This paper describes a flow assurance method known as "cold flow". The method is suitable for deepwater liquid dominated fields and reduces costs and carbon emissions compared to conventional flow assurance methods by letting hydrate and wax deposits travel as inert solids with the production stream to the host fascility (e.g. an FPSO). A compact subsea unit that utilizes the cold flow method is presented and an experimental test setup at SINTEF's Multiphase Flow Laboratory is described. The unit consists of a recycle stream that seeds dry particles to a place where the bulk flow temperature is close to the hydrate formation temperature (HFT) and the wax appearance temperature (WAT). Water droplets coat the dry particles and become a part of the particles absorbing free water in the flow. In addition to the seeding mechanism, a robot operated induction coil removes inner pipe wall deposits by heating the pipe locally. Results from the tests show no build-up of solids inside the cold flow unit itself or downstream the unit. The flow system is also robust in terms of shutdowns and the production flow is regained easily. Measurements also show that the unit is robust with respect to increasing water cut (WC).

In Norway, the majority of offshore oil and gas fields will be developed through tie-back solutions. Here, the produced reservoir streams are transported over long distances on irregular terrain and cold ambient temperatures to processing facilities. This might result in the formation of hydrate particles that can lead to increased pressure drop and gradual or sudden plugging of the pipe. Measures to address them tend to be expensive or have a high environmental footprint. An alternative measure less costly and more environmentally friendly is the cold flow technology. Here, hydrates are formed under controlled conditions, resulting in a stable particle slurry that does not agglomerate and plugs the pipeline downstream. This study presents a technical and environmental evaluation of cold flow as a flow assurance technique to produce an oil reservoir using a long tie-back. The case study is a synthetic field located on the Norwegian Continental Shelf. Results show that cold flow can successfully be used to produce the reservoir with lower emissions. The advantages and limitations of the concept were identified and discussed, and a comparison is made against alternatives, considering energy consumption, emissions during operation, and carbon footprint.