Recoil control of deepwater drilling riser system based on optimal control theory

Recoil of deepwater drilling riser system is a problem to be solved in offshore oil and gas engineering. Previous study focuses on the recoil analysis of deepwater drilling riser system rather on its recoil control. A recoil control method is proposed based on optimal control theory in this paper. A coupling recoil model of deepwater drilling riser system is established based on tensioner model, riser dynamic model and mud discharge model. Taking the displacement and velocity of each equivalent mass of the riser system as state variables, state-space equations for riser recoil control are then derived based on the established riser recoil model. The riser recoil controller is finally designed based on optimal control theory and linear quadratic regulator (LQR) control algorithm. Riser recoil response with controller and without controller is analyzed and compared with each other. The results show that the riser recoil response with controller is obviously less than that without controller. The designed riser recoil controller can control the riser recoil response effectively, which can decrease the recoil operation risk of the riser system. •A coupling riser recoil model is established for riser recoil analysis.•State-space equations are derived based on the coupling riser recoil model.•A riser recoil controller is designed based on optimal control theory.•The designed riser recoil controller can control riser recoil response effectively.