Abstract: Diclosed is a connecting assembly for communicating between a first location and a second location lower than the first location, with the two locations separated by a fluid body. A first tube extending between the two locations generally encloses a second tube, and the annular area between adjacent surfaces of the two tubes is sealed toward the second location. The buoyancy of the assembly is selectively controlled by selectively controlling the quantity and density of fluid in the area between the tubes. In an embodiment shown, a marine drilling facility is joined to an underwater well site by a riser with a liner set and sealed therein, and gas-lift pumping is used in controlling buoyancy. In a method, a riser is set between an underwater well site and a marine well operating facility. A first segment of the well may be drilled through the riser. Casing is cemented in the well, and a liner is sealed at its bottom end to the riser.

Abstract: Disclosed is a connecting assembly for communicating between a first location and a second location lower than the first location, with the two locations separated by a fluid body. A first tube extending between the two locations generally encloses a second tube, and the annular area between adjacent surfaces of the two tubes is sealed toward the second location. The buoyancy of the assembly is selectively controlled by selectively controlling the quantity and density of fluid in the area between the tubes. In an embodiment shown, a marine drilling facility is joined to an underwater well site by a riser with a liner set and sealed therein, and gas-lift pumping is used in controlling buoyancy. In the method, a riser is set between an underwater well site and a marine well operating facility. A first segment of the well may be drilled through the riser. Casing is cemented in the well, and a liner is sealed at its bottom end to the riser.