[0053] Example 1
[0054] The working area of 3D seismic data is 5.6km 2 , A1 exploratory well has been drilled, and well A1 has discovered oil reservoirs in three types of AVO "bright spots" characteristic reservoir areas. At most four sets of sand bodies are developed in the target layer of sand and mudstone thin interbeds in this work area. Forward modeling has confirmed that the seismic reflection waves on the top of the thin interbeds are interfered by the reflections of the thin interbeds to a relatively small extent, which makes the formation of a relatively high level on the top of the thin interbeds. Strong seismic reflection event axis. If the sand body on the top surface of the thin interbed contains oil, the difference in wave impedance between the upper and lower strata will increase, forming a "bright spot" feature event axis on the top surface; if the middle sand body in the thin interbed contains oil, the thin interbed contains oil The sandstone reservoir is disturbed by the reflection waves from the upper and lower sand and mudstone interfaces of the thin interbed, and there will be no "bright spot" reflection characteristics on the event axis. The previous reservoir identification methods are unable to effectively identify the "non-bright spot" reservoirs that may exist in the three types of AVO "bright spot" characteristic reservoir areas.
[0055] In this embodiment, the method for identifying "non-bright spot" reservoirs in the three types of AVO "bright spot" characteristic reservoir areas, the specific steps are as follows:
[0056] 1) The reflection coefficient sequence is calculated according to the logging data, and the theoretical wavelet is used for convolution of the reflection coefficient sequence to generate a synthetic seismic record; the waveform of the synthetic seismic record is compared with the waveform of the seismic trace beside the well to make the logging data Correspond accurately with the seismic data beside the well, and obtain the geological stratification data calibrated by the synthetic seismic records, such as figure 1 As shown, 4 sets of thin interbedded sand bodies are calibrated in three wave troughs and two wave crests.
[0057] 2) According to the reflection coefficient sequence and the seismic data beside the borehole, according to the principle that the synthetic seismic record generated by the convolution and the seismic trace beside the borehole are optimally similar, a wavelet beside the borehole is calculated (see figure 2 , In the figure a, b, c are the relationship diagrams of time and amplitude, amplitude and frequency, period and frequency in order).
[0058] 3) According to the geological stratification data, the study area C top, N1s3 bottom, N1s2 bottom, N1s1 bottom, N1t bottom 5 large layers and 3 wave troughs in the main target interval are explained (see image 3 ). Among them, the large set of lithological interface is calibrated on the wave peak of the seismic profile, and the target layer of this well develops four sets of sand bodies and is calibrated on the three wave troughs of the seismic profile.
[0059] 4) Calculate the reservoir information of the target zone. The target zone can develop up to four sets of thin interbedded reservoirs. The speed, density, thickness and other information of the oil layer, water layer, and non-reservoir of the known well thin interbed Statistics, the statistical results are as follows:
[0060] Oil layer: average speed 2500m/s, average density 2.1g/cm 3 , Thickness 5.2m, time thickness 4.16ms;
[0061] Water layer: average speed 2800m/s, average density 2.2g/cm 3 , Thickness 5.2m, time thickness 3.71ms;
[0062] Mudstone: average velocity 3350m/s, average density 2.41g/cm 3 , Thickness 2.9m, time thickness 1.73ms;
[0063] According to the above statistical results, in order to clarify the seismic profile response characteristics of the "non-bright spot" reservoirs, the statistical information of the velocity, density, and thickness of the oil layer, water layer, and non-reservoir is used to fill, and establish one set, two sets, and three sets. There are four sets of two-dimensional wave impedance models for four sets of reservoirs, each of which has only one set of sand body oil-bearing. The four sets of wave impedance models are used to perform convolution operations on the four sets of wave impedance models to generate four sets of forward simulations. Reflection waveform diagram (see Figure 4 ).
[0064] In order to study the characteristics of the "non-bright spot" reservoir on the amplitude plane attribute map, combined with the sedimentary characteristics of the sand bodies in the study area, four sets of sand bodies were established. The sand bodies in the middle were pinched out and matched with the structure to form the geology of the reservoir. Model, and use the well-side channel wavelet for forward modeling to generate a three-dimensional forward modeling data volume.
[0065] 5) Extract the amplitude attribute plan view of the forward modeling data volume, and clarify the strong amplitude of the "bright spot" reservoir and the weak spot of the "non-bright spot" reservoir through the analysis of the waveform characteristics of the reflected waveform map of the forward modeling and the above-mentioned amplitude attribute plan view. Amplitude seismic reflection characteristics, and extract the amplitude attribute plan view of actual seismic data.
[0066] From Figure 4 It can be seen that when there is only one set of reservoirs, the sand body has obvious characteristics of two peaks and one valley, and the amplitude of oil-bearing increases overall, which is a typical three-type AVO "bright spot" characteristic reservoir response characteristic. When there are two sets of reservoirs, due to interference, the sand body does not have obvious features of two peaks and one valley. After the first set of sand bodies contains oil, it has strong wave trough reflection characteristics, and the second set of sand bodies contains oil and has strong wave peak reflection characteristics. , Other in-phase axes have complicated interference. When there are three sets of reservoirs, only the top interfaces of the first and third sets of sand bodies have corresponding wave trough events, and the amplitudes of the two troughs are quite different; if the top sand bodies contain oil, they have stronger two The peak-to-valley feature is a typical “bright spot” reservoir; if the second set of sand bodies contains oil, there is no obvious amplitude reflection feature, and it is a typical “non-bright spot” reservoir; if the lower sand body contains oil, it has a strong Peak reflection characteristics. When there are four sets of reservoirs, only the top interfaces of the first, third, and fourth sets of sand bodies have corresponding wave trough events, and the amplitudes of these troughs are quite different; if the first set of sand bodies contains oil, it has two strong peaks The characteristic of Jiayi valley is a typical “bright spot” reservoir; if the second sand body contains oil, there is no obvious amplitude reflection characteristic, and it is a typical “non-bright spot” reservoir; if the third sand body contains oil, there is no obvious amplitude The reflection feature is a typical "non-bright spot" reservoir; if the fourth set of sand bodies contains oil, it has strong wave crest reflection characteristics and is a typical "bright spot" reservoir.
[0067] Extract the amplitude attribute slice map from the forward data volume (see Figure 5 In the figure, (a) is the forward model, (b) is the forward seismic profile, (c) is the seismic attribute plan), it is clear that the “bright spot” reservoir formed by the top sand body and the middle sand body formed by oil The seismic attribute plan feature of the “non-bright spot” reservoir, and the amplitude attribute plan of actual seismic data is extracted according to the feature guidance (see Image 6 ).
[0068] 6) According to the lithological structure and wave impedance characteristics of the thin interbeds of the forward model, construct 7 pseudo wells with 4 sets of thin interbeds, and construct 5 sets of middle sands with reference to the plane distribution map of the pinch-out line of the middle sand body. Fake wells with missing volumes; based on the wave impedance data of the pseudo wells, combined with the time horizon of the macroscopic large set of lithological interfaces in the study area explained in step 3), establish the initial model of inversion wave impedance, and use the wave impedance data and inversion The initial model of impedance modeling and the seismic data of forward modeling are used to select the inversion parameters sensitive to the "non-bright spot" reservoir by using the constrained sparse pulse inversion algorithm, which is applied to the impedance inversion of actual seismic data (see Figure 7 );
[0069] 7) Extract the wave impedance inversion result of actual seismic data from the wave impedance inversion attribute slice map parallel to the interpretation horizon (see Figure 8 ), where A1 and B1 oil wells are located in areas with lower wave impedance, but through Image 6 with Figure 8 The comparative analysis shows that the B1 oil well is located in an area with weak seismic amplitude.
[0070] It can be seen that the seismic inversion wave impedance planar attribute map can not only reflect the planar distribution characteristics of the "bright spot" characteristic reservoir, but also reflect the planar distribution characteristics of the "non-bright spot" reservoir, and the seismic amplitude attribute plan can clearly Reflects the planar distribution characteristics of "bright spot" reservoirs, but there are greater limitations in reflecting "non-bright spot" reservoirs.
[0071] Through the above comprehensive research of forward and inversion, the "non-bright spot" reservoirs were finally identified in the three types of AVO "bright spot" characteristic reservoir areas, indicating that the reservoir identification method in this example is in terms of finding "non-bright spot" hidden reservoirs It can improve the accuracy of reservoir prediction, has achieved good application effects, and has certain reliability.
