Research Projects

3D VSP

ADAPTATIVE 3-D TOMOGRAPHY FOR VERTICAL SEISMIC PROFILES

The main goal of this project is the development of a tomographic reconstruction method for estimating 3-D velocity and the geometry of reflectors from a joint inversion of transmission and reflection travel times. The approach is to extend the traditional techniques of cross-well tomography to the 3-D VSP. The 3-D VSP has better angular coverage than cross-well tomography and the joint inversion of transmission and reflection events will provide good quantitative estimates of seismic properties that can be used to estimate the reservoir properties and the positions of structural and stratigraphic interfaces way from the well.
To be able to invert these large 3-D datasets, we propose a parameterization of the velocity model in an adaptive unstructured grid that will be adapted to model resolution. Due to the dimensions of the inverse problem, several different inversion techniques will be investigated with emphasis on techniques that are efficient on parallel Beowulf style clusters. Possible methods are Conjugated Gradient, GMRES.

Figure 1: 3-D VSP acquisition geometry illustrates the ray paths of transmission and reflected waves

Figure2: Preliminary results from 1-D tomography applied to twenty shots from the San Juan 3-D VSP dataset. Estimated layer velocities for long offset and near offset shots are different Pattern of heterogeneity indicates need for consistent 3-D inversion.