Determination of nuclear magnetic resonance T2 cutoff value based on multifractal theory - An application in sandstone with complex pore structure

被引:121
作者
Ge, Xinmin [1 ,2 ]
Fan, Yiren [1 ,2 ]
Zhu, Xuejuan [3 ]
Chen, Yiguo [4 ]
Li, Runze [5 ]
机构
[1] China Univ Petr Huadong, Sch Geosci, Qingdao, Peoples R China
[2] CNPC Key Well Logging Lab, Qingdao, Peoples R China
[3] China Univ Petr Huadong, Shengli Coll, Dongying, Peoples R China
[4] Shanxi Yanchang Petr Grp Co Ltd, Res Inst, Xian, Peoples R China
[5] Qinghai Oilfield Nat Gas Dev Co, CNPC, Golmud, Peoples R China
基金
中国国家自然科学基金; 中国博士后科学基金;
关键词
SIZE DISTRIBUTIONS; IMAGES;
D O I
10.1190/GEO2014-0140.1
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The cutoff value of nuclear magnetic resonance (NMR) transversal relaxation time T-2 is vital for pore structure characterization, permeability prediction, and irreducible water saturation calculation. Conventional default values often lead to inaccurate results for rocks with complex pore structure. Based on NMR experiments and multifractal theory, we have developed an effective statistical method to predict T-2 cutoff values without other petrophysical information. The method is based on multifractal theory to analyze the NMR T-2 spectrum with the assumption that the T-2 spectrum is an indicator of pore size distribution. Multifractal parameters, such as multifractal dimension, singularity strength, and mass exponent, are calculated to investigate the multifractal behavior of T-2 spectrum via NMR experiments and a dyadic scaling-down algorithm. To obtain the optimal T-2 cutoff value, the rotation speed and time of centrifugation are enlarged increasingly to optimal centrifugal state. A predicating model for T-2 cutoff value based on multiple linear regressions of multifractal parameters was proposed after studying the influential factors. On the basis of the multifractal analysis of NMR T-2 spectrum, a reasonable predication model for T2 cutoff value was rendered. Upon testing, the predicted results were highly consistent with the experimental results.
引用
收藏
页码:D11 / D21
页数:11
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