Abstract:

Compared with main layers in Daqing oilfield, the class II oil layer is characterized by severe interlayer heterogeneity that makes features of its polymer injection and oil production combination quite different from the main layer. Commingled injection in the class II oil layer can not well solve the problem of interlayer production because thin and poor layers could be hardly recovered and water fingering in thick layers occurs frequently, so the effect of polymer flooding is still not highly satisfactory. It is important to define the optimal adjustment moment of polymer flooding for different injection-production types of the class II oil layer in Daqing oilfield. There are four types of the injection-production combination for the class II oil layer in Daqing oilfield, i.e. thick-layer injection with thick-layer production, thick-layer injection with thin-layer production, thin-layer injection with thin-layer production, and thin-layer injection with thick-layer production. Through isobaric polymer flooding experiments on parallel models of the four types, we obtained the optimal adjustment moment for these four different types, namely the polymer volume at the optimal adjustment moment is 740 PV·mg/L, 780 PV·mg/L, 810 PV·mg/L and 860 PV·mg/L respectively. Ceasing polymer injection at the optimal moment for each injection-production well type could make the oil increment per ton polymer maximum and reservoir recovery the most effective. Therefore, ceasing polymer injection at the optimal adjustment moment and taking further measures in time to enhance oil recovery can make the injection amount of each well type efficient and economical. By comparing displacement effects between the thick-layer injection with thin-layer production and the thin-layer injection with thick-layer production, we concluded that the pattern of injection in a high-permeable zone and production in a low-permeable zone was the most favorable and effective way of the horizontal heterogeneous reservoir development.

Key words: class II oil layer, injection-production type, polymer flooding, heterogeneity, adjustment moment

摘要：

大庆油田二类油层与主力油层相比，油层非均质性更加严重，决定了其聚驱动态特征与主力油层有较大差别，二类油层笼统注聚过程中，层间开采矛盾依然较突出，薄差层动用程度低，厚层突进现象严重，聚驱整体技术经济效果不理想。为明确大庆油田二类油层不同注采类型井组的聚驱调整时机，达到最佳的聚驱效果，针对大庆油田二类油层4种典型的矿场注采类型，建立厚注厚采、厚注薄采、薄注薄采、薄注厚采4种注采类型井组，通过开展4种注采类型模型等压聚合物驱油实验，得到厚注厚采、厚注薄采、薄注厚采、薄注薄采最佳调整时机聚合物用量分别为740 PV·mg/L、780 PV·mg/L、810 PV·mg/L和860 PV·mg/L。各井组在最佳调整时机时吨聚增油量最大，提高采收率值最高，应在最佳调整时机停止注聚合物，同时应在注聚过程中及时采取跟踪调整措施，最大限度地达到不同注采类型井组技术经济界限注入量，提高聚合物驱效率和效果。通过对比厚注薄采与薄注厚采聚合物驱效果，得到了平面非均质地层开采时，高渗带注入、低渗带采出的注采模式驱替效果更好，更有利于开采。

关键词: 二类油层, 注采类型, 聚合物驱, 非均质, 调整时机