Study On The Inversion Algorithm Of Nuclear Magnetic Resonance Transverse-relaxation Distribution

Nowadays, strongly inhomogeneous static and radio frequency magnetic fields become an accepted environment for the development of various nuclear magnetic resonance(NMR)techniques. More and more NMR applications are being proposed and successfully operated in such fields. NMR logging equipment use the radio frequency pulse to obtain a series of single-exponential transverse-relaxation echo strings. To analyze the relaxation characteristics of pore fluid and fluid mode, study is made to measure the inversion spectrum of relaxation spectrum.The polarization process as well as echo strings detection in the nuclear magnetic resonance signal are introduced to acquire the inversion model. The size of the model depends on the echo time series and the number of sampling distribution points. The former is usually larger than the latter. Therefore, the whole spectrum of solutions of the equation is ill-posed, while random noises is inevitably interfused which have a bad impact on the inversion of the original model. In fact, the model is based on the first Fred Holm integral equation, singular value decomposition and non-negative least squares can be used to solve the initial equation, these basic methods could not meet the non-negative constraints and also have stated error.The error of the inversion would seriously affect the identification of the pore fluids. Based on the inversion principle, a new inversion method is put forward to apply to simulated data which achieve a better transverse-relaxation distribution.