Mechanism of "droplet flow" in alkaline flooding for enhancing heavy-oil recovery

The displacement mechanism of alkaline flooding to enhance the heavy-oil recovery was studied by the microscopic visualization test and core flooding test.The micromodel test indicated that during alkaline flooding of heavy oil,the alkaline solution could penetrate into crude oil and subsequently form a water column or water coated with oil film,giving a droplet flow.Through the high viscosity of droplet flow and the Jamin effect produced thereafter,the fingering of displacement fluid could be significantly inhibited so as to increase the sweep efficiency.With increasing the alkaline concentration,the more frequently the droplet flow phenomenon occurs,the greater the sweep efficiency is.The core flooding result showed that both the oil recovery and the pressure drop of alkaline flooding increased with increasing the alkaline concentration,this is consistent with the rule obtained from the micromodel test that the sweep efficiency increases with increasing the alkaline concentration.Therefore,the increment of the sweep efficiency due to the droplet flow in alkaline flooding is the main mechanism to enhance the heavy-oil recovery.