Evaluation of Damage Characteristics of Shale Reservoirs Based on Normalization of In-situ Nuclear Magnetic Resonance Data: Chang 7 and Shanxi Formations in the Ordos Basin
1 School of Petroleum Engineering, Xi’an Shiyou University, Xi’an 710065, China
2 Key Laboratory of Carbon Dioxide Storage and Enhanced Recovery in Shaanxi Province, Xi’an 710065, China
3 Key Laboratory of Special Stimulation Technology for Oil and Gas Fields in Shanxi Province, Xi’an 710065, China
4 Research Institute of Shaanxi Yanchang Petroleum (Group) Co., Ltd., Xi’an 710065, China
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Received
Published
Revised
2025-07-03
2026-06-08
2025-11-28
Online Date
2026-08-07
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摘要
针对页岩储层微纳孔喉结构复杂、非均质性强、传统渗透率法难以准确评价伤害程度的问题,提出基于核磁共振(nuclear magnetic resonance,NMR)技术并结合T2谱归一化处理的伤害评价方法。选取鄂尔多斯盆地延长组长7段与山西组页岩岩心,模拟典型压裂液体系下的储层伤害过程,利用小尺寸岩心在线采集核磁信号,开展归一化定量分析,并与传统渗透率变化率结果进行对比验证。结果表明:两类储层对压裂液的响应存在显著差异:在长7段储层中,清洁压裂液体系的归一化进液量变化率最高(45.06%),而清水体系最低(-3.19%);在山西组储层中,小分子体系表现最优(41.16%),胍胶体系较差(5.02%)。各体系在两类储层中的伤害趋势与渗透率法高度一致,验证了该方法的准确性与可靠性。研究结果表明,“在线核磁共振+归一化分析”可有效减小岩心非均质性和尺寸差异带来的干扰,提升评价结果的可比性与稳定性,为页岩储层伤害识别与压裂液体系优化提供了一种高效可靠的新路径。
Abstract
To address the challenges posed by the complex micro-nano pore structure and strong heterogeneity of shale reservoirs, which limit the accuracy of conventional permeability-based damage evaluation methods, a new evaluation approach based on nuclear magnetic resonance (NMR) combined with T2 spectrum normalization was proposed. Shale cores from the Chang 7 Member of the Yanchang Formation and the Shanxi Formation in the Ordos Basin were selected as representatives. Simulated damage experiments were conducted using typical fracturing fluid systems, with NMR signals collected online from small-sized cores and analyzed through normalized processing. The results were then compared with traditional permeability-based evaluations for validation. The results indicate that the two types of reservoirs exhibit significant differences in their response to fracturing fluids: in the Chang 7 reservoir, the clean fracturing fluid system shows the highest normalized fluid intake rate change (45.06%), while the clean water system has the lowest (-3.19%). In the Shanxi Formation reservoir, the small-molecule system performs best (41.16%), whereas the guar gum system shows relatively poorer performance (5.02%). The damage trends of each system in both reservoir types are highly consistent with the permeability method, validating the accuracy and reliability of this approach. The findings demonstrate that the “online NMR+ normalization analysis” can effectively reduce the influence of core heterogeneity and size differences, enhancing the comparability and stability of evaluation results. This method provides a rapid and robust tool for shale reservoir damage assessment and fracturing fluid optimization.
HE Yan-long, TANG Si-yuan, LIU Ke-yi, BAI Lu, WANG Wei-bo, HUANG Hai, WANG Zhi-gang.
Evaluation of Damage Characteristics of Shale Reservoirs Based on Normalization of In-situ Nuclear Magnetic Resonance Data: Chang 7 and Shanxi Formations in the Ordos Basin[J].
Science Technology and Engineering, 2026, 26(16): 6829-6838 DOI:10.12404/j.issn.1671-1815.2504999
核磁共振(nuclear magnetic resonance, NMR)技术作为一种无损、高灵敏度的微观结构表征手段,已广泛应用于页岩及致密砂岩储层的伤害评价研究。苏珍等[15]提出了一种基于Beta峰模型的NMR反褶积方法(NMR-deconvolution,ND),结合六阶导分析与最小二乘拟合,实现了类固体与流体弛豫峰的分离,从而快速、准确地表征页岩孔隙分布特征。王治国等[16]基于低场NMR技术开展了苏里格致密砂岩储层的压裂液水锁伤害实验,定量揭示了微纳孔内束缚水的滞留规律,明确了水锁伤害主要集中在2 nm以下的微孔中。靳军等[17]将NMR实验与分形理论相结合,计算储层分形维数并关联物性参数,实现了致密砂岩储层孔喉结构复杂性与储层分类的定量化评价。Xu等[18]和Da等[19]基于NMR技术揭示了水基压裂液对页岩及致密砂岩储层的损伤演化规律,结果表明,T2谱变化可敏感反映孔喉结构的改造效应。Dai等[20]结合流体入侵与原子力显微镜(atomic force microscope, AFM)揭示了压裂液导致的富黏土页岩孔隙劣化机制。Li等[21-22]基于NMR技术定量表征页岩孔喉结构与裂缝网络的演化特征,建立了T2谱参数与储层微观结构之间的定量关系,实现了裂缝-孔隙系统的动态识别。Li等[23]进一步结合NMR、扫描电镜(scanning electron microscope, SEM)与压汞(mercury intrusion porosimetry, MIP)实验,从微观层面揭示了压裂液作用下储层矿物溶蚀与孔喉连通性变化规律。Lin等[24]基于NMR实验分析了页岩气储层中压裂液滞留的孔径分布及其对渗透率的影响。Yuan等[25]及Zhang等[26]进一步强调了基于NMR的渗透率变化与伤害识别方法在储层损伤研究中的适用性与局限性。总体而言,现有研究在NMR表征、孔喉结构识别及储层损伤方面取得了显著进展,但如何在保证评价效率的同时有效降低岩心尺寸差异与非均质性对结果的干扰,仍是当前核磁共振储层精细评价中亟待突破的关键技术难题。
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