Occurrence characteristics and controls over mobile fluids in a tight sandstone reservoir

Using nuclear magnetic resonance (NMR) technology, this paper proposes a new pore structure parameter called ‘effective mobile fluid saturation’, which can account for two factors that influence mobile fluids in pores: the stiction of hydrophilic particulates on the surfaces of pores and the constraints of tiny throats. The new parameter quantifies the effective content of the mobile fluids and compensates for the deficiencies using conventional parameters like ‘mobile fluid saturation’. Pore-throat connectivity is crucial for effective mobile fluid saturation, which reaches its highest point when the sorting coefficient is in the range of 1.5–2.0. Recognition of the pore-throat configuration is crucial in assessing the effectiveness of mobile fluids in tight sandstone reservoirs. Factors that influence the effectiveness of mobile fluids in three types of pore structures are discussed from a diagenetic perspective, including the development of microfractures and secondary pores, recrystallisation, clay mineral precipitation, and other micropore structure characteristics.