This message has been cross posted to the following Discussions: Projects and Facilities and Flow Assurance Technical Section .
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Hydrate risk can be mitigated with the addition different types of inhibitors. Most popular ones are good old thermodynamic inhibitors and recent LDHI. Kinetic inhibitors are effective upto sub-cooling levels of below 14oC (approx) and on shut-in conditions of few days they are likely to lose the effectiveness altogether. Thermodynamic inhibitors devoid of these drawbacks are very popular in GoM and North Sea where the sub-cooling levels are likely to be >14oC. On the nature of working of such thermodynamic inhibitors, one of the major players has recently coined a simple concept that anything that 'dilutes water' is effective. To restate it, any soluble substance that reduces the proportion of water in the unavoidable aqueous phase of a hydrocarbon system mitigates hydrate risk. MEG, MeOH, DEG, TEG etc are such externally added substances that are miscible in water. Due to HSE concerns, it is being advocated to phase them out. The dissolved substances in formation water (mainly NaCl) can also do the same job. As a thumb rule and also confirmed by the simulation tools, about 20 g/l of dissolved salts can offset 1oC sub-cooling. Formation water with a salinity of 300,000 ppm can offset nearly 15oC of sub-cooling. However, a number of studies including the brief reviews that appeared in OGF of Jun 12 and Feb 14 did not refer to this effective, no-cost and environment friendly solution. I seek the views of the members and their experiences in treating TDS of formation water where ever possible as the first level of defense against hydrate risk and build the additional measures if required, around it.
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Dasari Babu
Director, Dasari Hydrocarbons
Bangalore
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