Abstract
Conventional well control procedures rely merely on the pit gain and variations in pump pressure as the primary indicators to detect and handle the influx. These indicators are rudimentary and unreliable for drilling costly offshore wells while advanced well control techniques demand more reliable indicators for early detection of gas kicks. Having access to continuous pressure data along the wellbore, offered by intelligent (wired) drillpipes, can be very helpful in detecting and handling gas kicks.
This paper proposes a technique for early gas detection during conventional drilling by utilizing the intelligent drill pipe. For this purpose, different flow regions in the annulus are identified and modeled based on the conservation equations. A numerical scheme and transient gas kick simulator are developed to solve the equations. Sensitivity analysis is conducted for various parameters such as influx sizes, mud flow rates and wellbore geometry.
The results indicate that when gas influx enters the wellbore, pressure at all sensors increases simultaneously. This criterion can be used for early detection of gas kicks; In addition, when top of gas influx passes a certain sensor, pressure curve at that sensor declines. This fingerprint can be utilized in determining the location of the gas kick. This can be done even more precisely when pressure derivative curves are plotted to determine the time that a gas influx reaches a certain sensor.
Using intelligent drill pipes in modern well control operations can reduce kick detection time to less than half, which results in significant reduction in non-productive time and enhancements in safety. The developed simulator provides a powerful tool that can contribute to well control practices and real-time decision making.
