mud shale" and "shale" have the same meaning.

[0062] Example 1

[0063] like Figure 1 As shown, the method of the present application for recovering the free hydrocarbon content of mud shales of different lithologies includes: S101, performing closed cryo-pyrolysis, cryo-pyrolysis and cryo-multi-temperature-stage pyrolysis experimental test and analysis on cores from closed coring wells; S103, performing cryo-pyrolysis experimental test and analysis on cores from non-closed coring wells; S105, performing pyrolysis (conventional pyrolysis) experimental test and analysis on cores from multi-wells; S107, determining the lithologic type of the mud shale; S109, recovering the free hydrocarbon content of the mud shale based on the experimental test analysis results and the lithologic type.

[0064] This application can minimize the loss of light hydrocarbons, recover the free hydrocarbon content of non-sealed core well samples and placed samples of different lithologies, and improve the accuracy of shale oil content evaluation.

[0065] Example 2

[0066] like Figure 1 and Figure 2 As shown, the method of recovering the free hydrocarbon content of shales of different lithologies in this application includes:

[0067] The first step is that the core of the H11X well in the Fu 2nd Member of the Gaoyou Sag in the northern Jiangsu Basin is prohibited from being cleaned or wiped after it comes out of the barrel. The core of the closed coring well is sampled immediately at a density of 2 to 3 pieces / meter. No less than 90g of sample is collected at each depth point. The core is divided into three equal parts and placed in a liquid nitrogen frozen sealed insulation tank for transportation and storage to the laboratory. The three samples are respectively subjected to closed frozen pyrolysis, frozen pyrolysis and frozen multi-temperature stage pyrolysis experimental tests and analyses.

[0068] The parameters of the closed freezing pyrolysis experiment are obtained through continuous heating process. The sample transportation, storage and preparation are all carried out in a closed environment. The gaseous hydrocarbon S g(represents the original temperature of the sample is heated to 5℃ and kept at this temperature for 3 minutes to detect the amount of hydrocarbons), light hydrocarbon S0 (represents the amount of S g Then, the temperature was raised to 90℃ at 50℃ / min and kept constant for 5min to detect the amount of hydrocarbons), light hydrocarbon S 1-1 (represents the detection of hydrocarbon content after obtaining S0, heating at 50℃ / min to 200℃ and keeping constant at this temperature for 8 minutes), medium-light hydrocarbon S 1-2 (Represents obtaining S 1-1 Then the temperature was raised at 50°C / min to 300°C and kept constant for 5 min to detect the amount of hydrocarbons.

[0069] The parameters obtained by the frozen pyrolysis experiment test analysis are a continuous heating process, and the light hydrocarbon S1 can be obtained (representing the hydrocarbon amount detected at a starting temperature of 300℃ and a constant temperature of 3 minutes). 1-1 '(represents the starting temperature of 200℃ constant temperature for 1min to detect hydrocarbon quantity), medium-light hydrocarbon S 1-2 '(represents obtaining S 1-1 Then, the temperature was raised at 25°C / min to 350°C and held at that temperature for 1 min to detect the amount of hydrocarbons. Gaseous hydrocarbons, light hydrocarbons, and medium-light hydrocarbons are all considered free hydrocarbons.

[0070] The second step is to prohibit the cleaning and wiping of the core from the non-sealed coring well HY7 of the Fu 2nd Member in the Gaoyou Sag of the Northern Jiangsu Basin (the same coring interval as the sealed coring well) after it comes out of the barrel. The core from the non-sealed coring well is sampled immediately at a density of 2 to 3 pieces per meter. At each depth point, no less than 30g of sample is collected and placed in a liquid nitrogen frozen sealed insulation tank for transportation and storage to the laboratory. The two samples are tested and analyzed by cryo-pyrolysis experiment. The parameters for the cryo-pyrolysis experiment and analysis are a continuous heating process, which can obtain light hydrocarbon S 1非 (Represents the detection of hydrocarbon amount at a starting temperature of 300°C and a constant temperature of 3 minutes).

[0071] The third step is to sample the core of Well SX84 (the same core interval as the sealed core well and the non-sealed core well) in the Fu 2 section of the Gaoyou Sag in the Subei Basin at a density of 2 to 3 pieces per meter, with no less than 30g of sample taken at each depth point, and send it to the laboratory for pyrolysis (ordinary pyrolysis) test and analysis. The parameters for the pyrolysis test and analysis are a continuous heating process, which can obtain light hydrocarbon S 1放 (Represents the detection of hydrocarbon amount at a starting temperature of 300°C and a constant temperature of 3 minutes).

[0072] In the fourth step, whole-rock X-ray diffraction testing was used to determine the content of different mineral components in the shale. The lithologic type of the shale was determined using Chinese Patent 202211179373.0, "A Method for Determining Lithofacies Division Schemes for Continental Mixed Mud Shales." The sampling locations for lithologic analysis were located at the same depth as those for cryo-pyrolysis or pyrolysis testing, providing parallel samples. The study intervals in Wells H11X, HY7, and SX84 contain three types of lithologies: felsic-clay mixed shale, felsic-lime-dolomie mixed shale, and clayey-lime-dolomie mixed shale.

[0073] The fifth step is to use the core of the closed coring well to establish y, that is, S g +S0+S 1-1 +S 1-2 The relationship with x, i.e. S1, is that the first lithology mudstone is y=a1x+b1.

[0074] The linear fitting method was used to establish the y-S curve using the core of the H11X well. g +S0+S 1-1 +S 1-2 The relationship with x, that is, S1, such as Figure 3a 、 Figure 3b 、 Figure 3c As shown, the felsic-clay mixed shale y = 2.0624x-0.6779, the felsic-lime-dolomie mixed shale y = 4.7895x-4.2091, and the clayey-lime-dolomie mixed shale y = -0.2245x+2.3788.

[0075] Step 6: Use the core of the closed coring well to establish y1, that is, S 1-1 '+S 1-2 'The relationship with x, that is, S1, the first lithology mud shale y1=a2x+b2.

[0076] Using the core of the sealed coring well H11X, the y1, that is, S 1-1 '+S 1-2 'The relationship with x, that is, S1, such as Figure 4a 、 Figure 4b 、 Figure 4c As shown, the felsic-clay mixed shale y1 = 0.9611x + 0.5535, the felsic-lime-dolomie mixed shale y1 = 1.3066x - 0.0099, and the clayey-lime-dolomie mixed shale y1 = 1.0341x + 0.3599.

[0077] Step 7: Use the core of the closed coring well to establish y2, that is, S g +S0+S 1-1 +S 1-2 'The relationship with x, that is, S1, y2 = y + y1 - x, the first lithology shale y2 = (a1 + a2 - 1) x + b1 + b2.

[0078] Using the core of the sealed coring well to establish y2i.e. S g +S0+S 1-1 +S 1-2 'The relationship with x, that is, S1, is y2=y+y1-x, for felsic-clay mixed shale, y2=2.0235x-0.1244, for felsic-lime-dolomiaceous mixed shale, y2=5.0961x-4.219, and for clayey-lime-dolomiaceous mixed shale, y2=-0.1904x+2.7387.

[0079] The eighth step is to use the cores of the sealed coring well and the cores of the non-sealed coring well (the same coring interval as the sealed coring well) to establish x=S1 and x1=S 1非 The relationship between the first lithology mud shale x=a3x1+b3, establish y2 that is S g +S0+S 1-1 +S 1-2 ' and x1, that is, S 1非 The relationship between the first lithology shale is y2=(a1+a2-1)(a3x1+b3)+b1+b2.

[0080] Use the cores from the sealed coring well and the cores from the non-sealed coring well (the same coring interval as the sealed coring well) to establish x=S1 and x1=S 1非 relationship, such as Figure 5a 、 Figure 5b 、 Figure 5c As shown, the felsic-clay mixed shale x=0.6072x1+0.8758, the felsic-lime-dolomitic mixed shale x=0.858x1+0.3927, and the clay-lime-dolomitic mixed shale x=0.8375x1+0.8994. We can further establish y2, i.e., S g +S0+S 1-1 +S 1-2 ' and x1, that is, S 1非 The relationship is: felsic-clay mixed shale y2=1.229x1+1.6478, felsic-lime-dolomitic mixed shale y2=4.3724x1-2.2178, clayey-lime-dolomitic mixed shale y2=-0.1595x1+2.5675.

[0081] The ninth step is to use the cores of non-sealed coring wells and cores of wells stored for more than 30 days (the same as the core intervals of sealed coring wells and non-sealed coring wells) to establish x1, that is, S 1非 and x2, that is, S 1放 The relationship between the first lithology mud shale x1=a4x2+b4, establish y2, that is, S g +S0+S 1-1 +S 1-2 ' and x2, that is, S 1放The relationship between the first lithology shale is y2=(a1+a2-1)(a3a4x2+a3b4+b3)+b1+b2.

[0082] Using the cores from non-sealed coring wells and cores from wells stored for more than 30 days (the same core intervals as those from sealed and non-sealed coring wells), establish x1, which is S 1非 and x2, that is, S 1放 relationship, such as Figure 6a , Figure 6b , Figure 6c As shown, the felsic-clay mixed shale x1 = 1.2228x2 + 0.3939, the felsic-lime-dolomitic mixed shale x1 = 1.3983x2 + 0.214, and the clay-lime-dolomitic mixed shale x1 = 1.8769x2 + 0.0348. We can further establish y2, i.e., S g +S0+S 1-1 +S 1-2 ' and x2, that is, S 1放 The relationship is that the felsic-clay mixed shale y2=1.5028x2+2.1319, the felsic-lime-dolomie mixed shale y2=6.1139x2-1.242, and the clayey-lime-dolomie mixed shale y2=-0.2994x2+2.562.

[0083] The method used in this application can comprehensively utilize closed coring and liquid nitrogen freezing methods to conduct thermal release, pyrolysis, and multi-temperature pyrolysis experimental testing and analysis on cores from closed coring wells, cores from non-closed coring wells, and cores from wells that have been stored for more than 30 days, thereby minimizing the loss of free hydrocarbons as much as possible. It comprehensively utilizes multiple testing and analysis methods and multiple types of coring data to restore the free hydrocarbon content of shale, avoiding the inability of a single testing method to fully determine the free hydrocarbon content. Regardless of whether it is liquid nitrogen-frozen samples from non-closed coring wells or stored samples, this method can be used to recover their free hydrocarbon content, with an accuracy improvement of 50 percentage points to 97%. It improves work efficiency and avoids ineffective work, reducing the workload of one person for 10 days to one person for 2 days. It can accurately and efficiently complete the determination of free hydrocarbon content, providing an important basis for further horizontal well target window optimization and efficient development, helping to successfully drill shale oil horizontal wells and meet the needs of exploration and production. The method of this application was applied to the exploration of 13 wells in the Fu 2 section of the Gaoyou-Jinhu Sag in the Northern Jiangsu Basin, with a cumulative production of over 150,000 tons.

[0084] The present application also provides a method for evaluating the oil content of shale, including any of the above methods for recovering the free hydrocarbon content of shale of different lithologies.

[0085] The present application also provides a method for evaluating shale sweet spots, including any of the above methods for recovering the free hydrocarbon content of shale of different lithologies.

[0086] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for recovering the free hydrocarbon content of shales of different lithologies, characterized in that: include: Conduct closed-core coring well core testing and analysis of closed-core pyrolysis, frozen-core pyrolysis, and frozen-core multi-temperature-stage pyrolysis experiments; Conduct cryo-pyrolysis test and analysis on cores from non-sealed coring wells; Conduct pyrolysis test and analysis on cores placed in multiple wells; Determine the lithologic type of shale; The free hydrocarbon content of shale is restored based on the experimental test analysis results and lithology type.

2. The method for recovering free hydrocarbon content in shale of different lithologies according to claim 1, characterized in that: The closed-core coring well cores are tested and analyzed by closed-core pyrolysis, frozen pyrolysis, and frozen multi-temperature-stage pyrolysis experiments, including: After the core of the closed coring well is taken out of the barrel, the sample is divided into several parts and placed in a liquid nitrogen frozen sealed insulation tank for transportation and storage before being sent to the laboratory. The multiple samples are subjected to closed frozen pyrolysis, frozen pyrolysis, and frozen multi-temperature stage pyrolysis experimental test and analysis respectively; the parameters obtained by the closed frozen pyrolysis experimental test and analysis are a continuous heating process. The sample transportation, storage, and preparation are all carried out in a closed environment to obtain gaseous hydrocarbon S g , light hydrocarbons S0, light hydrocarbons S 1-1 , medium-light hydrocarbons S 1-2 The parameters obtained by the frozen pyrolysis experiment test analysis are a continuous heating process, and the light hydrocarbon S1 can be obtained; the parameters obtained by the frozen multi-temperature pyrolysis experiment test analysis are a continuous heating process, and the light hydrocarbon S 1-1 ', medium-light hydrocarbon S 1-2 '.

3. The method for recovering the free hydrocarbon content of shales of different lithologies according to claim 1 or 2, characterized in that: The cryo-pyrolysis test and analysis of cores from non-confined coring wells include: The cores of non-sealed coring wells are of the same core interval as those of sealed coring wells. After the cores of non-sealed coring wells are taken out of the barrel, they are sampled and placed in liquid nitrogen frozen sealed insulation tanks for transportation and storage before being sent to the laboratory. Multiple samples are subjected to cryo-pyrolysis test and analysis. The parameters obtained by the cryo-pyrolysis test and analysis are a continuous heating process, which can obtain light hydrocarbon S 1非 .

4. The method for recovering the free hydrocarbon content of shales of different lithologies according to claim 1 or 2, characterized in that: The pyrolysis test analysis of the multi-well cores includes: The cores of wells stored for more than a few days are in the same layer as those of sealed coring wells. The cores of wells stored for more than a few days are sampled and sent to the laboratory for pyrolysis test analysis. The parameters obtained by pyrolysis test analysis are a continuous heating process, which can obtain light hydrocarbon S 1放 .

5. The method for recovering free hydrocarbon content in shales of different lithologies according to claim 4, characterized in that: Based on the experimental test analysis results and lithology type, the recovery of free hydrocarbon content in shale includes: Use the core of the sealed coring well to establish yieS g +S0+S 1-1 +S 1-2 The relationship with x, i.e. S1, is that the first lithology mud shale y = a1x + b1, where a1 is the coefficient and b1 is the constant; Use the core of the closed coring well to establish y1, that is, S 1-1 '+S 1-2 'The relationship with x, that is, S1, the first lithology mud shale y1=a2x+b2, a2 ​​is the coefficient, and b2 is the constant.

6. The method for recovering free hydrocarbon content in shales of different lithologies according to claim 4, characterized in that: Based on the experimental test analysis results and lithology type, the recovery of free hydrocarbon content in shale includes: Using the core of the sealed coring well to establish y2i.e. S g +S0+S 1-1 +S 1-2 'The relationship with x, that is, S1, y2 = y + y1 - x, the first lithology shale y2 = (a1 + a2 - 1) x + b1 + b2.

7. The method for recovering free hydrocarbon content in shales of different lithologies according to claim 4, characterized in that: Based on the experimental test analysis results and lithology type, the recovery of free hydrocarbon content in shale includes: Using the cores from the sealed coring well and the cores from the non-sealed coring well, establish x=S1 and x1=S 1非 The relationship between the first lithology mud shale x=a3x1+b3, establish y2 that is S g +S0+S 1-1 +S 1-2 ' and x1, that is, S 1非 The relationship between the first lithology shale is y2=(a1+a2-1)(a3x1+b3)+b1+b2, where a3 is the coefficient and b3 is the constant.

8. The method for recovering free hydrocarbon content in shales of different lithologies according to claim 4, characterized in that: Based on the experimental test analysis results and lithology type, the recovery of free hydrocarbon content in shale includes: Using cores from non-sealed coring wells and cores from wells stored for more than several days, we can establish x1, which is S 1非 and x2, that is, S 1放 The relationship between the first lithology mud shale x1=a4x2+b4, establish y2, that is, S g +S0+S 1-1 +S 1-2 ' and x2, that is, S 1放 The relationship between the first lithology shale is y2=(a1+a2-1)(a3a4x2+a3b4+b3)+b1+b2, a4 is the coefficient, and b4 is the constant.

9. A method for evaluating the oil content of shale, characterized in that: The method comprises the method for recovering the free hydrocarbon content of shales of different lithologies according to any one of claims 1 to 8.

10. A method for evaluating shale sweet spots, characterized in that: The method comprises the method for recovering the free hydrocarbon content of shales of different lithologies according to any one of claims 1 to 8.

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