DENSIFICATION APPROACH FOR 3D-PRINTING SANDSTONE ANALOGUES

Geomechanical and transport properties of rocks are of great importance to geoscience and engineering. Typically, experimental programs depend on natural rocks from outcrops or wellbore cores drilled from reservoir formations, which introduce some degree of uncertainty due to the heterogeneous characteristics of rock samples. Binder-jet additive manufacturing (3D-printing) applied to rock models is becoming an emerging technology to characterize natural porous media in a repeatable and homogeneous fashion. As natural rocks that are composed of mineral grains and cement, binder-jet technology offers the capability to manufacture rock analogues with a wide variety of powders, including sand. Silica sand offers the ability to accurately reproduce pore geometry and the resolution to manufacture pore sizes similar to natural sandstones. 3D-printed sandstone analogues, which have similar physical and chemical properties to natural sandstones, allow us to use them in laboratory experiments in substitution for their natural counterpart. This is a promising alternative for experimental testing that can be used to calibrate numerical models in geoscience and engineering. The significance of this approach emerges due to a high interest to match specific geomechanical and transport properties to those in reservoirs. An M-Flex 3D printer (ExOne) located in the GeoPrint facility at the University of Alberta was utilized to 3D-print sandstone analogues. The initial condition of a 3D-printed sandstone shows a loose distribution of grains, and therefore high porosity (~45%) with respect to natural sandstones. In order to replicate more natural rock-like porous media, this study is focused on a densification approach into the 3D-printing rock process. The methodology analyzes a bimodal distribution of sand grain-size, which is a factor that affects packing. It also explores the use of different metal rollers to achieve mechanical compaction of sand layers. Finally, the study presents a map with the optimum printing location inside the job box of the 3D-printer. This map shows a location with coordinates where the specimen is built with more accurate geomechanical and transport properties.