Size Dependent Deformation of Nano-scale Pores during Consolidation

Abstract

One of the main challenges to effectively evaluating oil and gas reservoirs is determining the evolution of porosity and permeability during burial. During early diagenesis, consolidation is a critical process in all sedimentary rocks, reducing porosity, mean pore size, and subsequently permeability (Athy, 1930; Hedberg, 1936; Neuzil, 1994; Dewhurst et al., 1999). However, the evolution of all these parameters is ultimately determined by changes in pore size distributions within the sediment. Although experiments and field-based observations have provided crucial insight into the impact of consolidation on mud-rich sediments (e.g., Dewhurst et al., 1998; Yang and Aplin, 1998, 2007), a systematic approach that can predict the evolution of textural characteristics has yet to be fully achieved. Here, a mathematical model is presented that describes the evolution of pore size distributions during sediment consolidation. In addition, the model is tested by comparing numerical solutions with experimental data, providing a new quantitative tool with which to assess the mechanical behavior of sediments. Furthermore, we demonstrate that pore deformation decreases significantly with pore size and the magnitude of this effect is also calculated. Implications of the results for the behavior of other sedimentary rocks are also discussed.