关键词: 逾渗网络模型, 核磁T₂谱, 孔隙结构, 润湿性, 饱和度, 数值模拟

Abstract:

A three-dimensional irregular network model was established for describing the porous structures of the complex reservoir.The relations between T₂ spectra of nuclear magnetic resonance and the distribution of pore radius in water-saturated rock were studied by using numerical simulation.The effects of the reservoir properties and the saturation on T₂ spectra were discussed.The results indicated that there was good correlation between the T₂ spectra distribution and frequency histogram of pore radius.While increasing the throat radius and the ratio of pore to throat,the distribution peak of T₂ spectra moved towards longer relaxation time.However,the superposition region of T₂ spectra distribution between pore body and pore throat became smaller when the ratio of pore to throat increased.When the water saturation is 53 %,the left part of the T₂ spectra for the intermediate-wet rock was almost superposed with that for the strongly water-wet rocks.The right part of the T₂ spectra for the intermediate-wet rock was obviously larger than that for the strongly water-wet rock.The relaxation time of the oil-wet rock was longer than that of the strongly water-wet rock in the whole range.When the water saturation decreased,the intensity of the peak signal of the strongly water-wet rock reduced,and there was another peak at the left short T₂ spectra.With the reduction of water saturation,the intensity of the original peak signal of the intermediate-wet rock decreased,and there was a peak at the right long T₂ spectra mainly came from the surface relaxation of oil.

Key words: percolation network model, NMR T₂ spectra, pore structure, wettability, saturation, numerical simulation