利用核磁共振测井评价储层的捕集能力

Application of nuclear magnetic resonance log to trapping capability evaluation

在常规油藏评价中常常忽略对盖层和储层组合的评价。特定储 盖层组合下的综合储集能力主要取决于盖层孔隙半径和储层孔隙半径之间的相对数值关系 ,这个数值关系可以用临界油柱高度表征。盖层一般为泥岩或其他类型的致密岩石 ,对其取心和岩心分析都很困难 ,导致盖层孔隙半径的计算精度不高或根本不能计算。根据核磁共振测井对岩石孔隙结构的敏感性 ,提出了利用核磁测井计算盖层和储层孔隙半径的方法 ,经过压汞资料的刻度后 ,核磁共振测井可以计算连续的孔隙半径。在渤海湾井区的实际应用表明 ,利用核磁共振测井计算的岩石孔隙半径对于确定储 盖层的临界油柱高度、评价特定储 盖层组合下的油气捕集能力。

The combination evaluation of cap rock and reservoir is often neglected in the conventional reservoir evaluation. For a given combination model of cap rocks and reservoirs, the numerical relationship between the pore radius of cap rock and that of reservoir defines the trapping capability and can be expressed as the height of threshold oil column. In general, the cap rock consists of shale or other tight rock. It is difficult to conduct coring and laboratory measurement, which leads to the low calculation precision of the pore radius of cap rock. On the basis of the sensitivity of nuclear magnetic resonance (NMR) log to the porous structure of rock, a new method to calculate the porous radii of cap rocks and reservoir with NMR log was presented. When the NMR log is calibrated with mercury injection data, the porous radii can be obtained continuously. Applications and case studies of the new method in Bohai Bay area suggest that the porous radii of rocks obtained from NMR logs are favorable for calculating the threshold of oil column height and can be applied to evaluate oil trapping capability of the special combination system of cap rock and reservoir and to identify the tight layers in a reservoir.