This paper discusses the preliminary underwater testing of the ROV tooling and work packages developed for Norsk Hydro's Oseberg field. Final shallow water integration testing using the actual subsea equipment was originally scheduled to take place in Dec. '87 or Jan. '88 but was delayed. Since all of the ROV tooling and interface work was complete at that time, it was decided to construct an underwater test fixture and carry out separate underwater testing of these items to prove their performance in an actual operational situation. This was done to ensure that the solution of any problems found during testing could be easily accomplished prior to mobilizing the equipment for the offshore installation phase. The tests were carried out at Oceaneering's facility in Stavanger, Norway in Nov. '87. This paper discusses these tests, their results and the conclusions reached about the tooling designs. In addition, a brief review of the ROV tasks, subsea equipment design, and intervention work package designs is given at the beginning of the paper to provide needed continuity to the test discussion.
Remote work system intervention for the Oseberg Subsea Systems consists of the following major work tasks:
Transponder replacement
VX/HX gasket replacement
Cable/rope cutting
Guidewire/guidepost installation and replacement
Visual monitoring of connector latch/unlatch
X-mas tree valve operations and overrides
Connector overrides
Pig launching
Cleanup and removal of drill cuttings and cement returns
Flowline pull-in intervention
As shown in Figure 1, the wellheads, themselves are protected from fishing activities by an overtrawable monolithic concrete gravity structure. It has an octagonal shape that provides four inclined slabs for protection and four opposite openings for access to the X-mas tree and control pod assembly. The tasks that the remote work system is required to perform range from simple tasks such as guidewire cutting and replacement, to more complex tasks such as an override and operation of the X-mas tree and the production guide base (PGB) valves. Because the protective structure is installed prior to drilling operations, drill cuttings, mud, and cement returns must be removed from the inside before the production equipment is installed. Due to the operational procedures during final completion, some of this cleaning must be done by the remote work system. Also, although final X-mas tree installation and attachment of the flowlines and control umbilical will be done by divers, the remote work system will supply auxiliary hydraulic power to the pulling tools during pulling operations.
Some of the ROV tasks listed above do not require any specialized tooling. However, tasks such as manual valve overrides, hydraulic overrides and clean-up of drill cuttings and mud required the development of the following remote work packages:
Hydraulic override tool
Hydraulic override panels
Manual valve override/actuation tool
Manual valve interface panels
Hydraulic power skid
Dredging/jetting skid
