A method for predicting the oil and gas transport capacity of a composite transport system, trap and probability of accumulation

Abstract

The application discloses a method for predicting the oil and gas transportation capacity of a composite transportation system and the trap accumulation probability, belongs to the technical field of oil exploration, fully considers the whole process from the generation to the migration and accumulation of oil and gas, comprehensively evaluates the hydrocarbon supply capacity of source rocks, the vertical transportation capacity of fractures and the lateral migration capacity of sandstone transportation layers, can accurately and quantitatively evaluate the oil and gas transportation capacity of the fracture-sand body composite transportation system, and the accurate prediction of the oil and gas transportation capacity can effectively predict the trap accumulation probability and the oil and gas field scale, thereby improving the exploration success rate, especially in the low exploration degree area, the application does not need a large amount of drilled well data or the accumulation law of discovered oil and gas fields as prior information, only starts from the geological law to quantitatively study the oil and gas transportation capacity, and then predicts the oil and gas accumulation zone, and improves the success rate of exploration wells.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration technology, specifically to a method for quantitatively evaluating the oil and gas transport capacity of fracture / sand body composite transport systems and predicting the probability of trap formation. Background Technology

[0002] The hydrocarbon transport system refers to the network of channels and dynamic processes through which hydrocarbons migrate from source rocks to reservoirs or traps, acting as a "bridge" connecting source rocks and traps. Its study is crucial for hydrocarbon accumulation prediction and target area selection. Common transport systems include fault-dominated systems, where faults are the main vertical migration channels, especially in areas of intense tectonic activity (such as rift basins and buried hills). For example, in the northern Songliao Basin, hydrocarbons are injected via a combination of large faults and sand bodies. The degree of fracture development within the fault zone affects transport efficiency; if the fault's activity is weak in the later stages, it may act as a barrier rather than a conduit. Sand body-type transport systems utilize highly porosity and permeability sand bodies as the dominant lateral migration pathway, such as the Shahejie Formation sand body coupled with faults in the Bohai Bay Basin. Unconformity transport systems utilize unconformities as lateral migration channels, such as the enrichment of Silurian hydrocarbons along the Ordovician weathering crust unconformity in the Tahe Oilfield. Composite transport systems include fault-sandbody composite systems, such as the Songliao Basin where oil and gas migrate vertically along faults and are laterally distributed through sand bodies; fault-unconformity composite systems, such as the Tazhong area of ​​the Tarim Basin where faults and weathered crust unconformities form a stepped transport system; and sandbody-unconformity composite systems, such as the Bozhong Depression where distant-source oil and gas migrate long distances through sand bodies and regional unconformities. The most common transport system is the fault-sandbody composite system. Faults act as important channels connecting source rocks and reservoirs or transport layers, vertically transporting oil and gas from deep layers to shallower layers, while sand bodies act as lateral transport channels, transporting oil and gas to traps for hydrocarbon accumulation. Faults and sand bodies, as the main channels for oil and gas migration, can be quantitatively evaluated to predict favorable hydrocarbon accumulation areas, providing guidance for oil and gas exploration. Many experts and scholars have conducted related research on oil and gas transport capacity.

[0003] Some scholars predict favorable hydrocarbon accumulation areas by studying the hydrocarbon transport capacity of fractures. Peng Huijie et al. proposed a method for evaluating the probability of fracture-controlled hydrocarbon accumulation. Through research, they found that three parameters—fracture activity rate, fracture plane length, and relative distance between the fracture and the trap—have corresponding mathematical relationships with oilfield reserves (used here to characterize the probability of hydrocarbon accumulation). Based on this, they proposed the probability P of fracture-controlled hydrocarbon accumulation. f This is used to predict the probability of hydrocarbon accumulation.

[0004]

[0005] Among them, P f denoted as , where x is the late-stage activity rate of the fault, and y is the relative distance from the fault to the trap.

[0006] Fu Guang et al., by analyzing the mechanism and influencing factors of fracture-induced hydrocarbon transport capacity, proposed parameters for evaluating fracture-induced hydrocarbon transport capacity. Using these parameters, they predicted favorable hydrocarbon accumulation zones. Their analysis indicated that fracture-induced hydrocarbon transport capacity is related to the development characteristics of the fracture itself (fracture length, dip angle, and number of fractures) and the angle between the fracture and the regional principal compressive stress direction. Therefore, the evaluation parameters for fracture-induced hydrocarbon transport capacity are as follows:

[0007]

[0008] Where T is the evaluation parameter for fracture-guided oil and gas transport capacity; L i To calculate the extension length of the i-th fracture in the mesh; θ i To calculate the dip angle of the i-th fracture in the mesh; n is the number of fractures in the mesh; β i To calculate the angle between the direction of the i-th fracture in the mesh and the direction of the principal compressive stress in the region;

[0009] The above research methods focus on the control effect of fault conductivity on hydrocarbon reservoirs, while neglecting the influence of lateral migration paths. Liu Fangyuan et al. proposed "A Method for Predicting Reservoir Accumulation Probability Based on Evaluation of Hydrocarbon Transport Systems." The main idea is to first classify and evaluate the vertical migration capacity of faults and the lateral migration capacity of sand bodies, then comprehensively assess the hydrocarbon transport efficiency of both, and finally predict the probability of reservoir accumulation. The evaluation parameters for vertical migration capacity include fault displacement at key interfaces, vertical extension length, extension length of key planes, fault plane curvature, fault dip angle, and dip direction. A comprehensive evaluation score (Pv) for vertical migration capacity of faults is established based on these parameters. The evaluation parameters for lateral migration capacity of sand bodies include migration path direction, dip angle, sand-to-soil ratio, sand body thickness, sand body area, porosity, and permeability. A comprehensive evaluation score (Ph) for lateral migration capacity of sand bodies is established. By combining the two migration capacities, the probability of reservoir accumulation is predicted.

[0010] Pg = Pv * Ph

[0011] This invention considers the longitudinal and lateral migration capacity of the transport system and comprehensively considers the properties of faults and sand bodies, thus possessing significant practical value. However, it does not consider the ability of source rocks in the transport system to supply hydrocarbons to faults. Furthermore, porosity and permeability, parameters used to evaluate the lateral migration capacity of sand bodies, cannot be determined in areas with low exploration levels. Therefore, this method is not applicable to areas with low exploration levels.

[0012] The "Prediction Method and System for Effective Transport Path of Fault-Sandbody Transport Combination" proposed by Dou Lirong et al. determined the main source rock layer S i Hydrocarbon expulsion period T Si The main source rock layer S at that time i Conveying sandstone layer A j and fault Fn The paleotectonic map of the fault plane, based on the paleotectonic map, is used to analyze the transport sandstone layer A. j and fault F n Conduct transport path simulation to obtain the transport path M of the fault-sand body transport combination. f Semi-quantitative determination of hydrocarbon transport direction M using geochemical tracer parameters d ; utilizing the oil and gas transport direction M d Verify the transmission path M f To obtain an effective transmission path;

[0013] This invention considers the matching relationship between source rocks and the transport system during the main hydrocarbon expulsion period, and uses the transport direction determined by hydrocarbon tracers as prior information to gradually regress and obtain effective transport paths, providing some indication of hydrocarbon migration direction. However, this method does not consider the transport capacity of faults and sand bodies as transport paths, and can only indicate the transport direction of hydrocarbons as a qualitative judgment, unable to provide quantitative characterization. Furthermore, while using hydrocarbon tracers to determine the transport direction is applicable in mature exploration areas, it cannot be verified in areas with low exploration levels, therefore this method is also unsuitable for areas with low exploration levels. To address these issues, this application proposes a method for predicting the probability of trap formation in areas with high hydrocarbon transport capacity of a composite transport system. Summary of the Invention

[0014] To address the aforementioned problems, this invention provides a method for predicting the probability of hydrocarbon accumulation in traps using the hydrocarbon transport capacity of a composite transport system. This invention is achieved through the following technical solution.

[0015] A method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system includes the following steps:

[0016] S1. Paleotectonic maps of the main source rock S, the source fault F, and the transport layer sandstone C during the hydrocarbon accumulation period;

[0017] S2. The study area was gridded, and the main source rock within the grid was S. ij Oil source fracture

[0018] S3, based on the main source rocks S within the above grid ij and oil source break Paleotectonic maps were used to obtain hydrocarbon supply capacity, using the fracture source index V. ij Characterization;

[0019] S4. Based on the oil source fracture within the above grid. Paleotectonic maps were used to obtain the vertical transport capacity of oil-source faults, and the fault transport index T was used. ij Characterization;

[0020] S5. The fracture source index V calculated based on the above grid. ij and fracture conduction index T ij To obtain the fractured hydrocarbon supply capacity, the fractured hydrocarbon supply index U is used. ij Characterization;

[0021] S6. Based on the paleotectonic map of the sandstone C in the transport layer, obtain the lateral transport capacity of the transport layer and characterize it using the lateral transport index R.

[0022] S7. Based on the matching relationship between faults and sandstone transport layers, analyze the hydrocarbon accumulation mode of the traps;

[0023] S8. Calculate the probability of hydrocarbon accumulation in traps based on fracture hydrocarbon supply index, lateral transport index, and trap accumulation model.

[0024] Further, in step S1, seismic interpretation and tracing are performed on the top and bottom surfaces of the source rock layer, fault plane, and top and bottom surfaces of the sandstone transport layer in the three-dimensional seismic data volume to obtain paleotectonic maps of the source rock S, fault F, and sandstone transport layer C. If the depth domain three-dimensional seismic data volume is used for interpretation and tracing, only depth correction based on the drilled well is required. If the time domain three-dimensional seismic data volume is used for interpretation and tracing, a time domain structural map is obtained. Here, well-seismic calibration is performed first, and then the time-depth conversion relationship is established before converting the time domain structural map into a depth domain structural map.

[0025] Furthermore, in step S2, when the study area is meshed, the mesh size is 800m×800m or 1000m×1000m.

[0026] Furthermore, in step S3, the portion of the main source rock S in the i-th row and j-th column of the grid is S. ij Oil source No. K fractured F k The portion of the grid in the i-th row and j-th column is Oil and gas are generated from the main hydrocarbon source and migrate vertically into shallow strata via source faults. The hydrocarbon supply capacity of source rocks via source faults can be characterized by the volume of source rock units in contact with the source faults, which is defined here as the fault transmission index V. ij That is, the fracture with the source. The main source rock in contact S ij The sum of the volumes of the transport units;

[0027]

[0028] in, For fractures within the grid and through-source fractures The main source rock in contact S ij Contact area To connect with the source fracture The main source rock S ijThe length of the transport unit, θ ij For the source of the fracture With the main source rock S ij The angle between the tendencies of contact, k = 1, 2...n.

[0029] Furthermore, in step S4, the oil source fracture is a "high-speed channel" for oil and gas to migrate to shallow strata. The greater its vertical conduction capacity, the greater the probability of oil and gas accumulation and the higher the oil and gas reservoir filling degree. The vertical conduction capacity of the fracture is related to the permeability of the fracture zone. The greater the permeability, the stronger the vertical conduction capacity. However, the permeability of underground fracture zones is difficult to obtain. The vertical conduction capacity of the fracture can only be reflected by indirect factors.

[0030] Among them, there are four main parameters that can indirectly reflect the permeability of fault zones: the activity of the fault during the hydrocarbon accumulation period, the effective width of the fault ridge, the geometric characteristics of the fault, and the tensile and compressive properties. High fault activity during the hydrocarbon accumulation period easily forms high-permeability zones, and oil and gas preferentially migrate upward along the fault zone. When oil and gas migrate vertically along the fault surface, they preferentially migrate along the fault ridge. Therefore, the size of the fault ridge reflects the scale of the fault space development. The wider the ridge, the stronger the permeability and conduction capacity of the fault. The geometric characteristics of the fault mainly refer to the dip angle. The larger the dip angle, the steeper the fault, and the steeper the fracture induced by the fault zone. Oil and gas migrate upward along the fault. The greater the component force on the fracture surface, the easier it is for oil and gas to migrate upwards. The tensile and compressive properties of a fracture are mainly reflected by the angle between the fracture strike and the principal compressive stress in the region, representing the degree of opening of the fracture zone. When the angle between the fracture strike and the principal compressive stress is 90°, the fracture zone is mainly compressive, with a high degree of closure, the smallest transport space formed, and the weakest permeability, making it difficult for oil and gas to migrate upwards. When the angle between the fracture strike and the principal compressive stress is 0°, the fracture zone is mainly tensile, with a high degree of opening and the strongest permeability, making it easier for oil and gas to migrate upwards. The vertical transport index of a fracture can be quantitatively calculated using the following two formulas:

[0031]

[0032] in The growth index of oil-source faults during the reservoir formation period within the grid is used to characterize the intensity of oil-source fault activity during the reservoir formation period. It is defined as the ratio of the thickness of the downthrown block to the thickness of the upthrown block in the same stratigraphic unit on both sides of the fault. Let H be... k Uij H represents the thickness of the uplifted block of the strata during the hydrocarbon accumulation period of fault k within the grid. k Dij The thickness of the downthrown block during the hydrocarbon accumulation period of fault k within the grid;

[0033] The effective ridge width of fracture k within the grid. The dip angle of fracture k within the grid. The angle between the direction of fracture k within the grid and the principal compressive stress in the region.

[0034] Furthermore, in step S5, the fault source-supply index and the fault vertical transport index within the grid characterize the vertical hydrocarbon supply capacity of source-supplying faults that match the hydrocarbon source, determining the material basis for oil and gas accumulation in traps. Using the fault hydrocarbon supply index, the fault hydrocarbon supply index within each grid can be calculated, thereby quantitatively analyzing the vertical hydrocarbon supply capacity of oil source faults in the study area. The fault hydrocarbon supply index U... ij The calculation formula is as follows:

[0035] U ij =V ij ·T ij

[0036] Calculate the comprehensive evaluation index U within each grid. ij Afterwards, interpolation calculations can be performed on the plane. Kriging interpolation or inverse distance weighted interpolation is generally used here. Finally, the contour map of the fault hydrocarbon supply index in the study area is drawn. This step can generally be completed by geological drawing software such as Petrel or DoubleFox.

[0037] Furthermore, in step S6, the sandstone transport layer serves as a migration channel for oil and gas to migrate laterally to the structural reservoir. Its transport capacity also determines the degree of reservoir filling. Oil and gas generally migrate along structural ridges within the transport layer. Therefore, the size and dip angle of the structural ridge determine the lateral transport capacity of oil and gas, the size of the structural ridge determines the amount of lateral migration, and the dip angle determines the accumulation capacity. The lateral transport index of the transport layer can be quantitatively calculated using the following formula:

[0038] R = H C L C sinδ

[0039] Among them, H C To construct the ridge height, L C δ represents the width of the ridge and δ represents the inclination angle of the ridge.

[0040] Furthermore, in step S7, to analyze the hydrocarbon accumulation probability of each trap, it is necessary to match the vertical hydrocarbon supply from the fault with the lateral migration of the sandstone transport layer. The migration path and hydrocarbon accumulation mode of each trap in the study area are analyzed. Generally, they are divided into two categories: the "source-fault-ridge" hydrocarbon accumulation system and the "source-fault-loop" hydrocarbon accumulation system. This step can be obtained through analysis of seismic profiles and three-dimensional geological maps.

[0041] Furthermore, in step S8, the probability of hydrocarbon accumulation in a trap is a comprehensive reflection of the vertical hydrocarbon supply capacity of the oil source fault and the lateral migration capacity of the sandstone conduit. Based on the above data, the probability of hydrocarbon accumulation in a trap can be calculated, thereby quantitatively predicting the probability of hydrocarbon accumulation in a trap and the size of the oil and gas field. The formula for calculating the probability of hydrocarbon accumulation is as follows:

[0042] P = U·R

[0043] If the hydrocarbon accumulation system is a "source-fault-loop" system, then R = 1; if the hydrocarbon accumulation system is a "source-fault-ridge" system, then R is the normalized value after actual measurement.

[0044] Compared with the prior art, the beneficial effects of the present invention are:

[0045] This invention develops a method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system. It fully considers the entire process of hydrocarbon generation, migration, and accumulation, comprehensively evaluating three aspects: the hydrocarbon supply capacity of the source rock, the vertical transport capacity of the fault, and the lateral transport capacity of the sandstone transport layer. This method can accurately and quantitatively evaluate the hydrocarbon transport capacity of the fault-sand body composite transport system. Accurate prediction of hydrocarbon transport capacity can effectively predict the probability of trap accumulation and the size of oil and gas fields, thereby improving exploration success rates. Especially in areas with low exploration levels, this invention does not require a large amount of existing drilling data or the accumulation patterns of discovered oil and gas fields as prior information; it only requires quantitative research on hydrocarbon transport capacity based on geological laws to predict oil and gas accumulation zones and improve the success rate of exploration wells. Attached Figure Description

[0046] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the description of the specific embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is the overall flowchart;

[0048] Figure 2 A schematic diagram of the model for each characterization parameter;

[0049] Figure 3 Profiles and plan views, as well as grids of the study area, are provided for interpreting and tracing source rocks, channel faults, and sandstone transport layers based on 3D seismic data of the study area.

[0050] Figure 4 A three-dimensional representation of the contact relationship between source rocks, flow faults, and sandstone transport layers in the study area;

[0051] Figure 5 A plan view of the hydrocarbon supply index of oil source fracture in the study area;

[0052] Figure 6 This is a graph showing the relationship between hydrocarbon accumulation probability and maximum hydrocarbon column height. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example

[0055] like Figure 1-6 As shown in the figure, this embodiment provides a method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system, which includes the following steps:

[0056] Step S1: Seismic interpretation and tracing are performed on the top and bottom surfaces of the source rock layer, fault plane, and top and bottom surfaces of the sandstone transport layer in the 3D seismic data volume to obtain paleotectonic maps of the source rock S, fault F, and sandstone transport layer C. If the depth domain 3D seismic data volume is used for interpretation and tracing, only depth correction based on the drilled well is required. If the time domain 3D seismic data volume is used for interpretation and tracing, a time domain structural map is obtained. Here, well-seismic calibration is performed first, and then the time-depth conversion relationship is established before converting the time domain structural map into a depth domain structural map. In this embodiment, after interpreting and tracing the time domain data, the time-depth conversion relationship of the well-seismic calibration is used to obtain the depth domain paleotectonic map.

[0057] like Figure 3 (a) The base map is a time-domain 3D seismic data volume profile. Interpretation of sandstone transport layers, faults, and the top and bottom surfaces of source rocks is performed on the 3D data volume. Based on the interpretation results of the data volume, the corresponding paleotectonic map can be obtained, such as... Figure 3 (b) is a structural diagram of the top surface of the main hydrocarbon source rock S during the hydrocarbon accumulation period. Figure 3 (c) is a plan view of the source-source fault F that was in contact with the sandstone transport layer during the hydrocarbon accumulation period. Figure 3 (d) Structural diagram of the top surface of the sandstone transport layer.

[0058] Step S2: When gridding the study area, if the grid is too large, there will be insufficient sampling points and sparse data; if the grid is too small, there will be too many sampling points and redundant data. Therefore, a 1000m × 1000m grid was used for this study area gridding. The grids for the main source rock S and the oil source fracture F are as follows: Figure 3 As shown in (b) and (c).

[0059] Step S3, as follows Figure 2 (a) is a schematic diagram of the fracture source index calculation model, based on the main source rock S in the above grid. ij and oil source break Paleotectonic diagrams are used to determine hydrocarbon supply capacity. The portion of the primary source rock S in the i-th row and j-th column of the grid is S. ijOil source No. K fractured F k The portion of the grid in the i-th row and j-th column is Oil and gas are generated from the main hydrocarbon source and migrate vertically into shallow strata via source faults. The hydrocarbon supply capacity of source rocks via source faults can be characterized by the volume of source rock units in contact with the source faults, which is defined here as the fault transmission index V. ij That is, the fracture with the source. The main source rock in contact S ij The sum of the volumes of the transport units;

[0060]

[0061] in, For fractures within the grid and through-source fractures The main source rock in contact S ij Contact area To connect with the source fracture The main source rock S ij The length of the transport unit, θ ij For the source of the fracture With the main source rock S ij The angle between the tendencies of contact, k = 1, 2...n.

[0062] Figure 4 (a) is a three-dimensional representation of the contact between the source fracture F1 and the source rock strata. The calculation parameters of the fracture source index in step three can be obtained through... Figure 4 (a) Measured.

[0063] Step S4, as follows Figure 2 (b) is a schematic diagram of the fracture vertical transport index calculation model, based on the oil source fractures within the above grid. Paleotectonic maps are used to obtain the vertical transport capacity of oil-source faults. The vertical transport capacity of faults is related to the permeability of the fault zone. The higher the permeability, the stronger the vertical transport capacity. However, the permeability of underground fault zones is difficult to obtain. We can only reflect the magnitude of the permeability of the fault zone and thus the vertical transport capacity of the fault through indirect factors.

[0064] There are four main parameters that indirectly reflect the permeability of fault zones: the activity of the fault during the hydrocarbon accumulation period, the effective width of the fault ridge, the geometric characteristics of the fault, and its tensile and compressive properties. High fault activity during hydrocarbon accumulation easily forms high-permeability zones, with oil and gas preferentially migrating upwards along the fault zone. When oil and gas migrate vertically along the fault surface, they preferentially migrate along the fault ridge. Therefore, the width of the fault ridge reflects the scale of the fault space development; the wider the ridge, the stronger the permeability and transport capacity of the fault. The geometric characteristics of the fault mainly refer to its dip angle. The larger the dip angle, the steeper the fault, and the steeper the fractures induced by the fault zone. This results in a greater upward component of the oil and gas migration along the fault, making upward migration easier. The tensile and compressive properties of the fault are mainly reflected by the angle between the fault strike and the regional principal compressive stress, representing the degree of opening of the fault zone. When the angle between the fault strike and the principal compressive stress is 90°, the fault zone is predominantly compressive, with a high degree of closure, resulting in the smallest transport space, the weakest permeability, and making upward migration of oil and gas difficult. When the angle between the fracture zone strike and the principal compressive stress is 0°, the fracture zone is predominantly tensile, with a high degree of opening and the strongest permeability, making it easier for oil and gas to migrate upwards. The vertical conductivity index of the fracture can be quantitatively calculated using the following formula:

[0065]

[0066] in The growth index of oil-source faults during the reservoir formation period within the grid is used to characterize the intensity of oil-source fault activity during the reservoir formation period. It is defined as the ratio of the thickness of the downthrown block to the thickness of the upthrown block in the same stratigraphic unit on both sides of the fault. Let H be... k Uij H represents the thickness of the uplifted block of the strata during the hydrocarbon accumulation period of fault k within the grid. k Dij The thickness of the downthrown block during the hydrocarbon accumulation period of fault k within the grid;

[0067] The effective ridge width of fracture k within the grid. The dip angle of fracture k within the grid. The angle between the direction of fracture k within the grid and the principal compressive stress in the region.

[0068] Figure 4 (a) is a three-dimensional representation of the source-source fault F1 and the sandstone transport layer. The calculation parameters of the vertical transport index of the fault in step S5 can be obtained through... Figure 4 (b) Measured.

[0069] Step S5: Based on the fracture source index V calculated within the above grid. ij and fracture conduction index T ijTo obtain the hydrocarbon supply capacity of fractures, the fracture source index and fracture vertical transport index within the grid characterize the vertical hydrocarbon supply capacity of source fractures matching hydrocarbon sources, determining the material basis for hydrocarbon accumulation in traps. The fracture hydrocarbon supply index is used to characterize this capacity; the fracture hydrocarbon supply index within each grid can be calculated, thereby quantitatively analyzing the vertical hydrocarbon supply capacity of oil source fractures in the study area. The fracture hydrocarbon supply index U... ij The calculation formula is as follows:

[0070] U ij =V ij ·T ij

[0071] Calculate the comprehensive evaluation index U within each grid. ij After that, interpolation calculations can be performed on the plane. Kriging interpolation or inverse distance weighted interpolation is generally used here. Finally, the contour map of the fault hydrocarbon supply index in the study area is drawn. This step can generally be completed by geological drawing software, such as Petrel or DoubleFox.

[0072] Taking the source-conducting fracture F1 as an example, Table 1 shows the parameters measured in steps S3 and S4, including the number of fractures in the grid, hydrocarbon accumulation growth index, fracture ridge length, fracture dip angle, angle between the fracture and the principal stress, hydrocarbon source contact area, angle, and effective hydrocarbon source length. The source-conducting index and the transport index of the fracture can be calculated, and then the hydrocarbon supply index of the fracture can be calculated.

[0073]

[0074] Table 1

[0075] Figure 5 The comprehensive evaluation index U within each grid is calculated. ij A contour map drawn using DoubleFox, from... Figure 5 It can be seen that the hydrocarbon supply index of the oil source fracture F1 is the largest, showing a strong hydrocarbon supply capacity. In the process of oil and gas exploration, the matching between the oil source fracture and the sandstone transport layer can be studied to select favorable traps.

[0076] Step S6, as follows Figure 2 (c) is a schematic diagram of the calculation model for the lateral conductivity index of the conduit layer. Based on the paleotectonic map of sandstone C in the conduit layer, the lateral conductivity of the conduit layer is obtained. The sandstone conduit layer is the migration channel for oil and gas to migrate laterally to the structure for reservoir formation, and its conductivity also determines the degree of reservoir filling. Oil and gas generally migrate along structural ridges in the conduit layer. Therefore, the size and dip angle of the structural ridge determine the lateral conductivity of oil and gas. The size of the structural ridge determines the amount of lateral migration of oil and gas, and the dip angle determines the accumulation capacity of oil and gas. The lateral conductivity index of the conduit layer can be quantitatively calculated using the following formula:

[0077] R = HC L C sinδ

[0078] H C L represents the height of the ridge within the grid. C δ represents the width of the ridge within the grid, and δ represents the inclination angle of the ridge. Table 2 shows the statistics of the calculation parameters of the transverse conduction index of the ridge in the conduction layer.

[0079]

[0080] Table 2

[0081] Step S7: Based on the matching relationship between faults and sandstone transport layers, analyze the hydrocarbon accumulation model of the traps. To analyze the hydrocarbon accumulation probability of each trap, it is necessary to match the vertical hydrocarbon supply from the faults with the lateral migration of the sandstone transport layers. Analyze the migration path and hydrocarbon accumulation model of each trap in the study area. This is generally divided into two categories: the "source-fault-ridge" hydrocarbon accumulation system and the "source-fault-cage" hydrocarbon accumulation system. This step can be obtained through analysis of seismic profiles and 3D geological maps. Table 3 shows the statistical hydrocarbon accumulation models of each trap. For example, EP20-A is a "source-fault-cage" hydrocarbon accumulation, while EP20-F is a "source-fault-ridge" hydrocarbon accumulation.

[0082]

[0083] Table 3

[0084] Step S8: Based on the fracture hydrocarbon supply index, lateral transport index, and trap accumulation model, calculate the trap accumulation probability. The trap accumulation probability is a comprehensive reflection of the vertical hydrocarbon supply capacity of the oil source fracture and the lateral migration capacity of the sandstone transport layer. Based on the above data, calculate the accumulation probability of traps, and then quantitatively predict the accumulation probability of traps and the size of oil and gas fields. The accumulation probability calculation formula is as follows:

[0085] P = U·R

[0086] If the hydrocarbon accumulation system is a "source-fault-loop" system, then R = 1; if the hydrocarbon accumulation system is a "source-fault-ridge" system, then R is the normalized value after actual measurement.

[0087] Table 3 shows the fracture hydrocarbon supply index, transverse transport index of the transport layer, hydrocarbon accumulation probability, and maximum hydrocarbon column height of the trap calculated using this method in the study area of ​​the example. From the analysis of Table 3, it can be seen that the hydrocarbon accumulation probability of the EP20-A trap is the highest, reaching 38.13, followed by EP20-B, with a hydrocarbon accumulation probability of 7.92. Drilling has confirmed that EP20-A and EP20-B have the largest hydrocarbon column height and the highest degree of hydrocarbon enrichment. Moreover, the EP20-A and EP20-B oilfields are also the first and second largest oilfields in the region.

[0088] like Figure 6The graph shows the relationship between hydrocarbon accumulation probability and maximum hydrocarbon column height. As can be seen from the graph, the higher the hydrocarbon accumulation probability, the higher the actual maximum hydrocarbon column height, which proves the effectiveness of the method of the present invention.

[0089] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system, characterized in that, Includes the following steps: S1. Paleotectonic maps of the main source rock S, the source fault F, and the transport layer sandstone C during the hydrocarbon accumulation period; S2. The study area was gridded, and the main source rock within the grid was S. ij The oil source fracture is F k ij ; S3, based on the main source rocks S within the above grid ij and oil source fracture F k ij Paleotectonic maps were used to obtain hydrocarbon supply capacity, using the fracture source index V. ij Characterization; In step S3, the portion of the main source rock S in the i-th row and j-th column of the grid is S. ij Oil source No. K fractured F k The part of the grid in the i-th row and j-th column is F. k ij Oil and gas are generated from the main hydrocarbon source and migrate vertically into shallow strata via source faults. The hydrocarbon supply capacity of source rocks via source faults is characterized by the volume of source rock units in contact with the source faults, which is defined here as the fault transmission index V. ij That is, the source fracture F k ij The main source rock in contact S ij The sum of the volumes of the transport units; ； Among them, A k ij For the fracture within the grid and the source F k ij The main source rock in contact S ij Contact area, L k ij To connect with the source fracture F k ij The main source rock S ij The length of the transport unit, θ ij For the source fracture F k ij With the main source rock S ij The angle between the tendencies of contact, k=1,2……n; S4, Based on the oil source fracture F within the above grid k ij Paleotectonic maps were used to obtain the vertical transport capacity of oil-source faults, and the fault transport index T was used. ij Characterization; In step S4, the oil source fracture is a "high-speed channel" for the migration of oil and gas to shallow strata. The greater its vertical conduction capacity, the greater the probability of oil and gas accumulation and the higher the oil and gas reservoir filling degree. The vertical conduction capacity of the fracture is related to the permeability of the fracture zone. The greater the permeability, the stronger the vertical conduction capacity. However, the permeability of underground fracture zones is difficult to obtain. The vertical conduction capacity of the fracture can only be reflected by indirect factors. Four parameters reflect the permeability of fracture zones: fracture activity during hydrocarbon accumulation, effective ridge width, geometric characteristics of the fracture, and tensile-compressive properties. High fracture activity during hydrocarbon accumulation creates high-permeability zones, with hydrocarbons preferentially migrating upwards along the fracture zone. When hydrocarbons migrate vertically along the fracture surface, they preferentially migrate along the ridge. Therefore, the ridge width reflects the scale of fracture space development; the wider the ridge, the stronger the fracture's permeability and transport capacity. The geometric characteristics of the fracture refer to its dip angle; the larger the dip angle, the steeper the fracture, and the steeper the fracture-induced fractures. This results in a greater upward component of the hydrocarbon migration force along the fracture, making upward migration easier. The tensile-compressive properties of the fracture are reflected by the angle between the fracture strike and the regional principal compressive stress, representing the degree of fracture zone opening. When the angle between the fracture strike and the principal compressive stress is 90°, the fracture zone is predominantly compressive, with a high degree of closure, resulting in the smallest transport space, the weakest permeability, and making upward migration of hydrocarbons difficult. When the angle between the fracture strike and the principal compressive stress is 0°... At this time, the fault zone is mainly tensile, with a high degree of opening and the strongest permeability, making it easier for oil and gas to migrate upwards. The vertical transport index of the fault is quantitatively calculated using the following two formulas: ； ； Among them G k ij The growth index of oil-source faults during the reservoir formation period within the grid is used to characterize the intensity of oil-source fault activity during the reservoir formation period. It is defined as the ratio of the thickness of the downthrown block to the thickness of the upthrown block in the same stratigraphic unit on both sides of the fault. Let H be... k Uij H represents the thickness of the uplifted block of the strata during the hydrocarbon accumulation period of fault k within the grid. k Dij The thickness of the downthrown block during the hydrocarbon accumulation period of fault k within the grid; W k ij α is the effective ridge width of fracture k within the grid. k ij Let β be the dip angle of fracture k within the grid. k ij The angle between the direction of fracture k within the grid and the principal compressive stress in the region; S5. The fracture source index V calculated based on the above grid. ij and fracture conduction index T ij To obtain the fractured hydrocarbon supply capacity, the fractured hydrocarbon supply index U is used. ij Characterization; In step S5, the fault source-supply index and fault vertical transport index within the grid characterize the vertical hydrocarbon supply capacity of the source-supplying faults that match the hydrocarbon source, determining the material basis for the convergence of oil and gas into reservoirs. The fault hydrocarbon supply index is used to characterize this capacity. The fault hydrocarbon supply index within each grid is calculated to quantitatively analyze the vertical hydrocarbon supply capacity of the oil source faults in the study area. The formula for calculating the fault hydrocarbon supply index Uij is as follows: ； Calculate the comprehensive evaluation index U within each grid. ij Then, interpolation calculations can be performed on the plane, using Kriging interpolation or inverse distance weighted interpolation, and finally, contour maps of the fracture hydrocarbon supply index in the study area can be drawn. S6. Based on the paleotectonic map of the sandstone C in the transport layer, obtain the lateral transport capacity of the transport layer and characterize it using the lateral transport index R. In step S6, the sandstone transport layer serves as a migration channel for oil and gas to migrate laterally to the structural reservoir. Its transport capacity also determines the degree of reservoir filling. Oil and gas migrate along structural ridges within the transport layer; therefore, the size and dip angle of the structural ridge determine the lateral transport capacity of oil and gas. The size of the structural ridge determines the amount of lateral migration, and the dip angle determines the accumulation capacity. The lateral transport index of the transport layer is quantitatively calculated using the following formula: ； Among them, H C To construct the ridge height, L C δ represents the width of the ridge and δ represents the inclination angle of the ridge. S7. Based on the matching relationship between faults and sandstone transport layers, analyze the hydrocarbon accumulation mode of the traps; S8. Calculate the probability of hydrocarbon accumulation in a trap based on the fracture hydrocarbon supply index, the lateral transport index, and the trap accumulation model. In step S8, the probability of hydrocarbon accumulation in a trap is a comprehensive reflection of the vertical hydrocarbon supply capacity of the oil source fault and the lateral migration capacity of the sandstone conduit. Based on the above data, the probability of hydrocarbon accumulation in a trap is calculated, and then the probability of hydrocarbon accumulation in a trap and the size of the oil and gas field are quantitatively predicted. The formula for calculating the probability of hydrocarbon accumulation is as follows: ； If the hydrocarbon accumulation system is a "source-fault-loop" system, then R=1; if the hydrocarbon accumulation system is a "source-fault-ridge" system, then R is the normalized value after actual measurement.

2. The method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system according to claim 1, characterized in that: In step S1, seismic interpretation and tracing are performed on the top and bottom surfaces of the source rock layer, fault plane, and top and bottom surfaces of the sandstone transport layer in the three-dimensional seismic data volume to obtain paleotectonic maps of the source rock S, fault F, and sandstone transport layer C. If the depth domain three-dimensional seismic data volume is used for interpretation and tracing, only depth correction based on the drilled well is required. If the time domain three-dimensional seismic data volume is used for interpretation and tracing, a time domain structural map is obtained. Here, well-seismic calibration is performed first, and then the time-depth conversion relationship is established before converting the time domain structural map into a depth domain structural map.

3. The method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system according to claim 2, characterized in that: In step S2, when the study area is gridded, the grid size is 800m×800m or 1000m×1000m.

4. The method for predicting the probability of hydrocarbon accumulation in a trap using the hydrocarbon transport capacity of a composite transport system according to claim 3, characterized in that: In step S7, to analyze the hydrocarbon accumulation probability of each trap, it is necessary to match the vertical hydrocarbon supply from the fault with the lateral migration of the sandstone transport layer. The migration path and hydrocarbon accumulation mode of each trap in the study area are analyzed and divided into two categories: the "source-fault-ridge" hydrocarbon accumulation system and the "source-fault-loop" hydrocarbon accumulation system. This step can be obtained through seismic profile and three-dimensional geological map analysis.

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