Hydrate problems in deepwater flowlines
- R.J. Brown and Associates, Houston, TX (United States). Division of Kvaerner Earl and Wright
In the Gulf of Mexico (GOM), the ambient temperature below about 100 meters water depth (the thermocline), is as low as 44 F. The hydrate formation temperature for natural gas at the reservoir pressures encountered in the deeper waters of the GOM is substantially higher than the 44 F ambient temperature. In fact, below about 1,500 foot water depth, naturally occurring gas hydrates are present as ice-like lenses just below the sea floor. Classic dehydration is not possible. The injection of dew point depressants such as methanol or glycol is possible. Insulation is also a possibility. As an example of one selection process for deriving a workable solution to hydrate prevention/control in deepwater flow lines from subsea completions, this paper examines the approach taken to select the solution to the hydrate formation problems on Enserch`s Mississippi Canyon Block MC 441 Field Development Project. The project involved connecting dual flow lines from each well at two 3-well templates in about 1,525 feet of water to a shallow water production facilities platform located m 380 feet of water. Calculations indicated that the gas temperature in an uninsulated flow line would fall to ambient temperature in less than 1 mile from the wellhead. Considering that the platform was located about 3 and 6 miles from the two subsea well templates, and that free water would occur, hydrates were expected to be formed in the flow lines if nothing was done. Various possible hydrate control/prevention methods, including some of those currently in use in the North Sea, were investigated. The method chosen as the cost effective solution for the MC441 field development is a combination of low Cost open cell insulation around the six flow lines in a casing and methanol injection at the wellhead/manifold.
- OSTI ID:
- 55767
- Report Number(s):
- CONF-940230--; ISBN 0-7918-1268-5
- Country of Publication:
- United States
- Language:
- English
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