Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 150

HYDRAFLOW: A Multiphase Cold Flow Technology for Offshore Flow Assurance Challenges

R. Azarinezhad, A. Chapoy, R. Anderson, and B. Tohidi
OTC19485, Offshore Technology Conference, Houston, Texas, 5-8 May (2008)

Flow Assurance is a major challenge in offshore and deepwater operations. The current approach is based on preventing/delaying gas hydrate formation by using thermodynamic inhibitors (methanol, etc) and/or kinetic hydrate inhibitors and/or operating outside the hydrate stability zone by pipeline insulation and/or active heating. The above techniques are not economical and in some cases practical for deepwater operations, long tiebacks, and ageing reservoirs (i.e., high water cut). The industry needs new and novel techniques to tackle Flow Assurance in these challenging conditions. The approach presented in this communication, i.e., Hydraflow, is based on gas hydrates management, instead of prevention. HYDRAFLOW concept is based on allowing gas hydrate formation but preventing their agglomeration and pipeline blockage. The idea is to convert most or all of the gas phase into hydrates and transfer them in the form of hydrate slurry in the pipeline. Where produced water is limiting factor for hydrate formation, excess water (e.g. seawater) can be added. It is also possible to adjust the hydrate slurries viscosity by adjusting the amount of water. Anti­agglomerants and other additives might be necessary to control the hydrate crystal size and prevent solid blockage in these systems. Where possible, it is proposed to use a “Loop» concept which allows circulating the liquid phase (totally or partially) and its associated additives. The recycled fluid acts as carrier fluid, transferring produced hydrocarbons to their destination (e.g. platform). In this case, all or part of the additives including anti­agglomerants (AAs) can be recycled, hence reducing the operational costs and potential environmental impact. This paper presents the latest results of development of the HYDRAFLOW technology, including hydrate growth and kinetic for different systems (low and high GOR) and effect of salts (e.g. from reservoir brines or added seawater).

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