Flow assurance problems related to flow slugging, hydrates, and wax gelling lead to this study, post two integrated oil pipelines clogged in the Caspian Sea during the winter season. The methods and proposed solutions will be further deliberate, which includes the development of operating envelope to ease implementation. The overall methodology is based on dynamic flow assurance simulation and mathematical analysis, which was adapted depending on the problem being studied. Reduced production and terrain undulations had caused severe slugging in both pipelines which are flowing multiphase fluids. The bifurcation analysis of slug control valve will be discussed to determine the best choke opening that can eliminate slugging. The flow slugging also caused hydrate risk that was made worst during shutdown. Few strategies of hydrate mitigation including implementing extra heat insulation at riser air gap, gas flaring, optimised and overdose injection of mono ethylene glycol (MEG) were considered. Hydrate mass was evaluated for all the mitigations and requirement to inject lean MEG immediately after shutdown or prior start-up was identified. In terms of wax management, lower Flowing Tubing Head Temperature (FTHT) from wells added a challenge with limited facilities capability to operate more than the wax appearance temperature (WAT). Operating envelope of crude oil heater under heating limitation will be clearly shown to avoid operating in wax region. The development of operating envelope had enabled Operations personnel to know the safe condition to operate both pipelines during critical scenarios. The approach has changed the way the company operates, to ensure production is protected and maintained with minimal disruption caused by slugging, hydrate and wax gelling events.

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