Impact of Production Scheme on Pressure-Sensitive Reservoirs After Hydraulic Fracturing

ABSTRACT Tight oil reservoirs are typically pressure-sensitive, which can affect the well productivity and oil recovery rate when the reservoir pressure decays. In this paper, the pressure-sensitive of reservoir rock is studied using CT-monitored corefloods, during which the change of permeability and porosity of the rock can be determined under different effective stresses; meanwhile, numerical simulations are conducted to understand the conducted to understand the impact of flowback and production schemes on the oil recovery rate in the field scale. After the reservoir rock sample is saturated with the sample oil, different effective stresses are applied on the rock; the oil is continuously flooded through the sample, during which the porosity change is recorded through CT scans, and the pressure change across the rock is recorded to calculate the rock permeability at different time. After the numerical simulation results are history matched with the experimental results, different flowback and production schemes are studied. After fracturing, the bottom pressure was reduced to 15MPa by different steps. The change of permeability and porosity of the rock and its influence on oil recovery rate under different production schemes were observed. During production, the effective stress in the reservoir increases from about 10 MPa to 50 MPa. According to the pressure-sensitive experiment results, the permeability and porosity of the rock decreased to 22% and 89%. When the pressure sensitive effect is considered, the 10-year recovery rate is reduced from 27% to 17%, and the flowback rate is reduced by 13%.The numerical simulation results show that the rapid production scheme has the highest production and flowback rate, increasing the oil recovery rate by 6% and the flowback rate by 5.9% compared with the three or five steps. The change of production scheme has no significant effect on the relief of pressure-sensitivity and the well should be quickly flowback considering the potential effect of water-sensitivity. The change of rock permeability and porosity are firstly quantified in-situ using a CT-monitored coreflood. Combining the experimental and numerical simulation results, the production scheme can be optimized pressure-sensitive reservoirs.