Condition Assessment Techniques for Aged Fixed-Type Offshore Platforms Considering Decommissioning: a Historical Review

Abstract

In this study, the technical papers on structural condition assessment of aged fixed-type offshore platforms reported over the past few decades are presented. Other ancillary related works are also discussed. Large numbers of researches are available in the area of requalification for life extension of offshore jacket platforms. Many of these studies involve reassessment of existing platforms by means of conducting pushover analysis, a static nonlinear collapse analysis method to evaluate the structure nonlinear behaviour and capacity beyond the elastic limit. From here, the failure mechanism and inherent reserve strength/capacity of the overall truss structure are determined. This method of doing reassessment is described clearly in the industry-adopted codes and standards such the API, ISO, PTS and NORSOK codes. This may help understand the structural behaviour of aged fixed offshore jacket structures for maintenance or decommissioning.

A Useful Manufacturing Guide for Rotary Piercing Seamless Pipe by ALE Method

“…From the beginning of the introduction, the advantages of seamless pipe (i.e., increased pressure ratings, uniformity of shape, and structural strength and fatigue under load) were highlighted. Especially, uniformity of geometry and material properties of the seamless pipe may help to reduce the possibility of stress concentration, initial deflection, and welding-induced residual stress [54] which can lead age-related structural damage [55], such as fatigue cracking and its propagation, localized dents [56], corrosion [57,58], and combined corrosion-fatigue [59,60] or corrosion stress and deformation issues [61,62]. In particular, seamless pipe is used for the drilling, rigid-production riser, and small size piping systems by considering fatigue and structural capacities subjected to various types of environmental loadings.…”

Environmental impacts of utilization of ageing fixed offshore platform for ocean thermal energy conversion

“…Fixed offshore platforms are unique structures built in the sea or ocean and serve to carry industrial equipment for oil and gas production and drilling (14). Until 2020, it is estimated approximately 10,000 offshore platforms have been constructed and installed worldwide (15). According to Zawawi, Liew (6), there are over 300 shallow water-fixed oil and gas platforms in Malaysia which have already served its function for almost 20 years, with 48 % already exceeding their 25-year design life.…”

“…The construction of new offshore structures for OTEC platforms will require a lot of emissions with a very high embodied energy due to the need to produce parts and components of the structure (15). Embodied energy includes the total energy consumption during the processes of raw material extraction, production, operation, and final disposal at the end of the structure's lifetime (23).…”