Mitigating Flow Assurance Challenges in Deepwater Fields using Active Heating Methods

Abstract

Flow assurance challenges, mainly of hydrates and wax depositions, are amongst the key issues that must be resolved and mitigated to ensure that hydrocarbons can be efficiently and economically transported from well to processing facilities. As wells step further away from shore into deeper water, the flow assurance challenges are increasing tremendously due to prevalence of higher pressure and lower temperature conditions. Thus, the development of cutting edge technologies to cater for the ever increasing demand in exploring the hostile and technologically challenging deepwater fields is a matter of great urgency. One of the effective solutions to prevent the formation of wax or hydrates is to use active heating methods. This paper describes an overview of the available active heating methods and mechanisms which are being implemented as thermal management systems for flowline in deepwater fields. It also discusses the thermal performance calculation models available to aid the design and modelling of such systems. Some comparative studies are carried out to determine the advantages and disadvantages of each of the methods to establish a general reference source on the technology that provides the most significant economic impact without compromising the reliability and efficiency of the overall system. Active heating systems have been used in several projects in the North Sea, Gulf of Mexico and Offshore West Africa. This paper also summarizes these projects and their operating experience from open literature. In general, due to their operational flexibility and high efficiency through control of the pipeline temperature above the hydrate formation and wax deposition temperatures, active heating seems to be the most practical, economical and viable solutions in managing flow assurance issues; especially for the development of deepwater fields.

An Overview of Flow Assurance Heat Management Systems in Subsea Flowlines

“…Heat management systems is a practice of maintaining the fluid temperature inside the flowline well above the Hydrates Formation Temperature and WAT [49,50]. The heat management system is regarded as very valuable in flow assurance solutions due to its cost-effectiveness [50].…”

“…The heat management systems consist of active heating and passive insulation. The active heating system uses external heat sources like hot water, direct electrical, and electrically heat-traced flowline to warm the produced fluid [49] while the passive insulation system utilizes material like Mineral wool and Polyurethane with a low thermal conductivity to lower heat loss to the environment [49]. A heat management system flowchart is seen in Figure 2 below.…”

“…A heat management system flowchart is seen in Figure 2 below. In the last ten years, the design and operation of flowline heat management systems are increasing in preventing impediments caused by hydrates and wax deposition [49]. The flow efficiency in flowline insulation is affected by the distinctive issue of heat transfer [52].…”

“…Dry insulation materials are polyurethane foam and mineral with better heat transfer coefficients of around 1 W/ m 2 K are widely deployed for onshore and shallow water applications [50,87,93]. With dry insulation, the loss of heat to the environment is low and the hydrocarbon temperature is adequately maintained to reduce depositional issues [49]. Nevertheless, water ingress worsens the dry insulation performance [49] or degrades the insulation properties, and hence the need for a PIP system ( Figure 5).…”

The non-homogeneous flow of a thixotropic fluid around a sphere

“…Aside from being of theoretical interest, the thixotropic flow around a sphere is also closely linked with various industrial and medical applications as well. Flow assurance and drilling of oil & gas wells are prime examples in industry [25], and blood clotting disorder [26] and dysphagia (difficulty in swallowing) [27] are highlighted topics in medical applications. We believe that the current work will provide a useful insight for analyzing relevant flow scenarios of ultimate interest.…”