A continuation imaging method suitable for crosswell seismic large-angle reflection conditions

Abstract

The invention discloses a continuation imaging method suitable for interwell seismic large-angle reflection conditions. In the case of removing the direct wave, the seismic source wave field extends laterally toward the geophone direction, and the geophone receiving wave field extends laterally toward the seismic source direction. , when the two wave fields are extended to the same position, the relevant imaging conditions are used for imaging, so as to realize lateral extension imaging; imaging and superposition of all shot points can obtain the cross-well seismic depth domain migration imaging section. The invention converts the large-angle propagation information into a small angle in the direction of lateral extension, thereby improving the imaging effect of the vertical large-angle area. There is no need to separate uplink and downlink reflection waves, which avoids the impact of poor separation of uplink and downlink reflection waves on imaging results; it not only considers the kinematic characteristics of crosswell seismic reflection data (time information, etc.), but also considers crosswell seismic reflection Due to the dynamic characteristics of the wave data (amplitude information, etc.) and the particularity of the cross-well seismic observation method, the imaging is accurate and the precision is high.

Description

technical field [0001] The invention belongs to the technical field of seismic data processing, and in particular relates to a continuation imaging method suitable for cross-well seismic large-angle reflection conditions. Background technique [0002] Due to the special observation method of crosswell seismic, the reflected wave imaging methods are generally divided into VSP-CDP imaging, travel time field continuation imaging and wave equation continuation migration imaging and other technologies. The VSP-CDP imaging method is a commonly employed method. The advantage of VSP-CDP imaging is that the algorithm is stable and easy to implement, but its disadvantages are also obvious. The main reason is that the method is based on the assumption of a horizontal layered constant velocity medium, so the imaging accuracy is low. The POSTMAP imaging of crosswell seismic is based on the VSP-CDP imaging results to further converge the diffracted waves. The effect is better than that o...

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Problems solved by technology

The advantage of VSP-CDP imaging is that the algorithm is stable and easy to implement, but its disadvantages are also obvious. The main reason is that the method is based on the assumption of a horizontal layered constant velocity medium, so the imaging accuracy is low

The POSTMAP imaging of crosswell seismic is based on the VSP-CDP imaging results to further converge the diffracted waves, and the effect is better than VSP-CDP, which is equivalent to the Kirchhoff integral method, but it is difficult to adapt to the strong lateral changes of the velocity field

At the same time, since crosswell seismic reflections are mainly large-angle reflections, there are a large number of wide-angle reflections exceeding the critical angle. However, the current crosswell seismic wave equation migration method adopts the idea of ​​vertical continuation for wavefield continuation imaging, and It is not suitable for cross-well seismic reflection conditions close to wide-angle. Even if a high-precision vertical wave field continuation operator is used, the imaging effect of large-angle steep-dip structures is still affected, especially near the two wells, where the vertical continuation of the one-way wave Imaging is very difficult

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