Data from: Characterization of fluid occurrence states in Shale reservoirs: Centrifugal-nuclear magnetic resonance experimental analysis

The occurrence states of fluids in shale reservoirs directly influence the
resource assessment of shale gas, reservoir permeability, selection of
development technologies, and economic benefits. Accurate analysis of
fluid occurrence states is a key foundation for the efficient exploration
and development of shale gas. To comprehensively elucidate the fluid
distribution characteristics within shale pores, this study integrates
centrifugation-nuclear magnetic resonance (NMR) experiments with stepwise
thermal drying and methane adsorption analyses. By examining the NMR T₂
spectra of shale samples under varying centrifugal speeds, the distinction
between movable and bound fluids is established, clarifying the influence
of pore structure on fluid occurrence. Quantitative relationships between
pore size and adsorbed/free gas are further investigated through methane
adsorption experiments. Results demonstrate that centrifugation
progressively removes water from macropores and microfractures, leaving
residual water mainly confined to micropores. The stepwise thermal drying
method efficiently differentiates movable water, capillary-bound water,
and clay-bound water. Integrating NMR analysis with methane adsorption
reveals a significant impact of pore size on fluid occurrence: micropores
predominantly store adsorbed gas, whereas macropores mainly contain free
gas. These findings provide a theoretical basis for shale gas development
and furnish essential data for optimizing exploration and production
techniques.