Target evaluation method for large and medium-sized oil and gas fields on the basis of geological threshold research

Abstract

The present application provides a kind of source on large and medium-sized oil and gas field target evaluation method based on geologic threshold research, which includes: step 1: typical oil and gas reservoir dissection is carried out;Step 2: the parameter optimization and its characterization of main controlling geologic element of oil and gas accumulation are carried out;Step 3: the evolution analysis of key elements of basin simulation is carried out;Step 4: the correlation fitting of reserve scale and geologic single element of accumulation period is carried out;Step 5: the geologic element threshold condition of source on large and medium-sized oil and gas field formation is analyzed by multiple elements.The source on large and medium-sized oil and gas field target evaluation method based on geologic threshold research establishes the correlation of key single element and oil and gas reserve scale;Based on the single factor analysis result, through the superposition of multiple factors one by one, the relationship between source on large and medium-sized oil and gas reservoir and each geologic condition is qualitatively and quantitatively analyzed, and the intuitive evaluation of geologic threshold condition is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration, and in particular to a target evaluation method for large and medium-sized oil and gas fields above the source based on geological threshold research. Background Art

[0002] Source-upper-type oil and gas reservoirs are characterized by lower generation and upper storage. The primary transport pathway for oil and gas migration and accumulation is vertical transport along source-reservoir faults between the source and reservoir, with no large-scale lateral migration. Most oil and gas reservoirs in basin depressions belong to this type. According to the internationally accepted quantitative classification standard based on reserves, and in accordance with the "Geology and Mineral Resources Industry Standard of the People's Republic of China (DZ / T 0217-2005)", oil and gas fields with reported proven geological reserves ≥ 10 million tons (oil) or 10 billion cubic meters (gas) are defined as large or medium-sized oil and gas fields. Current research on the geological thresholds for the formation and distribution of large and medium-sized oil and gas fields has the following advantages and disadvantages: 1. Research on geological thresholds for oil and gas reservoir formation and distribution reveals the extent and probability of reservoir formation. For example, source rock controls the source of hydrocarbon accumulation. Source rock organic matter must reach a maturity of 0.6% before hydrocarbons can be expelled in various forms, including free hydrocarbons. Therefore, oil and gas reservoirs are influenced by source rock thresholds. Currently, there are many assessments of geological thresholds for reservoir formation, but few studies on the geological thresholds for reserve size formation. Secondly, there are many qualitative descriptions of the relationship between geological factors and reserve size, with few quantitative characterizations. These are mostly qualitative descriptions of "better geological conditions, larger reserves," with occasional quantitative characterizations focusing on the relationship between source rock (resource quantity) and reserve size, lacking systematicity.

[0003] To this end, we invented a new target evaluation method for large and medium-sized oil and gas fields above the source based on geological threshold research, which solved the above technical problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a geological threshold condition for the formation of large and medium-sized oil and gas fields above the source, and to provide a target evaluation method for large and medium-sized oil and gas fields above the source based on geological threshold research to provide evidence for the comprehensive evaluation and optimization of large and medium-sized oil and gas field exploration.

[0005] The purpose of the present invention can be achieved through the following technical measures: a target evaluation method for large and medium-sized oil and gas fields on the source based on geological threshold research, the target evaluation method for large and medium-sized oil and gas fields on the source based on geological threshold research includes: step 1: dissecting a typical oil and gas reservoir; step 2: optimizing and characterizing the parameters of the main geological factors controlling oil and gas accumulation; step 3: analyzing the evolution of key factors in basin simulation; step 4: fitting the correlation between reserve scale and single geological factors during the accumulation period; step 5: conducting a multi-factor comprehensive analysis of the geological factor threshold conditions for the formation of large and medium-sized oil and gas fields on the source.

[0006] The purpose of the present invention can also be achieved by the following technical measures:

[0007] In step 1, based on literature research and data analysis, typical oil and gas reservoirs in the distribution area of ​​source-type oil and gas fields in oil and gas basins are selected for detailed dissection, the basic geological characteristics and reservoir characteristics of oil and gas accumulation are analyzed, the source-reservoir-cap assemblages are divided, the oil and gas sources and their main accumulation periods are determined based on fluid inclusion data, and a big data knowledge base is established for the discovered source-type reserve blocks.

[0008] In step 2, the source-upper type oil and gas reservoirs are mainly vertically transported and accumulated nearby. According to the characteristics of the reservoir, the main controlling factors of its formation are summarized as four parts: source rock, reservoir, source-reservoir gap-cap system and upper cover layer.

[0009] In step 2, the source rock characterization parameters are concentrated on source rock thickness, organic matter maturity, organic matter abundance, and organic matter type. The hydrocarbon generation and expulsion amount increases with the increase of source rock organic matter abundance and organic matter maturity within a certain range. That is, the source rock hydrocarbon generation and expulsion amount is used as a comprehensive characterization parameter of the source rock geological threshold. In general, the oil and gas scale is positively correlated with the source rock hydrocarbon generation and expulsion amount. Mature to high-maturity and high hydrocarbon generation intensity source rocks also form larger oil and gas reservoirs.

[0010] In step 2, the macroscopic characterization parameters of the reservoir are mainly lithofacies characteristics, effective thickness and area. The most direct and quantitative microscopic parameters for reservoir performance are porosity and permeability. The effective volume of the reservoir is used as the comprehensive reservoir characterization parameter. The reservoir size is positively correlated with the effective volume. The formula is:

[0011] V=S×H×φ Formula 1

[0012] Where V is the effective volume of the reserve block (km 2 ×m), S is the oil and gas area of ​​the reserve block (km 2 ), H is the effective thickness of the reserve block (m), and φ is the effective porosity of the reserve block.

[0013] In step 2, the source-reservoir fault-cap system reflects the spatial configuration of the fault zone and various strata from source rock to reservoir. All discovered large and medium-sized oil and gas fields above the source have densely developed source-reservoir faults. Faults are sparse in zones with few or no above-source reservoirs. Above-source reservoirs are mostly distributed in depressions where source rocks are developed in various basins. Oil-source faults are primarily concealed strike-slip faults. Research on strike-slip faults reveals that the structural strain field intensity gradually decreases from deep to shallow layers. From deep to shallow, strike-slip faults are divided into three typical styles: braided, flower-shaped, and step-shaped. The order of fault density and vertical continuity is: braided > flower-shaped > step-shaped.

[0014] In order to facilitate the quantitative evaluation of the relationship between the source-reservoir-interval-cap system and the reserve scale, vertical migration and accumulation units of the reserve scale area are established and divided according to the following principles:

[0015] A: Oil source correlation and paleo-structural restoration during the accumulation period confirm that the oil accumulation occurred nearby and that there was no large-scale lateral migration background.

[0016] B: Determine that the reservoir is not completely filled with analogies;

[0017] C: Determine the scale area based on the sedimentary facies belt;

[0018] D: Determine the scale zone boundary based on edge fracture;

[0019] After dividing the vertical transport and aggregation units, the scale area is analyzed and the vertical transport and aggregation efficiency is calculated; the vertical transport and aggregation efficiency K 垂输 The quantitative evaluation of the vertical source-reservoir intermittent-cap conductivity is as follows:

[0020] K 垂输 =Q 储量 / Q 单元排烃量 Formula 2

[0021] where Q 储量 The proven reserves of each set of reservoirs with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units, Q 排烃量 is the hydrocarbon expulsion volume of source rocks in the vertical migration and accumulation unit;

[0022] Geological analysis and mathematical statistics were carried out to fit the relationship between the vertical conductivity of different fault-caprock combinations between source and reservoir and the mudstone thickness between source and reservoir.

[0023] In step 2, the characterization parameter of the upper cover layer is mainly the thickness of the mudstone cap layer. Combined with the fault pattern in the cap layer, the relationship between the single reserve scale of the oil and gas field above the source with different fault patterns and the thickness of the mudstone cap layer is established.

[0024] In step 3, for the source-reservoir fault-cap system, seismic interpretation technology is used to clarify the fault patterns of different strata in the source-reservoir reservoirs based on the theoretical guidance of the geometric pattern of compression-torsional strike-slip faults. For reservoirs with hydrocarbon source rocks drilled in, the thickness of the mudstone between the source and reservoir and the thickness of the overburden are obtained through rock cuttings logging data. For reservoirs without hydrocarbon source rocks drilled in, in addition to the logging and well logging data, the thickness of seismic data needs to be analyzed and comprehensively determined in combination with the basin structure and the amount of denudation. For the thick mudstone layers confirmed to be developed between the source and reservoir, the compaction trend method is used to restore the thickness during the accumulation period.

[0025] In step 3, for the reservoir, the compaction trend method + BasinMod basin simulation method are combined to restore the physical properties such as porosity and permeability and their evolution. The data of the two methods are comprehensively analyzed to finally clarify the evolution characteristics of the reservoir physical properties.

[0026] In step 3, for the source-reservoir fault-cap system, seismic interpretation technology is used to clarify the fault patterns of different strata in the source-reservoir reservoirs based on the theoretical guidance of the geometric pattern of compression-torsional strike-slip faults. For reservoirs with hydrocarbon source rocks drilled in, the thickness of the mudstone between the source and reservoir and the thickness of the overburden are obtained through rock cuttings logging data. For reservoirs without hydrocarbon source rocks drilled in, in addition to the logging and well logging data, the thickness of seismic data needs to be analyzed and comprehensively determined in combination with the basin structure and the amount of denudation. For the thick mudstone layers confirmed to be developed between the source and reservoir, the compaction trend method is used to restore the thickness during the accumulation period.

[0027] In step 3, for the upper cover layer, the BasinMod basin simulation method is used to restore the evolution of the upper cover layer thickness, and the seismic interpretation technology is used to clarify the fault pattern developed in the cover layer.

[0028] In step 4, based on the typical anatomy of oil and gas reservoirs and the restoration of the characteristics of key factors during the accumulation period, mathematical statistics are used to establish the relationship between the scale of oil and gas reserves and the source rock, reservoir, mudstone thickness of different fault combinations between the source and reservoir, and the thickness of the direct cap rock during the main accumulation period, and the critical geological threshold conditions for the main controlling factors of source-upper-type oil and gas reservoirs to control the distribution of large and medium-sized oil and gas fields are determined; the focus is on establishing the role of source rock, fault and mudstone thickness between the source and reservoir in controlling large and medium-sized oil and gas fields.

[0029] In step 4, for source rocks, through geological and geochemical analysis and thermal evolution simulation, the maturity and hydrocarbon generation and expulsion intensity distribution characteristics of each set of source rocks in the basin are clarified, and the cumulative hydrocarbon generation intensity of the source rocks is superimposed with the discovered above-source oil and gas fields. First, the control of the source rocks on the above-source oil and gas distribution is qualitatively analyzed; using the vertical migration and accumulation units established above as units, the corresponding source rock generation and expulsion volume within the unit is calculated, and the relationship between the organic matter maturity, hydrocarbon generation intensity, and hydrocarbon expulsion volume and the reserve scale is statistically analyzed. According to the boundary line, the value of each parameter is determined when the reserve scale reaches 10 million tons.

[0030] In step 4, for the reservoir, the effective volume of each reserve block in the source oil and gas field during the accumulation period is calculated according to formula (1):

[0031] V=S×H×φ Formula 1

[0032] Where V is the effective volume of the reserve block (km 2 ×m), S is the oil and gas area of ​​the reserve block (km 2 ), H is the effective thickness of the reserve block (m), and φ is the effective porosity of the reserve block;

[0033] Mathematical statistics show that the reserve scale and effective volume are generally positively correlated, and the fitting formula generally has linear characteristics:

[0034] Q 储量 =a×V+b Formula 3

[0035] Where V is the effective volume of the reserve block (km2 ×m), Q 储量 It refers to the proven reserves of each set of reservoirs overlying the source rocks in the vertical migration and accumulation units with reported proven geological reserves ≥ 10 million tons.

[0036] In step 4, for the source-reservoir discontinuity-cap system, the vertical transport efficiency of the vertical migration and accumulation unit is calculated according to formula (2):

[0037] K 垂输 =Q 储量 / Q 单元排烃量 Formula 2

[0038] where Q 储量 The proven reserves of each set of reservoirs with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units, Q 排烃量 is the hydrocarbon expulsion volume of source rocks in this vertical migration and accumulation unit;

[0039] In general, the vertical conductivity of the source-reservoir gap-caprock combination shows a significant exponential negative correlation with the thickness of the mudstone caprock, and the order is network faults > flower-shaped faults > step faults. First, a correlation model between the vertical conductivity and the source-reservoir gap-caprock thickness is fitted:

[0040] K 垂输 =α×e β×h1 Formula 4

[0041] where K is the vertical migration and accumulation efficiency, h1 is the thickness of the mudstone caprock between the source and reservoir, and α and β are both constants related to different fault combination styles such as network, flower-shaped, and step-shaped.

[0042] Based on the above analysis, the hydrocarbon generation and expulsion of source rocks is used as a comprehensive representation parameter of source rock parameters. The functional relationship between reserve scale, vertical transport efficiency of fault-caprock combination, and source rock hydrocarbon expulsion is further constructed. The fault-caprock and source rock linkage threshold for the formation of large and medium-sized oil fields above the source is determined. The functional relationship model between reserve scale, fault-caprock and source rock is:

[0043] Q 储量 =Q 单元排烃量 ×K 垂输 =Q 单元排烃量 ×α×e β×h1 Formula 5

[0044] Where: Q 储量 For proven reserves, 10,000 tons; Q 单元排烃量 : hydrocarbon discharge volume of migration and accumulation unit, ten thousand tons; α, β: coefficients, dimensionless, related to fault pattern; h1: mudstone caprock thickness threshold between source and reservoir, meter.

[0045] In step 4, for the upper cover layer, the correlation between the thickness of the cover layer and the reserve scale of different fault combination styles is established. The boundary phase fitting formula generally has a power characteristic:

[0046] Q 储量 =a×h2 b Formula 6

[0047] Where: Q 储量 is the proven reserves, 10,000 tons; h2 is the thickness of the overlying mudstone cover, meters; a and b are both constants, which are related to different fault combination styles such as network, flower-shaped and step-shaped.

[0048] In step 5, based on the analysis of source rock and reserve size, it was found that oil and gas reserves exhibited different correlations with various factors. The main controlling factors for reaching the size threshold jointly controlled the distribution of large and medium-sized oil fields: effective source rock control area, fault-caprock coupling control layer, and large-scale reservoir control location. ① Large and medium-sized oil reservoirs above the source rock are concentrated in the reservoir system overlying the source rock that has reached the threshold. ② The source-reservoir fault-caprock (mudstone) transport system controls the specific stratigraphic system that the oil and gas reaches. ③ After reaching the overlying strata, the lateral distribution characteristics of the effective reservoirs essentially control the planar distribution of the oil and gas.

[0049] The target evaluation method of large and medium-sized oil and gas fields above the source based on geological threshold research in the present invention systematically analyzes the static accumulation factor characteristics of source-reservoir-fault-caprock of above-source oil and gas reservoirs, restores the key factor characteristics of the oil and gas accumulation period, uses mathematical and statistical analysis technology to reveal the distribution pattern of oil and gas reservoirs in a macroscopic range, and successively establishes the correlation between key single factors such as source rock maturity, hydrocarbon generation intensity, hydrocarbon generation amount, reservoir porosity, effective reservoir volume, thickness of caprocks with different fault styles and oil and gas reserve scale; based on the results of single factor analysis, by superimposing multiple factors one by one, qualitatively and quantitatively analyzes the relationship between large and medium-sized oil and gas reservoirs above the source and various geological conditions, and realizes intuitive evaluation of geological threshold conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a flow chart of a specific embodiment of the method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research of the present invention;

[0051] Figure 2 Schematic diagram of source-reservoir-cap combination characteristics of an above-source oil and gas field in the Junggar Basin in a specific embodiment of the present invention;

[0052] Figure 3 This is a functional relationship diagram of the reserve scale of the above-source oil and gas fields in the Junggar Basin, the vertical conductivity efficiency of the "fault-cap" combination, and the hydrocarbon expulsion rate of the source rock in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the above and other objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings.

[0054] like Figure 1 As shown, Figure 1The present invention is a flow chart of the target evaluation method for large and medium-sized oil and gas fields on the source based on geological threshold research.

[0055] Step 1: Dissection of typical oil and gas reservoirs.

[0056] Based on extensive literature research and data analysis, typical oil and gas reservoirs in the distribution areas of above-source oil and gas fields in oil and gas basins were selected for detailed dissection. The basic geological characteristics and reservoir characteristics of oil and gas accumulation were analyzed, and the source-reservoir-cap assemblages were divided. The sources of oil and gas and their main accumulation periods were determined based on fluid inclusion data. Based on the Access system, the information of each oil and gas field was stored in three forms: "data, map, and text", and a big data knowledge base was established for the discovered above-source reserve blocks.

[0057] Step 2: Optimization and characterization of parameters of the main geological factors controlling oil and gas accumulation.

[0058] The above-source oil and gas reservoirs are mainly vertically transported and accumulated nearby. According to the characteristics of this reservoir, the main controlling factors of its formation are summarized into four parts: source rock, reservoir, source-reservoir gap-cap system and upper cover layer.

[0059] ① Source rock: Source rock characterization parameters focus on source rock thickness, organic matter maturity (Ro), organic matter abundance, and organic matter type. The hydrocarbon generation and expulsion rate increases with the increase of source rock organic matter abundance and maturity within a certain range. That is, the source rock hydrocarbon generation and expulsion rate (Q) is used as a comprehensive characterization parameter of the source rock geological threshold. In general, the oil and gas scale is positively correlated with the source rock hydrocarbon generation and expulsion rate. Mature to highly mature source rocks with high hydrocarbon generation intensity also form larger oil and gas reservoirs.

[0060] ② Reservoir: The macroscopic parameters of reservoirs are mainly lithofacies, effective thickness and area. The most direct and quantitative parameters for reservoir performance are porosity and permeability. This study uses effective reservoir volume as a comprehensive reservoir characterization parameter. The reservoir size is positively correlated with effective volume. The formula is:

[0061] V=S×H×φ Formula 1

[0062] Where V is the effective volume of the reserve block (km 2 ×m), S is the oil and gas area of ​​the reserve block (km 2 ), H is the effective thickness of the reserve block (m), and φ is the effective porosity of the reserve block.

[0063] ③ Source-reservoir fault-cap system: This reflects the spatial configuration of fault zones and various stratigraphic sets from source rock to reservoir. Currently discovered large and medium-sized above-source oil and gas fields all have densely developed source-reservoir faults. Zones with few or no above-source reservoirs have sparse faults. Above-source reservoirs are mostly distributed in depressions where source rocks are developed in various basins. Source faults are primarily concealed strike-slip faults. Research on strike-slip faults reveals a gradual decrease in tectonic strain intensity from deep to shallow. From deep to shallow, strike-slip faults are typically divided into three types: braided, flower-shaped, and step-shaped (Wang Jianwei, 2019). The order of fault density and vertical continuity is: braided > flower-shaped > step-shaped.

[0064] In order to facilitate the quantitative evaluation of the relationship between the source-reservoir-interval-cap system and the reserve scale, vertical migration and accumulation units of the reserve scale area are established and divided according to the following principles:

[0065] A: Oil source correlation and paleo-structural restoration during the accumulation period confirm that the oil accumulation occurred nearby and that there was no large-scale lateral migration background.

[0066] B: Determine that the reservoir is not completely filled with analogies;

[0067] C: Determine the scale area based on the sedimentary facies belt;

[0068] D: Determine the scale zone boundaries based on edge fractures.

[0069] After dividing the vertical migration and accumulation units, the scale area is analyzed and the vertical migration and accumulation efficiency is calculated. The vertical migration and accumulation efficiency (K) is used to quantitatively evaluate the vertical source-reservoir-interval-cap conductivity. The formula is as follows:

[0070] K 垂输 =Q 储量 / Q 单元排烃量 Formula 2

[0071] where Q 储量 The proven reserves of each set of reservoirs with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units, Q 排烃量 is the hydrocarbon expulsion amount of source rocks in this vertical migration and accumulation unit.

[0072] Geological analysis and mathematical statistics were carried out to fit the relationship between the vertical conductivity of different fault-caprock combinations between source and reservoir and the mudstone thickness between source and reservoir.

[0073] ④ Upper cover: The main characterization parameter is the thickness of the mudstone cover. Combined with the fault pattern within the cover, the relationship between the reserve size of a single oil and gas field above the source with different fault patterns and the thickness of the mudstone cover is established.

[0074] Step 3: Evolution analysis of key elements of basin simulation.

[0075] Based on the characterization parameters of the above-mentioned main controlling factors, the time evolution recovery of key elements of oil and gas reservoirs is carried out.

[0076] ① Source Rocks: Hydrocarbon generation and expulsion characteristics are studied based on the changing patterns of source rock generation potential over different geological periods. Based on an established knowledge base of geological element characteristics, the effective source rock series and types for the large and medium-sized above-source oil and gas reservoirs under evaluation are first identified. The thickness, organic matter abundance, type, and maturity of each effective source rock series are then defined. Based on tectonic and sedimentary evolution and constrained by measured geothermal and Ro data, the thermal evolution characteristics of the source rocks are determined. Based on the thermal evolution process, using hydrocarbon yield models and crude oil cracking models, and utilizing Petromod numerical simulation technology, the distribution of hydrocarbon generation and expulsion intensity for each major source rock series throughout the basin during different geological periods is determined. By integrating the expulsion intensity over an area, the hydrocarbon expulsion volume of the source rock in a given area is determined.

[0077] ② Reservoir: Lithology, lithofacies, oil-bearing area, and effective thickness are already known from proven reserves reports. The focus is on restoring the key characteristics of the reservoir during its critical accumulation period. This patent combines the compaction trend method with the BasinMod basin simulation method to restore physical properties such as porosity and permeability and their evolution. A comprehensive analysis of the data from these two methods ultimately defines the evolutionary characteristics of the reservoir physical properties.

[0078] ③ Source-reservoir fault-cap system: Using seismic interpretation technology and guided by the theory of geometric patterns of compression-torsional strike-slip faults, the fault patterns of different strata in the source oil and gas reservoirs are clarified.

[0079] For reservoirs with source rocks drilled into them, the thickness of the mudstone between the source and reservoir and the thickness of the overburden can be determined using cuttings logging data. For reservoirs without source rocks drilled into them, in addition to logging and well data, seismic data analysis combined with basin structure, erosion volume, and other factors are required for comprehensive determination. For thick mudstone layers identified between the source and reservoir, the compaction trend method is used to restore the thickness during the reservoir formation period.

[0080] ④ Upper cover: The BasinMod basin simulation method is mainly used to restore the evolution of the upper cover thickness, and seismic interpretation technology is still used to clarify the fault patterns developed in the cover.

[0081] Step 4: Fit the correlation between reserve size and single geological factor of reservoir formation period.

[0082] Based on the typical anatomy of oil and gas reservoirs and the restoration of key reservoir-forming factors, mathematical statistics were used to establish the relationship between oil and gas reserve size and the source rock, reservoir, mudstone thickness with different fracture patterns between the source and reservoir, and the thickness of the immediate caprock during the main accumulation period. This allowed the identification of the geological threshold critical conditions for the distribution of large and medium-sized oil and gas fields controlled by the main controlling factors of source-above-source reservoirs. The focus was on establishing the role of multiple factors, such as source rock, fractures, and mudstone thickness between the source and reservoir, in controlling large and medium-sized oil and gas fields.

[0083] ① Source rocks: Through geological and geochemical analysis and thermal evolution simulation, the maturity and hydrocarbon generation and expulsion intensity distribution characteristics of each set of source rocks in the basin were clarified. The cumulative hydrocarbon generation intensity of the source rocks was superimposed with the discovered above-source oil and gas fields. The control of the source rocks on the above-source oil and gas distribution was first qualitatively analyzed. Taking the vertical migration and accumulation units established above as units, the hydrocarbon generation and expulsion of the corresponding source rocks within each unit was calculated. The relationship between parameters such as organic matter maturity, hydrocarbon generation intensity, and hydrocarbon expulsion volume and reserve size was statistically analyzed. The values ​​of each parameter when the reserve size reaches 10 million tons were determined based on the boundary line.

[0084] ② Reservoir: Based on the reservoir research in the above steps, the effective volume of each reserve block in the source oil and gas field during the accumulation period is calculated according to formula (1). Mathematical statistics show that the reserve scale and effective volume are generally positively correlated, and the fitting formula generally has a linear characteristic:

[0085] Q 储量 =a×V+b Formula 3

[0086] Where V is the effective volume of the reserve block (km2×m), Q 储量 It refers to the proven reserves of each set of reservoirs overlying the source rocks in the vertical migration and accumulation units with reported proven geological reserves ≥ 10 million tons.

[0087] ③ Source-reservoir fault-cap system: The vertical conductivity of the vertical migration and accumulation unit is calculated according to formula (2). In general, the vertical conductivity of the source-reservoir fault-cap combination is significantly exponentially negatively correlated with the thickness of the mudstone caprock, and the order is network faults > flower-shaped faults > step faults. First, a correlation model between the vertical conductivity and the thickness of the mudstone between the source and reservoir is fitted:

[0088] K 垂输 =α×e β×h1 Formula 4

[0089] where K is the vertical migration and accumulation efficiency, h1 is the thickness of the mudstone caprock between the source and reservoir, and α and β are both constants related to the fault combination pattern.

[0090] Based on the above analysis, the hydrocarbon generation and expulsion of source rocks is used as a comprehensive representation parameter of source rock parameters. The functional relationship between reserve scale, vertical transport efficiency of fault-caprock combination, and source rock hydrocarbon expulsion is further constructed to determine the linkage threshold between "fault-caprock" and source rock for the formation of large and medium-sized oil fields above the source. The functional relationship model between reserve scale, "fault-caprock" and source rock is:

[0091] Q 储量 =Q 单元排烃量 ×K 垂输 =Q 单元排烃量 ×α×e β×h1 Formula 5

[0092] Where: Q 储量 For proven reserves, 10,000 tons; Q 单元排烃量: hydrocarbon discharge volume of migration and accumulation unit, ten thousand tons; α, β: coefficients, dimensionless, related to fault pattern; h1: mudstone caprock thickness threshold between source and reservoir, meter.

[0093] ④ Upper cover: Based on the analysis of the cover in the above steps, the correlation between the thickness of the cover and the reserve size of different fault combination styles is established. The boundary phase fitting formula generally has a power characteristic:

[0094] Q 储量 =a×h2 b Formula 6

[0095] Where: Q 储量 is the proven reserves, 10,000 tons; h2 is the thickness of the overlying mudstone cover, meters; a and b are both constants, which are related to the fault combination pattern.

[0096] Step 5: Comprehensively analyze the geological threshold conditions for the formation of large and medium-sized oil and gas fields at the source.

[0097] Analysis of source rock and reserve size reveals different correlations between oil and gas reserves and various factors. The main controlling factors for reaching the size threshold jointly control the distribution of large and medium-sized oil fields: effective source rock control areas, fault-caprock coupling control layers, and large-scale reservoir location control. ① Large and medium-sized reservoirs above the source rock are concentrated in the reservoir system overlying the source rock that reaches the threshold; ② The source-reservoir fault-caprock (mudstone) transport system controls the specific stratigraphic system that the oil and gas reaches; ③ After reaching the overlying strata, the lateral distribution characteristics of the effective reservoirs essentially control the planar distribution of the oil and gas.

[0098] In a specific embodiment of the present invention, the following steps are included:

[0099] (1) Twenty research materials in five categories, including proven reserve reports, literature, and research results of related topics, were collected. Based on the Access system, a knowledge base of petroleum geological characteristics of 20 discovered oil and gas fields of the above-source type in the Junggar Basin (211 reserve blocks) was established, which can intuitively reflect the source-reservoir-caprock combination characteristics of the above-source type oil and gas fields.

[0100] (2) Optimization and characterization of parameters of the main geological factors controlling oil and gas accumulation.

[0101] ① Source rock: The quality and spatial distribution of the main source rock systems such as P1f, P2w and J1b in the Junggar Basin were determined. ② Reservoir: The source-upper reservoirs in the Junggar Basin are mainly clastic rocks. Multiple sets of sandstone bodies migrated and overlapped, and are widely distributed throughout the basin. The deep and ultra-deep reservoirs in the basin still have good physical properties. The plane distribution characteristics of the sand bodies in the main reservoirs of the source-upper oil and gas fields in the Junggar Basin were clarified. ③ Source-reservoir fault-cap system: Guided by modern compression-torsion structural deformation theory, outcrop, physical model, digital model and seismic analysis techniques were used to clarify that the geometric style of compression-torsion faults is jointly controlled by the dryness of different rock layers (reservoir and cap combination) and the intensity of tectonic activity; theory guides practice, and techniques such as equal time slicing, coherent slicing along layers, and ant body tracking are used to finely interpret seismic data. Figure 2 Three basic combinations of compressional-torsional fault patterns were characterized: "step," "flower," and "net." ④ Upper cover: The Junggar Basin primarily develops four sets of regional cover rocks: T3b, J1, J2x, and K1q. Each set has a thickness of 100-500 m, with a maximum cumulative thickness exceeding 1500 m. These four sets of regional cover rocks overlap and are widely distributed.

[0102] (3) Analysis on the evolution of key elements of basin simulation.

[0103] Based on previous research results, the compaction trend method + BasinMod basin simulation method was used to restore the hydrocarbon evolution characteristics, reservoir properties and paleopressure of 8 sets of source rocks developed in the Junggar Basin.

[0104] (4) Statistical analysis of the reserve scale and geological single factors of the upstream oil and gas fields in the Junggar Basin during the accumulation period.

[0105] Source rock conditions: Large and medium-sized oil and gas fields in the Junggar Basin with a reservoir-forming period of Ro ≥ 0.7% and hydrocarbon generation intensity ≥ 1.5 million tons / km 2 , the hydrocarbon generation in the source area is ≥60 million tons.

[0106] Reservoir conditions: Porosity in normal pressure zone ≥ 15%, porosity in overpressure zone ≥ 12%; According to formula 3, the fitting relationship between reserve scale and effective volume is: Q 储量 =2.8533×V+517.15

[0107] Source-reservoir gap-cap system: Based on the principle of vertical migration and accumulation unit division, 21 migration and accumulation units were divided, including Mahu Sag, Jimusar Sag, Pen-1 Well West Sag and the piedmont belt of the southern margin of the Junggar Basin. Geological analysis and mathematical statistics show that Figure 3The correlation statistics of the vertical conductivity efficiency of the fault-cap and the thickness of the mudstone cap between the source and the reservoir are obtained. The vertical conductivity efficiency of the "fault-cap" combination is: network fault > flower-shaped fault > step fault, which shows an obvious exponential negative correlation with the thickness of the mudstone cap. For the Junggar Basin, in the step fault area, when the mudstone cap thickness is greater than about 500m, it is difficult for oil and gas to be vertically transported; in the flower-shaped fault area, when the mudstone cap thickness is greater than about 1100m, it is difficult for oil and gas to be vertically transported. Based on this, the functional relationship between the reserve scale and the vertical conductivity efficiency of the "fault-cap" combination and the source rock hydrocarbon expulsion volume was constructed, and the relationship between the corresponding vertical migration and accumulation unit hydrocarbon expulsion volume and the source rock thickness when the reserve scale reaches 10 million tons was obtained; the "fault-cap" and source rock linkage threshold for the formation of large and medium-sized oil fields above the source was determined, see Figure 3 , according to formula 5, the fracture style fitting formula is:

[0108] Mesh: Q 储量 =Q 单元排烃量 ×0.2402×e-0.007h1≥10 million tons

[0109] Flower shape: Q 储量 =Q 单元排烃量 ×0.2153×e-0.002h1≥10 million tons

[0110] Step shape: Q 储量 =Q 单元排烃量 ×0.2064×e-0.007h1≥10 million tons

[0111] Cap rock conditions: The development of faults in mudstone will reduce the effectiveness of the cap rock, and the cap rock thickness required to cap the same scale of oil and gas will increase. The correlation between the thickness of the cap rock and the reserve size of different fault pattern combinations is statistically analyzed. The thickness of the cap rock is at least ≥10m. The cap rock thickness required to cap the same scale of reserves is: no fault area < step fault < flower-shaped fault < network fault. According to formula 6, the fitting formula is:

[0112] Reticular fault: Q 储量 =2×10 -6 ×h2 4.8552

[0113] Step fault: Q 储量 =0.1243×h2 2.7571

[0114] No fault zone: Q 储量 =35.928×h2 1.3202

[0115] (5) The threshold conditions for the formation of large and medium-sized oil and gas fields above the source in the Junggar Basin are basically clarified, and the threshold conditions for the formation of large and medium-sized oil and gas fields are quantified. Table 1 shows the threshold conditions for the formation of large and medium-sized oil and gas fields above the source in the Junggar Basin.

[0116] Table 1 Threshold conditions for the formation of large and medium-sized oil and gas fields in the Junggar Basin

[0117]

Claims

1. A target evaluation method for large and medium-sized oil and gas fields above the source based on geological threshold research, characterized by: The target evaluation method for large and medium-sized oil and gas fields above the source based on geological threshold research includes: Step 1: Conduct typical oil and gas reservoir dissection; Based on literature research and data analysis, we selected typical oil and gas reservoirs in the distribution areas of above-source oil and gas fields in oil and gas basins for detailed dissection. We analyzed the basic geological characteristics and reservoir characteristics of oil and gas accumulation, divided the source-reservoir-cap assemblages, determined the oil and gas sources and their main accumulation periods based on fluid inclusion data, and established a big data knowledge base for discovered above-source reserve blocks. Step 2: Optimize and characterize the parameters of the main geological factors controlling oil and gas accumulation; The above-source type oil and gas reservoirs are mainly vertically transported and accumulated nearby. According to the characteristics of this type of reservoir, the main controlling factors of its formation are summarized as four parts: source rock, reservoir, source-reservoir gap-cap system and upper cover. Step 3: Conduct evolution analysis of key elements of basin simulation; For source rocks, the hydrocarbon generation and expulsion characteristics are studied based on the changing patterns of source rock hydrocarbon generation potential during different geological periods. Based on the established knowledge base of geological element characteristics, the effective source rock series and types of large and medium-sized oil and gas reservoirs to be evaluated are first determined. The thickness, organic matter abundance, type, and maturity planar characteristics of each set of effective source rocks are clarified. Based on tectonic sedimentary evolution and constrained by measured geothermal temperature and organic matter maturity Ro data, the thermal evolution characteristics of the source rocks are clarified. Based on the thermal evolution process, based on the hydrocarbon yield model and crude oil cracking model, and using Petromod numerical simulation technology, the distribution of hydrocarbon generation and expulsion intensity of each major source rock series in the entire basin during different geological periods is clarified. By integrating the hydrocarbon expulsion intensity over the area, the hydrocarbon expulsion volume of the source rocks in a certain area can be obtained. Step 4: Fit the correlation between reserve size and single geological factor of reservoir formation period; Based on the typical anatomy of oil and gas reservoirs and the restoration of key accumulation-stage factor characteristics, mathematical statistics were used to establish the relationship between oil and gas reserve size and the source rock, reservoir, mudstone thickness with different fracture combinations between the source and reservoir, and the thickness of the immediate caprock during the main accumulation period. This allowed the determination of the geological threshold critical conditions for the distribution of large and medium-sized oil and gas fields controlled by the main controlling factors of source-above-source oil and gas reservoirs. The focus was on establishing the control of multiple factors such as source rock, fractures, and mudstone thickness between the source and reservoir on large and medium-sized oil and gas fields. Step 5: Comprehensively analyze the geological threshold conditions for the formation of large and medium-sized oil and gas fields at the source; Based on the analysis of source rocks and reserve scale of various factors, it can be seen that oil and gas reserves have different correlations with various factors; the main controlling factors that reach the scale threshold jointly control the distribution of large and medium-sized oil fields: effective source rock controls the area, fault-cap coupling controls the layer, and large-scale reservoir controls the position.

2. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 2, the source rock characterization parameters are concentrated on source rock thickness, organic matter maturity, organic matter abundance, and organic matter type. The hydrocarbon generation and expulsion amount increases with the increase of source rock organic matter abundance and organic matter maturity within a certain range. That is, the source rock hydrocarbon generation and expulsion amount is used as a comprehensive characterization parameter of the source rock geological threshold. In general, the oil and gas scale is positively correlated with the source rock hydrocarbon generation and expulsion amount. Mature to high-maturity and high hydrocarbon generation intensity source rocks also form larger oil and gas reservoirs.

3. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 2, the macroscopic characterization parameters of the reservoir are mainly lithofacies characteristics, effective thickness and area. The most direct and quantitative microscopic parameters for reservoir performance are porosity and permeability. The effective volume of the reservoir is used as the comprehensive reservoir characterization parameter. The reservoir size is positively correlated with the effective volume. The formula is: V = S × H × φ Formula 1 Where: V is the effective volume of the reserve block, km 2 ×m; S is the oil and gas area of ​​the reserve block, km 2 ; H is the effective thickness of the reserve block, m; φ is the effective porosity of the reserve block.

4. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 2, the source-reservoir fault-cap system reflects the spatial configuration of the fault zone and each set of strata from source rock to reservoir. The source-reservoir gaps between large and medium-sized oil and gas fields discovered above the source all have densely developed oil-source faults, while faults are sparse in areas with few or no oil and gas reservoirs above the source. Source-type oil and gas reservoirs are mostly distributed in depressions where source rocks are developed in various basins. Oil-source faults are mainly concealed strike-slip faults. According to the research results of strike-slip faults, the structural strain field intensity gradually decreases from deep to shallow. Strike-slip faults can be divided into three typical styles from deep to shallow: braided, flower-shaped, and step-shaped. The fault density and vertical continuity are: braided > flower-shaped > step-shaped. In order to facilitate the quantitative evaluation of the relationship between the source-reservoir-interval-cap system and the reserve scale, vertical migration and accumulation units of the reserve scale area are established and divided according to the following principles: A: Oil source correlation and paleo-structural restoration during the accumulation period confirm that the oil accumulation occurred nearby and that there was no large-scale lateral migration background. B: Determine that the reservoir is not completely filled with analogies; C: Determine the scale area based on the sedimentary facies belt; D: Determine the scale zone boundary based on edge fracture; After dividing the vertical transport and accumulation units, the scale area is analyzed and the vertical transport efficiency is calculated; the vertical transport efficiency K 垂输 The quantitative evaluation of the vertical source-reservoir intermittent-cap conductivity is as follows: K 垂输 =Q 储量 / Q 单元排烃量 Formula 2 Where: Q 储量 The proven reserves of each set of reservoirs with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units, 10,000 tons; Q 单元排烃量 is the hydrocarbon expulsion volume of source rocks in this vertical migration and accumulation unit, 10,000 tons; Geological analysis and mathematical statistics were carried out to fit the relationship between the vertical conductivity of different fault-caprock combinations between source and reservoir and the mudstone thickness between source and reservoir.

5. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 2, the characterization parameter of the upper cover layer is mainly the thickness of the mudstone cap layer. Combined with the fault pattern in the cap layer, the relationship between the single reserve scale of the oil and gas field above the source with different fault patterns and the thickness of the mudstone cap layer is established.

6. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 3, for the reservoir, the compaction trend method + BasinMod basin simulation method are combined to restore the physical properties such as porosity and permeability and their evolution. The data of the two methods are comprehensively analyzed to finally clarify the evolution characteristics of the reservoir physical properties.

7. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 1, characterized in that: In step 3, for the source-reservoir fault-cap system, seismic interpretation technology is used to clarify the fault patterns of different strata in the source-reservoir reservoirs based on the theoretical guidance of the geometric pattern of compression-torsional strike-slip faults. For reservoirs with hydrocarbon source rocks drilled in, the thickness of the mudstone between the source and reservoir and the thickness of the overburden are obtained through rock cuttings logging data. For reservoirs without hydrocarbon source rocks drilled in, in addition to the logging and well logging data, the thickness of seismic data needs to be analyzed and comprehensively determined in combination with the basin structure and the amount of denudation. For the thick mudstone layers confirmed to be developed between the source and reservoir, the compaction trend method is used to restore the thickness during the accumulation period.

8. The method for evaluating large and medium-sized oil and gas fields above source based on geological threshold research according to claim 1, characterized in that: In step 3, for the upper cover layer, the BasinMod basin simulation method is used to restore the evolution of the upper cover layer thickness, and the seismic interpretation technology is used to clarify the fault pattern developed in the cover layer.

9. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 4, characterized in that: In step 4, for source rocks, through geological and geochemical analysis and thermal evolution simulation, the maturity and hydrocarbon generation and expulsion intensity distribution characteristics of each set of source rocks in the basin are clarified, and the cumulative hydrocarbon generation intensity of the source rocks is superimposed with the discovered oil and gas fields above the source. First, the control of the source rocks on the distribution of oil and gas above the source is qualitatively analyzed; using the vertical migration and accumulation units established above as units, the corresponding source rock generation and expulsion volume within the unit is calculated, and the relationship between the parameters such as organic matter maturity, hydrocarbon generation intensity, and hydrocarbon expulsion volume and the reserve scale is statistically analyzed. According to the boundary line, the value of each parameter is determined when the reserve scale reaches 10 million tons.

10. The method for evaluating large and medium-sized oil and gas fields above source based on geological threshold research according to claim 1, characterized in that: In step 4, for the reservoir, the effective volume of each reserve block in the source oil and gas field during the accumulation period is calculated according to formula (1): V = S × H × φ Formula 1 Where: V is the effective volume of the reserve block, km 2 ×m; S is the oil and gas area of ​​the reserve block, km 2 ; H is the effective thickness of the reserve block, m; φ is the effective porosity of the reserve block; Mathematical statistics show that the reserve scale and effective volume are generally positively correlated, and the fitting formula generally has linear characteristics: Q 储量 =a×V+b Formula 3 Where: V is the effective volume of the reserve block, km 2 ×m;Q 储量 The proven reserves of each reservoir with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units are 10,000 tons.

11. The method for evaluating large and medium-sized oil and gas fields above source based on geological threshold research according to claim 1, characterized in that: In step 4, for the source-reservoir discontinuity-cap system, the vertical transport efficiency of the vertical migration and accumulation unit is calculated according to formula (2): K 垂输 =Q 储量 / Q 单元排烃量 Formula 2 Where: Q 储量 The proven reserves of each set of reservoirs with reported proven geological reserves ≥ 10 million tons overlying the source rocks in the vertical migration and accumulation units, 10,000 tons; Q 单元排烃量 is the hydrocarbon expulsion volume of source rocks in this vertical migration and accumulation unit, 10,000 tons; In general, the vertical conductivity of the source-reservoir gap-caprock combination shows a significant exponential negative correlation with the thickness of the mudstone caprock, and the order is network faults > flower-shaped faults > step faults. First, a correlation model between the vertical conductivity and the source-reservoir gap-caprock thickness is fitted: K 垂输 =α×e β×h1 Formula 4 Among them: K 垂输 is the vertical transport efficiency; h1 is the thickness of the mudstone caprock between the source and reservoir; α and β are both constants, which are related to the different fault combination styles such as network, flower-shaped and step-shaped; Based on the above analysis, the hydrocarbon generation and expulsion of source rocks is used as a comprehensive representation parameter of source rock parameters. The functional relationship between reserve scale, vertical transport efficiency of fault-caprock combination, and source rock hydrocarbon expulsion is further constructed. The fault-caprock and source rock linkage threshold for the formation of large and medium-sized oil fields above the source is determined. The functional relationship model between reserve scale, fault-caprock and source rock is: Q 储量 =Q 单元排烃量 ×K 垂输 =Q 单元排烃量 ×α×e β×h1 Formula 5 Where: Q 储量 For proven reserves, 10,000 tons; Q 单元排烃量 is the hydrocarbon expulsion volume of source rocks in the vertical migration and accumulation unit, 10,000 tons; α, β: dimensionless coefficients related to fault pattern; h1: thickness threshold of mudstone caprock between source and reservoir, meter.

12. The method for evaluating large and medium-sized oil and gas fields above the source based on geological threshold research according to claim 11, characterized in that: In step 4, for the upper cover layer, the correlation between the thickness of the cover layer and the reserve scale of different fault combination styles is established. The boundary phase fitting formula generally has a power characteristic: Q 储量 =c×h2 d Formula 6 Where: Q 储量 is the proven reserves, 10,000 tons; h2 is the thickness of the overlying mudstone cover, meters; c and d are constants, which are related to different fault combination styles such as network, flower-shaped and step-shaped.

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