The knowledge of velocity model not even along well but at offset is key for building of VSP-CDP image. And the task is more difficult in situations of lateral variations of the media properties. The quality of obtained image is in a straight dependence on quality of reference model. And it is the main reason to obtain adequate reference model for offset-VSP processing. The main idea of method suggested in this paper is in reverse extrapolation of time-field of primary downing wave in the media based on first break hodograph and velocity model defined along the well with the specific dip for all layers of the model. Then back propagation seismic problem is solved based on extrapolated time-field and resulting wave field is stacked to primary reflectivity trace. In these calculations dip of layers is variable. Then one must make interpretation of obtained scope of refectivity traces, using the following rule: largest amplitude in trace corresponds to the true layer dip at a given depth. After that discovered values can be stacked in one trace which is to correspond to the multi-dipped layer model.


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