RIASSUNTO
During drilling operations, one of the primary concerns for a driller is to keep the pipe moving to avoid getting stuck. Often this philosophy creates a conflict with the evaluation services group, whose tools require time on station to collect key data. In particular, formation pressures and sampling require time on station to reach steady state pressures or obtain a relatively clean sample. Many believe that the risk of getting stuck increases linearly with the time drillpipe is stationary. This relationship between time on station and the probability of getting stuck has been ingrained into many of today’s drilling practices, yet it is not supported by the data from many wells. There are several instances where drillpipe remains stationary for tens of hours or even days. This can be a result of a catastrophic failure of the top drive system or need to acquire critical formation data through formation sampling. If time were the critical factor in sticking the bottom hole assembly (BHA), then this practice would surely result in stuck pipe; yet in many cases the drillstring moves freely. Today, there is a growing movement in the drilling community to prove that time on station is not in fact linear but is based on time, t, raised to the power of .. The first few moments without pipe movement are the most critical. In a properly maintained hole, this would mean that additional time on station for formation testing is not as problematic as other factors such as overbalance, wellbore complexity, inclination, and hole size. This paper will investigate the relationship between time on station and the probability of losing a BHA. Worldwide industry data will be used to investigate the causes of lost BHAs and the technology available today that can decrease the risk of sticking a BHA.