An oil and gas migration prediction method based on fine description of seepage structure

Abstract

The application provides an oil and gas migration prediction method based on fine description of seepage structure. The method performs local maximum processing on the fracture distribution probability through the seismic azimuth, and at the same time, the seismic dip is constrained to obtain the maximum probability dip of the fracture, and then the distribution of the seepage structure inside the reservoir is finely described, and then the seepage channel of the oil and gas migration and the high-probability oil and gas accumulation area are calculated in combination with the oil and gas probability of the reservoir to determine the layout position of the well to be drilled. The method has very important significance for fine description of the seepage structure inside the buried hill fracture reservoir and evaluation of the oil and gas migration, and can effectively guide the exploration and development of the buried hill fracture type oil and gas reservoir.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas exploration and development, specifically a method for predicting oil and gas migration based on a detailed description of seepage structure. Background Technology

[0002] Ancient buried hill fractured reservoirs possess significant oil and gas exploration and development potential. However, due to their complex geological structures, strong reservoir heterogeneity, disordered seismic reflection phase axes, poor continuity, and diverse reservoir spaces resulting from multiple evolutionary phases, determining reservoir fluid stimulation and hydrocarbon migration processes presents considerable challenges. Furthermore, the complex geological conditions also hinder the engineering implementation of buried hill reservoir exploration, leading to persistently high drilling costs. Therefore, to achieve breakthroughs in deep buried hill exploration under complex geological conditions, it is necessary to improve the prediction technology for the complex seepage structure of buried hill reservoirs, including the construction of geological models required for geological engineering construction in buried hill exploration, and to integrate exploration and development engineering with seismic geology.

[0003] In exploration and development, the complex geological structures and low quality of seismic data lead to ambiguity and uncertainty in identifying fractures and cracks within buried hills using conventional seismic attributes, making it difficult to effectively guide the prediction of hydrocarbon activity within these structures. To determine the patterns of hydrocarbon migration, a detailed description of the seepage structure characteristics within buried hills is needed. This provides clearer technical support for predicting further hydrocarbon migration and for well engineering design and construction during oil and gas development, guiding effective oil and gas reservoir exploration and drilling operations, and laying the foundation for safe, efficient, and high-quality oil and gas development. This invention patent aims to achieve a detailed description of the seepage structure within complex reservoirs, providing more reliable support for determining hydrocarbon migration within formations, and has significant application value. Summary of the Invention

[0004] To achieve a detailed description of reservoir flow structures and predict hydrocarbon migration patterns, this invention provides a method for predicting hydrocarbon migration based on a detailed description of flow structures. This method uses fracture probability to inversely constrain seismic dip information, clarifying the characteristics of the flow structure. This is then combined with the calculated reservoir gas content for interpretation, predicting hydrocarbon migration patterns and guiding reservoir evaluation and efficient oil and gas exploration and development. The method for predicting hydrocarbon migration based on a detailed description of flow structures includes the following steps:

[0005] (1) Input the original seismic data volume U, and establish the crack distribution probability volume S, seismic dip volume D, and seismic azimuth volume A of U;

[0006] (2) Set a rectangular window function W with side length d. The coordinates of the center point of W are (x0, y0, t0), where x0, y0, and t0 represent the coordinates of the center point in the x, y, and t directions, respectively, and the seismic azimuth angle at the center point is 0. The earthquake dip angle θ = D(x0,y0,t0) is used to constrain the earthquake dip angle volume D using the earthquake azimuth volume A and the crack distribution probability volume S, thus characterizing the crack distribution location. The maximum probability dip angle D of the crack is then determined by the following formula. SA (x0,y0,t0):

[0007]

[0008] In the formula, and These represent the azimuth angles of the center point. The coordinates of the sample points in the x, y, and t directions. This represents the probability value of the crack distribution at that point. null indicates an empty value;

[0009] (3) Move the rectangular window function W in the x, y, and t directions respectively until the maximum probability dip angle of the cracks in the entire original seismic data volume U is calculated, and the volume D with the maximum probability dip angle of the cracks is obtained. SA ;

[0010] (4) Use high-precision seismic signal time-frequency analysis methods to perform seismic instantaneous spectral energy decomposition on U:

[0011]

[0012] In the formula, ω is the angular frequency, U(ω) is the instantaneous spectrum of the seismic data U, and M represents the result of the energy decomposition of the seismic instantaneous spectrum;

[0013] (5) Determine the dominant frequency ω0 of the seismic data U, and calculate the probability G of the reservoir containing hydrocarbons using the results M of the seismic instantaneous spectral energy decomposition:

[0014] G=ω0M 2 ,

[0015] (6) Utilizing the maximum probability earthquake dip angle D of the fracture SA Based on the data of the reservoir's probability of oil and gas (G), the seepage channels for oil and gas migration and the high-probability oil and gas accumulation areas are calculated. Then, the locations of wells to be drilled are determined using the high-probability oil and gas accumulation areas. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the implementation of an oil and gas migration prediction method based on a fine description of seepage structure according to the present invention.

[0017] Figure 2 This is the original seismic data profile of an embodiment of the present invention.

[0018] Figure 3 This is a profile of the maximum probability seismic dip angle of the cracks in an embodiment of the present invention.

[0019] Figure 4 This is a reservoir oil and gas probability data profile according to an embodiment of the present invention.

[0020] Figure 5 This invention provides an embodiment of an oil and gas migration and accumulation profile based on a detailed description of the seepage structure. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described below with reference to the accompanying drawings of the embodiments of the present invention:

[0022] like Figure 1 As shown, the present invention provides a method for predicting oil and gas migration based on a fine description of seepage structure, comprising the following steps:

[0023] S1: Input the raw seismic data volume U to be interpreted.

[0024] like Figure 2 The image shows a profile extracted from the original seismic data volume. The horizontal axis represents the auxiliary survey line number, with a total of 450 lines and a line spacing of 25 meters. The vertical axis represents the sampling time. The start time shown in the image is 4.0 seconds, and the end time is 5.4 seconds. The time sampling interval of the seismic data is 2 milliseconds, and there are 701 sampling points. The light-colored dashed line along the dark phase axis in the image is the position of the upper interface of the target reservoir in the seismic image. The darker the color in the image, the larger the seismic amplitude value. The image shows relatively obvious buried hill structure (uplift) features.

[0025] S2: Establish the crack distribution probability S, earthquake dip angle D, and earthquake azimuth angle A;

[0026] S3: Set a rectangular window W with a side length of d = 3. The center point of the window has coordinates (x0, y0, t0), where x0, y0, and t0 represent the coordinates of the center point in the x, y, and t directions of the 3D seismic data, respectively. Within the rectangular window W, the center point has 8 adjacent sample points. The seismic azimuth angle of the center point of the rectangular window W is... Seismic dip at this point The seismic dip angle D is constrained by the seismic azimuth and the probability of crack distribution, that is, while depicting the location of crack distribution, the corresponding seismic dip angle D(x0,y0,t0) is formed:

[0027]

[0028] In the formula, and These represent the center points within the rectangular window W. The coordinates of the sample points in the x, y, and t directions. This represents the probability value of the crack distribution at that point. null indicates an empty value, D SA (x0, y0, t0) represents the obtained maximum probability dip angle of the crack. Move the rectangular window W until the calculation of the entire data volume is completed to obtain the maximum probability seismic dip angle attribute D of the crack. SA D SA (x0, y0, t0) ∈ D SA ;

[0029] like Figure 3 It is a profile extracted from the maximum probability earthquake dip angle data volume of the fracture, and the profile location is... Figure 2 The seismic profiles are identical. The horizontal axis represents the auxiliary survey line numbers, totaling 450 lines with a line spacing of 25 meters. The vertical axis represents the sampling time; the start time shown in the figure is 4.0 seconds, and the end time is 5.4 seconds. The seismic data sampling interval is 2 milliseconds, and there are 701 sampling points. The light-colored dashed line in the figure represents the location of the target reservoir's upper interface in the profile. Black lines and dark shaded areas represent fracture-developed areas, i.e., areas with developed seepage structures. The lighter the color, the fewer the fractures and the less developed the seepage structures. From Figure 3 As can be seen, at the top of the buried hill, the probability of fracture development is low, which can form a dense layer and act as an oil and gas trap. Inside the buried hill, the black lines are widely distributed, indicating that the internal seepage structure is relatively developed, and the top of the lines is basically facing the fracture-free area at the top of the buried hill.

[0030] S4: Perform seismic instantaneous spectral energy decomposition on the original seismic data volume U using high-precision seismic signal time-frequency analysis methods:

[0031]

[0032] In the formula, ω is the angular frequency, U(ω) is the instantaneous spectrum of the seismic data U, and M represents the result of the energy decomposition of the seismic instantaneous spectrum;

[0033] S5: Determine the dominant frequency ω0 of the seismic data U as 17Hz. Based on the seismic instantaneous spectral energy decomposition result M, calculate the probability of hydrocarbon content in the reservoir, i.e.:

[0034] G=ω0M 2 ,

[0035] In the formula, G represents the probability result of the reservoir containing oil and gas;

[0036] like Figure 4 It is a profile extracted from the reservoir's probability of hydrocarbon content, and the profile location is... Figure 2 and Figure 3The mid-section is the same. The horizontal axis in the figure represents the auxiliary survey line numbers, totaling 450 lines with a line spacing of 25 meters. The vertical axis represents the sampling time; the start time shown in the figure is 4.0 seconds, and the end time is 5.4 seconds. The seismic data sampling interval is 2 milliseconds, and there are 701 sampling points. The dashed line in the figure represents the location of the target reservoir's upper interface in the profile. Dark shading indicates that there may be a large accumulation of oil and gas in this area, while light-colored backgrounds indicate a lower probability of oil and gas accumulation. From Figure 4 As can be seen from the dotted lines on the top of the buried hill and the left and right sides of the top, there are shaded areas, indicating that these three places have a high probability of containing oil and gas.

[0037] S6: Utilizing the maximum probability earthquake dip angle D of the crack SA Based on the probability results G of oil and gas in the reservoir, the seepage channels for oil and gas migration and the oil and gas accumulation areas are determined, and the locations of the wells to be drilled are determined.

[0038] like Figure 5 It is a profile of the results of oil and gas migration and accumulation, and the profile location is related to... Figures 2 to 4 The mid-section is the same. The horizontal axis in the figure represents the auxiliary survey line number, with a total of 450 lines and a line spacing of 25 meters. The vertical axis represents the sampling time. The start time shown in the figure is 4.0 seconds, and the end time is 5.4 seconds. The time sampling interval of the seismic data is 2 milliseconds, and there are 701 sampling points. As shown in the figure, inside the buried hill, lighter oil and gas migrate along the direction indicated by the arrows in the figure to the top of the buried hill, where they accumulate under the sealing of the structural trap. The main oil and gas accumulation areas are located in three locations: OG-1, OG-2, and OG-3. Figure 3 Based on the distribution of migration channels, the oil and gas accumulated in OG-2 may migrate towards OG-1. OG-3 is located in a seepage structure, and the oil and gas are in a migration state. From T-1 to T-5, the oil and gas migrate from the right side of the buried hill to the top. From T-6 to T-8, the oil and gas migrate from the bottom and middle areas of the buried hill to the top. At T-9, the oil and gas migrate from the left side of the buried hill to the top. Therefore, the location of the well to be drilled can be determined as follows: Figure 5 As shown by the black straight line in the middle.

[0039] The advantages of the method of the present invention are:

[0040] (1) The present invention uses a highly efficient and accurate crack identification method, which can effectively identify the internal crack network of complex ancient buried hill strata.

[0041] (2) By constraining the seismic dip angle with the seismic azimuth and the probability of crack distribution, the spatial distribution of the crack network as a seepage channel can be characterized, and the characteristic information of these crack networks can be quantitatively interpreted.

[0042] (3) Combining the reservoir oil-bearing probability estimation results with the maximum probability seismic dip angle of fractures can effectively predict the seepage channels for oil and gas migration and the oil and gas accumulation areas, providing an effective basis for drilling well location deployment and improving the interpretation accuracy and development efficiency of ancient buried hill oil and gas reservoirs.

[0043] The above embodiments are only used to illustrate the present invention. The implementation steps of the method can be varied. Any equivalent transformations and improvements made on the basis of the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for predicting hydrocarbon migration based on fine description of seepage structure, characterized in that, The main steps include: (1) Input the original seismic data volume U, and establish the crack distribution probability volume S, seismic dip volume D, and seismic azimuth volume A of U; (2) Set a rectangular window function W with side length d. The coordinates of the center point of W are (x0, y0, t0), where x0, y0, and t0 represent the coordinates of the center point in the x, y, and t directions, respectively, and the seismic azimuth angle at the center point is 0. The earthquake dip angle θ = D(x0, y0, t0) is used to constrain the earthquake dip angle volume D using the earthquake azimuth volume A and the crack distribution probability volume S, thus characterizing the crack distribution location. The maximum probability dip angle D of the crack is then determined by the following formula. SA (x0, y0, t0): In the formula, and These represent the azimuth angles of the center point. The coordinates of the sample points in the x, y, and t directions. This represents the probability value of the crack distribution at that point. null indicates an empty value; (3) Move the rectangular window function W in the x, y, and t directions respectively until the maximum probability dip angle of the cracks in the entire original seismic data volume U is calculated, and the volume D with the maximum probability dip angle of the cracks is obtained. SA ; (4) Use high-precision seismic signal time-frequency analysis methods to perform seismic instantaneous spectral energy decomposition on U: In the formula, ω is the angular frequency, U(ω) is the instantaneous spectrum of the seismic data U, and M represents the result of the energy decomposition of the seismic instantaneous spectrum; (5) Determine the dominant frequency ω0 of the seismic data U, and calculate the hydrocarbon probability G of the reservoir using the results M of the seismic instantaneous spectral energy decomposition: G=ω0M 2 , (6) Utilizing the maximum probability earthquake dip angle D of the crack SA Based on the data of the reservoir's probability of oil and gas (G), the seepage channels for oil and gas migration and the high-probability oil and gas accumulation areas are calculated. Then, the locations of wells to be drilled are determined using the high-probability oil and gas accumulation areas.

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