Ormen Lange

Case Study 4 Thermodynamic Inhibition Canyon Express and Ormen Lange Flowlines... 

The above two examples serve to illustrate that more severe conditions of gas recovery require large expense in thermodynamic inhibitors. The high pressure and high water production at Canyon Express and the steeply upward sloping lines and subfreezing temperatures of Ormen Lange are harbingers of more severe conditions in the future. There are some cases in which the cost of hydrate inhibitors determine the project viability. 

Forty-six case studies of hydrate plug formation and remediation are recorded in Hydrate Engineering (Sloan, 2000). In every case, hydrate plugs were remediated. In addition, a rule of thumb is that most of the offshore flowline shut-ins are less than the 10 h no touch time, which requires no antihydrate operation before restart (J.E. Chitwood, Personal Communication, August 1, 2003). However, hydrate prevention methods are very expensive, as shown in the above Canyon Express and Ormen Lange examples, or in the fact that deepwater insulation costs are typically U.S.Sl million per kilometer of flowline. 

This strategy was successful in extending the field life by almost 2 years. This is one key example of the risk management philosophy, enabled by operating experience on the platform. The hydrate plug prevention technique in this case study is time-dependent and should be contrasted with thermodynamic (time-independent) inhibition methods in Case Study 4 of Canyon Express and Ormen Lange. 

There is no evidence for oleanane in any fluid inclusions or in any core extracts, suggesting that expelling Cretaceous source rocks have not contributed to hydrocarbons in the studied traps. However, Cretaceous strata seem clearly to be the source rock for some of the shallow high GOR traps in the deep water regions and may in our perspective represent an attractive gas play scenario for Ormen Lange and are certainly the source of the 6507/2-2 DST.2 petroleum. 

Figure 3. Illustration of Subsea to beach concepts - Snohvit and Ormen Lange.

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