Extra-high-resolution seismic space aliasing removal seismic interpretation method

Abstract

The invention discloses an extra-high-resolution seismic de-aliasing seismic interpretation method. The method comprises the following steps of performing conventional low-frequency three-dimensional seismic data horizon interpretation; reducing the time construction dip angle of the horizon data; smoothing the horizon data to form a trend surface horizon data body after horizon smoothing; leveling the extra-high-resolution seismic data volume by using a structural trend surface horizon; performing subdivision horizon interpretation on the extra-high-resolution seismic data body without spatial aliasing after structural trend surface horizon leveling processing; removing structure trend surface horizon leveling, and recovering the original sample of the extra-high-resolution seismic structure horizon; performing vertical interpolation on the horizon data to form new horizon data; and extracting the amplitude of the ultrahigh-resolution seismic data body along the layer. The method is used for geophysical extra-high-resolution seismic horizon interpretation in oil-gas exploration and development, and the problem that seismic horizon interpretation is difficult due to serious extra-high-resolution seismic spatial aliasing is solved.

Description

Technical fields:

[0001] This invention relates to the field of seismic exploration in oil and gas exploration and development, and belongs to a method for interpreting seismic horizons by removing spatial pseudofrequency in ultra-high resolution seismic data. Background technology:

[0002] To meet the needs of thin-layer oil and gas reservoir exploration and development, a broadband ultra-high resolution seismic processing method was developed. The apparent dominant frequency of the seismic waves was increased from 30Hz to over 100Hz, and the vertical resolution was significantly improved. Calculated using a quarter-wavelength vertical resolution, the vertical resolution of the 3600m / s velocity segment increased from 30m to 3-9m. Although the reflective layers in areas with small structural dip angles are clearly imaged on broadband ultra-high resolution seismic profiles, significant spatial aliasing exists in areas with large structural dip angles. The presence of spatial aliasing in ultra-high resolution seismic profiles distorts the reflection signals at large dip angles, and causes overlapping reflection signals from adjacent different layers, making stratigraphic interpretation difficult. The formula to eliminate spatial aliasing is: Δx ≤ V ÷ (4Fmax × tan(θ)), where Δx is the trace spacing, V is the velocity, Fmax is the maximum apparent dominant frequency, and θ is the structural dip angle.

[0003] Conventional 3D seismic data exhibits low apparent dominant frequencies, and spatial aliasing is generally absent on 3D seismic profiles, making the CDP (Content Parameter Table) parameters of 3D seismic acquisitions reasonable. However, ultra-high resolution (UHMR) seismic data shows a significantly increased apparent dominant frequency, leading to severe spatial aliasing in areas with large structural dips. Formulas for eliminating spatial aliasing indicate that acquisition parameters suitable for low-frequency seismic data are generally too large for UHMR seismic acquisitions using current 3D seismic acquisition methods. To overcome spatial aliasing in UHMR data, it is necessary to densify the seismic sampling trace spacing during field 3D seismic data acquisition and to perform trace interpolation to further densify the trace spacing during 3D seismic data processing. Since spatial aliasing in UHMR is not noise but rather a seismic display issue, seismic data interpretation requires research into UHMR display methods. Formulas for eliminating spatial aliasing show that reducing the displayed stratigraphic dip angle can overcome spatial aliasing. Therefore, this invention proposes a seismic stratigraphic interpretation method for eliminating spatial aliasing in UHMR data. Summary of the Invention:

[0004] The technical problem to be solved by this invention is the problem of spatial aliasing affecting the interpretation of seismic horizons in ultra-high resolution earthquakes.

[0005] The applicable technical solution is: a method for interpreting ultra-high resolution seismic data to remove spatial spurious frequencies, comprising the following steps:

[0006] Stratigraphic interpretation of conventional low-frequency 3D seismic data forms stratigraphic data Ta( Figure 1The time-structure dip angle of the stratigraphic data Ta is reduced to form stratigraphic data Tb, with the formula Tb = K × Ta, where K is a constant, generally greater than 0 and less than 1. The stratigraphic data Tb is smoothed to form a smoothed structural trend surface stratigraphic data volume Tb-p. The smoothing parameters are generally 6 trace spacings and 6 line spacings. The structural trend surface stratigraphic data Tb-p is used to flatten the structural trend surface stratigraphic layers of the ultra-high resolution seismic data volume, reducing the stratigraphic dip angle and forming an ultra-high resolution seismic data volume without spatial aliasing. Further subdivision of the stratigraphic interpretation is then performed on the flattened ultra-high resolution seismic data volume without spatial aliasing, forming subdivided stratigraphic data volumes such as Ta-1, Ta-2, and Ta-3. A vertically magnified scale is displayed before stratigraphic interpretation to make the ultra-high resolution seismic reflection layers and inter-layer faults clearer. Figure 2 The structural trend surface was removed and the layer was flattened to restore the original structure of the ultra-high resolution seismic data, and the interpretation results of the Ta-1, Ta-2, and Ta-3 layers were displayed. The Ta-1 and Ta-2 layer data were vertically interpolated to form the Ta-1-1 layer data. The volume amplitude of the ultra-high resolution seismic data was extracted along the Ta-1-1 layer for the compilation of the amplitude attribute analysis along the layer of the 3-5m thin reservoir.

[0007] The beneficial effects of this method are as follows: by reducing the dip angle of the stratigraphic structure and flattening the tectonic trend surface, this method eliminates spatial aliasing in ultra-high resolution seismic data, increases the visibility of thin strata of 3-9m, enhances the continuity of seismic horizons, and better leverages the ability of ultra-high resolution seismic data to reveal subsurface reflection information. This solves the problem that severe spatial aliasing in ultra-high resolution seismic data makes it impossible to interpret seismic horizons and identify thin reservoirs. Attached image description:

[0008] Figure 1 This is a conventional low-frequency 3D seismic profile with a dominant seismic frequency of 30Hz, showing Ta layers. The horizontal axis represents the CDP trace number, with a CDP trace spacing of 25m, and the vertical axis represents time in milliseconds, with a time sampling rate of 1ms.

[0009] Figure 2 This is an ultra-high resolution 3D seismic profile with a dominant seismic frequency of 300Hz. The left side is an ultra-high resolution 3D seismic profile with severe spurious frequencies, showing the Ta layer. The right side is an ultra-high resolution 3D seismic profile of the target layer after flattening the tectonic trend surface to remove spatial spurious frequencies, showing the interpretation results of the subdivided Ta-1, Ta-2, and Ta-3 layers. Detailed implementation method:

[0010] The invention will be further described below with reference to the accompanying drawings: The invention proposes a method for interpreting seismic horizons by flattening ultra-high resolution seismic tectonic trend surfaces and eliminating spatial spurious frequencies, comprising the following steps:

[0011] (1) Stratigraphic interpretation of conventional low-frequency 3D seismic data, forming stratigraphic data Ta( Figure 1 Conventional low-frequency 3D seismic data have low apparent dominant frequencies, no spatial false frequencies, strong reflection amplitudes of the target layer, and are easy to interpret by layer correlation.

[0012] (2) Reduce the time dip angle of the stratigraphic data Ta to form stratigraphic data Tb. The formula is Tb=K×Ta, where K is a constant, which is generally greater than 0 and less than or equal to 1. In this example, K=0.9;

[0013] (3) Smooth the stratigraphic data Tb to form the stratigraphic data volume Tb-p of the constructed trend surface after stratigraphic smoothing. The smoothing interval parameter is generally 6 traces in the trace direction and 6 lines in the line direction. The smoothing interval can be reduced or increased according to different needs. The criterion is that the time difference between Tb and Tb-p can reflect the characteristics of micro-amplitude structures and small faults. For example, there is a time difference of 2-5ms between Tb and Tb-p;

[0014] (4) Applying the structural trend surface layer data Tb-p to flatten the structural trend surface layer of the ultra-high resolution seismic data volume reduces the stratigraphic dip angle, forming an ultra-high resolution seismic data volume without spatial aliasing. Compared with the ultra-high resolution seismic data corresponding to conventional low-frequency 3D seismic data, due to the significantly increased apparent dominant frequency (300Hz), seismic vertical resolution of 3m, and 25m*25m pixel 3D ultra-high resolution seismic data, spatial aliasing is severe in locations with large stratigraphic dip angles. Spatial aliasing appears to be high-frequency noise, but is actually a seismic display problem; after the structural trend surface layer flattening process, the spatial aliasing above and below the structural trend surface disappears. Figure 2 There is a time lag between the stratigraphic data (Ta) of conventional low-frequency 3D seismic data and the ultra-high resolution seismic reflection layer, requiring reinterpretation of the ultra-high resolution seismic stratigraphic layers.

[0015] (5) Further subdividing the ultra-high resolution seismic data volume without spatial aliasing after flattening the structural trend surface, resulting in subdivided layer interpretations such as Ta-1, Ta-2, and Ta-3 layer data volumes. Figure 2 The vertical magnification scale display before stratigraphic interpretation makes the ultra-high resolution seismic reflection layers and inter-layer faults clearer. Ultra-high resolution seismic earthquakes have many phase axes, and the large scale display is beneficial to stratigraphic interpretation.

[0016] (6) Remove the structural trend surface and flatten the strata to restore the original structure of the ultra-high resolution seismic structure and display the interpretation results of Ta-1, Ta-2, Ta-3 and other strata. In this way, the seismic interpretation strata effectively pass through the spatial false frequency zone. The cross-section comparison shows that the application of the structural trend surface and flattening treatment not only eliminates the spatial false frequency but also preserves the relative height of the strata structure.

[0017] (7) Vertical interpolation of Ta-1 and Ta-2 layer data to form Ta-1-1 layer data. The interpolation formula is Ta-1-1=(Ta-1+Ta-2) / 2. Ta-1-1 is displayed on the ultra-high resolution seismic data volume without spatial aliasing after the layer flattening of the structural trend surface.

[0018] (8) Extract the volume amplitude of ultra-high resolution seismic data along the Ta-1-1 layer to compile the amplitude attribute map along the 3-6m thin reservoir.

Claims

1. A method for interpreting ultra-high resolution seismic data without spurious frequencies, characterized in that: Includes the following steps: Stratigraphic interpretation of conventional low-frequency 3D seismic data forms stratigraphic data Ta; The temporal structural dip angle of the stratigraphic data Ta is reduced to form stratigraphic data Tb, with the formula Tb = K × Ta, where K is a constant and is generally greater than 0 and less than 1. The stratigraphic data Tb is smoothed to form a smoothed structural trend surface stratigraphic data volume Tb-p. The smoothing parameters are generally 6 traces and 6 lines. The structural trend surface stratigraphic data Tb-p is used to flatten the structural trend surface stratigraphic data volume of the ultra-high resolution seismic data volume, reduce the stratigraphic structural dip angle, and form an ultra-high resolution seismic data volume without spatial aliasing. After flattening the tectonic trend surface, the ultra-high resolution seismic data volume, free from spatial aliasing, is further subdivided into layer interpretations, forming subdivided layer data volumes such as Ta-1, Ta-2, and Ta-3. A vertically magnified scale is displayed before layer interpretation to make the ultra-high resolution seismic reflection layers and interlayer faults clearer. The tectonic trend surface flattening is removed to restore the original tectonic structure of the ultra-high resolution seismic data, displaying the interpretation results for Ta-1, Ta-2, and Ta-3 layers. Vertical interpolation of the Ta-1 and Ta-2 layer data forms the Ta-1-1 layer data. The amplitude of the ultra-high resolution seismic data volume is extracted along the Ta-1-1 layer for compiling the amplitude attribute analysis of 3-5m thin reservoir layers.

2. The method for interpreting seismic horizons by flattening ultra-high resolution seismic tectonic trend surfaces and eliminating spurious frequencies, as described in claim 1, is characterized in that: Vertical interpolation of Ta-1 and Ta-2 layer data forms Ta-1-1 layer data, with the interpolation formula being Ta-1-1=(Ta-1+Ta-2) / 2. Ta-1-1 is displayed on a high-resolution seismic data volume without spatial aliasing after the layer flattening process of the tectonic trend surface.

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