Wells – Submerged well – Connection or disconnection of submerged members remotely...
Reexamination Certificate
1997-11-12
2001-02-06
Dang, Hoang (Department: 3672)
Wells
Submerged well
Connection or disconnection of submerged members remotely...
C166S347000, C166S366000
Reexamination Certificate
active
06182761
ABSTRACT:
SPECIFICATION
1. Field of the Invention
This invention relates to an apparatus and method for extending offshore hydrocarbon flowlines and, more particularly, to extending hydrocarbon flowlines from a template/manifold system at a first subsea well site to a second well site using a flowline pigging assembly.
2. Description of the Prior Art
In the 1970's, the petroleum industry began to produce hydrocarbons from offshore subsea wells. Over the past three decades, many different configurations of subsea production system components have been generated to help develop these offshore hydrocarbon reserves. Depending upon the number of wells required by a given production plan, the system configurations range from a single satellite subsea well producing to a host platform, to large multi-well subsea template/manifold systems producing to a host platform or a large floating production unit.
In subsea template/manifold systems, wells are drilled from one single structure, and hydrocarbons are collected in a single manifold attached to the template for delivery to a production platform or other surface production unit. Various forms of templates have been used to integrate production of various subsea producing wells into a single area and to more easily collect the production in a single manifold. The main advantage of the template/manifold systems is the reduction in the number of remote interface connections between the wells and the manifold.
More recently, subsea clustered configurations have come into use, featuring a central manifold surrounded by a number of subsea satellite wells. See, for example, U.S. Pat. Nos. 4,848,475 and 5,025,865.
Where marginal fields are located in deep water, operators will often choose to initially place only a few subsea wells in specific locations to evaluate producability before installing a high cost production facility. Further, operators may wish to incrementally add wells such that the reservoir and production data from each successive well may be used to better assess the risk of subsequent development efforts. Accordingly, a method of extending subsea flowlines from an initial template to later drilled wells at a second template site would be desirable if it could minimize the investment required in the initial installation to accommodate such future expansion.
Whichever type of subsea production system is used, a need exists to provide a method to clean the hydrocarbon flowlines. In hydrocarbon production it is common to remove deposits or debris from flowlines by pumping a “pig” through the flowline. The pig scrapes or dislodges deposits from the interior of the flowlines, and those deposits are carried out of the flowlines by the same fluids that propel the pig. Pigging is used as part of an overall corrosion control program to remove deposits and sweep out water that may collect in the low spots of flowlines. Pigging may also be used to displace resident fluids in the flowlines as may be required by operational procedures. As hardware associated with pigging is a necessary part of the initial investment required with installation of the subsea system and associated flowlines, it would be desirable to use this pigging hardware also for future expansion of the subsea flowlines.
SUMMARY OF THE INVENTION
The present invention is a pigging valve assembly for a template/manifold system that provides a flow path between multiple subsea flowlines to circulate pigs through the flowlines for cleaning and which can be modified to provide connections for extending flowlines to later developed wells that are remote from the initial template/manifold. The present invention also provides a method of extending flowlines using a pigging valve assembly.
The assembly of the present invention provides a flow path between subsea flowlines that terminate at subsea template/manifold systems. A curved or “U” shaped piping section of the assembly connects various production headers that are in turn connected to flowlines. The curved piping section is bent at a radius sufficient to allow a pig to pass. The assembly also includes pigging valves located between the curved section and the production headers to isolate individual flowlines or allow flow and pig passage.
In its simplest form, the invention connects two subsea flowlines. When the flowlines need to be cleaned, the pigging valve on the subsea termination point of each flowline is opened. A pig is launched from a surface end of one flowline. The pig flows down the flowline, through the subsea manifold, and passes the open pigging valve. The pig then turns in the curved piping section, flows through the open pigging valve on the second flowline, and returns to the surface through the second flowline where it can be retrieved.
The present invention also allows flowlines to be extended with minimal impact on the template/manifold system. Extension is made by first retrieving the pigging valve assembly to the surface and removing the curved piping section. Flowline connector adaptors and a porch support module are added to the assembly replacing the curved piping section. Flowline connector adaptors are connected on one end to pigging valves while the opposite end provides a connection point for extending the flowline. The flowline connector adaptor is curved such that it will allow a pig to pass through it and into a new flowline. The modified pigging valve assembly with the porch support module is lowered onto the subsea template/manifold. A new section of flowline can be attached to the flowline connector adaptor to extend the original flowline to a second template/manifold at the new well site.
REFERENCES:
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patent: 5842816 (1998-12-01), Cunningham
Dang Hoang
ExxonMobil Upstream Research Company
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