Investigating Recovery Potential through Depletion Development of Tight Oil Reservoirs via NMR Technology

Tight oil reservoirs have emerged as a vital component of the global energy landscape, offering both promising prospects and intricate challenges in their exploitation. Overcoming challenges to maintain sustainable production levels, including rapid declines, instability, and low primary recovery rates, is imperative. However, understanding the mechanisms behind production declines during the depletion development of tight oil reservoirs remains elusive. In this study, we employ nuclear magnetic resonance (NMR) online monitoring technology to quantitatively assess oil recovery on the pore scale and investigate the impacts of depletion development on tight oil reservoirs. Our experimental findings reveal a bimodal pore distribution within the target reservoir, characterized by a significant proportion of micronano pore throats measuring less than 0.1 μm in radius. A noteworthy nonlinear relationship exists between the T2 relaxation time and pore throat radius within the tight reservoir core, enabling the derivation of rock pore distribution from T2 spectra. Within these tight reservoirs, the recovery rate achieved solely through the utilization of formation energy during depletion development ranges from 7 to 10%. This finding underscores the substantial untapped potential for future oil recovery, with a significant volume of oil remaining trapped within the matrix. Our analysis indicates that primary oil extraction primarily targets macropores during depletion development, leaving the crude oil within the micropores largely undisturbed.