2.9-D Crosswell Traveltime Tomography

The acquisition geometry of the multiple surveys at the second phase of the. McElroy project provided the opportunity of reconstructing a 3-D slowness model from crosswell data only. This led us to the implementation of traveltime inversion algorithm for 3-D slowness reconstruction. The model is parameterized by the slowness values at nodes on a prismatic mesh. A slowness field is estimated from the joint inversion of arrival times from multiple crosswell surveys. The algorithm is applied to the post CO2 injection tomographic surveys of the McElroy project and to produce a time-Iapsed tomogram from the surveys taken before and after injection. The time-lapsed tomogram presents an anomaly at the reservoir region unambiguously related to the injection process.