Abstract
Polymer flooding provides a better sweep compared with water flooding, but there is concern about maintaining sufficient injectivity. Longer fractures could provide injectivity, but pose a risk for early break-through and containment. In addition, shear dilation of unconsolidated sand is also expected to improve permeability and injectivity. Shear dilation causing absolute permeability enhancement was observed in tri-axial tests. The relationship between propagation pressure and confining pressure was determined in unconsolidated sands by a series of physical model tests. The accuracy of the minimum in-situ stress determination was also investigated in unconsolidated sands. The results demonstrated that there is a small enhancement of absolute permeability due to dilation of unconsolidated sand and they do have a difference in absolute permeability between stress states for increasing and decreasing effective stress. Besides, the geometry of fractures induced by viscous fluids in an unconsolidated formation is a dominantly planar fracture, although it is very tortuous. In view of isotropic stress in the horizontal plane, multiple fractures were induced in several directions.
