Device and method for maintaining and guiding a riser, and method for transferring a riser onto a floating support

A method of transferring a riser on a floating support of the type having a central cavity from a production position of the riser to a position within a drilling derrick by using an apparatus which includes guide means enabling said riser to slide along its longitudinal axis ZZ′ and guiding lateral displacements thereof in a horizontal plane XX′, YY′ perpendicular to said longitudinal axis of the riser, the apparatus comprising joint means secured to said floating support which enables said riser to (a) rotate about a horizontal axis XX′, YY′ perpendicular to the longitudinal axis ZZ′ of said riser within the limit of a cone having a half-angle at the apex that is less than or equal to 10°, said horizontal axis and said apex of the cone being situated substantially at the center of the riser and level with the midplane of the zone along the longitudinal axis ZZ′ where said joint means are situated, and (b) slide along the longitudinal axis ZZ′ and to be guided in its lateral displacements in a plane XX′, YY′ substantially perpendicular to said longitudinal axis of the riser, the joint means comprising first friction pads mounted on a pad support enabling said pads to pivot about respective axes perpendicular to said longitudinal axis of said riser ZZ′, the first friction pads cooperating with one of wheels and second friction pads such that said one of said wheels and said second friction pads bear against said riser, and enable said riser to slide, said method being characterized in that said riser is displaced in said cavity of a floating support by displacing said apparatus relative to the floating support, said apparatus itself being secured to said riser.