Method for comprehensively establishing initial depth interval velocity model by combining seismogeology understanding

Abstract

The invention relates to a method for comprehensively establishing an initial depth interval velocity model by combining a seismogeology understanding. According to the method, seismic data inversion, drilling and logging information, earth surface geological outcrop data, area geological information, stratum velocity changing rules and other information are comprehensively applied to establish the initial depth interval velocity model, in other words, based on seismic data inversion, the drilling and logging information, the earth surface geological outcrop data, the area geological information and the stratum velocity changing rules serve as constraints, a relatively accurate initial structure model and the interval velocity along the stratum are obtained, and thus an enforceable initial depth interval velocity modeling process is formed. According to the method, the advantages of three existing initial depth interval velocity model establishing methods are fully absorbed; meanwhile, the concept of multiple information constraints is adopted for establishing the initial depth interval velocity model, and the initial depth interval velocity model is made to be more accurate.

Description

technical field [0001] The invention belongs to the field of petroleum and natural gas seismic exploration, and more specifically, relates to a method for comprehensively establishing an initial depth layer velocity model in combination with seismic geological knowledge in the aspect of pre-stack depth migration velocity modeling, and is mainly applied to seismic data of petroleum seismic exploration Handle explanations. Background technique [0002] With the increasing degree of oil and gas exploration and the complexity of exploration objects, the requirements for the quality and accuracy of seismic migration imaging are also getting higher and higher. When the velocity of the subsurface medium has drastic lateral changes or the velocity interface is not horizontally layered, only pre-stack depth migration can realize the superposition of common reflection points and the homing of diffraction points, and correct the subsurface caused by steeply dipping strata and velocity ...

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Problems solved by technology

[0004] At present, the method of establishing the velocity model of the initial depth layer is generally based on the inversion of seismic data. There are three main methods from simple to complex. Depth domain is used as the initial depth layer velocity. The velocity accuracy of this method is reduced and the error is large. It is only suitable for seismic data with high signal-to-noise ratio and simple velocity; the second method is to use prestack time migration velocity to perform time The initial depth layer velocity obtained by deep conversion to the depth domain is more reasonable than the first method, but since the pre-stack time migration velocity is mostly reflected as the root mean square velocity, the velocity converted to the layer velocity The layer velocity may be unreasonable, resulting in low accuracy of the initial depth layer velocity velocity model, and this method is only suitable for high signal-to-noise ratio data; the third method is to use pre-stack time migration to obtain the instantaneous layer velocity, and at the same time The geological horizon is interpreted on the pre-time migration profile, the instantaneous layer velocity is extracted along the geological horizon, the time-domain layer velocity is obtained through smoothing, and the initial depth layer velocity is obtained through time-depth conversion or map migration. The advantage of the two methods is that they take into account the stratigraphic velocity, which is a better method currently recommended for velocity modeling of complex structures. However, this method is still limited by the conditions of seismic data, that is, in the case of low signal-to-noise ratio of seismic data and complex structures. In this case, the obtained instantaneous layer velocity in the time domain may also have low accuracy, which will also cause a large error in the initial depth layer velocity

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