基于核磁共振技术的水力压裂孔隙结构演化特征  

Evolution Characteristics of Hydraulic Fracturing Pore Structure Based onNuclear Magnetic Resonance

作　　者：王佳澍 王琳琳[1] WANG Jia-shu;WANG Lin-lin(College of Safety and Ocean Engineering,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国石油大学(北京)安全与海洋工程学院,北京102249

出　　处：《科学技术与工程》2024年第30期12943-12950,共8页Science Technology and Engineering

基　　金：国家自然科学基金(22127812)。

摘　　要：水力压裂过程岩石孔隙结构的演化过程十分复杂,量化水力压裂过程中孔隙体积的变化对于理解水力压裂机理至关重要。采用自主设计的新型水力压裂实验装置对岩心进行了水力压裂实验,并利用核磁共振技术来定量表征完整水力压裂过程中孔隙结构的演变。研究结果表明:水力压裂过程中岩石的压力响应受注入速率的影响,且与岩心初始渗透率相关。当岩心的初始渗透率较低时,注入速率对压力累积响应影响较小,相反,对于具有较高初始渗透率的岩心,注入速率会显著影响压力变化;通过核磁共振得到了完整水力压裂过程孔隙体积演化规律。大孔体积的变化主导了岩石孔隙体积的变化,随注入速率的增加,孔隙体积增加显著。此外,随着岩心初始渗透率的提高,这种影响更加明显;水力压裂过程注入的流体不仅会形成水力裂缝,还会导致岩石孔隙体积发生显著变化,这些改变最终导致岩心的初始渗透性增强。注入的流体会引起岩石孔隙度和渗透率的变化,在常规水力压裂过程中被认为是无效的流体滤失在储层改造中起到了至关重要的作用,研究结果为进一步提高油气资源采收率提供了新见解。The evolution of rock pore structure during the hydraulic fracturing process is highly complex,and quantifying changes in pore volume is crucial for understanding the mechanism of hydraulic fracturing.The hydraulic fracturing experiments were conducted on rock cores using a self-designed experimental setup,and NMR(nuclear magnetic resonance)technology was employed to quantitatively characterize the evolution of pore structure throughout the hydraulic fracturing process.The results show as follows.The pressure response of rocks during hydraulic fracturing is influenced by the injection rate and is correlated with the initial permeability of the rock core.Lower initial permeability results in a smaller response in pressure accumulation to injection rate,whereas higher initial permeability cores exhibit a significant response to injection rate variation.Complete pore volume evolution during the hydraulic fracturing process was obtained through NMR.Changes in macropore volume dominate the variation in rock pore volume,with a significant increase observed with increasing injection rate.Moreover,this effect becomes more pronounced with a higher initial permeability of the rock core.The fluid injected during the hydraulic fracturing process not only creates hydraulic fractures but also causes significant changes in rock pore volume,ultimately enhancing the initial permeability of the rock.The injected fluid causes changes in rock porosity and permeability.What is traditionally considered ineffective fluid leak-off in conventional hydraulic fracturing plays a crucial role in reservoir stimulation.The findings provide novel insights for further enhancing oil and gas recovery.

关 键 词：水力压裂 核磁共振 孔隙结构 定量表征 

分 类 号：TE348[石油与天然气工程—油气田开发工程]