Pore Pressure Uncertainty, Practices and Pragmatism for Well Planning

Abstract

During the last decade, markets have imposed significant operational cost savings to the oil industry. With a given annual upstream budget and commonly overestimated exploratory well AFEs, some projects can be compromised or postponed. Defining with more accuracy the exploration wells AFE can allow to drill an extra well on the same annual budget. Pore Pressure and Geomechanical studies directly drive the well design (including contingencies), the drilling strategy, the rig selection or the equipment necessary to achieve the given objectives safely. The cost of the well is directly impacted, therefore, by these inputs. Optimising and lowering the PPFG uncertainties are key factors to reduce the allocated budget and final cost of a well. Reducing the uncertainty too much, however, can result in a well design not sufficient to handle the conditions with disastrous consequences. To solve this complex equation, the engineer needs to understand how all the sources of uncertainty are propagated. From the well Kick Off meeting to the final PPFG delivery to drilling team, every single step includes uncertainties: geological / prospect definition, offset well analysis and lessons learnt, seismic velocity, overpressure mechanisms and scenarios, fluid type, depth uncertainties, lithology effects amongst others.