Clariant Oil Services Treats the Formation of Hydrates on Unmanned Platform in North Sea
- Reduction in the platform’s total cost of operation (TCO)
- Improved safety and handling due to non-flammable formulation
- Combined KHI/CI negated the need for separate pump skids and tanks on the already valuable platform real estate
- Chemical cost savings and reduced visits to the unmanned platform (to fill tanks) due to reduced required volume
Background
A combination unmanned platform and gas operator in the Dutch sector of the Southern North Sea had been using MonoEthylene Glycol (MEG) and MEG regeneration as its primary hydrate inhibition strategy. The line exports gas from an unmanned platform to an onshore terminal via a 10-inch, 17km long flowline.
A major concern for the operator was the resulting cost of hydrate formation, which had caused blockages in the flowline, and the incumbent hydrate inhibition method, which had driven the TCO above desirable levels. The platform conditions are shown in Table 1.
Table 1: System Conditions
| MGL Temperature Range | 4 to 50°C |
| MGL Operating Range | 25 to 50 bara |
| Gas Production | 912,000 Nm3/d |
| Water Rate | 3.6 m3/d |
| Condensate Flow Rate | 10.1 m3/d |
| Pigging Frequency | Once every 3 to 7 days |
| Subcooling | 0 to 5°C |
Clariant Oil Services Solutions and Value Delivered
The operator had raised concerns about the use of a combined KHI/CI. Because there would be occasions when water would be left in the MGL for up to 14 days, he feared the possibility that the KHI would stop inhibiting hydrate formation before that time. To alleviate these concerns, Clariant Oil Services performed a series of laboratory hydrate tests at a sub-cooling of 5o C (the maximum sub-cooling expected in the flowline) for 20 days.
Results from these tests identified no hydrate formation during this time. The results of the laboratory studies showed that HYTREAT should be applied at a recommended dose rate of 1.11% volume, wrt water production rates.
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