Microscopic mechanisms and dominant productivity controls of Frac-Driven Oil Recovery in tight reservoirs

Fracturing-driven oil recovery is a key technology for the effective extraction of tight oil and gas resources. To address challenges such as rapid production decline, difficulty in replenishing formation energy, and unclear microscopic displacement mechanisms during tight oil reservoir development, this study focuses on the Chang 8 tight oil reservoir in the Ordos Basin. Using nuclear magnetic resonance (NMR) and other techniques, laboratory core flooding experiments were conducted to investigate the dynamic development characteristics of fracturing-driven injection. The microscopic production behavior and influencing factors were quantitatively analyzed based on oil recovery from pores of different scales. The research results indicate that: under saturated oil conditions, crude oil primarily exists in medium and large pores; when permeability is low, medium and small pores are primarily utilized, while when permeability is high, medium and large pores are primarily utilized, the recovery factor showed a strong positive correlation with permeability, increasing by 11.55% when permeability increased from 0.42 mD to 1.47 mD, primarily due to enhanced mobilization from large pores During the injection process, increasing the water injection pressure can induce micro-fractures in the rock core, thereby expanding the contact area between oil and water, enhancing fluid mobility, and improving oil-water displacement efficiency. This effectively increases oil recovery, although the extent of improvement gradually diminishes. Therefore, it is necessary to determine an appropriate water injection pressure. The increase in fracture density can expand the contact area between oil and water, enhance fluid seepage capacity, and effectively improve oil displacement efficiency. The research results provide theoretical support for clarifying the microscopic mechanisms during the fracturing-driven injection process in tight oil reservoirs and for the efficient development of tight oil.