Modular backup fluid supply system

This application claims priority to provisional application No. 60/705,538.

The invention relates generally to a fluid supply system and apparatus and, more particularly, to a modular backup hydraulic fluid supply system and apparatus.

Subsea drilling operations may experience a blow out, which is an uncontrolled flow of formation fluids into the drilling well. Blow outs are dangerous and costly. Blow outs can cause loss of life, pollution, damage to drilling equipment, and loss of well production. To prevent blowouts, blowout prevention (BOP) equipment is required. BOP equipment typically includes a series of functions capable of safely isolating and controlling the formation pressures and fluids at the drilling site. BOP functions include opening and closing hydraulically operated pipe rams, annular seals, shear rams designed to cut the pipe, a series of remote operated valves to allow controlled flow of drilling fluids, and well re-entry equipment. In addition, process and condition monitoring devices complete the BOP system. The drilling industry refers to the BOP system in total as the BOP Stack.

The well and BOP connect to the surface drilling vessel through a marine riser pipe, which carries formation fluids (e.g., oil, etc.) to the surface and circulates drilling fluids. The marine riser pipe connects to the BOP through the Lower Marine Riser Package (“LMRP”), which contains a device to connect to the BOP, an annular seal for well control, and flow control devices to supply hydraulic fluids for the operation of the BOP. The LMRP and the BOP are commonly referred to collectively as simply the BOP. Many BOP functions are hydraulically controlled, with piping attached to the riser supplying hydraulic fluids and other well control fluids. Typically, a central control unit allows an operator to monitor and control the BOP functions from the surface. The central control unit includes hydraulic control systems for controlling the various BOP functions, each of which has various flow control components upstream of it. An operator on the surface vessel typically operates the flow control components and the BOP functions via an electronic multiplex control system.

Certain drilling or environmental situations require an operator to disconnect the LMRP from the BOP and retrieve the riser and LMRP to the surface vessel. The BOP functions must contain the well when a LMRP is disconnected so that formation fluids do not escape into the environment. To increase the likelihood that a well will be contained in an upset or disconnect condition, companies typically include redundant systems designed to prevent loss of control if one control component fails. Usually, companies provide redundancy by installing two separate independent central control units to double all critical control units. The industry refers to the two central control units as a blue pod and a yellow pod. Only one pod is used at a time, with the other providing backup.

While the industry designed early versions of the pods to be retrievable in the event of component failure, later versions have increased in size and cannot be efficiently retrieved. Further, while prior art systems have dual redundancy, this redundancy is often only safety redundancy but not operational redundancy, meaning that a single component failure will require stopping drilling operations, making the well safe, and replacing the failed component. Stopping drilling to replace components often represents a major out of service period and significant revenue loss for drilling contractors and operators.

The industry needs a simple and cost effective method to provide added redundancy and prevent unplanned stack retrievals. The industry needs an easily retrievable system that allows continued safe operation during component down time and integrates easily and quickly into existing well control systems. The industry needs a simpler, economic, and effective method of controlling subsea well control equipment.

In some embodiments, the present invention provides an improved method and apparatus to provide redundancy to fluid flow components via alternative flow routes. In some embodiments, the present invention allows for safe and efficient bypass of faulty components while allowing continued flow to functions or destinations. The present invention can be integrated into various existing flow systems or placed on entirely new flow systems to provide a layer of efficient redundancy. In other embodiments, the present invention relates to a stand alone control system for subsea blow out prevention (BOP) control functions. The present invention is particularly useful for hydraulically operated control systems and functions in water depths of 10,000 feet or more.

In some embodiments, a fluid supply apparatus comprises a primary fluid flow route that includes one or more primary flow control components, an intervention shuttle valve, and a destination and a secondary fluid flow route that bypasses the primary flow control components, and includes a modular removable block of one or more secondary flow control components, the intervention shuttle valve, a selectively removable hose that connects the modular removable block of secondary flow control components to the intervention shuttle valve, and the destination. A remotely operated vehicle (ROV) may deploy selectable hydraulic supply to a BOP function that has lost conventional control. In some embodiments, the intervention shuttle valve has an outlet that is hard piped to a BOP function and a secondary inlet that is hard piped from a receiver plate.

In some embodiments, the modular valve block is removable and includes a directional control valve. More directional control valves may be placed on modular valve block, with the number of directional control valves corresponding to the number of BOP functions that it may simultaneously serve. Modular valve block is generally retrievable by an ROV, thus making repair and exchange easy. Further, the modular nature of the valve block means that a replacement valve block may be stored and deployed when an existing valve block requires maintenance or service. Many other components may be placed on the modular valve block, including pilot valves, and pressure regulators accumulators. Pilot valves may be hydraulic pilots or solenoid operated.

In some embodiments, the modular valve block connects to the BOP stack via pressure balanced stab connections, and in embodiments requiring electrical connection, via electrical wet-make connection. In some embodiments, the modular valve block mounts onto a modular block receiver that is fixably attached to BOP stack. Preferably, the modular block receiver is universal so that many different modular valve blocks can connect to it. In some embodiments, either the modular valve block or the modular block receiver is connected to a temporary connector for receiving a hose to connect the modular valve block to an intervention shuttle valve.

In some embodiments, the intervention shuttle valve comprises a housing having a generally cylindrical cavity, a primary inlet entering the side of the housing, a secondary inlet entering an end of the housing, a spool-type shuttle having a detent means, and an outlet exiting a side of the housing. In some embodiments, the outlet is hard piped to a destination, and the primary inlet is hard piped a primary fluid source. During normal flow, the shuttle is in the normal flow position and fluid enters the primary inlet and flows around the shuttle stem and out of the outlet. The shuttle design seals fluid from traveling into other areas. When backup flow is introduced into secondary inlet, the fluid forces the shuttle to the actuated position, isolating the primary inlet and allowing flow only from the secondary inlet.

In some embodiments a compound intervention shuttle valve comprises two intervention shuttle valves whose outlets are attached to the inlets of a gate shuttle valve. Thus, the compound intervention shuttle valve comprises two primary inlets, two secondary inlets, and an outlet. The gate shuttle valve is similar to the intervention shuttle valve in that it has a shuttle that shifts to allow flow from one inlet and to isolate flow from the other inlet, but generally has a different shuttle design.

In some embodiments, a BOP hydraulic control system includes a blue central control pod, a yellow central control pod, and at least one modular valve block associated with each pod to provide universal backup for all control pod components. The modular valve blocks have an outlet that attaches to a hose via a temporary connection, and the other end of the hose attaches to any one of a number of intervention shuttle valves, each associated with a BOP function. Thus, each modular valve block provides redundancy for at least one BOP function.

In another embodiment, the invention comprises a stand alone subsea control system, modular in construction and providing retrievable, local, and independent control of a plurality of hydraulic components commonly employed on subsea BOP systems. Such a system eliminates the need for separate control pods. Other embodiments allow independent ROV intervention using an emergency hydraulic line routed from the surface to an ISV in the case of catastrophic system control failure of all BOP functions.

Independent and/or redundant control over BOP functions reduces downtime and increases safety. Furthermore, a control system having easily retrievable components allows fast and easy maintenance and replacement. The present invention, in some embodiments is compatible with a multitude of established systems and provides inexpensive redundancy for BOP system components. In another embodiment of the invention, control over the modular block valves is transparently integrated into an existing multiplex control system, allowing an operator to control the modular valve block using the existing control system.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.