Pore Pressure Prediction in HP/HT environment

Abstract

The necessity to satisfy the world need for oil & gas pushes oil companies to drill in conditions that are getting harder and harder in terms of Temperature and Pressure. The drillers have to know the conditions as precisely as possible before drilling a new borehole. Generally, in complex and deep areas the more traditional relationships linking interval velocities from seismic time processing with the effective stress (and consequently the pore/over pressure), are no longer enough to make a correct prediction of the pore pressure. For this reason several methods have been developed to try to obtain more appropriate velocity fields, and in this paper we compare some of them, mainly CVA (Continuous Velocity Analysis) in the time domain and Grid Tomography, in the depth domain. We intend also to show pressure prediction results that, instead of being obtained directly from velocities, are derived from different seismic attributes. In particular we present some pressure predictions obtained by seismic inversion products such as Ip (Impedence of wave P) and Vp/Vs Ratio. The paper shows some results from a prospect where the deep targets present very difficult drilling conditions in terms of High Pressure and High Temperature.