Subsea drilling operations

Details Subsea drilling operations Subsea drilling operations

1999-09-14

2002-07-23

Bagnell, David (Department: 3672)

Wells

Submerged well

Connection or disconnection of submerged members remotely...

C166S340000, C166S341000, C175S007000, C405S191000

Reexamination Certificate

active

06422315

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to subsea drilling operations and, in certain particular embodiments, to retrieval systems and operations for retrieving pod containers from a subsea lower marine riser package platform.
2. Description of Related Art
In subsea drilling operations as shown in
FIGS. 3 and 4
, one or more subsea pod containers BP, YP are located on a lower marine riser package (“LMRP”) LM platform encompassing a riser RS through which drilling operations are conducted. These “pods” contain electronics and valves that are used in the monitoring and control of a wide variety of functions related to drilling operations. Typically the pods are releasably connected to an LMRP which is the top portion of a structure or “stack” ST that includes blowout preventers (“BOP”) and related apparatus used for well control.
The prior art discloses redundant systems which employ two similar pods so that if there is a failure in one “on line” pod, e.g. a failure of electronics or of a valve, the other “standby” pod can be brought to an “on line” status, e.g. by a Driller, to immediately perform the required actions or functions. The retrieval of a pod for replacement or for repair is a complex and expensive operation. To retrieve an LMRP with a failed pod requires removal of the riser to which the LMRP is connected. The riser extends from the drill floor, e.g. from a boat or rig at the water's surface, down to the stack. “Tripping” out the riser is a long expensive process, and LMRP retrieval requires such a “trip.”
Many prior art deep water multiplexed BOP Control Systems include two identical systems either of which may control Stack functions. One such system is illustrated schematically in FIG.
1
. This configuration is commonly referred to as being “Dually Redundant”. Both systems may be active electronically and may have single or dually redundant sets of electronic controls. One of the systems including one of the pods is active hydraulically. The system that is active hydraulically is manually selected by a Driller to be the active system or “Active Pod”. Each system, or Pod, is equipped with an hydraulic conduit supply. This supply is run from an Hydraulic Pressure Unit (HPU) HP on the surface to the Pod that is mounted on the LMRP. A “Crossover Valve” may be actuated. This actuation diverts hydraulic fluid from the Pod it is designed to supply to the redundant Pod normally supplied by the other conduit. This “Crossover” function allows either Pod to be supplied by either conduit. This is a Driller actuated, manual function and pod redundancy is lost during retrieval.
Also mounted on the LMRP are Hydraulic Accumulators HA. These Accumulators supply hydraulic fluid for the Stack functions at a consistent pressure so that a function is actuated according to the manufacturer's specifications. Each Pod's Hydraulic supply conduit HS
1
, HS
2
, resepctively, is connected to the Hydraulic Accumulator's Hydraulic Manifold HM so, that the conduit which has been selected as the active Hydraulic supply line may “charge” the Hydraulic Accumulators. Check valves CV prohibit the hydraulic fluid from backing-up the un-used, or not active, Hydraulic supply conduit. Thus, whichever conduit is selected as the active hydraulic supply will “charge” the LMRP mounted Accumulators. API requirements as well as normal “Oil-Field tradition” classify one of the hydraulic supply conduits as the Blue supply. The other hydraulic supply conduit is classified as the Yellow supply. The Pod traditionally associated with the Blue supply is classified as the Blue Electro/Hydraulic (E/H) Pod, or Blue Pod. Conversely, the other Pod is traditionally classified as the Yellow Pod (e.g. as shown in FIG.
2
). The prior art system of
FIGS. 1
,
2
functions as do the same parts that are in the system of
FIG. 19
, but without the triple redundancy of the system of FIG.
19
.
A typical prior art Blowout Preventer (BOP) Control System regulates a well during drilling operations and continuously monitors the status of such operations. The BOP system includes a structure that incorporates hydraulically actuated well control safety devices and their peripheral components, i.e. blowout preventer system. Such apparatus is referred to as the Blow Out Preventer Stack or simply as the “Stack”. The upper portion of the “Stack” is referred to as the Lower Marine Riser Package (LMRP). The LMRP includes a platform and is the interface between the Riser system and the “Stack”. It is a separate structure and is supplied with, or as a part of, the “Stack”. The LMRP is connected to the “Stack” via a hydraulically actuated “Stack” connector. It is connected to the Riser by a “RISER” connector. Between these two connections there may be inserted “BAG” BOP's “Pipe” BOP's (Pipe Rams), and/or other instrumentation or controlled protective and supplementary equipment. This LMRP “platform” also physically supports hydraulic accumulators and the BOP Control System Subsea Electro-Hydraulic (E/H) “PODS”. These subsea “E/H Pods” perform the well control regulation tasks as supervised by the Driller from the Drill Floor of the Rig. The Driller may regulate a parameter, i.e. a hydraulic pressure subsea on the LMRP or “STACK”, or control a function, i.e. close a pipe ram BOP, and/or monitor the real time actuation of the function controlled or the parameter regulated.
Many of the BOP Control System's end functions are on the lower portion of the “STACK”, i.e. below the LMRP “STACK” Connector. A command from the Driller is transmitted serially via fiber optics or cable, onto a “data freeway”. The electronic I/O equipment located in the Subsea E/H Pod retrieves data and instructions from, and writes status to, the data freeway. These instructions (commands) are performed with electronic I/O equipment that interfaces with electro/hydraulic functions, i.e. electrical solenoid valves. These solenoid valves either hydraulically actuate LMRP functions directly, or pilot larger valves i.e., sub plate mounted (SPM) valves. These SPM valves supply hydraulic fluid at greater volummes or flow rates than could be accomplished with the solenoid valves themselves.
These SPM valves supply hydraulic fluid to hydraulic connectors, or stab plates, which allow LMRP accumulator hydraulic fluid flow to the “Stack” mounted functions below. The LMRP Accumulators are supplied via multiple sources from the surface Hydraulic Pressure Unit (HPU). The LMRP Accumulators are “float” charged by the Driller selected surface hydraulic source, i.e. one of the multiple sources. This fluid, in route to a Stack mounted function, migrates through the solenoid valve, to the SPM valve piloted actuator, through the SPM valve supply ports, through the hydraulic connector, through a series of shuttle and check valves, and then on to actuate the desired Stack mounted, piston-like, function. These Stack mounted functions are referred to as a “Stack function”. The series of shuttle and check valves encountered by the hydraulic flow is necessary to enable redundancy of control. There is an E/H Pod associated with each of the surface hydraulic supplies.
As stated above for redundancy, “Oil Field” tradition dictates that one hydraulic source be associated with one E/H Pod. This Pod will be designated as the “Blue Pod”. Another hydraulic source will be associated with another E/H Pod and this combination should be labeled the “Yellow Pod”. Each one of these pods are identical, and contain identical components, i.e. the electronic I/O, the solenoid valves, the SPM valves, and the hydraulic stab plate (LMRP side). Each hydraulic stab plate, “Stack-side”, is connected by hydraulic tubing to the shuttle/check valve tubing and so terminated at the end function (Not Redundant). Only one pod is hydraulically active at a time. The other pod is considered a hot back up and may be electrically active and functioning. The electronic I/O (Input/Output) and the solenoid valves portion of the E/H Pod are referred to a

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