Study Of NMR Technique On Rock Fluid Characterization

Nowadays,some NMR fluid characterization methods require specific and troublesome experimetal processes,while others depend on the gradient tools.But NMR core analysis devices developed in our country do not have this kind of gradient components.In order to find a fast and simple method for these devices to detect and differentiate oil and brine,many former works have been reviewed and a NMR fluid characterization technique is thoroughly studied,which is based on the internal gradients in rocks.Firstly,according to NMR spins diffusion regimes and character of internal gradients in rock pore spaces,a relaxation model of oil and brine phases is established and a method base on the diffusion measurements in internal gradients is also proposed.Secondly,this oil and brine differentiation problem is devided into two kinds of subproblems and inversion algorithms are given respcetively.Aimed to solve the linear inversion model,conventional SVD algorithm is improved.Experiments show that improved SVD algorithm overcomes the deficiency of the conventional one and also run much faster.Aimed to solve the nonlinear subproblem,an nonlinear optimization algorithm is used.Numerical experimets show that this algorithm works effectively,and this algorithm may have significant applications in inverison problems of more complex and realistic relaxation model in the future.Finally,in order to confirm the validity of this differentiation method,an software is developed by Visual C++ and Compaq Visual Fortran mixlanguage programming.Numerical simulation experiments show that this method can differentiate oil and brine phases,and also have some deficiencies.