Wells – Submerged well – Testing
Patent
1998-08-26
2000-11-28
Lillis, Eileen D.
Wells
Submerged well
Testing
166368, E21B 33035, E21B 4706
Patent
active
061522309
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to well safety and, in particular, to safety of perforated and suspended wells in which are installed tubing hangers fitted with wireline plugs, but which do not have a xmas tree fitted.
At the end of the drilling phase of a production well, a tubing hanger may be run into the well, while the BOP stack and marine riser are still connected. The tubing hanger is landed, locked and then pressure tested. Downhole work may then occur to clean the well up and a brief well test may then be conducted. At the end of this phase the well is made safe prior to the disconnection and retrieval of the BOP stack and marine riser, to await the installation of a subsea xmas tree on some occasion in the future. The well is made safe by the installation of mechanical plugs with elastomeric seals deployed into the well using wireline techniques.
Within the production bore a primary barrier is established by the installation of a deep set plug in the downhole completion, at or below the packer assembly. A secondary barrier is established by the installation of a second similar plug within a suitable profile in the tubing hanger production bore. On the annulus side, the primary barrier is the downhole packer assembly and a secondary barrier is established by the installation of a similar wireline set plug in a separate profile of the annulus bore within the tubing hanger. Thus, the statutory requirement to provide two barriers between the reservoir and the environment are satisfied.
However, to date, the authority responsible for safety in the British sector of the North Sea, for the time being, the Health & Safety Executive (HSE), requires there to be a drilling facility on hand in the locality for the duration that a live well is suspended in this manner with a dual bore tubing hanger. The reason for this is that wireline set plugs have a poor record of reliability with the potential for such plugs to leak. Maintaining the presence of a drilling facility in the locality of such a suspended well enables the rig to stop its current activity and return to the suspended well with leaking plugs, re-run a BOP stack and perform the work necessary to stop the leakage. It will be appreciated that for field developments where such a drilling facility is on hand during the development of the field, no problem exists, the rig is in the area drilling other wells while previously drilled wells are suspended in this manner.
However, for small field developments, this requirement limits the opportunities to suspend wells in such a manner. It may not be possible to ensure the availability of a rig in close proximity to the suspended well for the period in which the well would be suspended, and it would not be cost effective to maintain a dedicated rig available in the locale until such time as subsea xmas trees are installed onto the suspended wells.
An object of the present invention is to obviate the requirement for a rig to be on hand in locales where there are suspended drilled wells.
A further object of the invention is to provide a barrier which can be coupled to the well to prevent leakage such that a drilling vessel is not required and which barrier can be easily removed to accommodate the installation of a subsea xmas tree.
This is achieved by providing an additional high security barrier installed onto the wellhead for containing any leakage safely and which permits the installation of a subsea xmas tree onto the wellhead whilst, simultaneously, providing means for containing full pressure control during rectification of the leak. The barrier includes means for monitoring the pressure between the upper surface of the tubing hanger and the underside of the barrier and, in addition, in the event the presence of well bore fluids is detected indicating that leakage has occurred, the barrier includes means to allow intervention in order to rectify the leakage.
According to a first aspect of the present invention there is provided a wellhead security system comprising, tubing hanger assembly suspended therein,
REFERENCES:
patent: 3800869 (1974-04-01), Herd et al.
patent: 4691781 (1987-09-01), Gano
patent: 4887672 (1989-12-01), Hynes
patent: 5280766 (1994-01-01), Mohn
patent: 5366017 (1994-11-01), Voss, Jr.
patent: 5372199 (1994-12-01), Cegielski et al.
Edwards Jeffrey Charles
Morgan Michael Graham
Expro North Sea Limited
Lagman Frederick L.
Lillis Eileen D.
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