Enhanced Collapse Resistance for Different D/t Ratios of UOE Pipes for Ultra Deepwater Application

Energy consumption outlook shows that the demand for Oil and Gas is increasing worldwide and since most of the undemanding reserves are already being explored, new reserves means longer distances from the shore and increasing water depths, of up to 3,000 meters. Collapse resistance has become a key factor in the design of pipelines for ultra-deepwater applications. UOE process is commonly used for manufacturing pipelines of large diameter and the cold work involved in this forming process modifies the mechanical properties of the pipes. This paper presents the effect of thermal treatment on final material properties, proving the validity of enhancing collapse for different D/t, as allowed by DNV-OS-F101 α_Fab, and extending what has been shown as valid on previous studies. In this work, the inputs for the processing strategies are presented, along with coupon compression testing and full scale testing, in order to qualify the selected route as compliant with producing pipes with α_Fab equal to 1, for usual D/t combinations. An analysis of the predicted collapse pressure compared to the real collapse pressure of the pipes is also presented. The extension of the qualification process achieved successful results and allows the use of a fabrication factor equal to 1 in ultra-deepwater offshore pipeline projects. This enables the reduction of wall thickness, generating reductions in material and offshore installation costs and also potentially enhancing the feasibility of many challenging offshore projects.