PZPS Event Matching and Simultaneous Inversion - A Critical Input to 3D Mechanical Earth Modeling

A 3D Mechanical Earth Model (3D MEM) of a field was built integrating geophysical, geological, and petrophysical data. The 3D MEM represented the close-to-initial field property conditions, and is an ideal basis for analyzing wellbore and formation stability, subsidence and compaction, and cap-rock and fault sealing during initial and depleted field conditions. The lateral resolution of the elastic rock properties input for the 3D MEM was obtained using a PZPS simultaneous inversion of OBC data. Simultaneous inversion of PZ and PS data required adequate alignment of the two datasets. PZ and PS data were aligned by an automated event registration where major events were aligned in an iterative process refining the matching result with each iteration step. The use of PZ and PS data in the simultaneous inversion showed superior density results compared to inversion with PZ-data only. In addition, the acoustic impedance and Vp/Vs ratio inversion results were improved showing a high degree of lateral continuity, and a better match with the wellbore log data. The final high resolution inversion results provided a well-constrained data basis for the subsequent distribution of geomechanical properties throughout the 3D Mechanical Earth Model.