Wells drilled with nitrified drilling fluids require a solution for the transmission of measurement-while-drilling (MWD) surveys, bi-directional communication with rotary steerable systems, and transmission of MWD and and logging-while-drilling (LWD) measurements of downhole temperature and annular pressure for surface choke adjustments. Wired drillpipe (WDP) provides the solution for these requirements. Results from a recent well drilled into an underpressured reservoir in southern Mexico provided an opportunity to demonstrate the applicability of WDP to deliver the required measurements and maintain the proper directional control while keeping the well fluids under control. During WDP operations, both the traditional mud pulse transmission and the new WDP transmission methods are available, providing 100% reliability for receiving the downhole MWD/LWD data.

During the drilling of this well, both single and multi-phase Managed Pressure Drilling (MPD) techniques were used. The plan called for the overburden and reservoir sections to be drilled in one bit run but with different mud types and constant bottom-hole pressure (BHP). Before drilling the reservoir section, the single-phase mud used to drill the overburden had to be changed-over to multi-phase mud while monitoring the wellbore for signs of instability. Maintaining constant BHP in this type of MPD operation is complicated by the fact that current hydraulic models do not have the proven capability to support constant BHP in a nitrified OBM.

With mud pulse telemetry, downhole data transmission stops when the rig pumps are shut-down. But with WDP, downhole data is actively transmitted during the time between pump shut-down and pipe disconnection. This allows MPD personnel to monitor actual annular pressure during pump transitions and more accurately determine the optimum choke position for constant BHP. During the connection, the downhole annular pressure is stored in memory. Once the connection has been made the data is transmitted up-hole for evaluation and analysis, which provides immediate feedback on the stability of the BHP during the connection.

Pressure sensors (along string measurements or ASM) within the multiple WDP repeater subs allow us to compute the fluid density at multiple intervals along the annulus for the first time in the history of drilling. We document a rather surprising case of temperature effects overriding pressure effects during the use of a single-phase compressible OBM used in the first stage of this drilling operation. This has implications for using WDP measurements to calibrate and verify hydraulic models for both single and multi-phase drilling fluids. Proper hydraulic modeling capabilities are critical for MPD operations.

This well provides the opportunity to demonstrate other applications for these newly invented “interval fluid densities.” For example, they are used to verify the top of the fluid level with and without the presence of nitrogen injection when accurate flow-in versus flow-out measurements are not available. This is used to verify the presence or absence of lost circulation and formation fluid influx during MPD operations, which is very difficult otherwise.

WDP allows for the transmission of high-frequency vibration and collar rotation data from the bottomhole assembly (BHA). This is used to determine the dynamic rotational tendencies of this drillstring under varying conditions, which can then be used to calibrate a dynamic mathematical drillstring model. This is then used to predict optimum drilling parameters to minimize stick/slip, bit bounce, and bit whirl to optimize rate of penetration (ROP).