Abstract: An emergency release tool for operation by a remotely operated vehicle (ROV) for forcefully releasing a riser from a subsea well assembly The tool includes hydraulic cylinders mounted on a frame that can be positioned by the remotely operated vehicle to surround the risers. The cylinders are pressurized to forcefully remove the riser from the wellhead assembly.

Abstract: A concentric riser parallel bore subsea well assembly for controlling production from a subsea wellhead to a floating production facility. The invention utilizes a concentric riser and tubing string in combination with a dual parallel bore production tree. The production tree communicates with a parallel bore tubing hanger that communicates with the production tubing string and the casing annulus.

Abstract: An anchor system for temporarily anchoring the lower end of a lower marine riser package (LMRP) assembly, drilling riser, and drill string used in drilling subsea wells. The anchor system includes a dummy wellhead secured to the ocean floor and weight means stored in a dummy wellhead that can be connected to the end of the drill string in a manner that restrains the lateral movement of the LMRP assembly, drilling riser, and drill string.

Abstract: A protective cover for protecting a wellhead mandrel and related equipment of a subsea wellhead when the drilling and producing equipment is removed. The protective cover is installed and removed using a pipe or cable running string with provisions for using either a hydraulic jet, a Remotely Operated Vehicle (ROV) or surface rig movements to position the cover.

Abstract: A well tubing hanger designed for severe service applications includes an annular seal formed about the tubing hanger exterior that is not energized during normal well operations. The annular seal is energized by lowering the tubing hanger downward within the tubing head until the annular seal subsequently contacts in a fluid-tight manner both the tubing hanger and the tubing head. The tubing hanger is lowered relative to the tubing head by rotative disengagement of a treaded mandrel operatively connected between the tubing hanger and the tubing head. The annular seal is energized prior to installation or removal of well flow control equipment located above the tubing hanger and tubing head, preferably after well fluid flow through the well has been secured.

Abstract: A selective injection of gaseous fluid into a portion of a subterranean reservoir is improved by positioning an impedance to fluid flow in the annulus between a pipe string and a surrounding permeable-walled conduit, ensuring the presence of granular solids between the permeable-walled conduit and the reservoir, injecting the gaseous fluid through the pipe string to a point below the impedance and injecting fluid which is more viscous than the gaseous fluid down the annulus to restrict bypassing of the impedance.