Application of Multifractal Theory for Determination of Fluid Movability of Coal-Measure Sedimentary Rocks Using Nuclear Magnetic Resonance (NMR)

A precise evaluation of the fluid movability coal sedimentary rock is crucial to effective and secure utilization measures gas reserves. Furthermore, its complex pore structure diverse mineral components impact flow properties fluids in structures, causing accurate mobility be extremely challenging. Nuclear magnetic resonance (NMR) technology currently a prevalent technique assess unconventional reservoirs due capacity acquire abundant reservoir physical property data determine details. The free-fluid volume index (FFI) factor assessing application NMR technology, which can only derived through intricate saturation centrifugation experiments This research utilized nuclear tests on 13 classic coal-measure samples three lithologies reveal FFI value. Moreover, association between components, parameters, was then extensively analyzed, prediction model for constructed. results indicate that T2 spectra sandstone shale own bimodal distribution, with principal point 0.1 10 ms secondary peak 100 ms. majority mudstone provide unimodal main distribution range spanning ms, demonstrating most experimental are micropores transition pores. calculated from 7.65% 18.36%, depict evident multifractal properties. Porosity, content kaolinite, dimension (Dq), linearly positively correlated. In contrast, chlorite, illite, subtraction (Dmin − Dmax), proportion (Dmin/Dmax), singularity strength (Δα) possess negative linear correlation FFI, further used modeling. On basis aforementioned influencing factors values eight core samples, an constructed multiple regression analysis. accuracy validated by utilizing this approach five not included development. It revealed produced predictions, findings may serve as guide classification estimation types reservoirs.