Patent ID: 7189029

Claim:
An undersea pipe of the riser type providing a connection between a floating support and the sea bottom, said riser being constituted by a rigid pipe of the catenary type suspended in the water subjected to gravity and extending between the surface and the sea bed, with a portion of the riser resting substantially horizontally on the sea bed, the curvature of the riser in suspension is such that the curvature radius of the riser decreases from the surface wherein the curvature radius has a maximum value, down to the point of contact of the riser with the sea bed where the curvature radius has a minimum value, the pipe being characterized in that said catenary riser comprises at least two pipe portions corresponding to two different catenary curves, one of said portions being a lower pipe portion terminating at said point of contact, the apparent weight per unit length in water of said lower pipe portion being at least 25% less than that of the remainder of said pipe constituting said catenary riser.