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

摘要：

建立了复杂储层的三维非规整网络模型,通过微观数值模拟研究了饱含水核磁T₂谱与孔隙尺寸分布间的关系,讨论了储层特征及饱和度等对T₂谱的影响规律。结果表明,饱含水岩样T₂谱与孔喉半径分布具有很好的相似性,随着喉道半径、孔喉比的增大,核磁T₂谱的峰值均向右移动,其不同之处在于:孔喉比增大时,孔隙体T₂谱与喉道T₂谱逐渐分开;含水饱和度为53%时,中等水湿岩样T₂谱左边部分与水湿岩样基本重合,右边部分弛豫时间明显大于水湿岩样;油湿岩样的弛豫时间在整个区间内均大于水湿岩样;随着含水饱和度的降低,强水湿岩样T₂谱峰值信号强度减弱,在左边短弛豫时间处出现另一缓慢增强的T₂峰;中等水湿岩样T₂谱原峰值处的信号强度降低,在右边长弛豫时间处出现一个以油的表面弛豫为主的峰。

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