Comparison of different inversion methods of D-T2 two-dimensional nuclear magnetic resonance logging and applicability analysis

D-T2 two-dimensional nuclear magnetic resonance (2D NMR) logging technology can distinguish pore fluid types intuitively; it is widely used in oil and gas exploration. Many 2D NMR inversion methods have been proposed thus far, but most of them are limited to numerical simulation. It is necessary to study the applicability of different inversion methods for NMR logging data of various acquisition sequences and to select optimal inversion methods for the 2D NMR logging software module. In this work, the principle of 2D NMR logging is studied; truncated singular value decomposition (TSVD), BRD, LM-norm smoothing, and TIST-L1 regularization methods are also studied in detail; and the precision and computational efficiencies of CPMG and diffusion editing (DE) sequences obtained from oil—water and gas—water models are compared, respectively. The inversion results and calculation time of TSVD, BRD, LM-norm smoothing, and TIST-L1 regularization are compared and analyzed through numerical simulation, and the inversion method is optimized to process the SP mode logging data from the MR Scanner instrument. The results show that the TIST-regularization method and LM-norm smoothing method are more accurate for the CPMG and DE sequence echo trains of the oil-water and gas-water models, but the LM-norm smoothing method is less time-consuming, making it more suitable for logging data processing. A case study in well A25 shows that the LM-norm smoothing method produces results consistent with GEOLOG software, demonstrating that the LM-norm smoothing method is applicable in practical NMR logging processing.