Abstract
Monoethylene glycol (MEG) is the primary hydrate inhibitor used in today's large gas fields. To fully prevent hydrate formation, high dosage rates of over 1 gallon of MEG per gallon of produced water may be required. As a result of these high rates, MEG usage can reach into the 100s of tonnes per day for a field.
The first estimate of MEG requirement stems from subsurface analysis of expected water production and it becomes the starting point for a design process that may lead to excess. A standard inhibition system must accomodate large uncertainties due to inaccurate MEG distribution to each well, inaccurate measurement of water production from each well, and difficulties recovering and reclaiming the MEG through topsides processing. The compounding of these uncertainties then requires a planned overdose of MEG to insure total hydrate inhibition. Determining the planned overdose and the necessary equipment to achieve it often leads to a doubling of system size, which can push the capcity of the MEG system into the 1000s of tonnes with a concurrent major increase in CAPEX. Likewise, the operation of an oversized systems leads to a significant increase in OPEX from energy usage for recovery, MEG replacement from loss, and other factors.
To combat this excess cost and make more fields economical, a hydrate management system has been identified that ties together industry proven equipment into an intelligently operated package. Uncertainties are reduced through the use of industry leading chemical injection metering valves to pinpoint and control the distribution of MEG, accurate metering using a variety of technologies to target exactly the amount of water in need of hydrate inhibition, energy efficient MEG recovery with up to 100% salt and solids removal, and real-time condition monitoring, performance evaluation, and process modeling to ensure that the whole system is operating optimally to prevent hydrates under any circumstance.
Tightening the use of MEG for hydrate inhibition with the hydrate management system can create substantial operational savings over the life of the field and, should it be included early enough in the design phase, has the ability to reduce overall system size resulting in substantial capital savings as well.
