Patent Application
20080202761
The invention relates to a method of controlling temporarily installed equipment such as Subsea Intervention trees and Retainer Valves using Tubing Hanger access. The method is comprised of the following components:
(1) Subsea Test/Intervention Tree and Retainer Valve: This equipment is utilized as a temporary part of a completion running string, deployed into wells from offshore floating or anchored vessels. Located within the vessels BOP stack and directly above the production trees Tubing Hanger and Tubing Hanger Running tool. This equipment provides a well isolation and unlatch function as well as hydrocarbon retention allowing the vessel to safely move off location in emergencies. These valves are hydraulically actuated and traditionally rely on application and venting of hydraulic pressures supplied from either an ‘In riser’ control system and/or an umbilical terminated at the uppermost face of each valve. This umbilical is strapped or clamped to the tubing or casing string and sits within the inside diameter of the Drilling/Marine riser, as such a high level of risk exists that movement between these elements due to sea or ocean currents can cause damage to that umbilical. From the uppermost face of the assembly where the umbilical or conduit is terminated, internal porting through the assembly will carry the control fluids or electrical conduits to the various functions within the Retainer Valve, Subsea Intervention Tree, Tubing Hanger Running Tool, Tubing Hanger and ultimately devices within the Completion string. This requirement for a large number of connections and intricate porting within the aforementioned devices particularly the Retainer Valve, Subsea Intervention Tree and Tubing Hanger; this creates multiple potential for leak paths or loss of electrical continuity for each conduit.
(2) Tubing Hanger Running tool: The Tubing Hanger Running tool is located directly below the Subsea Intervention tree and provides a facility to latch and unlatch the upper landing string from the Tubing hanger. This allows the temporary landing string to be removed leaving the production completion installed and locked. The Tubing hanger running tool can be mechanically or hydraulically actuated. Hydraulically actuated Tubing Hanger Running tools receive control pressure via conduits fed through from the Subsea Intervention valve assembly and also provides conduits for controlling the Tubing hanger and devices within the Completion string. These conduits represent multiple potential leak paths for each conduit.
(3) Tubing Hanger: The Tubing hanger forms the uppermost part of the permanent completion and facilitates the locking of the Completion into the production tree. The Tubing Hanger is traditionally hydraulically operated; the Tubing Hanger receives control pressure from surface via the conduits passed through the Tubing Hanger Running Tool, the Subsea Intervention valve, the Retainer Valve and the ‘In riser’ umbilical. It can be seen that this supply represents a torturous path with a multitude of potential leak paths. The interface between the Tubing hanger and the Production tree contains a series of stabs; these stabs facilitate the hydraulic or electrical communication between the production tree and Tubing hanger. Control pressures or electrical conduits are received from the production tree and then passed from the stabs down the completion string via a series of small-bore tubing or electrical conduits to control the various devices that make up the completion string.
(4) Production Tree: The Production Tree is a valve manifold that directs well effluent to the production facility via a side port. The production tree also acts as a control center for the completion itself; distributing hydraulic or electrical signals to the various down hole completion devices, which monitor, control or inject chemicals into the well. These controls are fed to the production Tree via a production umbilical and Junction or ‘J’ plate, which is deployed open water, from the production facility or the drilling vessel, depending on the phase of operation. Once connected to the production tree the controls are routed through the body and into the Tubing Hanger as described above via sets of stabs.
(5) Control System: The Control system is made up of a power unit comprising a pump and accumulators combined with hydraulic valves and regulators configured to control hydraulic pressures feeding various hydraulically operated devices. A control system can also regulate and supply electrical power to feed various electrically driven devices. A control system will also generally include the means of delivering the hydraulics or electrical power, i.e. an umbilical which is made up of hydraulic control lines or a combination of hydraulic control lines and electrical conduits thereof.
During completion running/pulling or workover operations Control elements (i.e fluids and/or electrical) are transferred from a floating offshore installation via a single or series of conduits to a junction plate. This junction plate is removable and attached to the Production tree (Generally, but not restricted to a Horizontal or spool type trees).
This junction plate locks the conduit/umbilical to the production tree and facilitates communication to a series of hydraulic ports/electrical conduits within the production tree wall. These ports will link to a set of stabs/receptacles located within or around the inner wall of the production tree and are isolated until such time as the mating tubing hanger is landed within its bore. The tubing hanger is deployed from the rig floor (Surface), through the bore of the Marine riser, into the BOP stack and landed on a location within the inner bore of the production tree. Typically a completion string will be attached to the lower end of the tubing hanger and a running tool c/w Landing string and well isolation devices (Typically, but not restricted to a Subsea Test/Intervention Tree and Retainer Valve) attached to the upper end.
The action of landing the Tubing hanger within the production tree will establish communication between the aforementioned stabs/receptacles and the Tubing hanger. Alternatively these stabs/receptacles may be energized to engage using external forces. These established communications provide monitoring or control to equipment located within the completion part or lower part of the inner assembly.
While the present invention has been described in terms of specific embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. The invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein: rather, these embodiments are provided by way of illustration only and so that this disclosure will be thorough, complete and will fully convey the full scope of the invention to those skilled in the art. Indeed, many modifications and other embodiments of the invention will come to mind to those skilled in the art to which the invention pertains, and which are intended to be, and are covered by this disclosure, the drawings and the claims.
