大庆油田二类油层注聚时机研究

Study on Reasonable Injection Timing for Polymer Flooding in Class Ⅱ Reservoirs of Daqing Oilfield

大庆油田聚驱开发对象已由一类油层向二类油层转变,以往基于一类油层区块建立的标准已不适用,需要开展适合于二类油层的注聚时机研究。基于二类油层地质特征和开发状况,利用数值模拟方法建立二类油层地质模型,研究开始注聚时含水率和结束注聚时含水率对聚驱开发效果的影响,并结合现场进行验证,确定合理的开始和结束注聚时机。研究结果表明,在结束注聚时含水率相同情况下,开始注聚时含水率越高,聚驱阶段采出程度越低,聚合物用量越大,吨聚增油量越低,含水下降幅度越小,含水最低值越高。即开始注聚时含水率越低,聚驱效果越好。在开始注聚时含水率相同情况下,结束注聚时含水率越高,聚合物用量、聚驱阶段采出程度越高,吨聚增油量越低。当水驱至含水率96%时开始注聚,选择含水回升到96%~97%时结束注聚比较合理,含水最好不要超过97%。

The development object of polymer flooding in Daqing Oilfield has changed from Class Ⅰ reservoirs to Class Ⅱ reservoirs.The standards established in the past based on the blocks with Class Ⅰ reservoirs are no longer applicable,so it is necessary to research polymer injection timing suitable for Class Ⅱ reservoirs.Based on the geological characteristics and development status of the Class Ⅱ reservoirs,a geological model of Class Ⅱ reservoirs is established by using the numerical simulation method.The influence of water cut at the beginning of polymer injection and at the end of polymer injection on the development effect of polymer flooding is studied,and it is verified in the field to determine the reasonable starting and ending.The research results show that when the water cut is the same at the end of polymer injection,the higher the water cut at the beginning of polymer injection,the lower the recovery degree during the polymer flooding;the more the polymer,the lower the oil increase per ton of polymer;the smaller the water cut decrease,the higher the minimum water cut.That is to say,the lower the water cut,the better the polymer flooding effect at the beginning of polymer injection.When the water cut is the same at the beginning of polymer injection,the higher the water cut at the end of polymer injection,the more the polymer,the higher the recovery degree during the polymer flooding,and the lower the oil increase per ton of polymer.When the water cut reaches 96% for water flooding,the polymer starts to be injected.It is recommended to end polymer injection when the water cut rises to about 96%-97%.The water cut should not exceed 97%.