Effects of Grain Size and Layer Thickness on the Physical and Mechanical Properties of 3D-Printed Rock Analogs

Abstract

Due to the complexity of the sedimentary and diagenetic processes, natural rocks generally exhibit strong heterogeneity in mineral composition, physicochemical properties, and pore structure. Currently, 3D printed (3DP) rock analogs fabricated from sandy materials (silica sand) are widely applied to study the petrophysical and geomechanical characteristics of reservoir rocks, which provides an alternative and novel approach for laboratory tests to calibrate the environmental uncertainties, resolve up-scaling issues, and manufacture customized rock specimens with consistent structure and controllable petrophysical properties in a repeatable fashion. In this paper, silica sand with various grain sizes (GS) and Furan resin were used to fabricate rock analogs with different layer thicknesses (LTs) using the binder-jetting 3DP technique. A comprehensive experimental study was conducted on 3DP rock analogs, including helium porosity measurement, micro-CT scanning, SEM, and uniaxial compression. The results indicate that the LT and GS have a great influence on the physical properties, compression strength, and failure behavior of 3DP rock analogs. The porosity decreases (the difference is 7.09%) with the decrease in the LT, while the density and peak strength increase (showing a difference of 0.12 g/cm3 and 5.67 MPa). The specimens printed at the 200 and 300 μm LT mainly experience tensile shear destruction with brittle failure characteristics. The ductility of the 3DP rocks increases with the printing LT. The higher the content of the coarse grain (CG), the larger the density and the lower the porosity of the specimens (showing a difference of 0.16 g/cm3 and 8.8%). The largest peak compression strength with a mean value of 8.53 MPa was recorded in the specimens printed with CG (i.e., 100% CG), and the peak strength experiences a decrease with the increment in the content percentage of the fine grain (FG) (showing a difference of 2.01 MPa). The presented work helps to clarify the controlling factors of the printing process and materials characteristics on the physical and mechanical properties of the 3DP rock analogs, and allows for providing customizable rock analogs with more controllable properties and printing schemes for laboratory tests.

Real-Size Reconstruction of Porous Media Using the Example of Fused Filament Fabrication 3D-Printed Rock Analogues

“…A number of studies discuss ways to reduce the porosity of synthetic specimens manufactured using the BJ process. The control of printing parameters in the BJ process, such as binder volume fraction [14,32,50], layer height, and particle size distribution of the expendable material (quartz sand) in research [51] allowed them to obtain specimens with different internal structures. In [14,50], the authors discuss the results of permeability and porosity measurements for specimens with different percentages of saturation with polymer binder.…”

“…The authors of [51] showed that changing the particle size distribution of the sand mixture (ratio of coarse to fine fractions) reduces the porosity of synthetic specimens from 49.3% (100% fine fraction) to 40.5% (100% coarse fraction) at a layer height of 200 µm. At the same time, reducing the layer height from 400 to 200 µm leads to a decrease in porosity of the specimens from 48.3% to 41.2% when using only coarse sand.…”