Method for quantitatively evaluating unconformity transport capacity of ancient buried hill

Abstract

The invention provides a method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill, and the method comprises the steps: 1, determining an unconformity lithology combination type according to an actual geologic body; step 2, establishing a conceptual model for evaluating whether oil and gas are accumulated or not under different lithologic combination types; 3, establishing an unconformity fluid migration dynamic resistance mathematical model; and step 4, combining the step 2 to establish an unconformity conduction capability quantitative evaluation model. According to the method for quantitatively evaluating the unconformity transport capacity of the ancient buried hill, parameters are easy to obtain, the evaluation of the unconformity transport capacity of the ancient buried hill can be met to the greatest extent on the basis of composite geological actual conditions, and the method can be widely applied to the field of geological exploration and development evaluation of oil and gas resources of the ancient buried hill.

Description

Technical Field

[0001] The invention relates to the technical field of geological exploration and development evaluation of oil and gas resources, and in particular to a method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill. Background Art

[0002] The Lower Paleozoic buried hills have undergone 60Ma of geological evolution, and the carbonate strata have the particularity of differential dissolution under different fluid environments, resulting in the complexity of oil and gas transport pathways and reservoir-forming environments. Multiple periods of weathering and leaching have formed unconformities in the ancient buried hills. Differential dissolution makes the unconformity highly heterogeneous, and the diversity of lithological combinations above and below the unconformity also brings certain challenges to the study of its characteristics. As an important channel for oil and gas migration in the Lower Paleozoic buried hills, the unconformity's transport capacity determines the enrichment pattern of oil and gas in the ancient buried hills and the fullness of the reservoirs. The lag in the quantitative evaluation of its transport capacity has seriously affected the understanding of the oil and gas enrichment law of the ancient buried hills, thereby restricting the oil and gas exploration work in the ancient buried hills.

[0003] In the Chinese patent application with application number: CN201711417931.1, a quantitative evaluation method of the unconformity conductivity of clastic rocks is involved, and its specific steps are: S1 constructing a conceptual model of unconformity conductivity mode; S2 constructing a mathematical model of unconformity fluid migration; S3 improving the mathematical model of unconformity fluid migration and obtaining an improved mathematical model of unconformity fluid migration; S4 constructing an unconformity conductivity rate mathematical model based on the improved mathematical model of unconformity fluid migration to quantitatively evaluate the unconformity conductivity of clastic rocks. This method is an evaluation method based on the unconformity conductivity of clastic rock formations. The lateral connectivity and homogeneity of unconformities in clastic rock formations have traceable regularity, and the fluid seepage conforms to high-speed non-Darcy flow. Therefore, this patent has certain limitations for low-speed non-Darcy flow and Darcy fluid in unconformity transport in ancient buried hills with strong heterogeneity.

[0004] In the Chinese patent application with application number: CN201710566937.9, a method for evaluating the vertical conductivity of reverse faults in volcanic rock areas in the foreland thrust belt is involved, and the steps include: establishing a fault zone structural geological model, establishing a model for the relationship between the permeability and effective stress of the structural layer of the fault zone, establishing a geometric relationship model for the structural layer of the fault zone, a component fault zone permeability evaluation model, constructing a mathematical model for the permeability correction factor of the fault zone, optimizing the fault conductivity evaluation profile, establishing a vertical conductivity quantitative evaluation model for fault units, and determining the threshold value of the fault conductivity quantitative evaluation index. The method for quantitative evaluation of the vertical conductivity of reverse faults proposed in this invention realizes the three-dimensional quantitative evaluation of the fault conductivity in the volcanic rock brittle stratum development zone, enriches the quantitative evaluation method of fault conductivity, and can be widely used in the evaluation of the conductivity of reverse faults in the volcanic rock areas in the foreland belt of the compression basin, which has important guiding significance for oil and gas exploration.

[0005] In the Chinese patent application with application number: CN202110134087.1, a method for evaluating the vertical conductivity of oil and gas based on the combination pattern of compression-torsion faults is involved, including: step 1, selecting a discovered reserve block with a high degree of exploration; step 2, dividing the vertical migration and accumulation units of oil and gas under the joint control of the fault combination pattern and the regional cap rock; step 3, conducting statistics on the fault combination pattern, the thickness of the corresponding fault-penetrating regional cap rock, and the scale of discovered reserves; step 4, calculating the vertical conductivity index of oil and gas corresponding to the combination pattern fault of the vertical migration and accumulation unit; step 5, fitting the vertical conductivity index curves of faults of different combination patterns at multiple block sample points to form a quantitative evaluation chart. This method for evaluating the vertical conductivity of oil and gas based on the combination pattern of compression-torsion faults solves the problem of the method for evaluating the vertical conductivity of oil and gas in complex compression-torsion fault zones in clastic rock basins, and is more in line with the development characteristics of compression-torsion faults and petroleum geological conditions in compression-torsion superimposed basins with clastic rock filling as the main component, effectively guiding the practice of oil and gas exploration, and has good prospects for application and promotion.

[0006] The above existing technologies are all significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new method for quantitatively evaluating the unconformity transport capacity of ancient buried hills. Summary of the invention

[0007] The purpose of the present invention is to provide a method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill, which is conducive to the study and prediction of the oil and gas enrichment law and enrichment pattern inside the ancient buried hill of the Lower Paleozoic in a deep layer of an oil and gas basin.

[0008] The object of the present invention can be achieved by the following technical measures: a method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill, the method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill comprising:

[0009] Step 1: According to the actual geological body, clarify the unconformity lithology combination type;

[0010] Step 2: Establish a conceptual model for evaluating whether oil and gas accumulation occurs under different lithology combinations;

[0011] Step 3, establish a mathematical model of the dynamic resistance of unconformity fluid transport;

[0012] Step 4: Combined with step 2, establish a quantitative evaluation model for the unconformity conductivity.

[0013] The purpose of the present invention can also be achieved by the following technical measures:

[0014] In step 1, based on the analysis of field outcrops, indoor core observations, and logging data, statistics are collected on the upper and lower lithologic combinations of the unconformity in the ancient buried hill, and different lithologic combinations are classified according to whether the upper lithology has sealing properties and whether the lower lithology has conductivity.

[0015] In step 2, a conceptual model F for evaluating oil and gas accumulation under different lithology combinations is constructed:

[0016] F=X·Y Formula (1)

[0017] Where X is the unconformable lithology combination configuration, and Y is the source-transport circle docking relationship.

[0018] In step 2, when X=1, the upper lithology blocks the lower lithology transport, when X=0, the upper lithology does not block the lower lithology transport, and X=-1, the upper lithology transports and the lower lithology blocks; when Y=1, the source and transport circles are connected, and when Y=0, the source and transport circles are not connected; when F=1, the unconformity has the transport capacity and is trapped in the buried hill below the unconformity; when F=-1, the upper part of the unconformity conducts and the oil and gas are accumulated in the shallow trap; F=0 means that the oil and gas do not migrate and accumulate along the unconformity.

[0019] In step 3, the unconformity fluid migration dynamics and resistance model is constructed. The fluid migration in the unconformity conforms to the percolation mechanism:

[0020]

[0021] Q—Flow rate through rock per unit time, cm 3 / s;

[0022] K-unconformity permeability, Md;

[0023] S- cross-sectional area of ​​fluid passing through the unconformity, cm 2 ;

[0024] μ-fluid viscosity, 10-3Pa·s;

[0025] △P-pressure difference before and after the fluid passes, MPa;

[0026] L-conduction distance, cm;

[0027] Transform formula 2 into:

[0028]

[0029] That is, the flow rate of fluid passing through a unit area per unit time, that is, the flow velocity V of the fluid, in m / s;

[0030] is the fluid pressure difference per unit distance, unit: MPa / m;

[0031] Therefore, the kinetic gradient of fluid transport within the unconformity is:

[0032]

[0033] In step 3, the resistance to oil and gas migration within the unconformity is mainly the capillary pressure of the porous medium, which depends on the interfacial tension between the two fluids, the capillary radius and the wettability of the medium and can be expressed as:

[0034]

[0035] Pc, capillary pressure, MPa;

[0036] σ, oil-water interfacial tension, N / m;

[0037] θ, wetting angle, °;

[0038] r, pore throat radius, m.

[0039] In step 3, the wetting angle θ<90° is a hydrophilic medium, and θ>90° is an oleophilic medium. Since the inner surface of the unconformable rock is basically wetted by water, it behaves as a hydrophilic medium, θ=0°, cosθ=-1, and formula 5 can be changed to:

[0040]

[0041] In step 4, collect the measured pressure value P of the source rock 烃源岩 , oil column height Z, unconformity burial depth h are combined with step 2 to establish a quantitative evaluation model for the unconformity conductivity.

[0042] In step 4, the fluid migration within the unconformity satisfies the dynamic equilibrium theory, and the migration and accumulation dynamics equation is expressed as:

[0043] P(migration and concentration) = P(migration force) - P(migration resistance) Formula (7)

[0044] When P>0, fluid can migrate within the unconformity;

[0045] When P = 0, the fluid accumulates in the trap near the unconformity;

[0046] When P < 0, the fluid does not migrate within the unconformity;

[0047] Through the study and analysis of the conceptual model of unconformity transport mode, it can be seen that the vertical lithological combination structure of unconformity has an important influence on the oil and gas transport capacity of unconformity. Combining formula (1) and formula (7), the evaluation equation of unconformity fluid migration and accumulation dynamics is:

[0048] P 不整合 =X·Y·P(aggregation) Formula (8).

[0049] In step 4, the forces acting on the fluids that migrate outside the unconformity include the hydrocarbon expulsion force of the source rock and buoyancy, and the resistance mainly comes from the capillary force. Therefore, the evaluation equation for the dynamics of fluid migration and accumulation in the unconformity is further expressed as:

[0050] P 不整合 =X·Y·(P 剩余 +P 浮力 -| P C|) Formula (9)

[0051]

[0052] Among them, P 不整合 : Momentum for oil and gas migration in unconformity, unit: MPa;

[0053] P 剩余 : is the residual pressure of source rock, i.e. the initial pressure of hydrocarbon expulsion, in MPa;

[0054] P 静水 : is the hydrostatic pressure, unit: MPa;

[0055] h: unconformity burial depth, unit: m;

[0056] Z is the oil column height, in m;

[0057] ρ o is the oil density, unit is g / cm 3 ;

[0058] According to the equivalent principle of the dynamic gradient of the unconformity, formula (4) is equivalent to formula (10), that is:

[0059]

[0060] Formula 11 is transformed into

[0061]

[0062] In step 4, the fluid migration rate V in the unconformity can characterize the transport capacity of the unconformity. Combined with formula (12) for the evaluation standard of the unconformity migration capacity, when the fluid migrates in the unconformity, V>0, that is:

[0063]

[0064] The larger the value, the better the unconformity conductivity;

[0065] when

[0066]

[0067] When the fluid is trapped near the unconformity, it accumulates;

[0068]

[0069] When the unconformity is formed, it does not have the ability to transport oil and gas.

[0070] In step 4, according to the evaluation formula, it can be seen that the unconformity transport capacity is proportional to the permeability, flow rate, and hydrocarbon expulsion power, and is inversely proportional to the fluid viscosity and migration distance.

[0071] The method for quantitatively evaluating the unconformity conductivity of an ancient buried hill in the present invention has relatively easy-to-obtain parameters and can satisfy the evaluation of the unconformity conductivity of a Lower Paleozoic buried hill on the basis of composite geological actual conditions to the greatest extent, and can be widely applied to the field of geological exploration and development evaluation of Lower Paleozoic buried hill oil and gas resources.

[0072] The advantages of the present invention also lie in:

[0073] 1. In the present invention, a conceptual model of the spatial structure of carbonate unconformity and its transport mode is first established, the influencing factors of unconformity migration efficiency are summarized, the concept of unconformity fluid migration is proposed, and a mathematical model of fluid migration is constructed based on the microscopic seepage mechanism of fluid. Then, the unconformity surface dip angle and unconformity structural parameters are introduced to improve the mathematical model of fluid migration. On this basis, in order to highlight the transport capacity of the unconformity itself, the concept of unconformity transport rate is proposed, and a mathematical model of transport rate is constructed, so as to quantitatively evaluate the transport capacity of the unconformity.

[0074] 2. The present invention takes into account a variety of geological factors and can meet the accurate requirements for quantitative evaluation of the unconformity conductivity of ancient carbonate strata in deep buried environments. The exploration of oil and gas reservoirs in such buried environments is an important area for increasing reserves and production in the future. The present invention can be widely used in the field of geological exploration and development evaluation of deep oil and gas resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] Figure 1 A flowchart of a specific embodiment of the method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill of the present invention;

[0076] Figure 2 It is a schematic diagram of the division of lithologic combinations near the unconformity of an ancient buried hill in a specific embodiment of the present invention;

[0077] Figure 3 It is a schematic diagram of a conceptual model for evaluating oil and gas accumulation near an ancient buried hill unconformity in a specific embodiment of the present invention;

[0078] Figure 4 It is a schematic diagram of the dominant migration path of oil and gas in evaluating the unconformity of ancient buried hills in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0079] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0080] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0081] like Figure 1 As shown, Figure 1 The flowchart of the method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill of the present invention is as follows. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill comprises:

[0082] Step 1: According to the actual geological body, clarify the unconformity lithology combination type;

[0083] Step 2: Establish a conceptual model for evaluating whether oil and gas accumulation occurs under different lithology combinations;

[0084] Step 3, establish a mathematical model of the dynamic resistance of unconformity fluid transport;

[0085] Step 4: Combined with step 2, establish a quantitative evaluation model for the unconformity conductivity.

[0086] The following are several specific embodiments of the present invention.

[0087] Example 1

[0088] In a specific embodiment 1 of the present invention, the method for quantitatively evaluating the unconformity transport capacity of the ancient buried hill includes the following steps:

[0089] In step 1, based on the analysis of field outcrops, indoor core observations, and logging data, statistics are collected on the upper and lower lithologic combinations of the unconformity in the ancient buried hill, and different lithologic combinations are classified according to whether the upper lithology has sealing properties and whether the lower lithology has conductivity.

[0090] In step 2, a conceptual model for evaluating oil and gas reservoir formation under different lithology combinations is constructed.

[0091] F=X·Y Formula (1)

[0092] Where X is the unconformity lithology combination configuration. When X=1, the upper lithology blocks the lower lithology conduction. Figure 2 Type I), when X=0, the upper lithology does not block the lower lithology conduction ( Figure 2 Type II), X = -1 means upper lithology conduction and lower lithology blocking ( Figure 2 Category III). Among them, Figure 2 Type I is a combination of upper plugging lithology and lower conductivity lithology. Figure 2Type II is a combination of upper conductivity lithology and lower plugging lithology. Figure 2 Class III is a lithology combination in which both the upper and lower lithologies have transport capacity.

[0093] Y: source-transmission-circle connection relationship. When Y=1, the source-transmission-circle is connected. When Y=0, the source-transmission-circle is not connected.

[0094] When F=1, the unconformity has the ability to transport and the reservoir is trapped in the buried hill below the unconformity ( Figure 3 Left middle figure), when F = -1, the upper part of the unconformity conducts and the oil and gas accumulate in the shallow trap ( Figure 3 Middle figure), when F = 0, oil and gas do not form reservoirs ( Figure 3 (middle right picture). Figure 3 The middle left picture shows oil and gas trapped in the buried hill below the unconformity; Figure 3 The middle figure shows that the upper part of the unconformity has the transport capacity and the oil and gas are accumulated in the trap above the unconformity; Figure 3 The middle right picture shows that the unconformity has the ability to transport oil and gas both above and below, but oil and gas cannot accumulate.

[0095] In step 3, the unconformity fluid transport force and resistance model is constructed.

[0096] Fluid migration within an unconformity follows a percolation mechanism:

[0097]

[0098] Q—Flow rate through rock per unit time, cm 3 / s;

[0099] K-unconformity permeability, Md;

[0100] S- cross-sectional area of ​​fluid passing through the unconformity, cm 2 ;

[0101] μ-fluid viscosity, 10-3Pa·s;

[0102] △P-pressure difference before and after the fluid passes, MPa;

[0103] L-conduction distance, cm.

[0104] Transform formula 2 into:

[0105]

[0106] That is, the fluid flow rate through a unit area per unit time, that is, the flow velocity V of the fluid, in m / s.

[0107] It is the fluid pressure difference per unit distance, in MPa / m.

[0108] Therefore, the kinetic gradient of fluid transport within the unconformity is:

[0109]

[0110] The resistance to oil and gas migration within the unconformity is mainly the capillary pressure of the porous medium, which depends on the interfacial tension between the two fluids, the capillary radius and the wettability of the medium and can be expressed as:

[0111]

[0112] Pc, capillary pressure, MPa;

[0113] σ, oil-water interfacial tension, N / m;

[0114] θ, wetting angle, °;

[0115] r, pore throat radius, m.

[0116] The interfacial tension σ can refer to the table of oil-water interfacial tension variation with depth obtained empirically by Schowalter in 1979 (Table 1).

[0117] Table 1 Relationship between oil-water interfacial tension and depth

[0118]

[0119]

[0120] When the wetting angle θ is less than 90°, it is a hydrophilic medium, and when θ is greater than 90°, it is an oleophilic medium. Since the inner surface of the unconformable rock is basically wetted by water, it behaves as a hydrophilic medium. When θ is 0° and cosθ is -1, Formula 5 can be changed to:

[0121]

[0122] In step 4, the measured pressure value P of the source rock is collected. 烃源岩 , oil column height Z, unconformity burial depth h are combined with step 2 to establish a quantitative evaluation model for the unconformity conductivity.

[0123] The fluid migration within the unconformity satisfies the dynamic equilibrium theory, and the migration and accumulation dynamics equation is expressed as:

[0124] P(migration and concentration) = P(migration force) - P(migration resistance) Formula (7)

[0125] When P>0, fluid can migrate within the unconformity;

[0126] When P = 0, the fluid accumulates in the trap near the unconformity;

[0127] When P < 0, fluid does not migrate within the unconformity.

[0128] Through the study and analysis of the conceptual model of unconformity transport mode, it can be seen that the vertical lithological combination structure of unconformity has an important influence on the oil and gas transport capacity of unconformity. Combining formula (1) and formula (7), the evaluation equation of unconformity fluid migration and accumulation dynamics is:

[0129] P 不整合 =X·Y·P(aggregation) Formula (8)

[0130] The forces acting on the fluid when it migrates outside the unconformity include the hydrocarbon expulsion force of the source rock and buoyancy, and the resistance mainly comes from the capillary force. Therefore, the evaluation equation for the dynamics of fluid migration and accumulation in the unconformity is further expressed as:

[0131] P 不整合 =X·Y·[P 剩余 +P 浮力 -|P C |] Formula (9)

[0132]

[0133] Where Z is the oil column height, in m;

[0134] ρ o is the oil density, unit is g / cm 3 ;

[0135] According to the equivalent principle of the dynamic gradient of the unconformity, formula (4) is equivalent to formula (10), that is:

[0136]

[0137] Formula 11 is transformed into

[0138]

[0139] The fluid migration rate V in the unconformity can characterize the transport capacity of the unconformity. Combined with formula (12) for the evaluation standard of the unconformity migration capacity, when the fluid migrates in the unconformity, V>0, that is:

[0140]

[0141] The larger the value, the better the unconformity conductivity;

[0142] when

[0143]

[0144] When the fluid is trapped near the unconformity, it accumulates;

[0145]

[0146] When the unconformity is formed, it does not have the ability to transport oil and gas.

[0147] According to the evaluation formula,

[0148] The unconformity transport capacity is proportional to the permeability, flow rate, and hydrocarbon expulsion dynamics, and inversely proportional to the fluid viscosity and migration distance.

[0149] Figure 4 It is a schematic diagram of the favorable oil and gas migration path for evaluating the unconformity of a buried hill in a specific embodiment of the present invention, wherein the curve is a simulated path for predicting the migration of oil and gas along the lower part of the unconformity into the buried hill, and the streamline end points to the favorable oil and gas accumulation area in the buried hill.

[0150] The parameters of this method are easy to obtain, and can satisfy the evaluation of the unconformity transport capacity of the Lower Paleozoic buried hills on the basis of the actual geological conditions to the greatest extent. It can be widely used in the field of geological exploration and development evaluation of oil and gas resources in the Lower Paleozoic buried hills.

[0151] Example 2

[0152] In a specific embodiment 2 of the present invention, the evaluation method of the unconformity transport capacity of the ancient buried hill includes the following steps:

[0153] Step 1: Based on the unconformity of the ancient buried hill in the oil and gas basin, the lithology combination near the unconformity is statistically analyzed. According to whether the lithology above and below the unconformity is permeable, it can be divided into three categories;

[0154] Step 2: Based on the three types of lithology combinations, establish a conceptual model for evaluating oil and gas reservoir formation under different lithology combinations. Let X be the unconformity lithology combination configuration. When X=1, the upper lithology blocks the lower lithology conduction. When X=0, the upper lithology does not block the lower lithology conduction. X=-1 means the upper lithology conducts and the lower lithology blocks. Let Y be the source-transmission circle docking relationship. When Y=1, the source-transmission circle docks. When Y=0, the source-transmission circle does not dock. Then the reservoir formation concept evaluation model is:

[0155] F=X·Y Formula (13)

[0156] Step 3: The fluid migration within the unconformity conforms to the percolation mechanism, so the flow rate per unit area per unit time is:

[0157]

[0158] Q—Flow rate through rock per unit time, cm 3 / s;

[0159] K-unconformity permeability, Md;

[0160] S- cross-sectional area of ​​fluid passing through the unconformity, cm 2 ;

[0161] μ-fluid viscosity, 10 -3 Pa·s;

[0162] △P-pressure difference before and after the fluid passes, MPa;

[0163] L-conduction distance, cm.

[0164] The formula transforms into:

[0165]

[0166] The resistance to fluid migration within the unconformity is mainly the capillary pressure of the porous medium, and its magnitude is affected by the fluid interfacial tension, capillary radius and medium wettability. There is a corresponding relationship between fluid interfacial tension and depth, and it is a certain value under different depths, temperature and pressure conditions. The inner surface of the rock within the unconformity is mainly a hydrophilic medium with a wetting angle of 0° and cosθ=-1, so the expression formula for resistance is:

[0167]

[0168] Step 4: The migration of fluids in the unconformity satisfies the dynamic equilibrium theory. When the driving force is greater than the resistance, the fluid can migrate in the unconformity. When the driving force is equal to the resistance, the fluid accumulates in the trap near the unconformity. When the driving force is less than the resistance, the fluid dissipates in the unconformity. Assume that the oil column height is Z, in meters, and ρ o is the oil density, unit is g / cm 3 , combined with the unconformity oil and gas reservoir evaluation conceptual model in step 2, the unconformity fluid migration and accumulation dynamics evaluation equation is established:

[0169]

[0170] Substituting formula (13) into formula (15),

[0171]

[0172] When V is greater than 0, the unconformity conducts oil and gas; when V = 0, the unconformity forms an accumulation; when V is less than 0, the unconformity does not have the ability to conduct oil and gas.

[0173] Example 3

[0174] In a specific embodiment 3 of the present invention, the method for evaluating the unconformity transport capacity of an ancient buried hill includes the following steps:

[0175] Step 101: Collect field data, core data, logging data and well data, and classify the lithology combination near the unconformity. The lithology combination near the unconformity in the ancient buried hill can be divided into: the upper rock layer is mainly composed of a series of low-permeability rock types such as breccia, mudstone or weathered claystone, and the lower part is carbonate rock with permeability and storage capacity after weathering and leaching. This lithology combination can be classified as Class I; the upper part is sandstone with certain porosity and permeability, and the lower part is mudstone with low permeability. This lithology combination can be classified as Class II; the upper and lower parts of the unconformity are permeable rock layers, which are classified as Class III.

[0176] Step 102: Evaluate the three types of lithologic combinations in step 101, especially whether they can form reservoirs. Let X be the unconformity lithologic combination configuration, X=1 for type I, X=0 for type II, and X=-1 for type III; let Y be the source-transport circle docking relationship, Y=1 for source-transport circle docking, and Y=0 for source-transport circle non-docking. The conceptual model for evaluating the unconformity conductivity is:

[0177] F=X·Y Formula (19)

[0178] When F=1, the unconformity has the ability to transport and the oil and gas are trapped in the buried hill below the unconformity. When F=-1, the upper part of the unconformity is transported and the oil and gas are accumulated in the shallow trap.

[0179] Step 103: The kinetic gradient of fluid migration within the unconformity is:

[0180]

[0181] Unconformity is generally an oil-wet medium, with a wetting angle of cosθ = -1. The interfacial tension σ can refer to the table of oil-water interfacial tension variation with depth obtained by Schowalter in 1979. Therefore, the resistance model is:

[0182]

[0183] Step 104: If the fluid enters the unconformity and keeps migrating, the migration rate V is greater than 0. If the fluid is accumulated near the unconformity, the fluid migration motive force is 0. If there is no fluid migration in the unconformity, the migration motive force is less than 0. Therefore, combining Formula 19-Formula 21, the unconformity fluid migration evaluation model is:

[0184]

[0185] When formula 22 is greater than zero, there is fluid migration in the unconformity, and the larger the value, the higher the migration efficiency. When formula 22 is equal to 0, the fluid is accumulated near the unconformity. When formula 22 is less than 0, the unconformity has no oil and gas transport capacity. According to the evaluation formula, the transport capacity of the unconformity is proportional to the permeability, flow rate, and hydrocarbon expulsion power, and inversely proportional to the fluid viscosity and migration distance.

[0186] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0187] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A method for quantitatively evaluating the unconformity transport capacity of buried hills, characterized in that: The quantitative evaluation methods of the unconformity transport capacity of the ancient buried hill include: Step 1: According to the actual geological body, clarify the unconformity lithology combination type; Step 2: Establish a conceptual model for evaluating whether oil and gas accumulation occurs under different lithology combinations; Step 3, establish a mathematical model of the dynamic resistance of unconformity fluid transport; Step 4: Combined with step 2, establish a quantitative evaluation model for the unconformity conductivity.

2. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 1, characterized in that: In step 1, based on the analysis of field outcrops, indoor core observations, and logging data, statistics are collected on the upper and lower lithologic combinations of the unconformity in the ancient buried hill, and different lithologic combinations are classified according to whether the upper lithology has sealing properties and whether the lower lithology has conductivity.

3. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill according to claim 1, characterized in that: In step 2, a conceptual model F for evaluating oil and gas accumulation under different lithology combinations is constructed: F=X·Y Formula (1) Where X is the unconformable lithology combination configuration, and Y is the source-transport circle docking relationship.

4. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill according to claim 3, characterized in that: In step 2, when X=1, the upper lithology blocks the lower lithology transport, when X=0, the upper lithology does not block the lower lithology transport, and X=-1, the upper lithology transports and the lower lithology blocks; when Y=1, the source and transport circles are connected, and when Y=0, the source and transport circles are not connected; when F=1, the unconformity has the transport capacity and is trapped in the buried hill below the unconformity; when F=-1, the upper part of the unconformity conducts and the oil and gas are accumulated in the shallow trap; F=0 means that the oil and gas do not migrate and accumulate along the unconformity.

5. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 4, characterized in that: In step 3, the unconformity fluid migration dynamics and resistance model is constructed. The fluid migration in the unconformity conforms to the percolation mechanism: Q—Flow rate through rock per unit time, cm 3 / s; K-unconformity permeability, Md; S- cross-sectional area of ​​fluid passing through the unconformity, cm 2 ; μ-fluid viscosity, 10-3Pa·s; △P-pressure difference before and after the fluid passes, MPa; L-conduction distance, cm; Transform formula 2 into: That is, the flow rate of fluid passing through a unit area per unit time, that is, the flow velocity V of the fluid, in m / s; is the fluid pressure difference per unit distance, unit: MPa / m; Therefore, the kinetic gradient of fluid transport within the unconformity is:

6. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill according to claim 5, characterized in that: In step 3, the resistance to oil and gas migration within the unconformity is mainly the capillary pressure of the porous medium, which depends on the interfacial tension between the two fluids, the capillary radius and the wettability of the medium and can be expressed as: Pc, capillary pressure, MPa; σ, oil-water interfacial tension, N / m; θ, wetting angle, °; r, pore throat radius, m.

7. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill according to claim 6, characterized in that: In step 3, the wetting angle θ<90° is a hydrophilic medium, and θ>90° is an oleophilic medium. Since the inner surface of the unconformable rock is basically wetted by water, it behaves as a hydrophilic medium, θ=0°, cosθ=-1, and formula 5 can be changed to:

8. The method for quantitatively evaluating the unconformity transport capacity of an ancient buried hill according to claim 7, characterized in that: In step 4, collect the measured pressure value P of the source rock 烃源岩 , oil column height Z, unconformity burial depth h are combined with step 2 to establish a quantitative evaluation model for the unconformity conductivity.

9. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 8, characterized in that: In step 4, the fluid migration within the unconformity satisfies the dynamic equilibrium theory, and the migration and accumulation dynamics equation is expressed as: P(migration and concentration) = P(migration force) - P(migration resistance) Formula (7) When P>0, fluid can migrate within the unconformity; When P = 0, the fluid accumulates in the trap near the unconformity; When P < 0, the fluid does not migrate within the unconformity; Through the study and analysis of the conceptual model of unconformity transport mode, it can be seen that the vertical lithological combination structure of unconformity has an important influence on the oil and gas transport capacity of unconformity. Combining formula (1) and formula (7), the evaluation equation of unconformity fluid migration and accumulation dynamics is: P 不整合 =X·Y·P(aggregation) Formula (8).

10. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 9, characterized in that: In step 4, the forces acting on the fluids that migrate outside the unconformity include the hydrocarbon expulsion force of the source rock and buoyancy, and the resistance mainly comes from the capillary force. Therefore, the evaluation equation for the dynamics of fluid migration and accumulation in the unconformity is further expressed as: P 不整合 =X·Y·[P 剩余 +P 浮力 -|P C |] Formula (9) Among them, P 不整合 is the driving force of oil and gas migration in unconformity, unit: MPa; P 剩余 is the residual pressure of source rock, i.e. the initial pressure of hydrocarbon expulsion, in MPa; P 静水 is the hydrostatic pressure, unit: MPa; h is the unconformity burial depth, in m; Z is the oil column height, in m; ρ o is the oil density, unit is g / cm 3 ; According to the equivalent principle of the dynamic gradient of the unconformity, formula (4) is equivalent to formula (10), that is: Formula 11 is transformed into 11. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 10, characterized in that: In step 4, the fluid migration rate V in the unconformity can characterize the transport capacity of the unconformity. Combined with formula (12) for the evaluation standard of the unconformity migration capacity, when the fluid migrates in the unconformity, V>0, that is: The larger the value, the better the unconformity conductivity; when When the fluid is trapped near the unconformity, it accumulates; When the unconformity is formed, it does not have the ability to transport oil and gas.

12. The method for quantitatively evaluating the unconformity transport capacity of buried hills according to claim 11, characterized in that: In step 4, according to the evaluation formula, it can be seen that the unconformity transport capacity is proportional to the permeability, flow rate, and hydrocarbon expulsion power, and is inversely proportional to the fluid viscosity and migration distance.

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