2018_EJRNL_PP_MAOJIN_TAN_1.pdf
Terbatas  
» Gedung UPT Perpustakaan
Terbatas  
» Gedung UPT Perpustakaan
Nuclear Magnetic Resonance (NMR) log can provide accurate porosity independent of lithology, and
NMR logging is more advantageous over conventional logs. In recent decades, it has been broadly applied
in reservoir evaluation and pore structure study of sandstone and carbonate formations. But in igneous
rocks, NMR porosity is underestimated compared to the actual porosity, which limits the application of
NMR measurement in such reservoirs. To tackle this problem, NMR measurements were firstly introduced
from DX, XS, and CPZ regions, China, and the effect of different igneous rocks on NMR porosity was
analyzed in detail. NMR transvers relaxation time (T2) of igneous rock is very short and the T2 distribution
is in fast relaxation region, and the amplitude of NMR signals is so low. From NMR measurement analysis,
NMR porosity relative error generally increases from acid, middle to mafic igneous rocks. Then, combined
with element measurement, some influential factors were summarized from laboratory experiments and the
relationships of NMR porosity relative error between different paramagnetic elements and magnetic
susceptibility were investigated. The elemental analysis from plasma emission spectrometer showed that,
NMR porosity relative error is related to paramagnetic mineral contents, and it generally increases as the
iron and manganese contents increase. Moreover, the magnetic susceptibility of igneous rock is usually
significantly greater than the sedimentary rocks, and from acid, middle to mafic igneous rocks, the
magnetic susceptibility trends to increase. According the above analysis, some NMR porosity correction
correlations are constructed. Finally, in case study from CPZ region, NMR logging porosity was correlated
by the constructed correction correlation from iron content of element spectrum capture log, the corrected
NMR porosity is in good agreement with core porosity, which proves the empirical correction method from
the paramagnetic element contents reliable. Therefore, this study provides the foundation for NMR
measurement correction and NMR logging interpretation of such complex igneous rocks formation