Start-Up Optimization in Deep-Water Developments: Strategies for Managing Wax, Hydrates and Slugging

Abstract Objectives/Scope The XYZ-Field, located at Eastern offshore India, at water depth of 600 meters, features deep-water oil wells tied back to a centrally located FPSO via dual 10″ pipe-in-pipe (PIP) flow lines. Ensuring uninterrupted flow during the initial start-up phase is crucial due to challenges such as low ambient temperatures, slugging, wax deposition, hydrate formation and flow instabilities. Apart from these, well-tested results indicated a lower GOR, further complicating things. This paper presents a comprehensive set of flow assurance strategies designed to mitigate these risks and ensure a smooth production ramp-up. Methods, Procedures, Process Flow assurance simulations using OLGA and PIPESIM were conducted to evaluate transient start-up behaviour, wax deposition potential and slugging tendencies. The analysis identified several key challenges, including very low fluid temperatures at the time of well ramp-up which creating challenges like hydrate formation, wax deposition and crude gelation another issue was low flow rates at the time of wells ramp-up which leads to low thermal mass so fast decline in fluid temperature and slugging issue in pipeline which also helping in making cold spot in pipeline and leading to more wax deposition. To counter these challenges, an innovative start-up strategy was developed, which includes preheating of the line, increasing fluid flow at the time of start-up, choking at FPSO topside and optimising the start-up sequence of wells. Results, Observations, Conclusions With the help of this strategy we were able to maintain the temperature of pipeline throughout startup period above Wax appearance temperature which helped in avoiding wax deposition, crude gelation and also helped in avoiding hydrate formation another thing we eliminated the slugging using FPSO topside choke and by increasing flowrate which helped in getting stable flow at FPSO and no issue to equipment at the topside and this also stop making cold spot in riser which is more prone to wax deposition so resulted in less wax deposition. This strategy also helped in long-term operation of the field by minimizing the slugging and wax deposition, resulting in decreased frequency of mitigation measures to remove wax in the flowline. Novel/Additive Information These findings provide a robust framework for enhancing the reliability of deep-water oil field start-ups, reducing production downtime, and ensuring long-term flow assurance. The proposed innovative strategy for reducing the frequency of wax mitigation measures presents a significant improvement in operational efficiency while maintaining flow line integrity.

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