JIP Collapse Assessment of Offshore Pipelines with D/t < 15

New Wave Media

June 15, 2013

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Based on project experience, research, and joint industry development work, DNV issues a number of pipeline codes. These comprise service specifications, standards and recommended practices, and are highly regarded within the international pipeline community. The DNV OS-F101 ‘Offshore Standard for Submarine Pipeline Systems’ provides acceptance criteria and design procedures for pipelines. The standard applies modern limit-state-design principles with ‘safety classes’ linked to consequences of failure. The DNV standard is complemented by several recommended practices (RPs), which give detailed advice on how to analyze specific technical aspects according to stated criteria.

DNV Pipeline Codes / Offshore Standard DNV-OS-F101

• 1976 - DNV Rules for Submarine Pipeline Systems - The 1st complete pipeline code for offshore pipelines, based on allowable stress format.

• 1981 - DNV Rules for Submarine Pipeline Systems - Update of 1976 version and became a wide spread code

• 1996 - DNV Rules for Submarine Pipeline Systems - A completely new version, incorporating the limit state format with calibrated safety factors based on the SUPERB JIP work

• 2000 - DNV-OS-F101:2000 - Converted to pure technical standard

• 2007 - DNV-OS-F101:2007 - General Improvement - Aligned with ISO3183 Linepipe standard

• 2009 – ASME Global Pipeline Award

• 2012 - DNV-OS-F101:2012 - General Improvement, Aligned with ISO

65% of the world’s offshore pipelines are designed and installed to DNV’s pipeline standard. As the easy recoverable fields in shallow water have been developed, the trend within the O&G industry is to go for the more challenging prospects, reaching water depth of 3000m+. There is a lack of available technical information addressing the collapse of thick walled pipelines, therefore DNV is launching the JIP to assess the behaviour of pipelines with low D/t and re-visit the design equations and safety factors currently in use. One of the targets of the JIP is to optimize and reduce wall thickness for a deep- and ultra-deepwater pipelines while still complying with the strictest safety and integrity regime.

This JIP is targeting deepwater pipelines in Brazil. There is an major deepwater drilling effort going on off the Brazilian coast and while much of this effort is related to uncorking new pre-salt reservoirs, some are actually seeking deepwater post-salt reservoirs as has been recently found by Petrobras. The new well, informally known as Arjuna, is covered by the 1-BRSA-882-ESS (Indra) Evaluation Plan, and is around 130 km off the coast of Espírito Santo state, and 0.9 km northwest of the discovery well. The oil reservoirs, approximately 200 meters deep, are located 3,679 meters down, at a water depth of 2,143 meters.

With the amount of new deepwater discoveries going on and the fact that deepwater pre-salt and post-salt production is increasing, it is becoming critical to develop new deepwater pipeline designs that allow for pipes of lesser thickness which are lighter and much easier to handle, while still maintaining high safety standards. The O&G industry and especially the operators involved in deepwater E&P are investing significant sums to this end. To this end DNV is performing the JIP Collapse Assessment of Offshore Pipelines with D/t < 15 along with industry partners. We will take an in-depth look at DNV’s Collapse Assesment of Offshore Pipelines in future posts.

Paschoa, Claudio
Claudio Paschoa is Marine Technology Reporter's correspondent in Brazil.