| dc.description.abstract | Multi-stage hydraulic fracturing has become common practice for economically enhancing production from unconventional oil and gas reservoirs in recent years. The process of hydraulic fracturing is continuously refined as we discover new techniques through field studies and laboratory investigations. However, in modern well stimulation research, it is often difficult or impossible to obtain core samples with consistent properties for experimental studies. In these cases, isolating & evaluating stimulation design parameters with differing samples can be problematic, as large variations in rock properties can lead to inconsistent or incorrect conclusions. Therefore, the ability to reliably procure core samples with the identical characteristics would serve to benefit the confidence in the results of laboratory investigations.
The aim of this work is to design a framework for utilizing 3D printing technology to consistently generate detailed artificial samples suitable for use in experimental laboratory research. Many readily available modern 3D printers can produce samples with up to 20-75 micrometers of accuracy. Stereolithographic (SLA) resin 3D printers accomplish this by using an ultraviolet light source to selectively illuminate and cure a photopolymer onto a travelling build platform, building a physical model in a layer-by-layer fashion. Recent developments in this technology also allow SLA 3D printers to generate large-volume samples without sacrificing speed and resolution.
For this study, two areas of well stimulation research were chosen to demonstrate the successful implementation of the presented workflow. In the first part of this work, we created a realistic, rough-walled fracture system with 3D printed surfaces that mimic those of actual fractured rock for use in proppant transport experiments. While the rough topography of fracture walls likely influences the proppant transport process in the reservoir, nearly all historical laboratory flow studies of proppant transport have used parallel smooth surfaces to represent these fracture walls. The transparent, rough-walled fracture system created in this study allowed for the direct observation of proppant behavior as slurries were pumped. With transparent 3D printed samples that more accurately represent the surfaces of actual rock, we can elevate our understanding of the behavior of proppants, fluids, and additives in hydraulic fractures.
In the second focus of this study, casts of 3D printed samples with simulated rough fracture surfaces were used to create artificial cement replicas suitable for conductivity experiments. Core samples, even when originating from the same source, still can possess a large variability in surface topography due to the inherent irregular nature of fractures. To address this, 3D printed conductivity samples were used as a mold for producing cement samples to serve as an alternative for core. In this investigation, we found that these cement replicas were able to retain the desired surface geometry and resolution while maintaining the required compressive strength to withstand the closure stresses required for conductivity testing.
This work presents the detailed workflow for generating 3D printed samples and demonstrates the successful implementation of this workflow in the types of experimental studies mentioned above, aiming to serve as the foundation for the continued use throughout future investigations. | |
