Research on the New Method of Determining Subsurface Porosity of Unconsolidated Cores

Abstract

Abstract In this paper, we have derived the transformational relationship between the porosity under triaxial, biaxial stress and uniaxial stress respectively. Moreover, porosity tests under biaxial and triaxial stress for 11 groups of parallel unconsolidated core samples are conducted. Based on the transformational relationship, we have converted the tested porosity under triaxial stress into the porosity under biaxial stress and then compared it with the tested porosity under biaxial stress. The results indicate that the theoretical porosity model is reliable and deformation of unconsolidated cores is approximate elastic deformation of the rock body. Therefore, the porosity under uniaxial stress can be converted from the porosity under biaxial stress, which can simplify the experimental procedure and equipment, and provide a new way of determining subsurface porosity of unconsolidated cores. Besides, the Poisson’s ratio of unconsolidated cores is much larger than that of the normal clastic rock, and the actual conversion factor should be used for the conversion.