超小井距在复杂断块油藏后期注水开发中的应用

枣园油田枣南孔一段油藏主要含油层位为孔一段的枣IV、V油组,油层平均有效厚度为58.3 m/19层;断块内有17条断层,划分为9个断块区,平均断块面积为0.19 km2。油层连通差,储层物性变化大,平面上注水井吸水状况不均衡,位于构造边部的采油井见不到注水效果,表现为低能低产,剩余油的潜力无法动用。通过室内驱替实验和理论公式计算得出,枣南孔一段油藏构造边部相对低渗区的合理井距为75 m;应用概率公式法、经验公式法及采收率-井网密度关系,计算平均井距75 m时井网水驱控制程度分别达到88.5%和89.6%,可提高最终采收率2.12%。超小井距注水首先在3个井组进行先导性试验,累计增油1 337 t,然后又在5个井组进行推广,受益油井产油量由39.1 t·d-1上升到54.7 t·d-1,增油15.6 t·d-1,累计增油2 172 t,预测油藏最终采收率从30.2%提高到31.3%。

Application of extra-small well spacing in late waterflooding development of complex fault-block reservoir

The main oil-bearing layer in the first member of Kongdian Formation of Zaoyuan Oilfield is Zao IV and V oil group.The average thickness of oil-bearing layer is 58.3 m per 19 layers.There are 17 faults in the block which are divided into 9 fault-block zones with an average area of 0.19 km2.The connectivity of oil-bearing layer is poor and the physical property of reservoir changes greatly.The water absorption for different areas is imbalanced.The oil production wells at the edge of the reservoir have not waterflooding effect with low productivity and unproduced remaining oils.Based on the laboratory experiment of natural cores,theory study,probability method,empirical formula and the relationship between well density and recovery,the reasonable well spacing at the edge of the reservoir was calculated to be 75 m and the control degree of waterflooding reached 88.5% and 89.6%.The ultimate oil recovery improved 2.12%.The pilot test of extra-small well spacing was processed on three well groups at first.The cumulative oil increased 1,337 t.After that,it was spread on the other five oil groups.The oil production of response wells increased from 39.1 t/d to 54.7 t/d with an oil increment of 15.6 t/d and a cumulative oil increment of 2,172 t.The ultimate oil recovery was predicted to increase from 30.2% to 31.3%.