Current Status, Effective Strategies, and Recommendations for Water Flooding in Low-Permeability Mature Oilfields

During water flooding, low-permeability mature oilfields commonly face the contradiction of poor injectivity and low productivity, which leads to low recovery. This study systematically reviewed development practices in low-permeability reservoirs worldwide, summarized and analyzed the main challenges encountered during water flooding as well as the common countermeasures applied in the field, and proposed development recommendations to address current challenges. The results indicate that key factors affecting water flooding performance in low-permeability mature oilfields include poor reservoir connectivity, strong heterogeneity, mismatched well patterns and spacing, incompatibility between injected water quality and pore-throat structures, and low microscopic displacement efficiency. Currently, these problems are mainly addressed in field operations through three approaches: optimization of water injection strategies, modification of displacement modes (e.g., pressure-driven flooding), and changing of displacement agents. However, the further development of mature oilfields continues to face multiple challenges: Long-term injection and production have led to a highly dispersed distribution of remaining oil, thus increasing the difficulty of precise exploitation. Unclear technical standards for pressure-driven flooding limit its large-scale application. The energy transition imposes higher requirements on techno-economic viability. Therefore, it is recommended to enhance refined reservoir characterization and remaining oil distribution prediction, subdivision of water quality standards, deepen research into the mechanisms of pressure-driven flooding and optimize its operational parameters, and develop cost-effective displacement agents to promote the efficient development of low-permeability mature oilfields.