Patent Application
20120292034
The field of the invention relates to side pocket mandrels and more particularly those used in gas lift operations and configured to provide double barrier protection between the tubing and the surrounding annular space.
Gas lift is a technique where fluid is injected into the string to aid the produced fluids to get to the surface. One way this is done is with side pocket mandrels. Side pocket mandrels are tubular structures fitted into a string at predetermined locations and include an internal side compartment where a valve can be installed without reduction of the string drift dimension. The side pocket has a wall opening and the valve is used to control the rate of fluid that can be injected into the string at the location of each of the side pocket mandrels that are in service for a particular string.
Some designs have tandem valves with separate check valves so that one can be taken out of service without opening communication between the tubing and the casing. Such a design is shown in U.S. Pat. No. 7,228,909 and in model SBRO-DVX side pocket mandrel sold by Weatherford International Ltd. of Houston, Tex. These tandem gas lift valve designs in a side pocket mandrel were built to address issues of capacity or pressure drop in operation and to provide workover capability of removing one of the valve assemblies in a workover and going back in service with a backup. In essence the dual gas lift design of the past ran the gas lift valves in parallel to increase gas injection flow and/or reduce pressure drop across such valves. Check valves associated with each pocket kept tubing pressure in the tubing to protect the surrounding casing from overpressure if the valves are removed from the pockets.
These designs fail to address requirements in many jurisdictions for dual barriers for any wall opening in a tubular string and the surrounding annular space regardless of whether that annular space is open to a formation being produced or is isolated from it with a packer. The present invention offers this capability and a compact design with the possibility of retrofitting of existing side pocket mandrel designs that have two or more locations for inserting valves. An alternative for single valve side pocket mandrels is to run two close to each other and provide control line connection of the valves for capability of running the valves in series. Preferably the passages in the side pocket mandrel can be internally configured to conduct flow in parallel to meet the double barrier requirements of many jurisdictions for isolation of tubular wall openings. Those skilled in the art can get a better understanding of the invention from a review of the description of the preferred embodiment and the associated drawings with an understanding that the full scope of the invention is to be determined by the appended claims.
A side pocket mandrel has openings to receive a plurality of valves such that the flow of fluid from outside the string and into the tubular such as in gas lift will flow through the valves in series. The side pocket mandrel that has a single valve pocket can also be used in tandem with another similar side pocket mandrel to get the same dual barrier configuration to meet requirements of many jurisdictions of such a valve arrangement for tubular wall openings.
The side pocket mandrel 10 has at least two pockets 100 and 110 that are interconnected through passage 120 that is preferably between them. Flow enters from the surrounding annular space 12 into inlet 14 seen in
It should be noted that there is a plug 26 that isolates passage 120 from interior passage 18. Passages 100 and 110 are preferably smooth walled to act as seal bores for the valves latched at profiles 16 and 22. While the side pocket mandrel 10 that is illustrated in
Retrofitting existing side pocket mandrels with two pockets for series rather than parallel flow is envisioned assuming the size in question leaves room in the wall to add another pocket that serves the function comparable to passage 120 and with transverse passages added so that the newly added pocket can communicate the adjacent pockets with the newly added pocket in a series path from one existing pocket to the next.
Each pocket such as 100 and 110 can have a check valve associate with it or in an adjacent transverse passage that prevents flow into the annulus if the pockets are left empty from a removal of a valve for maintenance or any other reason.
While the preferred embodiment connects the two valves in series through an intermediate passage 120 the use of such a passage is optional and a transverse passage can go between the pockets 110 and 100 directly depending on the size of the housing and the angular separation between the pockets. The transverse passages such as 20 and 150 can be drilled from the housing exterior and then closed with a threaded plug or the equivalent.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below:
