CO_(2)混相压裂液提高采收率作用机理实验研究

Experimental Study on Enhanced Oil Recovery Mechanism of CO_(2)Miscible Fracturing Fluid

柳1断块为低渗透油藏,呈现出采出程度低、采油速度低、水驱动用程度低的“三低”开发特征。为改善柳1断块的开发效果,开展CO_(2)混相压裂吞吐提高采收率矿场试验。为了明确CO_(2)混相压裂液提高采收率作用机理及主控因素,以室内实验为手段,开展高温高压条件下CO_(2)混相压裂液岩心驱替实验。利用高温高压长岩心驱替装置,进行储层渗透率、储层非均质性、原油黏度和不同压裂液添加剂等条件下的CO_(2)混相压裂液驱油效率实验,分析对比不同影响因素下的驱油效率规律,明确CO_(2)混相压裂液提高采收率的作用机制并分析主控因素。实验结果表明,储层渗透率、储层非均质性和不同压裂液添加剂等条件对储层提高采收率具有不同程度的影响,提高采收率的主控因素为添加剂的种类和渗透率,其中CO_(2)+增溶剂的驱油效率最好,提高储层渗透率可以有效提高CO_(2)+添加剂的驱油效率。在柳1断块稠油油藏开展CO_(2)混相压裂技术矿场试验,措施有效率100%,阶段增油10140t。

Liu 1 fault block belongs to low-permeability reservoirs,and has the characteristics of low recovery percent,low oil recovery rate and low producing degree by water flooding in the production.In order to improve the development status of Liu 1 fault block,field test of CO_(2)miscible fracturing huff and puff is carried out to improve oil recovery.In order to know the mechanism and main controlling factors of enhanced oil recovery by the CO_(2)miscible fracturing fluid,the core displacement experiment of the CO_(2)miscible fracturing fluid is carried out at high temperature and high pressure in the laboratory.The oil displacement efficiency experiment of the CO_(2)miscible fracturing fluid is made under the conditions of reservoir permeability,reservoir heterogeneity,crude oil viscosity and different fracturing fluid additives by using the long core displacement device at high temperature and high pressure.The oil displacement efficiency laws under different influencing factors are analyzed and compared,and the mechanism on enhanced oil recovery of the CO_(2)miscible fracturing fluid are clarified and its main controlling factors are analyzed.The experimental results show that reservoir permeability,reservoir heterogeneity and different fracturing fluid additives have different degrees of influence on enhanced oil recovery.The main controlling factors of enhanced oil recovery are the type of additives and reservoir permeability.Among them,CO_(2)+solubilizer may achieve the best oil displacement effect,and the increase of reservoir permeability may improve the oil displacement efficiency of CO_(2)+additives effectively.The field test of the CO_(2)miscible fracturing is done in the heavy oil reservoirs in Liu 1 fault block.The effective rate of the measures is 100%,and the oil production increased by 10140 tons at the stage.