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| A new method of NMR echo data inversion constrained by priori information |
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JIN Guowen1,2, XIE Ranhong1,2, XU Hongjun3, GUO Jiangfeng1,2, GAO Lun1,2
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(1.State Key Laboratory of Petroleum Resources and Prospecting in China University of Petroleum(Beijing), Beijing 102249, China;2.Key Laboratory of Earth Prospecting and Information Technology in China University of Petroleum(Beijing), Beijing 102249, China;3.PetroChina Research Institute of Petroleum Exploration and Development, Beijing 100083, China)
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| Abstract: |
| A new inversion method of nuclear magnetic resonance (NMR) logging constrained by priori information (ILT+) was presented for the inaccuracy of NMR inversion at short relaxation times. The priori information was computed directly from NMR echo trains using integral transforms. Specially the T2 tapered areas were computed using exponential hyperbolic sine transform (ESHT) and the mean value of the ω-th moment of T2 was computed using Mellin transform (MT). The numerical simulation and well data processing showed that the new method simultaneously constrained by two priori information synthesized the advantages of the new method constrained by single priori information, and improved the inversion accuracy of T2 spectrum at short relaxation times. This new method has broad application prospects for NMR data inversion in unconventional reservoirs such as tight sandstone and shale which usually contain more small pores. |
| Key words: nuclear magnetic resonance inversion integral transform priori information short relaxation times |
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