测井技术2025，Vol.49Issue(5)：667-675,713,10.DOI:10.16489/j.issn.1004-1338.2025.05.002
二维核磁共振测井正演模拟方法研究
Forward Modeling of Two-Dimensional Nuclear Magnetic Resonance Logging Responses
摘要
Abstract
To reveal the response mechanisms of two-dimensional nuclear magnetic resonance(NMR)logging,establish a reliable interpretation basis,and address the challenges of accurate fluid identification and quantitative evaluation in complex heterogeneous formations,this study takes T1—T2 NMR logging as an example and develops a two-dimensional forward modeling approach that integrates Bloch equation solutions with instrument spatial sensitivity distributions.A comprehensive physical modeling framework was constructed,spanning from microscopic magnetization evolution to macroscopic logging responses,to simulate the effects of various factors such as water saturation,drilling fluid filtrate invasion depth,and signal-to-noise ratio(SNR)on the logging results.The results demonstrate that:①Based on a three-dimensional finite element model of the NMR detector,the model can simulate the distributions of the static magnetic field(B0)and the radio-frequency magnetic field(B1).By combining the saturation recovery carr-purcell-meiboom-gill(SR-CPMG)pulse sequence to solve the Bloch equations point-by-point and utilizing a spatial sensitivity function to weight the contributions from each unit within the sensitive volume,the model achieves high precision.②Simulations of T1—T2 spectral responses under different water saturation conditions show that increased water saturation shifts the spectral peaks towards shorter relaxation times,with an average deviation of the simulated peak positions from theoretical values not exceeding 3.5%.③SNR significantly impacts the results:when the SNR increases from 5 to 15,the error in spectral peak position decreases from 8.3%to 2.1%.④Simulations at different investigation depths can effectively distinguish the drilling fluid filtrate invasion zone from the virgin formation:the T2 spectrum of the invasion zone exhibits a single peak,while the virgin formation shows a bimodal spectrum.In conclusion,the proposed two-dimensional NMR logging forward modeling framework exhibits strong adaptability and predictive capability under complex geological conditions,providing effective technical support for quantitative fluid identification and high-resolution reservoir evaluation.关键词
正演模拟/Bloch方程/空间灵敏度/T1—T2谱/含水饱和度/信噪比/钻井液侵入Key words
forward modeling/Bloch equation/spatial sensitivity/T1—T2 spectrum/water saturation/signal-to-noise ratio/drilling fluid filtrate invasion引用本文复制引用
张新宇,罗嗣慧,肖立志,廖广志..二维核磁共振测井正演模拟方法研究[J].测井技术,2025,49(5):667-675,713,10.基金项目
国家自然科学基金项目"方位扫描核磁共振探测新方法与实验验证"(42204106) （42204106）
中国石油大学(北京)学科前沿交叉探索专项"万米深地随钻测井探测器关键技术研究"(2462024XKQY009) （北京）
