Pressure-while-drilling data improve reservoir drilling performance

A new downhole annular pressure-while-drilling (PWD) tool has been applied recently to assist in drilling the reservoir section on the Statfjord field, offshore Norway. For drilling success in these high-angle wells it is critical to maintain the mud weight and equivalent circulating density (ECD) within safe operating limits defined by the formation fluid, collapse, and fracture pressures. Operating outside these limits historically has led to expensive lost circulation, differential sticking, and packoff incidents. Monitoring the actual downhole pressure in real time with a PWD tool, rather than relying on inferred pressures from predictive models, has allowed the operator to stay within and to better define these operating limits. The operator used this improved hydraulics information to avoid pressure-related hole problems, to optimize drilling practices, to test hydraulics models, and to obtain a greater understanding of the formation pressure limits.