A method of predicting T2 cutoffs from NMR logging data of tight glutenite reservoirs based on normal distribution simulation
ZHU Ming1, JIA Chunming1, MU Yuqing2, LI Jing1, HU Tingting1
1. Research Institute of Exploration & Development, PetroChina Xinjiang Oilfield Company, Urumqi, Xinjiang 830013, China; 2. Research Institute of Exploration & Development, Sinopec Shengli Oilfield, Dongying Shandong 257015, China
Abstract:T2 cutoff value is an important input for interpretation and evaluation of NMR (nuclear magne-tic resonance) logging data. The existing method of determining T2 cutoff is deficient, and brings a great challenge to the NMR interpretation of complicated reservoirs. A new method for calculating T2 cutoff value was proposed. Firstly, 21 core samples are classified into five types according to the morphological difference of NMR T2 spectra under full brine saturation. The morphological characteristics of the NMR T2 spectra in the states of full brine saturation and centrifugal irreducible water are analyzed. Then the normal distribution function is used to fit the NMR T2 spectrum of centrifugal irreducible water or movable water in macropores. The simulated T2 distributions are used to replace the experimental results of core samples to get the variable T2 cutoff value. Then calculate irreducible water saturation (Swi) and permeability. The advantage of the proposed method is that the T2 cutoff can be directly acquired from the NMR T2 distribution of full brine saturated condition. The actual data processing results show that the absolute error between the T2 cutoff value determined by this method and the core-derived results is less than 2.0ms. The ab-solute error between the corresponding estimated Swi and the core-derived results is less than 5.0%. Meanwhile, the predicted permeability is also in good agreement with the core-derived results. The method makes the applicability of NMR logging technique much improved.
朱明, 贾春明, 穆玉庆, 李静, 胡婷婷. 基于正态分布拟合的致密砂砾岩储层核磁共振测井可变T2截止值计算方法[J]. 石油地球物理勘探, 2021, 56(3): 612-621.
ZHU Ming, JIA Chunming, MU Yuqing, LI Jing, HU Tingting. A method of predicting T2 cutoffs from NMR logging data of tight glutenite reservoirs based on normal distribution simulation. Oil Geophysical Prospecting, 2021, 56(3): 612-621.
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