Badak LNG Plant is expecting to receive new feed gas from deepwater exploration and other various exploration projects starting 2016. Most of these new feed gas sources will be significantly leaner than the current sources. This ‘leaner’ feed gas may impact to the plant operation with respect to LNG product quality, turndown capability of existing distillation columns, and may even have the potential freeze-out of heavy hydrocarbons. Therefore, some equipment modifications will be required to allow the LNG trains capable to process the delivered gas within plant operability.
Two scenarios were assessed for determining the optimum LNG plant operation dealing with this new feed gas. The scenarios are commingle and segregation modes.
In commingle mode, all LNG trains will process the feed gas at the same gas composition since the rich and lean feed gases are mixed. This mode will result in higher plant efficiency and flexibility compared to segregation mode. However, some modifications should be implemented for all trains. Commingle mode will result in lower LPG production since the leaner feed gas will need more LPG to be re-injected into LNG to maintain heating value (HHV) specification at 1,107 Btu/scf.
Meanwhile, in segregation mode, the operation of LNG trains will be divided into 2 groups: rich and lean. Modifications will only be required for trains which process the lean gas. This mode will result in two LNG products (rich and lean) with steady HHV. This will also produce more LPG due to less LPG reinjection into LNG. However, plant efficiency and flexibility will be lower due to less number of spare trains compared to commingle mode.
The solution to combine the advantage of both scenarios is proposed and called as ‘commingle hybrid’ mode. The commingle hybrid mode is presumed to give better result in term of LNG contract, additional LPG production, additional production revenue and less plant modification cost. Badak LNG will continue the plant operation in commingle hybrid mode for anticipating leaner feed gas.