Wells – Submerged well – Connection or disconnection of submerged members remotely...
Patent
1998-04-17
2000-04-25
Taylor, Dennis L.
Wells
Submerged well
Connection or disconnection of submerged members remotely...
166338, 166368, E21B 712
Patent
active
060532521
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to well intervention systems. In particular, the invention relates to intervention systems for use on sub-sea wells.
At the present time, the number of well intervention operations on sub-sea wells is relatively few. However, interventions on platform based wells have contributed to considerable increases in production. Therefore, if the cost of sub-sea interventions is reduced there will be a considerable saving to industry.
DESCRIPTION OF THE RELEVANT PRIOR ART
An area which has a major cost implication in both capital and running costs is the system for monitoring pressure control during intervention on a sub-sea well. In the drilling mode this equipment comprises a blow out preventer (BOP) stack, a disconnectable lower marine riser package and a marine riser system. For well intervention through the sub-sea xmas tree a different pressure control system is used, comprising a safety package to contain the well, a disconnectable riser package and a dual workover riser system. These require complex and expensive handling and running system which occupies a large space on board the vessels which may cause problems with regard to storage of other equipment. If a cost effective and economic alternative to a traditional rigged-based BOP system or industry standard workover riser systems can be derived, then this would offer significant advantages.
Accordingly, several major operators are currently reviewing the feasibility of conducting well intervention operations from lightweight semi-submersible and mono-hull DP vessels for the purposes of well surveillance and management. Cost evaluations of this type of intervention indicate that saving of at least 40-50% are achievable compared with utilising a semi-submersible. If such a vessel could be used it would offer significant advantages in flexibility and speed of manoeuvre to different locations and could also be used for additional uses such as well testing or coiled tubing drilling.
Two existing through-BOP stack intervention systems have recently been disclosed; one in applicant's co-pending U.K. Application No. 9509547.7 for a 5".times.2" dual bore completion tree, and the other in U.K. 9505129.8 for a 5" and 7" monobore system for horizontal/spool trees. These BOP stack intervention systems enable completion/intervention operations to be conducted prior to a conventional tree being deployed or, in the case of a horizontal tree, during the completion and intervention phase. Both systems bring considerable advantages to the operator. Such systems are beginning to be deployed in the industry.
Dual bore skeletal workover risers are used in two roles. Firstly, within the marine riser to run and retrieve the well completion tree and, secondly, to deploy the xmas tree and intervention equipment in open water. In both cases the equipment provides the well control functions required in a well intervention role.
With the marine riser, the through riser equipment is not subjected to open water environmental loads and, consequently, does not have to offer the structural integrity to resist the bending and tensile forces experienced in an open water environment but the equipment does provide the well control functions required in a well intervention role.
It is desirable to create a system which offers all the functions of both a through-BOP and open water system but provide a lightweight intervention role, that is one without a BOP stack, which was hitherto not available or possible with existing systems.
SUMMARY OF THE INVENTION
This is achieved by providing a lightweight intervention system for use with single bore and dual bore intervention operations and which can be used with both horizontal trees and conventional trees and with wellheads without trees mounted thereon. The system is based on a two-part intervention apparatus; the lower part provides the pressure control and consists of a xmas tree or wellhead connector and structural housing in which a sub-sea test tree is located and is coupled to the
REFERENCES:
patent: 4691780 (1987-09-01), Galle et al.
patent: 4721163 (1988-01-01), Davis
patent: 4749046 (1988-06-01), Gano
patent: 5372199 (1994-12-01), Cegielski et al.
patent: 5941310 (1999-08-01), Cunningham et al.
Expro North Sea Limited
Taylor Dennis L.
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