f Rock Physics Model Inversion for Pore Pressure Prediction in Clastic Reservoirs

Pore pressure prediction is a safety and well control issue. In hydrostatic context, Shale velocity increases with burial, allowing defining a “Normal” Compaction Trend (NCT). Any deviations from this trend can be attributed to stress and pore pressure variations… - However, this fails if mineralogy or porosity happen to change (cementation, organic matter, smectite, sandstones, carbonates, etc.). It such situations, the pressure estimation has to take onboard basin analogs, regional knowledge, reservoir size and connection to aquifer, etc. which makes it highly interpretative. - We will present a new approach predicting Pore Pressure in both shale and clastic reservoirs. - Using rock physics templates and rock physics models (RPM) allows tailoring specific NCT for each type of rock (mineral fractions, porosity, in-situ fluids…): for a given silico-clastic rock (not only shale) saturated with a given fluid at a given burial, a “reference” hydrostatic velocity is calculated. Any difference with observed velocity can lead to pore pressure estimation in reservoirs. - RPM inversions give encouraging results at Log scale, as well as in 3D, at seismic scale; and both in pre-drill context and real-time update.