Scraping Assessment of Offshore Marine Risers

Abstract

Abstract The engineering assessment in this paper provides the recommendations for the minimum wall thickness selection of marine riser pipeline and their ability to allow the passage of in-line instrument scraper. The assessment was conducted considering two criteria: First, the minimum wall thickness for riser is evaluated against the minimum bore required by in-line instrument scraper provided by several service contractors for in-line inspection. Second, the riser minimum wall thickness is benchmarked with the minimum acceptable wall thickness specified by DNVOS-F101 [1] and Saudi Aramco engineering standard for submarine pipeline design. The outcome of this analysis is the following recommendation: The minimum wall thickness selected for riser pipeline diameters less than 8″ shall not be less than the values tabulated in Table 1 for each service. These values ensure that adequate protection measures are considered during the design of pipeline which is in-line with the requirement of DNV-OS-F101. In addition, the outcome of the assessment results into a collective projected cost avoidance of $ 0.94M per meter of pipeline and reduces carbon foot print.