3D Printed Rocks - An Emerging Technology for Systematic Petrophysical Studies

Abstract

3D printing translates digital models into physical objects, which could potentially be used to print proxies of reservoir rocks from their high-resolution images acquired by such as micro-CT tomography. This paper reviews current 3D printing technologies and explores the capabilities of 3D stereolithography (SLA) technique in rock printing in terms of scale, resolution, accuracy, and repeatability, with the eventual objective of studying factors affecting petrophysical models, such as Archie model, by varying petrophysical inputs of Archie parameters m and n, systematically. A 3D printer with the resolution of 10 μm is used to print rock models. Two types of digital models are designed for the 3D printing: Model I contains straight cylindrical pores; 19 pores with diameters from 10 to 100 μm with an increment of 5 μm, and Model II is a virtual core of 1 inch diameter and 2 inch length, created from a computer-generated random uniform sphere pack with a porosity of 30%. Model I cylindrical pores of down to 10 μm are printed and clearly observed on their micro-CT images. Pore connectivity is well preserved in the print proxy. However, the printed pore shapes are not completely circular as designed, indicating a challenge of shape preserving in printing. Pore sizes vary along the axis with a standard deviation of approximately 2-3 μm. In Model II virtual core printing, high printing accuracy and repeatability are achieved, while issues of converting from the digital design model to printer recognized STL model are discovered and being resolved. With continuous advancements in high resolution imaging, digitalization, and computing power, 3D printing could become a unique and innovative approach enabling manufacturing multiple rock samples for repeatable experiments with identical samples, experiments with systematic variables of such as pore structure or wettability. Challenges faced for printing full-scale pore-structure driven samples can leverage future development and applications of the evolving 3D printing technology.