The term “PPFG (Pore Pressure Frac Gradient)” has been used by oil and gas people since late 1950s, several years before the born of “Geomechanics”, to address the anomalous subsurface pore pressure and the corresponding fracture gradient. PPFG specialists use several empirical approaches to not only predict the pore pressure, but also estimate the fracture gradient to provide drillers with a safe mud weight window. Geomechanics specialists, however, utilize the science of rock mechanics to predict drilling risks and improve drilling performance by providing optimum mud and well designs. Unlike PPFG, geomechanics estimates the in-situ stresses, and consequently the safe drilling mud weight window, based on the mechanical properties of the rock formations. As the result, the mud weight window developed based on a geomechanical model is dependant on both rock mechanical properties and well trajectory, which is a requirement to differenciate wellbore stability conditions in vertical, deviated and horizontal wells.
The traditional PPFG approaches are associated with significant risks because of the low depth resolution and the fact that they are not base on scientific facts. Despite the advances in petroleum geomechanics in the last decades, PPFG models are still widely used in the oil and gas industry.
This presentation discusses seven major mistakes associated with the PPFG models, while the science of gemechanics can address these caveats and help developing wellbore stability models that are more reliable and provide valuable information for optimum mud, casing and well design.
Dr Hamed Soroush is an internationally recognized geomechanics expert with extensive experience in different applications of rock mechanics in the energy industry. He has conducted or managed more than 250 consulting and research projects worldwide. Dr Soroush is currently the CEO of PETROLERN LLC providing strategic planning, technical leadership, support and training for geomechanics and subsurface engineering applications. Prior to that, he held various positions with companies such as Dong Energy, Shell, Weatherford, Senergy, CSIRO, and Geomechanics International in different locations around the world. He is principal investigator for several US Department of Energy research projects.
Hamed holds a BSc in Mining Engineering, an MSc in Rock Mechanics and a PhD in Petroleum Engineering from Curtin University of Technology in Australia. He has given numerous industry short courses and has served as SPE Distinguished Lecturer for 2012 – 2013 and 2017 – 2018 programs.