针对静态、动态渗吸对致密砂岩微观孔隙的动用特征及协同机制不明确等问题,采用核磁共振测试技术,开展静态和动态岩心渗吸实验,在分析岩心渗吸前后T2谱的基础上,研究了2种渗吸方式对微小孔隙和大孔隙的渗吸动用特征,评价了渗吸时间、界面张力和渗透率对渗吸效果的影响,提出了先静后动联合渗吸的新方法。实验结果表明:静态渗吸中微小孔隙(孔径为0.002 7～0.368 0 μm)采出程度高于大孔隙(孔径为0.368 0～23.000 0 μm),动用比例占58.7%以上,微小孔隙采出程度随渗透率的增加而提高,随界面张力的降低先提高后降低;动态渗吸中大孔隙采出程度高于微小孔隙,是总采收率的主要贡献者,随着界面张力的降低,大孔隙采出程度提高,微小孔隙和总孔隙采出程度先提高后降低,动态渗吸的最佳界面张力低于静态渗吸的最佳界面张力;先静后动的联合渗吸方式能够同时大幅提高微小孔隙和大孔隙采出程度。实践表明,先导试验井组首轮静动联合渗吸后,日均产油量增幅达336%,平均含水率降幅达29%,增油控水效果显著。该研究对提高致密油采收率具有较强的指导意义。
In response to the unclear production characteristics and synergistic mechanisms of static and dynamic imbibition on micro-pores,nuclear magnetic resonance (NMR) testing technology was employed to conduct static and dynamic core imbibition experiments.Based on the analysis of T2 spectra before and after core imbibition,the production characteristics of the two imbibition methods on small pores and large pores were studied,the effects of imbibition time,interfacial tension,and permeability on imbibition efficiency were evaluated,and a new method of combined imbibition,static first followed by dynamic,was proposed.The experimental results show that in static imbibition,the recovery degree of small pores (pore diameter:0.002 7-0.368 0 μm) is higher than that of large pores (pore diameter:0.368 0-23.000 0 μm),accounting for more than 58.7% of the produced proportion.The recovery degree of small pores increases with increasing permeability and first increases then decreases with decreasing interfacial tension.In dynamic imbibition,the recovery degree of large pores is higher than that of small pores and is the main contributor to the total recovery factor.With decreasing interfacial tension,the recovery degree of large pores increases,while that of small pores and total pores first increases then decreases.The optimal interfacial tension for dynamic imbibition is lower than that for static imbibition.The combined imbibition method,static first followed by dynamic,can simultaneously and significantly improve the recovery degree of both small and large pores.Practice shows that after the first round of combined static-dynamic imbibition in the pilot test well group,the average daily oil production increase reached 336%,and the average water cut decrease reached 29%,demonstrating significant oil increase and water control effects.This research has strong guiding significance for improving tight oil recovery.
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