Phase ‐ field Modeling of Fracture Cementation Processes in 3 ‐ D

Abstract

Numerical simulations of fracture cementation contribute to a better understanding of processes involved in their formation and possess the potential to provide valuable insights into the rock deformation history and fluid flow pathways. In this study, the influence of an algorithmically generated fracture surface is investigated, which opens-up temporally along a curved trajectory, on the cement mineralization in 3-D. By adopting a thermodynamically consistent and numerically efficient phasefield approach, the benefits of accounting for an extra third dimensionality are explained. The 3-D simulation results are supplemented by innovative numerical post-processing and advanced visualization techniques. The new methodologies to measure the tracking efficiency of fracture cements reflect the incremental fracture opening and demonstrate the importance of accounting the temporal evolution of grains in 3-D; no such information is usually accessible in field studies and difficult to obtain from laboratory experiments. The grain growth statistics obtained by numerically post-processing the 3-D computational microstructures show that cement's grain boundaries and multi-junctions are preferentially arrested at fracture peaks, thereby, enhancing the tracking behavior of syntectonic rock microstructures. By analyzing the temporal evolution of the numerically simulated microstructure, it is found that the grain multi-junctions are pinned more strongly at the peaks on the fractured surface, as compared to the grain boundaries.

Quartz Cementation in Polycrystalline Sandstone: Insights From Phase‐Field Simulations

“…In the past decade, the phase-field method has established itself as a viable alternative for simulating mineral growth in 2-D and 3-D (Ankit et al, 2013;Ankit, Urai, et al, 2015;Ankit, Selzer, et al, 2015;Prajapati et al, 2017Prajapati et al, , 2018aPrajapati et al, , 2018bWendler et al, 2011Wendler et al, , 2016. In contrast to the aforementioned front tracking models that were based on the sharp interface approach, the phase-field models describe interfaces as diffuse regions.…”

Shale Anisotropy and Natural Hydraulic Fracture Propagation: An Example from the Jurassic (Toarcian) Posidonienschiefer, Germany

“…Previous numerical models have recreated this antitaxial texture by assuming that crystals at the median line have random crystallographic orientations (Ankit et al, ; Hilgers et al, ). These models then posit that cementation occurs by epitaxial overgrowth of these randomly oriented seed crystals, such that crystal growth passively fills in the space between the fiber tip and the vein wall.…”

“…Accordingly, if the walls of a growing vein move apart slowly enough, each crystal will be able to grow fast enough to fill that ephemeral space regardless of crystallographic orientation, and fibrous fill will result. In contrast, if the vein opening rate is faster, only those crystals having fast growth axes at the high angle to the vein wall will keep up with the opening rate, and a coarser fill style will develop, which also has a crystallographically preferred orientation (Ankit et al, ; Hilgers et al, ; Lander & Laubach, ).…”

Three‐Dimensional Phase‐Field Investigation of Pore Space Cementation and Permeability in Quartz Sandstone

“…The multiphase-field model used in the present work has been previously employed by Ankit, Selzer, et al (2015), Ankit, Urai, and Nestler (2015), and Wendler et al (2015) to address the problem of mineral growth in quartz veins. For the sake of completeness, the model equations describing cementation are recapitulated in section 2.1.…”

“…The phase-field method, broadly used in the material science community for modeling microstructure evolution accompanying phase transitions (e.g., review articles; Chen, 2002;Moelans et al, 2008;Nestler & Choudhury, 2011;Qin & Bhadeshia, 2010), has recently emerged as a powerful computational approach for modeling anisotropic cement overgrowths in calcite (Prajapati et al, 2018) and quartz veins (Ankit et al, 2013, Ankit, Selzer, et al, 2015, Ankit, Urai, & Nestler, 2015Wendler et al, 2015). These works provide a basis for an entirely new generation of cementation models for sedimentary basins.…”