核磁共振(NMR)测井是确定地层孔隙度的有效方法,已经得到广泛应用.但是,在我国部分油田的应用中发现核磁测井孔隙度与常规孔隙度之间存在明显差异.本文对NMR测井孔隙度观测模式和处理方法进行研究,分析了NMR孔隙度误差的来源.针对富含蒙脱石、伊利石和伊/蒙混层粘土矿物的陆相沉积砂泥岩地层,根据这些粘土矿物的NMR横向弛豫时间疋值特征以及孔隙度处理结果得到的4.0ms附近孔隙度分配量不合适,提出了新的观测模式和处理方法,并用实验验证了新方法的可行性.
Nuclear Magnetic Resonance (NMR) Logging has been widely used in determining porosity of formation. However, it is found that porosity difference between NMR and conventional porosity logging is unacceptable in some oilfields in China. In the paper, Magnetic Resonance Imaging Logging(MRIL) porosity acquisition activation and data processing method are studied. The cause for porosity difference between MRIL and conventional porosity logging is analysed. It is found that there are rich smectite, illite and I/S mixed layer clay minerals in terrestrial sand-shale formation. According to NMR transverse relaxation time T2 of clay minerals and the allocation of partial porosities near the bin of 4 ms, the new porosity activation and data processing method are given. The reliability of new method is proved in laboratory.