Method and system for calculating activity rate of oil reservoir group level fault

Abstract

The invention provides a calculation method and system for the activity rate of an oil reservoir group level fault. The calculation method comprises the steps that natural gamma curves of all oil reservoir groups of a preset target layer are sampled at equal intervals; performing spectral analysis on the selected natural gamma curve, and determining that the natural gamma curve has Mie astronomical cycle information; performing filtering analysis on the selected natural gamma curve to obtain a filtering result of the Mie's astronomical cycle information, and calculating the deposition time limit of the stratum of the corresponding oil reservoir group; obtaining the stratum apparent thickness with stable hanging wall and footwall near the fault, performing dip angle correction on the stratum apparent thickness to obtain the true thickness of the hanging wall and footwall stratum of the fault, and calculating the fall of the true fault; and based on the obtained true fault fall and the stratum deposition time limit of the corresponding oil reservoir group, calculating the activity rate of the oil reservoir group level fault. According to the method, the activity of the fault corresponding to a higher-level stratum is analyzed, the calculation precision of the activity rate of the fault is improved, and a higher-level and finer technical method is provided for the analysis of the fracture activity of an oil field.

Description

Technical Field

[0001] The invention belongs to the field of oil and natural gas exploitation, and in particular relates to a method and system for calculating the fault activity rate at the oil layer group level. Background Art

[0002] As the exploration and development of oil and gas fields become more refined, the thickness of the formation is divided into smaller and smaller parts, and the scale of fault research is correspondingly smaller and smaller. The fault drop of a certain period is usually used to indicate the fault activity of that period. However, due to the differences in the thickness and deposition time of the formations in different periods, when the fault drop is used to analyze the differences in fault activity in different periods, there is incomparability. For example, the fault drop of the A formation during the deposition period is 30m, and the deposition time is 3Ma; the fault drop of the B formation during the deposition period is 50m, and the deposition time is 5Ma; if the fault drop is used to compare the difference in fault activity between the A and B periods, then the fault activity in the B period is stronger than that in the A period, but in essence, the fault activity rate in the A and B periods is 10m / Ma, and the fault activity of the two periods is the same, so the fault activity rate needs to be used to analyze the fault activity.

[0003] There are currently two main problems in the study of fault activity at the oil layer group level: one is the determination of the depositional time limit of a certain oil layer group, and the other is that the difference in vertical thickness between the upper and lower plates of the fault should be the apparent fault throw, and the true fault throw should be obtained by using the difference in true thickness between the upper and lower plates of the fault.

[0004] The present application forms a method for calculating the fault activity rate at the oil layer group level, adopts the Michaelis astronomical cycle method to calculate the deposition time limit of the oil layer group, and uses the formation dip to calculate the true fault drop, so as to realize the calculation of the fault activity rate at the oil layer group level. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a method and system for calculating the fault activity rate at the oil layer group level, so as to solve the problem of how to determine the deposition time limit of the oil layer group and the true fault drop.

[0006] In a first aspect, an embodiment of the present invention provides a method for calculating the fault activity rate at the oil layer group level, comprising:

[0007] Step 1, sampling the natural gamma curves of each oil layer group of the preset target layer at equal intervals;

[0008] Step 2, perform spectrum analysis on the selected natural gamma-ray curve to determine whether it contains Mie astronomical cycle information;

[0009] Step 3: Filter and analyze the selected natural gamma curve to obtain the filtering result of Michaelis astronomical cycle information and calculate the sedimentation time limit of the corresponding oil layer group;

[0010] Step 4, obtain the apparent thickness of the stable strata on the upper and lower walls near the fault, make inclination correction for the apparent thickness of the strata, obtain the true thickness of the strata on the upper and lower walls of the fault, and thus calculate the true fault drop;

[0011] Step 5: Calculate the fault activity rate at the oil layer group level based on the acquired true fault drop and the corresponding oil layer group stratigraphic deposition time limit.

[0012] Furthermore, the Michaelis astronomical cycle information includes eccentricity, slope, and precession period.

[0013] Furthermore, the eccentricity period is filtered to calculate the deposition time corresponding to the oil layer group, including:

[0014] Sedimentation time formula: T = n*e

[0015] Where, T is the stratigraphic deposition time, ka (thousand years); n is the number of cycles, in units; e is the eccentricity period 95ka (thousand years);

[0016] Time and depth conversion formula:

[0017] H 视 =0.0001*t 2 +0.9323*t-8.1827

[0018] Where H is the depth in meters and t is the seismic two-way reflection time in milliseconds.

[0019] Furthermore, the calculation of the true fault drop includes:

[0020] True formation thickness: H 真 =H 视 *cos(α)

[0021] In the formula, H 真 is the true thickness of the formation, in m; H 视 is the apparent thickness of the formation, in m; α is the formation dip;

[0022] True fault drop: H 真落差 =H 上盘真 -H 下盘真

[0023] In the formula, H 上盘真 is the true thickness of the fault hanging wall, H 下盘真 Further, the true thickness of the fault footwall is used to calculate the fault activity rate at the reservoir group level, including;

[0024] Fault activity rate: V = H 真落差 / T

[0025] Where V is the fault activity rate, in m / ka (meters / thousand years); H真落差 is the true fault drop, in meters; T is the stratigraphic deposition time, in ka (thousand years).

[0026] In a second aspect, a system for calculating the fault activity rate at the oil layer group level comprises:

[0027] Sampling module: perform equal-interval sampling on the natural gamma curves of each oil layer group in the preset target layer;

[0028] Determination module: Spectral analysis is performed on the selected natural gamma curve to determine whether there is Mie astronomical cycle information;

[0029] The first calculation module: filter and analyze the selected natural gamma curve, obtain the filtering result of Michaelis astronomical cycle information, and calculate the sedimentary time limit of the corresponding oil layer group;

[0030] The second calculation module: obtain the stable apparent thickness of the upper and lower plates near the fault, make inclination correction for the apparent thickness of the formation, obtain the true thickness of the upper and lower plates of the fault, and thus calculate the true fault drop;

[0031] The third calculation module: calculates the fault activity rate at the oil layer group level based on the acquired true fault drop and the corresponding oil layer group stratigraphic deposition time limit.

[0032] The embodiments of the present invention bring the following beneficial effects:

[0033] The present invention realizes the calculation of fault activity rate at the oil layer group level, realizes the analysis of fault activity corresponding to higher-level strata, improves the calculation accuracy of fault activity rate, and provides a higher-level and more sophisticated technical method for oil field fault activity analysis.

[0034] Other features and advantages of the present invention will be described in the following description, and some features will become apparent from the description or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A flow chart of a method for calculating the fault activity rate at the oil layer group level provided in an embodiment of the present invention;

[0037] Figure 2 The oil layer group level stratigraphic spectrum analysis diagram provided by the embodiment of the present invention;

[0038] Figure 3A reservoir group-level stratigraphic deposition time diagram provided by an embodiment of the present invention;

[0039] Figure 4 A schematic diagram of a true formation thickness calculation process provided by an embodiment of the present invention;

[0040] Figure 5 A fault activity rate diagram at the oil layer group level provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] To facilitate understanding of this embodiment, Figure 1 As shown, firstly, a method for calculating the fault activity rate at the oil layer group level disclosed in an embodiment of the present invention is introduced in detail.

[0043] Step 1, sampling the natural gamma curve (GR) of each oil layer group of the preset target layer at equal intervals;

[0044] Specifically, the shallow lake-deep lake mudstone sedimentary section in the study area was selected, which was less affected by tectonic activities and volcanic activities, and the natural gamma ray curve (GR) of the target layer (each oil layer group) was intercepted, and the sampling interval was set to 0.125m.

[0045] Step 2: Spectral analysis is performed on the selected natural gamma ray curve to determine the existence of Michaelis astronomical cycle information, namely, eccentricity, slope, and precession period;

[0046] Specifically: Figure 2 As shown in the figure, by performing spectral analysis on the natural gamma ray curve (GR) of the target layer, it is considered that the information with a confidence level of more than 90% is relatively reliable. By extracting information with similar ratios of eccentricity (95ka), slope (38.5ka), and precession (23ka), it is confirmed that there is Michaelis astronomical cycle information in this layer in this area.

[0047] Step 3: Filter and analyze the selected natural gamma curve to obtain the filtering result of Michaelis astronomical cycle information and calculate the sedimentation time limit of the corresponding oil layer group;

[0048] Specifically: Figure 3 As shown in Figure 2, the information of the eccentricity period is the strongest confirmed by wavelet transform. Therefore, filtering is performed on the eccentricity period to calculate the deposition time corresponding to the oil layer group.

[0049] Among them, the deposition time formula is: T = n*e

[0050] Where, T is the stratigraphic deposition time, ka (thousand years); n is the number of cycles, in units; e is the eccentricity period 95ka (thousand years);

[0051] Furthermore, the time and depth conversion formula

[0052] H 视 =0.0001*t 2 +0.9323*t-8.1827

[0053] Where H is the depth in meters and t is the seismic two-way reflection time in milliseconds.

[0054] Step 4, obtain the apparent thickness of the stable strata on the upper and lower walls near the fault, make inclination correction for the apparent thickness of the strata, obtain the true thickness of the strata on the upper and lower walls of the fault, and thus calculate the true fault drop;

[0055] Among them, the true formation thickness is: H 真 =H 视 *cos(α)

[0056] In the formula, H 真 is the true thickness of the formation, in m; H 视 is the apparent thickness of the formation, in m; α is the formation dip;

[0057] True fault drop: H 真落差 =H 上盘真 -H 下盘真

[0058] In the formula, H 上盘真 is the true thickness of the fault hanging wall, H 下盘真 is the true thickness of the fault footwall.

[0059] Step 5, based on the acquired true fault drop and the bottom sedimentation time limit of the corresponding oil layer group, calculate the fault activity rate at the oil layer group level;

[0060] V=H 真落差 / T

[0061] Where V is the fault activity rate, in m / ka (meters / thousand years); H 真落差 is the true fault drop, in meters; T is the stratigraphic deposition time, in ka (thousand years).

[0062] Embodiment 2: A system for calculating the fault activity rate at the oil layer group level, comprising:

[0063] Sampling module: perform equal-interval sampling on the natural gamma curves of each oil layer group in the preset target layer;

[0064] Determination module: Spectral analysis is performed on the selected natural gamma curve to determine whether there is Mie astronomical cycle information;

[0065] The first calculation module: filter and analyze the selected natural gamma curve, obtain the filtering result of Michaelis astronomical cycle information, and calculate the sedimentary time limit of the corresponding oil layer group;

[0066] The second calculation module: obtain the stable apparent thickness of the upper and lower plates near the fault, make inclination correction for the apparent thickness of the formation, obtain the true thickness of the upper and lower plates of the fault, and thus calculate the true fault drop;

[0067] The third calculation module: calculates the fault activity rate at the oil layer group level based on the acquired true fault drop and the corresponding oil layer group bottom sedimentation time limit.

[0068] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0069] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the fault activity rate at the oil layer group level, characterized in that: The following steps are included: Step 1, sampling the natural gamma curves of each oil layer group of the preset target layer at equal intervals; Step 2, perform spectrum analysis on the selected natural gamma-ray curve to determine whether it contains Mie astronomical cycle information; Step 3: Filter and analyze the selected natural gamma curve to obtain the filtering result of Michaelis astronomical cycle information and calculate the sedimentation time limit of the corresponding oil layer group; Step 4, obtain the apparent thickness of the stable strata on the upper and lower walls near the fault, make inclination correction for the apparent thickness of the strata, obtain the true thickness of the strata on the upper and lower walls of the fault, and thus calculate the true fault drop; Step 5: Calculate the fault activity rate at the oil layer group level based on the acquired true fault drop and the corresponding oil layer group stratigraphic deposition time limit.

2. The method for calculating the fault activity rate at the oil layer group level according to claim 1, characterized in that: The Michaelis astronomical cycle information includes eccentricity, slope, and precession period.

3. According to the method for calculating the fault activity rate at the oil layer group level according to any one of claims 1-2, in step 3, filtering analysis is performed on the selected natural gamma curve, characterized in that: The eccentricity period is filtered to calculate the deposition time corresponding to the oil layer group. Sedimentation time formula: T = n*e, Where, T is the stratigraphic deposition time, ka (thousand years); n is the number of cycles, in units; e is the eccentricity period 95ka (thousand years); Time and depth conversion formula: H 视 =0.0001*t 2 +0.9323*t-8.1827, Where H is the depth in meters and t is the seismic two-way reflection time in milliseconds.

4. The method for calculating the fault activity rate at the oil layer group level according to claim 1, wherein the true fault drop is calculated in step 4, characterized in that: True formation thickness: H 真 =H 视 *cos(α), In the formula, H 真 is the true thickness of the formation, in m; H 视 is the apparent thickness of the formation, in m; α is the formation dip; True fault drop: H 真落差 =H 上盘真 -H 下盘真 , In the formula, H 上盘真 is the true thickness of the fault hanging wall, H 下盘真 is the true thickness of the fault footwall.

5. The method for calculating the fault activity rate at the oil layer group level according to claim 1, wherein the calculation of the fault activity rate at the oil layer group level in step 5 is characterized in that: Fault activity rate: V = H 真落差 / T, Where V is the fault activity rate, in m / ka (meters / thousand years); H 真落差 is the true fault drop, in m; T is the stratigraphic deposition time, in ka (thousand years).

6. A system using the method for calculating the fault activity rate at the oil layer group level according to claims 1 to 5, characterized in that: include: Sampling module: perform equal-interval sampling on the natural gamma curves of each oil layer group in the preset target layer; Determination module: Spectral analysis is performed on the selected natural gamma curve to determine whether there is Mie astronomical cycle information; The first calculation module: filter and analyze the selected natural gamma curve, obtain the filtering result of Michaelis astronomical cycle information, and calculate the sedimentary time limit of the corresponding oil layer group; The second calculation module: obtain the stable apparent thickness of the upper and lower plates near the fault, make inclination correction for the apparent thickness of the formation, obtain the true thickness of the upper and lower plates of the fault, and thus calculate the true fault drop; The third calculation module: calculates the fault activity rate at the oil layer group level based on the acquired true fault drop and the corresponding oil layer group stratigraphic deposition time limit.

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