A Digital Twin for Computing Dynamic Watch Circles on a Dynamically Positioned MODU

Abstract

Abstract A digital twin representing the drilling system of a dynamically positioned (DP) mobile offshore drilling unit (MODU) has been developed and deployed in offshore Brazil. The primary output of the digital twin is a set of dynamic watch circles which are generated based off the predicted drift-off behavior of the MODU under real-time environmental conditions. The watch circles, together with vessel and weather status information, are displayed to the crew on board and updated on an hourly basis. This paper describes the development of the software platform on which the digital twin is built, together with the underlying drilling system model and solution parameters, which uniquely include the effect of the marine riser restoring force. Integration with external data streams is presented, including vessel position and heading, riser tension, and environmental data (wind, wave, and current). The system outputs, including the local user interface on the vessel and the output data stream to the operator’s real-time data center via the WITSML protocol, are also described. The digital twin with dynamic watch circle output has been successfully utilized on a campaign of shallow-water wells for plug-and-abandonment (P&A) operations in concert with BOP tethering and subsea realtime monitoring systems. Together, these systems ensured safe operations and wellhead protection in a challenging environment for dynamically positioned MODUs. Additionally, the operator was able to gather correlated data streams monitoring the weather conditions, vessel status, dynamic watch circle estimation, subsea drilling system status, and tether loads. The digital twin and dynamic watch circle system enables drilling and completion operations to be performed under conditions judged to be untenable when evaluated via traditional operability analysis methods involving statistically predicted environmental conditions.