高凝油油藏水驱油效率影响因素

INFLUENCING FACTORS OF THE OIL DISPLACED EFFICIENCY BY WATER FOR HIGH POUR-POINT RESERVOIRS

高凝油油藏普遍采用注水开发方式,但冷水驱替会对储层产生伤害,影响水驱油效率。为完全模拟实际储层条件,采用含气原油进行水驱油室内实验,分别研究温度、渗透率、注水倍数、注水速率和润湿性对高凝油油藏水驱油效率的影响。研究发现:温度主要通过改变原油黏度和析蜡来影响驱油效率,驱油效率随温度的变化曲线具有明显的3个阶段;渗透率在原油析蜡前对驱油效率影响较大,但随着温度降低,析出的蜡质形成具有一定强度的空间网状结构堵塞渗流通道,导致渗透率的影响逐渐减小;随着注水倍数的增加,驱油效率呈上升趋势,但注水后期上升缓慢;相同注水倍数下,注水速率在析蜡前后对高凝油油藏的影响规律不同,针对不同储层温度合理选择注水速率对提高驱油效率十分关键。

Developing mode of the water flooding is commonly adopted for high pour-point oil reservoirs,but the cold water flooding will cause the reservoir damage and influence the oil displaced efficiency. In order to fully simulate the actual reservoir conditions,the live oil was used to conduct the water flooding experiment,the influences of the temperature,permeability,water injection multiple,water injection rate,wettability on the efficiency were respectively researched for the high pour-point oil reservoir. The studies found that the temperature affects the oil displaced efficiency mainly by changing the oil viscosity and wax precipitation,and moreover the changed curve shows three distinct phases; the permeability has a greater influence on the displaced efficiency before the precipitated wax,however,as the temperature decreases,the precipitated wax forms the spatial network structure with a certain strength and thus plugs the seepage channels,then the influence of the permeability decreases gradually; with the increase of the water injection multiple,the oil displaced efficiency presents the rising trend,but later the rise lowers down at the later stage of the water flooding; under the condition of the same multiple,the influence laws of the water injection rate are different before and after the wax precipitation for the high pour-point oil reservoir,so it iscritical to choose the reasonable water injection rate in the light of different reservoir temperatures to improve the oil displaced efficiency.