Interference analysis and operability envelopes design for deepwater parallel strings

Dual derrick operations are widely used for field development during offshore drilling. During this process, complex operations and complicated hydrodynamic interaction may contribute to the interference collisions of parallel strings. In this context, this study addresses interference collisions for parallel strings during the deepwater dual derrick operation. To analyze the response of parallel strings a mechanical model for deepwater parallel strings is established. Moreover, Huse wake model and strip model are used for calculating the hydrodynamic influence in different wake fields. The research results validate that the collision will occur during the operation considering the hydrodynamic wake shielding effects and interference evaluation criterion. The increasing platform offsets and surface current are the leading causes of parallel strings collisions. To avoid the risk of interference collisions an innovative procedure for operability envelopes is developed by synthesizing the platform offsets and surface currents. The proposed operability envelopes method for parallel strings is automatically completed which can save much workforce and resources. A case study on deepwater drilling in the South China Sea has been applied to verify the effectiveness of these methods. Besides, the proposed methodology can effectively reduce collision accidents and provide technical support for the offshore oil and gas exploration.