Flow Assurance for Subsea Wells

Abstract

Abstract The focus of flow assurance analysis and design has often been from flowlineentry to the initial separator at the production facility. This paper focuseson the flow assurance issues that pertain to the well, with emphasis on thesubsea well located in cold environments. Consideration is given to design andoperational issues that result from management of flow assurance related tohydrates, with a brief discussion of other issues, such as wax, asphaltenes, and chemical compatibility issues. Introduction Oil production from the deep water Gulf of Mexico has increased dramaticallyover the past several years. Similar increases are expected in the coming yearsin several locations worldwide. While development of new facilitiesinfrastructure continues in these environments, production from subsea wells indeep water regions is increasingly common. Even in cases where newinfrastructure is included in the development, often a substantial portion ofthe production is derived from subsea wells. While flow assurance issues can have relevance in shallow water environmentsand with Direct-Vertical-Access (DVA) wells, the advent of subsea production indeeper waters has increased the importance of these concerns to system designand operations. In addition to flow assurance-related impacts on systemavailability, deep water developments may be susceptible to dramatically higherintervention costs associated with flow assurance related failures orimpairments. The importance of these issues is demonstrated to some extent bythe industry's significant investment in these technologies in the past severalyears (e.g., by Deepstar and by Petrobras). The impact of these issues must always be seen in terms of the overallproject economics, where tradeoffs between initial capital expenses andoperating costs are considered. To do this effectively, the hardware/systemdesign and operations planning must integrate flow assurance at each stage ofdevelopment. The need for flow assurance methodology in multiphase production lines(flowlines) is well established and some information on methodology isavailable in the literature. To date, there has been limited attention given toflow assurance concerns that are specific to subsea wells. This paper attemptsto define the flow assurance objectives for subsea wells, to indicate some ofthe design issues and operational constraints that may be inferred from theseobjectives, and to give a couple of examples of the analysis process used todefine design and operational parameters.