Formation Pressure Testing During Drilling: Challenges and Benefits

Abstract

Abstract Formation pressure testers are utilized to measure formation pressure along a wellbore. From the data reservoir engineers develop information on formation fluid type, fluid contact depths, and formation connectivity. Together with recovered fluid samples, these data provide crucial exploration and development information for oil and gas fields. Until recently, pressure measurements were performed with wireline tools or during production and drill stem testing. Notably, these methods can only be used after the borehole is drilled and the drill string is pulled out of the hole. A formation test-while-drilling tool has been introduced to provide formation pressures during a brief pause in the drilling. The tool is equipped with an intelligent control system to perform closed loop, controlled drawdown-buildup tests in less than 5 minutes. Individual tests are controlled and analyzed with the FRA (Formation Rate Analysis) method in real time while repeat tests are optimized based on the previous test data. The formation pressure data can be utilized directly to choose the casing points and adjust the mud weight and ECD (Effective Circulation Density), thus allowing one to increase the drilling efficiency and safely drill into high pressured zones. As with wireline tools, the data also can be used to establish fluid gradients and fluid contacts and to analyze the connectivity between reservoirs.