Experimental Investigation on the Relationship between Biot’s Coefficient and Hydrostatic Stress for Enhanced Oil Recovery Projects

Abstract

The majority of global conventional oil reservoirs have been dramatically depleted during the last few decades. To increase the oil production rate, enhanced oil recovery (EOR) techniques are commonly utilized. The ratio of the recovered oil volume to the rock volume change is defined as Biot’s coefficient. During the EOR operations, Biot’s coefficient continuously changes due to the fluid injection and oil production; however, so far, only porosity-dependent or constant values of Biot’s coefficient have been incorporated in the EOR calculations, which is not valid since the role of external stress changes is overlooked. In this research, the Biot’s coefficient of a sandstone formation was measured through the acoustic wave propagation technique. A stress-dependent equation of Biot’s coefficient was achieved for application in the EOR calculations. The findings illustrated that Biot’s coefficient decreases logarithmically with the hydrostatic stress. Moreover, the Biot’s coefficient varied from 0.52 to 0.60 for an applied hydrostatic stress of 3.50 MPa to 21 MPa. Furthermore, it was found that there was no anisotropy of Biot’s coefficient in the sandstone formations. The extracted empirical correlation can be utilized for EOR projects in which the recovered oil volume is of paramount importance economically.

Keywords

• EOR
• depleted oil reservoir
• poroelasticity
• pore pressure
• sandstone rock