The greatest risk to operational safety during the drilling and completion of a well is a kick. A gas influx, with its potential for escalation into well control event, places the crew, the environment and the rig in imminent danger.
The second greatest risk is misdiagnosis of an event and the failure to quickly and correctly take action.
For kicks and other pressure related events, the question is often fundamental—"are we experiencing losses or is the well ballooning during a connection"? The answer can be critical. An incorrect decision based on a misdiagnosed situation can result in millions of dollars in non-productive time (NPT). In the extreme, incorrect diagnosis can lead to death and injury, environmental damage and the loss of the rig.
These risks to well control and drilling efficiency are being mitigated using a handful of common oilfield technologies that are the key elements of closed-loop circulating system—rotating control devices (RCDs), flow-metering technologies, automated drilling choke systems and downhole isolation valves.
This is truly an instance of the whole being greater than the sum of the parts. That value is being further enhanced through the integration of innovative analysis and management software. These closed loop systems have proven very successful in mitigating risk and improving economics across a wide range of land and marine drilling applications and are allowing the industry to safely tackle it’s most risk-laden and costly wells.
The elements are field proven—some with more than a 40-year history—readily available from numerous vendors and are relatively economical. Individually they add incremental safety and efficiency benefits. However, when these elements are paired or used in combination with each other to create a closed and pressurizable mud-returns system, the benefits escalate at an exponential rate.
This paper examines the basics elements of a closed-loop circulating system and how this technology is enhancing the safety and efficiency of drilling and completion operations without sacrificing other operational elements.