Study on pore and fracture heterogeneity of high rank coal samples based on NMR technology and multi-fractal theories
Based on the NMR saturation and centrifugal T2 spectrum distribution curves of high rank coal samples in Qinshui Basin,coal samples were divided into three types.Applicability of single fractal and multifractal models to the quantitative characterization of pore size distribution of middle and high-order coal samples was analyzed,and the pore fractal characteristics were revealed by integrating pore structure and reservoir physical parameters.The results show that the T2 value of class A samples is between 1～1000 ms,and saturated T2 spectrum distribution shows a"single peak",which is dominated by the development of macro-pores,with good physical conditions.The T2 value of class B samples is mainly 0.1～300 ms,the irreducible water saturation is relatively high,the pore development is relatively small under the influence of compaction,and the average porosity and permeability are less than that of class A.The T2values of C and D samples are between 0.01～200 and 0.01～10 ms,respectively.The saturated T2 spectrum distribution shows"single peak state",and the pore permeability structure is the worst.The single fractal dimension has a good linear relationship with porosity,T2 cut off and other physical parameters.Meanwhile,there is a good negative correlation between multifractal parameters and single fractal parameters.Small and large pores are the key pore sizes affecting the change of single fractal parameters,while mesoporous pore distribution is the key pore size affecting the change of multifractal parameters.
coal reservoirspore-fracturefractal dimensionpore size distribution heterogeneity
NETL
NSTL
万方数据
