3D PRINTING POROUS ROCK MODELS: A REVIEW OF METHODS, MATERIALS, CURRENT LIMITATIONS, AND FUTURE POTENTIAL

Petrophysicists have long been confined to analyzing the pore systems of reservoir rocks that nature has made. Recent development of rapid prototyping machines capable of manufacturing three-dimensional models (known colloquially as “3D printing”) quickly and cheaply has opened the possibility of building synthetic models to test specific research questions in the laboratory concerning the flow, electrical and mechanical properties of reservoir pore systems. 3D Printers are found on most college campuses nowadays and industrial-grade printers are available for one-off jobs through several on-line portals.

Rapid prototyping is a family of related technologies for building three-dimensional models. These methods can be subtractive (like carving a statue from a block of marble) or additive (like building a wall from bricks and mortar). Subtractive methods are limited in their ability to print porous models because of the difficulty in producing non-linear holes in original solid. Additive methods offer the greatest potential for printing the intricacies of reservoir pore systems with the accuracy needed to test research hypotheses.

To accurately copy a reservoir rock, one must not only reproduce the physical arrangement of solid and void but also reproduce the physics of the surface separating them. To address the former, the printer must have high spatial resolution. To address the latter, it must print in materials that appropriately match or mimic the natural materials.

The ability of any one additive method to print a pore system depends not only on the scale of the instrument (smaller orifices for example, can make smaller parts), but also specific machine settings (like extrusion temperature and travel speed) and the type of material being printed (plastic is most common, but metals and minerals are becoming more so). Typically, the higher the resolution, the smaller the model that can ultimately be 3D printed.

Solutions to some of these limitations are being actively developed. For example, the foundry industry is eager to be able to 3D print intricate models out of silica for casting into metal.