Origin of Abnormal Pressures, Hydrodynamism and Pore Pressure Prediction

Abstract

SUMMARYCurrent Frontier exploration is bringing us to drill into increasingly highly pressured sedimentary intervals as well as hydrodynamic flows. In these Frontier contexts, lack of well calibrations & poor understanding of the pressure generating mechanisms lead to ever increasing uncertainties in our pore pressure prognoses. Total's experience of all mechanisms of abnormal pressures shows that our in-house shale pressure modeling is quite accurate and reliable with conformity rates between the prognoses and results close to 100%. By taking a step back, it has been noticed that the greatest uncertainty lies within the reservoir pressures and that these are 100% linked to the understanding (or lack of) of the 3D geological model. All recent cases where the pressure results are significantly different from the prognosis are always linked to errors on the geological model used to estimate the reservoir pressures. Thankfully, Total's philosophy for pre-drill pore pressure prognoses, follow-up while drilling and postmortem analysis has allowed us to reach 100% of exploration objectives while keeping the highest safety standards & not put our operations at risk in case of non-compliance to the PPP modeling. We are putting great efforts to maintain this track record and striving to refine our methodologies.