The present paper deals with the subject of failure of deep-sea pipelines that have thickness metal-loss areas caused by corrosion and are subjected to high external hydrostatic pressure. An extensive research program was launched to observe failure modes, to examine existing and to develop prediction collapse equations, and to determine their accuracy. The program uses finite element modeling and external hydrostatic collapse tests of full-scale specimens. This paper presents and discusses the results of the first 20 collapse tests, which were performed in a new 103 MPa (15 ksi) hyperbaric chamber (760 mm internal diameter and 7200 mm length). The test results obtained with full scale specimens (324 mm external diameter and 23 mm thickness) made of low carbon steel API 5L X60 with external machined metal loss defects are used to verify the level of accuracy and conservatism of four analytical simple equations used to predict collapse of pipes with corrosion subjected to high external pressure.
Nowadays, the global trend is an increasing need for oil and gas. As the easily recoverable fields have been already developed, the trend in the offshore oil and gas industry is going deeper into the more challenging outlook, such as outside West Africa, the Brazilian Pre-Salt developments and in the Gulf of Mexico. For ultra-deep waters the main design challenge is related to the high external pressure that may cause collapse of pipelines. This potential failure mode is normally dealt with by increasing the pipe wall thickness, but at ultra-deep waters this may require very thick pipe that becomes very costly, difficult to manufacture and hard to install due to its weight. Facing the challenges of the pipeline design for ultra-deep waters, the Collapse Joint Industry Project (JIP) was started to develop a guideline for wall thickness design optimization for offshore pipelines with external diameter to wall thickness ratio less than 20 (D/t < 20). As part of the JIP, nine buckle propagation tests were conducted on full scale seamless pipes. This paper describes these experiments and new conclusions that were raised in light of the test results.
Brazil Campos Basin is under large offshore oil production activity. Many new giant oil fields are under development. In many oil fields Brazil has been using ship tankers converted as FPSO platform vessel. At this moment four FPSO are in final construction phase to be installed in Campos Basin (P-43, P-48, P-50 and P-54). Many oil cargo tankers are transformed to work as FPSO. Although they are showing good characteristics, some problems are rising. The turret design approach was used in the primary FPSO’s design phase but recently the spread mooring system is also under installation in Campos Basin. Two converted FPSO’s (P-43 and P-48) were installed recently using spreading mooring system. The P-43 was installed at 800 m of water depth in Barracuda field at Campos basin. It is brother P-48 is installed at Caratinga field. Both platforms are designed to produce 300.000 barril/day. New ideas about Floating Production Storage and Offloading (FPSO) system have been in focus since some projects started working in an appropriately FPSO design direction. The Naval Architecture and Marine Engineering Department at COPPE/UFRJ has been investigating a new FPSO design and many ideas are under evaluation. One of these ideas is implement a ballast tank system to improve the floating platform behavior in waves with less structure stress. This paper presents the FPSO-H preliminary design. The aim of this project is investigate a new conception where deck are is used to separate accommodation and production plant. Also, the design applied the idea that the number of tanks should be increased to allow better weight distribution and improve the tanks inspection plain. In addition the design includes ballast tanks to increase the operator ability to control stability and vessel motion. The paper presents a case study of FPSO-H design for a Campos basin field. Graphics and tables shown the main results and recommendations are highlights for future work.
With new discoveries in the Brazilian Pre-Salt area, the oil industry is facing huge challenges for exploration in ultra-deep waters. The riser system, to be used for the oil transportation from seabed to the production unit, is one of them. The definition of riser configurations for ultra-deep waters is a real challenge. Problems have being identified for flexible risers, hybrid risers and steel catenary risers (SCR) configurations to comply with rules requirements and criteria in water depths of 2000m. The objective of this work is to present a study on the fatigue behavior of a Steel Catenary Riser in 1800m of water depth. One of the main challenges for SCRs in ultra-deep waters is the fatigue, due to platform 1st order motions, at the touch down zone (TDZ). A case study is presented for a Steel Catenary Riser connected to a semi-submersible platform. The influence of some design and analysis parameters is studied in order to evaluate their impact on the SCR fatigue life. The main parameters to be evaluated in this work are: The mesh refinement, in the global analysis, at the Touch Down Zone; The internal fluid density variation along the riser, and; The 1st order platform motions applied to the top of riser; In addition to the results of this paper, some highlights are presented for SCR analysis in similar conditions.
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