Abstract: A recoil system and method for supporting a marined riser which is extended from offshore well head equipment to a floating platform are disclosed. The purpose of the recoil system is to prevent a violent collision of the riser with the platform when the riser becomes separated from the well head equipment during a planned or an emergency disconnect operation. Upon disconnection of the riser from the well head equipment, the lifting force applied to the riser is reduced to a predetermined lower level and the riser is retracted to an elevated position above the well head equipment to permit unobstructed excursions of the riser. A variable lifting force is applied to the riser to maintain the riser substantially in equilibrium in the retracted position as the floating platform heaves relative to the riser in response to wave action.

Abstract: A recoil system and method for supporting a marine riser which is extended from offshore well head equipment to a floating platform are disclosed. The purpose of the recoil system is to prevent a violent collisin of the riser with the platform when the riser becomes separated from the well head equipment during a planned or an emergency disconnect operation. Upon disconnection of the riser from the well head equipment, the lifting force applied to the riser is reduced to a predetermined lower level and the riser is retracted to an elevated position above the well head equipment to permit unobstructed excursions of the riser. A variable lifting force is applied to the riser to maintain the riser substantially in equilibrium in the retracted position as the floating platform heaves relative to the riser in response to wave action.

Abstract: Method and apparatus for controlling down hole pressure during an offshore drilling operation is disclosed. The method and apparatus are particularly useful for drilling in deep water from an offshore surface facility which includes a drilling vessel stationed above an ocean floor drilling site in which well head equipment is embedded. A marine riser is connected to the well head equipment and extends to the drilling vessel. A drill string enclosed within the riser extends from the drilling vessel through the well head equipment and into a borehole beneath the ocean floor. Choke and kill conduit lines are connected in fluid communication with the borehole and extend from the well head equipment to the drilling vessel. According to the invention, a subsea choke valve is connected in fluid communication with the choke conduit line and with the interior of the riser whereby fluid or gas may be discharged at a controlled rate from the choke line directly into the riser annulus.

Abstract: Pipe connectors particularly useful in securing sections of an underwater marine riser together, including a pin received in a box and bearing against a box shoulder, the pin and box being secured together by coengaging members mounted on the box, and between the pin and box, and forced against a shoulder at the outer portion of the pin over substantially 360.degree. of the shoulder, to correspondingly force the outer end of the pin against the box shoulder, with the contacting pin and box surfaces axially preloaded against each other. The coengaging members can include a plurality of lock dogs mounted in the box and movable radially inwardly against a ring device disposed between the box and pin and engaging the shoulder at the outer portion of the pin, the dogs and pin device having coengaging cam surfaces causing dogs to exert an axial thrust on the ring device which is transmitted from the ring device to the pin shoulder.