Hybrid riser and method for sub-sea transportation of petroleum products with the device

A method of producing a device for transporting petroleum products in deep waters, from the sea bed up to a floating or semi-submersible surface structure, said method comprising the steps of:

• assembling a hybrid riser adapted for transporting petroleum products and an anchor,
• forming said hybrid riser as a rigid and straight unit extending vertically, and having a rigid central hollow tubular structure surrounded by syntactic material providing buoyancy for the hybrid riser and thermal insulation for the central tubular structure, a plurality of rigid pipelines being embedded in the syntactic material, in surrounding relation to said central tubular structure, for transporting said petroleum products therethrough,
• forming said anchor as a body embedded in the sea bed and connected to a bottom end of the hybrid riser,
• fixing a submerged float to a top end of the hybrid riser for exerting an upwards vertical force on the hybrid riser,
• connecting flexible pipelines to said rigid pipelines at the top end of the hybrid riser and to a floating or semi-submersible structure at the surface of the water, and
• conveying the petroleum products to the bottom of the rigid pipelines to cause the petroleum products to pass upwardly through the rigid and the flexible pipelines to said floating or semi-submersible structure.