Asynchronous and synchronous huff-n-puff water injection for enhanced oil recovery in water-wet tight oil reservoirs

The exploitation of tight oil faces significant challenges due to their low permeability, complex pore structures, and rapid production decline rates. Water-based enhanced oil recovery (EOR) methods hold great promise due to their low cost and wellbore safety. However, their effectiveness is significantly constrained by low injectivity and clay swelling. The water huff-n-puff strategy has demonstrated success in the Tuha Oilfield achieving economic production. Nevertheless, deeper mechanistic understanding is needed to elucidate the underlying recovery mechanisms. In this study, the effectiveness of two water-based EOR methods—asynchronous huff-n-puff (ASHNP) and synchronous huff-n-puff (SHNP)—was investigated using core flooding experiments on tight cores from the Santanghu Basin, China. Nuclear magnetic resonance was utilized to analyze oil recovery, characterize water front movement, …