A method for dividing favorable areas based on shale gas exploration prediction

Abstract

The present invention discloses a method for dividing favorable areas based on shale gas exploration prediction, which uses the thickness of Class I continuous reservoirs predicted by seismic, water saturation, TOC, total gas content, porosity, and brittleness index to divide favorable areas and select related parameters. The thickness of Class I continuous reservoirs and related parameters are closely related to production capacity, and the applicable effect is very good. In the past, high-quality shales predicted by seismic were used for comprehensive evaluation, and the thickness of Class I continuous reservoirs and related parameters were never used for evaluation. In addition, shale gas did not use seismic prediction of water saturation in the past. The present invention adds a water saturation parameter, which has a control factor in shale gas reservoirs. In general, this method considers the thickness of Class I continuous reservoirs and related parameters, which is more reasonable and reliable. In addition, the water saturation parameter is considered in the evaluation, making the invention more practical and reliable.

Description

Technical Field

[0001] The invention belongs to the field of exploration technology, and in particular relates to a method for dividing favorable areas based on shale gas exploration prediction. Background Art

[0002] Shale gas is an unconventional natural gas rich in organic matter and stored in organic-rich shales. Its development is of great significance to the transformation of the global energy structure.

[0003] In petroleum exploration, accurate evaluation and division of favorable areas is of great significance for the development of oil and gas fields. For shale gas, the division of favorable areas is even more important.

[0004] Conventional classification utilizes reservoir characteristics analysis, structure and fault evaluation, resource estimation, resource quality evaluation, cost-benefit analysis, etc.; however, the evaluation of shale gas and tight gas is not targeted and is not closely related to production capacity. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for dividing favorable areas based on shale gas exploration prediction, evaluates the close relationship between shale gas and production capacity, completes the accurate division of favorable areas, and accurately guides the later shale gas production.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for dividing favorable areas based on shale gas exploration prediction, comprising the steps of:

[0007] S100: Acquire 3D seismic time domain gather data and well data of the work area, as well as ground elevation data;

[0008] S201: performing time migration processing on the 3D seismic time domain gather data to obtain time migration data in the time domain; and obtaining the horizon data of the target layer using the time migration data;

[0009] S202: converting the 3D seismic time domain gather data into angle gather data;

[0010] S203: Obtaining the correlation between density, velocity or wave impedance related to seismic in the well data, and determining the optimal correlation parameter;

[0011] S300: using the stratigraphic data of the target layer and combining it with the optimal correlation parameter, an elastic parameter body is obtained through inversion;

[0012] S401: interpreting the plane distribution of the fault according to the phase characteristics of the stratigraphic data of the target layer, obtaining a plane distribution map of the fault, and performing classification to obtain faults of various levels; using the velocity body in the elastic parameter body, converting the stratigraphic data of the target layer into depth domain data by multiplying the elastic parameter body and the velocity body; and obtaining a burial depth result by adding the depth domain data to the ground elevation data;

[0013] S402: Use the sample point statistical method to obtain the thickness of Class I continuous reservoirs;

[0014] S403: using the fitting method to obtain other parameters of the type I continuous reservoir, including T0C, total gas content, porosity and water saturation;

[0015] S404: Calculate the Young's modulus and Poisson's ratio using the elastic parameter body, and then take the average of the two to obtain the brittleness index;

[0016] S500: The reservoir is divided into favorable areas of different levels using the results of burial depth, Class I continuous reservoir thickness, T0C, total gas content, porosity, water saturation brittleness index and the set reservoir division evaluation standard values.

[0017] Furthermore, the stratigraphic data of the target layer is picked up based on the wave group characteristics, wave group relations and reflection characteristics on the time offset data to obtain the stratigraphic data of the target layer.

[0018] Furthermore, the correlation between density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio related to seismic in the well data is obtained, including: selecting well data of a Class I continuous reservoir section, and performing a histogram analysis on it and the density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio; determining through the histogram analysis which parameter of the well and the seismic or the calculation result of the parameter can separate the Class I continuous reservoir from the non-reservoir, as the optimal correlation parameter.

[0019] Furthermore, by utilizing the stratigraphic data of the target layer and combining it with the optimal correlation parameters, an elastic parameter body is obtained through inversion, and it is determined that the elastic parameter body directly related to the well and the earthquake includes density, longitudinal wave velocity and transverse wave velocity. The longitudinal-to-straight wave velocity ratio is the result of the longitudinal wave velocity or transverse wave velocity calculation.

[0020] Furthermore, the velocity body in the elastic parameter body is inverted to obtain the target layer, and the burial depth result is obtained by adding the layer position in the depth domain to the ground altitude. The plane distribution of the fault is interpreted according to the phase characteristics of the target layer of the offset data to obtain the plane distribution map of the fault.

[0021] Furthermore, when the sample point statistical method is used to obtain the Class I continuous reservoir thickness results, the Class I continuous reservoir thickness results are obtained by extracting the thickness of the sample point*P-wave velocity body.

[0022] Furthermore, other parameters of the Class I continuous reservoir, including TOC, total gas content, porosity and water saturation, are obtained by fitting, including: fitting the on-well TOC, total gas content, porosity and water saturation with the on-well density or velocity, finding out which of the on-well TOC, total gas content, porosity and water saturation has the highest correlation with the velocity or density, and finding the corresponding relationship, and using the relationship to calculate the TOC, total gas content, porosity and water saturation.

[0023] Furthermore, the evaluation criteria for the first type of favorable areas are: burial depth less than 500 meters, thickness of the Class I continuous reservoir greater than or equal to 10 meters, TOC greater than 3%, total gas content greater than 3%, porosity greater than 4%, water saturation less than or equal to 40%, and brittleness index greater than 55%;

[0024] The evaluation criteria for Class II favorable areas are: burial depth less than 500 meters, Class I continuous reservoir thickness less than 10 meters, TOC greater than 2% and less than 3%, total gas content greater than 2% and less than 3%, porosity greater than 3% and less than 4%, water saturation greater than 40%, and brittleness index greater than 45% and less than 55%.

[0025] The beneficial effects of adopting this technical solution are:

[0026] The present invention utilizes the thickness of Class I continuous reservoirs, water saturation, TOC, total gas content, porosity, and brittleness index predicted by seismic to divide favorable areas and select related parameters. The thickness of Class I continuous reservoirs and related parameters are closely related to production capacity, and the applicable effect is very good. In the past, high-quality shales predicted by seismic were used for comprehensive evaluation, and the thickness of Class I continuous reservoirs and related parameters were never used for evaluation. In addition, shale gas did not use seismic prediction of water saturation in the past. The present invention adds a water saturation parameter, which has a control factor in shale gas reservoirs. In general, this method considers the thickness of Class I continuous reservoirs and related parameters, which is more reasonable and reliable. In addition, the water saturation parameter is considered in the evaluation, making the invention more practical and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic flow chart of a method for dividing favorable areas based on shale gas exploration prediction of the present invention;

[0028] Figure 2 Graph 1 is a histogram of longitudinal wave velocity, shear wave velocity, ratio of longitudinal and shear wave velocities, and density in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described below with reference to the accompanying drawings.

[0030] In this embodiment, see Figure 1 As shown, the present invention proposes a method for dividing favorable areas based on shale gas exploration prediction, comprising the steps of:

[0031] S100: Acquire 3D seismic time domain gather data and well data of the work area, as well as ground elevation data;

[0032] S201: performing time migration processing on the 3D seismic time domain gather data to obtain time migration data in the time domain; and obtaining the horizon data of the target layer using the time migration data;

[0033] Specifically, the stratigraphic data of the target layer is picked up based on the wave group characteristics, wave group relations and reflection characteristics on the time migration data to obtain the stratigraphic data of the target layer.

[0034] S202: Convert the 3D seismic time domain gather data into angle gather data.

[0035] S203: Obtaining the correlation between density, velocity or wave impedance related to seismic in the well data, and determining the optimal correlation parameter;

[0036] Specifically, the correlation between density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio related to seismic in the well data is obtained, including: selecting well data of a Class I continuous reservoir section, and performing a histogram analysis on it and the density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio; determining through the histogram analysis which parameter of the well and the seismic or the calculation result of the parameter can separate the Class I continuous reservoir from the non-reservoir, as the optimal correlation parameter.

[0037] S300: using the stratigraphic data of the target layer and combining it with the optimal correlation parameter, an elastic parameter body is obtained through inversion;

[0038] By using the stratigraphic data of the target layer and combining it with the optimal correlation parameters, an elastic parameter body is obtained through inversion, and it is determined that the elastic parameter body directly related to the well and the earthquake includes density, longitudinal wave velocity and transverse wave velocity. The longitudinal-to-straight wave velocity ratio is the result of the longitudinal wave velocity or transverse wave velocity calculation.

[0039] like Figure 2 As shown in the figure, it can be clearly seen that density can distinguish the type I continuous reservoir and non-reservoir segment well, and the P-wave velocity and S-wave velocity as well as the P-wave and S-wave velocity ratios of the type I continuous reservoir and non-reservoir segment overlap more and cannot be effectively separated.

[0040] S401: Interpret the planar distribution of the faults according to the phase characteristics of the stratigraphic data of the target layer, obtain a plane distribution map of the faults, and classify them to obtain faults of various levels; use the velocity body in the elastic parameter body to convert the stratigraphic data of the target layer into depth domain data by multiplying the elastic parameter body and the velocity body; use the depth domain data and the ground elevation data to add to obtain the burial depth result.

[0041] Specifically, the velocity body in the elastic parameter body is inverted to obtain the target layer, and the burial depth result is obtained by adding the layer position in the depth domain to the ground altitude. The plane distribution of the fault is interpreted according to the phase characteristics of the target layer of the offset data to obtain the plane distribution map of the fault.

[0042] S402: Use the sample point statistical method to obtain the thickness of Class I continuous reservoirs;

[0043] Specifically, when the sample point statistical method is used to obtain the Class I continuous reservoir thickness results, the Class I continuous reservoir thickness results are obtained by extracting the thickness of the sample point*P-wave velocity body.

[0044] S403: using the fitting method to obtain other parameters of the type I continuous reservoir, including T0C, total gas content, porosity and water saturation;

[0045] Specifically, other parameters of the Class I continuous reservoir, including TOC, total gas content, porosity and water saturation, are obtained by fitting, including: fitting the on-well TOC, total gas content, porosity and water saturation with the on-well density or velocity, finding out which of the on-well TOC, total gas content, porosity and water saturation and velocity or density has the highest correlation, finding out the corresponding relationship, and using the relationship to calculate TOC, total gas content, porosity and water saturation.

[0046] S404: Calculate the Young's modulus and Poisson's ratio using the elastic parameter body, and then take the average of the two to obtain the brittleness index;

[0047] Specific:

[0048] Young's modulus:

[0049] Poisson's ratio:

[0050] S500: The reservoir is divided into favorable areas of different levels using the results of burial depth, Class I continuous reservoir thickness, T0C, total gas content, porosity, water saturation brittleness index and the set reservoir division evaluation standard values.

[0051] Specific:

[0052] The evaluation criteria for Class I favorable areas are: burial depth less than 500 meters, Class I continuous reservoir thickness greater than or equal to 10 meters, TOC greater than 3%, total gas content greater than 3%, porosity greater than 4%, water saturation less than or equal to 40%, and brittleness index greater than 55%;

[0053] The evaluation criteria for Class II favorable areas are: burial depth less than 500 meters, Class I continuous reservoir thickness less than 10 meters, TOC greater than 2% and less than 3%, total gas content greater than 2% and less than 3%, porosity greater than 3% and less than 4%, water saturation greater than 40%, and brittleness index greater than 45% and less than 55%.

[0054] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for dividing favorable areas based on shale gas exploration prediction, characterized in that: Includes steps: S100: Acquire 3D seismic time domain gather data and well data of the work area, as well as ground elevation data; S201: performing time migration processing on the 3D seismic time domain gather data to obtain time migration data in the time domain; and obtaining the horizon data of the target layer using the time migration data; S202: converting the 3D seismic time domain gather data into angle gather data; S203: Obtaining the correlation between density, velocity or wave impedance related to seismic in the well data, and determining the optimal correlation parameter; S300: using the stratigraphic data of the target layer and combining it with the optimal correlation parameter, an elastic parameter body is obtained through inversion; S401: interpreting the plane distribution of the fault according to the phase characteristics of the stratigraphic data of the target layer, obtaining a plane distribution map of the fault, and performing classification to obtain faults of various levels; using the velocity body in the elastic parameter body, converting the stratigraphic data of the target layer into depth domain data by multiplying the elastic parameter body and the velocity body; and obtaining a burial depth result by adding the depth domain data to the ground elevation data; S402: Use the sample point statistical method to obtain the thickness of Class I continuous reservoirs; S403: using the fitting method to obtain other parameters of the type I continuous reservoir, including T0C, total gas content, porosity and water saturation; S404: Calculate the Young's modulus and Poisson's ratio using the elastic parameter body, and then take the average of the two to obtain the brittleness index; S500: The reservoir is divided into favorable areas of different levels using the results of burial depth, Class I continuous reservoir thickness, T0C, total gas content, porosity, water saturation brittleness index and the set reservoir division evaluation standard values.

2. The method for dividing favorable areas based on shale gas exploration prediction according to claim 1 is characterized in that: The stratigraphic data of the target layer is picked up based on the wave group characteristics, wave group relations and reflection characteristics on the time migration data to obtain the stratigraphic data of the target layer.

3. A method for dividing favorable areas based on shale gas exploration prediction according to claim 2, characterized in that: Obtaining the correlation between density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio related to seismic in the well data, including: selecting the well data of the Class I continuous reservoir section, and performing histogram analysis on it and the density, velocity or wave impedance, and longitudinal and transverse wave velocity ratio, and determining which parameter or parameter calculation result of the well and seismic can separate the Class I continuous reservoir from the non-reservoir through the histogram analysis, as the optimal correlation parameter.

4. A method for dividing favorable areas based on shale gas exploration prediction according to claim 3, characterized in that: By using the stratigraphic data of the target layer and combining it with the optimal correlation parameters, an elastic parameter body is obtained through inversion, and it is determined that the elastic parameter body directly related to the well and the earthquake includes density, longitudinal wave velocity and transverse wave velocity. The longitudinal-to-straight wave velocity ratio is the result of the longitudinal wave velocity or transverse wave velocity calculation.

5. The method for dividing favorable areas based on shale gas exploration prediction according to claim 1 is characterized in that: The velocity body in the elastic parameter body is inverted to obtain the target layer. The burial depth is obtained by adding the layer position in the depth domain to the ground altitude. The plane distribution of the fault is interpreted according to the phase characteristics of the target layer of the offset data to obtain the plane distribution map of the fault.

6. The method for dividing favorable areas based on shale gas exploration prediction according to claim 1, characterized in that: When the sample point statistical method is used to obtain the Class I continuous reservoir thickness results, the Class I continuous reservoir thickness results are obtained by extracting the thickness of the sample point*P-wave velocity body.

7. The method for dividing favorable areas based on shale gas exploration prediction according to claim 1, characterized in that: The fitting method is used to obtain other parameters of the Class I continuous reservoir, including T0C, total gas content, porosity and water saturation, including: fitting the well T0C, total gas content, porosity and water saturation with the well density or velocity, finding out which of the well T0C, total gas content, porosity and water saturation has the highest correlation with the velocity or density, and finding the corresponding relationship, and using the relationship to calculate T0C, total gas content, porosity and water saturation.

8. The method for dividing favorable areas based on shale gas exploration prediction according to claim 1 is characterized in that: The evaluation criteria for Class I favorable areas are: burial depth less than 500 meters, Class I continuous reservoir thickness greater than or equal to 10 meters, TOC greater than 3%, total gas content greater than 3%, porosity greater than 4%, water saturation less than or equal to 40%, and brittleness index greater than 55%; The evaluation criteria for Class II favorable areas are: burial depth less than 500 meters, Class I continuous reservoir thickness less than 10 meters, TOC greater than 2% and less than 3%, total gas content greater than 2% and less than 3%, porosity greater than 3% and less than 4%, water saturation greater than 40%, and brittleness index greater than 45% and less than 55%.

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