A Possibility of Active Controlled Installation for Deep Water Subsea Production Modules

The water depth of the offshore oil/gas development becomes deeper, and in some field like offshore Brazil pre-salt, the target water depth is generally more than 2000m. Although there are several new technologies to be developed for the pre-salt deep water field, a new method how to install a SPS module effectively and precisely is one of the most desired challenges. In this paper, I will present a possibility of using active control technique for deep water installation using a crane vessel. The SPS module structure consists of a pendulum system whose arm length is becoming longer as the hanged structure is going down to the sea bed. An initial offset angle from the vertical axis will cause a vibration motion whose horizontal amplitude develops according to time during installation. Two dimensional equation of motion is derived and several simulation results will be shown for the cases of both free hanging situation and actively controlled situation. The control algorithm is LQR and a ROV is assumed attached to the structure as an actuator to suppress the vibratory motion to install the structure on the desired target point on the sea bed.