致密油藏的压裂开采过程中,压裂液对储层孔隙中原油的渗吸置换作用,逐渐成为提高采收率技术的重点研究领域.然而,渗吸过程中不同尺度孔隙原油动用特征及其机理尚不明确,严重制约了压裂液体系的优化设计与开采工艺的合理选择.以鄂尔多斯盆地长 7 段致密油藏为研究对象,采用两性表面活性剂(EAB-40)作为清洁压裂液体系主剂,结合T1-T2 二维核磁共振与润湿性测试,系统研究表活剂浓度对储层界面性质及压裂液渗吸驱油效率的影响规律,揭示其微观作用机理.实验结果表明,EAB-40 通过协同降低油水界面张力(达10-2 mN/m量级)与诱导润湿性反转(接触角由 147°降至 57.34°),显著增强毛细管驱动力与原油脱附效率;当表活剂浓度为 0.1 wt%时压裂液体系综合驱油效果最优.渗吸过程中,小孔隙因水湿矿物集中,表面活性剂扩散引发润湿性反转,驱动原油由小孔隙T2＜1 ms向中(T2 介于 1～100 ms)、大孔隙T2＞100 ms高效运移.聚合物分子改善压裂液体系流变性能,促进束缚油、盲端孔隙残余油深度动用.实现"IFT降低—润湿性反转—粘弹性流控"三重协同渗吸机制.

In the process of fracturing in tight reservoirs,the imbibition and displacement of crude oil in reservoir pores by fracturing fluids has gradually become a key research field of enhanced oil recovery technology.However,the production characteristics and mechanism of pore crude oil at different scales in the process of imbibition are still unclear,which seriously restricts the optimal design of fracturing fluid system and the reasonable selection of mining technology.Taking the Chang 7 member tight reservoir in the Ordos Basin as the research object,the amphoteric surfactant(EAB-40)was used as the main agent of the clean fracturing fluid system,combined with T1-T2 two-dimensional nuclear magnetic resonance and wettability test,the influence of surfactant concentration on reservoir interface properties and fracturing fluid imbibition and displacement efficiency was systematically studied,and its microscopic mechanism was revealed.The experimental results show that EAB-40 signifi-cantly enhances the capillary driving force and crude oil desorption efficiency by synergistically reducing the oil-water interfacial tension(up to the order of 10-2 mN/m)and inducing the wettability reversal(the contact angle is reduced from 147° to 57.34°).The comprehensive oil displacement effect of the fracturing fluid system is optimal when the concentration of surfactant is 0.1 wt%.During the imbibibibition process,the wettability inversion is caused by the concentration of water-wet minerals in the small pores,and the diffusion of surfactants causes the wetting inversion,which drives the crude oil to migrate efficiently from the small pores T2<1 ms to the middle(T2 is between 1 and 100 ms)and large pores T2>100 ms.Polymer molecules improve the rheological properties of the fracturing fluid system and promote the deep utilization of residual oil in bound oil and blind end pores.Realize the triple synergistic imbibibibibition mechanism of"IFT reduction-wetting inversion-viscoelastic flow control".