The Study On Velocity Analysis And Imaging Method Of Deviated VSP

VSP is a method of seismic exploration which observe in a well. Comparing with the conventional seismic survey methods, VSP has the higher S/N and resolution. And the feature of kinematics and dynamics of wave is more evident. Moreover, VSP can provide accurate time-depth conversion and velocity model for processing and interpreting of seismic data. So this technology is widely used in petroleum exploration.The conventional VSP aimed at vertical well primarily. With the development of this technology, there are a variety of VSP technology, such as Walk Way VSP, opposite VSP and 3D VSP. But VSP technology includes vertical wells VSP and deviated VSP if it is sorted by the gradient of wells. Deviated VSP is attracting our more and more attention because it is more tightly combined with practice than vertical wells VSP.The conventional velocity analysis is mainly based on the first break time. The defects of these methods are that it can only get the deepest strata above the rate of detection. But it is powerless to get the deepest point of the following ground speed detection. The velocity analysis method we brought, which is based on hyperbolic correction is a method just using the reflected wave estimate velocity. Due to the information the reflected wave contained, it have resolved detection point below the deepest formation rate of reflection.The basic idea is that we get RMS velocity in accordance with the idea of the seismic velocity scanning after correcting VSP records to the ground. We used a second order approximation in the conversion processing. For the flat ground, the velocity we got is RMS velocity which is related to the seismic stacking velocity. So it combines VSP with the surface seismic method organically.The VSPCDP imaging method which based on vertical well is also applicable deviated VSP, and the difference is we need consider the deviation factors when imaging. The traditional VSPCDP imaging method is put forward by Wyatt in 1981. It is also a VSP imaging method which is using the known velocity model under some certain constraints ray tracing, and obtains the distribution of reflection points, images at last. The key of that is velocity. So that is, the more accurate velocity has, the better it images. The surface stack based on the ray tracing method is an adaptive imaging method which can images when acquiring velocity. Through human-computer interaction, it can get better imaging effects.This article firstly synthesizes the theory deviated VSP records of the different models using the ray tracing method. On this basis, this article has achieved the conventional velocity analysis and VSPCDP imaging methods. And we written the interactive velocity picking software which is based on hyperbolic correction. At last, we get better results according to the theory and real data calculation.