Abstract:
An apparatus and a method for its use allow selective installation and removal of a canister such as one containing interface electronics to a mating connector on a housing, such as one containing a subsea multiphase flow meter sensor. The separately retrievable canister may contain multiphase flow meter detector electronics and is sealed, waterproof, and preferably light-weight. Installation and retrieval may be via use of an ROV and an alignment guide which acts as a guide to aid in correct positioning of the canister. The canister may be cooled by surrounding sea water and/or by insulation.

Description:
RELATION TO OTHER APPLICATIONS 
   This application claims priority through U.S. Provisional Patent Application No. 60/566,701, filed on Apr. 30, 2004. 

   FIELD OF THE INVENTION 
   This invention relates to a subsea device and more particularly to a retrievable subsea multiphase fluid flow meter wherein a method of and apparatus for engaging or disengaging a water-tight canister containing the flow meter electronics is utilized. 
   BACKGROUND OF THE INVENTION 
   Multiphase flow meters in the oil and gas industry are commonly used for topside (non-subsea) applications. Subsea non-retrievable multiphase flow meters are also common which have little or no distinguishing features from topside multiphase flow meters other than a water-proof design and/or remotely deliverable electrical and hydraulic power connections. 
   Existing subsea retrievable multiphase flow meters include complex and expensive stationary inlet and outlet sections in which the multiphase flow meter detector electronics are non-detachable. 
   Existing subsea retrievable multiphase flow meters have the disadvantage of non-detachably housing the flow meter detector electronics such that removal of the entire meter is required to service or repair it, causing significant downtime and expense. 
   Typical multiphase subsea oil and gas flows at high temperatures which detrimentally effects the multiphase flow detector electronics by reducing its mean time before failure. Existing subsea retrievable multiphase flow meters have the disadvantage of not providing an inexpensive cooler for stabilizing the multiphase flow detector electronics and thereby improving mean time before failure. 
   SUMMARY OF THE INVENTION 
   The present inventions relate to a apparatus and a method for allowing a subsea multiphase flow meter sensor housing directly attached to, but detachable from, a separately retrievable canister containing multiphase flow meter detector electronics. The retrievable canister is sealed, waterproof and may be light-weight. In one embodiment, the retrievable canister may be retrieved and installed through an alignment guide which acts as a guide to aid in correct positioning by the novel use of a remotely operated vehicle (“ROV”) without the use of a light intervention tool. A specially designed connector disposed on an exterior surface area of the removable canister provides one or more connections between the multiphase flow detector electronics disposed in the interior of the canister and the flow meter sensor housing mating connector. 
   The removable canister may be cooled by surrounding sea water, which may stabilize the temperature of the flow detector electronics and may improve equipment and component mean time before failure. In another embodiment, the removable canister is insulated and additionally cooled by the surrounding sea water which may stabilize the temperature of the flow detector electronics and may improve equipment and component mean time before failure. 
   The scope of protection is not limited by the summary of an exemplary embodiment set out above, but is only limited by the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A better understanding of the present invention can be obtained when the detailed description set forth below is reviewed in conjunction with the attached drawings depicting various embodiments of the present invention. The attached drawings are incorporated herein as if set out in full. 
       FIG. 1  is a perspective view of an embodiment of the present inventions; 
       FIG. 2  is a cutaway view of an embodiment of the present inventions; 
       FIG. 3  is a perspective view of an embodiment of the present inventions; and 
       FIG. 4  is a perspective view of an embodiment of a retrievable canister of the present inventions. 
   

   DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Referring now to  FIG. 1 , retrievable canister  30  is removably secured to multiphase flow meter  10 , which comprises flow tubular housing  20  and alignment guide  40 . Fluid flowing within multiphase flow meter  10  can be single or multiphase and be oil, water or gas, or any combination thereof, as well as any similar type of fluid or combination. 
   Flow meter housing  10  may comprise flow tubular housing  20  and alignment guide  40 . 
   Referring to  FIG. 2 , either flow tubular housing  20  or alignment guide  40  comprises flow meter sensor housing mating connector  22 . Flow meter sensor housing mating connector  22  provides for further communication with one or more devices (not shown in the figures) disposed on, near, or within flow tubular housing  20  of multiphase flow meter  10 , e.g. for transmission of power and data or control signals. 
   Retrievable canister  30 , which is preferably water-tight, comprises an exterior surface area and an interior volume. Electronics (not shown in the figures), e.g. fluid flow detector electronics, may be disposed within an interior volume of retrievable canister  30  in any of numerous conventional ways as will be familiar to those of ordinary skill in the subsea instrumentation arts. In an embodiment, retrievable canister  30  may comprise a substantially cylinder shape, e.g. having spherical or obround ends. Retrievable canister  30  comprises connector  32  adapted to provide a water-tight connection to flow meter sensor housing mating connector  22  and thus further between its interior electronics and one or more devices (not shown in the figures) disposed on, near, or within flow tubular housing  20  of multiphase flow meter  10 , e.g. for transmission of power and data or control signals. 
   Canister  30  uses a locking mechanism  33 , shown in an exemplary embodiment in  FIG. 4  as handle  34 , hub  35 , and locking pins  36  and  27 , to be secured to multiphase flow meter  10 . Locking mechanism  33  is disposed on the exterior surface area of retrievable canister  30  and may be selectively engaged or disengaged to selectively secure retrievable canister  30  to multiphase flow meter  10  to mate connector  32  with flow meter sensor housing mating connector  22 . Locking mechanism  33  may be disposed on an end of retrievable canister  30  opposite connector  32 . 
   In the exemplary embodiment illustrated in  FIG. 4 , locking mechanism  33  operates by pivotally mounting locking pins  36  and  37  to hub  35  which is rotatably mounted about a center axis and adapted to move axially in either direction upon rotary motion of handle  34 . Movement in a direction, e.g. circumferentially, forces pins  36  and  37  to extend from hub  35  and movement in the opposite direction forces pins  36  and  37  to retract. Pins  36  and  37  may align with corresponding mating receivers, e.g. receivers (not shown in the figures) in Flow meter housing  10 . Once hub  35  is rotated to a desired position, hub  35  may be locked into that position by any of numerous, equivalent methods as will be known to those of ordinary skill in these arts. One or more additional latches or locking mechanisms may be present, e.g. as mating portions of connector  32  and flow meter sensor housing mating connector  22 . 
   Referring additionally back to  FIG. 1 , alignment guide  40  maybe attached to flow tubular housing  20  or be integral with flow tubular housing  20 , i.e. multiphase flow meter  10  may be a unitary device comprising both flow tubular housing  20  and alignment guide  40 . Alignment guide  40  will typically comprise a volume greater than the volume of canister  30  and may further generally conform to the three-dimensional shape of canister  30 . 
   Alignment guide  40  may act as an aid to positioning retrievable canister  30  and its locking mechanism  33  when inserting retrievable canister  30  into, and attaching, or disconnecting and retrieving retrievable canister  30  from flow meter sensor housing  10 , including engaging connector  32  with or disengaging connector  32  from flow meter sensor housing mating connector  22 . 
   Referring additionally to  FIG. 3 , for proper alignment and orientation of retrievable canister  30  during a subsea mating operation, alignment guide  40  comprises guide funnel  42  or other a substantially conical opening to receive retrievable canister  30 . 
   Retrievable canister  30  may be locked to either stationary portion  30  or alignment guide  40 , e.g. to guide funnel  42 . Retrievable canister  30 , when locked into position, e.g. using locking mechanism  33 , forms a water-tight seal between connector  32  and flow meter sensor housing mating connector  22 . A mechanical locking mechanism (not shown in the figures) that maintains retrievable canister  30  in position after mating may be present at a second end of retrievable canister  30 . 
   In an embodiment, retrievable canister  30  comprises an exterior shell comprising a metal suitable for use subsea to protect its inner electronics from intrusion of sea water. In a preferred embodiment, the exterior shell protects the inner electronics from intrusion of sea water at depths up to at least 3000 meters. Internally, retrievable canister  30  may have an environment comprising a predetermined pressure maintained with an inert gas such as Nitrogen, e.g. around one atmosphere. 
   In an embodiment, retrievable canister  30  is insulated from its external environment which may improve equipment and component mean time before failure. 
   In the operation of exemplary embodiments, a method of mating a retrievable canister  30  to stationary section  20  of multiphase flow meter  10  is accomplished by using a remotely operated vehicle (“ROV”) subsea (not shown in the figures). In this method, retrievable canister  30  is positioned by an ROV into alignment guide  40 . A 90 degree turn may be required by the ROV to engage the locking mechanism. 
   The remote engagement or disengagement of the water-tight canister locking mechanism may be accomplished by using a light intervention tool or by using a ROV to position retrievable canister  30  into alignment guide  40 . The ROV then guides retrievable canister  30  to a position wherein connector  32  is proximate mating connector  22 . Once positioned, locking mechanism  33  is engaged by the ROV to secure retrievable canister  30  to stationary portion  20  of flow tubular housing  10 . 
   To retrieve retrievable canister  30 , locking mechanism  33  is disengaged by the ROV to unsecure retrievable canister  30  from stationary portion  20  of flow tubular housing  10  and retrievable canister  30  retrieved from stationary portion  20  of flow tubular housing  10  by the ROV. 
   Typically, engaging locking mechanism  33  further engages connector  32  to mating connector  22  to establish communications between electronics disposed within retrievable canister  30  and one or more predetermined devices external to retrievable canister  30  this manner, a device disposed outside retrievable canister  30 , e.g. a fluid flow detector (not shown in the figures) disposed within or proximate flow tubular  10 , is operatively connected to electronics disposed within retrievable canister  30 , e.g. a flow meter. This allows communication between these devices and receives data transmitted by sensors from the flow meter sensor housing mating connector after the locking mechanism is engaged. The data transmission, and, hence, the connection, may be electronic, fiber optic, acoustic, or the like, or a combination thereof. The fluid flow detector is self-contained and may utilize a self-contained power unit, a central processing unit to calculate the fluid flow from the transmission of data received from the flow meter sensor housing mating connector, or the like, or a combination thereof. The central processing unit may use a computer software flow algorithm to calculate the fluid flow. The fluid flow detector may also allow for the local or remote transmission or recording of the calculated fluid flow. 
   The foregoing disclosure and description of the invention are illustrative and exemplary thereof, and various changes in the size, shape and materials, as well as in the details of the illustrated construction, may be made without departing from the spirit of the invention.