A geochemical identification method for a continental shale oil reservoir assemblage type

Abstract

The application discloses a kind of terrestrial shale oil accumulation combination type geochemical identification method, comprising: according to the observation of fluorescence scanning core and the whole rock analysis of X-ray diffraction experiment, the sample of typical lithofacies in research area and to be evaluated area is selected respectively;Sample is carried out multi-temperature stage pyrolysis experiment, and the content of shale oil under different occurrence states is quantitatively characterized;According to the content of shale oil of sample in research area, establish the geochemical parameter chart of shale oil accumulation combination type identification;Shale oil content of to be evaluated area is projected on geochemical parameter chart;According to the projection result, the shale oil accumulation combination type of to be evaluated area is identified.The geochemical identification chart of series shale oil accumulation combination type used in the application makes full use of multi-temperature stage pyrolysis parameters, contains both quantitative evaluation method of shale oil oiliness, and also contains the remaining hydrocarbon generation potential information of typical lithofacies, can more intuitively and accurately identify the shale oil accumulation combination type of to be evaluated area.

Description

Technical Field

[0001] This invention relates to the field of shale oil resource exploration and development technology, and in particular to a geochemical identification method for continental shale oil reservoir assemblage types. Background Technology

[0002] With the decline in conventional oil and gas production and the advancement of fracturing technology, shale oil has become an important unconventional oil and gas development target. Unlike North American marine shale oil, Chinese continental shale oil is formed and hosted within a variety of lithofacies in mixed fine-grained sediments, such as shale, mudstone, dolomite, and siltstone. Due to the characteristics of these lithofacies—ultra-fine-grained mixed sedimentation, strong heterogeneity, ultra-low porosity and permeability, and nanoscale pore structures—the formation mechanism of shale oil is poorly understood, such as the micro-migration of shale oil (shale, mudstone, dolomite, and siltstone, etc.) between different lithofacies and its role as a source-reservoir-seal complex. In other words, there is a lack of effective understanding and identification methods for "source-reservoir integrated" and "source-reservoir separated" shale oil accumulation assemblages.

[0003] The technology for identifying the types of continental shale oil accumulation assemblages is a relatively blank area in the research on shale oil accumulation and enrichment mechanisms both domestically and internationally. Although significant breakthroughs have been made in the exploration of continental shale oil strata in major basins in China, existing published papers mainly classify the types of continental shale oil accumulation based on factors such as organic matter maturity, lithotexture, and source-reservoir relationships, lacking a clear quantitative method for identifying accumulation assemblages. Summary of the Invention

[0004] The purpose of this invention is to provide a relatively mature, rapid, simple and easy-to-use method for identifying the type of continental shale oil reservoir assemblage.

[0005] Therefore, this invention provides a geochemical identification method for continental shale oil accumulation assemblages, including:

[0006] Based on observations of fluorescent scanning cores and whole-rock analysis by X-ray diffraction experiments, samples of typical lithofacies from the study area and the area to be evaluated were selected respectively.

[0007] The samples were subjected to multi-temperature-level pyrolysis experiments to quantitatively characterize the shale oil content under different occurrence conditions.

[0008] Based on the shale oil content of samples in the study area, a geochemical parameter map for identifying shale oil reservoir assemblage types was established.

[0009] The shale oil content in the area to be evaluated is plotted on the geochemical parameter chart;

[0010] The shale oil reservoir assemblage type in the area to be evaluated is determined based on the sampling results.

[0011] In another aspect, the present invention provides an application of the above-described method in shale oil resource exploration.

[0012] In another aspect, the present invention provides a method for shale oil resource exploration, including: identifying the shale oil reservoir combination type according to the above method.

[0013] In another aspect, the present invention provides a geochemical parameter chart established according to the above method.

[0014] The geochemical identification charts of a series of shale oil reservoir types used in this invention make full use of multi-temperature pyrolysis parameters. They include both quantitative evaluation methods for shale oil oil content and information on the remaining hydrocarbon generation potential of typical lithofacies, enabling more intuitive and accurate identification of shale oil reservoir types in the evaluation area. They have good prospects for widespread application.

[0015] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures described in the written description, claims, and drawings.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0018] Figure 1 This is a flowchart of a specific embodiment of the geochemical identification method for continental shale oil reservoir assemblage types according to the present invention;

[0019] Figure 2 The pyrolysis parameters of the "source-reservoir integrated" shale oil reservoir combination in this embodiment of the invention are adsorbed hydrocarbons + pyrolysis hydrocarbons (S). 2-1 +S 2-2 ) and lithological relationship plate;

[0020] Figure 3 The free hydrocarbons (S) in the "source-reservoir integrated" shale oil reservoir assemblage in this embodiment of the invention. 1-1 +S 1-2 ) and lithological relationship plate;

[0021] Figure 4 The free mobile hydrocarbon S in the "source-reservoir integrated" shale oil reservoir assemblage in this embodiment of the invention. 1-1 With pyrolytic hydrocarbons S 2-2 Relationship diagram;

[0022] Figure 5 The pyrolysis parameters of the "source-reservoir separation" type shale oil reservoir combination in this embodiment of the invention are adsorbed hydrocarbons + pyrolysis hydrocarbons (S 2-1 +S 2-2 ) and lithological relationship plate;

[0023] Figure 6 The free hydrocarbons (S) in the "source-reservoir separation" type shale oil reservoir assemblage in this embodiment of the invention. 1-1 +S 1-2 ) and lithological relationship plate;

[0024] Figure 7 The free mobile hydrocarbon S in the "source-reservoir separation" type shale oil reservoir assemblage in this embodiment of the invention. 1-1 With pyrolytic hydrocarbons S 2-2 Relationship diagram.

[0025] Figure 8 A schematic diagram of Zhao Xianzheng's paper in the prior art;

[0026] Figure 9 A schematic diagram of Li Guoxin's paper in the prior art;

[0027] Figure 10 A schematic diagram of Zhi Dongming's paper in the prior art;

[0028] Figure 11 A simplified technical flowchart of the multi-temperature-level pyrolysis experiment by Jiang Qigui et al. in the existing technology. Detailed Implementation

[0029] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0030] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0031] In their research addressing the aforementioned issues, the inventors discovered that current findings related to the identification of shale oil reservoir assemblages primarily include published papers by Zhao Xianzheng (2020), Li Guoxin (2020), and Zhi Dongming (2019), among others.

[0032] Zhao Xianzheng (2020) et al. pointed out that, such as Figure 8 As shown, based on rock texture, continental shale oil can be classified into layered, mixed, interbedded, and interbedded types; according to the accumulation type of shale oil, shale oil can be classified into stagnant, migrating, and stagnant-migrating types.

[0033] Li Guoxin (2020) et al. pointed out that, such as Figure 9 As shown, based on shale oil maturity, continental shale oil can be divided into two resource types: medium-high maturity and medium-low maturity. Currently, the reservoir types of medium-high maturity shale oil that can be recovered using current technology can be further divided into source-reservoir differentiation type, source-reservoir integrated type, and pure shale type, etc.

[0034] Zhi Dongming (2019) et al. pointed out that, such as Figure 10 As shown, the Lucaogou Formation in the Jimsar Depression of the Junggar Basin is a shale oil assemblage with integrated source and reservoir; while the Fengcheng Formation in the Mahu Depression is a frequently interbedded source and reservoir formation with three assemblage modes: thick "sweet spots" interbedded with thin source rocks, thick source rocks interbedded with thin "sweet spots", and source and reservoir nearly equal thickness interbedded assemblage.

[0035] Crude oil in different geological states exhibits different molecular thermal volatility characteristics. Lower molecular weight oil compounds are more readily released thermally; shale oil in large fractures and pores is more easily pyrolyzed than shale oil in small pores; and free oil is more likely to be released thermally than adsorbed or mixed oil. Therefore, pyrolysis methods can be used for quantitative evaluation of crude oil in different geological states.

[0036] (1) Parameters obtained by the traditional rock-eval method, such as total organic carbon abundance (TOC), free hydrocarbon / oil (S1), and pyrolytic hydrocarbons (S2), are usually used to evaluate the hydrocarbon generation intensity, crude oil mobility, and residual hydrocarbon generation intensity of source rocks. However, the TOC experimental analysis for shale oil is usually carried out without washing the oil, that is, the measured organic carbon content includes both solid kerogen from hydrocarbon generation and crude oil adsorbed on the shale surface, which makes the actual measured TOC value higher than the true value and not suitable as an effective indicator of source rocks. On the other hand, for continental shale oil in China, due to the relatively low maturity, the occurrence state of shale oil is complex. In addition to the free state, adsorbed and miscible shale oil accounts for a large proportion. Therefore, S1 represents the generated and discharged shale oil being lower than the actual value, while S2 represents the residual hydrocarbon generation intensity being higher than the actual value; (2) Jiang Qigui et al. (2016) improved the traditional Rock-Eval pyrolysis method and established a multi-temperature-stage pyrolysis experimental model for shale oil under different occurrence conditions, such as Figure 11 As shown. In short, S was obtained by testing at 200℃, 350℃, 450℃, and 600℃ respectively. 1-1 S 2-1 S2-1 S 2-2 Among them, S 1-1 : Free light oil, representing the actual movable oil content; S 1-2 Free medium / heavy oil; S 2-1 : Adsorbed oil, asphalt, and other high molecular weight hydrocarbons; S 2-2 Hydrocarbon generation from kerogen.

[0037] In addition, the stepwise extraction method established by Qian et al. (2017) is also a relatively effective method for quantitatively characterizing the content of shale oil in different occurrence states. However, due to the environmental pollution caused by the extraction solvent, this technical process does not consider using it.

[0038] To address the above technical problems and provide a relatively mature, rapid, simple, and easy-to-implement method for identifying continental shale oil accumulation assemblages, this invention provides a geochemical identification method for continental shale oil accumulation assemblages, such as... Figure 1 As shown, it includes the following steps:

[0039] Step 1-1: Based on the observation of fluorescence scanning cores and whole-rock analysis by X-ray diffraction (XRD), select samples of typical lithofacies from the study area.

[0040] The selected samples should have typical lithofacies from the vicinity of the same adjacent core, such as shale, mudstone, or dolomite. The lithofacies of the samples include shale, mudstone, and dolomite, and attention should be paid to describing the degree of development of laminae and fractures. All samples should be kept as fresh as possible and free from organic contamination.

[0041] Steps 1-2: Conduct multi-temperature-level pyrolysis analysis on the selected typical lithofacies samples.

[0042] Specifically, multi-temperature-stage pyrolysis experiments were conducted on a Rock-Eval 6 pyrolysis apparatus to obtain a simplified process for shale oil in different occurrence states: starting from 100℃, the temperature was increased to 200℃ at a rate of 25℃ / min, and held at that temperature for 1 min to obtain S. 1–1 Then, the temperature was increased to 350℃ at a rate of 25℃ / min and held at that temperature for 1 minute to obtain S. 1–2 Next, the temperature was increased to 450℃ at a rate of 25℃ / min and held constant for 1 minute to obtain S. 2–1 Finally, the temperature was increased to 600℃ at a rate of 25℃ / min and held constant for 1 minute to obtain S. 2–2 .

[0043] Steps 1-3: Establish geochemical parameter maps for identifying shale oil reservoir types based on the shale oil content.

[0044] Specifically, establish an integrated source and storage system (such as...) Figure 2(as shown in 3, 4) and "source-storage separation" (such as...) Figure 5 Geochemical identification chart of shale oil accumulation assemblages (shown in Figures 6 and 7), including pyrolysis parameters: adsorbed hydrocarbons + pyrolysis hydrocarbons (S... 2-1 +S 2-2 ) and lithological relationship charts, free hydrocarbons (S 1-1 +S 1-2 ) and lithological relationship charts and free mobile hydrocarbons S 1-1 With pyrolytic hydrocarbons S 2-2 Relationship diagram.

[0045] Among them, adsorbed hydrocarbons + pyrolytic hydrocarbons (S 2-1 +S 2-2 The plot of the relationship between lithology and adsorbed hydrocarbons (S) is constructed with typical lithologies of the study area as the abscissa, such as dolomite, mudstone, and shale, and the plot of adsorbed hydrocarbons + pyrolytic hydrocarbons (S) as the axial axis. 2-1 +S 2-2 () is the vertical axis, based on the S of each lithology 2-1 +S 2-2 The trend of change forms the basis of the analysis.

[0046] Among them, free hydrocarbons (S 1-1 +S 1-2 The plot of the relationship between lithology and hydrocarbons was constructed, with typical lithologies of the study area as the abscissa, such as dolomite, mudstone, and shale, and free hydrocarbons (S) as the ordinate. 1-1 +S 1-2 (S) is used as the ordinate, based on the lithology of each lithology. 1-1 +S 1-2 The trend of change is the basis for analysis.

[0047] With variations in lithology (limestone, mudstone, and shale, etc.), shale oil from different hydrocarbon accumulation assemblages exhibits different trends in variation (S). 2-1 +S 2-2 ), (S 1-1 +S 1-2 A diagram showing the relationship between the source and reservoir of shale oil. For the "source-reservoir integrated" shale oil reservoir assemblage type, (S... 2-1 +S 2-2 ) and lithology (e.g.) Figure 2 The above), (S) 1-1 +S 1-2 ) and lithological relationship plates (such as Figure 3 As shown, a coordinated change trend is observed; for the "source-reservoir separation" type of shale oil accumulation combination, (S 2-1 +S 2-2 ) and lithology (e.g.) Figure 5 (as shown), (S) 1-1 +S 1-2 ) and lithological relationship plates (such as Figure 6 As shown, it exhibits a reversal trend.

[0048] Among them, free mobile hydrocarbon S 1-1 With pyrolytic hydrocarbons S 2-2 The plotting of the relationship diagram, based on the pyrolytic hydrocarbon S of typical lithologies in the study area. 2-2 The x-axis represents free mobile hydrocarbon S. 1-1 Using the vertical axis as the ordinate, the multi-temperature pyrolysis experimental data of typical lithologies are projected onto the chart, dividing the chart into three zones: the retention zone, the transition zone, and the accumulation zone.

[0049] Organic matter maturity (Ro) of 0.75% is generally considered the stage at which shale oil begins to drain and migrate, corresponding to S... 1-1 / S 2-2 =10% - 20%. Draw S starting from the origin. 1-1 +S 1-2 With S 2-2 The curve will S 1-1 / S 2-2 <10%, 10%–20%, and >20% are used as the basis for classifying shale oil retention zones, transition zones, and accumulation zones.

[0050] For the "source-reservoir integrated" shale oil accumulation assemblage, the free movable hydrocarbons (S) in typical lithofacies... 1-1 With pyrolytic hydrocarbons S 2-2 Relationship diagrams (such as) Figure 4 As shown), it is mainly distributed in the stagnant zone; for the "source-reservoir separation" type of shale oil accumulation assemblage, the free movable hydrocarbons S in typical lithofacies are mainly distributed in the reservoir area; 1-1 With pyrolytic hydrocarbons S 2-2 Relationship diagrams (such as) Figure 7 As shown in the figure, they are mainly distributed in the transition zone and the agglomeration zone.

[0051] Steps 1-4: Select a series of core samples from the area and strata to be evaluated, ensuring the samples are fresh and uncontaminated. Based on fluorescence scanning core observation and X-ray diffraction (XRD) whole-rock analysis, classify the typical lithofacies types of the area to be evaluated. Perform the same operations as described in Step 1-1 on this series of samples. Proceed to Step 1-5.

[0052] Steps 1-5: Conduct multi-temperature-level pyrolysis experiments on typical lithofacies of the area to be evaluated. Perform the same operations as described in Steps 1-2 on this series of samples to obtain the Ss of the samples. 1–1 S 1–2 S 2–1 and S 2-2 This includes parameters such as the content of light free oil and relatively heavy free oil, the content of adsorbed oil mainly consisting of heavy oil and asphaltenes, and the amount of residual kerogen pyrolysis hydrocarbons. The process then proceeds to steps 1-6.

[0053] Steps 1-6: Plot the multi-temperature-level pyrolysis experimental data of typical lithofacies in the area to be evaluated onto the geochemical identification chart of the hydrocarbon accumulation assemblage established in Steps 1-3, including pyrolysis parameters such as adsorbed hydrocarbons + pyrolysis hydrocarbons (S). 2-1 +S 2-2 ) and lithological relationship charts, free hydrocarbons (S 1-1 +S 1-2 ) and lithological relationship charts and free mobile hydrocarbons S 1-1 With pyrolytic hydrocarbons S 2-2 Relationship charts. Using three charts, the type of shale oil reservoir combination, either "source-reservoir integrated" or "source-reservoir separated," is comprehensively identified in the area to be evaluated.

[0054] The geochemical identification method for continental shale oil reservoir assemblage types in this embodiment of the invention utilizes geochemical parameters (pyrolysis parameters: adsorbed hydrocarbons + pyrolysis hydrocarbons (S...)). 2-1 +S 2-2 ) and lithological relationship charts, free hydrocarbons (S 1-1 +S 1-2 ) and lithological relationship charts and free mobile hydrocarbons S 1-1 With pyrolytic hydrocarbons S 2-2 The relationship diagram is used to evaluate the shale oil reservoir assemblage type.

[0055] This method is based on quantitative characterization from multi-temperature-level pyrolysis experiments, and establishes new evaluation charts such as S. 2-1 +S 2-2 Lithological Relationship Plate, S 1-1 +S 1-2 Lithological Relationship Plate, S 1-1 With S 2-2 The relationship chart compares the differences, trends, and internal correlations of various evaluation parameters among typical lithofacies (shale, mudstone, dolomite, etc.) from the same core, replacing the traditional evaluation parameters S1, S2, and TOC. It clarifies the "source-reservoir-cap" roles of various lithofacies in shale oil accumulation at the core scale, and quickly and accurately identifies "source-reservoir integrated" or "source-reservoir separated" shale oil accumulation combinations.

[0056] This method employs a series of geochemical identification charts for shale oil reservoir assemblages, fully utilizing multi-temperature pyrolysis parameters. It includes both quantitative evaluation methods for shale oil bearing capacity and information on the remaining hydrocarbon generation potential of typical lithofacies, providing a more intuitive and accurate "source-reservoir-seal" role for each lithofacies in shale oil accumulation. This offers geochemical evidence for identifying the shale oil reservoir assemblages in the evaluation area. The method is relatively simple, low-cost, and facilitates rapid evaluation of shale oil reservoir assemblages, making it easier to promote and apply.

[0057] In summary, the method described in this embodiment achieves the following technical effects:

[0058] 1) A new parameter index S for shale oil accumulation combination type was established. 1-1 +S 1-2 S 2-1 +S 2-2 S 2-2 ;

[0059] 2) From the perspective of energy conservation and emission reduction, the advantage lies in reducing the investment in pollution experiments once the hydrocarbon accumulation combination type of the area to be evaluated is clearly identified;

[0060] 3) From a technical perspective, advanced multi-temperature-stage pyrolysis experimental techniques are adopted.

[0061] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A geochemical identification method for continental shale oil reservoir assemblage types, characterized in that, include: Based on observations of fluorescent scanning cores and whole-rock analysis by X-ray diffraction experiments, samples of typical lithofacies from the study area and the area to be evaluated were selected respectively. Multi-temperature-stage pyrolysis experiments were conducted on the samples using a Rock-Eval 6 pyrolysis apparatus to quantitatively characterize the shale oil content under different occurrence states, including the content of free hydrocarbons, adsorbed hydrocarbons, and pyrolytic hydrocarbons. The multi-temperature-stage pyrolysis experiments included: heating from 100℃ to 200℃ at a rate of 25℃ / min, holding at that temperature for 1 min, and measuring the S... 1–1 The temperature was increased to 350℃ at a rate of 25℃ / min and held at that temperature for 1 min to obtain S. 1–2 The temperature was increased to 450℃ at a rate of 25℃ / min and held at that temperature for 1 min to obtain S. 2–1 The temperature was increased to 600℃ at a rate of 25℃ / min and held at that temperature for 1 min to obtain S. 2–2 Among them, S 1-1 : Free light oil content, representing actual movable oil; S 1-2 Content of free medium / heavy oil; S 2-1 The adsorbed oil content is high, consisting of heavy oil and asphaltenes; S 2-2 Residual kerogen pyrolysis hydrocarbon content; Based on the shale oil content of samples in the study area, geochemical parameter maps for identifying shale oil reservoir assemblage types were established, including: maps showing the relationship between pyrolysis parameters, adsorbed hydrocarbons and pyrolysis hydrocarbons and lithology, maps showing the relationship between free hydrocarbons and lithology, and maps showing the relationship between free mobile hydrocarbons and pyrolysis hydrocarbons. Based on multi-temperature pyrolysis experimental data of typical lithologies, the shale oil content in the area to be evaluated was plotted on the geochemical parameter chart. The chart showing the relationship between free mobile hydrocarbons and pyrolytic hydrocarbons was based on S... 1-1 / S 2-2 <10%, 10%–20%, and >20% are divided into: retention zone, transition zone, and accumulation zone; the shale oil reservoir assemblage type of the area to be evaluated is determined based on the point-drop results.

2. The method according to claim 1, characterized in that, The typical lithofacies samples include: shale, mudstone, dolomite, or siltstone.

3. The method according to claim 1 or 2, characterized in that, The selection of the sample includes selecting the sample from an adjacent part of the same core.

4. An application of the method according to any one of claims 1 to 3 in shale oil resource exploration.

5. A method for shale oil resource exploration, characterized in that, include: The method according to any one of claims 1 to 3 is used to identify the shale oil reservoir assemblage type.

6. A geochemical parameter plate established by the method according to any one of claims 1 to 3.

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