Work

Enhancing Oil Recovery in Ultra-Low Permeability Reservoirs Refracturing: Sweet Spot Evaluation and the Re-Pressurization Plus Infill-Fracturing Strategy

Year: 2026

Type: article

Abstract: Non-uniform production contribution caused by insufficient reservoir stimulation during initial fracturing significantly constrains the lifecycle and estimated ultimate recovery (EUR) of horizontal wells. Refracturing is therefore urgently required to reconstruct fracture networks and activate undeveloped reserves. In this study, a coupled geomechanics-matrix-fracture-seepage model is developed based on the Unconventional Fracturing Model (UFM) to characterize formation energy evolution and residual oil distribution. Simulation results indicate that initial fracturing provides limited energy diffusion (radius of 5- 30 m), resulting in a "strong near-well, weak far-field" pressure distribution and inefficient residual oil utilization. To address this, we propose a refracturing strategy combining "re-pressurization of existing fractures" with "inter-stage new fracture stimulation" (infill fracturing). this strategy significantly outperforms conventional refracturing, increasing the predicted cumulative oil production by 55.86%. Parameter optimization suggests that maintaining a pumping rate of 10- 12 m3/min and a fluid intensity of 1700- 1900 m3/stage, while optimizing proppant ratios for conductivity, maximizes recovery. This work provides theoretical guidance for sweet spot evaluation and refracturing design in ultra-low permeability reservoirs.

Source: Energies

DOI: 10.3390/en19041022