USING TWO-PHASE LNG EXPANDERS TO EXTEND LIFETIME OF DEPLETING GAS WELLS OR FOR NITROGEN REJECTION

摘要

The depletion of natural gas wells is the subject of increasing technical and economic interest. There are several reasons for this growing interest:rn1. It is difficult to predict the time when the natural gas well starts to deplete and to estimate the remaining time until the well is completely exhausted.rn2. Upgrading the facility to an advanced technology is too expensive in relation to the risk connected with the depletion.rn3. Reduced pressure in the gas well requires injection with nitrogen gas and increases the overall liquefaction costs.rnThe paper presents a new approach to extend the lifetime of depleting gas fields. The installation and operation of two-phase LNG expanders reduces the required feed gas supply in existing liquefaction plants, thus extending the lifetime of the gas well. In addition, for nitrogen injected gas wells, or nitrogen rich feed gas, two-phase LNG expanders can handle such feed gas, resulting in sub-cooling the remaining LNG and reducing the entire boil-off downstream of the expander. The investment payback time for LNG expanders is less than six months. The overall plant profit increases by using two-phase LNG expanders in a base-load LNG plant despite of the gas well depletion.