Determination of Dynamic Limits for Rig Heave and Running Speed Based on Drilling Parameters, Well Data and Completion Tool Limitations - Case Studies

SummaryA novel method of utilizing simulations of surge and swab induced by floating rig heave is presented in this paper. The intended applications are in well planning and follow-up of drilling and completion operations. We focus on rig heave during drill pipe connections when the rig's heave compensator cannot be engaged. The method consists of: (1) estimating a dynamic, well- and operation-specific, rig heave limit based on surge & swab simulations at different depths in a well and (2) clearly communicating the dynamic rig heave limit to the rig crew and onshore organization as a simple metric. We present cases where this novel methodology has been tested during the drilling and completion of two offshore wells in Norway, and we elaborate on the operators’ view of the method's advantages. We conclude that complementing the traditional fixed rig-specific heave limit with the dynamic one that is based on the properties of the actual well and the actual drilling/completion parameters offers an opportunity to improve management of risks related to breaching well pressure margins or damaging downhole equipment and to reduce costs through reduction of weather-related non-productive time. We show that the dynamic rig heave limit may differ significantly from well to well and also throughout the same well depending on the kind of operation in the well, depth in the well, well geometry and other parameters related to well and operation properties. Our conclusion is that care should be taken when generalizing a maximum allowed rig heave value as is the industry practice today. The benefits of utilizing dynamic well-specific rig heave limit should be assessed during well planning for any well drilled and completed from a floating rig. Well planning software existing today does not offer this functionality.