Offshore Brazil, the wet completion is a common alternative. That requires heavy equipments (say 300 tons) to be installed on the bottom of the sea. Due to deep water discoveries this task has become more and more complicated. This deep water and also the weight of the equipment it is likely to lead to resonant conditions with the wave excitation and several casualties have been observed.
Very expensive installation vessels with heave compensation may be used. However, even is one can pay for this services, they are not easily available leading to prohibited delays.
To face this situation recently Petrobras developed a method (the Pendulous Installation Method - PIM) that does not require specialty vessels but two simpler ones. The device is hold by one vessel and a cable is connected to the other such that as the equipment is launched a trajectory that resembles a pendulum is followed up to the sea bottom. In fact the oscillation does not really occur since as it has been proven that almost supercritical behavior prevails.
Before the method was considered safe and reliable, several model tests concomitant with numerical models have been performed as discussed in the present work. Aspects like fluttering, tumbling of the device were observed and, later on, avoided.
Even more recently, further a simplification has been searched with the goal of deploying the equipment from the deck of one of the vessels. This would allow much easier installations with more commonly available vessels reaching a fortunate less expensive, fast and safe situation.
This paper synthesizes a method for model testing of non-conventional devices and operations to the development Pendulous Installation Method (PIM).
Specifically, the PIM does not require boats with compensation systems for the usual vertical launching. The device to be installed is released from the free surface. It is hold by an auxiliary cable from a boat and connected by the installation cable to another boat some distance away. The auxiliary cable is then released and after an almost vertical trajectory of the manifold, the installation cable traction increases and the device rotates (pendulous motion) about the turning point on the other support boat.
During the development of novel systems or operations, the industry is learning the importance of model testing. During the model tests, it has been understood that a two-scale problem had to be faced by the model test design. There are large bodies (the device) together with slender bodies (cables) in the same hydrodynamic situation. These two bodies have different scaling laws. How cope with it depends on the several aspects (inertia, damping, etc). However, with the help of a modern numerical model computer code, these problems may be anticipated by creating a framework of results that help in the interpretation of the model testing result itself.