The objective of this study is to develop an image analysis scheme for the control of riser end, which is important for the riser connection with the seabed wellhead in offshore oil drilling and production. In the scheme, a single camera is used to get the image of the targets, an approach of 3D position recognition is used to get the 3D coordinate of targets from the images, and thereby the displacement of targets between different images can be obtained. In the study, the static and dynamic experiments on the image analysis scheme were carried out. This scheme can be applied to the re-entry operation of riser end, and its preliminary experiment was carried out.
Riser technology is widely used in offshore oil drilling and production (Brink, et al, 1981; Koterayama, et al, 2005). Drilling riser pipe is held on a vessel, floating with ocean wave. Considering that it is made of rigid material, thin and long, easy to be damaged, it should be disconnected from the seabed wellhead when the sea condition becomes bad. After the sea condition turns better, the riser end may need to be connected with the seabed wellhead again. To accomplish the connection, the riser end (in this paper, riser end means riser lower end, and riser top means riser upper end) should be surveyed by a position recognition system, and moved by the riser controller. Generally speaking, cameras installed on the ROV are used to observe the riser end, an operator guesses its distance between the riser end and the sea bottom wellhead connector from the image, and then moves the riser end empirically, but it's not an easy task and sometimes takes too much time. Also many kinds of displacement sensors can detect the distance between targets (Suzuki, ea al, 1993; Machado, et al, 1999), but they may need many additional devices and cause much inconvenience in the deep sea.
