Study on nuclear magnetic-resonance sample mud logging and in-site application
Cai Jian-hua1,2, Guo He-kun3, Liu Wei3
1. Central South University, Changsha City, Hunan Province, 410083, China;
2. Hunan University of Arts and Science, Changde City, Hunan Province, 415000, China;
3. Institute of Porous Flow & Fluid Mechanics CNPC & China Academy of Sciences, Langfang City, Hebei Province, 065007, China
Abstract：The theoretical basis of nuclear magnetic-resonance sample analytic technique is nuclear magnetic relaxation that the fluid-bearing spin hydrogen nuclear in the rock produced in uniformly distributed static magnetic field and action by radio-frequency field, the time of relaxation is different in the fluid with different porosity, the meaning of time relaxation spectra in reservoir physics is that the porosity with different sizes made up the proportion of total porosity in rock. The paper gained following knowledge after indoor experimental study and analyzing the practical test results of nuclear magnetic-resonance sample mud logging technique: ①in a condition of isotropic strata geology, the T2 time relaxation spectra of nuclear magnetic resonance reflects abundant physical information of surveyed samples, such as porosity, permeability and percentage of movable fluid and the T2 time relaxation spectra of nuclear magnetic resonance basically same to relative core can be gained by nuclear magnetic-resonance sample survey, without affecting by grain size of samples, proving that the technique can be used for debris analysis; ②the change of nuclear magnetic-resonance signal amplitude per unit volume and T2 geometric average value is very small before and after the samples being soaked by mud, so the influence of invading mud filtrate on nuclear magnetic survey is small and can be neglected; ③the nuclear magnetic sample mud logging and nuclear magnetic sample logging can gain very approaching physical parameters of reservoir, but the former surveyed results are more coincident to results of core measurement and oil test.
