| 摘要 |
<p>511,768. Extracting oil by distillation from oil-bearing strata. BENSON, M. Nov. 19, 1937, No. 31842. [Class 55 (ii)] [Also in Group III] To improve the recovery of oil from wells, especially after the natural gas pressure has fallen, some or all of the oil is heated to or above the critical temperature by means of an expansive fluid, e.g. superheated steam, while a pressure above the critical pressure is maintained. Up to the critical temperature the more volatile fractions of the oil remain dissolved, thinning the liquid and facilitating drainage to the well; at the critical temperature the whole of the oil is vapourized without change of composition. Drainage is also facilitated by the reduction of surface tension and viscosity near the critical temperature ; condensation of the steam re-saturates the sand. The pressure and temperature may be the highest practicable having regard to the nature of the cap rock and the materials of the plant ; it is stated that the natural gas pressure in a well may be several thousand lbs. per sq. in. and plant using stainless or low-carbon steel (C=0.35 to 1 per cent.) is available in which steam may be superheated to 1,000‹C. The steam may be superheated by direct heating (electric or other) or by internal firing with a fluid fuel and air, oxygen, or both. The pressure may be controlled by a backpressure device (valve. de Laval nozzle, or turbine) on the well, and this device may be at the outlet of a condenser or cooler serving also as feed-water heater or steam generator. The oil may be fractionated during condensation, either without or with cracking. The steam &c. may be introduced to one of a group of wells.tapping a single pool. The process may be used in a partially-flooded oil-field.</p> |
