缝洞型油藏单井注氮气提高采收率技术政策研究

缝洞型油藏地质条件复杂，储层非均质性极强，虽然单井注氮气提高采收率矿场试验获得成功，但由于单井地质特征各不相同，使得注气效果差异大，注采参数需要进一步优化。为此，提出建立针对此类油藏的“一井一策”注气提高采收率技术政策，并以TA1井为例，在储层识别和预测基础上，构建储集体发育模式，采用“分类建模、分类数模”的方法再现油藏开发历程，表征剩余油分布特征，基于实体油藏模型优化转注时机、注气方式及注采参数。结果表明，TA1井洞顶存在5.28×10⁴ t剩余油，注入氮气能够形成次生气顶动用洞顶阁楼油，进一步提高油藏采出程度，基于模型确定最优转注时机为含水率93%时，注气方式为气水混注，周期注气量为60×10⁴ m³，注气速度15×10⁴ m³/d，焖井时间10 d，采液强度40 m³/d，预测增油2 496.0 t，该技术政策为注气方案编制和矿场实施提供了参考，实施后增油效果显著，推广到不同岩溶背景注气井均取得较好应用效果。

Technical Policy Study of Single Well N2 Injection for EOR in Complex Fracture-cavity Carbonate Reservoirs

Fractured-cavity carbonate reservoirs in Tahe Oilfield have complex geological conditions and strong heterogeneity.The oilfield test of single well inject N2 for EOR has been successful,but the effect are quite different between wells due to the difference of each well and the injection and production parameters need further optimized action.In this paper,we propose specific reproduce N₂ injection technology policy for each well in this kind reservoir.Takeing Well TA1 as an example,based on reservoir identification and prediction,we build reservoir development pattern,reproduce reservoir development process and characterize the distribution characteristics of remaind oil;based on the actual reservoir model,we optimize the injection timing,gas injection mode and inject-production parameters.The results show that there are more than 50000 t of remaining oil in the top cave of Well TA1.N₂ injection can form a secondary gas cap,which can better utilize the attic oil on the top of cave and further improve the recovery degree of the reservoir.We determined the optimal parameters based on the model that the best,inj ection time is when the water cut is 93%,and best injection mode is gas water mixed injection,cycle gas inj ection volume is 600000 m³,gas injection speed is 150000 m³/d,well soak time is 10 d,and liquid production intensity is 40 m³/d.This technical policy provides important basis for the preparation and implementation of gas injection scheme.After implementation of the plan,the effect of increasing oil is remarkable.lt has been applied to other injection wells with different karst background and achieved good results.