基于单元体模型的核磁共振测井渗透率评价方法

为了解决低孔隙度、低渗透储层渗透率计算模型精度较低的问题,通过研究单元体模型,利用核磁共振测井资料表征谱面积与胶结指数,并建立了计算储层渗透率的数学模型（REV模型）。分析了REV模型中各参数与渗透率的关系,给出了模型中各参数的求取方法,并将REV模型与经典的Timur-Coates模型和SDR模型进行了对比。分析表明,谱面积与渗透率存在幂函数关系,相关系数达到0.88,胶结指数在谱面积和孔隙度确定的情况下与渗透率呈一次函数关系,相关系数达到0.82,谱面积与胶结指数共同决定了储层渗透率的大小,渗透率与谱面积及胶结指数的变化存在较好的一致性。研究结果表明,REV模型的渗透率计算精度明显高于Timur-Coates模型和SDR模型,具有推广应用价值。 

An NMR Logging Permeability Evaluation Method Based on the Representative Elementary Volume Model

In order to solve the problem that permeability calculation models have low accuracy for low porosity and low permeability reservoirs, a mathematical model for predicting reservoir permeability has been established by using NMR logging data to characterize spectral area S and cementation exponent on the basis of a study of the representative elementary volume model (REV model). The relationship of each parameter from the REV model and permeability has been analyzed, and the calculation method for all parameters in the model was taken into consideration. The REV model was compared with the classical Timur-Coates and SDR models, the study results indicated that there was a power function relationship between spectral area and permeability, with the correlation coefficient of 0.88. Given a certain of spectral area and porosity, the cementation exponent has a linear relationship with permeability, with a correlation coefficient of 0.82. The value of reservoir permeability is determined by both the spectral area and cementation exponent. There is a good consistency in the change among permeability, spectral area and the cementation index. The study results showed that the accuracy of permeability calculation by REV model was significantly higher than Timur-Coates and SDR models, which is worthy of popularization and application.