Experimental and Numerical Assessment of the Influence of Bottomhole Pressure Drawdown on Terrigenous Reservoir Permeability and Well Productivity

Abstract

During oil and gas fields development, a decrease in reservoir and bottomhole pressure has often a detrimental effect on reservoir properties, especially permeability. This study presents the results of laboratory tests conducted to determine the response of terrigenous reservoir core-sample permeability to changes in the effective stresses and a decrease in the reservoir pressure. The considered samples were exposed for a long time to a constant high effective stress for a more reliable assessment of the viscoplastic deformations. According to these experiments, the decrease of the core samples permeability may reach 21% with a decrease in pressure by 9.5 MPa from the initial reservoir conditions. Numerical simulations have been also conducted. These have been based on the finite element modeling of the near-wellbore zone of the terrigenous reservoir using poroelasticity relations. The simulation results show a limited decrease in reservoir permeability in the near-wellbore zone (by 17%, which can lead to a decrease in the well productivity by 13%).