Abstract
Nuclear magnetic resonance (NMR) log is a powerful tool to obtain porosity and oil saturation in reservoir evaluation. NMR echo inversion, however, may give poor information in the two parameters if the ratio of signal-to-noise is not so good. Combining NMR log and some conventional logs, such as GR log, sonic log, and density log, a novel inversion algorithm is developed in this research. First, normalize the logging response, then, insert both the logging response equations and the definition equations of volume model into the NMR echo equations. By conducting the data inversion for both NMR echo and conventional logging data, the porosity and oil saturation can be calculated. The condition number of the inversion matrix is decreased, so, the inversion parameters own better stability and the random weak noise is stifled. Furthermore, the T2 spectral distribution derived from the new inversion seems to be sensitive to the small pores in tight reservoir. Due to the weak noise removal and sensitiveness of small pore, the novel inversion may be utilized in reservoir evaluation in shale oil and gas, such as the identification of “sweet spot”.
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Acknowledgements
This work is supported by National 13th 5-Year Plan of Oil and Gas Program of China (2017ZX05019-001), CNPC Research Project (No. 2017 F-16), National Natural Science Foundation of China (No. 41476027) and PetroChina Key Technological Program (No. 2016E-0503), all the research support funds are greatly appreciated.
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Jiang, L., Liu, T., Yu, C. et al. A Novel Inversion Combining NMR Log and Conventional Logs. Appl Magn Reson 51, 85–101 (2020). https://doi.org/10.1007/s00723-019-01176-y
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DOI: https://doi.org/10.1007/s00723-019-01176-y