US EPA

4966147 

Journal Article 

Applications and characterization of NMR relation derived from sphere-capillary model 

Liu, TY; Xiao, LZ; Fu, RS; Wang, ZD 

2004 

Yes 

Diqiu Wuli Xuebao / Chinese Journal of Geophysics
ISSN: 0001-5733 

47 

4 

663-671 

WOS:000222988300017 

All pores in rock can be regarded as a system consisting of spherical pore and capillary pores. This paper presents a model of sphere-capillary. All pores are divided into different groups by their radii, and the relaxation time of each group can be calculated with the sphere-capillary model. The transversal relaxation time (T-2) spaced on the sphere-capillary model, can be utilized to conduct the inversion of NMR relaxation signal. Our research suggests that the T-2 distribution from the inversion is related with the special pore structure defined by the sphere-capillary model. Using different sphere-capillary models to derive different relaxation times, we conduct the inversion of relaxation signal with the relaxation time. When a T-2 distribution fits the relaxation signal in the least squares, the pore structure defined by the sphere-capillary model characterizes the pore system in rock best. Data from lab NMR measurements are analyzed with the sphere-capillary model, and the results are compared with the pressure data from mercury injection. The result shows that the sphere-capillary model describes properly the relaxation characteristic related with pore structure. Furthermore, the relaxation characteristic may be associated the with pore fluids. 

NMR; pore structure; mercury injection; sphere-capillary model; relaxation; petro-geophysics