The Norwegian operator Norsk Hydro has more than 80 flexible dynamic risers and service lines in operation at different platforms. Riser integrity monitoring programs have been established for the flexible risers in order to ensure safe and reliable operation. SeaFlex has performed annulus testing on a large number of these risers as a part of the programs. The free annulus volume of a flexible pipe is defined as the volume between the extruded internal pressure barrier layer and the extruded external sheath subtracted the volume occupied by pressure- and tension armor, tape and eventual other layers. Two methods are presently used by the industry for annulus free volume testing of flexible pipes, namely nitrogen pressure testing and vacuum testing. Both methods identify trends of volume reduction with time and to detect annulus flooding. Annulus testing has proven to be an efficient and reliable tool for detecting annulus flooding, blocked vent ports and outer sheet damages. This paper address the challenges related to annulus testing of flexible pipes, advantages, experiences and how such tests and the results are used for condition assessment and monitoring of the risers.
The deep-water (700 m) Gimboa field in offshore Angola was discovered in 2004. With approximately 50 million barrels of recoverable oil in place, this project is marginal at best. The development required accurate resources determination, cost effective implementation, and maximum recovery of the reserves. This is also the first deep water development by Sonangol Pesquisa & Produção, the National Oil Company of Angola, as Operator.The short-term project (approximately 4 years from discovery to production) was loaded with uncertainties and risks. Among the technical challenges were performing the conversion of an oil trading tanker to an FPSO, the manufacturing and deployment of subsea production facilities as a tie-back to the FPSO, and the solution of issues related to low reservoir pressure, gas lift, water injection and insulation.In order to tackle these difficulties and quickly build expertise, the Operator formed a technical assistance agreement with one of the concession partners. Engineers, geoscientists, and managers from both companies worked together, as one colocated team with shared objectives. Effective communication using the web and management were key factors to ensure that the project team and the globally distributed team of vendors could focus on the work at hand. After successfully meeting all the challenges, the field is scheduled to enter into production at the start of 2009.An equally important result of the Gimboa development was the self-realization by a relatively young national oil company that they could manage and develop complex projects in difficult environments. This project also demonstrates that regional and global organizations can equally benefit from the introduction of innovative and more open partnership models.The paper summarizes the Gimboa experience, and describes how national oil companies, with the appropriate focus and technical assistance, can successfully and quickly develop their marginal discoveries, making the most of the available fiscal incentives, using national resources, and promoting local content.
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