Simulation of ductile grain deformation and the porosity loss predicted model of sandstone during compaction based on grain packing texture

The content of ductile grains and grain packing texture have great influence on the quality of sandstone, especially tight sandstone. A new simulation method for ductile grain deformation during compaction in sandstone under triaxial stress servo based on the discrete element method (DEM) was established. The micro-mechanical parameters for the simulation were obtained using physical experimental data in the literature. The numerical simulation results of single ductile grains and sandstone with ductile grains confirmed the reliability of the simulation method, where the effect of grain crushing, cementation and dissolution on porosity evolution were not considered. The simulation and physical experiment results show the porosity of sandstone decreases linearly with the increase of ductile grain content. The relationship between porosity and effective stress can be predicted using exponential model, when the grain packing texture was one-component nature packing texture dominated and ductile grain content was less than 50%. When the grain packing texture changes to binary packing and the content of ductile grains was less than 50%, the porosity evolution curve show some fluctuations, and the monitoring compaction curve showed that the relationship between effective stress and porosity can not be represented by exponential model. The void ratio changes of sandstone with binary packing texture during compaction can be predicted based on grain packing texture, and the correlation coefficient between the predicted and simulated void ratio changes (e) were high, the average errors accounts less than 6% of the average of void ratio changes (e) when the content of ductile grains were less than 25%. The errors between predicted and simulated void ratio changes (e) based on packing texture increases with the increase of ductile grain content. When the content of ductile grains exceeded 50%, the exponential model was no longer applicable for sandstone, while the logarithmic model is better. In addition, the proposed simulation method is significant for the study of porosity evolution process and the quantitative evaluation of the relative importance of its diagenesis in sandstone having ductile grains. © 2021 Elsevier B.V.