Abstract: A dual riser assembly for use with an offshore multi-activity drilling assembly to conduct drilling operations from a deck above the surface of a body of water into the bed of the body of water utilizing two risers, a first and a second, which extend from a location above the surface of a body of water to a common location adjacent to the bed of the body of water. Each riser terminates, at a distal end, into a dual riser assembly, allowing for selective open internal communication between each of the two risers and a single wellhole.

Abstract: A dynamically positioned, concentric riser, drilling system comprising a dynamically positioned drilling unit operable to float at least partially above the surface of a body of water, a first, outer, low-pressure, marine riser extending from the drilling unit into the body of water, a tensioning system to support the first marine riser, a second, inner, high-pressure, marine riser concentrically extending within the first, outer, low-pressure, marine riser, a surface blowout preventor, a lower marine riser package, a subsea blowout preventor, and a connector at the base of the lower marine riser package to release the risers from the wellhead in the event of a loss of station of the drilling unit.